Wednesday, November 19, 2014

The Oyster Man Appears!

 It's freezing cold here just like many parts of the United States.
That doesn't stop Derby and Julep from barking at the oyster
man working the creek harvesting oysters.

Ecosystem Roles

Oysters are filter feeders, consuming phytoplankton (free-swimming algae) and improving water quality while they filter their food from the water. As generations of oysters settle on top of each other and grow, they form reefs that provide structured habitat for many fish species and crabs. The Chesapeake Bay was once known for its abundance of oysters. Much of their recent decline was due to decades of overharvest and habitat destruction. More recently, two parasitic diseases, MSX and Dermo, have devastated the remaining oyster populations in most areas of the Bay and its tributaries.
It has been estimated that oysters were once able to filter all the water in the Bay in about a week. The sharp decrease in the number of oysters means that it now takes the current oyster population about a year to filter the same amount of water. Because the oyster serves such an important function as a filter feeder, it has been hypothesized that their decrease has contributed to an apparent shift in the food web in the Bay, and an increase in zooplankton (which also eat phytoplankton) and their predators (ctenophores and jellyfish).
Two recent field studies in the Chesapeake Bay, one involving restored oysters and the other involving a small, naturally occurring bivalve, demonstrated the potential for filter feeders to improve water quality. A study partially funded by NOAA and done by the Maryland Department of Natural Resourcesrestored a small oyster reef in the South River on Maryland's Western Shore and did intensive water-quality measurements to look for improvements near the oysters. The results showed improvements in both chlorophyll and turbidity levels near the oysters when tidal flow was occurring, as expected, although the improvements were less than those predicted by models.
 Derby doesn't eat oysters ... but he barks at the men who
take our oysters from the creek.

Oyster Reefs
At one time, oysters were so abundant in the Chesapeake Bay that their reefs defined the major river channels. The reefs extended to near the water surface; to stray out of the center channel often posed a navigational hazard to ships sailing up the Bay. Now, after decades of damage to reefs from harvest, increased disease, falling salinity due to the increased runoff that accompanies increased impervious surface, and increased sedimentation from runoff, a significant amount of hard bottom habitat has been lost. The oyster population in the Bay is less than 1% of what it once was.
Degrading water quality is both a cause and an effect of the oyster decline, because fewer oysters means less filtration capacity. But oysters, as hardy as they are, can be killed by prolonged periods of low dissolved oxygen at the Bay's bottom.   
Keep warm and be safe.

1 comment:

  1. I would hate to be out there on that water in the freezing cold