Diatoms shape the biogeography of heterotrophic prokaryotes in early spring in the Southern Ocean

The interplay among microorganisms profoundly impacts biogeochemical cycles in the ocean. Culture-based work has illustrated the diversity of diatom–prokaryote interactions, but the question of whether these associations can affect the spatial distribution of microbial communities is open. Here, we investigated the relationship between assemblages of diatoms and of heterotrophic prokaryotes in surface waters of the Indian sector of the Southern Ocean in early spring. The community composition of diatoms and that of total and active prokaryotes were different among the major ocean zones investigated. We found significant relationships between compositional changes of diatoms and of prokaryotes. In contrast, spatial changes in the prokaryotic community composition were not related to geographic distance and to environmental parameters when the effect of diatoms was accounted for. Diatoms explained 30% of the variance in both the total and the active prokaryotic community composition in early spring in the Southern Ocean. Using co-occurrence analyses, we identified a large number of highly significant correlations between abundant diatom species and prokaryotic taxa. Our results show that key diatom species of the Southern Ocean are each associated with a distinct prokaryotic community, suggesting that diatom assemblages contribute to shaping the habitat type for heterotrophic prokaryotes.     

A mini-review of microbial consortia: Their roles in aquatic production and biogeochemical cycling

Molecular oxygen (O₂) is a potent inhibitor of key microbial processes, including photosynthesis, N₂ fixation, denitrification, sulfate reduction, methanogenesis, iron, and metal reduction reactions. Prokaryote survival and proliferation in aquatic environments is often controlled by the ability to tolerate exposure to oxic conditions. Many prokaryotes do not have subcellular organelles for isolating O₂-producing from O₂-consuming processes and have developed consortial associations with other prokaryotes and eukaryotes that alleviate metabolic constraints of high O₂. Nutrient transformations often rely on appropriate cellular and microenvironmental, or microzonal, redox conditions. The spatial and temporal requirements for microenvironmental overlap among microbial groups involved in nutrient transformations necessitates close proximity and diffusional exchange with other biogeochemically distinct, yet complementary, microbial groups. Microbial consortia exist at different levels of community and metabolic complexity, as shown for detrital, microbial mat, biofilm, and planktonic microalgal-bacterial assemblages. To assess the macroscale impacts of consortial interactions, studies should focus on the range of relevant temporal (minutes to hours) and spatial (microns to centimeters) scales controlling microbial production, nutrient exchange, and cycling. In this review, we discuss the utility and application of techniques suitable for determining microscale consortial activity, production, community composition, and interactions in the context of larger scale aquatic ecosystem structure and function. Correspondence to: Hans W. Paerl.     

Remarkably Complex Microbial Community Composition in Bromeliad Tank Waters Revealed by eDNA Metabarcoding

To investigate patterns of biotic community composition at different spatial scales and biological contexts, we used environmental DNA metabarcoding to characterize eukaryotic and prokaryotic assemblages present in the phytotelmata of three bromeliad species (Aechmea gamosepala, Vriesea friburgensis, and Vriesea platynema) at a single Atlantic Forest site in southern Brazil. We sampled multiple individuals per species and multiple tanks from each individual, totalizing 30 samples. We observed very high levels of diversity in these communities, and remarkable variation across individuals and even among tanks from the same individual. The alpha diversity was higher for prokaryotes than eukaryotes, especially for A. gamosepala and V. platynema samples. Some biotic components appeared to be species‐specific, while most of the biota was shared among species, but varied substantially in frequency among samples. Interestingly, V. friburgensis communities (which were sampled at nearby locations) tended to be more heterogeneous across samples, for both eukaryotes and prokaryotes. The opposite was true for V. platynema, whose samples were more broadly spaced but whose communities were more similar to each other. Our results indicate that additional attention should be devoted to within‐individual heterogeneity when assessing bromeliad phytotelmata biodiversity, and highlight the complexity of the biotic assemblages gathered in these unique habitats.     

