Περίληψη:
The North Kenya Banks (NKBs) have recently emerged as a new frontier for
food security and could become an economically important fishery for
Kenya with improved resources providing better accessibility. Little
research has been done on the mechanisms supporting high fish
productivity over the NKBs with information on annual and interannual
environmental variability lacking. Here we use a high-resolution,
global, biogeochemical ocean model with remote sensing observations to
demonstrate that the ocean circulation exerts an important control on
the productivity over the NKBs. During the Northeast Monsoon, which
occurs from December to February, upwelling occurs along the Kenyan
coast, which is topographically enhanced over the NKBs. Additionally,
enhanced upwelling events, associated with widespread cool temperatures,
elevated chlorophyll, nutrients, primary production, and phytoplankton
biomass, can occur over this region. Eight such modeled events,
characterized by primary production exceeding 1.3 g C/m(-2)/day, were
found to occur during January or February from 1993-2015. Even though
the upwelling is always rooted to the NKBs, the position, spatial
extent, and intensity of the upwelling exhibit considerable interannual
variability. The confluence zone between the Somali Current and East
African Coastal Current (referred to as the Somali-Zanzibar Confluence
Zone) forms during the Northeast Monsoon and is highly variable. We
present evidence that when the Somali-Zanzibar Confluence Zone is
positioned further south, it acts to enhance shelf-edge upwelling and
productivity over the NKBs. These findings provide the first indication
of the environmental controls that need to be considered when developing
plans for the sustainable exploitation of the NKB fishery.
Plain Language Summary The North Kenya Banks (NKBs) have recently
emerged as a region capable of sustaining a rich fishery, which would
boost Kenya's economy. Little research has been conducted on the
environmental controls that affect these fisheries and whether there is
annual variability over multiple years. Here an ocean model is used,
with satellite remote sensing data, to investigate how the ocean
influences this region. Specifically, the convergence of two currents
during the Northeast Monsoon, the Somali Current and the East African
Coastal Current, which meet near the NKBs and flow away from the coast.
This induces the upwelling of cold, nutrient-rich waters, which are
brought up from depth to the surface, resulting in the NKBs being a
highly productive area. The confluence of these two currents forms from
December to February and its position along the Kenyan coast varies from
year-to-year. This leads to considerable variability in the intensity,
position, and spatial extent of productive waters. Productivity is
enhanced over the NKBs when the confluence of the two currents is
generally positioned further south. These findings provide the first
indication of the environmental controls that need to be taken into
account when developing plans for sustainable exploitation of the
fisheries resources.
Συγγραφείς:
Jacobs, Z. L.
Jebri, F.
Raitsos, D. E.
Popova, E. and
Srokosz, M.
Painter, S. C.
Nencioli, F.
Roberts, M. and
Kamau, J.
Palmer, M.
Wihsgott, J.
