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New Spectrophotometric Equations for Determining Chlorophylls a, b, c1, and c2 in Higher Plants, Algae and Natural Phytoplankton
... The endosymbionts of corals, soft corals and molluscs are usually assumed to be made up entirely of endosymbiont dinoflagellates (zooxanthellae) containing chlorophylls a + c 2 (Jeffrey et al. 1975;Morden & Sherwood 2002;Schubert et al. 2017;Ritchie et al. 2022). However, non-dinoflagellate algal symbionts are common in marine and freshwater organisms such as sponges, platyhelminths, coelenterates and urochordates. ...
... Chlorophyll extracts from the soft coral were made with a cork borer (diameter 11.3 mm) of the animal and ground in sand with 90% acetone as the extractant, as previously described (Jeffrey & Humphrey 1975;Ritchie et al. 2022). The best common extractant for both the soft coral, zooxanthella cell suspensions and the isolated green alga was a 1:1 mixture of acetone and DMSO (Porra 2011;Ritchie et al. 2021Ritchie et al. , 2022. ...
... Frigaard et al. (1996) was used as the source of standard reference spectra. The equations for 90% acetone in water were used as the benchmark for chlorophyll assays (Jeffrey & Humphrey 1975;Jeffrey & Welschmeyer 1997;Ritchie 2006). Routine scans from 600 to 850 nm were used (Ritchie et al. 2022) using 850 nm, not 750 nm, as the zero blank. ...
ABSTRACT
An undescribed variety of the green alga Chlorella cf. vulgaris was found living in the octocoral (soft coral) Sarcophyton sp., which also has dinoflagellate zooxanthellae. The green alga is present in very small numbers and is capable of photoheterotrophy based on growth in the presence of an inhibitor of photosynthesis, DCMU, with glycerol provided as a carbon source. The presence of zoochlorellae (Chl a + b), in soft corals appears to have been unsuspected. The easily cultured green alga was unicellular,
unflagellated and very small, c. 2 to 6 μm in diameter and had a relatively high Chl b content (Chl b/a = 0.379 ± 0.063). Rapid light curves using PAM fluorometry on the cultured cells showed that Yield vs. irradiance had a low maximum yield (Ymax, 0.388 ± 0.0132; Irradiance ½ point, E½Ymax = 139 ± 11.1 μmol
photon m–2 s–1). The overall optimum irradiance (Eopt) for the alga was 314 ± 18.8 μmol photon m–2 s–1. The alga can photosynthesize at 50% or more of the optimum rate from 70 to 900 μmol photon m–2 s–1 but would be severely inhibited under full sunlight. Most naturally occurring low irradiance habitats may
have a low median irradiance but are exposed intermittently to very high irradiances and so a relatively high Eopt is advantageous in minimizing photochemical damage. Like the green algal symbiont Elliptochloris marina of sea anemones, Chlorella cf. vulgaris is not exclusively marine: it grows better in
freshwater medium where it has different photosynthetic characteristics (higher Ymax, Eopt and ETRmax). Chlorella cf. vulgaris appears to be capable of photoheterotrophy and it is not clear if it is a symbiont, a commensal or a parasite.
... Chl a concentration and phytoplankton biomass were measured from an integrated water sample-depending on the sampling depth from 0.5 m and then after every metre to 1 m from the bottom, pooled together, and sampled (according to EVS-EN 16698 (2015a)). Samples for Chl a were filtered through GF/F filters, kept in -16˚C until analyses (within a week), extracted up to 24 h with 96% ethanol, measured spectrophotometrically (Hitachi U-3010) and calculated according to Jeffrey & Humphrey (1975). Utermöhl (1958) method and inverted light microscopes Nikon Eclipse and Olympos CK 40 were used to count phytoplankton cells. ...
Cyanobacterial blooms are widespread phenomena, expected to increase in frequency, magnitude, and duration due to a changing climate and increasing temperatures. We looked at remote sensing (optical, microwave, thermal) possibilities to enhance our understanding of bloom dynamics and its parameters, retrievable from satellite data in the shallow, eutrophic, transboundary lake Peipsi. Sentinel-3/OLCI (Ocean_and_Land_Colour_Instrument) and ENVISAT/MERIS (Medium_Resolution_Imaging_Spectrometer) data were used for Chlorophyll a (Chl a) detection, from which bloom parameters were retrieved. Pixels were categorized as “bloom” when Chl a concentration exceeded the long-term average by at least 5%. Maximal bloom coverage was about 100% in all parts of the lake, but on average, the blooms covered 96.5% of Lämmijärv, 85.0% of Peipsi sensu stricto (s.s.), and 84.5% of Lake Pihkva. On average, the blooms lasted 101 days in Peipsi s.s., 78 days in Lämmijärv, and 69 days in Lake Pihkva. Higher water levels resulted in significantly shorter blooms in Lämmijärv and Lake Pihkva. Traditional microscopy gave an overview of the main bloom-formers and their changes over a 20-years period. The importance of Gloeotrichia echinulata P.G.Richter has decreased in the last 10 years in Peipsi s.s and the importance of Aphanizomenon has increased in the entire lake.
... These filters were frozen at -40 °C and later analyzed spectrophotometrically after 90% acetone Chl-a extraction in complete darkness at 4 °C (Venrick & Hayward, 1984). Chl-a was calculated using the equations of Jeffrey & Humphrey (1975). An estimated detection limit of chlorophyll concentrations to be reported of 0.2 mg/m 3 was established using a high-performance spectrophotometer with a 10 -4 resolution Milton Roy Spectronic 1201 & 1001 plus. ...
Although autotrophic picophytoplankton (APP) is a sensitive component of phytoplankton responding to climate variability, little has been investigated in relatively undisturbed marine systems. This study aimed to assess the monthly dynamics of APP abundances from March 2009 to December 2010 and their association with regional climate variability at the Alfonso Basin station (Gulf of California). APP, the most abundant autotrophic component in the 0–100-m layer, and chlorophyll-a concentration (Chl-a) showed interannual variations associated with climate variability. APP abundance was positively correlated with temperature, salinity, and Chl-a, and significant negative correlations were established between nitrites + nitrates and phosphates. From July 2009 to April 2010, APP-integrated abundance explains at least 48% of the net primary productivity variation, suggesting a positive response to a prolonged influence of surface tropical water mass. According to the depth-integrated (0–100 m) abundance, APP variation was associated with the temporal evolution of Central Pacific El Niño 2009–2010 and multiannual warming that explains the positive trends in satellite sea surface temperature and stratification, and lower nutrient concentrations and N:P ratios values in the upper pycnocline layer at Alfonso Basin. These results highlight the importance of maintaining regional marine observatories.
... Surface water samples for measuring dissolved oxygen (DO) and chlorophyll a (Chla) concentrations were obtained with a 5-L Niskin bottle. DO was measured according to the Winkler procedure (Strickland and Parsons 1972), and chlorophyll a was measured according to Jeffrey and Humphrey (1975), using a PerkinElmer Lambda 2 spectrophotometer (Shelton, CT, USA). Prior to each tow to minimize accidental inclusion of dead organisms from previous stations, the net was thoroughly rinsed. ...
During 2015, monthly zooplankton sampling and measurements of surface temperature (SST), salinity, dissolved oxygen and chlorophyll a were conducted. Collections were made during neap tides at four locations between the inner and near the mouth of Magdalena Bay, Mexico. Thirty-three taxonomic groups were identified, and the most abundant taxa were copepods, diplostracans, decapods, ichthyoplankton (fish eggs), and chaetognaths. Zooplankton abundance did not vary significantly over time but did vary between sampling stations. SST and salinity were significantly correlated with the spatial distribution of organisms. Differences were found between the mortality percentages for the sampling stations and also for the taxonomic groups analyzed (Copepods 18%; Decapods 32%; Chaetognaths 33%), which implies the importance of carrying out mortality determination analyses in ecological studies of zooplankton.
... The extracts in the cuvettes were acidified with 30 µl of 1N HCl, and the absorbance at 665 nm (D665a) was measured (Lorenzen, 1967;Hendry et al., 1987;Zapata, 1988). The concentrations of chlorophyll a and b were estimated from the absorbance data using the equations of Jeffrey & Humphrey (1975), and the pheophytin a concentrations with the equation of Baird et al. (2017). The ratio Chla/Chlb was estimated from the concentration values. ...
Aquatic bryophytes are frequently used as bioindicators of water quality in rivers. Poor water quality increases physiological stress in moss, and stress levels can be estimated by measuring the concentrations of photosynthetic pigments and by calculating pigmentary indices. However, studies collecting many samples in a short time may need to store them until analysis. In the meantime, the pigments may suffer some degradation. Given the lack of studies on this problem for aquatic bryophytes, this one investigates the effect of three storage methods (refrigerated at 6 °C, frozen at − 20 °C and dried at room temperature) on the concentrations of chlorophyll a, chlorophyll b, pheophytin a and the following ratios: chlorophyll a/chlorophyll b, D430/D410, D665/D665a, D430/D665 and D480/D665 (where Dx is the absorbance at x nm) in the aquatic moss Fontinalis antipyretica. The results showed that refrigeration was the most suitable method, freezing might be suitable for some parameters, and drying was inadequate for this purpose. We recommend that all studies on photosynthetic pigments detail the time elapsed from collection to sample analysis, as well as the storage method used.
