Gold mining changes composition, habitat correlates and morphological attributes of an endemic fish assemblage in the Guiana Shield highlands, Guyana, South America

Background/Question/Methods

Habitat alteration through human impacts such as mining can drive changes in community composition and potential loss of ecological function. The upper Mazaruni River in Guyana, South America, houses a relatively depauperate fish fauna with a unique composition that may reach 95% endemism and is facing increasing pressure from gold mining. We performed standardized fish and habitat sampling in 54 localities in the upper Mazaruni basin, including both mined and pristine sites, and used geometric morphometrics to generate community ecomorphospace representations at each site. We used Canonical Correspondence Analysis (CCA) to estimate associations between species relative abundance and habitat attributes as indicators of species habitat preferences. We compare community morphospace among sites using trait-based metrics as indicators of possible changes of ecological function between mined and pristine sites.

Results/Conclusions

CCA results indicate strong affinity between habitat attributes and species. Particularly, two type of assemblies are recognizable: 1) assemblies in the large channels dominated by fishes with preference for moderate current, deep water and relatively open riparian vegetation, and 2) assemblies in smaller tributaries with fishes preferring faster, shallower water with highly structured habitats and denser riparian coverage. Mined sites generally displayed much higher turbidity and included unstructured, artificially generated “tailings” beaches for which no fish species showed strong affinity. We find that mined areas exhibit significantly changed community composition when compared to pristine sites. This suggests there may be changes in functional diversity reflected by changes in community morphospace across sites.