Marine Pollution and Research in the Coastal Lagoons of Kenya.

Item Type Book Section

Authors Nguta, C.

Publisher Swedish Agency for Research Cooperation with Developing Countries (SAREC)

Download date 27/09/2021 11:23:19

Link to Item http://hdl.handle.net/1834/7152 Marine pollution and research in the coastal lagoons of Kenya

Dr Mweu Nguta Kenya Marine and Fisheries Research Institute, Mombasa, Kenya Abstract Marine pollution in the coastal lagoons of Kenya originates princi­ pally from land based sources and other activities within the marine environment. Although the extent of industrialization is relatively low, discharge ofliquid wastes into the sea has been reported. Solid wastes, both domestic and industrial, including toxic chemicals are dumped in the uncontrolled landfill at Makupa Creek. Leakage from the landfill, including run-off containing toxic substances, enters the adjoining creek waters. Contamination of sediments by heavy metals has shown enrichment factors ranging between 1.2-7.8. Only 20 % of the population has sewage disposal and, although localized, the discharge in biochemical oxygen demand. (BOD) is estimated to be 3.52 ton/year/km coastline. This amount can easily be assimilated by the high dilution with sea-water. However, with the increasing population and the future extension of sewerage plans, sewage discharge will become a major area of concern. Agricultural chemicals, pesticides and fertilizers have reached the lagoonal waters through river transportation and land run-off. The Galana-Sabaki river system has caused heavy siltation with adverse effects on coral reefs and tourist beaches. Oil pollution from frequent spills in the port have been estimated to 10 tons/day, resulting in values between 0.1 mg/l and 7.0 mg/l in the water column. The water quality around Mombasa is not seriously affected by the oil due to thorough mixing of the water mass. Tar balls have been observed on tourist beaches in concentrations ranging between 0-18 grn/m2 which appears to be influenced by the monsoon season. Other sources and types of pollution exist along the coastal ivaters on a localized basis but the levels are not significant. The responsibility ofall research pertaining to marine environment 2, falls under the Kenya Marine and Fisheries Research Institute .v (KMFRI). Very little marine pollution assessment has been under­ p .v < 86 ~ taken. The rruljor constraints are shortage ofskilled rrulnpower, lack of analytical equipment and ageneral lack offunds. Through bilateral agreements with foreign governments and assistance from United Nation agencies some rrulrine training and research has been undertaken. Initial results from these programmes and from others conducted earlier, indicate that the state of pollution is not very serious but assessments and monitoring of the situation should be intensified.

Introduction The coastal lagoons along the 500 km long coast of Kenya extend from about 10 38' 5 to 40 37' S. The lagoons are located between the beaches or the cliffs of the mainland and the off­ shore fringing reefs. They run continuously parallel and close to the shore, except for occasional breaks at the mouths of estuar­ ies and creeks. The lagoons are approx. 1-2 km wide with depths of up to 10 m. The lagoon waters are cillm, characterized by high biological productivity and act as habitat and nursing grounds to a great variety of fish species. Often beds of seaweed and seagrass colonize the lagoon floor, Cyrnodocea being the most abundant species. In addition, apart from playing an important ecological role as habitats to some molluscs and copepods coral-sand beaches are a major tourist asset, especially when combined with the marine life of the coral reefs. From the foregoing it can be understood that these coastal ecosystems offer valuable socio-economic resources and multifunctional benefits, which must be protected from the harmful effects of pollution that result from a variety of human activities.

Marine Pollution Marine pollution along the Kenyan coast is at present limited to a few specific areas and originates principally from land-based sources and other activities within the marine environment. The types of pollution caused by various transport routes are either physical, chemical, microbiological or aesthetic. A qualitative overview of the marine pollution situation in Kenya has recog­

2 nized the existence of these problems, although the levels are o still moderate (Norconsult, 1975). Most of the industry in the coastal zone is concentrated to the

~• western mainland of Mombasa (Fig. 1). Liquid and solid u o C wastes, both domestic and industrial, are discharged without v

