Dredging up the sea floor kills corals

F. Joseph Pollock

Dredging up the sea floor kills corals

Too little food and too much work can stress out corals and leave them vulnerable to disease. The most pervasive family of diseases, called white syndromes, strips corals to mere skeletons of their former vibrancy (as in the image above). A paper published this week in PLOS ONE shows that dredging, the act of shoveling tons of sediment from the sea floor to maintain beaches and build new land, contributes to the spread of diseases like white syndromes by placing corals under intense stress. Researchers used satellite images to study the effects of the Gorgon Project, which dredged about 7.6 million tons of sediment to clear a shipping channel. Corals that were exposed to sediment plumes from 296 to 347 days showed twice as much disease than corals that suffered little to no exposure. Dredging muddied the water, increasing turbidity and blocking out sunlight. Without sunlight, the corals’ symbiotic algae could not photosynthesize to provide the coral with essential nutrients. Sediment that blanketed corals also prevented them from suspension feeding and forced corals to expend energy on sloughing off the muck. Under these stressful conditions, the corals were more susceptible to disease. The researchers hope to further study exactly how diseases like white syndromes latch on to corals as coastal development continues.

Posted in Environment, Plants & Animals