Description: Commercially exploited stocks that have experienced declines in population abundance have responded by altering life history traits of growth and maturation. Cod is not only becoming mature at an earlier age but also, the majority of the stock comprises fishes with no previous spawning experience. Actual fisheries management does not take in account qualitative differences within the spawning stock. If the stock responds to continued exploitation by shifting maturity to an earlier stage, fish will spawn at smaller sizes. They will produce smaller eggs, and consequently small and less viable larvae, so that the contribution to the spawning stock biomass will be less than expected. There are many advantages for delaying maturation: Larger and heavier fish will be better conditioned for spawning, have higher fecundity and larger eggs that are more viable. Harvesting at delayed recruitment enables the stock to maintain a larger SSB with an expanded age structure while supporting a sustainable fishery.

Description: Over the past decade large carbonate mound structures, situated in several provinces along the European continental margin have been discovered in 600 to 1200 m water depths. These structures appear as single, conical or ridge-like features, which are often colonised by a deep-water coral ecosystem. Cold-water corals Lophelia pertusa and Madrepora oculata dominate the coral community. Associated sessile and vagile fauna, like sponges, soft corals, bivalves, gastrodpods, crinoids, brachiopods, and fish make these bioherms as diverse as their tropical counterparts. The objective of this study is to reconstruct past environmental settings locked in the sediments of a carbonate mound in the northern Porcupine Seabight, west off Ireland. Detailed investigations were concentrated on seven 3.5 to 6 m long sediment cores, retrieved from Propeller Mound and its closer vicinity. This mound is a ~150 m high structure within the Hovland Mound province, a cluster of several sea-floor protruding carbonate mounds. A first detailed analysis on benthic foraminiferal assemblages in the vicinity of a carbonate mound was performed on two sediment cores, one located on top of the mound and a second one from an off-mound position further north as control site. The off-mound samples reveal two different assemblages: (1) an Interglacial group dominated by infaunal species reflecting present-day environmental and oceanographic conditions with high nutrient flux to the sea-floor and low sediment accumulation under a strong hydrodynamic regime, and (2) a Glacial group, dominated by cassidulinid species, which describe an influence of polar conditions with low nutrient supply and cold intermediate waters. A single species, Elphidium excavatum, dominates the lower core section and is described here as a species displaced from shallow shelf areas. This removal of sediments from the shelf is related to a first advance of the Irish Ice Sheet onto the Irish Mainland shelf, inducing high sedimentation rates of ~28 cm/kyr with a coeval sea-level drop of ~50 m during Late Marine Isotope Stage (MIS) 3. Due to an incomplete stratigraphic record in the on-mound core, the same species of the off-mound assemblages have been grouped in on-mound samples. The results indicate a dominance of the Interglacial group, whereas the Glacial group is less abundant throughout the entire core. This pattern indicates the lack of glacial time intervals in the on-mound core, which is coherent with stable oxygen isotope data and U/Th dates on coral fragments, presenting only interglacial/-stadial values and ages. A third assemblage is abundant in samples of the on-mound core showing elevated epibenthic species not occurring in offmound samples or only to a minor degree. This Mound group shows a great affinity to strong currents, high nutrient availability and is supposed to indicate Mediterranean Outflow Water in the northern Porcupine Seabight, as well as a higher coral cover on Propeller Mound in an earlier interglacial period. A Late Pleistocene decline in mound growth for Propeller Mound is suggested by a decrease of the Mound group towards the Holocene, which might face its complete burial in the future as this already happened to the buried mounds of the Magellan Mound province further north. Detailed information on off-mound sediment structures and contents from visual core description and the interpretation of Computer Tomographic images were used to evaluate sedimentary processes in glacial and interglacial periods. The sediments portray the depositional history of the past ~31 kyr BP, mainly controlled by sea-level fluctuations and the climate regime with the advance and retreat of the Irish Ice Sheet onto the Irish Mainland Shelf. A first advance of glaciers is indicated by a turbiditic release slightly older than 31 kyr BP, coherent with Heinrich event 3. During MIS 3 and MIS 2 shelf erosion prevailed with abundant gravity flows and turbidity currents. A change from glaciomarine to hemipelagic contourite sedimentation during the onset of the Holocene indicates the establishment of the strong, present-day hydrodynamic regime at intermediate depths. A general decrease in sediment accumulation with decreasing distance towards Propeller Mound was discovered throughout the entire core sections. This suggests that currents (turbidity currents, gravity flows, bottom currents) have had a strong impact on sediment accumulation at the mound base for the past ~31 kyr BP. Finally, the reconstructed environmental setting deduced from sedimentary and micropaleontological analyses portrays the boundary conditions of the habitable range for the cold-water coral Lophelia pertusa. The growth of this ecosystem occurs during interglacial and interstadial periods, whereas a glacial retreat of corals is documented in the absence of glacial sediments in the onmound core. These conclusions are summarised in a model – the Mound Factory – which efficiently accounts for the moundd development covering the period of the Northern Hemisphere Glaciation (past 3.1–2.5 Ma).

