Impacts of climate change on the planktonic food web in the European Arctic

Price, Elliott ORCID: 0000-0001-8766-6531
(2021) Impacts of climate change on the planktonic food web in the European Arctic. PhD thesis, University of Liverpool.

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Across the globe, planktonic consumer resource interactions are being altered by changing environmental conditions. Climate change is altering the distributions of both phytoplankton and zooplankton, thus modifying the base of the food web, which has consequences for the feeding environment of consumers and predators with knock on effects for population viability. In the Arctic, inflows of Atlantic waters are strengthening, which is increasing sea surface temperatures, weakening stratification and transporting temperate and sub-Arctic plankton species deeper into the Arctic interior. In other regions, increased sea ice melt is freshening and stratifying the water column, causing phenological shifts to phytoplankton blooms. These heterogenous alterations have direct effects to zooplankton feeding and the wider food web. Our knowledge of the responses of zooplankton feeding within the planktonic Arctic food web is limited due to the highly seasonal nature of the Arctic environment that adds to food web complexity. Untangling this complexity remains a challenge if we are to accurately predict and understand the functioning of marine food webs in the Arctic. In this thesis I aim to resolve the spatial and interannual feeding ecology the calanoid copepods Calanus in the Arctic. I use multivariate statistical techniques on an abundance Continuous Plankton Recorder dataset to define the feeding environment for Calanus and a dual biomarker approach of isotope analysis and DNA gut content analysis to estimate the feeding strategies of Calanus. These dietary descriptors are contextualised by environmental parameters derived from CTD casts, remote sensing databases and models. Changes to the food environment for Calanus were variable on both spatial and interannual scales, these include differences in net primary production, and in the phytoplankton assemblage. The drivers of these changes were factors that altered the strength of stratification, which impact nutrient delivery and primary production in the surface. Despite these changes, Calanus were consistently omnivorous, occupying the trophic level 2.5. In some regions, the smaller C. finmarchicus/glacialis had a slightly higher TP than the larger C. hyperboreus, likely due to the earlier termination of feeding by the latter. In water masses with low productivity and strong stratification, the niches of these two Calanus groups were separated, indicating different resource utilization. Whereas in highly productive regions, there was high niche overlap, suggesting the sharing of resources. The high plasticity of Calanus indicates that, providing the nutritional quality of dietary items is maintained, they should continue to transfer essential lipids to the rest of the food web despite the regionally specific changes in stratification and net primary production rates.

Item Type: Thesis (PhD)
Divisions: Faculty of Science and Engineering > School of Environmental Sciences
Depositing User: Symplectic Admin
Date Deposited: 06 Sep 2022 10:06
Last Modified: 18 Jan 2023 21:04
DOI: 10.17638/03153996