ALANA ZAMMIT
Research Proposal: Understanding the effects of surface temperature and pH on phytoplankton abundance and diversity in the North Atlantic
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Phytoplankton are critically important to ecosystems worldwide. They are single-celled photosynthetic aquatic organisms, which form the foundation of almost all oceanic food webs. They act as a vital carbon sink though their uptake of carbon dioxide in photosynthesis, and in turn, generate significant proportions of the atmosphere’s oxygen. Their abundance and diversity are influenced by a host of environmental factors, including sea surface temperature (SST) and pH levels. Ocean warming and acidification due to climate change may be influencing phytoplankton community structure, in turn affecting primary productivity and marine biodiversity. This study aims to assess the relationships between SST, pH, and phytoplankton diversity and abundance in the North Atlantic over a three-week period.
Data collection will occur onboard the Excelsior, a sail training vessel owned by the Excelsior Trust. Data will be collected between August-September, during three weeks of sailing across the North Atlantic Ocean. Water samples will be taken daily across various latitudes to maximise the number of oceanic zones sampled.
Sea Surface Temperature (SST): Sea surface temperature (SST) will be measured using a digital temperature logger borrowed from the University of Oxford or a partnering institution (enquiries into this are currently ongoing). If specialised equipment is unavailable, SST will instead be measured using a high-precision mercury thermometer.
pH: To measure the pH of each sample site, a portable pH meter will be used, preferably borrowed from a university laboratory (enquiries ongoing). In the absence of electronic equipment, pH indicator strips will be used, which will provide an approximate pH reading.
Phytoplankton sampling and identification: Phytoplankton samples will be collected using a plankton net (mesh size ~20 µm), following methods in Kraberg et al (2017). We will perform vertical tows whenever possible, to ensure the phytoplankton are adequately sampled. All tows will be conducted to a standardised duration and speed. Samples will then be preserved using Lugol’s solution, or stored in cool, dark conditions to be analysed upon return. Phytoplankton diversity and abundance will be analysed using a compound microscope following methods in Karlson (2010).
Data analysis: Phytoplankton diversity and abundance will be analysed with SST and pH levels to identify any correlations between environmental conditions and phytoplankton community structure. To measure changes in phytoplankton diversity across environmental conditions, diversity indices such as the Shannon-Wiener Index will be used.