Sint Maarten Nature Foundation Scientifically Assess Coral Reef Impacts Post Hurricanes Irma and Maria Using GCRMN Standards

The Sint Maarten Nature Foundation has started to scientifically monitor the state of the country’s coral reefs after the passing of hurricanes Irma and Maria in September. With financial support made available by the Dutch Caribbean Nature Alliance the Foundation has started to research the state of the Country’s coral using the GCRMN method; “Reef monitoring is conducted every year to determine the health, composition and state of our reefs. We did our last monitoring in August right before Irma so we have good information which we can use to compare the impacts that the coral reefs have experienced. Right after the storms and since then we did some qualitative measurements but in the coming week using the GCRMN method we will be able to scientifically establish what those impacts are,” commented Nature Foundation Manager Tadzio Bervoets.

The Nature Foundation surveyed mainly dive sites in the Man of War Shoal Marine Protected Area and other important dive sites around the island. All measurements are conducted along a transect line and repeated five times on one dive site. First, abundance and biomass of all fish species is determined, secondly the cover of reef organisms (corals) are analyzed based on photo quadrats made during the dives and photo quadrats are assessed for coral health. Monitoring is also done looking for coral recruitments (juvenile corals) and algae coverage and height. Lastly, invertebrate species (sea urchins, sea cucumbers, lobster and conch) are counted and water quality is measured. These measurements will help better understand the impact Hurricanes Irma and Maria has had on Sint Maarten reefs. The method will also allow for the comparison between reefs on SInt Maarten and in the region.

“Coral reefs are critical to the economy of the island. Studies conducted by the Nature Foundation has shown that reefs contribute about USD$50 million to our economy annually so it is critical that we know their status and their ecological function after experiencing the strongest hurricanes on record,” concluded Bervoets.

Caption: Nature Foundation diver does research using GCRMN method (Michelle McNaught Photo)

70-95% of Some Coral Species on Sint Maarten Reefs Suffered Extreme Hurricane Damage

The St. Maarten Nature Foundation has been continuously monitoring coral reefs both inside and outside of the Man of War Shoal Marine Protected Area in order to determine the impact of Hurricane Irma. Intense impacts have been recorded on certain coral species and on the reef, however also some reef recovering has already been recorded.

Acropora coral (Elkhorn and Staghorn) were hit the hardest by Hurricane Irma: this particular group of species is very prone to intensive water movement and has caused large pieces to break off. Besides the major break-off of coral fragments, also large die-offs have been recorded in those particular coral colonies. Many parts of especially Elkhorn coral colonies (A. palmata) died, due to direct impacts of the swell or sediment cover, light reduction or water quality reduction.

About 80% of Elkhorn (A. palmata) coral colonies are affected by and have died off directly and indirectly due to Hurricane Irma on St Maarten Reefs. Staghorn (A. cervicornis) coral colonies have shown even more damage due to the storm surge; hardly any coral fragment have been found back and entire colonies have been wiped out. 95% of the Staghorn coral colonies have been destroyed by Hurricane Irma. No colonies have been found  or only small fragments remain.

The loss of these Acropora species will have large negative impacts on our reefs due to their importance as reef builders. Acropora corals decreased tremendously in the 1980’s and are currently already listed as ‘Critically Endangered’ on the IUCN Red List of Ecosystems and Species. Until the 1980’s Acropora coral species dominated the near shore zone of many Caribbean islands, including Sint Maarten. Even before Hurricane Irma these coral reef zones have almost disappeared from most islands in the region due to diseases, climate change, pollution and habitat destruction. The increased loss of these Acropora corals due to Hurricane Irma will have even larger negative effects on biodiversity, biomass of fishes, coastal protection and tourism.

Also Pillar coral (Dendrogyra cylindrus) colonies have been significantly affected by Hurricane Irma. Pillar colonies have been reduced with about 70% due to Irma. Colonies at the dive sites Mikes Maze and Hen and Chicks which were known to reach up to five feet are now reduced to not much more than a foot.

In order to qualitatively assess the reefs and the Man of War Shoal Marine Park, the Nature Foundation will start up reef monitoring according to the Global Coral Reef Monitoring Protocol (GCRMN) in the coming month. Data from before Hurricane Irma and data from last year will be used to determine the detailed impacts and damages on St. Maarten reefs.

Picture 1: An Elkhorn (Acropora palmata) coral damaged over 80% due to Hurricane Irma at the islands Hen and Chicks.

Picture 2: Only a little piece of Staghorn (Acropora cervicornis) coral is found alive in the Marine Park since the passage of Hurricane Irma.

Picture 3: An Elkhorn (Acropora palmata) coral with many broken off branches found in the Man of War Shoal Marine Park.

Picture 4: Pillar (Dendrogyra cylindrus) coral colony which is chopped down by 70%.

Nature Foundation Assesses Marine Park and Dive Sites

Due to Hurricane Irma causing significant damage to underwater life because of storm surge and strong water motion, the Sint Maarten Nature Foundation conducted initial Marine Park and Dive Site assessment to determine the level of impact underwater. Initial marine assessment was carried out from the 28th of September until the 6th of October 2017.

Several St Maarten dives sites in the Man of War Shoal Marine Park and around the island have been surveyed for reef and coral damage, marine life presence and to assess the mooring systems for dive operators. The Nature Foundation will start in depth reef monitoring in the coming weeks to determine detailed impacts.

Hurricane Irma impacted St Maarten reefs severely; large coral and sponge die offs have been recorded, especially in the lower parts of the reef. Shallower dive sites experienced direct major damage to branching corals such as Elkhorn coral (Acropora palmata). Large coral fragments have been broken off. The large and branching growth form of Elkhorn corals makes them vulnerable to strong water motions and surge.

Major indirect impacts are found on the reef and to corals due to sediment and sand cover. The strong surge and water motion of hurricane Irma caused sand and sediment to move over the reef and cover mainly deeper sections and mainly coral and sponges show large die offs. Rapid assessment s have estimated a 30% die off of the reef due to sediment cover and a total of 50% of the reef being affected by Irma generally. Especially in the Man of War Shoal Marine Park turf algae and macro algae have been ripped off the reef due to the strong surge underwater. Turf algae are the main food source for several reef fish and the disappearance could impact fish stock negatively.

Seagrass beds around the island have decreased drastically, probably ripped off by the strong current or covered by sediment, it could be a potential problem for sea turtles and other marine life which depend on it as a food source. Mainly the invasive midrib seagrass (Halophila stipulacea) disappeared; native seagrass species survived the storm more often, such as turtle grass (Thalassia testudinum) and manatee grass (Syringodium filiforme), probably due to their larger growth form and strong roots.

Fortunately several marine species were found in good health on our reefs, including sharks, stingrays, sea turtles, reef fish, octopus and morays. The Nature Foundation is very pleased to have recorded quite a lot of sea turtles surviving the hurricane. Interesting is the occurrence of sharks on our reefs, three weeks after the storm no sharks were recorded yet, however four weeks after the storm sharks were back to normal abundance. This shows that sharks are most likely looking for hurricane shelter in the deeper waters and after return to their normal habitat.

Despite the reef and coral damage, St Maarten dive sites are still great for scuba diving because of the remarkable marine life and surroundings. The Foundation still highly recommends St Maarten as a dive destination and encourages visitors to return to scuba dive. The Nature Foundation is aware of three dive boats surviving the storm and dive schools are encouraged to start operating in the near future.