·< Malindi and Lamu and the z ·,• u expansion of existing ones in Mombasa, the problem is ex­ o pected to increase. "u ·• 88 The population is mainly occupied by agricultural activities which invariably contribute significantly to pollution. Use of agricultural chemicals, pesticides and fertilizers is widely practised, replacing traditional and less efficient farming methods. River transportation of agro-chemicals, by land run­ off during the rainy season, is the main pathway to the marine environment for these chemicals. Persistent and ecologically harmful chemicals such as organochlorines, organophosphorous, insecticides and herbicides are used in large quantities at food-, sugar cane- and cotton plantations. The strong coastal currents off the reef reduce the concentra­ tions of suspended solids to acceptable levels. Near-shore waters show a total nitrogen value of 100 mg!l and total phos­ phate ranging between 10-15 mg!I. Creek waters show slightly higher values. These low concentrations are typical of clean unpolluted waters. Due to soil erosion the Galana-Sabaki river system is heavily silted, causing high siltation on beaches at Malindi and possibly adverse effects on tourism. Kenya imports about 2,000,000 tons of crude oil every year. Hence, oil pollution of the coastal environment is of major concern due to its possible effects on tourism. Major sources are oil tankers flushing their tanks at sea, or accidental spills. Frequent spills are common in the Kilindini harbour during operational transfer of oil from oil tankers to the storage recep­ tion facilities. Oily waste water from the refinery at Mombasa containing effluents of 100,000 m3! day is discharged into the creek waters. Based on the IMO regulation of 100 mg!l of oil in refinery effluents, about 10 tons of oil is released daily around the coast of Mombasa. Between 0-7 mg!l of dissolved and dispersed hydrocarbons were recorded in creek waters, while these values ranged between 0.2-1.0 mg!l in open oceanic waters. The oil spills in the port do not affect the water quality along the coast north and south of Mombasa. A probable reason for this may be that the wind induced currents move the oil slicks in an inland direction, as evidenced by the oily sheen on the surface water in the mangrove areas. Some incidents of oil spill accidents have been recorded, the most serious occurring at Makupa Creek in July 1988 (Kitoyo, 1990). A punctured storage tank resulted in 4,000 metric tons of bunker oil being spilt into a 2 km enclosed body of water. As the accident occurred during spring tide, the contamination reached areas high above the mean tidal level, killing the entire mangrove vegetation. Other sources and types of pollution, though localized, are present along the coastline. Various major port development

89 activities involving construction, enlargement or dredging have been undertaken. Although no data is available, the activities invariably have detrimental environmental consequences on the creek and near-shore resources (GESAMP, 1980). In particu­ lar, dredge suspended sediments may interfere with light penetration in the water, exerting both a biological and a chemical oxygen demand (Johannes, 1975).

Research In Kenya the responsibility and management of all research related to the marine environment falls under the Kenya Ma­ rine Fisheries Research Institute (KMFRl). The institute coordi­ nates activities within the marine sector on a national and international basis. Only a few studies of marine pollution in the area have been conducted. Any studies undertaken have essentially been made on an ad hoc basis, carried out by a few researchers work virtually in isolation. There has been no comprehensive study of the area due to shortage of skilled manpower, lack of analytical equipment and a general lack of funds. Some studies of oceanographic conditions have been carried out on ocean outfalls and physico-ehemical characteris­ tics of the Kilindini harbour. Through bilateral agreements with foreign governments and assistance from United Nations agencies some marine training and research has been initiated. At present, two marine research programmes of multi­ displinary nature are running The first one falls under the UNEP/FAO"Assessment and Control of Pollution in the Coastal and Marine Environment of the East African Region (EAF/ 6)". Preliminary work on the first phase has started and some equipment has been received. The objective of the study is to provide useful baseline information on the physical, chemical, biological, and hygienic conditions of the area. At the end of the eighteen-month assessment period it is expected that concrete proposals of preventive, remedial and control measures will be instituted. The second marine research programme, which contains an aspect of marine pollution studies, falls within the framework of the Kenya/Belgium cooperation in marine science entitled "The Ecology and Assessment of the Kenya Mangrove Ecosys­ tems". The aim of this four-year pollution study is to assess the levels for heavy metals, organochlorines and petroleum prod­ ucts, as a basis for setting up future monitoring and research z ·,• programmes. u o o u