... The eluted peak was collected and concentrated by an ultrafiltration centrifuge tube (molecular weight cut-off: 100 kDa AMICON, Merck Millipore) to a concentration of 10 mg Chl ml −1 and stored in liquid nitrogen. The concentration of Chl a/c was determined according to Jeffrey et al. 41 . ...
Cryptophyte algae are an evolutionarily distinct and ecologically important group of photosynthetic unicellular eukaryotes. Photosystem II (PSII) of cryptophyte algae associates with alloxanthin chlorophyll a/c-binding proteins (ACPs) to act as the peripheral light-harvesting system, whose supramolecular organization is unknown. Here, we purify the PSII-ACPII supercomplex from a cryptophyte alga Chroomonas placoidea (C. placoidea), and analyze its structure at a resolution of 2.47 Å using cryo-electron microscopy. This structure reveals a dimeric organization of PSII-ACPII containing two PSII core monomers flanked by six symmetrically arranged ACPII subunits. The PSII core is conserved whereas the organization of ACPII subunits exhibits a distinct pattern, different from those observed so far in PSII of other algae and higher plants. Furthermore, we find a Chl a-binding antenna subunit, CCPII-S, which mediates interaction of ACPII with the PSII core. These results provide a structural basis for the assembly of antennas within the supercomplex and possible excitation energy transfer pathways in cryptophyte algal PSII, shedding light on the diversity of supramolecular organization of photosynthetic machinery.
... The PE and PC contents were calculated using the formula of Beer and Eshel (1985). Chl. a was extracted in 90% acetone from the tissue pellets after centrifugation for phycobilin, and Chl. a content was determined spectroscopically using the formula of Jeffrey and Humphrey (1975). ...
To elucidate whether Neoporphyra kitoi strain OHN-1 has superior characteristics as a new marine crop in the nori farm setting, we compared OHN-1 and Neopyropia yezoensis f. narawaensis strain U-51 cultivated under identical conditions during the early nori season. We assessed the growth and the contents of photosynthetic pigments and free amino acids (FAAs), which affect the quality and taste of nori, between OHN-1 and U-51. The blade length of OHN-1 was found to be significantly longer than that of U-51, and OHN-1 exhibited high-yield characteristics. Notably, the blade thickness of OHN-1 was only slightly greater than that of U-51, despite the significant differences between the two strains. The contents of pigments and FAAs related to the taste were also higher in OHN-1 than in U-51. These results obtained with a N. kitoi cultivar demonstrated that N. kitoi has superior growth and quality characteristics in the nori farm setting. Thus, we concluded that N. kitoi could be used as a new marine crop for nori cultivation.
... Samples from each station (3 L) and microcosm (3 L on June 17th, 1 L the following days; samples taken every day at noon) were filtered onto Whatman GF/F filters (25 mm in diameter), and frozen at − 20 • C until analysed. At the laboratory, the photosynthetic pigments were extracted in absolute methanol in darkness at 4 • C for 24 h (Jeffrey and Humphrey, 1975) and measured using a fluorometer (Perkin Elmer, model LS 55). A Chl a standard (Chl a from spinach, Sigma-Aldrich) was used to transform the fluorescence data into Chl a concentration. ...
... where D is the maximum depth of secchi disk visibility in meter (Raymont 1980). For pigment analysis, one litre of surface water was collected from each of the sampling stations for determination of the chlorophyll pigment (Chl a, b and c) by spectrophotometric method after extraction with 90% acetone (Jeffrey and Humphrey 1975). ...
The biochemical composition of red seaweeds, Catenella repens was investigated in this present study along with subsequent analysis of relevant physico-chemical variables. In this study, the relationship between the nutritive components of this species and the ambient environmental parameters was established. Protein content varied from 2.78 ± 0.30% of dry weight (stn.3) to 16.03 ± 0.96% of dry weight (stn.1) with highest values during monsoon. The protein levels were positively correlated with dissolved nitrate content and negatively correlated with water temperature (except stn.3) and salinity. Carbohydrate content of this species varied significantly (p < 0.05) during pre-monsoon between stations and the values showed positive relationship with salinity and surface water temperature. In contrast to carbohydrate , lipid concentration was lowest in values and varied very slightly between seasons and stations. Astaxanthin content of the seaweed species was greater in pre-monsoon than monsoon and post-monsoon in all the selected stations. Compared with the three seasons, samples of red seaweed collected in pre-monsoon has high carbohydrate-astaxanthin in contrast to protein-lipid which showed high values during monsoon. Statistical analysis computed among the environmental and biochemical parameters suggests the potential role played by the abiotic parameters on biosynthetic pathways of seaweed. This paper also highlights the influence of the nutritional quality of water that can be used for mass cultivation of Catenella repens.
... The algae were deposited onto membrane filters with a pore diameter of 3-5 μm, which were dried in the dark at room temperature and stored in the refrigerator until analysis. The chlorophyll concentration was calculated using the equation from (Jeffrey and Humphrey, 1975). ...
... Other subsamples were mixed with CO 2 -free deionised waters at a volume ratio of 1:2.5, from which pH and salinity were measured using a pH meter (Mettler Toledo) and a salinity meter (Vastocean), respectively. Chlorophyll a (Chl-a) was extracted with acetone and determined using a spectrophotometer (Shimadzu UV-2550, Kyoto, Japan) according to Jeffrey and Humphrey (1975). Total organic carbon (TOC) and total nitrogen (TN) were measured using a thermal combustion furnace analyser (Elementar analyzer vario El cube, Frankfurt, Germany). ...
Microbial communities are commonly characterised through the metabarcoding of environmental DNA. This DNA originates from both viable (including dormant and active) and dead organisms, leading to recent efforts to distinguish between these states. In this study, we further these approaches by distinguishing not only between viable and dead cells but also between dormant and actively growing cells. This is achieved by sequencing both rRNA and rDNA, in conjunction with propidium monoazide-treated rDNA, to partition the active, dormant and relic fractions in environmental samples. We apply this method to characterise the diversity and assemblage structure of these fractions of microeukaryotes in intertidal sediments during a wet-dry-rewet incubation cycle. Our findings indicate that a significant proportion of microeukaryotic phylotypes detected in the total rDNA pools originate from dormant and relic microeukaryotes in the sediments,both in terms of richness (dormant, 13 ± 2%; relic, 47 ± 5%) and read abundance (dormant, 20 ± 7%; relic, 14 ± 5%). The richness and sequence proportion of dormant microeukaryotes notably increase during the transition from wet to dry conditions. Statistical analyses suggest that the dynamics of diversity and assemblage structure across different activity fractions are influenced by various environmental drivers. Our strategy offers a versatile approach that can be adapted to characterise other microbes in a wide range of environments.
... For Chl a analysis after 96 h, samples were filtered in cellulose ester membranes (0.45 μm of pore size, Millipore) and were extracted with dimethyl sulfoxide (DMSO) (Shoaf and Lium, 1976), and then run in a HACH DR500 spectrophotometer (HACH Company, Loveland, CO, USA) at 664 and 630 nm. The Chl a content was calculated according to Jeffrey and Humphrey (1975). To quantify the carbohydrates after 96 h, samples were centrifuged (4400 rpm, 10 min), extracted by phenol-sulphuric reaction (Liu et al., 1973), and then run in a spectrophotometer at 485 nm. ...
Nanoparticles have applications in many sectors in the society. ZnWO4 nanoparticles (ZnWO4-NPs) have potential in the fabrication of sensors, lasers, and batteries, and in environmental remediation. Thus, these NPs may reach aquatic ecosystems. However, we still do not know their effects on aquatic biota and, to our knowledge, this is the first study that evaluates the toxicity of ZnWO4-NPs in a eukaryotic organism. We evaluated the toxicity of ZnWO4-NPs on the green microalga Raphidocelis subcapitata for 96 h, in terms of growth, cell parameters, photosynthesis, and biochemical analysis. Results show that most of Zn was presented in its particulate form, with low amounts of Zn2+, resulting in toxicity at higher levels. The growth was affected from 8.4 mg L−1, with 96h–IC–50 of 23.34 mg L−1. The chlorophyll a (Chl a) content increased at 30.2 mg L−1, while the fluorescence of Chl a (FL3-H) decreased at 15.2 mg L−1. We observed increased ROS levels at 44.4 mg L−1. Regarding photosynthesis, the NPs affected the oxygen evolving complex (OEC) and the efficiency of the photosystem II at 22.9 mg L−1. At 44.4 mg L−1 the qP decreased, indicating closure of reaction centers, probably affecting carbon assimilation, which explains the decay of carbohydrates. There was a decrease of qN (non-regulated energy dissipation, not used in photosynthesis), NPQ (regulated energy dissipation) and Y(NPQ) (regulated energy dissipation via heat), indicating damage to the photoprotection system; and an increase in Y(NO), which is the non-regulated energy dissipation via heat and fluorescence. Therefore, to protect aquatic ecosystems, it is extremely important to study the toxicity of emerging contaminants on microalgae, as they are at the base of aquatic food chains, and impacts on these primary producers can affect entire ecosystems. Our study shows that ZnWO4-NPs affect the growth and physiological and biochemical parameters of the chlorophycean R. subcapitata.
