Eutrophication of rivers and streams in agricultural lands is one of the main threats for biodiversity and ecosystem functions. This study was focused on seven subtropical streams where agriculture ...is the predominant land use. We tested the hypothesis that (i) eutrophication causes a decrease in taxonomic and functional diversity of zooplankton, leading to potential consequences for the ecosystem integrity. Furthermore, given that the temporal variability in the environmental conditions of each stream may influence the species sorting mechanisms, we also hypothesized that (ii) streams with higher temporal environmental variability have greater taxonomic and functional alpha (α) and temporal beta (β
t
) diversity measures regardless of the trophic state. Thus, we characterized the streams according to their trophic state and analyzed the zooplankton composition, α and β
t
by using taxonomic and functional perspectives. We found differences in the zooplankton composition between mesotrophic and eutrophic streams. However, eutrophic streams supported similar taxonomic and functional α diversity and similar taxonomic β
t
diversity to mesotrophic ones. These results were mainly explained by the occurrence of rare species occupying different temporal niches in eutrophic systems. On the contrary, functional β
t
diversity was lower in the eutrophic streams, being nestedness the ecological mechanisms underlying the variability in the zooplankton functional groups. Streams with higher temporal environmental variability supported greater α taxonomic diversity. However, the β
t
diversity metrics showed no correlation with the environmental variability, suggesting that the environmental filters of the studied systems were the overriding determinants of species turnover. Our study suggests that both taxonomic and functional perspectives should be considered to improve our knowledge on the biotic responses to environmental changes. Also, among all metrics analyzed on the zooplankton community, functional β
t
diversity was the most sensitive indicator of the eutrophication impact.
Anthropogenic stressors on aquatic environments change the relative importance of environmental conditions on spatial species distributions in a regional pool. One way to assess the spatial species ...distribution is measure the beta diversity. This study analyzed the difference in zooplankton beta diversity between natural lakes and artificial reservoirs, to understand whether reservoirs affect beta diversity, and the relative importance of deterministic processes for the spatial distribution of species. We measured beta diversity using Raup-Crick dissimilarity and analyzed the relative impact of environmental filters on beta diversity in 30 reservoirs and 29 shallow lakes located in Brazil, during two seasons (dry and rainy period). Rotifer beta diversity did not differ between lakes and reservoirs, while copepod beta diversity was higher in reservoirs. Environmental filters were important during the dry period for both lakes and reservoirs, indicating that deterministic processes could drive beta diversity during that season. Environmental productivity, estimated by chlorophyll-a, was associated with zooplankton beta diversity in lakes and reservoirs. The spatial turnover of zooplankton communities depended on the biological characteristics of zooplankton groups, and their responses to environmental filters.
Despite being considered beneficial by providing a clean and renewable source of energy, the construction of hydroelectric dams has extremely negative implications for Amazonian fisheries. This study ...investigated the impacts of the Santo Antônio and Jirau hydroelectric dams on the fishery stocks of the Madeira River. This investigation was based on fish catch data from the Z‐31 fishing colony, located in the municipality of Humaitá, in Amazonas State, Northern Brazil. Data were collected daily and provided information on the date of return from each trip, the fish species targeted, and the total catch (kg) between January 2002 and September 2017. The results indicated reductions of 39% in the mean annual catch and 34% in the mean monthly catches. These results highlight the high price paid by local fish communities for the development of hydroelectric power in the Amazon basin.
Reservoirs are intermediate ecosystems between rivers and lakes. These ecosystems break up the landscape by forming artificial lakes connected by rivers and change important ecological processes of ...lotic ecosystems (e.g. organic matter production and nutrient cycling) and thus have direct effects on aquatic biodiversity. We test the hypothesis that damming water courses exerts a negative effect on the zooplankton community by decreasing the alpha diversity. Samplings were conducted in 30 reservoirs and 29 natural lakes in the Neotropics, during two hydrological periods (dry and rainy) in 2001. The study analysed differences in alpha diversity, the number of rare, accessory and constant species, and species composition between the types of lakes. Alpha diversity was significantly higher in natural lakes and species composition differed between natural lakes and reservoirs. Zooplankton alpha diversity was positively related to total phosphorus (best model), indicating that productive environments (natural lakes) gather more species. Our results suggest that reservoirs have negative effect on community structure, whereas natural lakes have an important ecological function for biodiversity conservation because they are refuges for biodiversity.
