Chemical composition of manganese nodules and crusts from the Pacific and Indian Ocean and Loch Fyne, Scotland

The first part of this thesis includes some topics of a non-geochemical nature but which are of importance in interpreting the geochemistry of nodules. The points covered include their distribution, petrography, structure, mineralogy and internal compositional variations. Part Two includes the geochemistry of both nodules and that of their surrounding sediments, This geochemical study has been divided into firstly, a general geochemical study of both nodules and sediments using a statistical approach to the interpretation of the data, secondly, the regional geochemistry of Pacific and Indian Ocean nodules and sediments, the latter entirely uninvestigated in the past, and thirdly, local variations in the composition of nodules. Throughout, emphasis has been placed on the geochemistry of nodules in terms of their environment of formation.

Hidden impacts of ocean acidification to live and dead coral framework

Cold-water corals, such as Lophelia pertusa, are key habitat-forming organisms found throughout the world's oceans to 3000 m deep. The complex three-dimensional framework made by these vulnerable marine ecosystems support high biodiversity and commercially important species. Given their importance, a key question is how both the living and the dead framework will fare under projected climate change. Here, we demonstrate that over 12 months L. pertusa can physiologically acclimate to increased CO2, showing sustained net calcification. However, their new skeletal structure changes and exhibits decreased crystallographic and molecular-scale bonding organization. Although physiological acclimatization was evident, we also demonstrate that there is a negative correlation between increasing CO2 levels and breaking strength of exposed framework (approx. 20-30% weaker after 12 months), meaning the exposed bases of reefs will be less effective 'load-bearers', and will become more susceptible to bioerosion and mechanical damage by 2100.

Lithology description, textural and structural observations, and indications for ground ice of sediment core CRP-2 (Table 1-4)

From the upper 300 m of CRP-2/2A, twenty-six samples of diamicts and deformation structures have been thin sectioned. These have been analysed for texture, structure, diagenesis and plasmic fabric. The combination of certain microstructures (e.g. turbate and linear) and plasmic fabric development is indicative of grounded ice. Clear evidence for two grounded ice events (three samples) was found in the upper Oligocene part of the core. The interpretation of ten more samples is less certain, but as for CRP-1, is taken to point to grounded ice as well. There is a strong correlation between these indications for grounded ice and the basal part of cycles in the sequence stratigraphy.

Microsatellite genotyping of Mediterranean population of Ircinia fasciculata and Ircinia variabilis

Recent episodes of mass mortalities in the Mediterranean Sea have been reported for the closely related marine sponges Ircinia fasciculata and I. variabilis, which live in sympatry. In this context, the assessment of the genetic diversity, bottlenecks and connectivity of these sponges has become urgent in order to evaluate the potential effects of mass mortalities on their latitudinal range. Our study aims to establish 1.) the genetic structure, connectivity, and signs of bottlenecks across the populations of I. fasciculata, and 2.) the hybridization levels between I. fasciculata and I. variabilis. To accomplish the first objective, 194 individuals of I. fasciculata from 12 locations across the Mediterranean were genotyped at 14 microsatellite loci. For the second objective, mitochondrial cytochrome c oxidase subunit I sequences of 16 individuals from both species were analyzed along with genotypes at 12 microsatellite loci of 40 individuals coexisting in 3 Mediterranean populations. We detected strong genetic structure along the Mediterranean for I. fasciculata, with high levels of inbreeding in all locations and bottleneck signs in most locations. Oceanographic barriers like the Almeria-Oran front, North-Balearic front, and the Ligurian-Thyrrenian barrier seem to be impeding gene flow for I. fasciculata, adding population divergence to the pattern of isolation by distance derived from the low dispersal abilities of sponge larvae. Hybridization between both species occurred in some populations, which might be increasing genetic diversity and somewhat palliating the genetic loss caused by population decimation in I. fasciculata

Geochemistry of hydrate gas and water at DSDP Hole 84-570

Molecular and isotopic measurements of gas and water obtained from a gas hydrate at Site 570, DSDP Leg 84, are reported. The hydrate appeared to be Structure I and was composed of a solid framework of water molecules enclosing methane and small amounts of ethane and carbon dioxide. Carbon isotopic values for the hydrate-bound methane, ethane, and carbon dioxide were -41 to about -44, -27, and -2.9 per mil, respectively. The d13C-C1 values are consistent with void gas values that were determined to have a biogenic source. A significant thermogenic source was discounted because of high C1/C2 ratios and because the d13C-CO2 values in these sections were also anomalously heavy (or more positive) isotopically, suggesting that the methane was formed biogenically by reduction of heavy CO2 . The isotopically heavy hydrate d13C-C2 is also similar to void gas isotopic compositions and is either a result of low-temperature diagenesis producing heavy C2 in these immature sediment sections or upward migration of deeper thermogenic gas. The salinity of the hydrate water was 2.6 per mil with dDH2O and d18OH2O values of +1 and +2.2 per mil, respectively.

Viral, bacterial and ciliate abundance and viral-bacterial diversity in mesocosm experiments, 2007-2008, Kongsfjorden

Two mesocosm experiments, PAME-I and PAME-II were conducted in 2007 and 2008 to investigate fate of organic carbon in the arctic microbial food web. Mesocosms were nutrient fertilized initially to induce phytoplankton bloom development. In PAME-I eight units (each 700 L) formed two four point gradients of additional DOC in form of glucose (0, 0.5, 1 and 3 times Redfield ratio in terms of carbon relative to the nitrogen and phosphorus additions) (Fig. 1). All the eight units also got a daily dose of NH4+ and PO4**3- in Redfield ratio. Two gradients were set up, one with silicate addition, performed in the Arctic location Ny Ålesund, Svalbard, have previously been reported to give different food-web level responses to similar nutrient perturbations. In PAME-II all ten units (each 900 L) formed two four point gradients of additional DOC in form of glucose (0, 0.5, 1, 2 and 3 times Redfield ratio in terms of carbon relative to nitrogen and phosphorus additions). The two gradients in glucose were kept silicate replete. NH4+ was used as the DIN source in one gradient (units 1 to 5) and NO3- in the other (units 6-9). All units got a daily dose of PO4**3- in Redfield ratio. Prokaryotes and viruses were measured by flow cytometry, while ciliate abundances were counted using a Flow Cam. Viral and bacterial diversity was measured by PFGE and DGGE, respectively. In PAME-II the abundance of ciliates was lower than in PAME-I, presumably caused by higher copepod grazing. The abundances of prokaryotes and viruses were also lower in PAME-II compared to PAME-I. Further, less diversity was detected in the viral community (FCM and PFGE) in PAME-II, and no response was observed in the bacterial community structure due to addition of organic carbon.