Salinity-temperature interaction drives metabolic and energetic changes in an Arctic crustacean

The Arctic is shifting towards a prevalence of warm and more saline
Atlantic-like waters. These changes in the marine environment pose
significant challenges for the eco-physiology of marine invertebrates.
Here we measured the metabolic enzyme activity of citrate synthase and
lactate dehydrogenase, as well as the energy content and level of
oxidative damage in 71 individuals (~ 10/station) of Thysanoessa inermis
collected in six fjords in Svalbard that were characterized by different
levels of influence of Atlantic water and, thus, temperature and salinity
variability in the water column. T. inermis inhabiting fjords with strong
influence of Atlantic water masses had lower lipid and protein content,
and higher anaerobic metabolism compared to those from more Arctic fjord
types. Moreover, T. inermis collected in fjords with high variability in
both temperature and salinity had 0.8-fold lower lipid content than
station with more stable temperature and salinity. Our results suggest
that T. inermis in fjords influenced by Atlantic waters is possibly under
stress leading to increased metabolism, consequently enhancing energy
consumption. If the energy consumption is not compensated for, by an
uptake, it could result in a decrease of total biomass of T. inermis with
possible consequences for the entire Arctic food web.