How Hurricanes Impact The Reef

As rainy season approaches every year, thoughts of possible hurricane activity are not far behind. This is especially the case after last year's close run-in with Hurricane Mitch. Hurricanes are a common part of life in the Caribbean, causing damage (even death) and significantly impacting the inhabitants of affected countries. What may be less known are the effects hurricanes have on the coastal ecosystem, particularly the coral reef.

Typically, in the Caribbean, the hurricane season starts in June, reaching its peak in mid-August, and lasting through late October. A hurricane is a type of tropical cyclone that develops over tropical waters, gathering heat and energy through contact with warm ocean waters. As moisture is evaporated from the sea surface and is incorporated into the storm, a developing hurricane becomes what is described as a "giant heat engine."

Hurricanes reach the shores of countries, such as Belize, with the help of easterly trade winds and temperate westerlies. Fortunately, the presence of the barrier reef helps to reduce the strength of extremely powerful waves that accompany hurricanes, decreasing the impact experienced on the shoreline. But what does this constant pounding of waves and exposure to winds do to the coral reef?

Opinions vary in regards to the effect of hurricanes on the reef. Some believe that tropical storms may provide a benefit to the reef ecosystem, clearing the reef of dead organisms and even enhancing bio-diversity. In some instances, segments of branching corals that were broken off and scattered by waves settle, reproduce, and start new colonies. Substrates that have attached to reefs are sometimes cleared by strong storms, leaving new surfaces for coral larvae to grow on. There are even reports in Florida that areas affected by black band disease have been cleared of the disease, leaving behind healthy coral. Still, others believe that the effects are much more significant and often very destructive.

Reef Brief is a weekly column published in the San Pedro Sun
After Hurricane George hit the Florida Keys last year, evidence of damage to the reef could easily be detected. The obvious damage (reported by the Florida Keys Tourist Development Council) could be seen as sponges and sea fans ripped from their bases appeared on the shores of beaches. Many areas of reef were reduced to rubble, thus eliminating habitat for many sea creatures. Hurricane winds and waves shattered branching elkhorn and staghorn corals and entire communities of corals, sponges, and seagrass were smothered by sand driven by powerful winds. Furthermore, strong storms increased the circulation and re-suspension of sediments into the water column. The presence of sediments often raises the nutrient level of the water, stimulating algae growth, eventually smothering corals. Sediments also decrease the visibility of the water, reducing the amount of sunlight penetrating the water column, thus hindering the growth of corals.

There has not been much research done on the impact to the reef due to Hurricane Mitch, but the effects were probably comparable to that of Hurricane George. For the most part, damage to the coastline, as well as to corals can be rehabilitated, as long as we limit other impacts. Coastal development and other potentially damaging activities make this ecosystem more susceptible to the impacts from natural disasters. As we all know, Belize and its people are incredibly fortunate that Hurricane Mitch chose a different path. But all reports point to the fact that this year will again be an active year for hurricanes. Fortunately, Belize's reef is still considered healthy, so even in the event of a hurricane, it would likely make a strong comeback.

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