Figure 44 - uploaded by David Siqueiros-Beltrones
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(a,y,z) Bacillaria socialis; (b,c) Nitzschia longa; (d,e) N. insignis; (f,g) N. angularis; (h,w) N. spathulata; (i,j) N. valdestriata; (k,l) N. bicapitata; (m) N. agnita; (n-r) Cymbellonitzschia banzuensis; (s,t) Nitzschia frustulum; (u,v) N. amabilis; (x) N. distans. Scale bar = 10 μm.
Source publication
A taxonomic analysis of diatoms found on Phyllodictyon pulcherrimum yielded a total of 244 diatom taxa (all illustrated) within 27 orders, 45 families, and 86 genera. The Taxa were briefly documented in a list including identification references and morphometric data. Thirty-eight of the taxa identified at the species and infraspecific levels repre...
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Recent investigations at previously unexplored localities on the Mexican coast have confirmed the high taxonomic potential of benthic marine diatom assemblages (BMDA) in the region. An exploratory study of epiphytic diatoms of macroalgae in the Revillagigedo Archipelago (RA) suggested that further studies would yield many more taxa, prompting the h...
Certain diatom species, mainly those that are conspicuous within an assemblage, may constitute useful references while addressing various ecological and biogeographical issues. This may well be the case with Mastogloia species which are frequently the most diverse diatom taxa in benthic marine assemblages from warm seas. Twenty three new records of...
Citations
... Taxa in Falcula are distributed worldwide (Round et al. 1990), with documented occurrences including the Mediterranean Sea (Voigt 1960), the Black Sea (Ryabushko et al. 2019), some tropical regions (Voigt 1961;Lobban et al. 2012;Risjani et al. 2021), the Gulf of California (López-Fuerte et al. 2020), and the Pacific coasts of Japan (Tanaka et al. 2019;Sugawara et al. 2021). ...
Two members of the marine diatom genus Falcula, which has been little known for a long time, were
found from the surface of some Japanese seaweeds; one was assigned to F. cf. media and the other was
described as a new species, F. rectangularis sp. nov. Aside from the arcuate valves and slit-like apical
fields, typical of the genus, detailed morphological observations using light and scanning electron
microscopy revealed resemblance between F. cf. media and F. rectangularis in areolae, stria density
and lack of costae. However, the two species can be distinguished based on several morphological
features, including the valve length, plastid arrangement, and frustules in girdle view. A three-gene molecular phylogeny recovered these two species as monophyletic with a high interspecific rbcL difference, which in turn were sister to the clade containing taxa that belong to the orders Cyclophorales and Protoraphidales with low support. The members in this poorly supported assemblage share apical fields composed of slits. The two species of Falcula were phylogenetically distinct from
Pseudofalcula hyalina, a member previously assigned to Falcula.
... Micrographs were taken of specimens of representative diatom taxa, and others were selected mainly according to the particular objectives of the study. Taxa identification followed that of [1,2,4,8,9,[16][17][18][19][20][21][22][23][24][25][26][27] and was updated according to the Algaebase electronic platform [28]. ...
... From this perspective, the authors attributed this to the displacement of equitability toward the rare species side of the distribution, whereby the percentage (57%) of the identified genera in the CGCR represented by a single SS (59) or singletons is somewhat higher than that of Revillagigedo BDT (52%) with 53 genera [29]. On the other hand, while the floristics from other studies allocated in the central region of the Gulf of California (CRGC) were not included here, a floristic study of epiphytic diatoms on Phyllodictyon pulcherrimum (Chlorophyceae) in the CRGC was carried out earlier [9]. Although said work did not include a diversity measurement based on the relative abundance of the taxa, it yielded a high species richness (S = 244 taxa) and 86 genera, whereby the best represented of which were Nitzschia (25 SS), Amphora (17), Diploneis (15), Navicula (13), Cocconeis (12), and Achnanthes (7), whilst in RA these were Cocconeis (27), Nitzschia (24), Amphora (23), Navicula (19), Diploneis (17), and Grammatophora (15). ...
... Since 2018, several new records have been added to the diatom flora of the CRCG and NW Mexico, 3 by [31] and 38 by [9], including a new taxon [32]. This, along with the 16 new records and the 13 unidentified taxa in this study, together with the estimated diversity using both relative abundances and the genus-to-species ratio [29], evidence the diversity potential of the region and show the need for continuous floristic efforts in the Gulf of California littorals. ...
