St. Croix residents have wondered for more than a year what happened on the South Shore at Great Pond. Once there were healthy, lush green leaves of mangroves, now there are only dead branches silhouetted by the ocean.
The direct cause appears evident – high salinity in the pond. Julio Santiago Rios of Fish and Wildlife, V.I. Department of Natural Resources, tested the pond early last fall and found high salinity. He said that the pond registered about 60 parts per million of salinity while the mangroves tolerance level is about 50 parts per million.
His suspicion is that the lack of rainfall during a period of drought leading up to the death of the mangroves is responsible. Rainfall would flush out the pond and keep salinity down.
There is also another conjecture that the influx of huge amount of Sargasso last year blocked flushing of the pond and kept the salinity too high for the mangroves to survive.
One thing is certain: the mangroves at Great Pond have been devastated. John Farchette of St. Croix Marine Park, which oversees the area, says 80 percent of the mangroves there are gone. He says, “They are dead; you can bury them.”
Geographic Consulting recently did a survey of the mangroves there and other areas. Owner of the company Brian Daley says about Great Pond, “We saw a lot of dead trees. We had not realized the extent of what had happened.”
However, he is reassuring that the situation at Great Pond is unique. He says, “You look at Salt River and they are all fine there.”
In an interview Wednesday, Daley suggested another possibility contributing to the death of the mangroves. He said that his team did not see any Sargasso blocking the channel, but soil erosion could be blocking the flow of water through the channel.
He also responded to a question about the acidification of the oceans effect on mangroves. He says about mangroves, “They are very tough, not like coral.”
According to the National Oceanic and Atmospheric Agency, the acidity of the ocean has risen by 30 percent since the beginning of the industrial age. Acidity is caused by carbon dioxide released into the atmosphere.
No one interviewed saw leaf or trunk damage that would indicate an insect infestation or other disease.
According to the Geographic Consulting website, “The purpose of this study is to document the presence, health and structure of existing mangrove forest stands. To this end, we are taking measurements along transects that run perpendicular to the coast in order to capture the diversity and complexity of the mangrove forest.”
Daley indicated there is no reason to believe that mangroves, a key part of the Virgin Islands ecosystem, are in danger.
What might surprise island residents is what Daley says about black, red and white mangrove. “These tree species are not related, and the word “mangrove” is a description of their ecology rather than a distinct plant family.”
Even though his team found dead mangroves, Daley says, “We found really great wildlife like juvenile sharks and rays.”
More information about the survey can be found at