Limnetica 34

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Fish community in a large coastal subtropical lake: how an environmental gradient may affect the structure of trophic guilds

Lúcia Ribeiro Rodrigues, David da Motta Marques & Nelson Ferreira Fontoura
2015
34
2
495-506
DOI: 
10.23818/limn.34.37

Biological communities change in time and space under driving pressures from differences in habitat structure, resource availability, interspecific competition, predation and other factors. Spatial heterogeneity, or patchiness, has been recognized as an important feature in a number of lake systems. In this study, we analysed changes in the seasonal dynamics of fish community in a subtropical lake over one year, focusing on the spatial and temporal distribution of fish biomass and species composition. Mangueira is a large shallow lake (3 m deep in average, 90 km long, 3-10 km wide,  820 km2) located along the Atlantic coast-line in southern Brazil (33º31’22”S 53º07’48”W). Mangueira Lake presents longitudinal gradients in both biotic and abiotic factors, and a principal components analysis (PCA) showed temporal and spatial gradients in the system. Analysis of similarity (ANOSIM) showed significant differences between the north and south extremes of Mangueira Lake. Secchi transparency (p < 0.001), dissolved organic carbon (DOC) (p = 0.03) and chlorophyll a (p < 0.001) were identified as the driving factors for this spatial gradient. A two-way ANOVA was adjusted for each data set. Chlorophyll a (p = 0.017), fish captures (p = 0.033) and fish richness (p = 0.026) were different according to the sampling site (after removing the seasonal effect), while only fish richness presented significant seasonal variation after removing the sampling site effect (p = 0.041). This longitudinal gradient can be related to two main driving pressures. The first is prevailing winds from northeast to southwest, with predictable consequences for the whole trophic cascade. The other structuring pressure is the interface of the Taim wetland with northern Mangueira Lake. Thus, the northern part presents more turbid water, muddy sediments and increased chlorophyll a concentration, while the southern part is characterized by increased water transparency, less chlorophyll a concentration and more PVI (percent volume infested) of submerged macrophytes, demonstrating the spatial heterogeneity of the ecosystem.

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