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Multimetric indices (MMIs) are used worldwide to assess the ecological conditions of aquatic and terrestrial ecosystems. Different criteria and approaches are used to construct MMIs, resulting in widely different indices. Therefore, scientists, managers, and policymakers sometimes question whether such MMIs are useful for biomonitoring and bioassessment programs. Crucial design issues for biomonitoring programs include MMI responsiveness, the bioindicator group used, survey design, field sampling methods, level of taxonomic resolution, metric selection and scoring, and reference condition identification. We performed a meta-analysis on MMI development and applications worldwide to analyze the response of MMIs to different disturbance factors and to determine the degree to which MMI construction features influence their responsiveness to anthropogenic disturbances. We used the Web of Science database to find articles that applied an MMI and related MMI values to an environmental stressor, and we extracted data from 157 articles. We performed random-effects modeling to estimate the overall effect of MMI responses to disturbance and used subgroup analysis to analyze the extent to which the effect sizes varied as a function of different MMI construction features. We found that reference condition criteria had the major effect on MMI responses to disturbance. The environmental disturbance type, the number of metrics, and the ecosystem type to which MMIs were applied contributed more weakly to the effect size variance. The general response of MMIs to disturbance was little affected by the bioindicator group, taxonomic resolution, metric selection criteria, or scoring method. These findings have important implications for designing biomonitoring programs, including developing and improving cost-effective biological indices, because they could enhance MMI development and application protocols. [ABSTRACT FROM AUTHOR]

[Display omitted] • The host-parasite mixed-network structure depends on parasitism form response to the environment. • Host-ectoparasite mixed-network structures tend to be more modular in human-perturbed areas. • The mean intensity of infection of ecto- and endoparasitic forms of parasitism were related to modularity. • The most important traits for species composition among modules were parasite total abundance, host fitness and body size. • Host individual variation is important information for network structure and needs to be acknowledged in future studies. Parasitism is an association based on host individual traits and environmental factors. The complexity of this type of interaction is often lost when studying species-by-species interaction networks. Here we analyze changes in modularity - a metric describing groups of nodes interacting much more frequently among themselves than they do with nodes of other modules, considering the host individual variation and the different forms of parasitism: ecto- and endo-parasitism. For this, we studied mixed networks: bipartite networks comprising host individuals and parasite species as two sets of nodes interacting with each other. We used a fish-parasite mixed network from a highly perturbed coastal river to understand how an anthropogenic perturbation gradient influences the modular structure of host-parasite networks. In addition, we tested how host individual traits drove module configuration within host-parasite mixed networks. Our results showed that different forms of parasitism respond differently to the environment: modularity in fish-ectoparasite networks increased with human perturbation, but modularity was not related to human perturbation in fish-endoparasite networks. In addition, mixed network modules were intrinsically related to individual variation, with host intensity of infection being the most important trait, regardless of the parasite's life form. The effect of total abundance over network structure indicates signs of changes in community equilibrium, with an increase in species with opportunistic behaviors. Module composition was also related to host fitness and body size, which were most predictive in more preserved and diverse river sections. Overall, our results indicate that host-parasite networks are sensitive to ecological gradients marked by human perturbation and that host individual fitness helps to determine network structure. [ABSTRACT FROM AUTHOR]

Non-native predators are known to cause ecological impacts through heightened consumption of resources and decimation of native species. One such species is Micropterus salmoides. Often introduced for sport fishing worldwide; it has been listed by International Union for Conservation of Nature and Natural Resources as one of the 100 of the world's worst invasive species. Whilst impacts conferred towards native prey are well known, its relationship with other non-native species has received much less attention. Therefore, the aim of this study was to experimentally investigate the feeding preference of M. salmoides towards native prey (Geophagus iporangensis) compared to non-native prey (Oreochromis niloticus and Coptodon rendalli) using comparative consumption and the Manly-Chesson selectivity index. We found a higher consumption by M. salmoides towards the non-native prey and a tendency for this non-native preference to increase when prey availability increased. Our results are in line with the hypothesis that the invasion of the non-native predator can be facilitated by the high abundance and reproductive rate of the non-native prey. This is relevant considering the interaction of multiple invaders in an ecosystem, in particular environments modified by humans. Interspecific relationships are complex and their understanding is necessary for environmental management decision-making. [ABSTRACT FROM AUTHOR]

