As we begrudgingly accept the fact that sargassum weed is now a long-term aspect of marina management in the Caribbean, we are investigating solutions to most effectively minimise its impact.
The sargassum enters through our flushing channels, but blocking these channels that serve the inner and outer marinas is not an option. Not only will it create a huge buildup of the weed outside the marina, the flushing channels serve the important purpose of creating a flow of fresh water through both the marinas.
The Inner Marina, although sargassum does enter through the flushing channel, tends to be self-purge reasonably well.
The outer marina needs a little more help. Many of our marina guests will have seen our chase boats tied to docks with their engines running and in gear to create mobile flushing stations. While this is effective it’s not an efficient or cost-effective long term solution.
We are currently testing marine de-icers or circulators from Canada. These units better known as bubblers are submerged thrust de-icers that use an impeller system to create movement of water. This water agitation inhibits ice formation near structures, shoreline, and boats.
We have four high-thrust units to test and will be running them along the main walkway to create a flow along the inside of the marina. Not only will we be testing them to see if they actually clear the weed, we will be interested to see how long they last in a Caribbean saltwater environment.
Where is it coming from?
“Initially, the source was thought to be the Sargasso Sea, dubbed “The Golden Floating Rainforest”, which is estimated to hold up to 10 million metric tons of sargassum. It was assumed that sargassum was transported from the Sargasso Sea directly into the Caribbean on ocean currents moving in a south westward trajectory. However, by back-tracking the movement of sargassum from its first mass stranding locations in 2011 with the use of ocean models, satellite trackers, and examining high resolution satellite images, scientists are now convinced that the recent influxes to the Caribbean Sea and along the coast of West Africa are related to massive sargassum blooms occurring in the equatorial area of the Atlantic where the ocean currents rotate in what oceanographers call the North Equatorial Recirculation Region (NERR), an area which is not directly associated with the Sargasso Sea and is essentially a new ‘source’ region for sargassum.
“Factors believed to be contributing to the anomalous quantities of sargassum in this region include warming ocean temperatures due to global climate change and increasing discharge of nutrients (nitrogen and phosphorus) into the marine environment from land-based sources, which are allowing rapid growth of the seaweed.
“In addition, fluctuations in the strength of the recirculating currents in the NERR driven by increasing fluctuations in major climate indices are allowing a cycle of build-up and subsequent release of large quantities of the seaweed which then travel north westwards up into the Caribbean Sea with the complex and seasonally variable surface water currents (North Brazil and Guiana Currents).”
Source: https://www.cavehill.uwi.edu/principal/getattachment/17762/Sargassum-Management-Brief.pdf.aspx
