Paleolimnological records reveal biotic homogenization driven by eutrophication in tropical reservoirs

Author(s)

Wengrat, Simone ; Padial, Andre A. ; Jeppesen, Erik ; Davidson, Thomas A. ; Fontana, Luciane ; Costa-Boeddeker, Sandra ; Bicudo, Denise C.

• Document type: Journal article
• Source: JOURNAL OF PALEOLIMNOLOGY; v. 60, n. 2, p. 11-pg., 2018-08-01.

Abstract

Biodiversity changes in response to eutrophication, climate variability and species invasions. These pressures have been shown to reduce community heterogeneity at various scales; however, how productivity drives homogenization patterns in a community of primary producers, such as diatoms, has not been studied. Using a dataset with good temporal resolution, obtained from cores collected from seven tropical reservoirs, we evaluated patterns of spatial and temporal homogenization, i.e. the trends in temporal alpha-diversity and spatial beta-diversity (change in community composition), of diatom assemblages over the past 60-100 years. The paleolimnological records allowed us to study biodiversity trends since the initial community (reservoir construction) in those systems with low anthropogenic impact and also those undergoing eutrophication. No clear trend of spatial beta-diversity change over time was found when all reservoirs were analyzed together. However, when only eutrophic reservoirs were considered, a marked decrease in the spatial beta-diversity occurred, suggesting that eutrophication leads to homogenization of the diatom assemblage. These findings were reinforced by the lack of change in beta-diversity when the age of the reservoirs was standardized, indicating that the reservoirs' ontogeny did not influence the spatial beta-diversity trend and beta-diversity did not increase even in the reservoirs with low anthropogenic impact. In addition, the results showed a decrease of alpha-diversity over time for almost all the eutrophic reservoirs, as well as a decrease in the total species pool for the reservoirs, although periphytic diatoms may be favored by the appearance and sometimes mass development of floating macrophytes in warm, shallow eutrophic reservoirs. This study supports the role of eutrophication as one of the main drivers of diatom assemblage homogenization in tropical reservoirs, with a significant loss of species over time. (AU)

• FAPESP's process: 12/25366-5 - Shifts in present-day and pre-eutrophic diatom assemblages in reservoirs of different trophic status (Upper Tietê River and surrounding drainage basins)
• Grantee: Simone Wengrat
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 09/53898-9 - Paleolimnological reconstruction of Guarapiranga Reservoir and diagnosis of water and sediment current quality of SPMR water supply reservoirs facing their management
• Grantee: Carlos Eduardo de Mattos Bicudo
• Support Opportunities: Research Projects - Thematic Grants