The role of gelatinous zooplankton for marine ecosystems and the carbon cycle

Wright, Rebecca (2019) The role of gelatinous zooplankton for marine ecosystems and the carbon cycle. Doctoral thesis, University of East Anglia.

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Abstract

There is increasing recognition of the importance of gelatinous zooplankton (GZ) within the ocean. However, observations of GZ and understanding of their ecosystem role, lags behind other zooplankton. Increasing pressures on the ocean, including climate change and overfishing, will likely impact GZ. This thesis aims to identify the role of GZ in the marine ecosystem and carbon cycle using observations and a model. This is achieved by (1) an analysis of GZ abundance and biomass from a global database, (2) the addition of GZ as a Plankton Functional Type in the global biogeochemical model PlankTOM11, (3) an analysis of the effect of GZ on carbon export in PlankTOM11 and (4) a case study on the effects of overfishing and climate change on GZ in PlankTOM11. Model developments made use of available vital rates and biomass data. Parameterisation of mortality was the largest source of uncertainty for GZ; therefore, mortality was tuned based on the resulting biomass generated by PlankTOM11. GZ had the largest influence on macrozooplankton biomass and influenced the whole plankton ecosystem through trophic cascades. PlankTOM11 showed trophic level as the most important characteristic of GZ for increasing export. There is evidence that GZ mortality plays an important role in export, but this is not replicated in PlankTOM11, likely due to particulate organic carbon (OC) representation as smaller and with slower sinking speeds than GZ carcases. Further partitioning of OC should improve the representation of GZ mortality and its influence on export. The case study found overfishing reduced GZ biomass, in opposition to other studies. The lack of fish predation on GZ may be a key factor. Climate and overfishing acted synergistically on the ecosystem. GZ play a key role in marine ecosystems by influencing plankton community structures through trophic cascades, thus influencing carbon export.

Item Type:	Thesis (Doctoral)
Faculty \ School:	Faculty of Science > School of Environmental Sciences
Depositing User:	Jennifer Whitaker
Date Deposited:	27 Feb 2020 16:22
Last Modified:	27 Feb 2020 16:22
URI:	https://ueaeprints.uea.ac.uk/id/eprint/74335
DOI:

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