Multifaceted aspects of synchrony between freshwater prokaryotes and protists

Community composition of freshwater prokaryotes and protists varies through time. Few studies contemporarily investigate temporal variation of these freshwater communities for more than 1 year. We compared the temporal patterns of prokaryotes and protists in three distinct habitats for 4 years (2014–2017) in Lake Tovel, a cold‐water lake. This lake showed a marked temperature increase in 2017 linked to altered precipitation patterns. We investigated whether microbial communities reflected this change across habitats and whether changes occurred at the same time and to the same extent. Furthermore, we tested the concept of hydrological year emphasizing the ecological effect of water renewal on communities for its explanatory power of community changes. Microbe diversity was assessed by Illumina sequencing of the V3–V4 hypervariable region of the 16S rRNA gene and 18S rRNA gene, and we applied co‐inertia analysis and asymmetric eigenvector maps modelling to infer synchrony and temporal patterns of prokaryotes and protists. When considering community composition, microbes were invariable in synchrony across habitats and indicated a temporal gradient linked to decreasing precipitation; however, when looking at temporal patterns, the extent of synchrony was reduced. Small‐scale patterns were similar across habitats and microbes and linked to seasonally varying environmental variables, while large‐scale patterns were different and partially linked to an ecosystem change as indicated by increasing water transparency and temperature and decreasing dissolved oxygen. Our advanced statistical approach outlined the multifaceted aspect of synchrony when linked to community composition and temporal patterns.     

Influence of the community of associates on Sirex noctilio brood production is contextual

1. Competition and predation are important components of biotic resistance, which helps define the invasibility of an ecosystem. 2. To search for evidence of biotic resistance to the European woodwasp, Sirex noctilio Fabricius, in North America, cages were used to experimentally exclude the community of associates (natural enemies and competitors) from infested logs. Specifically, the study assessed S. noctilio brood production in pine forests in Ontario and New York, where there was a rich existing community of associates (other wood borers, bark beetles and associated fungi, and parasitoids), and in South Africa, where siricid wasps and pines are not native and a similar associate community is not present. In addition, in Ontario, associates were excluded by size, and for different periods of time to identify important associates and their temporal dynamics. 3. Evidence was found that biotic factors limit S. noctilio in North America, whereby exclusion of natural enemies and competitors had a positive influence on the abundance or presence of S. noctilio brood in Ontario and New York. This influence was absent in South Africa. 4. It is unclear which member(s) of the associated insect community in North America were most important in limiting S. noctilio brood production, although they probably acted quickly (< 2 weeks) following S. noctilio oviposition. 5. Further study is needed to determine whether associates have limited S. noctilio populations in pine forests throughout northeastern North America, and which specific natural enemies and/or competitors are important.     

Environmental rather than spatial factors structure bacterioplankton communities in shallow lakes along a > 6000 km latitudinal gradient in South America

Metacommunity studies on lake bacterioplankton indicate the importance of environmental factors in structuring communities. Yet most of these studies cover relatively small spatial scales. We assessed the relative importance of environmental and spatial factors in shaping bacterioplankton communities across a > 6000 km latitudinal range, studying 48 shallow lowland lakes in the tropical, tropicali (isothermal subzone of the tropics) and tundra climate regions of South America using denaturing gradient gel electrophoresis. Bacterioplankton community composition (BCC) differed significantly across regions. Although a large fraction of the variation in BCC remained unexplained, the results supported a consistent significant contribution of local environmental variables and to a lesser extent spatial variables, irrespective of spatial scale. Upon correction for space, mainly biotic environmental factors significantly explained the variation in BCC. The abundance of pelagic cladocerans remained particularly significant, suggesting grazer effects on bacterioplankton communities in the studied lakes. These results confirm that bacterioplankton communities are predominantly structured by environmental factors, even over a large‐scale latitudinal gradient (6026 km), and stress the importance of including biotic variables in studies that aim to understand patterns in BCC.     

