La Niña’s affect on the abundance and primary productivity of phytoplankton
Phytoplankton form the base of the food chain in the world’s oceans; their declining or blossoming populations can have major impacts on the abundance of other oceanic species. It is for this reason that I am interested in examining La Niña’s affect on the abundance and primary productivity of phytoplankton populations surrounding the Hawaiian Islands. At the conclusion of our trip, I would like to compare my data with data from previous non-La Niña years to see how a La Niña event influences phytoplankton populations. During a La Niña event, sea surface temperatures can fall by as much as four degrees Celsius, drastically decreasing the stratification in the upper water column (Gorgues et al. 2010). This study expects that a La Niña event will cause phytoplankton populations surrounding the Hawaiian Islands to flourish due to increased upwelling of cold, nutrient-rich deep water. To examine this, conductivity-temperature-depth (CTD) casts will be performed at multiple stations and samples will be collected at various depths using Niskin bottles attached to a CTD rosette. From these samples, cell counts will be performed using an inverted microscope to determine phytoplankton abundance and dissolved oxygen (DO) concentrations will be calculated using Winkler titrations to determine phytoplankton primary productivity. These samples will be collected aboard the R/V Thomas G. Thompson from 27 December 2010 – 5 January 2011. Understanding La Niña’s affect on phytoplankton is important because a large increase in phytoplankton populations could mean a major increase in fish stocks as well. This surge in abundance of fish could have major impacts (e.g. more revenue from fishing, tourism, etc.) for local human populations. The main advisor for this study is Kathy Newell but I will be relying on the entire crew of the R/V Thomas G. Thompson.