Abstract
To understand the effects of predicted warming and changing salinity of marine ecosystems, it is important to have a good knowledge of species vulnerability and their capacity to adapt to environmental changes. In spring and autumn of 2014, we conducted common garden experiments to investigate how different populations of the copepod Eurytemora affinis from the Baltic Sea respond to varying temperatures and salinity conditions. Copepods were collected in the Stockholm archipelago, Bothnian Bay, and Gulf of Riga (latitude, longitude: 58°48.19′, 17°37.52′; 65°10.14′, 23°14.41′; 58°21.67′, 24°30.83′). Using individuals with known family structure, we investigated within population variation of the reaction norm (genotype and salinity interaction) as a means to measure adaptive capacity. Our main finding was that low salinity has a detrimental effect on development time, the additive effects of high temperature and low salinity have a negative effect on survival, and their interaction has a negative effect on hatching success. We observed no variation in survival and development within populations, and all genotypes had similar reaction norms with higher survival and faster development in higher salinities. This suggests that there is no single genotype that performs better in low salinity or high salinity; instead, the best genotype in any given salinity is best in all salinities. Genotypes with fast development time also had higher survival compared to slow developing genotypes at all salinities. Our results suggest that E. affinis can tolerate close to freshwater conditions also in high temperatures, but with a significant reduction in fitness.
Highlights
Climate change is affecting biodiversity of marine organisms, and in coastal estuarine ecosystems like the Baltic Sea that will experience some of the greatest changes in temperature and salinity (Lehmann et al 2011; Meier et al 2006)
One population was collected in October 2013 from the Stockholm archipelago at the Askö monitoring station B1 (STHLM) (58°48.19′, 17°37.52′); the other two populations were collected in August and September 2014 from Pärnu Bay in the Gulf of Riga (GOR) (58°21.67′, 24°30.83′) and monitoring station F3A5 in the Bothnian Bay (BB) (65°10.14′, 23°14.41′)
Our study reveals how clutch size, hatching success, development time, and survival are affected by changing temperature, salinity, and their interactions in different populations of the calanoid copepod E. affinis sampled along the Baltic Sea salinity and temperature gradient
Summary
Climate change is affecting biodiversity of marine organisms, and in coastal estuarine ecosystems like the Baltic Sea that will experience some of the greatest changes in temperature and salinity (Lehmann et al 2011; Meier et al 2006). Grow, and reproduce under climate change, organisms have to adapt to the new environmental conditions (Davis and Shaw 2001) or migrate to new habitable areas (Parmesan 2006). Due to taxon-specific tolerance limits, it is difficult to predict how species will cope and interact with environmental changes. A good knowledge of adaptive capacity and tolerance limits of key species can Responsible Editor: A.
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