High dissimilarity within a multiyear annual record of pollen assemblages from a North American tallgrass prairie

Grassland vegetation varies in composition across North America and has been historically influenced by multiple biotic and abiotic drivers, including fire, herbivory, and topography. Yet, the amount of temporal and spatial variability exhibited among grassland pollen assemblages, and the influence of these biotic and abiotic drivers on pollen assemblage composition and diversity has been relatively understudied. Here, we examine 4 years of modern pollen assemblages collected from a series of 28 traps at the Konza Prairie Long‐Term Ecological Research Area in the Flint Hills of Kansas, with the aim of evaluating the influence of these drivers, as well as quantifying the amount of spatial and temporal variability in the pollen signatures of the tallgrass prairie biome. We include all terrestrial pollen taxa in our analyses while calculating four summative metrics of pollen diversity and composition – beta‐diversity, Shannon index, nonarboreal pollen percentage, and Ambrosia:Artemisia – and find different roles of fire, herbivory, and topography variables in relation to these pollen metrics. In addition, we find significant annual differences in the means of three of these metrics, particularly the year 2013 which experienced high precipitation relative to the other 3 years of data. To quantify spatial and temporal dissimilarity among the samples over the 4‐year study, we calculate pairwise squared‐chord distances (SCD). The SCD values indicate higher compositional dissimilarity across the traps (0.38 mean) among all years than within a single trap from year to year (0.31 mean), suggesting that grassland vegetation can have different pollen signatures across finely sampled space and time, and emphasizing the need for additional long‐term annual monitoring of grassland pollen.     

Multifaceted approach for the analysis of the phototrophic microbial community in a freshwater recreational area of Xochimilco,México

The freshwater microbial community in a recreational area of Xochimilco, México was investigated and compared based on spatial (three different sites) and temporal (dry and rainy seasons) environmental variables. Many of the 16S- and 18S rRNA gene sequences recovered by DGGE fingerprinting analysis were related to phototrophic microbial phylotypes of known identity. Our genetic and morphological analysis indicated the ubiquitous presence of the microeukaryotic green algae Desmodesmus-Scenedesmus spp. and of the unicellular cyanobacteria Cyanobium spp. as the most representative populations in the samples. While 18S rRNA-DGGE fingerprinting analysis revealed a homogeneous community composition across sites and seasons, the 16S rRNA showed significant differences between localities and seasons. None of the cyanobacteria species with potential to produce toxins were identified across the investigated samples. Correlations between biotic and abiotic variables evidenced an important difference between the dry and the rainy season, with a greater consistency in data from the rainy season. According to Principal Component Analysis (PCA), a strong relation between inorganic nitrogen, species richness, and subaquatic irradiance determines environmental variability in Xochimilco. Complementary and relevant data in results obtained from microscopy, fingerprinting, and statistical analysis applied in ecology indicate that a multifaceted approach to the study of microbial communities is necessary to accomplish a comprehensive scientific framework and to generate proper management strategies.     

Environmental and spatial controls of taxonomic versus trait composition of stream biota

相似文献   

Spatial predictions at the community level: from current approaches to future frameworks

A fundamental goal of ecological research is to understand and model how processes generate patterns so that if conditions change, changes in the patterns can be predicted. Different approaches have been proposed for modelling species assemblage, but their use to predict spatial patterns of species richness and other community attributes over a range of spatial and temporal scales remains challenging. Different methods emphasize different processes of structuring communities and different goals. In this review, we focus on models that were developed for generating spatially explicit predictions of communities, with a particular focus on species richness, composition, relative abundance and related attributes. We first briefly describe the concepts and theories that span the different drivers of species assembly. A combination of abiotic processes and biotic mechanisms are thought to influence the community assembly process. In this review, we describe four categories of drivers: (i) historical and evolutionary, (ii) environmental, (iii) biotic, and (iv) stochastic. We discuss the different modelling approaches proposed or applied at the community level and examine them from different standpoints, i.e. the theoretical bases, the drivers included, the source data, and the expected outputs, with special emphasis on conservation needs under climate change. We also highlight the most promising novelties, possible shortcomings, and potential extensions of existing methods. Finally, we present new approaches to model and predict species assemblages by reviewing promising ‘integrative frameworks’ and views that seek to incorporate all drivers of community assembly into a unique modelling workflow. We discuss the strengths and weaknesses of these new solutions and how they may hasten progress in community‐level modelling.     

