Introduction

This project aims to investigate the abundance of phytoplankton in Lombok Strait in relation to SST and wind speed and direction. To measure phytoplankton, data will be taken as Chlorophyll-a which is the main substance of phytoplankton. Chlorophyll-a is vital to our survival, as phytoplankton, the bottom of the food chain in the ocean, rely on them to live. Phytoplankton also generate much of the Earth’s oxygen, so it is important to study their abundance and what affects it, which will be done in this project with SST and wind data. SST affects the value of Chlorophyll-a as cooler waters that upwell to the surface brings nutrients beneficial to the phytoplankton, so phytoplankton are more able to thrive in these waters, while warmer waters tend to hurt them. Wind speed and direction also affects the locations where phytoplankton are able to be found.

Materials

Chlorophyll-a and SST data is taken from oceandata provided by NASA. The sensor is MODIS-Aqua with a 4km resolution. The data will then be processed using SeaDas and ArcGis.

Analysis

Using a calculator to obtain the Pearson’s Correlation Coefficient for each of the averages of the SST and Chlorophyll-a values during the wet and dry season in 2003, 2009 and 2020, the correlation between SST and Chlorophyll-a can be seen below 2003 dry: r=-0,59 2003 wet: r=-0,81 2009 dry: r=0,66 2009 wet: r=0,10 2020 dry: r=0,49 2020 wet: r=0,36 Moderate - Strong - Moderate + Very weak + Weak + Weak + From the Correlation coefficients above, conclusions about the correlation between SST and Chlorophyll-a can be drawn. It is important to note that there is an outlier in the 2009 wet season data, which likely skewed the mean to cause the low correlation strength. The strength of the correlation over the years tends to get weaker, and it changes from a negative correlation to a positive correlation, contradicting with the theory that a higher SST causes a lower abundance of Chlorophyll-a due to less upwelling happening [2]. It is also important to note that correlation does not equal causation, so changes in SST might not have been the reason for a change in the abundance of Chlorophyll-a, and it might have been caused by other factors instead. The strength of correlation during the dry season is also stronger than during the wet season, which is interesting because Chlorophyll-a tends to be more profound after periods of rainfall due to the rain providing nutrients to the water, helping the phytoplankton grow, but the data contradicts this hypothesis, since it is shown to have stronger reactions towards the dry seasons’ temperature changes. From the mapped data, it can also be seen that the locations where Chlorophyll-a is abundant in is affected by the wind direction and speed. During the dry season when the winds are weaker and slower, Chlorophyll-a is mainly found in the bottom of the subset in the map, whereas during the wet season, where the winds have higher speed, the Chlorophyll-a is pushed upwards towards the top of the map. This can be correlated to how wind speed and direction affects the currents in the ocean, which in turn pushes the surface waters away, leading to the deeper, more nutritious waters to upwell, which then increases phytoplankton abundance and deciding the location of the Chlorophyll-a abundance [10].

Conclusion

Though Chlorophyll-a abundance is currently stable according to the statistics, average SST values are getting higher. Phytoplankton are very sensitive to environmental changes, such as temperature, since high temperature waters decrease the amount of nutrients in the surface for phytoplankton to use in their growth. Phytoplankton are important to us in many ways [6], one of the biggest ways being oxygen generation, and the ocean ecosystem relies on phytoplankton as the primary producer for the first consumers in the food chain, so it is important to ensure that Chlorophyll-a levels remain stable. With this project, we hope to spread awareness regarding the significance of phytoplankton in the environment, and introduce some factors that affect its abundance that we should consider to establish sustainability in our ecosystem