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Green Bay, Lake Michigan is a freshwater estuary. At GB17 (box) a Great Lakes Observing System (GLOS) buoy has been deployed seasonally since 2012. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
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Quantifying rates of primary production and respiration is fundamental to understanding ecosystem function. This study utilized high-frequency time series, buoy-based sensor data to estimate daily primary production and respiration rates during the summers of 2012–2015 in southern Green Bay, Lake Michigan. Highly coherent diel oscillations of disso...
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The primary productivity and seasonality of phytoplankton and its seasonality in Lake Bosomtwe (Ghana), West Africa were studied from September 2005 to August 2006 using the dissolved oxygen method. The wet weight biomass (0.41±0.37 gCm-2 d-1 , n=25), Chlorophyll a (52.11±19.51 mg m-2 , n=17), mixed layer depth (9.28±3.47 m, n=25), euphotic depth (...
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... Methodological problems arise when the study considers intraday variations: the conventional oxygen bottle method is too laborious for continuous round-the-clock observations (Depew et al., 2006;Mineeva et al., 2016). An investigation into the daily course of oxygen, measured directly in the reservoir using O 2 loggers, makes it possible to estimate short-term (for example, hourly) changes in net ecosystem production during the day and community respiration at night (Staehr et al., 2010;LaBuhn and Klump, 2016). However, it is not possible to obtain hourly changes in basic parameters such as GPP and R (Hanson et al., 2008). ...
... From this study, it was clear that Green Bay has lower cyanobacteria concentrations relative to Saginaw Bay, which in turn has lower cyanobacteria concentrations relative to western Lake Erie. In spite of the very high variability of cyanobacteria blooms shown in Table 4, it has been noted that there is little interannual variability in respiration and gross primary productivity in Green Bay [67]. The average gross primary production of Green Bay is 288 mmol O 2 m −2 day −1 [67] This is a factor of five higher than the gross primary production in Saginaw Bay of 40.6-65.1 mmol O 2 m −2 day −1 reported by Fahnenstiel et al. [68]. ...
... In spite of the very high variability of cyanobacteria blooms shown in Table 4, it has been noted that there is little interannual variability in respiration and gross primary productivity in Green Bay [67]. The average gross primary production of Green Bay is 288 mmol O 2 m −2 day −1 [67] This is a factor of five higher than the gross primary production in Saginaw Bay of 40.6-65.1 mmol O 2 m −2 day −1 reported by Fahnenstiel et al. [68]. While Saginaw Bay has higher cyanobacteria biomass relative to Green Bay, the primary production is higher in Green Bay further indicating the confounding issues of mixed phytoplankton assemblages present in Green Bay. ...
... The standing stock of phytoplankton in 2009 and 2010 correspond to the low seasonal adg. It is also hypothesized that the primary production was the same throughout the study [67] and that diatoms and/or green algae classes outcompeted cyanobacteria in 2009 and 2010, and that increased grazing rates by zooplankton ultimately reduced the standing stock of chlorophyll. Gelbstoff absorption is not a key driver in the blooms in western Lake Erie or Saginaw Bay (Figure 8), where summer blooms are generally dominated by cyanobacteria. ...
Cyanobacteria blooms have been reported to be increasing worldwide. In addition to potentially causing major economic and ecological damage, these blooms can threaten human health. Furthermore, these blooms can be exacerbated by a warming climate. One approach to monitoring and modeling cyanobacterial biomass is to use processed satellite imagery to obtain long-term data sets. In this paper, an existing algorithm for estimating cyanobacterial biomass previously developed for MERIS is validated for Green Bay using cyanobacteria biovolume estimates obtained from field samples. Once the algorithm was validated, the existing MERIS imagery was used to determine the bloom phenology of the cyanobacterial biomass in Green Bay. Modeled datasets of heat flux (as a proxy for stratification), wind speed, water temperature, and gelbstoff absorption along with in situ river discharge data were used to separate bloom seasons in Green Bay from bloom seasons in nearby cyanobacteria bloom hotspots including western Lake Erie and Saginaw Bay. Of the ten-year MERIS dataset used here, the highest five years were considered “high bloom” years, and the lowest five years from biomass were considered “low bloom” years and these definitions were used to separate Green Bay. Green Bay had a strong relationship with gelbstoff absorption making it unique among the water bodies, while western Lake Erie responded strongly with river discharge as previously reported. Saginaw Bay, which has low interannual bloom variability, did not exhibit a largely influential single parameter.
