Oysters and Us

Lela Schlenker, our guide to the oyster reef, gill net in hand.

Yet again yesterday, our explorations reinforced connections between the well-being of Gulf Coast natural and social environments and those of us who live far from the shore. Our lessons came from a field excursion to some fledgling oyster reefs and from interviews with Dr. George Crozier, Executive Director of the Dauphin Island Sea Lab (DISL), and Dr. Sean Powers, who oversees research at the Lab related to oyster fisheries. Yes, and then there was also the oyster martini Nat and I enjoyed at the end of the day at the Oarhouse pub after witnessing another blazing Gulf sunset at the public beach on this lovely barrier island.

Lela Schlenker, a DISL lab technician, took us on a tour of the Lab’s experimental work to enhance oyster habitat in Mobile Bay and elsewhere in the Gulf. Like Apalachicola Bay, barrier islands that partially protect Mobile Bay from the open waters of the Gulf create an estuary, where salt water mixes with fresh water from the Mobile-Tensaw River delta (for more on the wonders of estuaries you can visit the earlier post, Cradle of Life: Introducing the Estuary). If you ever make it to Dauphin Island, don’t miss the Sea lab, which, in addition to carrying out extensive research on estuary environments, Gulf ecology, and fisheries management (when it’s not busy dealing with crises like the oil spill), also has a wonderful Estuarium as part of its many public educational efforts.

Part of DISL's oyster reef experiment: several oyster beds made from stacks of oyster shells in mesh bags.

Lela led us on a hike along a stretch of shoreline at low tide. Running parallel to us a dozen yards off shore a series of constructed oyster reefs were visible above the water. Laid out in grids roughly 30-feet long and 10-feet wide, the eight reefs formed a controlled experiment for determining which of three strategies create the best habitat for oysters while also improving conditions for multiple other species that thrive when the oysters thrive.

Sean Powers emphasized that oysters are an indicator species for estuaries, because they can’t pick up and find a new home when their habitats get degraded. Moreover, when they do well, their beds create habitat for other species and the oysters improve estuary conditions by filtering bacteria from the surrounding waters. Oysters also have been a mainstay for Gulf fishermen, because they are inexpensive to harvest using traditional methods and easy to find if stocks are good. For a glimpse into the family-oriented oyster fishing culture and traditional harvesting techniques in the Gulf, here is a video profile of Wayne Hicks, a third-generation oysterman from Apalachicola bay:

Traditionally, tiny oyster spat attach themselves to sub-surface piles of shells left by their ancestors where they grow to harvestable size within a year. But in many areas populations have declined due to several causes: pollution that can originate thousands of miles inland and is carried to the Gulf by inland waterways (the main problem in Mobile Bay), irregular flows of freshwater into estuaries from upstream dams (the biggest issue in Apalachicola Bay), and excess sediment from surface runoff that covers the shell reefs. When these things happen, oyster beds deteriorate and the little spat need help. DISL’s project is focused on determining which of three materials are best for rebuilding reefs. The experiment has proven that man-made oyster beds can enhance oyster populations, reduce shoreline erosion, and improve conditions for other species. Of course, reducing the sources of pollution and restoring freshwater flow levels into estuaries are also essential to the long-term sustainability of the oysters, the oyster fishery, and the estuaries that nurture oysters and fishermen.

Reef-building Materials (from left): ReefBlk (which get filled with oyster shells), Reef Ball (also filled with shells), and meshed bags filled with shells (the best, but most labor-intensive, solution).

As we discussed the overall health of Gulf coastal environments with George Crozier, the conversation had a way of returning to the impact of the BP oil spill. While oyster beds in Mobile and Apalachicola bays didn’t suffer a direct hit of oil from the spill, the precipitous drop in tourism and unfounded fears of tainted seafood, combined with the recession, have had what Crozier said are “catastrophic” impacts on the Gulf’s coastal communities.

Later, at the Oarhouse, Nat and I talked about the health of the Gulf’s oysters and oystermen while enjoying our oyster martini—a large martini glass filled with a half-dozen raw oysters on a bed of lettuce. Outside, the sky darkened after another amazing sunset display.

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2 Responses to Oysters and Us

  1. Brian says:

    I really appreciate your point about the connections between upstream pollution and the health of the Gulf. Is there a particular pollution source (agricultural? industrial? urban?) that is hurting the oysters, or is it just unclean water that’s the problem?

    The video is a great . Hopefully we can take the actions necessary to save this commercial fishery.

  2. John Shepard says:

    Thanks for your comment, Brian. The most common pollution sources impacting Gulf coast estuaries are what is called non-point pollution–that is, nutrients and other toxic elements that originate in small quantities from multiple sources. These include fertilizers from agriculture and urban landscaping, pesticides, animal waste, oil and gas from city streets and roads entering storm sewers, eroding sediment from farm fields and construction sites, leaking septic systems, and inadequate sewage treatment. All considered, in the Mississippi river system agricultural fertilizer from the Upper Midwest is the biggest contributor to poor water quality in the Gulf, and is the cause of the oxygen-poor “dead zone” near the Mississippi delta that is about the same size as the state of New Jersey

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