Description: The present study aimed to know the influence of five phytoplankton species on the feeding behavior, reproduction and survival of the copepod A. tonsa. Biochemical parameters (total lipid, carbohydrate and protein) were measured to know the possible nutritional value of the diet. The species were offered to A tonsa as single and mixed diet. The species used were the flagellates C. acantha and R. baltica, the potentially toxic dinoflagellates A. tamarense and P. lima and the diatom S. costatum. Protein (55-69%) was the major biochemical components per cell volume, following for carbohydrate (17-31%) and lipid (13-18%). The concentration of the biochemical components measured per cell volume influenced the hatching success and survival of the adults. The hatching success was correlated with the egg production and ingestion rate of the copepod and survival of the early stages. No correlation was found between egg production and the biochemical concentration per cell volume. The biochemical components per cell volume showed a high interspecific difference between the species and seemed to better explain part of the nutritional value of the phytoplankton, as the concentrations per dry weight and volume medium. The copepod A tonsa had a selective feeding behavior feeding preferable on S. costatum and R. baltica in the mixed food. The ingestion rate of the specie C. acantha was reduced into the mixed food. The size range of the species offered to A. tonsa did not influence its ingestion rate.The flagellates R. baltica and C. acantha and the mixed food provided the best effects on the reproduction and survival of A. tonsa. The best results among the single foods treatments were found with the alga, with the higher lipid content (R. baltica and C. acantha). The dinoflagellates P. lima all showed eggs production and good hatching but, the survival of adults and early stages was affected. S. costatum prevented egg production. The survival and reproduction of A. tonsa fed on A. tamarense was reduced and comparable to the control (without food). In spite of, no influence was seen when S. costatum, P. lima and A. tamarense were offered mixed with the two flagellates. The mixed food was the best food. This result could demonstrate that the negative effect of these species on the reproduction and survival of A. tonsa was due their insufficient biochemical content as the presence of toxin. A good food muss proved not only a good egg production and hatching success, but a high the survival of the first stages, guaranteed the survival of the organism in the environment. The negative effect of the dinoflagellates on the survival of the early stages of the copepod indicated that these species were a bad food for A. tonsa. Therefore, A. tamarense, S. costatum and P. lima were no a good diet as single food to A. tonsa. The best results with the mixed food could be result from an increase on the levels of DHA, provided for R. baltica, and EPA, provided for S. costatum, also as for the increase of protein supplied for C. acantha, major content of protein per cell volume. But for a better understand of the relation of the biochemical contents with survival e reproduction of aquatic animals makes necessary a analysis of vitamins, minerals and of the constitutes of each gross biochemical composition, such as fatty acids, amino acids, sterols, sugars.

Description: Das Verhalten sowohl adulter Weibchen als auch juveniler Karettschildkröten (Eretmochelys imbricata) auf See wurde aufgezeichnet und die Tauchgänge in Abhängigkeit von unterschiedlichen extrensischen und intrensischen Bedingungen analysiert. In den zwei Karibischen Untersuchungsgebieten wurden an den freilebenden Karettschildkröten Geräte befestigt, die Wassertemperatur, Lichtintensität, Schwimmgeschwindigkeit, Tiefe, Himmelsrichtung und Lage im Raum in Messintervallen zwischen 0.25 und 30 sek aufzeichneten. Während der Reproduktionsphase führten adulte Weibchen Ruhetauchgänge durch, die unabhängig vom Tagesrhythmus waren. Lediglich kurz vor der Eiablage zeigte sich ein nachtaktiver Rhythmus. Während eines Hurrikans war das Verhalten des betroffenen Weibchens kurzfristig verändert und die Wassertemperatur mittelfristig erniedrigt. Immature Karettschildkröten zeigten einen deutlich tagaktiven Rhythmus mit kürzeren, aktiven Tauchgängen am Tag und langen Ruhetauchgängen in der Nacht. Nach Beendigung der Nistsaison suchten die untersuchten Weibchen Nahrungsgründe in verschiedenen Himmelsrichtungen und Entfernungen zwischen 70 und 360 km auf. Im grundsätzlichen Tauchverhalten adulter Weibchen ausserhalb der Reproduktionsphase wurde Tagaktivität nachgewiesen. Die erhobenen Daten zeigen eine Abhängigkeit der Tauchdauer von der saisonal schwankenden Wassertemperatur und von der Körpermasse des Tieres.

