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dc.contributor.advisorBrierley, Andrew
dc.contributor.authorBoersch-Supan, Philipp Hanno
dc.coverage.spatialxvi, 225 p.en_US
dc.description.abstractThe waters of the open ocean constitute the largest living space on Earth but despite its obvious significance to the biosphere, the open ocean remains an unexplored frontier. With a regional focus on the Indian Ocean, this thesis investigates (i) the distribution of pelagic biota on basin scales, (ii) the effect of abrupt topography on pelagic biota and their predator-prey relationships, and (iii) the use of genetic techniques to elucidate population connectivity and dispersal of pelagic taxa. (i) Pelagic scattering layers (SLs) were surveyed with scientific echosounders across the southwest (SWIO) and central Indian Ocean to investigate their vertical and geographical distribution. Structurally distinct SL regimes were found across the Subantarctic Front, and may explain recently observed foraging behaviours of southern elephant seals. Regression models indicated a close relationship between sea surface temperature and mean volume backscatter, with significantly elevated backscatter in the subtropical convergence zone. The heterogeneous distribution of scattering layer biota may have implications for predator foraging and carbon cycling in the Indian Ocean. (ii) Acoustic surveys revealed diverse interactions between SLs, aggregations and topography around islands as well as shallow (<200m) and intermediate (200-800m) seamounts at spatial scales from 1 to 100 km. Epi-and mesopelagic backscatter was increased around reefs and banks of the Chagos archipelago, indicating connectivity between oceanic and neritic systems. SWIO seamounts harboured summit-associated aggregations, but the distributions of surrounding SLs did not follow a general pattern. Downstream SL depletion was observed in one location and combined with stomach content analyses, provides an insight into the mechanics of prey flux between open-ocean and seamount ecosystems. (iii) A mitochondrial marker was used to assess the population structure and demography of the hatchetfish Argyropelecus aculeatus in the SWIO. The results are suggestive of a single, well-connected population and indicate a recent population expansion around 0.14 million years ago. This highlights that even highly abundant mesopelagic populations are vulnerable to global climatic changes. Dispersal and recruitment are key ecological processes structuring seamount communities and are directly relevant for the management of exploited populations. Genetic barcoding was evaluated as a means to identify cryptic larval specimens of eels (leptocephali) and spiny lobsters (phyllosomata). Identification success was limited, but indicated the presence of 3-4 phyllosoma clades and 5-6 leptocephalus clades along the SWIR.en_US
dc.description.sponsorship"Additional funds came from the German National Academic Foundation, the Rehbock Fund, the Fisheries Society of the British Isles, and the Marin Alliance for Science and Technology for Scotland (MASTS) pooling initiative (Grants DSSG1 and SG98)." -- Acknowledgementsen
dc.description.sponsorshipData collection in the Southwest Indian Ocean was undertaken as part of the Southwest Indian Ocean Seamounts Project ( supported by the EAF Nansen Project, the Food and Agriculture Organization of the United Nations, the Global Environment Facility, the International Union for the Conservation of Nature, the Natural Environment Research Council (Grant NE/F005504/1), the Leverhulme Trust (Grant F00390C) and the Total Foundation. Shiptime in the Chagos was funded by the UK Foreign and Commonwealth Office." -- Acknowledgementsen
dc.publisherUniversity of St Andrews
dc.subject.lcshMarine ecology--Indian Oceanen
dc.subject.lcshSeamount animals--Indian Oceanen
dc.subject.lcshPlankton--Indian Oceanen
dc.subject.lcshElephant seals--Indian Oceanen
dc.subject.lcshOceanography--Research--Indian Oceanen
dc.titleThe ecology of scattering layer biota around Indian Ocean seamounts and islandsen_US
dc.contributor.sponsorLesley & Charles Hilton-Brown Scholarshipen_US
dc.contributor.sponsorStudienstiftung des deutschen Volkesen_US
dc.contributor.sponsorRehbock Funden_US
dc.contributor.sponsorFisheries Society of the British Isles (FSBI)en_US
dc.contributor.sponsorMarine Alliance for Science and Technology for Scotland (MASTS)en_US
dc.contributor.sponsorEAF-Nansen Projecten_US
dc.contributor.sponsorFood and Agriculture Organization of the United Nationsen_US
dc.contributor.sponsorGlobal Environment Facilityen_US
dc.contributor.sponsorInternational Union for Conservation of Natureen_US
dc.contributor.sponsorNatural Environment Research Council (NERC)en_US
dc.contributor.sponsorLeverhulme Trusten_US
dc.contributor.sponsorFondation d'entreprise Totalen_US
dc.contributor.sponsorGreat Britain. Foreign and Commonwealth Officeen_US
dc.type.qualificationnamePhD Doctor of Philosophyen_US
dc.publisher.institutionThe University of St Andrewsen_US

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