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Distribution of deep-sea bioluminescence across the Mid-Atlantic Ridge and Mediterranean Sea : relationships with surface productivity, topography and hydrography

Bioluminescence is widespread in the deep sea. In this study, the density of bioluminescent zooplankton (BL) in the deep Mediterranean Sea (MS) and at the Mid- Atlantic Ridge (MAR) was measured using low light video cameras, including a novel Image intensified Charge coupled device for Deep-sea research (ICDeep). Sampling across the MS was undertaken to assess the potential optical interference from bioluminescent zooplankton at sites under consideration for the construction of a large volume deep-sea neutrino telescope. This revealed a general decrease in deep pelagic BL densities from the western to the eastern MS. Deep mesopelagic (500- 1000 m depth) BL density was significantly correlated (p<O.Ol) to Chlorophyll a concentrations in overlying surface waters. Investigation of temporal variation across the Ionian Sea revealed a deep (500-2400 m depth) peak in BL density on the western side, present in the autumn (mean BL density: 14.92 m-3) and absent the following spring (4.52 rrr"). Deep water of Adriatic origin flows into this region and may seasonally affect the supply of organic material, increasing deep zooplankton populations. Near-bed (0-400 m above bed, mab) BL density in the MS was found to decrease exponentially with seafloor depth; by a factor of 4.2 every 1000 m. BL densities were consistently lower in the MS than at the MAR. On the MAR, at ca. 2500 m depth, an investigation of altitude effects within the near seafloor region revealed a weak increase (0.016 m-3 mab': p<O.OOl) in BL and inacroparticle (>430 urn] densities from 100 to 5 mab attwo sites south of the Charlie-Gibbs Fracture Zone. At 2500 m depth on the MAR, a rate of naturally occurring bioluminescent events was observed to be 155 times higher (3.1 min+) than literature based predictions, prompting a reappraisal of the visual environment in relation to complex topography of the deep-sea floor.

Identiferoai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:569785
Date January 2012
CreatorsCraig, Jessica
PublisherUniversity of Aberdeen
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation
Sourcehttp://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=186379

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