... Para los nutrientes se ha seguido la metodología descrita por Grasshoff et al., (1999) [7]. Las clorofilas se han determinado mediante espectrofotometría siguiendo un protocolo estandarizado [8] y aplicando las ecuaciones tricromáticas de Jeffrey y Humprey [9] y sus respectivas correcciones para feopigmentos. Las muestras de fitoplancton fueron fijadas con una solución al 20% de formaldehído tamponado con hexametilentetramina [10] y la concentración de las muestras se llevó a cabo mediante cámaras de sedimentación durante 48 horas. ...
... Laminarin chiết từ loài rong Laminaria digitata được sử dụng làm chất chuẩn. + Định lượng chlorophyll: hàm lượng chlorophyll được định lượng theo phương pháp Jeffrey và Humphrey (1975) [11]. + Phương pháp đánh giá hoạt tính -Hoạt tính chống oxy hóa tổng: được xác định theo phương pháp của Prieto và cộng sự, (1999): lấy 100 µl mẫu bổ sung 900µl nước cất và thêm 3 ml dung dịch A (H2SO4 0,6 M, sodium phosphate 28 mM and ammonium Molybdate 4 mM). ...
Bài báo này tập trung vào việc nghiên cứu ảnh hưởng của nhiệt độ và thời gian chần tới hàm lượng fucoidan, laminarin, alginate, chlorophyll và hoạt tính sinh học của dịch chiết từ rong mơ Sargassum polycystum. Loài rong này được thu mẫu vào tháng 12/2016 và 4/2017 ở vùng biển Ninh Thuận. Các hoạt tính sinh học được đánh giá là hoạt tính chống oxy hóa tổng, hoạt tính khử sắt, hoạt tính bắt gốc tự do DPPH và hoạt tính ức chế enzyme lipoxygenase. Nhiệt độ chần được nghiên cứu trong dải từ 80ºC - 100ºC với bước nhảy là 10ºC, thời gian chần từ 5 giây - 20 giây với bước nhảy 5 giây. Kết quả cho thấy, nhiệt độ và thời gian chần ảnh hưởng mạnh lên hàm lượng các chất sinh học và hoạt tính của dịch chiết thu nhận từ rong mơ Sargassum polycystum. Khi chần ở 100ºC trong 15 giây, hàm lượng các chất sinh học và hoạt tính thu được cao nhất. Hàm lượng chlorophyll thu được cao nhất ở nhiệt độ chần 100ºC và thời gian chần 10 giây. Hàm lượng các chất sinh học và hoạt tính biến đổi theo mô hình tuyến tính bậc một với xu hướng tăng theo thời gian và nhiệt độ chần. Từ khóa: hoạt tính sinh học, chlorophyll, fucoidan, Sargassum polycystum, chần
... The contents of the microalga pigments, including chlorophyll a (Chl a) and chlorophyll c (Chl c), were determined according to the procedure specified by Jeffrey and Humphrey (1975). Briefly, 5 mL acetone (90%) was added to 0.01 g of the collected cells from each test culture, and the suspension was vortexed vigorously for 2 min and then incubated in the dark at 4 °C for 24 h. ...
Toxicological effects of silver nanoparticles (SNPs) in different organisms have been studied; however, interactions of SNPs with other environmental pollutants such as mercury are poorly understood. Herein, bioassay tests were performed according to ΟECD 201 guideline to assess the toxic effects induced by mercury ions (mercury chloride, MCl) on the marine microalga Chaetoceros muelleri in the presence of SNPs or silver ions (silver nitrate, SN). Acute toxicity tests displayed that the presence of SNPs or SN (0.01 mg L⁻¹) significantly reduced the toxicity of MCl (0.001, 0.01, 0.1, 1, 10, and 100 mg L⁻¹) and increased the IC50 of MCl from 0.072 ± 0.014 to 0.381 ± 0.029 and 0.676 ± 0.034 mg L⁻¹, respectively. In the presence of SN or SNPs, the mercury-reducing effect on algal population growth significantly decreased. Considering the increase of IC50, the mercury toxicity decreased approximately 5.44 and 9.66 times in the presence of SNPs or SN, respectively. The chlorophyll a and c contents decreased at all exposures; however, the decrease by MCl-SNPs and MCl-SN was significantly less than MCl except at 1 mg L⁻¹. The lowering effect of MCl-SN on chlorophyll contents was less than MCl and MCl-SNPs. MCl exposure induced significant raises in total protein content (TPC) at concentrations < 0.01mg L⁻¹, with a maximum of ~ 70.83% attained at 100 mg L⁻¹. The effects of MCl-SNPs and MCl-SN on TPC were significantly less than MCl. Total lipid content (TLC) at all MCl concentrations was higher than the control, while at coexposure to MCl-SN, TLC did not change until 0.01 mg L⁻¹ compared with the control. The effects of MCl-SN and MCL-SNPs on TPC and TLC were in line with toxicity results, and were significantly less than those of MCl individually, confirming their antagonistic effects on MCl. The morphological changes of algal cells and mercury content of the cell wall at MCl-SN and MCl-SNPs were mitigated compared with MCl exposure. These findings highlight the mitigatory impacts of silver species on mercury toxicity, emphasizing the need for better realizing the mixture toxicity effects of pollutants in the water ecosystem.
Graphical Abstract
... The absorbance measurements were recorded by a UV-vis spectrophotometer (Hach Lange, DR 2800, Loveland, CO, USA) at 750, 665, 662, 645, 630, and 470 nm. The concentrations of the carotenoids and Chl-a were calculated according to Jeffrey and Humphrey [40] and Lichtenthaler and Wellburn [41]. DNA was extracted from biofilm samples using Qiagen DNeasy PowerBiofilm Kit (Hilden, Germany) following the manufacturer's instructions. ...
Algal biofilms play an essential role in ecosystem functioning, but their physiological and biochemical changes during salt stress remain poorly understood. This study aimed at investigating how biofilm communities react to different salinity in a microcosm experiment and to offer insights into the potential effects of future freshwater salinization. Biofilm samples collected from Iriri River (Drâa basin, Southern Morocco) were exposed to water gradually enriched with sodium chloride to obtain three final concentrations (1, 10, and 30 g/L) over 14 days, and the changes were compared with control. Several biofilm responses were analyzed throughout the experiment, including biofilm biomass, changes in community structure and composition via eDNA metabarcoding, physiological feedback, biochemical parameters, antioxidant activities, non-enzymatic salt stress markers, osmoprotection indicators, and nitrogen assimilation. High salt concentrations significantly altered biofilm communities' composition, structure, and function, leading to an overall decrease in alpha diversity and a decrease in diatom and cyanobacterial biomass, while green algae remained unchanged. Chlorophyll a content increased in biofilm exposed to low salt concentration (1 g/L) and decreased at high salt concentrations while carotenoid significantly increased even at high salinity (10 g/L). Biofilm also showed an increase in carbohydrates and a decrease in protein content under high salinities (10 and 30 g/L). In addition, salt stress-induced ROS generation in the biofilm, with an increase in H2O2 content, caused oxidative damage and lipid peroxidation with an increase in MDA levels. To prevent this damage, elevated proline content was recorded, and additionally, the biofilm exhibited antioxidant defense mechanisms by rising activity of ROS-scavenger enzymes such as SOD, CAT, and POD. Our experimental results highlighted the salinity effect on algal biofilm as well as physiological and biochemical responses. This study could help predict the consequences of freshwater salinization on river biofilms and its potential impact at the ecosystem level.
... As previously mentioned, the chlorophyll a (Chl-a) content solution were carried out using the acetone extraction technique (Jeffrey and Humphrey, 1975). In a nutshell, acetone was extracted using ultrasound (40 kHz, 30 min). ...
Cadmium is a persistent heavy metal commonly found in aquatic ecosystems and has a strong toxic effect on organisms. The sensitivity of phytoplankton to environmental changes and its role as an indicator of aquatic ecosystem health have been well-established. However, the mechanisms by which phytoplankton respond to cadmium remain incompletely understood. In this study, we chose the typical planktonic diatom Cyclotella meneghiniana Kützing, by integrating physiological-biochemical data and transcriptome analysis, to reveal the molecular mechanisms of C. meneghiniana responing to cadmium. Under cadmium stress, the cell density and chlorophyll-a content of C. meneghiniana significantly decreased, while MDA content and SOD activity gradually increased. At 72 h of cadmium stress, we found that at this time point, cell abundance and physiological variation were very significant, therefore we selected 72 h for subsequent analysis. To better understand the cadmium stress response mechanisms of C. meneghiniana, a de novo transcriptome method was used to analyse C. meneghiniana under cadmium stress for 72 h, and 1704 (M vs. CK) and 4788 (H vs. CK) differentially expressed genes were found. Our results showed that the changes in gene expression were closely correlated to the physiological-biochemical changes. Although cadmium stress could promote the nitrogen metabolism pathway, ROS scavenging system, and photosynthesis. While, C. meneghiniana under medium and high concentrations of cadmium can also limit various intracellular metabolic pathways, such as the MAPK pathway and phosphati-dylinositol metabolic pathway, and the degree of inhibition increases with the increase of stress concentration. In present study, the complete molecular mechanism of the planktonic diatom response to cadmium has been established, which provided important information for further studies on heavy metal pollutants and the multiple functional genes responsible for cadmium sensitivity and tolerance in planktonic diatoms.
