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The mangrove bivalves, Anadara tuberculosa and Anadara similis, are pivotal for the Colombian Pacific coast mangrove ecosystems and economies. In this study, the current and future potential distribution of these bivalves is modeled considering climate change. The future models (2030 and 2050) were projected considering the new climate scenarios (SSP1, SSP2, and SSP5) proposed by the IPCC in its sixth report. Our findings reveal areas in the Colombian Pacific coast, notably Nariño, Cauca, southern Valle del Cauca, and Chocó, with high environmental suitability for these bivalves. However, the 2050 projections, especially under the pessimistic SSP5 scenario, indicate potential adverse impacts from climate change. By 2030 and 2050, the species might lean more toward a southwesterly distribution in the Colombian Pacific coast. Climate-induced spatiotemporal mismatches could occur between the bivalves and the mangroves in some areas. These insights are crucial for effective conservation and management strategies for these species.
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Several experimental studies on aquatic plants have reported the prevalence of chemical defense mechanism against herbivory, as opposed to structural, life-forms or other traits. Here, our laboratory feeding experiments and integrative analysis explored the relationship among palatability (fresh or reconstituted plants used as artificial diet) and various chemical/nutritional traits (i.e., contents of dry mass, ash, nitrogen, protein, and phenols) of diverse aquatic plants and their susceptibility to consumption by the generalist gastropod Biomphalaria glabrata. Biomphalaria glabrata consumed all of the assayed aquatic plants in a hierarchical yet generalized way, with the consumption of fresh plants, their reconstituted forms and defensive properties of lipophilic extracts not being significantly correlated with plant physical or chemical traits to determine the feeding preference of the gastropod. Our results do not reveal a prevalence for a specific plant attribute contributing to herbivory. Instead, they indicate that the susceptibility of aquatic plants to generalist consumers is probably related to a combination of their chemical and physical properties, resulting in moderate grazing rates by generalist consumers.
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Intestinal microbiota perform important functions for the health of fishes. Knowing the microbial composition and evaluating the possible effects caused by anthropogenic pollution in the intestinal microbiota of fish populations might represent an important step in defining microbial biomarkers for water pollution. This study evaluated the impact of environmental contamination on the gut microbiota of the livebearer killifish Phalloceros caudimaculatus. The 16S survey using the V4 region of the 16S rRNA gene was used to characterize and compare the microbiota of two P. caudimaculatus populations from streams with different levels of environmental contamination in Rio Grande, RS, Brazil. Twelve bacterial operational taxonomic units (OTUs) (around one-third of the total) were shared between both fish populations. They represent the core microbiota of the gut in this species. The dominant phyla were Protebacteria and Firmicutes, with more than 80% of relative abundance. The dominant genus was Burkholderia with more than 35% of the relative abundance irrespective of the environmental condition. We detected a lower microbial diversity (Shannon index and observed OTUs) in fish from the polluted stream compared to the reference stream. The PERMANOVA analysis showed that the intestinal microbial communities from fish living in the polluted stream were distinct from those found in the reference stream (p < 0.05). Finally, we identified Luteolibacter, Methylocaldum and Rhodobacter genera, which correlated strongly with the polluted stream. These taxa might represent potential microbial biomarkers of exposure to environmental contaminants in the guts of fish. Confirmation of these findings in other polluted environments might allow the development of a microbiota-based screening approach for environmental evaluation in ecotoxicological studies in aquatic ecosystems.
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This study evaluates the potential use of archaeological otoliths of Genidens barbus (Cuvier and Valenciennes) as a tool to study fish behavior and hunter-gatherers procurement strategies on the North Patagonian coast. The studied samples come from the San Antonio archaeological locality dated at ca. 1000-800 14C yr BP (Late Holocene). To assess whether exposure to fire significantly affects the otolith Sr:Ca and Ba:Ca ratios, burned and unburned modern lapilli otoliths have been analyzed by Laser Ablation Inductively Coupled Plasma Mass Spectrometry and no statistically significant differences were found between the results of both treatments. Core-to-edge chemical time series were carried out on ancient otoliths (ca. 1000 14C yr BP) in order to study the fish life history. Three amphidromous patterns were found for ancient samples. The capture environments and seasons inferred by the otolith edge chemistry and marginal increase, respectively, suggest a location in high salinity water (estuary and sea) in summer. Finally, to estimate the size of archaeological fish, a linear regression between total length and otolith length was constructed using 70 modern catfish otoliths. The size variability (358-610 mm) might indicate the use of non-selective capture techniques, probably nets, by hunter-gatherer groups.
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Increased pollution and degradation of water resources and their associated ecosystems has stimulated the development of tools and methodologies to characterize, estimate, predict, and reverse the environmental impact of anthropic effects on water bodies. The Secondary Water Quality Standards (NSCA) adopted in Chile have incorporated the use of bioindicators complementary to physicochemical analyses, in order to determine the ecological condition of lotic and lentic environments. Our research used the "Lake Biotic Index" (LBI) to establish the ecological condition of Lake Rupanco using benthic macroinvertebrates. The results indicated an Oligo-Eubiotic condition for this lake given the high concentration of oxygen and low organic matter content in sediments, in addition to low biogenic potential and good taxa preservation in both the autumn and spring surveys. Features of the ecological condition obtained through the application of the LBI (benthic subsystem) conform to the results of physicochemical and microalgae analyses undertaken previously in Lake Rupanco (pelagic subsystem). Based on these results, we support application of the LBI index as a complementary tool for the integrated management of lentic ecosystems.