What are marine ecosystems?
Marine resources do not exist in isolation. They are part of a complex system called a marine ecosystem, which consists of all living things such as fish, corals and seaweed and non-living things such as the sea water and sand with which they interact. Humans are also part of the marine ecosystem.
Sunlight is used by very small drifting plants (phytoplankton) which are grazed on by small drifting animals (zooplankton). Larger plants and some animals such as corals and giant clams use sunlight to create tissue which is used by plant eaters, including rabbitfish. Other animals feed on the plant eaters so that food moves through the ecosystem and supports a huge array of living things as indicated in the figure above.
What is the purpose of protecting marine ecosystems?
Each species exists in a balance with the species that feed on it (its predators) and the one that it feeds on (its prey). There’s no point in protecting marine resources without protecting the marine ecosystems and habitats in which they live, including coral reefs, mangroves, seagrass beds and estuaries.
When and where should we protect ecosystems?
A survey, completed by Fisheries authorities in Pacific Island countries and territories, captured the negative effects of non-fisheries activities on the marine environment, including reclamation, siltation, waste disposal, eutrophication (depleted oxygen), pollution and the inadequate treatment of effluent. All of these can affect food webs and key habitats, such as nursery and spawning areas.
Threats and possible remedial actions are detailed below under the headings of the key ecosystems of coral reefs, mangrove areas, seagrass areas and estuaries.
> Coral reefs are one of the most productive ecosystems in the world and support a wide range of species, including corals, worms, crabs and fishes. Damage occurs by using destructive fishing methods, siltation and the overgrowth of algae due to the presence of excessive nutrients.
An important step to improve water quality and marine ecosystem health is in reducing the amount of effluent from sewage systems and piggeries. The addition of these nutrients can result in eutrophication (low levels of dissolved oxygen) and kill fish in lagoon waters. Nutrient-using plants, such as bananas, can be planted near the drains or outflows from sewage systems and piggeries. Traditional destructive fishing methods, such as the smashing of corals to catch sheltering marine resources, should be banned as should the collection of corals for building materials.
- Mangrove areas are trees or shrubs that grow at the edge of the sea. As well as protecting shores from erosion, they provide food and shelter for many marine resources.
Community actions could include the banning of cutting mangroves for firewood and structures. The establishment of rubbish dumps in mangrove areas should
be banned.
In some cases, mangrove areas have been destroyed indirectly by the construction of coastal roads. Unless large pipes are placed beneath the road, mangroves on the seaward side of the road die in water that is too saline and those on the landward side die in water that is too fresh.
In many countries and territories, the demand for living space is high and coastal areas are under increasing threat. Many coastal wetlands and mangrove areas have been destroyed and converted to dry land for coastal development purposes.
There have been several attempts to re-establish lost areas of mangroves by planting seedlings. However, the reason for their original loss needs to be established and addressed before replanting.
- Seagrass areas form underwater meadows and provide essential habitats for many marine resources. Communities could close areas of seagrass beds to fishing and harvesting to create seagrass reserves.
- Estuaries occur where rivers meet the ocean. Here the water is often brackish due to sea water mixing with fresh water. Estuaries support a range of species such as crabs, prawns and the juveniles of many fishes.
Communities could ban the dumping of waste and rubbish in the mouths of rivers. Preventing the establishment of houses and farms close to the banks of rivers would also reduce silt and effluents entering rivers and estuaries.
Besides being unsightly, discarded packaging, typically plastic and polystyrene, can be harmful to marine species. Large fish and turtles often mistake litter for food then choke, as an example, on plastic bags, which resemble jellyfish.
How can we implement the protection of marine ecosystems?
Considering the degradation of ecosystems, fisheries managers are now taking a broader approach that attempts to manage fish habitats and ecosystems. This implies that non-fisheries activities impacting marine ecosystems must also be managed, particularly by communities.
Most marine ecosystems are under the mandate of multiple government departments and there should be an attempt to ensure that there is a coordinated approach to sustainable development and management of ecosystems.
What are the benefits, problems and limitations in protecting ecosystems?
Local actions to protect marine ecosystems are often very effective. However, actions taken at the community level may not address the problems caused by sources of silt and pollution from activities further away, including forestry, sand mining and reclamation. If the marine ecosystems are being affected by silt or other materials from one of these sources, the actions of local communities will have little effect without government involvement and cooperation.
Collaborative efforts are needed by the different government departments responsible for forestry, agriculture, fisheries and climate change to work together to address the sources of degradation of marine ecosystems. An ecosystem approach to fisheries management can ensure that sources of pollution, siltation and other land-based activities, are considered.
How do we know if protecting marine ecosystems is working?
Fisheries departments, agencies or communities could appoint a number of local people as community wardens to monitor actions required to protect their marine ecosystems. Local schools could also be involved in their monitoring and reporting on community actions taken.
What other management tools can be used to complement the protection of ecosystems?
Other methods of protecting marine ecosystems include the declaration of permanent closures. Closures can be declared to protect mangrove and seagrass areas as well as coral reefs, but these only work with the participation of communities, especially fishers, both men and women. Fishing on critical species which ensure the health of corals, such as parrotfish, should be reduced.
