Eastern Oyster - Effects of The BP Deepwater Horizon Oil Spill

Effects of The BP Deepwater Horizon Oil Spill

Harvestable size of a C. virginica oyster is 75mm, which can take from 12 to 36 months, depending on temperature, salinity of the water, and food supply. Salinity is a very important climatological variable that affects spatfall. Oysters do best where salinities are from 10 to 30 ppt; 15 to 18 ppt is considered optimal. Typically, when salinity levels are less than 6 ppt, larvae will not settle and metamorphose into spat. In 2010, 665 miles of coastline were affected by the Deepwater Horizon oil spill. To keep the oil at bay and to spare the oystermen, the authorities of Louisiana made an unprecedented decision to maximize the fresh water flow through the region’s canals to three times usual levels. At the mouth of the canals, salinity fell to almost zero which was probably why most of the oysters died. Sujata Gupta ventured into the marshlands and Gulf of Mexico with Brad Robin, a man from a line of generations of oystermen in southeastern Louisiana. Robin and his crew threw a net over the side to haul in a catch. There were dozens of palm-sized oysters, but 75% of them were “boxes,” or empty shells. However, as they traveled further towards the Gulf of Mexico, where the water was less salinity stressed by the flush, only 20% of the haul came back as boxes, a promising sign the oysters are trying to come back. Gupta reports, “Now since there are so many empty shells scattered on the sea floor, the larvae have more to latch onto, improving their odds". However, salinity levels are not the only concern. Eastern oysters are filter feeders, so they are greatly affected by their surroundings since they are sessile organisms. This means that if the water around them was contaminated with oil and also the dispersant used to get rid of the oil, then these chemicals were collected by the oysters as they filtered the water. This is cause for great concern that the oysters are being killed by the toxins in the dispersant as well. An added dilemma is oysters are in their weakest state after spawning season, which may have caused some of them to close their shells, resulting in death by suffocation within just a couple of days due to warm temperatures in the Gulf if the shells remains closed. The toxins in the oil and dispersants can also kill the larvae.