Beta diversity of cold-water coral reef communities off western Scotland

Spatial heterogeneity in coral reef communities is well documented. This “species turnover” (beta diversity) on shallow warm-water reefs strongly conforms to spatial gradients in the environment as well as spatially autocorrelated biotic processes such as dispersal and competition. But the extent to which the environment and spatial autocorrelation create beta diversity on deep cold-water coral reefs such as those formed by Lophelia pertusa (Scleractinia) is unknown. The effects of remotely sensed and ground-truthed data were tested on the community composition of sessile suspension-feeding communities from the Mingulay Reef Complex, a landscape of inshore Lophelia reefs off the Scottish west coast. Canonical correspondence analysis determined that a statistically significant proportion (68%) of the variance in community composition could be explained by remotely sensed environmental variables (northerly and easterly aspect, seabed rugosity, depth), ground-truthed environmental variables (species richness and reef macrohabitat) and geospatial location. This variation was further partitioned into fractions explained by pure effects of the environment (51%), spatially structured environmental variables (12%) and spatial autocorrelation (5%). Beta diversity in these communities reflected the effects of both measured and unmeasured and spatially dependent environmental variables that vary across the reef complex, i.e., hydrography. Future work will quantify the significance and relative contributions of these variables in creating beta diversity in these rich communities.     

Spatial and temporal variability in a stratified hypersaline microbial mat community

Hypersaline microbial mat communities have recently been shown to be more diverse than once thought. The variability in community composition of hypersaline mats, both in terms of spatial and temporal dimensions, is still poorly understood. Because this information is essential to understanding the complex biotic and abiotic interactions within these communities, terminal restriction fragment analysis and 16S rRNA gene sequencing were used to characterize the near-surface community of a hypersaline microbial mat in Guerrero Negro, Mexico. Core samples were analyzed to assay community variability over large regional scales (centimeter to kilometer) and to track depth-related changes in population distribution at 250-μm intervals over a diel period. Significant changes in total species diversity were observed at increasing distances across the mat surface; however, key species (e.g. Microcoleus sp.) were identified throughout the mat. The vertical position and abundance of >50% of the 60 peaks detected varied dramatically over a diel cycle, including Beggiatoa sp., cyanobacteria, Chloroflexus sp., Halochromatium sp., Bacteroidetes sp. and several as-yet-identified bacteria. Many of these migrations correlated strongly with diel changes in redox conditions within the mat, contributing to strong day–night community structure differences.     

Effects of environmental variation and spatial distance on Bacteria,Archaea and viruses in sub-polar and arctic waters

We investigated the influence of environmental parameters and spatial distance on bacterial, archaeal and viral community composition from 13 sites along a 3200-km long voyage from Halifax to Kugluktuk (Canada) through the Labrador Sea, Baffin Bay and the Arctic Archipelago. Variation partitioning was used to disentangle the effects of environmental parameters, spatial distance and spatially correlated environmental parameters on prokaryotic and viral communities. Viral and prokaryotic community composition were related in the Labrador Sea, but were independent of each other in Baffin Bay and the Arctic Archipelago. In oceans, the dominant dispersal mechanism for prokaryotes and viruses is the movement of water masses, thus, dispersal for both groups is passive and similar. Nevertheless, spatial distance explained 7–19% of the variation in viral community composition in the Arctic Archipelago, but was not a significant predictor of bacterial or archaeal community composition in either sampling area, suggesting a decoupling of the processes regulating community composition within these taxonomic groups. According to the metacommunity theory, patterns in bacterial and archaeal community composition suggest a role for species sorting, while patterns of virus community composition are consistent with species sorting in the Labrador Sea and suggest a potential role of mass effects in the Arctic Archipelago. Given that, a specific prokaryotic taxon may be infected by multiple viruses with high reproductive potential, our results suggest that viral community composition was subject to a high turnover relative to prokaryotic community composition in the Arctic Archipelago.     

