Description: Arctica islandica is the longest-lived non-colonial animal found so far, and reaches individual ages of 150years in the German Bight (GB) and more than 350years around Iceland (IC). Frequent burrowing and physiological adjustments to low tissue oxygenation in the burrowed state are proposed to lower mitochondrial reactive oxygen species (ROS) formation. We investigated burrowing patterns and shell water partial pressure of oxygen (PO2) in experiments with live A. islandica. Furthermore, succinate accumulation and antioxidant defences were recorded in tissues of bivalves in the normoxic or metabolically downregulated state, as well as ROS formation in isolated gills exposed to normoxia, hypoxia and hypoxia/ reoxygenation. IC bivalves burrowed more frequently and deeper in winter than in summer under in situ conditions, and both IC and GB bivalves remained burrowed for between 1 and 6days in laboratory experiments. Shell water PO2 was 〈5kPa when bivalves were maintained in fully oxygenated seawater, and ventilation increased before animals entered the state of metabolic depression. Succinate did not accumulate upon spontaneous shell closure, although shell water PO2 was 0kPa for over 24h. A ROS burst was absent in isolated gills during hypoxia/reoxygenation, and antioxidant enzyme activities were not enhanced in metabolically depressed clams compared with normally respiring clams. Postponing the onset of anaerobiosis in the burrowed state and under hypoxic exposure presumably limits the need for elevated recovery respiration upon surfacing and oxidative stress during reoxygenation.

Description: Human-induced habitat destruction, overexploitation, introduction of alien species and climate change are causing species to go extinct at unprecedented rates, from local to global scales. There are growing concerns that these kinds of disturbances alter important functions of ecosystems. Our current understanding is that key parameters of a community (e.g. its functional diversity, species composition, and presence/absence of vulnerable species) reflect an ecological network’s ability to resist or rebound from change in response to pressures and disturbances, such as species loss. If the food web structure is relatively simple, we can analyse the roles of different species interactions in determining how environmental impacts translate into species loss. However, when ecosystems harbour species-rich communities, as is the case in most natural systems, then the complex network of ecological interactions makes it a far more challenging task to perceive how species’ functional roles influence the consequences of species loss. One approach to deal with such complexity is to focus on the functional traits of species in order to identify their respective roles: for instance, large species seem to be more susceptible to extinction than smaller species. Here, we introduce and analyse the marine food web from the high Antarctic Weddell Sea Shelf to illustrate the role of species traits in relation to network robustness of this complex food web. Our approach was threefold: firstly, we applied a new classification system to all species, grouping them by traits other than body size; secondly, we tested the relationship between body size and food web parameters within and across these groups and finally, we calculated food web robustness. We addressed questions regarding (i) patterns of species functional/trophic roles, (ii) relationships between species functional roles and body size and (iii) the role of species body size in terms of network robustness. Our results show that when analyzing relationships between trophic structure, body size and network structure, the diversity of predatory species types needs to be considered in future studies.

Description: The Magellan region at the southern tip of South America constitutes the southernmost outpost of Atlantic as well as Pacific shelf and coastal ecosystems. This region may be the beachhead of a forthcoming invasion of Antarctic ecosystems by northerly species which will profit from the climate change driven warming of Antarctic waters. Thus, the current state of Magellan coastal and shelf ecosystems and the way they differ from their Antarctic counterparts is of general interest. Previous comparisons of benthic community biomass and productivity between Magellan and Antarctic shelf areas indicated lower biomass but higher production in the Magellan area. The main objective of the present study is to extend this comparison in terms of spatial coverage (73 stations in the Magellan region and 232 stations in the Antarctic), and to examine the role of major environmental parameters for benthic distribution patterns at either side of the Antarctic circumpolar current.

Description: The synergistic effects of ocean acidification (OA) and warming were studied on the king scallop (= great scallop; Pecten maximus, L.), an actively swimming calcifier. Metabolic activity and survival success were investigated on the organismic level using oxygen measurements and force recordings during routine metabolism and swimming activity (escape response), respectively. Experiments on P. maximus sampled during winter from Stavanger (Norway) incubated at 4°C and at 10°C for 6-8 weeks at CO2 levels of around 0.039 and 0.112 kPa (390 and 1120 ppm) in re-circulated systems suggest that OA alone has only an marginal impact on routine metabolism and escape response of the scallops. However, we found a significant reduction in both force production and on the quotient of exhausted exercise metabolism to routine metabolism (factorial aerobic scope) in the group incubated under elevated temperature and high CO2 conditions. Hemolymph data revealed, that exhausted animals had significant less oxygen and more CO2 in their hemolymph compared to animals under routine conditions. Scallops incubated at 0.039 kPa had less CO2 in their hemolymph compared to animals at high CO2 conditions. Our data support the hypothesis of Pörtner and Farrell (Science, 2008) that increased CO2 concentrations will effect thermal tolerance of scallops by narrowing the “window” of optimal life conditions.