Carnivora species present specialisations for carnivorous diet, although their dietary spectrum is variable: some are strictly carnivorous, others feed mostly on plants. Knowledge about Carnivora feeding habits and resource use patterns is the basis for understanding ecological dynamics, including their role in ecosystems, trophic interactions and conservation.We aimed to contribute to the identification and description of the trophic guild structure of Carnivora species throughout the Neotropical Region and explore the main drivers behind their structuring.We compiled Carnivora dietary studies and evaluated trophic guild formation through network analysis, diet dissimilarity and overlapping. We investigated whether there is spatial variation in diet parameters and the role of phylogeny in trophic guild structuring.We found dietary studies for 32 species from six Carnivora families. We observed two important biases: most studies focus on large‐bodied felids and canids and were predominantly conducted in South and South‐eastern regions of South America. Additionally, it has been noted that biomes such as the Amazon and Caatinga require further research on dietary studies.The network patterns evidenced that central items in carnivorans' diet are small mammals, plants, arthropods and crustaceans. Modularity suggests grouping generalists/opportunists, marine‐based, plant‐based and two mammal‐based diets. Most opportunistic and generalist species were found within the families Canidae and Procyonidae, while felids were strictly carnivorous.Dietary parameters reveal carnivorans tend to maintain niche breadth regardless of the ecoregion, possibly by substitution of items in their diet. Finally, we observed that phylogeny is an important driver of dietary patterns, indicating that evolutionary history explains part of the habits of carnivores. Our review provides insights to identify broad‐scale patterns and guidelines for new studies. [ABSTRACT FROM AUTHOR]

Human activities have resulted in higher levels of turbidity in aquatic systems due to increased sediment runoff from agriculture, urbanization, and mining activities into nearby water bodies. Previous research has suggested that as turbidity increases, fish may increase their mobility to counteract the reduction in low visual acuity and maintain prey consumption similar to those in clear water. However, other studies have reported negative and non-significant relationships between turbidity and fish mobility. Here, we conducted a systematic review and meta-analysis to investigate the effect of turbidity on fish mobility. We analysed potential sources of variation in the turbidity–fish mobility relationships (moderators), such as body size, eye size and the trophic position of fish, as well as turbidity type, range and ecosystem types, while also accounting for phylogenetic relationships among fish species. Our results revealed that the overall effect size of turbidity on fish mobility was not significantly different from zero, indicating that turbidity does not consistently affect fish mobility. Instead, some fish species may increase their mobility, while others decrease or remain unchanged. Furthermore, the effects of turbidity on fish mobility varied greatly among studies. However, none of the moderators tested explained such variability in the turbidity–fish mobility relationships. These findings demonstrate that the effects of turbidity on fish movements are complex and that some fish species and populations may be particularly vulnerable to increasing turbidity levels in water bodies worldwide caused by human activities. [ABSTRACT FROM AUTHOR]

In this study, we have shown that nutrient input in aquatic ecosystems has different impacts on the various facets of phytoplankton and zooplankton diversity. We designed an experiment with eleven levels of nutrient addition replicated four times. Alpha, beta, and gamma taxonomic and functional diversity indices were calculated based on organisms' occurrences and abundances in each microcosm, among microcosms of the same treatment and for the set microcosms of a same treatment. There was an increase in species richness and a decrease in equitability along the gradient for both groups. Taxonomic beta diversity based on occurrences was positively related to nutrient gradient, but a hump-shaped relationship between nutrient enrichment and beta diversity was observed when abundance data were considered, showing greater variation in species composition at intermediate levels of nutrient. Alpha functional richness increased for both groups, whereas alpha and gamma RaoQ, and gamma functional divergence decreased, indicating that nutrient enrichment promotes functional trait richness, but also the dominance of species. At small spatial scale and at a short period of time, we showed that taxonomic and functional diversities respond in similar ways to nutrient enrichment. We conclude that nutrient input may modify community composition and affect ecological processes overtime. [ABSTRACT FROM AUTHOR]

Guest editors: Verónica Ferreira, Luis Mauricio Bini, Katya E. Kovalenko, Andre A. Padial, Judit Padisák & María de los Ángeles González Sagrario / Aquatic Ecosystem Services Introduction to ecosystem services Millennium Ecosystem Assessment The dependency of human wellbeing from ecological systems has been long recognized. The ecosystem services approach has provided background and motivated international legislation and agreements aiming to halt and reverse ecosystem degradation and biodiversity loss, such as the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES), the UN Decade on Ecosystem Restoration, and the EU Nature Restoration Law. The papers included in this Special Issue, together with reviews on ecosystem services provided by other aquatic ecosystems and organisms (e.g., Barbier et al., [2]; Macadam & Stockan, [25]; Hilt et al., [14]; Riis et al., [37]; Janssen et al., [16]), contribute to highlighting the relevance of these ecosystems and organisms to human wellbeing, and emphasizing the need for their conservation and restoration. This is followed by 6 reviews addressing ecosystem services provided by specific aquatic ecosystems and 12 reviews addressing ecosystem services provided by different groups of aquatic organisms (Table 2). [Extracted from the article]

Functional homogenization can be defined as a simplification of functional communities or species traits over time. The purpose of this review was to summarize the existing quantitative evaluations of functional homogenization (FH) in aquatic ecosystems, as well as to propose a framework to guide future research. Few articles have quantitatively evaluated FH to date. Although FH is an expected pattern in most studies given the anthropogenic impacts of the Anthropocene era, the result depends on the same factors, like temporal and spatial scales and biological groups. Largely, fish were the most investigated, freshwater was the most evaluated ecosystem, and within these, FH patterns were frequently evidenced with relatively lower connectivity, and were usually associated with an increase in generalist non-native species. The poor link between traits and ecosystem functioning in most studies highlights the need for a better definition of functional measurements for several biological groups. We urge standardized monitoring studies and further research in marine and estuarine ecosystems. Studies on cross-taxa effects as well as a better choice of complementary traits should be encouraged. For that, we suggested a framework to serve as a guide for future studies, to better inform the management and conservation of ecosystem services. [ABSTRACT FROM AUTHOR]