... No entanto, devido à extensa área e à limitação de recursos, os delineamentos amostrais em geral necessitam se restringir à apenas uma coleta em determinado horário, tornando dados noturnos uma premente lacuna do conhecimento científico (Cotovicz et al. 2015), de difícil direcionamento inclusive por questões de segurança. Apesar da potencial importância das mudanças de curto prazo na qualidade da água (Paranhos et al. 1998) e do desenvolvimento de equipamentos autônomos (e.g., boias acopladas a sensores), tornando mais acessíveis as ações de monitoramento de alta resolução temporal (LaBuhn, & Val Klump 2016), ainda não há conjunto de dados de longo prazo que contemplem tanto pressão parcial de O 2 (pO 2 ) quanto de CO 2 (pCO 2 ) nas águas costeiras tropicais eutróficas. ...
Evidências crescentes indicam importantes consequências de mudanças globais relacionadas a eutrofização, hipóxia, acidificação e balanço de gases envolvidos na síntese e degradação biológicas de matéria orgânica (i.e., metabolismo) nas águas costeiras tropicais. No entanto, a escassez de dados sobre a variação nictemeral dos principais gases metabólicos (i.e., oxigênio -O2- e dióxido de carbono -CO2-) ainda restringe nossa compreensão sobre a ciclagem de carbono (C) nesses ecossistemas quentes altamente produtivos, especialmente em condições eutróficas. O objetivo do presente estudo foi analisar a variação nictemeral da pressão parcial de ambos os gases metabólicos (pO2 e pCO2), bem como de parâmetros físico-químicos da água ao longo do inverno de 2018 em uma praia de baía tropical altamente eutrofizada (Baía de Guanabara, região metropolitana do Rio de Janeiro, Brasil), no âmbito dos primeiros resultados do Biomonitoramento Contínuo de Águas do Programa Ecológico de Longa Duração da Baía de Guanabara (BiCA/PELD-Guanabara). Os resultados indicaram intensas alternâncias de supersaturação e subsaturação de CO2 entre os períodos noturno e diurno respectivamente, bem como o oposto para O2. Além disso, a relação negativa de CO2 e temperatura da água foi muito superior à esperada por processos físico-químicos, confirmando a predominância de controles biológicos sobre CO2, acidificação e hipóxia nas águas costeiras eutróficas superficiais. No entanto, declínios matinais de CO2 acompanhando aumentos de temperatura não foram observados em todos os meses, também revelando o papel da pluviosidade sobre a mediana diária de pCO2, provavelmente devido à redução de radiação solar aos autótrofos e incrementos de substratos orgânicos aos heterótrofos ou aportes alóctones desse gás. Como conclusão, intensas variações de curto prazo em gases metabólicos podem apresentar profundas implicações ao balanço de C nas águas costeiras tropicais eutróficas, um componente das mudanças globais que deveria ser melhor avaliado em programas de monitoramento. CONTINUOUS WATER BIOMONITORING IN THE LTER- GUANABARA BAY: STRONG WITHIN-DAY VARIATION OF METABOLIC GASES IN TROPICAL EUTROPHIC CONDITIONS:Growing evidence indicates important global change consequences related to eutrophication, hypoxia, acidification and the balance of gases involved in the biological synthesis and degradation of organic matter (i.e., metabolism) in tropical coastal waters. However, the scarcity of data on within-day variation in main metabolic gases (i.e., oxygen -O2- and carbon dioxide -CO2-) still constrains our understanding of carbon (C) cycling in these highly productive warm ecosystems, especially at eutrophic conditions. Here, the aim was to assess the within-day variation of the partial pressure of both metabolic gases (pO2 and pCO2) associated to water physico-chemical parameters over the winter of 2018 in a beach of highly eutrophic tropical bay (Guanabara Bay, metropolitan region of Rio de Janeiro, Brazil), within the scope of the first results of the Continuous Biomonitoring of Waters of the Long-term Ecological Research Program in the Guanabara Bay (BiCA/PELD-Guanabara, acronym in Portuguese). As a result, intense shifts of supersaturation and undersaturation of CO2 between nocturnal and diurnal periods respectively, and the opposite for O2 were observed. In addition, the negative relationship of CO2 and water temperature was much higher than that expected by physical-chemical processes, confirming the predominance of biological controls on pCO2, acidification and hypoxia in surface eutrophic waters. However, morning declines in pCO2 with increasing temperature were not observed in all months, also revealing the role of rainfall on daily medians of pCO2, likely due to decreased solar radiation to autotrophs and increased terrestrial organic substrates to heterotrophs or the allochthonous CO2 contributions. In conclusion, strong short-term variations in metabolic gases may have profound implications for C balance in eutrophic tropical coastal waters, a component of global change that should be better assessed in monitoring programs.