The ecological significance of benthic diatom taxocoenoses in marine ecosystems renders them a suitable reference when making decisions on conservation, as well as ecological and biogeo-graphical issues. This study focuses on floristics of epiphytic diatoms of macroalgae from the central region of the Gulf of California and their biogeographical affinities. Based on current floristics for benthic diatoms of the Mexican NW, it was hypothesized that species richness would be higher for the central gulf (transitional) than for the tropical Revillagigedo Archipelago. Additionally, it was hypothesized that it would be composed mainly of common taxa of the region, with tropical and temperate components. Likewise, it was hypothesized that Mastogloia (tropical) would include less taxa and Lyrella would include more taxa in the transitional central gulf. The diatom flora yielded 333 taxa and 101 genera, and out of which the best represented were Navicula with 29 taxa, Amphora (27), Cocconeis (25), Nitzschia (24), Diploneis (19), Achnanthes (13), Halamphora (14), Fallacia (10), Lyrella (9), and Mastogloia (8), adding up to 53% of the total. The inspected diatom taxocoenosis included mostly taxa commonly distributed in the Mexican NW, albeit with 16 new records. This, plus the high species richness, as well as the proportions of selected taxa depicting this diatom taxocoenosis as being of transitional biogeographical affinity, back the posed hypotheses.
... Thus, both diversity and ecological aspects of benthic diatoms should be considered essential in order to have an adequate ecological prospect of any aquatic ecosystem, particularly when developing management plans for protected areas. The high floristic potential of benthic diatoms (Bacillariophyceae) for Mexican littorals has recently been confirmed through surveying new substrata and by studies in hitherto unexplored areas that have yielded numerous new records for the region [3][4][5][6][7] and have enriched the overall species list for the region [6]. According to [8], in some parts of the biosphere where diatoms are abundant, there is very little known about them. ...
... gallopagensis, Gyrosigma parvulum, Psammodictyon pustulatum, Psammodictyon roridum, Seminavis basilica, Trachyneis aspera var. oblonga and Tryblionella nicobarica, among others [7,50]. This indicates a biogeographical connectivity between regions where warm conditions determine the presence of species with a tropical affinity. ...
Recent investigations at previously unexplored localities on the Mexican coast have confirmed the high taxonomic potential of benthic marine diatom assemblages (BMDA) in the region. An exploratory study of epiphytic diatoms of macroalgae in the Revillagigedo Archipelago (RA) suggested that further studies would yield many more taxa, prompting the hypothesis that diversity measurements, based on ecological indices, would be among the highest in pristine environments. Thus, the aim of this research was to enrich the record of epiphytic diatom floristics of the RA, and to estimate species diversity based on information theory (H′). Floristically, 167 identified taxa are added here to the BMDA species list of the RA, bringing the total to 397 taxa overall, including 52 taxa that are potentially new records for the Mexican Pacific coast. Among the most conspicuous genera are Mastogloia with five new taxa and it remains the most diverse genus with 55 taxa overall, followed by Cocconeis (27), Nitzschia (24), Amphora (23), Navicula (19), Diploneis (17) and Grammatophora (15). As expected for a pristine environment, the computed species diversity values for the BMDA were high, ranging from H′ = 3.92–5.2, depicting stability. Future surveys are expected to further increase the species richness of BMDA for the RA.
... Said differences, however, are common and may be exemplified by the fact that similarity values between subsamples of the same sample commonly variate between 60 and 80% and denote the patchy distribution of diatom assemblages [3]. Notwithstanding, the taxonomy of the diatom assemblages from the control site adds relatively few taxa to the floristics of the Baja California Peninsula coasts, while the number and composition of species are similar to those from recent studies in the area [45,54], while showing a typical structure. This is why species composition has to be coupled with numerical presence of said taxa to infer a given response to the contaminants in the sediments of SR. ...
Studies on marine benthic diatoms in environments contaminated by metals are scarce. The typical structure of benthic diatom assemblages (species richness, diversity, dominance, dominant taxa) from undisturbed environments may be used as reference for contrasting with contaminated environments in order to observe how said assemblages respond to such disturbance. Thus, the Ho that the structure of benthic diatom associations and morphology of their frustules under contamination by metals would be normal, as in unpolluted environments was tested. To do this, concentrations of 24 metals were surveyed in a coastal zone impacted by mining residues, and the structure of benthic local diatom assemblages was described. Metal concentrations measurements for 15 metals surpassed the normal values of the upper earth cortex, seven were under the low range effect, and three (Cd, Cu, Zn) surpassed the medium range effect values. At a control site no element concentration was above the reference values for low range effect (LRE) or medium range effect (MRE) standards. There, diatom species richness (S) was high, particularly on seaweeds; where, 397 diatom taxa were recorded. In contrast, at the contaminated area 217 diatom taxa were recorded, but diversity (H') ranged from 2.4 to 4.3. Relative high frequencies of deformed diatom valves mainly of Achnanthes spp. were recorded in contaminated sediments. In general, diatom taxoceno-ses presented a typical structure for non-contaminated environments. However, scarceness of specimens , lower S, and frequency of deformed valves suggest responses to metal contamination. For marine environments, the latter values corresponding to A. longipes may be considered a reliable reference to the response of benthic diatoms to metal contamination.
