Description: The relatively small numbers of pelagic cephalopods caught in the RMT-8 samples (0–300 m) in February/March 1983 in the Weddell Sea were dominated by early life stages of the cranchiid squid Galiteuthis glacialis. A total of 48 specimens were caught with dorsal mantle length (ML) ranging from 4–36 mm. They occurred with a mean density of 0.15 ind. × 1000 m−3 and were present in 38% of 33 RMT-8 samples. G. glacialis was the only cranchiid squid found in the Weddell Sea between 66° and 74°S. Its early life stages were concentrated in the layers below the summer thermocline (〉50 m) and body sizes appeared to increase towards deeper water layers. For biochemical analyses, nine specimens of G. glacialis (ML 6–18 mm) were sampled in the eastern Weddell Sea between 185–520 m water depth in January/February 1985. Total lipid contents ranged from 8%–11% dry weight (DW) with phospholipids being the main lipid component (43–56% of total lipid). Storage lipids (triacylglycerols) made up 18–26% of total lipid. The relatively low lipid contents may reflect the early development stage of the specimens examined. The data presented give the first information on geographical and vertical distribution patterns of early life stages of G. glacialis in the high-Antarctic Weddell Sea, as well as on their lipid content and composition.

Description: Seasonal activities of the digestive enzyme trypsin were measured between August 1998 and May 1999 to study different nutritional strategies of the two copepods Pseudocalanus minutus and Oithona similis in the Arctic Kongsfjorden (Svalbard) using a highly sensitive fluorescence technique. Stage-, depth- and season-specific characteristics of digestive activity were reflected in the trypsin activity. P. minutus females and stage V copepodids (C) had highest trypsin activities in spring during reproduction (197.5 and 145.7 nmol min−1 ng C−1, respectively). In summer stages CIII–V and in autumn stages CIV and V had high activities (80–116 nmol min−1 ng C−1) in the shallow layer (〈 100 m) presumably as a consequence of prolonged feeding before descending to overwintering depth. Trypsin activities at depth (〉 100 m) in summer and autumn were low in stages CIII and CIV (29–60 nmol min−1 ng C−1) and in winter in all stages in both layers (20–43 nmol min−1 ng C−1). Based on low trypsin activity, males most likely did not feed. In O. similis, the spring phytoplankton bloom did not significantly affect trypsin activity as compared to the other seasons. O. similis CV and females had high trypsin activities in summer in the deep stratum (304.5 nmol min−1 ng C−1), which was concomitant with reproductive processes and energy storage for overwintering. In autumn, stage CV and female O. similis had significantly higher activities than stage CIV (130–152 versus 78 nmol min−1 ng C−1), which is in accordance with still ongoing developmental and reproductive processes in CVs and females. Comparisons of both species revealed different depth-related responses emphasizing different nutritional preferences: the mainly herbivorous P. minutus is more actively feeding in the shallow layer, where primary production occurs, whereas the omnivorous O. similis is not as much restricted to a certain depth layer, when searching for food. P. minutus had lower levels of trypsin activity during all seasons. In contrast to P. minutus, higher enzyme activities in males of O. similis suggest that they continue to feed and survive after fertilization of females.

Description: Seasonal lipid dynamics of various developmental stages were investigated in Pseudocalanus minutus and Oithona similis. For P. minutus, the dominance of 16:1(n−7), 16:4(n−3) and 20:5(n−3) fatty acids indicated a diatom-based nutrition in spring, whereas 22:6(n−3), 16:0, 18:2(n−6) and 18:1(n−9) pointed to a flagellate-based diet during the rest of the year as well as omnivorous/carnivorous low-level feeding during winter. The shorter-chain fatty alcohols 14:0 and 16:0 prevailed, also reflecting biosynthetic processes typical of omnivores or carnivores. Altogether, the lipid signatures characterized P. minutus as an opportunistic feeder. In contrast, O. similis had consistently high amounts of the 18:1(n−9) fatty acid in all stages and during all seasons pointing to a generally omnivorous/carnivorous/detritivorous diet. Furthermore, the fatty alcohol 20:1(n−9) reached high percentages especially in adult females and males, and feeding on Calanus faecal pellets is suggested. Fatty alcohols, as wax ester moieties, revealed significant seasonal variations in O. similis and a seasonal trend towards wax ester accumulation in autumn in P. minutus. P. minutus utilized its lipid deposits for development in the copepodite stages III and IV and for gonad maturation in CV and females during the dark season. However, CVs and females depended on the spring phytoplankton bloom for final maturation processes and reproduction. O. similis fueled gonad maturation and egg production for reproduction in June by wax esters, whereas reproduction in August/September co-occurred with the accumulation of new depot lipids. Both species revealed significantly higher wax ester levels in deeper (〉50 m) as compared to surface (0–50 m) dwelling individuals related to a descent prior to overwintering.

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.