Beschreibung: Abundance, distribution, population structure, lipid content, lipid composition and reproductive and feeding activity of Rhincalanus nasutus were studied in the Gulf of Aqaba and in the northern Red Sea during RV “Meteor”-cruise M 44-2 in February/March 1999. Rhincalanus nasutus occurred in higher numbers in the Gulf of Aqaba (585 ind m−2) than in the northern Red Sea (254 ind m−2). Young developmental stages (nauplii, copepodite stages CI and CII) were absent. In the southern Gulf of Aqaba, the bulk of the population developed from stage CV to adult in the course of the 3-week study period. In contrast, immature CV stages dominated at the adjacent stations in the northern Gulf of Aqaba and in the northern Red Sea. Development was associated with the seasonal vertical migration from wintering mid-water layers and initiation of feeding starting as early as beginning of March in the southern Gulf of Aqaba. No upward migration was observed in the northern parts of the Gulf and in the northern Red Sea, where more than 90% of the females remained immature during our study. Lipids were dominated by wax esters in females and CV. The fatty acid and fatty alcohol compositions of females were very similar throughout the study region and period. Major fatty acids were 18:1(n−9), 16:1(n−7), 16:2(n−4) and 20:5(n−3). Our results support the previous reports of a seasonal dormancy of R. nasutus in the Gulf of Aqaba and suggest that the timing of vertical migration, feeding and maturation is closely coupled to the development of the spring bloom in oligotrophic subtropical waters.

Beschreibung: The abundance and vertical distribution of microcopepods sampled by nets with 55 μm mesh size was compared for two neighbouring but hydrographically different areas, the Gulf of Aqaba and the northernmost Red Sea, during spring 1999. The vertical structure of the total microcopepod communities differed considerably between the two regimes: In the stratified waters of the Red Sea, calanoids outnumbered oncaeids as well as oithonids at 0–100 m, whereas oncaeids dominated in all meso- and bathypelagic layers below 100 m deep. In the unusually deep vertically mixed waters of the Gulf of Aqaba, calanoids outnumbered each of the non-calanoid taxa as deep as 250 or 350 m, whereas the oncaeid dominated deep water community was restricted to depth ranges below 400 m. Dominant non-calanoid species in both areas were Oncaea bispinosa, Paroithona pacifica, Oithona simplex, Spinoncaea ivlevi, O. tregoubovi and O. cristata. O. scottodicarloi occurred in exceptionally high numbers in the northern Gulf. Pronounced differences between the two areas were found in the vertical distribution of poecilostomatoid species. By comparing the present results with published data from the central and southern Red Sea and other tropical and warm-temperate oceanic areas, intra- and inter-oceanic differences in the structure of microcopepod communities in oligotrophic areas are discussed. The high abundance and vertically extended range of calanoid copepods during spring appears to be a specific feature of the Gulf of Aqaba, indicating an unusual vertical succession in the trophodynamic structure of the copepod fauna in this area.

Beschreibung: 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.

Beschreibung: Aim Biodiversity dynamics comprise evolutionary and ecological changes on multiple temporal scales from millions of years to decades, but they are often interpreted within a single time frame. Planktonic foraminifera communities offer a unique opportunity for analysing the dynamics of marine biodiversity over different temporal scales. Our study aims to provide a baseline for assessments of biodiversity patterns over multiple time-scales, which is urgently needed to interpret biodiversity responses to increasing anthropogenic pressure. Location Global (26 sites). Time period Five time-scales: multi-million-year (0-7 Myr), million-year (0-0.5 Myr), multi-millennial (0-15 thousand years), millennial (0-1,100 years) and decadal (0-32 years). Major taxa studied Planktonic foraminifera. Methods We analysed community composition of planktonic foraminifera at five time-scales, combining measures of standing diversity (richness and effective number of species, ENS) with measures of temporal community turnover (presence-absence-based, dominance-based). Observed biodiversity patterns were compared with the outcome of a neutral model to separate the effects of sampling resolution (the highest in the shortest time series) from biological responses. Results Richness and ENS decreased from multi-million-year to millennial time-scales, but higher standing diversity was observed on the decadal scale. As predicted by the neutral model, turnover in species identity and dominance was strongest at the multi-million-year time-scale and decreased towards the millennial scale. However, contrary to the model predictions, modern time series show rapid decadal variation in the dominance structure of foraminifera communities, which is of comparable magnitude as over much longer time periods. Community turnover was significantly correlated with global temperature change, but not on the shortest time-scale. Main conclusions Biodiversity patterns can be to some degree predicted from the scaling effects related to different durations of time series, but changes in the dominance structure observed over the last few decades reach higher magnitude, probably forced by anthropogenic effects, than those observed over much longer durations.

Beschreibung: Zooplankton plays a notable role in ocean biogeochemical cycles. However, it is often simulated as one generic group and top closure term in ocean biogeochemical models. This study presents the description of three zooplankton functional types (zPFTs, micro-, meso- and macrozooplankton) in the ocean biogeochemical model FESOM-REcoM. In the presented model, microzooplankton is a fast-growing herbivore group, mesozooplankton is another major consumer of phytoplankton, and macrozooplankton is a slow-growing group with a low temperature optimum. Meso- and macrozooplankton produce fast-sinking fecal pellets. With three zPFTs, the annual mean zooplankton biomass increases threefold to 210 Tg C. The new food web structure leads to a 25% increase in net primary production and a 10% decrease in export production globally. Consequently, the export ratio decreases from 17% to 12% in the model. The description of three zPFTs reduces model mismatches with observed dissolved inorganic nitrogen and chlorophyll concentrations in the South Pacific and the Arctic Ocean, respectively. Representation of three zPFTs also strongly affects phytoplankton phenology: Fast nutrient recycling by zooplankton sustains higher chlorophyll concentrations in summer and autumn. Additional zooplankton grazing delays the start of the phytoplankton bloom by 3 weeks and controls the magnitude of the bloom peak in the Southern Ocean. As a result, the system switches from a light-controlled Sverdrup system to a dilution-controlled Behrenfeld system. Overall, the results suggest that representation of multiple zPFTs is important to capture underlying processes that may shape the response of ecosystems and ecosystem services to on-going and future environmental change in model projections.