Are freshwater turtles macro-epibionts indicators of water quality of the streams where the turtles live?

Abstract

Organisms that live above others can give information not only about therelation between them but also about the environment they inhabit. In that sense, thiswork studies the relationship between epibionts living on freshwater turtles and theimpact degree of streams where they live. We studied the macro-epibiont assemblagesand algal and epipelic biofilm covers in two species of freshwater turtles withcontrasting habits (the bottom-dwelling-aquatic basking Hydromedusa tectifera andthe swimming-aerial basking Phrynops hilarii), from streams with different types anddegrees of anthropogenic impact. Algal and epipelic biofilm covers and animal epibiontassemblages were, in most cases, greater in H. tectifera than in P. hilarii. In general, turtlesfrom polluted streams had higher algal and epipelic biofilm covers and poorer epibiontassemblages with low abundance of sensible species. Our results also highlighted akey mutualistic relationship between H. tectifera and Temnocephala brevicornis, forwhich this turtle is the main host. We provide insights for using this biological unit tomonitor water quality, particularly in low impacted streams where temnocephalans offermodulate responses, useful to early detection of pollution.