... Hitachinaka, Japan). Chl-a values were calculated for mixed phytoplankton assemblage according to Jeffrey and Humphrey (1975). ...
Dissolved organic matter (DOM) plays an important role in biogeochemistry of lake ecosystems. Studies measuring DOM at short intervals in lakes are still rare, thus its short-term dynamics are largely unknown. We investigated DOM temporal variation in large and shallow eutrophic Lake Võrtsjärv (Estonia) during one growing season (May–September 2016) using field-deployable spectrometer In Situ Spectral Analyzer (GO Systemelektronik GmbH) to measure absorbance spectra (wavelength range 200–708 nm) at a 2-hour interval coupled with monthly discrete water sampling. Collected spectra were analyzed together with some in-lake variables, lake metabolic rates, and meteorological and hydrological data using Boosted Regression Tree (BRT) and Random Forest (RF) models. Different spectral parameters were used to assess total and allochthonous DOM quantity, and relative share of autochthonous DOM. All parameters, i.e., DOM quantity and quality, varied on a large scale. For example, dissolved organic carbon (DOC) concentrations ranged from 12.0 to 17.3 mg L-1. High levels of DOM were mainly of allochthonous origin; strong relationship with inflow indicated the same. Relative share of autochthonous DOM increased with rising air temperature as primary production rose in warm water; however, we did not find any direct relationships with gross primary production. RF and BRT models explained up to 38% and 63% of DOM temporal variability, respectively. Our results showed that monthly water samples did not capture large variation in DOM. Therefore, high-frequency measurements using in situ spectrometer improve temporal representativeness of DOM monitoring in lakes compared to traditional sampling methods.
... from the corresponding stream. The suspension was distributed in aliquots to analyse chlorophyll-a (chl-a; Jeffrey and Humphrey, 1975) and then stored at − 20 • C for further analysis. Additionally, at days 0, 7, 14, 21 of the exposure period and days 7 and 14 of the recovery period, we preserved 5 mL of the biofilm suspension by using 5 mL Ethanol 70% to determine the diatom growth rate. ...
https://www.sciencedirect.com/science/article/pii/S0166445X24000146?via%3Dihub#sec0001
... Chlorophyll-a and -b contents were determined by measuring the extractant at an absorbance of 664 nm and 647 nm, respectively, using a spectrophotometer (Jenway 6300 Spectrophotometer) (Harmut 1987;Wang et al. 2020). The chlorophyll concentrations were calculated following equations by Jeffrey and Humphrey (1975) (chlorophyll-a: 11.93 × λ 664nm − 1.93 × λ 647nm and chlorophyll-b: 20.36 × λ 647nm − 5.50 × λ 664nm ). ...
Plastic is an essential component of agriculture globally, becoming a concerning form of pollution. Biodegradable alternatives are gaining attention as a potential replacement for commonly used, non-degradable plastics, but there is little known about the impacts of biodegradable plastics as they age and potential leachates are released. In this study, different types (conventional: polyethylene and polypropylene and biodegradable: polyhydroxybutyrate and polylactic acid) of micro- and meso-films were added to soil at 0.1% (w/w) prior to being planted with Lolium perenne (perennial ryegrass) to evaluate the plant and soil biophysical responses in a pot experiment. Root and shoot biomass and chlorophyll content were reduced when soil was exposed to plastics, whether conventional or biodegradable, pristine, aged or when just their leachate was present. The pH and organic matter content of soil exposed to these plastics and their leachates was significantly reduced compared to control samples; furthermore, there was an increase in CO2 respiration rate from soil. In general, meso (> 5 mm) and micro (< 5 mm) plastic films did not differ in the impact on plants or soil. This study provides evidence that conventional and biodegradable plastics have both physical and chemical impacts on essential soil characteristics and the growth of L. perenne, potentially leading to wider effects on soil carbon cycling.
Graphical abstract
... To quantify chlorophyll-a 300-2000 mL of sample water was filtered through pre-combusted GF/C filters (Whatman). Chlorophyll-a was extracted in cold acetone (90%) and the absorption was measured using a spectrophotometer [29,30]. Total P was digested with persulfate according to [31] and analysed complying with Ö NORM EN ISO 15681-2. ...
Information is scarce on how environmental and dispersal processes interact with biological features of the organisms, such as their habitat affinity, to influence patterns in biodiversity. We examined the role of habitat specialist vs. generalist species, and the spatial configuration, connectivity, and different environmental characteristics of river-floodplain habitats to get a more mechanistic understanding of alpha and beta diversity of fish metacommunities. We used environmental DNA metabarcoding to characterize species (taxa) richness and composition in two separate floodplains of the river Danube (Austria and Hungary) during two different hydrological conditions. Results showed that differences in the number of generalist and specialist species and their responses to connectivity and environmental gradients influenced patterns in alpha and beta diversity. Of the components of beta diversity, richness difference (nestedness) showed consistently higher values than replacement (turnover), mainly due to the decrease of specialist species along the connectivity gradient (i.e., from the mainstem to the most isolated oxbows). Variance in both alpha and beta diversity could be well predicted by a set of local and regional variables, despite high environmental variability, which characterizes river-floodplain ecosystems. Of these, the joint or shared variance fractions proved to be the most important, which indicates that the effects of local and regional processes cannot be unambiguously separated in these river-floodplain systems. Local scale environmental variables were more important determinants of both alpha and beta diversity in the low water period than in the high water period. These results indicate the differential role of local and regional processes in community organization during different hydrological conditions. Maintenance of both local and regional scale processes are thus important in the preservation of alpha and beta diversity of floodplain fish metacommunities, which should be considered by environmental management.
... The chlorophyll a (Chla) content in corals was spectrophotometrically measured with a modular spectrometer (Flame-T-UV-VIS, Ocean Optics Inc.), using Jeffrey and Humphrey (1975) equations. Pigments were extracted using a mixture of acetone / dimethyl sulfoxide (95:5 vol / vol) (Iglesias-Prieto and Trench, 1994), from samples of coral tissue previously extracted with an air gun connected to a scuba tank and homogenized with a tissue homogenizer (Tissue-tearor, BioSpec Inc.). ...
El deterioro de las propiedades ópticas del agua, o aumento de turbidez, debido a perturbaciones antropogénicas es un fenómenogeneralizado en zonas costeras. Los efectos sobre el ambiente lumínico submarino y la fisiología de corales simbióticos, quedependen principalmente de la luz para sobrevivir y mantener elevada calcificación, han sido poco explorados. En este estudiose describen los efectos de la pluma del Canal del Dique sobre el ambiente lumínico, sobrevivencia y fisiología de corales en el arrecifeVaradero. Se realizó un trasplante recíproco con fragmentos de Orbicella faveolata entre una zona somera en Varadero (3.5 m) y un sitio contrastante con aguas más claras a mayor profundidad (12 m) con intensidad de luz comparable. La columna de agua en Varadero se encontró fuertemente estratificada, favoreciendo el aislamiento del arrecife de la pluma. Corales trasplantados a Varadero mostraron mayor sobrevivencia posiblemente debido a reducción de estrés lumínico y mayor heterotrofía. Su fisiología indicó aclimatación a poca luz y limitado potencial autotrófico, evidenciando un riesgo para la sobrevivencia de corales a mayor profundidad. Los resultados indican que un mayor deterioro de las propiedades ópticas del agua en la bahía de Cartagena por perturbaciones antropogénicas en la cuenca del río Magdalena y en la zona costera pone en riesgo la prevalencia del arrecife Varadero.
... The OD values at 664 nm, 647 nm, and 630 nm were used to calculate chlorophyll concentration, while the OD value of 750 nm was used as turbidity correction factor and subtracted from each of the pigments OD values before using them in the equations. The concentrations of chlorophyll a, was calculated using the corrected OD values in the following equations [6] : Where: C a = Chlorophyll-a concentration in mg/L, and OD66 4, OD6 47, and OD630 = corrected optical densities (with a 1 cm light path) at the respective wavelengths. Once the pigment concentrations in the extract were determined, the pigments' quantity per unit volume was com-puted using the following formula: ...
Cyanobacterial species such as Oscillatoria spp. pigments are essential components that enable the photosynthetic ability of this autotrophic organism. These pigments, principally chlorophylls and phycobiliproteins, are crucial for photosynthesis and give cyanobacteria their distinctive blue-green color. Exploring these pigments is crucial for unraveling the ecological and biotechnological relevance and significance. Spectrophotometric methods were used for measuring the chlorophyll-a, phycobiliprotein, and carotenoid contents of Oscillatoria species. Oscillatoria spp. displayed significantly variable (p ˂ 0.05) chlorophyll-a ranging from 12.67 ± 0.04 to 22.72 ± 0.04 µg/mL. Phycobiliprotein content (mg/g) significantly (p ˂ 0.05) varied from 87.39 ± 0.12 µg/mL to 121.42 ± 0.06. Carotenoid content also significantly ranged from 1.0 ± 0.01 µg/mL to 1.4 ± 0.01 µg/mL. Present data will contribute to the screening and characterization of Oscillatoria spp. in terms of pigment to utilize it in rigorous scientific research and diverse commercial applications.