Disturbances caused by both natural and anthropogenic forces can drive changes in alpha and beta taxonomic diversity and be accompanied by losses or gains in freshwater ecosystem function (e.g., ...secondary productivity and rate of decomposition). In this study, we tested the hypothesis that increases in cladoceran (microcrustaceans) taxonomic beta diversity in highly impacted environments lead to functional simplification and homogenization of community trait composition. This was accomplished by comparing a reference group of low-impact waterbodies (lakes and reservoirs) to high-impact waterbodies located in four regions of northeastern and south Brazil. Functional composition of cladoceran communities was inferred using a suite of morphological, physiological, behavioral, and life-history traits. Differences in taxonomic and functional community composition were tested using univariate and multivariate statistics. Taxonomic beta diversity and functional richness differed significantly between the reference (low-impact) and high-impact waterbodies, where high-impact environments showed higher taxonomic and functional beta diversity and lower functional richness. By contrast, we found functional homogenization of cladoceran communities in just one out of the four regions. Last, we propose that disturbances can affect traits locally in communities, making them rarer until they are lost, by promoting functional simplification. When disturbances are persistent, they lead to functional and taxonomic homogenization.
In floodplains, rotifers are among the most abundant zooplankton organisms and play an important role in ecosystem functioning. Here, we evaluated the distribution of six feeding guilds of ...rotifers including filter C1 (body size: <200 µm), filter C2 (body size: >200 to <600 µm), filter C3 (body size: >600 to <1000 µm), filter C4 (body size: >1000 µm), suctor, and predator for 11 years. We also analyzed the relationship between guild distribution and environmental parameters (i.e., chlorophyll‐a, phosphate, nitrate, ammonia, and inorganic suspended matter). Finally, we investigated the relationship between feeding guilds heterogeneity (abundance inconsistency) and environmental heterogeneity. Sampling occurred every 3 months from 2000 to 2010 in six shallow lakes of the Upper Paraná River floodplains. Filters C1, Filter C2, and suctors were the dominant feeding guilds. Nitrate and chlorophyll‐a shaped the temporal distribution of the guilds. An intermediate value of environmental heterogeneity was correlated with greater feeding guilds heterogeneity, potentially indicating that intermediate disturbance in the environmental variables may allow for greater differences in abundance distribution between rotifer guilds in shallow floodplain lakes. Our study elucidated the role of rotifers in food resource consumption, energy transfer, and competitive relationships in response to temporal environmental heterogeneity in subtropical floodplains.
Patterns of beta diversity of plankton communities in rivers have been mainly determined by hydrological factors that alter the dispersion and composition of species and traits. Rotifers in the Guamá ...River (eastern Amazonian River) were sampled (monthly between October 2017 and June 2019) to analyze the temporal variation of taxonomic and functional beta diversity and its partitions (turnover and nestedness) as well as the effects of temporal, environmental, and seasonal dissimilarities. Taxonomic turnover and functional nestedness over time were observed as well as functional homogenization, which was arguably due to the hypereutrophic condition of the river. There were no seasonal differences in taxonomic and functional beta diversity probably due the low environmental dissimilarity. This study demonstrated that this Guamá River stretch presented low environmental dissimilarity and hypereutrophic waters, which benefited the establishment of a community of species with high taxonomic turnover over time, but with low functional dissimilarity and loss of some functions related to the functional traits evaluated in the ecosystem. It is important to point out that temporal studies should evaluate both taxonomic and functional aspects of communities, mainly because the effect of environmental changes may be more noticeable at the functional level of communities.
