Τίτλος:
Productivity driven by Tana river discharge is spatially limited in
Kenyan coastal waters
Γλώσσες Τεκμηρίου:
Αγγλικά
Περίληψη:
The Tana River is the longest river system in Kenya (-1000 km) and
contributes - 50% of the total river discharge to Kenyan coastal
waters. The river discharges significant amounts of nutrients and
sediments, reaching -24,000 tons per day during the rainy season
(March-April), into Ungwana Bay (North Kenya Banks). The bay is an
important habitat for high-value Panaeid prawn species which sustain
important small-scale fisheries, semi-industrial bottom trawl prawn
fisheries, and is the livelihood mainstay in the surrounding counties.
In this study we analysed 20 years of satellite-derived chlorophyll-a
observations (Chl-a, an index of phytoplankton biomass), along with in
situ river discharge and rainfall data, to investigate if the Tana River
discharge is a major driver of local phytoplankton biomass in Ungwana
Bay and for the neighbouring Kenyan shelf. We find that during the rainy
inter-monsoon (March-April), a significant positive relationship (r =
0.63, p < 0.0001) exists between river discharge and phytoplankton
biomass. There is a clear time-lag between rainfall, river discharge
(1-month lag) and local chlorophyll biomass (2-months lag after
discharge). Unlike offshore waters which exhibit bi-annual chl-a peaks
(0.22 mg m3 in February, and 0.223 mg m3 in August/September), Ungwana
Bay displays a single peak per annum in July (2.51 mg m- 3), with
indications that river discharge sustains phytoplankton biomass for
several months. Satellite-derived observations and Lagrangian tracking
simulations indicate that higher Chl-a concentrations remain locally
within the bay, rather than influencing the broader open waters of the
North Kenya Banks that are mainly impacted by the wider oceanic
circulation.
Συγγραφείς:
Mutia, Damaris
Carpenter, Stephen
Jacobs, Zoe
Jebri, Fatma
and Kamau, Joseph
Kelly, Stephen J.
Kimeli, Amon
Langat,
Philip Kibet
Makori, Amina
Nencioli, Francesco
Painter,
Stuart C.
Popova, Ekaterina
Raitsos, Dionysios
Roberts,
Michael
Περιοδικό:
OCEAN & COASTAL MANAGEMENT
Εκδότης:
Elsevier Sci Ltd, Exeter, United Kingdom
Λέξεις-κλειδιά:
Tana River; Chlorophyll-a; Western Indian Ocean; Remote sensing
DOI:
10.1016/j.ocecoaman.2021.105713