Description: The overflow of dense water from the Nordic Seas through the Denmark Strait is one of the primary sources of the deep water in the world’s oceans. In 1998, a rapid high-resolution survey on the F/S Poseidon with expendable profilers (XCP/XCTD) collected velocity, temperature, and salinity data from the region of the Denmark Strait sill to study the initial descent of the overflow into the deep North Atlantic. The major results from this and an earlier, more modest, survey in 1997 on the R/V Aranda, along with additional analysis of satellite and current meter data, can be summarized as follows: - The flow near the sill is characterized by a strongly barotropic structure associated with a nearly-vertical temperature front. As the denser water descends the Greenland slope, it develops the bottom-intensified structure characteristic of a gravity current. - Initial transport of sq 〉 27.8 water at the sill is measured by the synoptic sections to be 2.7 ± 0.6 Sv, essentially identical both in mean and variability to that measured in 1973 by a 5-week current meter array deployment. - Despite large spatial and temporal variability in velocity, thickness, and transport, the overflow’s pathway and descent with distance from the sill are remarkably steady. - Measurements of near-bottom shear stress (from logarithmic velocity fits) confirm the importance of bottom friction in controlling the rate of overflow descent. - Satellite sea-surface temperature images confirm the birth and downstream propagation of cyclonic eddies starting at approximately 125 km southwest of the sill. This same point is also marked by a change in the rate of overflow entrainment and a maximum in overflow speed. Σ The presence of subsurface eddies upstream of the appearance of the surface features suggests a geographical separation between the region of flow instability and the site of eddy generation and vortex stretching. These two distinct processes occur in the approach to the sill and over the steepest descent, respectively.

Description: In this thesis I studied the clonal structure in dense eelgrass (Zostera marina) meadows in the Baltic Sea in the context of the mating system, inbreeding depression, local adaptation, kinship structure and genet dynamics. I used microsatellite markers to access the fine scale (1-m) clonal structure in four 15-m x 15-m plots located within dense eelgrass meadows in two populations on the Baltic Coast (1.5 – 3.5 m water depth). These plots served as templates for the selection of replicated transplants for laboratory and field experiments, as permanently marked areas for resampling and tracking genets and as database for the calculation of genetic parameters. The key questions investigated and their answers were the following: (i) Can flowering ramets recognize their genetic neighbourhood through pollen and/or growth interactions? - Addition of self versus cross pollen affected the inflorescence sex ratio. This can only be explained by the presence of a cryptic self-incompatibility system. (ii) Does inbreeding depression influence the size distribution of eelgrass clones? - The level of heterozygosity was higher in larger clones. Together with measures of reproductive output this suggests that large dominant clones outcompete their relatively inbred neighbours in an environment with low levels of disturbance. (iii) Are eelgrass clones locally adapted? - Transplantation of replicated genets between two populations showed significant local adaptation and dominance at one site. (iv) Does limited gene flow lead to kinship structure beyond the spatial spread of eelgrass clones? - Spatial autocorrelation, modified for a clonal species, revealed significant coancestry (fij) for the neighbourhood of ramets, clone fragments and entire clones. (v) What are the demographic parameters of eelgrass genets? - Eelgrass clones showed surprisingly high turnover across genets but almost constant patterns within genets between the years 2000 and 2001. This suggests a genetic component to flowering intensity and the production of vegetative shoots. This last study was designed to continue for several more years.

Description: The aim of this study was to elucidate the foraging ecology of South American sea lions (Otaria flavescens) on the Patagonian shelf. Data from satellite tags revealed that male sea lions use a much larger part of the shelf than females and often reach areas close to the shelf break, which may be related to the highly productive shelf break front. The data also showed a high site fidelity, both towards feeding grounds and haul-out sites. Calculations of food consumption revealed that the impact that males have on their prey resources depends on the time that the animals spend at sea, and thus the distance to suitable foraging grounds. A new non-electronic release-mechanism was developed for the recovery of dead reckoners that were used to study the diving behaviour of sea lions. The diving data supported the expectations that males, because of their larger size, had a greater diving capacity than females, which lead to a greater dive efficiency at depths greater than 45m. The use of an Area-Interest-Index to determine space usage revealed that sea lion foraging trips can be divided into distinctive travel and foraging phases. Differences in this index were also visible on the scale of individual dives.