Eutrophication is a key threat to aquatic biodiversity around the world, but especially in the Cerrado biome that has undergone intensive land use conversion and fertilizer use. In this study, we investigated how water conditions and different taxonomic and functional indicators of phytoplankton communities responded to eutrophication over time and also identified which of these variables can act as early indicators of eutrophication. We used a mesocosm experiment to simulate shallow lakes and added nutrients to produce eutrophic and oligo-mesotrophic environments. We found that conductivity and turbidity increased with the nutrient enrichment process. Eutrophication did not change species richness; however, it increased the total phytoplankton density and chlorophyll-a concentration and decreased the diversity indices (Shannon–Wiener diversity and Pielou's equitability) over time, for both taxonomic and functional facets. Our results indicate that eutrophication may not have marked effects on the composition of the initially dominant organisms in the short term but does increase the density of certain organisms and exclude rare species and functional groups in eutrophic environments along the time. Furthermore, the diversity indices are more sensitive indicators of eutrophication compared to abiotic indicators and composition of species and functional groups. Therefore, they may be considered reliable early warnings of ecosystem changes. [ABSTRACT FROM AUTHOR]

We described the spatial and temporal dynamics of aquatic macrophytes in a Neotropical coastal estuarine river, and identified the negative effects associated to the presence and dominance of the invasive tanner grass. We compared macrophyte beds along the Guaraguaçu River (South Brazil) over four years, using taxonomic and functional dimensions. Biodiversity descriptors were higher in the driest periods compared to the rainiest, although this difference seems to be decreasing over the studied years. Moreover, the spatial organization of biodiversity and community structure slightly changed over time. Such spatial community stability was highlighted by the dominance of the highly invasive tanner grass. In beds dominated by the invasive species, the biodiversity was reduced. As aquatic macrophytes represent an important group in water bodies, the long-term loss of seasonal differences in community structuring is of concern, mainly regarding its potential to impact other groups and ecosystem functioning. By analysing data from standardized monitoring, we were able to identify a poorly discussed facet of biotic homogenisation—the seasonal homogenisation. We also discussed the impact of massive development of invasive species and its consequences for biodiversity in a Neotropical river of outmost importance for biological conservation. [ABSTRACT FROM AUTHOR]

Host-parasite metacommunities are influenced by a myriad of factors, although little is known about which processes affect this relationship at different scales. Here, we tested how local habitat characteristics and host traits explained the parasite metacommunity of a migratory fish in a large Brazilian river floodplain. The parasite metacommunity structure showed a Clementsian pattern, which indicates a more deterministic assembly pattern, in accordance with partial Redundancy Analysis results. Results indicated that species filtering is the predominant mechanism driving community assembly. Patterns were clearer in the dry season of the floodplain. Environmental determinism seems to explain ectoparasite metacommunities in the dry season, in contrast with endoparasites that were more correlated to host traits. Overall, our results indicated that ectoparasitism is an interaction marked by opportunity, whereas endoparasitism is likely related to host features. Thus, we argue that metacommunity structuring of parasites depends on the infection strategy. Our results show that floodplain dynamics are central not only for free-living animal organizations but also for symbiotic interactions. Here, we highlight the importance of understanding the factors influencing the distribution of parasites to predict their transmission, as well as the importance of floodplain dynamics and its hydrological regime on the maintenance of ecological interactions. [ABSTRACT FROM AUTHOR]

While environmental alterations have made Homo sapiens the hyperkeystone species of the globe, biotic homogenization initiated a new era, the "Homogenocene." Still, some terrestrial and aquatic ecosystems in South America are considered pristine and wild, which can lead to a general faith that economic progress is consistent with conservation strategies, even without scientific support. We compiled anthropogenic threats to fish biodiversity in a hierarchical meta‐analysis, along with an evidence synthesis of threats related to biological invasions, based on peer‐reviewed research with the aim to represent the actual conservation status of the South American ichthyofauna. We highlighted human‐related threats and synergistic effects of biological invasions, climate change, environmental alterations (e.g., pollution, aquaculture and damming) and fisheries. Considering measures that reinforce novel alien fish (e.g., artificial hybrids or genetically modified) introductions, it became clear why an eventual increase in local or regional species richness is not always beneficial to aquaculture, biodiversity, human well‐being or nature. In fact, citizens in all societal roles, including scientists, should revise their concepts about threats to fish biodiversity. Environmental policies require more than taxonomic diagnostics to achieve conservation goals under an incompatible scenario of a multiplying number of fish species and biotic homogenization. We advocate for countries in South America using science‐based strategies useful to maintain their social and economic growth along with their "remaining nature." We live a crucial moment when the government overlooks threats to biodiversity and uses agribusiness as the most acceptable manner of fuelling the economy. [ABSTRACT FROM AUTHOR]