< 90 '"· Discussion The quality of creek waters differs from the near-shore ocean in the content of suspended materials. Creek waters have a higher turbidity and lower transparancy, as well as higher content of nutrients. The ecology of marine waters appears generally to be determined by natural processes and the influences of human activities are negilible. All waters are valuable as regards exploitable biological resources, with the exception of the immediate surroundings of port areas because of local pollution from marine traffic. In order to understand the state ot marine pollution of the Kenyan coast, the influence of tides, waves and other factors on transport, diffusion and mixing processes must be considered. The average tidal range of 2.3 m ensures that large quantities of ocean water is available throughout the year which reduces the concentrations of dissolved and suspended pollutants. The exchange between tidal creek waters and near-shore waters causes the pollutants to have a net transport into the open ocean. This is often observed by the discolouration of coastal waters for several kilometres during ebb tide. For these reasons the lagoons have a natural appearance but increased , I human activities are likely to have an adverse effect on fish communities. While there is sufficient subjective infonnation to conclude that pollution, albeit in varying degrees with respect to various beneficial uses, exists in the waters close to major population and industrial centres, there is a lack of quantitative data. Some data on some common criteria such as dissolved oxygen, bacterial counts and sedimentation exists in a number of governmental departments but there is a complete lack of systematic data on such pollutants as heavy metals and pesti­ cides. Linked to the lack of long-term physico-chemical data, is a dearth of biological knowledge. In fisheries research compat­ ible statistics are not easy to obtain, nor is the industry better provided with the necessary data on the quantity and quality of its discharges to the environment. Thus, wastes of unknown quality and quantity are being discharged into an ill defined environment.

z o Conclusions Although monitoring can be both necessary and valuable in most instances, it should be used to provide answers to inter­ pret levels in relation to effects on man. These answers must lie in research, education and legislation with scientists and policy .u ~ '" 91 makers working to prevent rather than measure and record pollution. The local authorities along the coast should develop research programmes in estuaries, creeks and near-shore waters to establish the necessary bench-mark data. National legislation (Laws of Kenya, 1972) dealing with a wide number of pollut­ ants should require all discharges, whether direct or indirect, to be monitored on a basis acceptable to a centralized national environmental secretariat. The impact of land-use and the distribution of tirban-, industrial- and tourist centres on the near-shore environment must be recognized and adequate provisions made to measure it. Such an all-embracing approach is necessary and is implied in the definition of the concept of "total pollution load". Finally, although the regulations of various sources of marine pollution, such as shipping, mining and other coastal develop­ ments may remain scattered between the various ministries, overall coordination of the various marine pollution control measures by KMFRI should be established to ensure unifonn policy.

References: 1. GESAMP (1980): Marine Pollution Implications of Coastal Area De­ velopment 11. 144pp. 2. Johannes, R.E. (1975): "Pollution of coral reef communities". In: Tropical Marine Pollution. Wood, E.J.F.; Johannes, R.E. (eds.). Elsevier. Oceanogr.ser., 12:13-51. 3. Kitoyo, A. 1990: "The situation in Kenyan ports with special regard to loading /unloading of tankers". Paper No.12. In: Regional seminar on MARPOL 73/78. Mombasa, Kenya, 29 Oct-2 Nov 1990. 4. Munga, D.; Delbeke, K.; Wynant, J. (1991): "Tourism, waste water, solid waste collection and disposal". Presented at the workshop: To­ wards Sustainable Coastal Tourism. 22-23rd April, 1991. School, J.; Visser, N. (eds.). Discussion paper. Commissioned by the Netherlands Ministry of Agriculture, Nature Management and Fisheries.. 5. Oteko, D. (1987): Analysis of Some Major Trace Metals in the Sediments of Gazi, Makupa and Tudor Creeks on the Kenyan Coast. M.Sc. Thesis. Free University of Brussels. VUB. 6. Norconsult, A.S. (1975): Mombasa Water Pollution and Waste Dis­ posal Study. Vol. 6. Marine Investigations. Republic of Kenya, Ministry of Local Government, Nairobi. 7. UNEP (1982): Regional Seas Reports and Studies. No.9. 8. Laws of Kenya (1972): In: Water and Fish Industry Acts. Govern­ ment Printer, Nairobi. Ch. 372 and 378. ·< ·J u ·o "u ·< 92 '"·