... Shallow depths and rapid settling rates lead to the deposition of organic matter which intensifies benthic respiration and cause hypoxia under stratified conditions in the mid to late summer (Klump et al., 2017;Labuhn, 2017). LaBuhn and Klump (2016) have shown that summertime primary production in Green Bay supports benthos respiration during this time and is a dominant cause of hypoxia in Green Bay. ...
... An increased anthropogenic input of nitrogen and phosphorus from agriculture, industrial waste and sewage has caused widespread eutrophication [4][5][6][7]. Affected locations include the Baltic Sea [8], Lake Garda in Italy [9,10], the East China Sea [11], Lake Taihu in China [12], Lake Bogoria in Kenya [13,14], Lake Victoria in Africa [15,16], Lake Erie in the United States [17,18], Lake Michigan in the United States [19,20], Lake Columbia in Canada [21,22], Bahía Blanca Estuary in Argentina [23,24] and the Great Barrier Reef in ...
Column integrated algal biomass provides a robust indicator for eutrophication evaluation because it considers the vertical variability of phytoplankton. However, most remote sensing-based inversion algorithms of column algal biomass assume a homogenous distribution of phytoplankton within the water column. This study proposes a new remote sensing-based algorithm to estimate column integrated algal biomass incorporating different possible vertical profiles. The field sampling was based on five surveys in Lake Chaohu, a large eutrophic shallow lake in China. Field measurements revealed a significant variation in phytoplankton profiles in the water column during algal bloom conditions. The column integrated algal biomass retrieval algorithm developed in the present study is shown to effectively describe the vertical variation of algal biomass in shallow eutrophic water. The Baseline Normalized Difference Bloom Index (BNDBI) was adopted to estimate algal biomass integrated from the water surface to 40 cm. Then the relationship between 40 cm integrated algal biomass and the whole column algal biomass at various depths was built taking into consideration the hydrological and bathymetry data of each site. The algorithm was able to accurately estimate integrated algal biomass with R2 = 0.89, RMSE = 45.94 and URMSE = 28.58%. High accuracy was observed in the temporal consistency of satellite images (with the maximum MAPE = 7.41%). Sensitivity analysis demonstrated that the estimated algal biomass integrated from the water surface to 40 cm has the greatest influence on the estimated column integrated algal biomass. This algorithm can be used to explore the long-term variation of algal biomass to improve long-term analysis and management of eutrophic lakes.
... Green Bay was sampled from the RV Neeskay during three cruises -August 2014, and July and August 2015. The sites were based on a 5 × 5 km grid that has been used in previous Green Bay studies (Klump et al., 2009;LaBuhn and Klump, 2016;Lin et al., 2016). Samples were collected from the water column at 0 m (m) and 1 m depths in 2014 and at 1 m depth during both 2015 cruises. ...
Cyanobacterial harmful algal blooms (cyanoHABs) are a growing problem in freshwater systems worldwide. CyanoHABs are well documented in Green Bay, Lake Michigan but little is known about cyanoHAB toxicity. This study characterized the diversity and spatial distribution of toxic or otherwise bioactive cyanobacterial peptides (TBPs) in Green Bay. Samples were collected in 2014 and 2015 during three cruises at sites spanning the mouth of the Fox River north to Chambers Island. Nineteen TBPs were analyzed including 11 microcystin (MC) variants, nodularin, three anabaenopeptins, three cyanopeptolins and microginin-690. Of the 19 TBPs, 12 were detected in at least one sample, and 94% of samples had detectable TBPs. The most prevalent TBPs were MCRR and MCLR, present in 94% and 65% of samples. The mean concentration of all TBPs was highest in the Fox River and lower bay, however, the maximum concentration of all TBPs occurred in the same sample north of the lower bay. MCs were positively correlated with chlorophyll and negatively correlated with distance to the Fox River in all cruises along a well-established south-to-north trophic gradient in Green Bay. The mean concentration of MC in the lower bay across all cruises was 3.0 ± 2.3 μg/L. Cyanopeptolins and anabaenopeptins did not trend with the south-north trophic gradient or varied by cruise suggesting their occurrence is driven by different environmental factors. Results from this study provide evidence that trends in TBP concentration differ by congener type over a trophic gradient.
