Open Access

Zoran Sargac

• Under the influence of human activities, increased climate variability induces changes in multiple marine environments. Especially vulnerable are the coastal ecosystems where organisms must cope with constant extreme changes of environmental drivers, such as temperature, salinity, pH, and oxygen content. In coastal areas, brachyuran crabs are important animals that have a high impact on ecosystem functioning and serve as a link in food webs and pelagic-benthic coupling. Larval stages of crabs are crucial for population persistence and dispersal. They are generally more vulnerable to changes of environmental drivers and failure to adapt to new conditions may result in population collapse. To analyse the effects of multiple environmental drivers on larval performance and to elucidate interspecific and intraspecific difference, this project examined larval performance in the European shore crab Carcinus maenas. In this study, larvae of C. maenas from three native populations (Cádiz: Cádiz Bay, Helgoland: North Sea, Kerteminde: Baltic Sea) were reared in a factorial design consisting of different temperature (15-24 °C) and salinity treatments (20, 25, 32.5 PSU). Results demonstrated how descriptors of larval performance (growth, physiological, and developmental rates, and survival) were affected by combined environmental drivers. Larval responses to temperature and salinity showed contrasting patterns and differed among native populations originating from distant or contrasting habitats, as well as within the populations. The highest overall performance was recorded in the Cádiz population, while the Kerteminde population had the lowest performance in most of tested traits. The interactive effects of multiple drivers differed among the populations. In the Cádiz and Helgoland populations, higher temperatures mitigated the effect of lower salinity while the Kerteminde population showed a maladaptive response when exposed to lower salinity. Differences in performance showed better locally adapted populations (e.g. Cádiz) that could acclimate faster, have better adaptive mechanisms or stronger dispersive abilities. Because of their wider tolerance to increased temperature and decreased salinity, interactive effects in particular populations may favour some populations in a changing climate, especially in coastal habitats. Variation in larval performance showed complex interactions in larval performance and highlighted the necessity to quantify inter-population responses to climate-driven environmental change where responses of species should not be generalised. This study emphasizes the need for inclusion of multiple traits, drivers, and populations in experimental studies to properly characterize performance of marine coastal animals.