Coral heads dislodged and piled in a mound of rubble along a reef off Nassau following Hurricane Matthew in 2016
(photo credit: Craig Dahlgren)
Over the past few weeks we have been reminded of the sheer destructive power of hurricanes and how our climate is changing. Both of these interconnected issues are intricately tied with the past and future of coral reefs, and the species that depend on them – including our own.
As tropical marine systems, hurricanes have helped shape the evolution and development of coral reefs. When reefs are healthy and resilient, hurricanes may play an important role in spreading corals through fragmentation, where pieces broken off the main colony can naturally reattach to the seafloor and regrow. On healthy reefs damage to coral colonies that become dislodged or “sand blasted” by moving sediments may open up space for coral larvae to settle and grow, increasing diversity of corals and reef structure. The problem with hurricanes that reefs face now is that their ability to recover from impacts have been impaired. Fragments of broken off colonies often fail to reattach or get smothered by algae on reefs, and dead pieces of coral are rapidly overgrown by algae or allow species to that contribute to reef erosion to become established. The result is that reefs may not recover from hurricanes and can rapidly decline, changing the habitat to unsuitable for many of the fish and invertebrates that live there. People are also affected. Degraded coral reefs can’t support fisheries the way healthy ones can and as reef structure declines, reefs can’t protect coastal communities from shoreline erosion and flooding.
As our climate changes, reefs are under increasing threats so that even relatively healthy ones may be faced with severe declines. Over the past decade we have numerous examples of widespread loss of corals globally due to increased sea temperatures. Add to this the prediction of increased frequency and intensity of hurricanes. Hurricane impacts may become too frequent for reefs to recover or may cause damage too severe for recovery for decades or even centuries. And yet, coral reefs are not without hope. Marine parks and protected areas may increase coral reef resilience so that reefs can recover from these impacts. Coral restoration may also be a means to help reefs recover from these impacts and new techniques show promise for further recovery.
Over the next few weeks, the Perry Institute will be assessing the damage inflicted by Hurricane Dorian to reefs around Abaco and Grand Bahama. This will include assessments of reefs that saw a range of impacts from Category 1 to Category 5 strength winds and were exposed to different amounts of wave energy. It will also include reefs that were in different condition before the storm and may be more resilient than other reefs. This information will be used as a baseline for monitoring recovery of these reefs and determining how these reefs may be managed in parks and other protected areas and restored to increase their resilience.