... Endosymbiont cell densities were determined by microscopy using a hemocytometer and counting three replicate aliquots of the cell suspension per fragment. Endosymbiont photopigments were extracted in 100% acetone for 24 h and concentration of chlorophyll a was determined via absorbance at 630, 663, and 750 nm using the equation (Jeffrey & Humphrey, 1975): ...
Back‐to‐back marine heatwaves in 2016 and 2017 resulted in severe coral bleaching and mortality across the Great Barrier Reef (GBR). Encouragingly, some corals that survived these events exhibit increased bleaching resistance and may represent thermally tolerant populations that can better cope with ocean warming. Using the GBR as a natural laboratory, we investigated whether a history of minimal (Heron Island) or severe (Lizard Island) coral bleaching in 2016 and 2017 equates to stress tolerance in a successive heatwave (2020). We examined the genetic diversity, physiological performance, and trophic plasticity of juvenile (<10 cm) and adult (>25 cm) corals of two common genera ( Pocillopora and Stylophora ). Despite enduring greater cumulative heat stress (6.3°C week ⁻¹ vs. 5.6°C week ⁻¹ ), corals that experienced the third marine heatwave in 5 years (Lizard) exhibited twice as high survival and visual bleaching thresholds compared to corals that had not experienced significant bleaching in >10 years (Heron). Surprisingly, only one shared host–Symbiodiniaceae association was uncovered between locations ( Stylophora pistillata – Cladocopium “C8 group”) and there was no genetic overlap in Pocillopora – Cladocopium partnerships, suggesting turnover in species composition from recent marine heatwaves. Corals within the species complex Pocillopora that survived the 2016 and 2017 marine heatwaves at Lizard Island were the most resilient, exhibiting three times greater calcification rates than conspecifics at Heron Island. Further, surviving corals (Lizard) had distinct isotopic niches, lower host carbon, and greater host protein, while conspecifics that had not experienced recent bleaching (Heron) had two times greater symbiont carbon content, suggesting divergent trophic strategies that influenced survival (i.e., greater reliance on heterotrophy vs. symbiont autotrophy, respectively). Ultimately, while corals may experience less bleaching and survive repeated thermal stress events, species‐specific trade‐offs do occur, leaving open many questions related to the long‐term health and recovery of coral reef ecosystems in the face of intensifying marine heatwaves.
... where D is the maximum depth of secchi disk visibility in meter (Raymont 1980). For pigment analysis, one litre of surface water was collected from each of the sampling stations for determination of the chlorophyll pigment (Chl a, b and c) by spectrophotometric method after extraction with 90% acetone (Jeffrey and Humphrey 1975). ...
The biochemical composition of red seaweeds, Catenella repens was investigated in this present study along with subsequent analysis of relevant physico-chemical variables. In this study, the relationship between the nutritive components of this species and the ambient environmental parameters was established. Protein content varied from 2.78 ± 0.30% of dry weight (stn.3) to 16.03 ± 0.96% of dry weight (stn.1) with highest values during monsoon. The protein levels were positively correlated with dissolved nitrate content and negatively correlated with water temperature (except stn.3) and salinity. Carbohydrate content of this species varied significantly (p < 0.05) during pre-monsoon between stations and the values showed positive relationship with salinity and surface water temperature. In contrast to carbohydrate , lipid concentration was lowest in values and varied very slightly between seasons and stations. Astaxanthin content of the seaweed species was greater in pre-monsoon than monsoon and post-monsoon in all the selected stations. Compared with the three seasons, samples of red seaweed collected in pre-monsoon has high carbohydrate-astaxanthin in contrast to protein-lipid which showed high values during monsoon. Statistical analysis computed among the environmental and biochemical parameters suggests the potential role played by the abiotic parameters on biosynthetic pathways of seaweed. This paper also highlights the influence of the nutritional quality of water that can be used for mass cultivation of Catenella repens.
... The water was filtered in Millipore ® AP40 filters, and the filter was stored protected from the light, and frozen until analysis. The pigment was extracted from filters using 90% acetone, the extract was measured in a spectrophotometer, and pigment concentration was obtained according to Jeffrey and Humphrey (1975) equations. ...
This study quantified the seasonal and spatial variability of partial pressure of CO 2 ( p CO 2 ) and water‐atmosphere CO 2 fluxes in the Parnaíba River Delta, the largest delta in the Americas. It is a pristine equatorial, mangrove‐dominated environment located in a transitional between humid and semi‐arid climates, with marked seasonality in rainfall and river discharge. Major channels and bays were sampled during dry and wet seasons, with continuous measurements of p CO 2 , temperature, salinity, and wind velocity. Subsurface water samples were collected in discrete stations for pH, total alkalinity (TA), dissolved inorganic carbon (DIC), dissolved oxygen and chlorophyll a quantification. A significant positive correlation between carbonate system parameters with salinity was found in both periods, with salinity significantly higher in the dry season. Strong deviations of p CO 2 , TA, and DIC from two endmembers conservative mixing were found, particularly in mangrove‐dominated waters, due to organic matter degradation. The Delta showed high spatial variability of p CO 2 , with the highest values in mangrove‐dominated waters, moderate in the river‐dominated regions, and lowest in the high salinity areas, suggesting that p CO 2 variability is likely controlled by a combination of river‐ocean mixing and biological processes (respiration and photosynthesis). The Delta outgasses about 20 times less CO 2 in the dry season (9.06 ± 11.09 mmol m ⁻² .d ⁻¹ ) than in the rainy season (209.68 ± 250.87 mmol m ⁻² d ⁻¹ ). Our results indicate this large mangrove‐dominated tropical delta is an important source of CO 2 to the atmosphere, but a sharp decrease was observed during dry periods.
... The FCPs bands were cut out and subjected to mass spectrometry (MS) analysis as described previously 47 (Fig. 1c), whose results were searched against the 9 C. meneghiniana sequences obtained via transcriptome sequencing and the fcp01-12 sequences reported previously 32,48,49 . The Chl concentration was determined as previously reported 50 , which shows that the ratio of Chl a/c is as high as 100. Pigment compositions were analyzed by HPLC analysis as reported previously 51 , which identified the existence of Chl a, Chl c, Fx, Ddx, Dtx and BCR based on the corresponding absorption spectra and elution times (Fig. 1d). ...
Diatoms are dominant marine algae and contribute around a quarter of global primary productivity, the success of which is largely attributed to their photosynthetic capacity aided by specific fucoxanthin chlorophyll-binding proteins (FCPs) to enhance the blue-green light absorption under water. We purified a photosystem II (PSII)-FCPII supercomplex and a trimeric FCP from Cyclotella meneghiniana (Cm) and solved their structures by cryo-electron microscopy (cryo-EM). The structures reveal detailed organizations of monomeric, dimeric and trimeric FCP antennae, as well as distinct assemblies of Lhcx6_1 and dimeric FCPII-H in PSII core. Each Cm-PSII-FCPII monomer contains an Lhcx6_1, an FCP heterodimer and other three FCP monomers, which form an efficient pigment network for harvesting energy. More diadinoxanthins and diatoxanthins are found in FCPs, which may function to quench excess energy. The trimeric FCP contains more chlorophylls c and fucoxanthins. These diversified FCPs and PSII-FCPII provide a structural basis for efficient light energy harvesting, transfer, and dissipation in C. meneghiniana .
... Then 100 µl of methanol were added to the pellet and vortexed for 20 s followed by adding 900 µl of acetone and vortexing for 10 s. After centrifugation for 2 min at 16 000 g in a microcentrifuge 5424 (Eppendorf, Wesseling-Berzdorf, Germany), Chl a absorbance was determined spectrophotometrically using the Jeffrey and Humphrey formula (Jeffrey and Humphrey, 1975). Cultures were then adjusted to a Chl a content of 2 μg ml -1 , and non-photochemical quenching (NPQ) was measured using PAM Imaging (Heinz Walz GmbH, Effeltrich, Germany). ...
Aureochromes (AUREOs) are unique blue-light receptors and transcription factors found only in stramenopile algae. While each of the four AUREOs identified in the diatom Phaeodactylum tricornutum may have a specific function, PtAUREO1a has been shown to have a strong impact on overall gene regulation, when light changes from red to blue light conditions. Despite its significance, PtAUREO1a’s molecular mechanism is largely unexplored. To comprehend the overall process of gene regulation by PtAUREO1a, we conducted a series of in vitro and in vivo experiments, including pull-down assays, yeast one-hybrid experiments, and phenotypical characterization using recombinant PtAUREOs and diatom mutant lines expressing a modified PtAureo1a gene. We describe the distinct light absorption properties of four PtAUREOs and the formation of all combinations of their potential dimers. We demonstrate the capability of PtAUREO1a and 1b to activate the diatom-specific cyclin 2, PtAureo1a, and PtAureo1c genes under both light and dark conditions. Using mutant lines expressing a modified PtAUREO1a protein with a considerably reduced light absorption, we found novel evidence that PtAUREO1a regulates the expression of PtLHCF15, which is essential for red-light acclimation. Based on current knowledge, we present a working model of PtAUREO1a gene regulation properties.
... Surface water samples for measuring dissolved oxygen (DO) and chlorophyll a (Chla) concentrations were obtained with a 5 L Niskin bottle. DO was measured according to the Winkler procedure (Strickland and Parsons 1972), and chlorophyll a was measured according to Jeffrey and Humphrey (1975), using a PerkinElmer Lambda 2 spectrophotometer (Shelton, CT, USA). Prior to each tow to minimize accidental inclusion of dead organisms from previous stations, the net was thoroughly rinsed. ...
