Environmental influence on phytoplankton communities in the northern Benguela ecosystem

Barlow, R; Lamont, T; Louw, D; Gibberd, M-J; Airs, RL; van der Plas, A. 2018 Environmental influence on phytoplankton communities in the northern Benguela ecosystem. African Journal of Marine Science, 40 (4). 355-370. https://doi.org/10.2989/1814232X.2018.1531785

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Official URL: http://dx.doi.org/10.2989/1814232X.2018.1531785

Abstract/Summary

An investigation of surface phytoplankton communities was undertaken on the shelf of the northern Benguela upwelling ecosystem during austral autumn (May) and spring (September), along latitudinal transects at 20° S and 23° S, from 2 to 70 nautical miles offshore, as well as on a zigzag grid located between these transects. Microscopic identification of the phytoplankton and CHEMTAX analysis of pigment biomarkers were used to characterise the community composition. During May 2014, warmer, more-saline water with a shallower upper mixed layer corresponding to periods of less-intense offshore Ekman transport was encountered on the shelf. Satellite imagery indicated high phytoplankton biomass extending for a considerable distance from the coast, and CHEMTAX indicated diatoms as dominant at most of the stations (52–92%), although dinoflagellates were dominant at some inshore localities (57–74%). Species of Chaetoceros, Bacteriastrum and Cylindrotheca were the most abundant, with abundance of the Pseudo-nitzschia ‘seriata-group’ being particularly high at a number of stations. In September 2014, more-intense wind-forcing resulted in a deeper upper mixed layer and stronger upwelling of colder, less-saline water. Elevated phytoplankton biomass was confined close to the coast, where diatoms accounted for most of the population (54–87%), whereas small flagellates, such as prasinophytes, haptophytes and cryptophytes, as well as the cyanobacterium Synechococcus, dominated the communities (58–90%) farther from the coast. It is hypothesised that stronger upwelling and deeper vertical mixing in September of that year were not conducive for widespread diatom growth, and that small flagellates populated the water column by being entrained from offshore onto the shelf in the upwelled water that moved in towards the coast.

Item Type: Publication - Article
Additional Information. Not used in RCUK Gateway to Research.: This is the Authors Accepted Manuscript whose final and definitive form has been published in African Journal of Marine Science 2018, 4: 355-370 © 2018 copyright NISC (Pty) Ltd. African Journal of Marine Science is available online at: http://www.tandfonline.com/10.2989/1814232X.2018.1531785
Divisions: Plymouth Marine Laboratory > Science Areas > Marine Biochemistry and Observations
Depositing User: Kim Hockley
Date made live: 27 Feb 2019 09:03
Last Modified: 27 Feb 2019 09:03
URI: http://plymsea.ac.uk/id/eprint/8150

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