Description: The intertidal Asian shore crab H. sanguineus was initially found on the French coast in the late 1990’s. It rapidly extended its range further north and is now well established in the German Wadden Sea. Recently, it was also found in western Sweden. In its intertidal habitat, it co-occurs with the European green crab C. maenas. The ecophysiology of H. sanguineus is virtually unknown. In this study, the physiological capacities of both species and their potential for intra-guild competition were investigated. We specifically compared the energy deposition and dietary preferences of ovigerous females of both species. Females of both species carrying immature or mature eggs were collected in April, June, August and October 2015 in an intertidal site on the Island of Helgoland, North Sea, Germany. Total lipid levels of midgut glands and eggs were acquired via extraction. Subsequently, fatty acid compositions were determined through gas chromatography. Total lipid levels of H. sanguineus midgut glands were clearly higher than those of C. maenas (40% vs. 10% dry mass, DM). Immature eggs of both species were quite lipid-rich with 30% and 25%DM, respectively. In mature eggs, lipid levels decreased to ~15%DM each. A Principal Component Analysis of the fatty acid compositions of midgut glands and eggs revealed separate clusters for both species. Lipids of C. maenas were characterized more by membrane fatty acids. Fatty acids of C. maenas midgut glands and eggs clustered together. They were largely dominated by carnivory biomarkers. Contrastingly, fatty acids of midgut glands and all eggs of H. sanguineus formed separate clusters and trophic markers indicated a more herbivorous diet. Higher lipid levels and thus more pronounced energy deposition in H. sanguineus midgut glands indicate higher starvation tolerance for females, a potential competitive advantage over C. maenas. Direct food competition, however, seems negligible, as H. sanguineus prefers a more herbivorous diet than C. maenas. Deviating fatty acid compositions among H. sanguineus midgut glands and eggs suggests that this species may represent an income breeder, utilizing energy from both the midgut gland and dietary input. In contrast, most brachyuran crabs are capital breeders, relying exclusively on internal reserves.

Description: In this chapter, the effects of temperature change—as a main aspect of climate change—on marine biodiversity are assessed. Starting from a general discussion of species responses to temperature, the chapter presents how species respond to warming. These responses comprise adaptation and phenotypic plasticity as well as range shifts. The observed range shifts show more rapid shifts at the poleward range edge than at the equator-near edge, which probably reflects more rapid immigration than extinction in a warming world. A third avenue of changing biodiversity is change in species interactions, which can be altered by temporal and spatial shifts in interacting species. We then compare the potential changes in biodiversity to actual trends recently addressed in empirical synthesis work on local marine biodiversity, which lead to conceptual issues in quantifying the degree of biodiversity change. Finally we assess how climate change impacts the protection of marine environments.