During 2015, monthly zooplankton sampling and measurements of surface temperature (SST), salinity, dissolved oxygen and chlorophyll a were conducted. Collections were made during neap tides at four locations between the inner and near the mouth of Magdalena Bay, Mexico. Thirty-three taxonomic groups were identified, and the most abundant taxa were copepods, diplostracans, decapods, ichthyoplankton (fish eggs) and chaetognaths. Zooplankton abundance did not vary significantly over time, but did vary between sampling stations. SST and salinity were significantly correlated with the spatial distribution of organisms. Differences were found between the mortality percentages for the sampling stations and also for the taxonomic groups analyzed (Copepods 18%; Decapods 32%; Chaetognaths 33%), which implies the importance of carrying out mortality determination analyses in ecological studies of zooplankton .
... Chlorophyll a was measured according to Jeffrey and Humprey [49] at the end of the experiment (day 21). Briefly, a pellet with known Symbiodiniaceae cell count was resuspended in 90% acetone, vortexed and left in darkness for 24 h at 4˚C. ...
Coral reefs may experience lower pH values as a result of ocean acidification (OA), which has negative consequences, particularly for calcifying organisms. Thus far, the effects of this global factor have been mainly investigated on hard corals, while the effects on soft corals remain relatively understudied. We therefore carried out a manipulative aquarium experiment for 21 days to study the response of the widespread pulsating soft coral Xenia umbellata to simulated OA conditions. We gradually decreased the pH from ambient (~8.3) to three consecutive 7-day long pH treatments of 8.0, 7.8, and 7.6, using a CO 2 dosing system. Monitored response variables included pulsation rate, specific growth rate, visual coloration, survival, Symbiodiniaceae cell densities and chlorophyll a content, photosynthesis and respiration, and finally stable isotopes of carbon (C) and nitrogen (N) as well as CN content. Pulsation decreased compared to controls with each consecutive lowering of the pH, i.e., 17% at pH 8.0, 26% at pH 7.8 and 32% at pH 7.6, accompanied by an initial decrease in growth rates of ~60% at pH 8.0, not decreasing further at lower pH. An 8.3 ‰ decrease of δ ¹³ C confirmed that OA exposed colonies had a higher uptake and availability of atmospheric CO 2 . Coral productivity, i.e., photosynthesis, was not affected by higher dissolved inorganic C availability and none of the remaining response variables showed any significant differences. Our findings suggest that pulsation is a phenotypically plastic mechanism for X . umbellata to adjust to different pH values, resulting in reduced growth rates only, while maintaining high productivity. Consequently, pulsation may allow X . umbellata to inhabit a broad pH range with minimal effects on its overall health. This resilience may contribute to the competitive advantage that soft corals, particularly X . umbellata , have over hard corals.
... Chlorophyll content was measured according to Winters et al. (2009a) and Ferrier-Pagès et al. (2010). This method was developed by Jeffrey and Humphrey (1975) and was widely used to study chlorophyll in aquatic ecosystems such as algae, natural phytoplankton, and zooxanthellae (Winters et al., 2009a;b;Ferrier-Pagès et al., 2010;Gentine et al., 2022;Martell, 2022). Briefly, coral tissue was removed from the skeleton with filtered seawater (FSW) emitted from a high-pressure water gun attached to a SCUBA cylinder, collected into 50-ml centrifuge tubes (Mayfield et al., 2013). ...
... After discarding the filter membrane, the sample was centrifuged for 15 min at 4000g, and the supernatant was utilized to measure the absorbance at 664 nm and 630 nm. The pigment contents were calculated using the equations proposed by Jeffrey and Humphrey (1975) and expressed as μg chlorophyll per 10 6 cells. ...
Sulfamethoxazole (SMX) is widely present in water systems, and its stable properties and poor biodegradability can result in high residues of SMX in the water environment. This, in turn, can have detrimental effects on the entire aquatic habitat and human life and health. This study aimed to investigate the toxic effects of SMX on the growth, photosynthetic pigment content, and oxidative stress of two marine microalgae species: Skeletonema costatum and Phaeodactylum tricornutum. SMX demonstrated a significant inhibitory effect on microalgae proliferation , with 96-h median effective concentration (EC 50) values of 0.93 mg/L and 4.65 mg/L for S. costatum and P. tricornutum, respectively. At low concentrations, SMX significantly increased the production of Chl a in both microalgae species. However, in the higher concentration SMX treatment group, Chl a content in P. tricornutum experienced a significant decrease, whereas Chl c showed no sensitivity to SMX. The activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), along with the glutathione (GSH) content, exhibited a significant increasing trend in response to higher SMX concentrations. However, these changes effectively inhibited the accumulation of malondialdehyde (MDA) content. In the treatment group with the highest SMX concentration, MDA content in both microalgae species was significantly higher compared to the control group. The Integrated Biomarker Response Version 2 (IBR v2) index showed a significant positive correlation with SMX concentration, suggesting its potential for assessing the ecotoxicological effects of lower SMX concentrations on marine microalgae.
... However, it was later discovered that the Arnon formula for calculating chlorophyll content relied on incorrect extinction coefficients for chlorophyll a and b (Porra et al. 1989;Porra 2002;Esteban et al. 2018). As a consequence, more accurate and efficient methodologies for chlorophyll estimation were subsequently formulated (Jeffrey and Humphrey 1975;Lichtenthaler 1987;Porra et al. 1989;Wellburn 1994). ...
Rice crops experience biotic (weeds) and abiotic stress (drought) at early in the season when the plants are most susceptible to weed competition, which results in oxidative stress in rice. Oxidative stress is an important factor that could decrease plant yield. The main aim of this study was to investigate the biochemical, physiological, and yield responses of rice in the presence of its major weeds (Echinochloa colona (L.) Link. and Alternanthera paronychioides A. St.-Hil.) during the critical competitive period (25 days after sowing) under drought stress and identifying the differential sensitivity of rice towards the weeds. In the presence of weeds, the rice physiological, biochemical attributes and yield of rice are negatively affected under drought, which was evident by a decline in relative water content, membrane stability index, antioxidant enzymes, non-enzymatic oxidants and chlorophyll content linked with the accumulation of reactive oxygen species (ROS). However, the extent of reduction in these traits of rice was greater and the accumulation of ROS was higher in the presence of E. colona than A. paronychioides, indicating a higher sensitivity towards E. colona under drought stress. The highest accumulation of MDA was observed under drought due to A. paronychioides (38.66 µg g⁻¹ FW) and E. colona (66.21 µg g⁻¹ FW) interference. Besides this superoxide content increased by 6.81 µmol g⁻¹ FW and 8.36 µmol g⁻¹ FW in the presence of A. paronychioides and E. colona, respectively under drought stress. This oxidative stress significantly reduced the yield. Overall, our study provides the characterization of trait responses of rice to biotic (weeds) abiotic stresses (drought) at the physiological and biochemical level and can serve as starting point for further in-depth research.
... The absorption values of the supernatant at 480, 510, 630 and 664 nm were determined by UV spectrophotometer (UH-5300, HITACHI, Japan). The calculation methods of Jeffrey and Humphrey (1975) and Parsons et al. (1984) were as follows: ...
As an invasive species of macroalgae, Sargassum muticum (Yendo) Fensholt has invaded European shores and the Mediterranean, and even drifting individuals have been observed in sea area near the Canary Islands, becoming a potential species responsible for the "Sargassum golden tide". When drifting on the sea surface, algae receive more ultraviolet radiation (UVR). However, photosynthetic responses and adaptation mechanism of S. muticum to UVR remain unclear. In this study, thalli of S. muticum were respectively exposed under two radiation treatments of 200 W m − 2 PAR (photosynthetically active radiation, 400-700 nm), and 200 W m − 2 PAR + 38 W m − 2 UVR (280-700 nm) for 120 mins, and then recovered at a low light (PAR) of 10 μmol photons m − 2 s − 1 for 240 mins. During this treatment, the photosynthetic properties of algae were measured, to investigate the responses and protection mechanism of S. muticum to UVR. The results showed that photosynthesis of thalli was significantly inhibited by UVR, reflected by decreased maximum photochemical quantum yield (F v /F m) and chlorophyll content, and changes of parameters of rapid light response curve and chlorophyll fluorescence induction curve in PAR and PAR + UVR treatments. Meanwhile, algae actively adopted several strategies to alleviate the inhibition caused by UVR, including photoprotection characterized by increased contents of UV-absorbing compounds (UVACs) and carotenoids (Car), excess light energy dissipation by elevated non-photochemical quenching (NPQ) coupled to the xanthophyll cycle, and photorepair manifested as an accelerated synthesis of D1 protein and enhanced antioxidant for scavenging ROS. Benefiting from the effects of the above several pathways, after 240 mins of low light recovery, photosynthesis was greatly restored in these two radiation treatments, with the restoration of F v /F m and parameters of rapid light response curve and chlorophyll fluorescence induction curve. Based on these results, we conservatively speculate that the photosynthesis of drifting S. muticum individuals may be restored in the evening with low light levels after being damaged by UVR on the surface of sea at midday, resulting in maintaining rapid growth and forming a golden tide.
