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  • 1
    Publication Date: 2018-06-05
    Description: 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.
    Type: Article , PeerReviewed
    Format: text
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  • 2
    Publication Date: 2018-06-05
    Description: 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.
    Type: Article , PeerReviewed
    Format: text
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  • 3
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    American Geophysical Union (AGU)
    In:  EPIC3Journal of Geophysical Research Biogeosciences, American Geophysical Union (AGU), 127(10), ISSN: 2169-8953
    Publication Date: 2023-06-21
    Description: 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.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
    Format: application/pdf
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