August 2001

Vol. 16, No. 8     What's this?

The Truth About San Salvador’s Algae

from the August, 2001 issue of Undercurrent  

In our review of San Salvador Island, we noted that the reefs were covered with algae, which made them drab and uninteresting. We offered some scientific speculation about the cause, but long time dive manager Chris McLaughlin wrote to set me straight:

Thank you for your June 2001 story. I believe that you were accurate and fair, though we are actually 400 miles southeast of Miami. Algae-covered reefs are a long time phenomenon on San Salvador. When I first came here in 1975 there was a lot of algae already. It is more widespread here than most Bahamian Islands. The Bahamian field station thinks it is possibly caused by deep water upwelling of Amazon River effluent, brought up by oceanic currents. From December to mid-April, winter storms clean all the fluffy algae from the reef. After the last big storm front of the season this nasty stuff starts growing fast and covers the reefs until October/November, when the first cold front storms blow it off again. Unfortunately, there is less coral left each time. Hurricane Floyd acted like a cold front and cleaned off the algae for a couple of weeks in the summer. So, your theory doesn’t explain the steady increase of algae for 26 observed years, with hurricanes only in 1996 and 1999.