The Plymouth Student Scientist
Document Type
Biological and Marine Sciences Article
Abstract
In the context of a rapidly changing climate, understanding how ocean warming is reshaping the foundation of marine ecosystems has never been more important. This research investigates factors contributing to ocean warming, and where anthropogenically influenced climate change plays a critical role in the functionality of the physical marine environment, phytoplankton, and trophodynamics throughout the pelagic zone. Phytoplankton, whilst microscopic, are vital; they are regulated by physical oceanographic factors that control their access to growth-limiting factors, such as nutrients. With the formidable climate-driven physical and biological changes occurring in the marine environment, alongside the decline in fish stocks, it is imperative that oceans are closely monitored using an ecosystem-based approach, with phytoplankton being one of the key indicators of broader environmental health.
Therefore, it was important to focus on the impacts of global warming on physical environmental conditions—such as sea surface temperature and mixed layer depth—and how these affect ocean biology through changes in phytoplankton biomass and phenology. Cost-effective satellite data from NASA’s Goddard Earth Sciences Data and Information Services Center (GES DISC) were used, with changes in phytoplankton dynamics indicating potential implications for fish stocks and current fisheries management around St Helena Island. St Helena’s territorial waters include a 200 nautical mile Category 6 sustainable use marine protected area, underscoring the need to understand and safeguard this ecologically and economically vital region. In this marine hotspot region, interannual variability in sea surface temperature, mixed layer depth, and chlorophyll-α concentration was analysed to identify long-term trends. Additionally, annual phytoplankton blooms were characterised, and shifts in phytoplankton phenology were investigated.
Notably, results of sea surface temperature displayed an increase, with intensified temperature-influenced stratification strengthening, causing the mixed layer depth to become shallower, decreasing phytoplankton biomass, and a non-significant earlier initiation of annual phytoplankton blooms to occur around St Helena. The negative changes in the pelagic layer physics and biology around the island that are linked to ocean warming provided insight into the implications for ocean productivity, fish stocks, and fisheries management. With very little known and understood about St Helena Island’s oceanography, it is crucial that its condition is monitored closely. This is important for the residents dependent on productive regions in their territorial sea for their economy and food security. Finally, it was found that phytoplankton are reactive species to climate change and its indirect effects. Making it an important component of ecosystem-based management as an ecological indicator in pelagic fisheries management.
Publication Date
2025-07-10
Publication Title
The Plymouth Student Scientist
Volume
18
Issue
1
ISSN
1754-2383
Deposit Date
2025-07-29
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Bargo, Shelby
(2025)
"The impacts of ocean warming on phytoplankton dynamics and links to fisheries management around St Helena Island, South Atlantic Ocean,"
The Plymouth Student Scientist: Vol. 18:
Iss.
1, Article 1.
DOI: https://doi.org/10.70156/1754-2383.1513
Available at:
https://pearl.plymouth.ac.uk/tpss/vol18/iss1/1