Spatio-temporal patterns of eukaryotic biodiversity in shallow hard-bottom communities from the West Antarctic Peninsula revealed by DNA metabarcoding

Aim

We studied molecular eukaryotic biodiversity patterns in shallow hard-bottom Antarctic benthic communities using community DNA metabarcoding. Polar ecosystems are extremely exposed to climate change, and benthic macroinvertebrate communities have demonstrated rapid response to a range of natural and anthropogenic pressures. However, these rich and diverse ecosystems are poorly studied, revealing how little is known about the biodiversity of the Antarctic benthos associated with hard-bottom habitats.

Location

West Antarctic Peninsula and South Shetland Islands.

Methods

Using data collected in seven localities along the western Antarctic Peninsula, we calculated spatial patterns of alpha and beta diversities. Furthermore, we analysed temporal changes in benthic composition in one location (Deception Island) over 3 years. We calculated the temporal alpha and beta diversities to reveal changes in this community over time.

Results

We obtained a final list of 2057 molecular operational taxonomic units. We found significant differences in benthic community composition between localities and among years. Our dataset revealed a total of 10 different kingdom-level lineages and 34 different phyla in the samples. The most diverse phylum was Arthropoda, followed by Bacillariophyta, and Annelida, while the highest relative read abundances belonged to Annelida, Porifera and Echinodermata. Benthic community compositions changed between 2016 and 2018 in Deception Island, and decreasing species richness was the main component of temporal beta diversity.

Main Conclusions

Direct sampling methods are required for monitoring these complex communities. Informative biodiversity patterns can be retrieved even though most of the benthic biodiversity found in Antarctic habitats is yet to be taxonomically described and barcoded. Hard-bottom assemblages exhibit high spatial variability and heterogeneity, not related to depth, which represent a huge challenge for large-scale studies in the Southern Ocean. Local patchiness and structure within these communities are probably a consequence of a combination of several biotic and abiotic factors (i.e. ice disturbance, food supply and competition).     

台风利奇马对海水贝塘浮游生物群落的影响

为了揭示台风前后海水池塘贝类养殖过程中浮游生物群落结构的变化,对养殖水体环境基因组DNA中16S和18S rRNA基因进行了高通量测序和生物信息学分析。结果显示,原核生物OTU数(28728)明显高于真核生物(8498),其中原核生物优势类群主要为变形菌门(Proteobacteria)、蓝藻门(Cyanobacteria)、拟杆菌门(Bacteroidetes)、放线菌门(Actinobacteria)和绿菌门(Chlorobi)等;真核生物优势类群为纤毛虫、鞭毛虫、原绵虫、杯鞭虫、隐藻、棕鞭藻和硅藻等,其中硅藻丰度占比在台风后显著性增加(P<0.05)。台风过后真核生物多样性均未发生显著改变,原核生物Shannon指数和Simpson指数出现显著性差异(P<0.05),表现为先降低后升高,而OTU数和Chao I指数则未发生显著改变。PCoA分析显示,台风后原核和真核生物群落结构均产生时间异质性,但仅原核生物群落结构产生显著差异。ANOSIM显示,真核和原核微生物群落在台风前后均存在显著性差异(P<0.05),其中原核微生物每个时间点之间均有显著差异(P<0...     

