Description: Respiration rates and electron transport system (ETS) activities were measured in dominant copepod species from the northern Benguela upwelling system in January-February 2011 to assess the accuracy of the ETS assay in predicting in vivo respiration rates. Individual respiration rates varied from 0.06 to 1.60 µL O2/h/ind, while ETS activities converted to oxygen consumption ranged from 0.14 to 4.46 µL O2/h/ind. ETS activities were significantly correlated with respiration rates (r**2 = 0.79, p = 0.0001). R:ETS ratios were lowest in slow-moving Eucalanidae (0.11) and highest in diapausing Calanoides carinatus copepodids CV (0.76) while fast-moving copepods showed intermediate R:ETS (0.23-0.37). 82% of the variance of respiration rates could be explained by differences in dry mass, temperature and the activity level of different copepod species. Three regression equations were derived to calculate respiration rates for diapausing, slow- and fast-moving copepods, respectively, based on parameters such as body mass and temperature. Thus, knowledge about the activity level and behavioral characteristics of copepod species can significantly increase the predictive accuracy of metabolic models, which will help to better understand and quantify the impact of copepods on nutrient and carbon fluxes in marine ecosystems.

Description: Respiration rates of 16 calanoid copepod species from the northern Benguela upwelling system were measured on board RRS Discovery in September/October 2010 to determine their energy requirements and assess their significance in the carbon cycle. Individual respiration rates were standardised to a mean copepod body mass and a temperature regime typical of the northern Benguela Current. These adjusted respiration rates revealed two different activity levels (active and resting) in copepodids C5 of Calanoides carinatus and females of Rhincalanus nasutus, which reduced their metabolism during dormancy by 82% and 62%, respectively. An allometric function (Imax) and an energy budget approach were performed to calculate ingestion rates. Imax generally overestimated the ingestion rates derived from the energy budget approach by 〉75%. We suggest that the energy budget approach is the more reliable approximation with a total calanoid copepod (mainly females) consumption of 78 mg C m-2 d-1 in neritic regions and 21 mg C m-2 d-1 in oceanic regions. The two primarily herbivorous copepods C. carinatus (neritic) and Nannocalanus minor (oceanic) contributed 83% and 5%, respectively, to total consumption by calanoid copepods. Locally, C. carinatus can remove up to 90% of the diatom biomass daily. In contrast, the maximum daily removal of dinoflagellate biomass by N. minor was 9%. These estimates imply that C. carinatus is an important primary consumers in the neritic province of the northern Benguela system, while N. minor has little grazing impact on phytoplankton populations further offshore. Data on energy requirements and total consumption rates of dominant calanoid copepods of this study are essential for the development of realistic carbon budgets and food-web models for the northern Benguela upwelling system.

Description: Total lipids, lipid class and fatty acid compositions were studied to elucidate their role in the life cycle strategies of the Antarctic silverfish Pleuragramma antarcticum, one of the few truly pelagic fish species in the Antarctic realm. Various size groups (larvae to juveniles, 10-105 mm length) of this notothenioid fish have been collected in the southern Weddell Sea during different seasons (mainly spring: October/November and summer: January/February). Total lipid data of P. antarcticum revealed little variation between the seasons. Lipid levels were largely determined by the developmental stage and size, with lower lipid levels (〈20% of dry mass DM) found in the larvae (10-16 mm) and intermediate concentrations in the younger juveniles, which increased strongly to maximum amounts of lipid (〉40%DM) in the older juveniles (〉55-105 mm). Lipid class composition was clearly related to total lipid levels, with neutral lipids (triacylglycerols) comprising 〈20% of total lipid (%TL) in the younger lipid-poor specimens and 〉65%TL in the older lipid-rich fishes. Triacylglycerols and phospholipids showed an inverse relationship. Hence, the relative importance of these polar lipids, typically components of biomembranes, decreased with increasing lipid and triacylglycerol levels. Principal fatty acids were 14:0, 16:0, 18:1(n-9), 18:1(n-7), 20:5(n-3) and 22:6(n-3). Elevated portions of the long-chain mono¬unsaturated fatty acids, 20:1 and 22:1, in the lipid-rich specimens suggest the ingestion of two dominant calanoid copepod species, the wax ester-rich Calanoides acutus and the triacylglycerol-rich Calanus propinquus. They are the only species known to biosynthesize larger amounts of these monounsaturated compounds in high-Antarctic waters, which may therefore serve as dietary marker fatty acids for higher trophic levels. Apparently, wax ester moieties (fatty acids and alcohols) ingested with prey, e.g. copepods, are converted to triacylglycerols via fatty acids or metabolized by P. antarcticum. We discuss the function of these high-energy and low-density lipid compounds as energy reserve and/or buoyancy aid in this swimbladderless fish species.

Description: The aim of this study was to determine the macro-parasitic infestation level of oysters from the southern German Bight focussing on copepods of the genus Mytilicola. Crassostrea gigas, Ostrea edulis and Mytilus edulis were collected at five locations: three nearshore sites in the eastern Wadden Sea and two offshore cultivation sites in the German Bight. To reveal seasonal variations one sampling site was investigated in winter and summer. At the nearshore sites, Mytilicola orientalis was regularly detected in C. gigas. Prevalences ranged between 32.3% and 45.1%, intensity between 3.0 ± 0.6 and 8.2 ± 1.5. Infestation rates of C. gigas within the southern German Bight decreased from west to east: Apparently, M. orientalis has started its range extension along the German coast with gradual retardation eastwards but generally followed the invasion route of its main host, the Pacific oyster. Interestingly, we detected not only M. intestinalis but also M. orientalis as an intestinal parasite in M. edulis, which has sofar not previously been described as host within this region. We conclude that M. orientalis is flexible in its host choice. Furthermore, in the eastern Wadden Sea infestation rates of oysters and mussels by copepods are similar. These results deviate from the patterns observed for the northern Wadden Sea in terms of infestation level and host specificity. No macro-parasites were found in oysters and mussels from the offshore sites. This absence can be considered as potentially beneficial for aquaculture activities in the open ocean in terms of stamina and physiological performance.

Description: Antarctic and Arctic zooplankton species have developed very similar life strategies and energetic adaptations to the harsh environment via sophisticated modes of lipid accumulation. A very efficient biosynthesis, storage and utilization of lipids enable especially herbivorous species to buffer the pronounced seasonality of food supply in the polar oceans. Lipid levels usually peak at the end of the productive season in autumn and reach minimum levels in spring. In many species lipid deposits are not primarily used for maintenance during winter but are conserved to fuel reproductive processes at the end of the dark season. The dependence on seasonal primary production is also reflected by the respective lipid compositions. Detailed lipid analyses of dominant Antarctic and Arctic copepods revealed that the herbivorous Calanus and Calanoides species have developed the most complex lipid biochemical pathways. They biosynthesise large amounts of wax esters with long-chain monounsaturated fatty acids and alcohols (20:1, 22:1) as major components. In contrast, the Antarctic Calanus propinquus and C. simillimus synthesise primarily triacylglycerols consisting mainly of long-chain monounsaturated fatty acids with 22 and even 24 carbon atoms (2 major isomers), which is very unusual among plankton species. In contrast, the lipids of omnivorous and carnivorous taxa such as Metridia or Euchaeta are deficient in such long-chain fatty acids and alcohols, although their lipid reserves mainly consist of wax esters. Our investigations underscore that lipids are a key factor in high latitude ecosystems, especially for the lower trophic levels. The extremely lipid-rich herbivorous species ensure an efficient lipid-based energy transfer and represent high-calory food for fish and warm-blooded animals like birds and mammals.