Is there a relationship between proximity to sewage effluent and the prevalence of coral disease?

Kaczmarsky, Longin; Draud, Matthew; Williams, Ernest

The relationship between prevalence of various coral diseases and exposure to sewage is studied in this report. This was done using transects and a significant relationship was found. We studied the prevalence of black-band disease (BBD) and white plague type II (WP) in two sites (Frederiksted and Butler Bay) within a St. Croix coral community that varied in relative exposure to sewage outflow. During sewage discharge events, fecal coliform and Enterococci data indicated impact area was limited to Frederiksted. We gathered data from seven belt transects in each of the two sites during the summer of 2001. We sampled 1046 colonies in 343 m2 in Frederiksted and 2399 colonies in 302 m2 in Butler Bay. There was significantly (Chi-square: df =1, p =0.0001) more disease in the impacted site with 13.6% of colonies of locally susceptible species infected (n = 566) versus the up current site that had 3.7% (n = 1344). Prevalence was highest for Diploria clivosa, with 23.7% of total colonies (n = 76) infected in the sewage impact site, which was significantly (Chi-square: df = 1, p = 0.0001) more than in the Butler Bay site where only 2.5% of the total colonies (n =320) were infected. Recorded mortality, due to WP type II, was most severe for Dichacaenia stokesi with 26% of the infected colonies (n = 38) dying in just two months or 9.4% of the total D. stokesi sample population (n = 107). The results of the study suggest a relationship between a high prevalence of BBD and WP type II and exposure to sewage.

Is there a relationship between proximity to sewage effluent and the prevalence of coral disease?

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