Presenter: Madeleine Schwede (Wellesley College)

Description:
Calculating net community production (NCP) allows us to quantify the productivity of the phytoplankton in the ocean. NCP, the difference between total photosynthesis and community respiration, is a measure of the total amount of carbon dioxide taken up by the ocean’s biological pump. We analyze the relationship between NCP and abiotic factors such as temperature, salinity, and wind speed in order to predict the effect of climate change on productivity. The Ocean Twilight Zone (OTZ) project by Woods Hole Oceanographic Institute and the Ocean EXPORTS team partnered in May 2021 on the Sarmiento de Gamboa cruise to explore the carbon pump from the ocean surface to the twilight zone. In this study, CTD and O2/Ar data from the 2021 Sarmiento de Gamboa cruise in the northern Atlantic are used to calculate NCP. We found high productivity during this cruise with an average NCP of about 32.8 mmol O2 m-2d-1 and a maximum of over 100 mmol O2 m-2d-1. The relationship between NCP and abiotic factors during two storm events was also analyzed. We discover a strong correlation between temperature and salinity during both storm events. Although NCP is weakly correlated with wind speed during both storms, we can see a negative effect of increased wind speed on NCP during the first storm and a positive effect during the second storm. However, the decrease in wind speed at the calm at the end of the storm resulted in an increasing NCP after both storm events. These results reveal the importance of temperature and salinity to community production; additionally, the variable relationship between NCP and wind speed is telling of how dynamic the ocean is. Understanding the effect of extreme weather events on NCP gives us insight into the effects of climate change on the ocean’s carbon pump.