February 15, 2012

Volcano Poses Unique Threat to Montserrat’s Coral Reefs


By James Hewlett, Reef Check Montserrat Coordinator and EcoDiver Course Director

On January 6, 2012, a group from Finger Lakes Community College (FLCC) in New York arrived in the Caribbean nation of Montserrat to continue their work on a reef research project as part of the ongoing Research Integrating Molecular and Environmental Science (RIMES) program. The group was led by Professor James Hewlett, a Reef Check Course Director and Coordinator. Accompanying Hewlett as a Teaching Assistant was Ashli Roberts, a certified EcoDiver. Rounding out the team were students Courtney Stein and Barb Dagata, and Troy Depperman, Dwayne Daley, Oswald West, and Raphael White of Montserrat’s Green Monkey Dive Shop.

A rare streak of winter calm provided ideal conditions for conducting research and provided an opportunity for the team to organize a Reef Check survey. The team was able to add three new reef sites to the Montserrat survey program. The Reef Check data collected on Montserrat has been a valuable asset to the RIMES program and has been used in publications, consultant reports, and management recommendations submitted to the local government. It appears that the decline in hard coral cover measured over the past 10 years has stabilized and remains in the 8-15% range. Heavy fishing pressure, including pot fishing, continues to be a threat to the nearshore reef system on the leeward side of Montserrat. Of particular note was the addition of Montserrat to the growing list of Caribbean islands impacted by the invasion of Pterois volitans (Red Lionfish).

Montserrat’s reefs face an unusual threat due to its active volcano in the Soufriere Hills. Volcanic activity began in 1995 and continues to this day. A January and February 2010 collapse of the volcanic dome dropped more than 70 million cubic meters of hot ash and rock onto the landscape and out into the ocean on both the leeward and windward side of the island. Direct deposition of ash, increased erosion, and increased redevelopment activity has contributed to a substantial sedimentation load on Montserrat’s reefs. One of the primary objectives of the research program is to establish a monitoring protocol for all sources of sedimentation and ash deposition for each study site. While sedimentation and siltation sources are diverse and varied from site to site, sources of volcanic ash deposition can be categorized as either direct (pyroclastic flows and atmospheric deposition) or indirect (run-off/erosion, resuspension and redeposition). The Soufriere Hills volcano has been “quiet” with minimal dome growth since the 2010 collapses. This period of calm has contributed to a significant reduction in deposition of ash on Montserrat’s reefs.

Overall siltation and sedimentation rates on Montserrat’s reefs are believed to be very high due to the combined effects of intermittent deposition of volcanic ash following dome collapses and an above average sediment load due to erosion. Erosion in areas impacted by volcanic activity can be attributed to extensive deforestation, defoliation, and loss of vegetative cover. It is believed that sedimentation due to erosion has increased over the last five to seven years north of the exclusion zone due to the alteration of the landscape for development, road construction, and mining. This increased threat is exacerbated in northern areas of the island where there are regions of steep relief and soils that are erosive in nature. Using data from a variety of sources (sediment traps, rainfall and turbidity data, ash cloud data) the FLCC team has developed a six point estimate to assess frequency and load integrated over all sources of sedimentation. This data is then added to other measured sources of stress on Montserrat’s reefs in an attempt to quantify the effects of stress on the reef ecosystem. Utilizing the sedimentation data, the FLCC team is currently trending the robust Reef Check database from Montserrat in an effort to establish correlates of reef stress.