Effects of spatially heterogeneous lakeside development on nearshore biotic communities in a large, deep, oligotrophic lake

Sewage released from lakeside development can reshape ecological communities. Nearshore periphyton rapidly assimilate sewage-associated nutrients, leading to increases of filamentous algal abundance, thus altering both food abundance and quality for grazers. In Lake Baikal, a large, ultra-oligotrophic, remote lake in Siberia, has increased near developments, localized sewage input is the suspected cause. These shifts are particular interest where endemic littoral biodiversity high, settlements mostly small, tourism relatively high (~1.2 million visitors annually), separated by large tracts undisturbed shoreline, enabling investigation heterogeneity gradients disturbance. We surveyed sites along 40 km Baikal's southwestern shore indicators—pharmaceuticals personal care products (PPCPs) microplastics—as well as macroinvertebrate indicators web structure (stable isotopes fatty acids). Summed PPCP concentrations were spatially related development. As predicted, was associated with more algae lower sewage-sensitive mollusks. Periphyton stable essential acids suggested that otherwise remained similar across sites; yet, invariance amphipod acid composition, relative periphyton, grazers adjust behavior or metabolism compensate different assemblages. Our results demonstrate even low levels human disturbance result spatial nearshore responses, potential changing trophic interactions propagate through web.