Description: The Denmark Strait overflow is the major gateway for dense water from the Nordic Seas into the North Atlantic and thus it constitutes an important part of the thermohaline circulation under present-day climate conditions. This study focuses on the regional to basin wide dynamics of the Denmark Strait overflow for present-day and Last Glacial Maximum conditions. It contributes to the Research Unit Ocean Gateways located at the University of Kiel which addresses the question how ocean gateways might have affected climate in the past.The volume transport of the overflow is likely to be controlled by hydraulic constraints, thus the transport is set by the relative density contrast between the water masses north and south of the Denmark Strait and the height of dense water above sill level. By using high resolution numerical models it is investigated how the volume transport can be best described using existing hydraulic theories. Hydraulic constraints are shown to be valid over a wide parameter range which allows to transfer this theory to LGM conditions. During the LGM both bathymetry and hydrography have been different and the relative importance of the individual effects is disentangled using a high-resolution numerical model. The drop in eustatic sea-level and glaciated shelves in this area had a comparable smaller effect than the reduced density contrast. In addition to buoyancy forcing wind stress might play a role in setting the overflow transport. In a regional model of the Greenland-Scotland Ridge an influence of wind stress on the overflow can be shown. Therefore, wind stress changes due to different phases of the NAO are expected to imprint a signal on the overflow transport. The same holds for wind field changes from Last Glacial Maximum to present-day conditions. Even though the wind stress was increased the density difference between Nordic Seas and North Atlantic supports almost no buoyancy forcing of the overflows thus the Denmark Strait overflow was probably reduced to less than 0.5 Sv during Last Glacial Maximum summer. However, it is proposed that the increased LGM wind stress is an important factor in keeping the Nordic Seas ice free during summer. The heat transport associated with the volume transport is generally reduced for the Last Glacial Maximum with a pronounced reduction if the Denmark Strait is additionally closed e.g. by iceberg blocking. The relation connecting hydraulic constraints and volume transport was implemented in a global climate model to improve the representation of the Denmark Strait overflow in that model. It results in an increased Atlantic meridional overturning and the associated northward heat transport. A close correlation between overflow representation and climate in northern Europe can be shown. This emphasises the impact of the Denmark Strait overflow on climate even though the response in overturning due to the representation is less than expected from previous studies. There is nearly no stabilising effect of the overflow for large scale freshwater perturbations but a weak effect if the system is perturbed locally in the Labrador Sea.

Description: Die Muschel Calyptogena pacifica (Fam. Vesicomyidae) lebt an den kalten Quellen, den Cold Seeps, der Subduktionszonen. Sie lebt mit sulfidreduzierenden Bakterien in ihrem Kiemengewebe in Symbiose. An zwei Muscheln aus den Cold Seeps aus dem Eel River Becken (östlicher Pazifik) wurden Sulphidaufnahmeraten in Abhängigkeit von Schalenlänge und Feuchtgewicht bestimmt. Die Untersuchungen an zwei neu entdeckten Cold Seeps vor Markan und West-Java haben gezeigt, dass die Wechselbeziehung zwischen dem tektonisch-geologischen Sulfidfluss und der Sulfidaufnahme seep-assoziierter vesicomyider Muscheln für einzelne Fluidaustrittsstellen gilt. Die Muschelkolonien, die um diese Austrittsstellen herum siedeln, dienen als optischer Anzeiger. Eine systematische video- und fotounterstützte Kartierung der Cold Seep Gebiete kann mit geochemischen Stoffflüssen gekoppelt werden.

Description: Der marine Kohlenstoffkreislauf wurde mit neuen Ansätzen zur flächenbezogenen Modellierung für drei unterschiedliche Regionen, den nordöstlichen Nordatlantik, den Nordwestatlantik und den äquatorialen Ostatlantik, unter Anwendung eines Geoinformationssystems (GIS) bilanziert. In regionalen Detailstudien zum Transport organischen Kohlenstoffes aus der photischen Zone zum Meeresboden anhand empirischer Analysen und repräsentativer Datensätze zur Primärproduktion an der Meeresoberfläche anhand von Satellitenfernerkundung und zur direkten Bestimmung benthischer Sauerstoffzehrung, die den Abbau organischer Substanz in entsprechender Wassertiefe am Meeresboden widerspiegelt, konnten die Variabilität und die Abhängigkeiten ortsspezifischer Prozesse erfasst, eingegrenzt und bilanziert werden. Kleinregionale und tiefenbezogene Massenbilanzen wurden für jedes Gebiet aufgestellt, um die Kopplung benthisch-pelagischer Prozesse des marinen Kohlenstoffkreislaufes zu untersuchen. Demnach werden biogeographische Zonierungen der Meeresoberfläche in kleinräumiger Auflösung auch aus benthischer Sicht wiedergegeben und können zur Bilanzierung des Abbaus organischer Substanz in der Tiefsee und der langfristigen Einbettung in das Sediment herangezogen werden. Im Gegensatz zu globalen Beziehungen und Bilanzen ergaben sich regional signifikante Unterschiede im Export zum Meeresboden und der benthischen Remineralisierung. Typische tiefenabhängige und kleinregionale Verteilungsmuster konnten so mit Hilfe empirischer Relationen und eines GIS sichtbar gemacht und bilanziert werden.