REVEALING SECRETS ABOUT…
MARINE NURSERIES: An Essential Ecosystem Service
Marine Nurseries Keep the Oceans Bounty Flowing
Marine nursery areas provide an essential ecosystem service: essential for the oceans, and for us as well. Nursery areas allow a whole host of marine creatures to survive, are necessary to maintain the workings of coastal ecosystems, and provide for continued production of commercially and recreationally important fisheries. Yet marine nurseries are amongst the most highly threatened habitats on earth.
Care for the Young. Nurseries provide safe haven and ample food for the young of coastal fishes, crabs and lobsters, oysters, clams and other mollusks, and even far-ranging open ocean species like sea turtles and tunas. The production in these key areas is astounding: nurseries are literally teeming with young life. When nursery areas are lost or damaged, the species that rely on them suffer – as does the rest of the food chain, including human beings.
Fisheries. The most commercially important fisheries such as shrimp, lobster, crabs, oysters, clams, mussels, rely on intact nursery habitats. In 1999, the world marine fisheries catch was over 70 million metric tons – most of this directly dependent on nursery habitats. In the U.S., coastal fisheries are currently valued at $111 billion and provide approximately 1.5 million jobs.
Recreation. Global tourism is big business. In the U.S. alone, coral and other reef ecosystems support millions of jobs and billions of dollars in tourism each year. Reef-based tourism generated over $1.2 billion in the Florida Keys alone, while in Hawaii, annual gross revenues generated from just a single, half square mile coral reef reserve exceed $8.6 million. A majority of our recreationally fished species utilize nursery areas. Over 17 million people in the US participate in marine recreational fishing, generating billions of dollars in revenue. Coral reef based recreational fisheries alone generates over a $100 million annually.
Ecosystem Benefits. Intact and well functioning nursery areas provide a priceless service to all manner of coastal and marine ecosystems. They support species that help maintain the natural balance of the system and keep food webs stable and productive. When key species are removed, negative effects cascade through the system and the oceans become less productive. Nurseries also support critical populations of endangered or threatened species such as green sea turtles, lemon sharks, groupers, and shad, and are absolutely essential for their survival.
“Salt marshes, mangrove forests, sea grass meadows, and kelp forests are often called the‘nurseries of the sea’ since so many fish, shrimp, crabs and other creatures starttheir lives in these productive, food-rich environments. Without these nurseries, large
How Marine Nurseries Work
Nursery areas support the web of ocean life by providing food and refuge to vulnerable young of many marine, estuarine, and coastal organisms. Many of these species, in turn, are the source of prey for other fish and invertebrates that live in the open ocean or in other coastal areas.
The survival of these species underpins the survival of the oceans in general, since some play a critical role in maintaining ecosystem balances and productivity.
Marine nurseries are crucial for humans, too: worldwide, an estimated 95% of commercially valuable fishery species rely on nursery areas to live and reproduce. Water is the great connector – providing the lifeline that links rivers, land, and the oceans, through the crucial nursery areas in-between. Nurseries are found in estuaries, mangroves, seagrass beds, kelp forests, and coral reefs, as well as offshore areas like sea mounts.
What is Destroying the Earth’s Vital Nursery Areas?
Nursery areas are being lost or degraded daily, leading to the decline of commercially harvested species as well as the overall health of coastal ecosystems.
Freshwater Diversion. Human activities also impact nursery areas indirectly, by causing the alteration and degradation of distant habitats, especially through interference with water flow. Without freshwater input, estuaries can become hypersaline, losing the special attributes that make them suitable as nursery areas.
Pollution. Nursery areas are commonly affected by both point source and non-point source pollution. Perhaps the greatest impact is through eutrophication (sometimes called over-fertilization) from run-off or dumping of fertilizers, sewage, and other non-natural nutrients. Sedimentation is another form of pollution caused by run-off that dramatically alters nursery habitats by lowering light penetration, and by physically suffocating filter-feeding organisms. Additional pollutants borne by rivers into coastal areas include debris, heavy metals, hydrocarbons, and other persistent organic pollutants, which have toxic effects on fish and wildlife and sometimes even humans.
Invasive Species. Invasive species that are not natural to an area but are introduced to it, either accidentally or deliberately, are also a form of pollution. Invasive species of plants and animals often travel in the ballast water of ships, are discharged near ports, and then take a foothold in their new environs while displacing native species.
Over-exploitation of Resources. Resources that are key components of nursery habitats, such as mangrove wood or oysters from shell reefs, are often in high demand. Removal of these resources destroys nursery habitat and harvest of fishery species from nursery habitat can impact entire food chains to cause disruptions in marine ecology.
Climate Change. Climate change dramatically alters nursery habitat in a variety of ways. Global warming changes the temperature and salinity of estuary and nearshore nursery habitats, rendering them inhospitable. Warming can also exacerbate the problem of eutrophication, leading to algal overgrowth, fish kills, and even dead zones like the one in the Gulf of Mexico. Changes in weather patters caused by climate change, including increased precipitation in some areas, warming at the poles, and increased frequency and intensity of storm events, can all affect oceanic circulation and currents and the ability of organisms to access nursery areas.
This fact sheet is part of a series of materials on ecosystem services available through the Communicating Ecosystem Services Project of the Ecological Society of America. For more information about the project, contact:
Reference as: Ecological Society of America. 2010. Communicating Ecosystem Services: Marine Nurseries Fact Sheet - Revealing Secrets About Marine Nurseries Areas. Online at www.esa.org/ecoservices
Updated: August 24, 2010.