Elsevier

Marine Pollution Bulletin

Volume 42, Issue 12, December 2001, Pages 1264-1278
Marine Pollution Bulletin

Kenya

https://doi.org/10.1016/S0025-326X(01)00241-7Get rights and content

Abstract

The Kenya coast is bathed by the northward-flowing warm waters of the East Africa Coastal Current, located between latitudes 1 and 5° S. With a narrow continental shelf, the coastal marine environments are dominated by coral reefs, seagrass beds and mangroves, with large expanses of sandy substrates where river inputs from Kenya's two largest rivers, the Tana and Athi rivers, prevent the growth of coral reefs. The northern part of the coast is seasonally influenced by upwelling waters of the Somali Current, resulting in lower water temperatures for part of the year. The coast is made up of raised Pleistocene reefs on coastal plains and hills of sedimentary origin, which support native habitats dominated by scrub bush and remnant pockets of the forests that used to cover East Africa and the Congo basin. The marine environment is characterized by warm tropical conditions varying at the surface between 25°C and 31°C during the year, stable salinity regimes, and moderately high nutrient levels from terrestrial runoff and groundwater. The semi-diurnal tidal regime varies from 1.5 to 4 m amplitude from neap to spring tides, creating extensive intertidal platform and rocky-shore communities exposed twice-daily during low tides. Fringing reef crests dominate the whole southern coast and parts of the northern coast towards Somalia, forming a natural barrier to the wave energy from the ocean. Coral reefs form the dominant ecosystem along the majority of the Kenya coast, creating habitats for seagrasses and mangroves in the lagoons and creeks protected by the reef crests. Kenya's marine environment faces a number of threats from the growing coastal human population estimated at just under three million in 2000. Extraction of fish and other resources from the narrow continental shelf, coral reef and mangrove ecosystems increases each year with inadequate monitoring and management structures to protect the resource bases. Coastal development in urban and tourist centers proceeds with little regard for environmental and social impacts. With a faltering economy, industrial development in Mombasa proceeds with few checks on pollution and other impacts. In 1998 Kenya's coral reefs suffered 50–80% mortality from the El Niño-related coral bleaching event that affected the entire Indian Ocean. The institutional, human resource and legal infrastructure for managing the coastal environment has in the past been low, however these are rapidly improving with the revitalization of national institutions and the passing in 1999 of an Environment Act. Marine Protected Areas are the key tool currently used in management of marine ecosystems, and focus principally on coral reefs and biodiversity protection. New initiatives are underway to improve application of fisheries regulations, and to use Integrated Coastal Area Management (ICAM) as a framework for protecting marine and coastal environments.

Section snippets

The Coastal and Marine Environment

The Kenya coast is slightly over 500 km long, between latitudes 1 and 5° S (Fig. 1). It forms the northern extreme of the tropical East African coast, which stretches another 3500 km south through Tanzania and Mozambique. Northwards, the Somali coastline extends a further 1500 km, with a transition from the warm water environments of the East Africa coast to the seasonal upwelling system of the Somali current. The Kenya coast is variously identified as part of the Somali Current Large Marine

Physical and Chemical Oceanography

The Kenya coast is bathed by waters of the East African Coastal Current (EACC), formed by the northward deflection of the Southern Equatorial Current when it hits the African mainland in southern Tanzania and northern Mozambique. The EACC flows northwards throughout the year, accelerated during the SEM when reinforced by the prevailing winds to speeds of 0.5–0.75 m/s, and slower during the NEM when the monsoon winds blow counter to the current, at speeds of <0.25 m/s (Obura et al., 2000a). At

Major terrestrial habitats

Kenya's coastal plain is dominated by scrub-bush in the south, growing on ancient limestone rock and sedimentary deposits, and bushy grasslands in the north (UNEP, 1998). Historically, coastal forests were part of extensive networks of forests extending across East Africa to the Congo basin. The climatic regime, dominated by up to five dry months in the year, has been stable for up to 30 million years and has resulted in unique forest communities with high drought resilience and high levels of

Coral bleaching and global climate change

Coral reefs along the entire coast of Kenya suffered widespread bleaching and mortality of corals during the first half of 1998 (McClanahan et al., 2001; Obura, 1999) as part of the worldwide bleaching of corals following the 1997–98 El Niño (Wilkinson et al., 1999; Goreau et al., 2000). Sea surface temperature anomalies in March to June 1998 rose to 2°C above normal, unprecedented for the Kenya coast (Fig. 4, Obura et al., 2000a). Coral bleaching is one of the most dramatic environmental and

Management and Protective Measures

Kenya's legislation for protection of the marine environment goes back several decades to the 1960s and before, due to its strong commitment to protection of wildlife and natural habitats, and evidenced by the elaborate detail in the Fisheries Act on trout fishing and management. These laws reflected the dominant political reality at the time, which was of the inherited colonial legal structure and a newly-independent country borrowing strongly from colonial laws that emphasized control by the

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