... Such high-resolution temporal data expands our understanding of hourly to daily dynamics (see e.g. LaBuhn and Klump, 2016), and the ability to extend such high-resolution information into parameters like dissolved phosphate has resulted from the development of in situ sensors capable of unattended subhourly measurements (Zorn et al., this issue). ...
Green Bay has sometimes been referred to as the largest freshwater “estuary” in the world. Its watershed, much of it in intensive agriculture, comprises one-third of the Lake Michigan basin and delivers one-third of the lake's total phosphorus load. At one time, the major tributary, the Fox River, was considered the most heavily industrialized river in North America, primarily from paper manufacturing. Deterioration in water quality and the loss of beneficial and ecological uses have been extensive and began well back into the last century. More recently, the bay has also become a test case for our resolve to remediate and restore ecosystems throughout the Great Lakes and elsewhere. Green Bay has stimulated a significant amount of widely relevant research on the fate and behavior of toxics, biogeochemistry, habitat, biodiversity, and ecological processes. The bay represents a true “proving ground” for adaptive restoration. Key findings of the recent summit on the Ecological and Socio-Economic Tradeoffs of Restoration in the Green Bay Ecosystem are summarized here. Foremost among recommendations of the workshop was the creation of a “Green Bay Ecosystem Simulation and Data Consortium” serving as a data clearing house, building upon the significant progress to date, and developing a modeling framework and visualization tools, furthering public outreach efforts, and ensuring a sustained growth in scientific expertise. Funding was estimated to be on the order of ~$15–20M over the next ~5 years – a modest investment relative to the value of the ecosystem and the long-term cost of inaction.
... The mechanics of how the thermocline forms and breaks down, as well as its stability and interaction with surface and meteorological conditions, is arguably the most critical physical process to understand when evaluating how Green Bay and other polymictic environments will respond to climate change (Cyr, 2012;Trumpickas et al., 2015;Wilhelm and Adrian, 2008). Increases in temperature increase oxygen demand and production of methane within the sediments while cool bottom waters provide the setup for hypoxic conditions in the southern bay (Schulz et al., 1997;Waples and Klump, 2002), displaying the strong role of thermal variability on biogeochemical processes as observed in other lake systems (LaBuhn and Klump, 2016;Piccolroaz et al., 2013;Wik et al., 2014). Additionally, variability in stratification drives the occurrence of hypoxic and anoxic bottom waters and sediment temperature (LaBuhn and Klump, 2016;Waples and Klump, 2002). ...
... Increases in temperature increase oxygen demand and production of methane within the sediments while cool bottom waters provide the setup for hypoxic conditions in the southern bay (Schulz et al., 1997;Waples and Klump, 2002), displaying the strong role of thermal variability on biogeochemical processes as observed in other lake systems (LaBuhn and Klump, 2016;Piccolroaz et al., 2013;Wik et al., 2014). Additionally, variability in stratification drives the occurrence of hypoxic and anoxic bottom waters and sediment temperature (LaBuhn and Klump, 2016;Waples and Klump, 2002). Understanding how Green Bay thermal structure responds to climate and meteorological variability is critical for modeling and forecasting hypoxia in Green Bay as well as assessing how climate variability will impact production and flux of methane, a potent greenhouse gas, in Green Bay (Buchholz et al., 1995;Wik et al., 2014). ...
... Our observations that southwesterly, along-axis winds push surface water northwards, resulting in a reciprocal flow of bottom water observed as a cold water intrusion agrees with previous hypotheses about the mechanisms for these observed water masses (Kennedy, 1982;Waples and Klump, 2002), with the caveat that winds initiating the intrusion do not need to be aligned with the along-axis component of the bay but rather from a generally southerly direction. The intrusions initiate stratification in southern Green Bay, with prolonged stratification setting up conditions for rapid consumption of hypolimnetic oxygen and seasonal hypoxia observed in the bay for decades (LaBuhn and Klump, 2016;Valenta, 2013). Other eutrophic Great Lakes systems have observed similar phenomena where hypoxia is dependent on periodic stratification formed by intrusions of cold water (Biddanda et al., 2018). ...
