Coastal ecosystems and habitats

January 2, 2012

By Kent Gustavson
Raidho Resource Consulting Ltd.

Coastal habitats found in the Gulf of Maine include: salt marshes, mudflats, seagrass beds, kelp beds, shellfish beds, rocky and cobble shore, and sandy shore. The structure and function of coastal ecosystems are threatened by several pressures that can have important impacts. Increasing population, economic growth and coastal development lead to increased physical habitat alteration and destruction, increased contamination and pollution and an increased need for renewable resource extraction. This, together with the pressures from a changing climate, can alter physical and chemical environments, change the distribution and extent of coastal habitats, affect the distribution and abundance of species within coastal ecosystems, and reduce the provision of critical ecosystem goods and services.

Key biophysical changes of concern are: site energetics (wave and tidal action); nutrient loading; oxygen demand and availability; water turbidity (and availability of light); habitat fragmentation, and pollution and contamination with toxic chemicals. Overall coastal ecosystems are particularly susceptible to: effluent from wastewater treatment and outfalls; runoff and sedimentation from coastal development, forestry and agricultural activities; contamination from aquaculture facilities, and direct destruction of habitat through infilling and other activities that remove habitat from production.

Table 1 summaries the pressures, current status and impacts by habitat type in the Gulf of Maine.

Habitat type	Pressures	Status	Impacts
Salt marshes	Habitat alteration and destruction through coastal development Sea level rise Pollution and contamination	Salt marshes tend to be largest and most common in Nova Scotia, New Brunswick and Massachusetts. Salt marshes within the Gulf of Maine are declining. Within New Brunswick and Nova Scotia approximately 65% of salt marsh area has been lost since European settlement. Approximately 50% of salt marsh area has been lost in Massachusetts and 25-50% in Maine.	Pressures on salt marshes result in negative impacts on the ability of salt marshes to provide refuge and nursery areas for fish and shellfish species, as well as resting, feeding and breeding areas for birds and food for other animals. A reduction in the amount and quality of fish rearing grounds has a negative impact on commercial and recreational fisheries.
Mudflats	Pollution and contamination Navigational dredging Renewable resource harvesting	Information is not readily available for the distribution and spatial extent of mudflats.	Mudflats are important feeding grounds for birds and contain organisms that provide an important trophic link between primary coastal productivity and higher trophic levels. They support important commercial fisheries. Deposition and accumulation of contaminants in mudflats has an impact the harvest of species. Inputs of nutrients from agricultural and sewage sources can lead to massive growth of bottom algae, and the subsequent biological oxygen demand can further stress and have an impact on mudflat species.
Seagrass habitat	Changes in seawater properties (sedimentation; turbidity) Pollution	Eelgrass is the dominant seagrass species throughout the region and has been identified by Fisheries and Oceans Canada as an ecologically significant species. Seagrass habitats throughout the Gulf of Maine are thought to be in significant decline. It is estimated that eelgrass has declined 20% since European settlement.	Pressures lead to a reduction in the ecological functions provided by seagrass habitat. Specifically the ability for seagrass beds: to trap suspended sediment and reduce the load entering the marine environment from land; absorb dissolved nutrients; provide refuge, spawning, feeding and nursery areas for many species of fish and shellfish; serve as a source of vegetative detritus for marine filter feeding organisms; and provide habitat space for a number of coastal species.
Kelp beds	Storm events Changes in seawater properties (temperature) Renewable resource harvesting	Although there is no readily available information on the distribution and spatial extent of kelp beds, the deforestation of kelp beds is a general concern.	Impacts include loss of habitat, food source and key provider of primary production to the ocean waters.
Shellfish beds	Renewable resource harvesting Pollution and contamination Changes in seawater properties (temperature and acidification) Navigational dredging	Information is not readily available for the distribution and spatial extent of shellfish beds.	Fishing has a direct impact on the size, community structure and habitat structure of shellfish beds. Persistent organic pollution and metal contamination are also of particular concern to shellfish. Loss of shellfish beds can also lead to a loss of habitat.

There are many actions and responses in place to reduce the impacts on coastal ecosystems and habitats in the Gulf of Maine. These include: regulatory control of development, pollution and direct habitat disturbance; habitat protection and the creation of conservation areas; habitat restoration initiatives (The Gulf of Maine Council has developed a habitat restoration strategy); and environmental mapping and monitoring to inform adaptive management.

More detailed information is available in the theme paper. www.gulfofmaine.org/state-of-the-gulf/docs/coastal-ecosystems-and-habitats.pdf

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Tags: December 2011 Issue