Background.
The structure of benthic diatom assemblages (BDA) is related to the type of substrate where they flourish.
Goals.
assess the degree of variation shown by BDA growing on live and non-living substrata from a tropical coastal lagoon (Terminos lagoon). We tested the hypothesis that substrate influence would deem significantly distinct BDA.
Methods.
diatom samples were collected from live and non-living substrata from four sites within Terminos lagoon, México, where physicochemical variables were also measured. Diatom taxa were identified, and their relative abundances were estimated and used to compute community parameters (species diversity, equitability, dominance), along with the indicator value (IndVal). Also, similarity between the BDA from the four sites was measured and values were then compared using ANOSIM.
Results.
Although the IndVal showed a clear separation based on the dominant/constant taxa, ANOSIM indicated that differences between the sites were not significant. This may be related to the characteristic patchy distribution of BDA along environmental gradients.
Conclusions.
in coastal ecosystems the structure of BDA could be mainly influenced by environmental variables.
Background. Within any given taxocenosis of benthic diatoms (BDT), the distribution of the taxa relative abundances renders them as very abundant, common, uncommon, and rare taxa. This structure is considered when estimating species diversity using Shannon’s index (H’) based on information theory. Thus, because
this distribution also occurs within the taxonomic hierarchy of BDT, i.e., genera with a high number of spe-
cies-infraspecies (SS) or species singletons, estimating species diversity (H’) using the genus/SS ratio instead of relative abundances, represents an alternative measure of diversity but resorting to a much smaller data matrix. Hence, the diversity index designated H’ G/SS is proposed here. Objective. In this essay, we sought to gather evidence that combining information on the genus-level taxa and their included SS provides a reliable estimation of taxonomic diversity for BDT. Hence, we tested the hypothesis that the estimated H’ G/SS for the floristic of BDT in a particular locality would be as high as the highest value using diatom relative abundances. Method. To test the above, floristic and species diversity (H’) data from several studies of BDT along Mexican shores were analyzed quantitatively under the premise that diversity estimates based on relative abundances of species (H’) or the H’ G/SS index would be equivalent. Results. Statistical tests supported our ypothesis
showing no significant differences between the original values of H’ and those using H’ G/SS . Conclusions. This diversity estimation using H’ G/SS for BDT represents a reliable, quicker, and more comprehensive approach and another parameter that can be used for further conservationist, ecological, and biogeographical purposes.
Antecedentes.
Existe un reciente interés por el estudio de diatomeas bentónicas marinas (DBM) y su respuesta a contaminación por elementos potencialmente tóxicos (EPT), principalmente metales que pueden impactar la composición de especies, alterar los parámetros de las asociaciones, y ocasionar deformaciones de las frústulas de diatomeas.
Objetivo.
Explorar qué cambios en las asociaciones de DBM podrían representar una respuesta a contaminación por EPT en ambientes marinos, usando de referencia la estructura típica de sus asociaciones, incluyendo florística, riqueza, diversidad y dominancia, así como frecuencia de frústulas deformes.
Métodos.
Se tomaron muestras de roca y sedimento en mayo 2015 y enero 2016 en Santa Rosalía, BCS, una playa contaminada con desechos mineros.
Resultados.
Se apoyó parcialmente la hipótesis propuesta, i.e., se registró entre 1 y 7.6% de valvas deformes por sitio; esta frecuencia de frústulas deformes sugiere impacto de contaminación por EPT en el área. Se registraron valores de diversidad de H´ entre 1.1 a 4.3, los cuales están dentro de los intervalos típicos de diversidad para sitios no contaminados, a pesar de que concentraciones de EPT como Cu 3760 mg kg⁻¹, Zn 2294 mg kg⁻¹, Ni 401 mg kg⁻¹, Pb 216 mg kg⁻¹, registradas en el área sobrepasan los valores de efecto de rango medio, indicando que un 50% de la biota presente sería afectada.
Conclusiones.
Las elevadas abundancias de ciertos taxa sugieren su capacidad de tolerar PTE, mientras que aquellos que mostraron deformaciones de sus frústulas podrían considerarse taxa sensibles.
