Processes and microbial patterns of the Agulhas system

Boundary currents are an important oceanographic feature. The Agulhas current, as an example of a boundary current, drives many oceanographic features. Microbial communities as the basis of the marine food web, respond to environmental changes. Understanding the drivers of these microbial communities provides insight into the impact of environmental changes. The objective of the project was to determine the microbial community dynamics within the Agulhas current and adjacent areas. The drivers of these community patterns were determined to explain the patterns observed. A comparison between nearshore and offshore habitats was investigated in the present study. Samples were collected from the Agulhas Bank and across the Agulhas Current aboard the RV SA Agulhas II in July 2016 and 2018. Six-hourly underway sampling was conducted to collect samples from Cape Town to the Agulhas System Climate Array (ASCA) transect. Subsurface (7m) seawater was collected at each site from the underway and water was collected from the CTD at depths to capture the chlorophyll maximum (fmax, 15-90m depth). Microbial biomass was collected by filtration onto a 0.22 micron nylon filter (Pall Corporation) and targeted gene-specific PCR amplification was carried out for 16S rRNA, 18S rRNA and rbcL gene for identifying the prokaryotic and eukaryotic community structure across the Agulhas system.