... The sea surface temperature (SST) and surface salinity were recorded simultaneously with a conductivity, temperature, and depth (CTD) recorder (Sea-Bird Scientific, Bellevue, WA, USA). Surface water samples for measuring the concentrations of dissolved oxygen (DO) and chlorophyll a (chl a) were obtained with a 5 l Niskin bottle; DO was measured according to the Winkler procedure (Strickland & Parsons, 1972), and chlorophyll a was measured according to Jeffrey & Humphrey (1975), using a PerkinElmer Lambda 2 spectrophotometer (Shelton, CT, USA). ...
Estimates of the prevalence of dead zooplankton are increasingly necessary in marine ecological studies. We aimed to identify the relative proportions of live/dead individuals of three of the historically most abundant taxa of zooplankton in Magdalena Bay, Mexico: copepods, decapods, and diplostracans. Abundance data and environmental variability were recorded monthly at neap tides during 2015–2018. Samples were stained with neutral red to distinguish living from dead individuals. Copepods were the most abundant group and showed a significant annual variability in their abundance during the study period. Influenced by a preceding warm spell and the El Niño event of 2015–2016, the lowest abundances and the highest recorded standing mortalities of all three taxa were reported in 2015; standing mortality during El Niño was double that otherwise observed. A significant correlation was found between some of the environmental variables analyzed (salinity, temperature) and increased standing mortalities in copepods and decapods. We found differences between the percentages of live/dead organisms between the years analyzed and also between the taxonomic groups involved (copepods 17%, decapods 21%), which underlines the importance of including mortality analyses in ecological studies of zooplankton.
... Symbiont density was measured using a hemocytometer (Marienfeld, Germany), with four replicate counts for each sample. Subsamples of the homogenate were extracted in 90% acetone at 4 °C for 24 h, and the Chl a, Chl c and carotenoids content was calculated using a microplate reader (Epoch, BioTek, USA) according to the Jeffrey andRitchie (1975, 2006): Symbiont density was reported as cells cm −2 , and the pigment content was normalized to the symbiont density (pg cell −1 ). ...
Corals dwelling in coastal reefs persistently inhabit turbid waters characterized by limited light availability. However, the adaptive strategies and mechanisms underlying such resilience to low light stress, particularly the role of heterotrophic inputs and physiological trade-offs, are still poorly understood. Here, we used the dominant coral species in coastal Indo-Pacific reefs, Galaxea fascicularis, as a model and investigated its responses to combinations of four light levels and two feeding regimes. We focused on processes like symbiont physiology, photosynthetic capacity, skeletal growth, and asexual reproduction (budding rate) to determine any physiological strategies utilized by the coral. Our results showed that G. fascicularis acclimates to light limitation by improving photosynthetic efficiency (α), and that heterotrophic input had an apparent enhancement effect on most physiological processes. We also found that G. fascicularis can adopt complex trade-offs between a variety of physiological processes to acclimate to multiple light and feeding conditions. Specifically, in the case of autotrophic limitation, G. fascicularis preferentially maintained skeletal growth and symbiont physiology, while budding rate was compromised. Therefore, our study demonstrates that increased heterotrophic input and physiological trade-offs are critical for the persistence and resilience of corals under low light conditions. The findings of this study can provide valuable insights for targeted conservation and management efforts aimed at protecting coral reefs in light-limited habitats.
Eutrophication is a main threat to continental aquatic ecosystems. Prevention and amelioration actions have been taken under the assumption of a stable climate, which needs reconsideration. Here, we show that reduced precipitation can bring a lake ecosystem to a more productive regime even with a decline in nutrient external load. By analyzing time series of several decades in the largest lake of the Iberian Peninsula, we found autocorrelated changes in the variance of state variables (i.e., chlorophyll and oxygen) indicative of a transient situation towards a new ecosystem regime. Indeed, exceptional planktonic diatom blooms have occurred during the last few years, and the sediment record shows a shift in phytoplankton composition and an increase in nutrient retention. Reduced precipitation almost doubled the water residence time in the lake, enhancing the relevance of internal processes. This study demonstrates that ecological quality targets for aquatic ecosystems must be tailored to the changing climatic conditions for appropriate stewardship.
Microbial biodiversity is fundamental to maintain ecosystem functioning in seasonally variable ecosystems. However, it remains unclear how alterations in water availability caused by episodic drying compromise the ability of stream microbes to maintain multiple functions simultaneously (e.g., primary production and carbon cycling). Using data from 32 streams, we investigated how the phenology of annual drying influences stream sediment microbial biodiversity and their capacity to sustain multifunctionality. Our results showed that stream multifunctionality and most bacteria did not respond to changes in drying phenology. Only two bacterial groups, the drying‐resistant Sphingobacteriia and the drying‐sensitive Acidobacteria_Gp7, exhibited positive associations with multifunctionality; whereas, bacterial diversity showed a negative correlation with functions. Among these biodiversity aspects, Sphingobacteriia showed the strongest capacity to maintain multifunctionality at low and moderate performance levels. Our findings will help to better understand the mechanisms through which biodiversity sustains the functioning of seasonally variable streams and their responses to global change.
In Egypt, the beet sugar industry produces huge amounts of solid wastes called
beet filter cake (BFC), which presents a problem for disposal, polluting the
environment. On the other hand, the commercial production of cyanobacterium
Spirulina platensis as an alternative protein source is costly. Therefore, this study
intended to recycle BFC waste by exploiting it for the economical production of
single-cell protein Spirulina platensis on a large scale using an open raceway pond.
The cultivation was done in winter using two open ponds of 1000L capacity fitted
with a paddle wheel for mixing, which was constructed in the Faculty of Science,
Mansoura University, Egypt. One of them was for standard Zarrouk's medium
(SZM), and the other was for an optimized beet filter cake extract (BFCE) medium.
Environmental conditions, such as temperature and solar radiation, as well as growth
parameters, such as optical density, photosynthetic activity, specific growth rate, and
dry weight were monitored every two days. Experimental results showed that the
temperature was 19.1- 21°C in SZM and 17.8- 21°C in the optimized BFCE, and the
pH increased during the cultivation period to maximum values of 10.5 and 11.1 in
SZM and optimized BFCE, respectively, which maintains alkaline conditions. The
maximum dry weight values were 0.47 and 0.57g/ l in SZM and optimized BFCE
medium at the end of the cultivation period, and there was no significant difference
in the Fv/ Fm values in both media. Furthermore, no significant differences were
observed in the protein content in both media, which was 55.11± 0.75 and 52.58±
1.31 in SZM and optimized BFCE medium. The cost of biomass produced from
optimized BFCE medium is 2.6 times cheaper than that of Zarrouk's medium.
Finally, we concluded that optimized BFCE can be used as a promising, cost�effective medium for the large-scale production of single-cell protein Spirulina
platensis.
Cyanobacteria are regarded as vital constituents of aquatic ecosystems which recently become viable option for bioremediation since it can remove contaminants from polluted water. They possess intriguing metabolic properties and exhibit differential growth patterns. This study elucidates the isolation and identification of two marine and two freshwater indigenous Oscillatoria spp., their growth performance, nutritional composition along with intricate biochemical profiles. Agar streak plate method was used for the isolation, growth curve was determined through chlorophyll content and optical density. Freshwater and marine Oscillatoria spp. were mass cultured in commercial Bold Basal Media and Conway media respectively. Wet biomass was harvested through centrifugation at the early stationary phase of their respective growth curve and oven-dried at 40 °C to determine the nutritional and biochemical profiles. Oscillatoria sp. 2 displayed significantly higher (p ˂ 0.05) chlorophyll-a (22.72 ± 0.04 µg/mL) and OD value (1.87 ± 0.03) in the stationary phase (9th to 11th day) than the other species. Crude protein contents (%) varied from 21.56 ± 0.09 to 56.97 ± 0.03. Crude lipid (%) ranged from 9.07 ± 0.07 to 17.13 ± 0.13 and Crude fiber content (%) showed the range from 7.49 ± 0.15 to 17.04 ± 0.08. Fatty acid and amino acid were also found variable among the species. Present study will contribute to the meticulous selection and characterization of Oscillatoria sp. to utilize it in the rigorous scientific investigations and diverse commercial applications.
The distribution of symbiotic scleractinian corals is driven, in part, by light availability, as host energy demands are partially met through translocation of photosynthate. Physiological plasticity in response to environmental conditions, such as light, enables the expansion of resilient phenotypes in the face of changing environmental conditions. Here we compared the physiology, morphology, and taxonomy of the host and endosymbionts of individual Madracis pharensis corals exposed to dramatically different light conditions based on colony orientation on the surface of a shipwreck at 30 m depth in the Bay of Haifa, Israel. We found significant differences in symbiont species consortia, photophysiology, and stable isotopes, suggesting that these corals can adjust multiple aspects of host and symbiont physiology in response to light availability. These results highlight the potential of corals to switch to a predominantly heterotrophic diet when light availability and/or symbiont densities are too low to sustain sufficient photosynthesis, which may provide resilience for corals in the face of climate change.