The disordered growth of large cities around water bodies causes environmental damage due to discarded plastics and microplastics (MPs) that aquatic organisms can ingest. This study analyzed the ...occurrence, type, and abundance of MPs in the gastrointestinal contents of four species of commercial fish (120 total specimens), namely, Brazilian mojarra (
Eugerres brasilianus
) and mullets (
Mugil curema
,
Mugil curvidens
, and
Mugil liza
), obtained in Porto Seguro in Bahia, Brazil, between March and May 2019.
A priori
probability distributions were generated using a Bayesian approach and simulations to assess MP intake based on varying exposure amounts (θ = 0.2, θ = 0.5, and θ = 0.8).
E. brasilianus
(53.33%) and
Mugil
spp. (41.66%) were contaminated with some types of MPs. Black, blue, and green MPs dominated in the extracted samples, and most measured 1.0 mm in length or smaller. The dominant polymers identified using Fourier transform infrared spectroscopy (FTIR) were polyester, polypropylene, semi-synthetic rayon fiber, and polyamide 6 (nylon). The
a posteriori
probabilities of more than half the
E. brasilianus
and
Mugil
spp. ingesting MPs were 0.336 and 0.008, respectively, indicating that
E. brasilianus
is much more likely to ingest MPs. These simulations can be useful tools for assessing the environmental quality and local anthropic impact of MP ingestion by fish populations.
•Phytoplankton diversity decreased in areas subjected to greater human influence.•Water transparency was negatively associated with phytoplankton diversity.•Nitrate was negatively associated with ...phytoplankton diversity.•Increase in the N:P ratio negatively affected the phytoplankton diversity.
Habitat fragmentation, overexploitation of natural resources, the introduction of alien species and environmental degradation in aquatic environments are the main causes of reductions in aquatic biota diversity. Phytoplankton represent good ecological indicators because they are highly diverse and rapidly respond to a wide array of environmental disturbances. We investigated the interannual variation in alpha diversity of the phytoplankton community in lakes of an alluvial floodplain. We predicted that the phytoplankton diversity decreases over time in lakes and rivers subjected to human activities, whereas those biotopes in areas under pristine environmental conditions do not show a reduction in alpha diversity. Phytoplankton samples were taken quarterly over a period of eleven years (2000–2010), from ten localities associated with three large rivers, which showed different uses of the watershed. The time series of alpha diversity was analysed, to assess the temporal trend, in addition to their relationships with environmental factors. Phytoplankton alpha diversity in the Upper Paraná River floodplain ranged between 4 and 87 species and showed a mean of 30 (±16.5). Sites associated with the Paraná River showed a decline in diversity, which was associated with transparency, nitrogen and phosphorus forms. These results reflect a combination of seston retention by damming and an increase in the N:P ratio, which appears to negatively affect phytoplankton diversity. If temporal trends in environmental variation and the phytoplankton community remain, the future consequences for phytoplanktonic diversity in the Paraná subsystem will be severe, which might cause changes in the trophic structure and dynamics, and therefore in the functioning of environments, since this community is one of the main sources of energy for other trophic levels.
Brazilian coral reefs are the largest and richest reefs in the Southwestern Atlantic Ocean. Despite their historical and tourist importance, coral reefs on the east coast of Brazil remained unknown ...until recently. This study evaluated the structure of the reef-building coral community in three tidal pools along a gradient of anthropogenic disturbance. The pool known as Dolphin Pool is the warmest and has a high abundance of stony coral Siderastrea spp. One endemic species is on the national list of threatened species. Despite the high frequency of water temperatures above the alert threshold for mass bleaching events, the tidal pools have high densities of adults and recruits of reef-building corals. The results highlight the importance of reef formations on the coastal zone of the Royal Charlotte Bank, given the uniqueness of this area, and reinforce the need for further research and adoption of adaptive conservation approaches.
