Gulf of Guinea is a hotspot of multiple stressors such as marine and maritime pollution, climate change and overexploitation of aquatic resources. Nevertheless, we know very little of the effects of these stressors on tropical marine environment. This lack of knowledge hampers the efforts for sustainable management. HOTSPOT targets the degradation of the coastal environment in Ghana, its causes and its socio-economic consequences.
Threats to coastal marine ecosystems
Coastal marine ecosystems worldwide are threatened by multiple human-induced stressors, ranging from global stressors such as climate change, to local pollution, habitat loss and over-exploitation of resources. This results in fast degradation of coastal ecosystems and the services that they provide.
The consequences of this environmental degradation are potentially catastrophic – both for the diversity of marine life and for the millions of people who depend on marine resources for their livelihood.
Need for efficient management of activities
Regaining and maintaining a good environmental status requires efficient management of different activities which influence the oceans – which is a great challenge considering the number and diversity of threats, and the different vulnerabilities of ecosystems.
Management efforts are currently hampered by the lack of knowledge on the spatial and temporal overlap, relative importance, and ecosystem effects of different multiple stressors – in fact, the cumulative impact of multiple stressors was recently suggested to be one of the most important research questions in marine systems.
Gulf of Guinea – hotspot of multiple stressors
Gulf of Guinea large marine ecosystem is a hotspot of multiple stressors. The threats to this ecosystem include both organic and solid waste from domestic and industrial sources, hazardous substances originating from mining and oil exploration and diverse pollution from maritime activities, including oil and invasive species from ballast water as well as small- and large-scale coastal infrastructure projects. Together with the effects of climate change and overexploitation of aquatic resources, they put an intense pressure on the environment of the Gulf.
Coastal waters of Ghana suffer from e.g.
- elevated levels of heavy metals
- PAH compounds and hazardous chemicals in sediments
- high concentrations of marine litter on the beaches
- unsustainable artisanal and industrial fisheries
- warming of the surface waters
- habitat loss and potential altering of coastal currents.
Different industrial and domestic land-based pollution sources combine with global stressors and maritime pollution, which include oil, heavy metals and litter from the ca. 2500 ships which daily sail in the area, and heavy metals and petroleum hydrocarbons resulting from accidental spills and operational discharge from offshore oil exploration.
How do multiple stressors act together?
Maritime contaminants, land-based pollution and climate change can result in unknown synergistic, antagonistic or additive effects to marine life.
Straightforward causal relationships between contaminant concentrations and biological effects on biota are difficult to establish. For instance, trophic status and complexity of the food web can have large effect on how oil impacts the pelagic system, and synergistic effects among different heavy metals or PAH compounds can have detrimental effects on plankton at concentrations which are hundred times lower than if the organisms are exposed to a single metal.
Plastics can add to these harmful effects by facilitating the bioaccumulation of pollution in a variety of exposed organisms, although the magnitude and effect of plastic as a vector are still unknown.
Marine pollution bill in Ghana
In 2018, Ghana passed a marine pollution bill which strives to prevent the pollution by oil, noxious liquid substances, harmful substances carried by the sea, sewage, and garbage and air pollution from ships, in accordance to the regulations by International Maritime Organisation(IMO).
However, lack of regulatory capacity, and data of maritime and marine pollution for research-based management, result in challenges in implementation and enforcement of the regulations.
Gaps in knowledge
There are relatively few studies on the effects of toxic substances on aquatic organisms in the tropical environment, no studies on cumulative effects either at an individual or community level, few studies on the mechanisms behind species responses, and no overview of the proportional importance or spatial or temporal overlap of different stressors in the coastal waters of Ghana.
Similarly, the consequences of coastal degradation for the local communities or the alternative livelihood strategies have not been addressed.
These gaps-in-knowledge need to be filled to promote ecosystem-based management, advance marine conservation and increase the resilience of coastal communities to environmental degradation in the coastal waters of Ghana.