Estuarine systems, being situated at the interface between land and marine environments, are important sites for nitrate (NO3–) retention and processing due to large inputs, long retention time, and high biogeochemical activity. However, it remains uncertain how pelagic and benthic processes control NO3– cycling and how these differ between contrasting seasons. In this study, we measured pelagic and benthic assimilatory and dissimilatory NO3– processes in a large lagoon (Curonian Lagoon, SE Baltic Sea) to understand changes in NO3– cycling in relation to variation in riverine inputs and shifts in phytoplankton community composition. We show that in spring, benthic dissimilatory and assimilatory NO3– processes were important, while in summer, pelagic assimilatory processes dominated. During spring, diatom blooms promote greater delivery of nitrogen (N) and labile organic matter to the benthos resulting in greater denitrification in the sediments and a net flux of NO3– from the water column to the sediments. In summer, phytoplankton blooms dominated by buoyant cyanobacteria exhibited high rates of assimilatory uptake and greater particulate organic N export to the sea, but low rates of sediment–water exchange. Cyanobacteria blooms were associated with higher absolute rates of NO3– uptake, as well as higher mass-specific rates compared to spring. Given the low dissolved inorganic N in summer, high uptake indicates that the pelagic community possessed a nutritional strategy to efficiently utilize multiple N forms. Overall, our findings show that the seasonal succession from diatom to cyanobacteria-dominated communities is associated with a shift from strong benthic-pelagic coupling to predominantly pelagic-based N cycling.
Coral propagation- and planting-based reef restoration practices are accelerating globally, yet short-term “success” continues to be measured as broad metrics of coral survival and growth, even though goals are often centred on recovering broad ecosystem service values. As such, how restoration activities may impact healthy reef functioning remains uncertain. For example, trade-offs in resource acquisition and partitioning that potentially regulate growth vs survival may yield very different outcomes towards factors governing reef biogeochemical cycles. Here we considered a proof-of-concept “multi-trait” approach to capture how a broader range of functional traits reflect the expression of growth and survival for a key coral species (Acropora cf. hyacinthus) — impacted by recent mass bleaching events — propagated for restoration activities on the Great Barrier Reef (GBR), Australia. We examined a diverse array of bio-physical, bio-chemical, and skeletal traits (n = 91 traits) for wild (donor) colonies and their nursery-derived fragments from a 12-month growth period (Opal Reef, northern GBR). Nursery corals grew 20-25 times faster than their donor (wild) colonies, but both exhibited similar survivorship. Faster growth within nurseries was accompanied by more pigmented colonies (darker-coloured and with more symbionts), and higher photosynthesis, respiration, and calcification rates. However, despite these metabolic changes, biogeochemical properties of the nursery and reef corals (carbohydrates, lipids, proteins, elemental stoichiometry, and skeletal properties) remained largely the same after 12 months, suggesting the bio-energetic value to trophic transfer as well as the structural rigour of corals was unaltered by nursery propagation. Thus, a “multi-trait” approach enables more informed evaluation as to how propagation activities impact diverse ecosystem service values, highlighting the immense importance of this knowledge in choosing coral individuals for restoration. Our example provides confidence to practitioners that key ecosystem service attributes of native corals are largely retained through an intermediate nursery growth phase that can accelerate coral biomass gains.
Efficient nutrient recycling underpins the ecological success of cnidarian-algal symbioses in oligotrophic waters. In these symbioses, nitrogen limitation restricts the growth of algal endosymbionts in hospite and stimulates their release of photosynthates to the cnidarian host. However, the mechanisms controlling nitrogen availability and their role in symbiosis regulation remain poorly understood. Here, we studied the metabolic regulation of symbiotic nitrogen cycling in the sea anemone Aiptasia by experimentally altering labile carbon availability in a series of experiments. Combining ¹³C and ¹⁵N stable isotope labeling experiments with physiological analyses and NanoSIMS imaging, we show that the competition for environmental ammonium between the host and its algal symbionts is regulated by labile carbon availability. Light regimes optimal for algal photosynthesis increase carbon availability in the holobiont and stimulate nitrogen assimilation in the host metabolism. Consequently, algal symbiont densities are lowest under optimal environmental conditions and increase toward the lower and upper light tolerance limits of the symbiosis. This metabolic regulation promotes efficient carbon recycling in a stable symbiosis across a wide range of environmental conditions. Yet, the dependence on resource competition may favor parasitic interactions, explaining the instability of the cnidarian-algal symbiosis as environmental conditions in the Anthropocene shift towards its tolerance limits.
Harmful algal blooms (HABs) caused by Heterosigma akashiwo are occurring in coastal waters frequently, posing a great risk to marine environments and subsequent treatment processes like desalination. UV-assisted permanganate oxidation (UV/KMnO4) is recognized as an innovative advanced oxidation process. This study investigated the inactivation and removal efficiencies of H. akashiwo cells by UV/KMnO4. Algal cells were effectively disintegrated into fragments by UV/KMnO4. Also, the degradation of photosynthetic pigments, membrane lipid peroxidation, and severe oxidative stress in algal cells was observed. The removal efficiency of algal cells reached 80.2% by 20 min of UV/KMnO4 oxidation, with a KMnO4 dosage of 5 mg L−1. In addition, the residual algal cells could be completely removed by a subsequent self-settling process, without an additional coagulation procedure. The fragmentation of algal cells caused by UV/KMnO4 may facilitate the formation of algal flocs, thereby improving the cell settleability. Furthermore, UV254 was significantly reduced by UV/KMnO4, which is expected to reduce the formation of disinfection byproducts and membrane fouling. This study elucidates that UV/KMnO4 can be a promising technique for the efficient treatment of harmful marine algae.
The methine proton signals of certain N,N‐di‐2‐propyl amides were shown to broaden selectively as the temperature is lowered. For N,N‐di‐2‐propyl isobutyramide, the high‐field methine signal broadened around room temperature, but sharpened again between −50° and −60°C. For other related amides, the low‐field methine signals broke up into subsets of signals at low temperature. This broadening and multiplicity is interpreted as evidence for slow rotation around the 2‐propyl‐to‐nitrogen bonds. This sort of behavior is viewed as potentially a serious complication in determining rotation rates by PMR‐signal‐shape analysis for rotors to which the 2‐propyl and related groups are attached.
The NMR spectra for a series of amides and thioamides of type magnified image where R = CH 3 , C 6 H 5 and C 6 H 5 CH 2 , were investigated from −60° to 150°C. The Arrhenius activation energies, E a , for the normal amide equilibration were determined by the W ½ method and the values range from 15.4 to 20.9 Kcal/mole.
The three thioamides, compounds ( 2 ), ( 4 ) and ( 6 ) yield spectra showing a second, low temperature, equilibration. This exchange was first studied by Siddall and co‐workers and they interpreted the spectral changes in terms of population changes of the conformational isomers about the NCH bonds. They assumed strong interaction of nitrogen alkyl groups which gave rise to three low energy dl pairs of isomers. Their results, however, as well as those obtained for similar compounds reported herein, show only two sets of patterns at low temperatures. These spectra suggest a first order, A⇄B, type equilibration where P A ≠P B . An alternative assignment based upon the following classification of steric effects of S, R, R′ and R″, magnified image is suggested; (1) a strong interaction of the sulfur atom with the adjacent alkyl group on the nitrogen atom, R′, (2) a somewhat weaker interaction of R with the adjacent nitrogen alkyl group R″ and (3) a still weaker interaction of the two nitrogen alkyl groups, R′ and R″. This leads to four isomers, two dl pairs, C 1 T 4 , C 6 T 3 and C 1 T 6 , C 6 T 3 , which are expected to have a lower energy than the rest and the first pair is preferred.
The W ½ method of measuring exchange rates was extended to cover A⇄B equilibrations, where P A ≠P B . The results indicate an accuracy that is not significantly lower than that obtained by the more elaborate total line shape analysis.
Mit Hilfe von sterisch fixierten 1-Thioacyl-piperidinen werden Modelle für die magnetische Anisotropie-Wirkung des Thioformamid- und Thioacetamid-Systems entwickelt, die die unterschiedliche Zuordnung der Signale der cis- und trans-N-Methyl-Gruppe beim Dimethylthioacetamid und Dimethylthioformamid (2a) erklären. Anhand der NMR-Spektren von 1-Thioisobutyryl- und 1-Thiopivalyl-4-methyl-piperidin (1c und d) wird der sterische Einfluß des Säurerestes auf die Abschirmverhältnisse diskutiert. 1d sowie das N.N-Dimethyl-thiopivalinsäureamid (2d) zeigen bei Raumtemperatur schnelle Rotation um die C–N-Bindung. – Die 2-Methyl-Gruppe des 1-Thioacetyl-2-methyl-piperidins (1f) ist axial angeordnet.
On the Structure of Thioamides and their Derivatives, Vl 1). Magnetic Anisotropy of the Thio-amide Group
Models of the magnetic anisotropy of the thioformamide and the thioacetamide system are developed with the aid of sterically fixed 1-thioacyl piperidines. In this way the different assignment of the signals of the cis- and trans-N-methyl groups in dimethylthioacetamide and dimethylthioformamide (2a) can be explained. The steric effects of the acid residue on the shielding conditions are discussed on the basis of the n.m.r. spectra of 1-thioisobutyryl- and 1-thiopivalyl-4-methylpiperidine (1c and d). In 1d and in N.N-dimethylthiopivalinamide (2d) rotation around the C–N bond is fast at room temperature. The 2-methyl group in 1-thioacetyl-2-methylpiperidine (1f) is axial.