Effect of forest fire prevention treatments on bacterial communities associated with productive Boletus edulis sites

Cistus ladanifer scrublands, traditionally considered as unproductive, have nonetheless been observed to produce large quantities of king bolete (Boletus edulis) fruitbodies. These pyrophytic scrublands are prone to wildfires, which severely affect fungi, hence the need for fire prevention in producing C. ladanifer scrublands. In addition, B. edulis productions have severely decreased in the last years. A deeper understanding of the B. edulis life cycle and of biotic and abiotic factors influencing sporocarp formation is needed to implement management practices that facilitate B. edulis production. For example, some bacteria likely are involved in sporocarp production, representing a key part in the triple symbiosis (plant–fungus–bacteria). In this study, we used soil DNA metabarcoding in C. ladanifer scrublands to (i) assess the effect of site history and fire prevention treatment on bacterial richness and community composition; (ii) test if there was any correlation between various taxonomic groups of bacteria and mycelial biomass and sporocarp production of B. edulis; and to (iii) identify indicator bacteria associated with the most productive B. edulis sites. Our results show that site history drives bacterial richness and community composition, while fire prevention treatments have a weaker, but still detectable effect, particularly in the senescent plots. Sporocarp production correlated positively with genera in Verrucomicrobia. Several genera, e.g. Azospirillum and Gemmatimonas, were identified as indicators of the most productive sites, suggesting a potential biological role in B. edulis fructification. This study provides a better understanding of the triple symbiosis (plant–fungus–bacteria) involved in C. ladanifer–B. edulis systems.     

18S rRNA metabarcoding diet analysis of a predatory fish community across seasonal changes in prey availability

Predator–prey relationships are important ecological interactions, affecting biotic community composition and energy flow through a system, and are of interest to ecologists and managers. Morphological diet analysis has been the primary method used to quantify the diets of predators, but emerging molecular techniques using genetic data can provide more accurate estimates of relative diet composition. This study used sequences from the 18S V9 rRNA barcoding region to identify prey items in the gastrointestinal (GI) tracts of predatory fishes. Predator GI samples were taken from the Black River, Cheboygan Co., MI, USA (n = 367 samples, 12 predator species) during periods of high prey availability, including the larval stage of regionally threatened lake sturgeon (Acipenser fulvescens Rafinesque 1817) in late May/early June of 2015 and of relatively lower prey availability in early July of 2015. DNA was extracted and sequenced from 355 samples (96.7%), and prey DNA was identified in 286 of the 355 samples (80.6%). Prey were grouped into 33 ecologically significant taxonomic groups based on the lowest taxonomic level sequences that could be identified using sequences available on GenBank. Changes in the makeup of diet composition, dietary overlap, and predator preference were analyzed comparing the periods of high and low prey abundance. Some predator species exhibited significant seasonal changes in diet composition. Dietary overlap was slightly but significantly higher during the period of high prey abundance; however, there was little change in predator preference. This suggests that change in prey availability was the driving factor in changing predator diet composition and dietary overlap. This study demonstrates the utility of molecular diet analysis and how temporal variability in community composition adds complexity to predator–prey interactions.     

Spatial and Temporal Distribution of the <Emphasis Type="Italic">Vibrionaceae</Emphasis> in Coastal Waters of Hawaii,Australia, and France

