Krill vs salps: dominance shift from krill to salps is associated with higher dissolved N:P ratios
The aim of this study is to elucidate the potential relation between changes in macrozooplankton (krill vs. salps) densities and the nutrient dynamics at the WAP. We therefore analyzed the Palmer LTER data set by testing for the correlation between krill and salp density and the dissolved N and P pool, using a linear mixed effects model approach. The outcome of this model indicated that an increasing salp:krill ratio is significantly associated with higher dissolved N: P. In order to assess the potential mechanisms behind this pattern, we further conducted a field survey aboard the RV Polarstern in austral fall 2018, as well as laboratory experiments manipulating the presence of krill and salps in a plankton community. Preliminary results from the experiments revealed a significant impact of krill and salps on N and P recycling, resulting in higher dissolved N:P ratios in the presence of salps.
Our study demonstrates the importance of a comprehensive assessment of plankton community structure and biogeochemistry in order to predict how future changes in the composition of key species might modify stoichiometric dynamics in the planktonic food web of the WAP.