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The biogeochemistry and oceanography of the East African Coastal Current

The biogeochemistry and oceanography of the East African Coastal Current
The biogeochemistry and oceanography of the East African Coastal Current
The East African Coastal Current (EACC) is the dominant oceanographic influence along the coastlines of Tanzania and Kenya yet formal descriptions of the biogeochemical characteristics of these waters remain fragmented or poorly defined. Whilst the region remains undersampled, and information for many parameters is limited or even absent, the region is not understudied and complex patterns, due in part to the changing monsoon seasons, can be identified from extant observations. A critical distinction between the neritic waters of the narrow East African continental shelf, which may be more influenced by local tidal currents and terrestrial inputs, and the oligotrophic surface waters of the deeper offshelf region under the influence of the EACC can be drawn, which cautions against the extrapolation of trends or seasonal patterns from limited datasets more widely throughout the region. Permanently N-limited, low NO3-:PO43- surface waters coupled with high (>25°C) sea surface temperatures are a key feature of the EACC Ecoregion and likely responsible for the presence of a regionally important population of the nitrogen fixing cyanobacterium Trichodesmium, though information on another key requirement, iron, is lacking. Phytoplankton diversity, abundance and the spatiotemporal variability of phytoplankton populations are considered poorly known due to limited sampling efforts. Recent and growing recognition of high coral biodiversity, high reef fish species endemism, of widespread reductions in mangrove forest coverage, and growing anthropogenic pressures on coastal waters suggest that the region deserves greater multidisciplinary study. Efforts to anticipate climate induced changes to these waters, which are expected to impact local fisheries with substantial socioeconomic impacts, would benefit from greater efforts to synthesise existing biogeochemical data, much of which resides within grey literature sources, theses, project reports, remains inaccessible or has been lost. Future biogeochemical and oceanographic observational efforts should simultaneously explore shelf and deeper offshelf waters to determine shelf-to-ocean linkages and the spatiotemporal variability of parameter fields whilst also bridging the gap to research efforts on coral biodiversity, fisheries and marine management activities due to recognised gaps in underlying scientific data to support decision making in these areas.
Biogeochemistry, East African Coastal Current, Kenya, Tanzania, Tropical coastal waters, Western Indian Ocean
0079-6611
Painter, Stuart
29e32f35-4ee8-4654-b305-4dbe5a312295
Painter, Stuart
29e32f35-4ee8-4654-b305-4dbe5a312295

Painter, Stuart (2020) The biogeochemistry and oceanography of the East African Coastal Current. Progress in Oceanography, 186, [102374]. (doi:10.1016/j.pocean.2020.102374).

Record type: Article

Abstract

The East African Coastal Current (EACC) is the dominant oceanographic influence along the coastlines of Tanzania and Kenya yet formal descriptions of the biogeochemical characteristics of these waters remain fragmented or poorly defined. Whilst the region remains undersampled, and information for many parameters is limited or even absent, the region is not understudied and complex patterns, due in part to the changing monsoon seasons, can be identified from extant observations. A critical distinction between the neritic waters of the narrow East African continental shelf, which may be more influenced by local tidal currents and terrestrial inputs, and the oligotrophic surface waters of the deeper offshelf region under the influence of the EACC can be drawn, which cautions against the extrapolation of trends or seasonal patterns from limited datasets more widely throughout the region. Permanently N-limited, low NO3-:PO43- surface waters coupled with high (>25°C) sea surface temperatures are a key feature of the EACC Ecoregion and likely responsible for the presence of a regionally important population of the nitrogen fixing cyanobacterium Trichodesmium, though information on another key requirement, iron, is lacking. Phytoplankton diversity, abundance and the spatiotemporal variability of phytoplankton populations are considered poorly known due to limited sampling efforts. Recent and growing recognition of high coral biodiversity, high reef fish species endemism, of widespread reductions in mangrove forest coverage, and growing anthropogenic pressures on coastal waters suggest that the region deserves greater multidisciplinary study. Efforts to anticipate climate induced changes to these waters, which are expected to impact local fisheries with substantial socioeconomic impacts, would benefit from greater efforts to synthesise existing biogeochemical data, much of which resides within grey literature sources, theses, project reports, remains inaccessible or has been lost. Future biogeochemical and oceanographic observational efforts should simultaneously explore shelf and deeper offshelf waters to determine shelf-to-ocean linkages and the spatiotemporal variability of parameter fields whilst also bridging the gap to research efforts on coral biodiversity, fisheries and marine management activities due to recognised gaps in underlying scientific data to support decision making in these areas.

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Accepted/In Press date: 26 May 2020
e-pub ahead of print date: 1 June 2020
Published date: July 2020
Additional Information: Funding Information: This work contributes to the Sustainable Oceans, Livelihoods and food Security Through Increased Capacity in Ecosystem research in the Western Indian Ocean (SOLSTICE-WIO) programme ( www.solstice-wio.org ), a four-year collaborative project funded through the UK Global Challenges Research Fund (GCRF) under NERC grant NE/P021050/1. I am indebted to various colleagues for fruitful scientific discussions during the preparation of this review, to Edward Moto (University of Dodoma) for assistance accessing some of the taxonomic literature, to Fatma Jebri (National Oceanography Centre) for assistance with Fig. 8 , and to colleagues from the Institute of Marine Science (Zanzibar, Tanzania), the Tanzania Fisheries Research Institute (Dar es Salaam, Tanzania), the Kenya Marine and Fisheries Research Institute (Mombassa, Kenya) and Nelson Mandela University (Port Elizabeth, South Africa). ACEP data provided courtesy of L. Scott and M. Roberts. Funding Information: ASCLME, 2012a. National Marine Ecosystem Diagnostic Analysis, Tanzania. Contribution to the Agulhas and Somali Current Large Marine Ecosystems Project (supported by UNDP with GEF grant financing), 91p. Funding Information: ASCLME, 2012b. National Marine Ecosystem Diagnostic Analysis. Kenya. Contribution to the Agulhas and Somali Current Large Marine Ecosystems Project (supported by UNDP with GEF grant financing), 50p. Publisher Copyright: © 2020 The Author(s)
Keywords: Biogeochemistry, East African Coastal Current, Kenya, Tanzania, Tropical coastal waters, Western Indian Ocean

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Local EPrints ID: 441502
URI: http://eprints.soton.ac.uk/id/eprint/441502
ISSN: 0079-6611
PURE UUID: 158c141a-fdbc-4d06-b854-e702a9bc6c11

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Date deposited: 16 Jun 2020 16:31
Last modified: 16 Mar 2024 08:12

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Author: Stuart Painter

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