Relatively little is known about large-scale spatial and temporal fluctuations in bacterioplankton, especially within the bacterial families. In general, however, a number of abiotic factors (namely, nutrients and temperature) appear to influence distribution. Community dynamics within the Vibrionaceae are of particular interest to biologists because this family contains a number of important pathogenic, commensal, and mutualist species. Of special interest to this study is the mutualism between sepiolid squids and Vibrio fischeri and Vibrio logei, where host squids seed surrounding waters daily with their bacterial partners. This study seeks to examine the spatial and temporal distribution of the Vibrionaceae with respect to V. fischeri and V. logei in Hawaii, southeastern Australia, and southern France sampling sites. In particular, we examine how the presence of sepiolid squid hosts influences community population structure within the Vibrionaceae. We found that abiotic (temperature) and biotic (host distribution) factors both influence population dynamics. In Hawaii, three sites within squid host habitat contained communities of Vibrionaceae with higher proportions of V. fischeri. In Australia, V. fischeri numbers at host collection sites were greater than other populations; however, there were no spatial or temporal patterns seen at other sample sites. In France, host presence did not appear to influence Vibrio communities, although sampled populations were significantly greater in the winter than summer sampling periods. Results of this study demonstrate the importance of understanding how both abiotic and biotic factors interact to influence bacterial community structure within the Vibrionaceae.     

Body size determines soil community assembly in a tropical forest

Tropical forests shelter an unparalleled biological diversity. The relative influence of environmental selection (i.e., abiotic conditions, biotic interactions) and stochastic–distance‐dependent neutral processes (i.e., demography, dispersal) in shaping communities has been extensively studied for various organisms, but has rarely been explored across a large range of body sizes, in particular in soil environments. We built a detailed census of the whole soil biota in a 12‐ha tropical forest plot using soil DNA metabarcoding. We show that the distribution of 19 taxonomic groups (ranging from microbes to mesofauna) is primarily stochastic, suggesting that neutral processes are prominent drivers of the assembly of these communities at this scale. We also identify aluminium, topography and plant species identity as weak, yet significant drivers of soil richness and community composition of bacteria, protists and to a lesser extent fungi. Finally, we show that body size, which determines the scale at which an organism perceives its environment, predicted the community assembly across taxonomic groups, with soil mesofauna assemblages being more stochastic than microbial ones. These results suggest that the relative contribution of neutral processes and environmental selection to community assembly directly depends on body size. Body size is hence an important determinant of community assembly rules at the scale of the ecological community in tropical soils and should be accounted for in spatial models of tropical soil food webs.     

Exploration of spatial and temporal patterns of fish diversity and composition in a tropical estuarine system of Mexico

There are many studies of fish assemblages intemperate systems, but little informationexists about tropical estuarine systems,particularly in the Western Atlantic Regionincluding Mexico. We investigated the fishcommunity structure in the Pueblo Viejo lagoon,Veracruz. Biological samples were collectedmonthly for one year at six sites: three withdense stands of Ruppia maritima and threesites without submerged vegetation. For eachsample, temperature, salinity, dissolvedoxygen, turbidity and depth were analyzed. Theunbiased Simpson diversity index, CanonicalCorrespondence Analysis (CCA) and DiscriminantAnalysis (DA) were used to analyze the fishcommunity. Environmental abiotic variablestended to show significant temporal, but notspatial differences. Fish diversity showedonly a weak significant correlation with watertemperature, and relatively strong diversitypeaks, from June to August and April, wererelated to production peaks in the system. Thetwo first axes of CCA accounted for 65% of thespecies-environment biplot variance, whichsuggested that monthly changes of salinity,turbidity and precipitation, and presence orabsence of submerged vegetation, were the mostimportant environmental variables indetermining the observed variability in fishcommunity composition. Further, fish diversitywas significantly different between habitatswith and those without the presence ofsubmerged vegetation (P < 0.02). A DA showedsignificant differences (P < 0.03) in fishcommunity composition between both kinds ofhabitats, with Lagodon rhomboides,Mugil curema and Menidia beryllina(substantially more abundant in habitat withsubmerged vegetation) as the most importantspecies in the discrimination of spatial fishcomposition. Considering both habitatscombined, fewer differences were observed infish diversity and community compositionbetween rainy and dry seasons. Fish communitycomposition showed greater similarity betweenseasons than between habitats, despite the factthat environmental abiotic variables showed aninverse pattern, suggesting that site factors,such as the presence of submerged vegetation,play a more important role in the maintenanceof fish community patterns than those relatedto temporal influence.