Sierra Leone - State of the Marine Environment 2015

7. Pests, introduced species, diseases and algal blooms

The Sierra Leone marine environment is overall in good condition with regards to pests, introduced species, algal blooms and outbreaks of diseases that can disturb the ecological balance of the aquatic realm. However, the problem of coastal and marine invasive species is likely to worsen over the coming decade due to increases in shipping activities throughout the region. Ship traffic is projected to continue growing into the coming decade with economic growth and therefore the outlook for transfer of alien organisms through ship‘s ballast water could be expected to grow. The Queen Elizabeth II quay is the primary international gateway for all foreign vessels entering into the country. There have not been documented any pest species from this quay or any of the wharfs to have caused any significant ecological impact in the local areas.There have been reports of malaria and such outbreaks, especially in coastal areas of high urbanisation and population densities, and these have been attributable to poor sanitation where mosquitoes have been able to proliferate in stagnant water settlements. The high risk areas for such incidents to happen are in

Outbreaks of diseases, non-natural algal blooms and infestations by pests have been assessed as symptoms of an unhealthy marine ecosystem. The results of research estimates indicate that a very high percentage of the pollution currently discharged into the coastal area is done by the local inhabitants. Untreated waste on beaches and in the nearshore zone is directly related to the health status of the local population. Epidemics such as typhoid fever, cholera and similar outbreaks are the results of poor sanitation or the symptoms of consuming raw or partially cooked oysters, clams and mussels harvested from coastal waters into which raw or inadequately treated sewage had been discharged (Meith-Avcin and Helmer, 1978). High concentrations of harmful nutrients and micro- organisms areusually contained inuntreatedand inadequately treated waste. Aquatic ‘over nourishment’ from nutrients may lead to eutrophication of coastal receiving water bodies like estuaries and bays bringing various negative consequences such as plankton blooms, oxygen depletion and fish kills. Such adverse circumstances are sometimes observed in the streams, rivers, and estuaries but they go unrecorded.

36