Invasion of common carp (Cyprinus carpio) reduces the quality of bottom sediments in shallow lakes

Species invasions are one of the main anthropogenic forces reshaping ecological structure and function in lakes during the 21st century. Common carp (Cyprinus carpio) are among the most globally widespread and damaging aquatic invasive species, with the capacity to significantly alter lake ecosystems. While it is well documented that carp feeding activity can disturb sediments, decrease water quality, and reduce macrophyte and fish diversity, less is known about how carp influence sediment chemistry and nutrient cycling. Here, we examined the effect of carp invasion on sediment phosphorus (P) dynamics and organic matter quality in shallow lakes. We compared P fractions in sediments of lakes with established carp populations and those from carp-free reference lakes. We found that lakes with carp had depleted surficial sediments, with significantly lower organic P (0.16 vs. 0.41 mg g^-1) and higher C/P ratios (972 vs. 639) than lakes without carp. Carp lakes had higher concentrations of water-column total P (370 vs. 160 μg L^-1), though a mass balance between sediment labile P and water-column P was similar for lakes with and without carp, indicating sediment P loss due to carp is largely kept in the water column. Sediments are a crucial component of lake ecosystems, and a reduction in sediment organic matter quality by invasive carp can alter food web dynamics and geochemical processes in invaded lakes.