Bounties of Lake Victoria


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Pollution and its destructive effects on marine resources such as coral reefs, mangroves, fish, humpback whale, sea turtles, seaweed, seagrass, to mention but a few, is today a major concern with clarion calls to conserve marine life growing louder by the day. It is for this reason KMFRI went all out to conduct near shore survey to establish the impact pollution has on marine environment, investigate marine biodiversity of multiple areas and check nutrients levels and porosity by examining water samples and sediments. Of interest is also organic matter and benthos (the flora and fauna found on the bottom, near the seabed or in the bottom sediments of sea or lake). This community of aquatic organisms lives in or near marine sedimentary environments. They include starfish, brittlestars, oysters, clams, sea cucumbers and anemone.

Research scientists collect core for sampling

The objective of the survey, carried out at Malindi Kenya Wildlife Service Marine Park in August 2018 was to conserve marine or aquatic environment. “Ecosystem stressors which disrupt aquatic organisms emanate from land-based sources and mostly include increased nutrients, sediments and toxicants,” KMFRI Senior Research Officer Dr Eric Okuku, who is also Mombasa Centre Director, said.

Need to protect ecosystems

Mangrove forests are breeding grounds for fish, shrimp, crab and molluscs, an important source of food for coastal communities. Mangroves protect shorelines from storms and hurricane winds, floods and waves, help prevent erosion by stabilizing sediments with their tangled roots. They also maintain water quality and transparency, filter pollutants and trap sediments originating from land.

Research was carried out by KMFRI research scientists at multiple locations within KWS Marine Park in Malindi for estuarine, seagrass and mangroves.

The marine park ecosystem is impacted by sediments flowing from the Sabaki River and successful completion of sample examinations will help establish the source of pollution and impact it has on our environment. This survey stems from the realisation that land-based pollution such as waste from manufacturing industries, which finds its way to our oceans, coastal development, erosion, chemical and oil spills, impede reproduction of corals, disrupt ecosystems, change dynamics and feeding behaviours of fish, and shorten mortality of other marine species.

“Corer sedimentation helps project the impact of pollution and the source, and using the data generated we can work backwards to even 100 years ago to establish when pollution started and advise relevant stakeholders accordingly,” Dr Okuku said. “Radioisotope will be used to track pollution in water,” he added. KMFRI has state-of-the-art radioisotope lab.

The data generated will be submitted to state corporations namely Kenya Wildlife Service, Kenya Fisheries Services and National Environment Management Authority, among other state offices, to inform policies and decision making processes.

“Plans are in place to carry out near shore survey monthly in Mombasa and quarterly in other coastal counties,” said Dr Eric Okuku.

According to Dr Okuku, examination of sediments collected around Kilifi County Fisheries, Madharini, Sabaki, among other locations will inform the source of pollutants and the period within which sediment has been accumulating.

Samples collected (water and sediment) and mud oysters will be examined to establish levels of salinity, temperature, nutrients present to know whether marine organisms such as coral reefs, seagrass, fish, among others can thrive in particular aquatic environments.

However, marine organisms such as corals, a critical breeding ground for fish, do not require nutrients to thrive.

“Because rates of carbonate production and bioerosion are similar, even modest increases in nutrient availability can shift a reef community from net production to net erosion”. Their treatment of the role of nutrients emphasizes light penetration and its subsequent diminution by phytoplankton blooms that are driven by nutrient increases. By the time the reef is buried by sediment, it is already dead or dying.

“Water turbidity, for example, affects coral reefs with increased turbidity limiting amount of light reaching seagrass which slows down photosynthesis,” said Assistant Research Officer, Oceanography Athman Salim.

The survey will also establish seagrass carbon sequestration; the ability of seagrass to sink carbon to know carbon credits required for seagrass. The data will assist in identifying nutrients found in particular areas.

The components of sediment will also inform if chlorophyll A, phytoplankton and zooplankton, usually food for fish, are present in a given marine environment. High levels of the organisms indicate high fish productivity and findings help in mapping of fishing zones, information that is critical in advising fishers on areas with fish abundance.  

According to Darwin (1842), deposition of sediments checks the growth of coral reefs. Dr Okuku added that high sedimentation flattens seabed destroying important marine life such as seagrass, destroying fish breeding grounds.