Thursday, March 26, 2015

Research on the Reef (Or How I Learned to Love the Oyster)

I am in Marineland, a town south of St. Augustine, covered in muck, standing on an oyster reef offshore. My dingy garage-sale kayak, which I have recently dubbed the “Oystercatcher” (potentially a tongue-in-cheek name amusing only to me) sits unceremoniously nearby, full to the brim with random pieces of equipment – muddy work gloves, needle nose pliers, zip ties, lengths of rebar and PVC pipe. I free the buckets I’ve lashed to the back of the boat with fluorescent green lengths of nylon rope. This is one of several trips I have taken to test the design of sediment traps, constructed from said buckets and netting, which I will use for my research. Over two weeks, I will relate what the oysters produce as faeces and pseudofaeces (rejected food particles), collectively called biodeposits, to inorganic matter in the surrounding waters. I will use this to reveal how much and how fast these bivalves filter feed.

My boots after just two trips to the reef!
   These oysters on first glance are not beautiful to look at. The collective snarls of shell are what I lovingly refer to as 'nature’s little razor blades', and represent a challenge for unwitting boaters. However, these shellfish truly are one of the multi-taskers of the coastal world. The masses of oyster reefs along coastlines serve to protect against the battering of the many storms that pass through Florida, or the gradual erosion that cuts away at local shorelines. They sequester carbon by locking it away in their bodies and more permanently into the structure of their shells. Oysters are considered a keystone species, and are lauded as being “ecosystem engineers” for their ability to shape and provide new habitat for a veritable plethora of organisms including shrimp, crabs, mussels, barnacles, and polychaete worms. Often this diverse community stimulates other creatures who feed on or benefit from the reef, including many species of fish coveted by the local fishermen, as evidenced by the smattering of fishing boats nearby. At reefs off of a nearby sight known as Devil’s Elbow, I’ve watched adult and juvenile dolphins stir the water into a froth as they engage in what is known as strand feeding on the adjacent mud flats.

One of my sediment trap prototypes.
But some of the more salient functions of oysters relate to their role as filter feeders. Their ability to positively affect water quality has been the impetus for many restoration projects.  Through the use of my sediment traps, I am hoping to shed light on the local linkage between oyster filtration and the control of phytoplankton - masses of microscopic plants whose populations wax and wane with a variety of environmental factors, but whose growth can boom substantially when excess nutrients are present in a system. When phytoplankton abound in a region, less light is available for sea grasses and other submerged vegetation, and dissolved oxygen may become a scarcer commodity as well. In some regions, oysters may be a significant part of the components controlling this unchecked growth. 

So while I pull off my work gloves and start to collect my things in expectation of the incoming tide, I pause. Delicate little shore birds nimbly navigate over the reefs, feeding between the crevices, while hints of silvery scales break the water’s surface nearby. I begin to remember why I love what I do and what a bastion of life these oysters are. 

Example of a fringing reef hugging the shoreline of a tidal creek.

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