Sci-Tech Information： Seagrass Cannot Survive If the Water Is Too Murky
Seagrass needs sunlight at the water's surface, but microorganisms can become so abundant that they block the light the plants need to survive.
Seagrass beds represent critical and threatened coastal habitats around the world. Loss of seagrass means fish, crabs, and other animals lose their homes and manatees and sea turtles lose a source of food.
Nutrients, such as phosphorous, may prevent seagrass from getting the sunlight it needs to thrive. Nutrients may come from a variety of sources, including fertilizers used in agriculture, golf courses and suburban lawns, pet waste, and septic tank waste.
Scientists often use seagrass to judge coastal ecosystems' vitality, says Chuck Jacoby, a courtesy associate professor in the soil and water science department at the University of Florida. "By protecting seagrass, we protect organisms that use seagrass and other photosynthetic organisms that need less light."
When nutrient levels are too high, microorganisms in the water, called phytoplankton, use these nutrients and light to grow and reproduce until they become so abundant that they block sunlight seagrass needs to survive, says Zanethia Choice, a former graduate student who led the investigation.
SURFACE SUNLIGHT
"Seagrass can cope with short-term light reductions, but if those conditions last too long or occur too frequently, seagrass will deteriorate and ultimately die," Choice says. "Good water clarity is vital for healthy coastal systems."
For a new study published in the journal Marine Pollution Bulletin, Choice studied seagrass beds in a 700,000-acre swath off the coast of Florida's Big Bend.
The study combines 13 years of light and water quality data and two years of seagrass samples from habitats near the mouths of eight rivers that empty into the Gulf of Mexico and constitute part of the second largest seagrass bed in Florida. The largest bed is in Florida Bay, between the Everglades and the Florida Keys.
Choice wanted to see how much light was needed to keep the seagrass in the region healthy. Different seagrass species need varying amounts of light, ranging from 8 to 27 percent of the sunlight at the water's surface.
The study will give water resource managers, such as the state Department of Environmental Protection, water-clarity targets they can use to set proper nutrient levels for water bodies, Jacoby says.
Reducing nutrient levels can promote the health of seagrass and coastal waters. For example, concerted efforts to reduce nutrients flowing into Tampa Bay over the past 20-plus years resulted in a 50 percent reduction in nitrogen, a 50 percent increase in water clarity, and a return of lost seagrass, according to the Tampa Bay Estuary Program.
Unlike Tampa Bay, there is no evidence that elevated nutrient levels in the current study area have led to loss of seagrass. Researchers are trying to make sure nutrients don't pollute the seagrass beds off the coast of the Big Bend, and hope their results will guide managers as they work to prevent any damage.
sources: [http://en.twwtn.com/Information/26_65041.html]
Seagrass beds represent critical and threatened coastal habitats around the world. Loss of seagrass means fish, crabs, and other animals lose their homes and manatees and sea turtles lose a source of food.
Nutrients, such as phosphorous, may prevent seagrass from getting the sunlight it needs to thrive. Nutrients may come from a variety of sources, including fertilizers used in agriculture, golf courses and suburban lawns, pet waste, and septic tank waste.
Scientists often use seagrass to judge coastal ecosystems' vitality, says Chuck Jacoby, a courtesy associate professor in the soil and water science department at the University of Florida. "By protecting seagrass, we protect organisms that use seagrass and other photosynthetic organisms that need less light."
When nutrient levels are too high, microorganisms in the water, called phytoplankton, use these nutrients and light to grow and reproduce until they become so abundant that they block sunlight seagrass needs to survive, says Zanethia Choice, a former graduate student who led the investigation.
SURFACE SUNLIGHT
"Seagrass can cope with short-term light reductions, but if those conditions last too long or occur too frequently, seagrass will deteriorate and ultimately die," Choice says. "Good water clarity is vital for healthy coastal systems."
For a new study published in the journal Marine Pollution Bulletin, Choice studied seagrass beds in a 700,000-acre swath off the coast of Florida's Big Bend.
The study combines 13 years of light and water quality data and two years of seagrass samples from habitats near the mouths of eight rivers that empty into the Gulf of Mexico and constitute part of the second largest seagrass bed in Florida. The largest bed is in Florida Bay, between the Everglades and the Florida Keys.
Choice wanted to see how much light was needed to keep the seagrass in the region healthy. Different seagrass species need varying amounts of light, ranging from 8 to 27 percent of the sunlight at the water's surface.
The study will give water resource managers, such as the state Department of Environmental Protection, water-clarity targets they can use to set proper nutrient levels for water bodies, Jacoby says.
Reducing nutrient levels can promote the health of seagrass and coastal waters. For example, concerted efforts to reduce nutrients flowing into Tampa Bay over the past 20-plus years resulted in a 50 percent reduction in nitrogen, a 50 percent increase in water clarity, and a return of lost seagrass, according to the Tampa Bay Estuary Program.
Unlike Tampa Bay, there is no evidence that elevated nutrient levels in the current study area have led to loss of seagrass. Researchers are trying to make sure nutrients don't pollute the seagrass beds off the coast of the Big Bend, and hope their results will guide managers as they work to prevent any damage.
sources: [http://en.twwtn.com/Information/26_65041.html]
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