□ YSTER SCIENCE ON THE EDGE: 



REEF DESIGN 

 AND DISEASE 

 RESISTANCE 



By Ann Green 



AS THE TIDE BEGINS TD 



recede at Masonboro Sound in Wilmington, 

 Martin Posey and Troy Alphin trudge through 

 knee-deep water and mud. 



The North Carolina Sea Grant researchers 

 continue through the mud flat until they reach a 

 reef piled high with oyster shells. 



Built by Posey, Alphin and their students at 

 the University of North Carolina at Wilmington, 

 the created oyster reef has a high, zigzagged edge 

 with nooks and crannies. 



"The edge gives the fish a channel to swim 

 through," says Posey, chair of the UNC-W 

 biology department. 



The researchers built a total of 24 artificial 

 reefs, which vary in vertical height, edge and 

 complexity. 



The reefs are part of a Sea Grant project 

 focusing on how characteristics of intertidal reef 

 morphology, or shapes, affect fishery habitats. 

 UNC-W graduate students Heather Harwell and 

 Joseph Sonnier collaborated on the project. 



The dramatic decline in oyster reefs in 

 North Carolina and other states — coupled with 

 the rising recognition of biofiltration, habitat and 

 other ecosystem benefits of oyster reefs — has 

 led to increasing efforts to restore and conserve 

 oyster habitats in North Carolina and other states. 



In 2003, more than 260,000 pounds of 

 oyster meat was harvested at a value of more 

 than $1 .02 million compared to 724,000 pounds 

 in 1983 valued at more than $1.12 million, 

 according to the N.C Division of Marine 

 Fisheries (DMF). 



"Oysters may have greater economic 

 consequences than their value as a fishery," 

 says Posey. "Reefs provide critical habitats for 

 commercial and recreational species. The South 

 Atlantic Fishery Management Council and the 



6 AUTUMN 2004 



North Carolina Marine Fisheries Commission 

 have both declared oyster reefs to be an essential 

 fish habitat." 



After studying the reefs for two years, 

 researchers found that high complexity reefs 

 with numerous crevices were used more as blue 

 crab habitat than reefs with fewer crevices. These 

 reefs also were used more by species like pinfish 

 — which are food for other fish species — than 

 other reef shapes. 



Oysters settle on top of one another to 

 form clusters and build dense colonies, creating 

 habitats for up to 300 species of plants and 

 animals including, shrimp, speckled sea trout, 

 drum and rockfish. Healthy oysters also filter the 

 water and help to cleanse estuaries of suspended 

 materials, resulting in the removal of excess algae 

 and vegetation growth. 



REEF EDGE 



In addition, the reef edge affects local cur- 

 rents, as well as the flow of organic matter and 

 amount of nutrients inside and outside the reefs. 



The edge disrupts the flow and filtration, 

 leading to the deposition of organic nutrients 

 in and around the reefs, possibly increasing the 

 amount of food for bottom animals eaten by fish 

 and blue crabs, Posey says. 



These findings have implications for fishery 

 management. 



"In reef restoration for fisheries, we need 

 to pay attention to how the reef is constructed," 

 Posey adds. "All reefs aren't the same. More and 

 more reefs are being used for habitat restoration, 

 much like salt marshes are used to restore 

 habitats." 



In the reef restoration project, the scientists 

 left a channel between the reefs instead of 

 constructing one continuous reef. 



Continued 