We present water column thermal structure for two climatically different years: 2012, which experienced abnormally warm spring and summer air temperatures preceded by a relatively low ice winter and 2013, which experienced cooler than average spring and average summer air temperatures and preceded by average ice conditions. Mean bottom water temperatures for the season and during cold water intrusions were significantly warmer in 2012 than 2013 leading to a significantly reduced stratified season in 2012. Cold water intrusions were driven into southern Green Bay by southerly winds while intrusions were terminated when winds switched to persistent northerly winds. 2012 observed a significant increase in northerly winds relative to 2013, decreasing cold water intrusion presence and duration but winds did not fully explain the difference in thermal conditions for southern Green Bay. These cold bottom waters drive stratification in polymictic southern Green Bay while dimictic waters were found to have significantly warmer bottom temperatures during 2012 and a deeper mixed layer. Our observations suggest that relatively shallow (<20 m), seasonally stratified systems may not increase in stratification strength and duration under a warming climate; rather, changing wind climatology and surface heat flux can inform the degree to which the mixing regime can be expected to change and impact stratification and thermal structure of coastal systems. We discuss the biogeochemical implications of different thermal regimes, particularly within the context of multiple drivers of physical water column structure in eutrophic, stratified coastal systems.
... Higher standing stock of phytoplankton following the invasions in Green Bay also indicates that a greater amount of phytoplankton production presumably settles out of the water column. This higher flux of material to sediments likely contributes to increased frequency and extent of bottom hypoxia in southern Green Bay (Klump et al., 2009;Hamidi et al., 2015;Labuhn and Klump, 2016). ...
... Primary productivity continues to decrease along the gradient as well, with post-invasion Lower bay rates significantly greater than Middle bay estimates (Fig. 2b). Other recent primary productivity studies along the gradient documented similar rates in both Lower bay and Middle bay regions Labuhn and Klump, 2016). These rates are 2-3 times greater than those obtained for other Great Lakes following invasion by dreissenid mussels (Lake Erie: DePew et al., 2006;Ostrom et al., 2005;Lake Huron: Fahnenstiel et al., 1995), demonstrating the continued highly eutrophic condition of lower Green Bay. ...
As the largest freshwater estuary in the Laurentian Great Lakes, Green Bay, Lake Michigan (USA) is an important ecosystem presenting both challenges and opportunities for investigating changes in the face of multiple anthropogenic stressors. We collected new data from 2000 to 2007 to assess changes in lower food web interactions after establishment of invasive species (Bythotrephes longimanus and Morone americana in 1988 and Dreissena polymorpha in 1993) and nutrient reductions (1990s). Phytoplankton and zooplankton biomass and composition, as well as primary productivity and zooplankton community grazing rates, were determined along the previously well-studied trophic gradient from the shallow Lower bay to the stratified, open-water Middle bay. A clear trophic gradient still occurred during 2000–2007, with higher nutrients, phytoplankton and zooplankton in Lower bay compared to Middle bay. Phytoplankton abundance and cyanobacteria dominance increased significantly compared to earlier studies. However, integrated primary productivity did not change significantly at either Lower or Middle bay. Zooplankton standing stock decreased in Lower bay, driven primarily by reductions of bosminids, chydorids, and cyclopoid copepods, but did not change in Middle bay. Zooplankton community grazing rates did not change significantly, but shifts in magnitude and seasonality of net phytoplankton growth rates are consistent with increased phytoplankton standing stocks. Changes in zooplankton composition indicate increased predation by invertebrates and decreased fish predation. Shifts in both bottom-up and top-down factors have occurred, with Lower and Middle bay regions more eutrophic and similar to each other as a result of changes in this highly productive Great Lakes embayment.
... The high oxygen demand of benthic respiration in organic rich sediments is likely to quickly draw down DO in the hypolimnion (Sweerts et al., 1991). In eutrophic systems, hypoxia is amplified due to high rates of algal productivity leading to sinking/dying plankton, and the subsequent large source of carbon for water column and sediment respiration (Scavia et al., 2014;Bouffard et al., 2013;LaBuhn and Klump, 2016). In most temperate systems that experience seasonal changes, bottom water hypoxia is commonly associated with the summer thermal stratification . ...
