. Coast watch. Marine resources; Oceanography; Coastal zone management; Coastal ecology. By Daun Daemon In the winter months, some clams brought in from North Carolina waters sport a different look: green gills. The condition is nothing new — clams here have probably occasionally worn green for millennia. But this greening can cause problems for seafood markets because most folks shy away from the shellfish, believing they are inedible. Biologists have traditionally explained that algae on the gills caused the discoloration — not a palatable thought. When Skip Kemp, Sea Grant's regio
. Coast watch. Marine resources; Oceanography; Coastal zone management; Coastal ecology. By Daun Daemon In the winter months, some clams brought in from North Carolina waters sport a different look: green gills. The condition is nothing new — clams here have probably occasionally worn green for millennia. But this greening can cause problems for seafood markets because most folks shy away from the shellfish, believing they are inedible. Biologists have traditionally explained that algae on the gills caused the discoloration — not a palatable thought. When Skip Kemp, Sea Grant's regional seafood marketing specialist, decided to investigate the issue, he found that the French consider green-gilled oysters a delicacy and pay premium prices for the nuttier tasting, oddly colored creatures. Kemp learned from Jean Prou, a coastal zone manager with the French Institute for the Exploitation of the Sea, that oyster farmers in France raise the shellfish in claires, ponds that encourage the diatom Haslea ostrearia. This single-celled alga, called "the blue diatom," synthesizes the blue pigment marennine. "Haslea releases marennine into the water, giving it a bluish tinge," Kemp says. "Oysters pick up the water-soluble pigment in their gills as they filter the water for food. When the blue combines with the animal's natural yellow color, the gills turn ; Like oysters, clams are filter feeders, so the greening process is the same for these shellfish. The French have grown the oysters for centuries, and their scientists are currently studying Haslea in hopes of improving the. Skip Kemp culturing process. According to Kemp, no one really understands why the Haslea blooms occur in colder months or which factors contribute to them. For example, the diatom will flourish in one claire but not in another nearby with the same conditions. To test whether North Carolina's waters hosted the diatom, Kemp collected samples from Topsail Sound
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