Climate change is affecting coastal environments. Increased global temperature, heat wave intensity, and related effects add to human-made and natural stressors like contaminants and predation stress. Marine invertebrates are often exposed to excess copper, which can have subtle and drastic effects on non-target organisms. Predation risk affects population dynamics and can also interfere with copper responses.  In the lab, predation risk potentiates copper effects on delayed development in the splash pool copepod <em>Tigriopus brevicornis</em>. Here we tested these stressors in a realistic field setting by exposing outdoor mesocosms to predation risk, copper, a combination of both, and a control. Monthly, we counted copepods and other inhabitants. We also quantified the copepod population’s stage composition and measured their size, stable isotope composition, and astaxanthin concentration. Astaxanthin is an antioxidant that reduces the impact of copper but can increase visual predation risk. Despite extreme conditions, with daily temperature fluctuations up to 25°C, peaks of 50°C, and salinities over 120, copper and predation risk reduced the population size of the surviving copepods, especially under combined stress. We could not find any difference in their pigmentation or isotope signature. Chironomidae and Ephydridae, which naturally populated the pools, were unfazed by the treatments. While physical stressors pose an immediate threat to populations, the interaction of anthropogenic and natural stressors can increase populations’ vulnerability even further.

Primary Presenter: Jan Heuschele, University of Oslo (janheuschele@gmail.com)

Authors:

Jan Heuschele, University of Oslo  (janheu@uio.no)

Torben Lode, University of Oslo  (torben.lode@ibv.uio.no)

Hilde Bruserud, University of Oslo  (hildbrus@student.ibv.uio.no)

Trym Dingstad, University of Oslo  (trymrd.98@gmail.com)

Solveig Brochmann, University of Oslo  (solvebro@student.ibv.uio.no)

Raoul Wolf, Norwegian Geotechnical Institute, Oslo, Norway  (raoul.wolf@ngi.no)

Katrine Borgå, University of Oslo  (katrine.borga@ibv.uio.no)