However, too much fertilizer in lakes, rivers or sounds can encourage harmful algal blooms, which smother and kill underwater vegetation and fish as the algae die and decompose, depleting the water of oxygen. A 2008 Nature paper estimates that almost one-half of the world’s population depends on synthetic nitrogen-based fertilizer to enrich crop soils. In the early 1900s, the Haber process established a method for chemically converting inactive nitrogen gas to ammonia, which can be converted to nitrates for fertilizers. Fertilizer came from manure or nitrogen-fixing crops such as peas. Active nitrogen was not created except by an occasional lightning strike. There was a time when bioavailable nitrogen was locked in a cycle, much like the water cycle. If fertilizers are applied in excess for farming and residential use, they may cause problems in nearby waters. Nitric oxide occurs in the exhaust of internal combustion engines. In the past 100 years, humans have dramatically altered the nitrogen landscape. Nitrogen can be a problem when it’s in the concentrated form of fertilizer or nitric oxide. Nitrogen is the most abundant gas in the air we breathe and the gas generally is inert. These microbes - that live in and on the sediment associated with the shellfish - are active in recycling nitrogen.Ī thriving community co-exists with oysters on a sanctuary in Pamlico Sound. In a North Carolina Sea Grant study, Michael Piehler and graduate student Ashley Smyth at the University of North Carolina at Chapel Hill found that unseen organisms also flourish around oyster reefs. While fish flourishing around an oyster reef is an obvious benefit to ecosystems, a more subtle way that oyster reefs improve habitat is through nitrogen recycling, or converting nitrogen waste products into atmospheric nitrogen. Finfish use oyster reefs as refuge and nursery. The living reefs are placed just offshore of marshes where they provide spawning and nursery area for blue crab, shrimp and clams. He and other volunteers with PenderWatch also are active in creating living reefs along shorelines using recycled oyster shells. Each ball supports dozens of living oysters and other wildlife, such as tiny crabs and grass shrimp that find homes in the crevices. Before long, a sphere of oysters has formed around the recycled shells. He revels in describing “spat by the millions, just looking for a place to settle.” He makes necklace-like strings of old oyster shells and suspends them in the water below his dock. Spruill, vice president of PenderWatch and Conservancy, experiments with growing oysters on all kinds of surfaces - not for eating, but for the environmental services they provide, such as water filtration. But the oyster does not have a true brain - just one or two aggregates of nerve cells located near the hinge region. When the mature shellfish detects a shadow passing, it rapidly closes up. Jack Spruill ponders oyster spat’s propensity to settle on the unlit side of surfaces.
“Imagine what it’d do if it had a brain.”
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