The impact of physical processes on primary and secondary production in temperate shelf seas

Panton, Anouska
The impact of physical processes on primary and secondary production in temperate shelf seas. Doctor of Philosophy thesis, University of Liverpool.

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The shelf seas account for only 9% of the surface area of the global ocean, yet are estimated to be responsible for 16% of global primary productivity and 47% of global annual carbon export. While the importance of these seas in the marine carbon cycle is well-recognised, the relationship between the physical environment and the magnitude and fate of biological production is still largely undetermined. Using a range of approaches, this project examined the relationship between physical processes and biological carbon flow over various time and space scales in a temperate shelf sea. Autonomous high-resolution sensor surveys in Liverpool Bay and the Irish Sea reveal that this region is net autotrophic on an annual scale with estimates of regional net community production rates based on oxygen mass balance ranging from 1.3 to 4.2 mol C m-2 y-1. The highest NCP rates were measured in a Region Of Freshwater Influence (Liverpool Bay). Ship-based sampling in the Celtic Sea illustrated the influence of water column structure on rates of primary and bacterial production and community structure. The highest rates of primary production were observed in the fully mixed water column (55.1 mmol C m-2 d-1). However, bacterial production rates were lowest at the mixed site (6.8 mmol C m-2 d-1). In contrast, primary production and bacterial production at the seasonally stratified sites and shelf break were comparable (34.8 mmol C m-2 d-1 and 37.2 mmol C m-2 d-1 respectively, and 12.9 and 12.9 mmol C m-2 d-1 respectively). The phytoplankton community was dominated by diatoms at the mixed site and dinoflagellates at the seasonally stratified sites, with both diatoms and dinoflagellates occurring at the shelf edge. Bacterial carbon demand at each site was estimated using published empirical relationships. However, at three out of the four sites examined, the estimated daily rate of total primary production was insufficient to meet the daily bacterial carbon demands, implying that either an external source of carbon was required or that the assumptions used during estimates of bacterial processing of carbon were incorrect. Finally, the definition of export production in shelf seas is examined in relation to the potential pathways of carbon flow on daily and seasonal timescales in shelf seas.

Item Type: Thesis (Doctor of Philosophy)
Additional Information: Date: 2012-08 (completed)
Uncontrolled Keywords: shelf sea, primary production, net community production
Divisions: Faculty of Science and Engineering > School of Environmental Sciences
Depositing User: Symplectic Admin
Date Deposited: 03 Sep 2013 08:32
Last Modified: 17 Dec 2022 01:14
DOI: 10.17638/00009713