Hurricane Effects on Tropical Coral ReefsMegan LucasNortheastern State University

There are so many things to learn about involving the tropics. It seems as if there are a millions of different species. This ultimately means that there are lots of things that need to be taken into consideration when studying any one subject of the tropics. So many organisms rely on other larger species for food or shelter. Sometimes when something bad happens the affects only appear to have negative effects but in all reality they might actually have some positive effects as well that are just not as obvious. People tend to think that hurricanes are horrible and just ruin everything; while they can damage coral reefs, they can actually help coral reefs to survive as well. The effects that hurricanes have on coral reefs will be discussed in detail throughout this paper.

For a hurricane to even form, usually, the ocean surface temperature must be greater than 26°C. As the air moves across the surface of the ocean it takes in moisture and energy from the ocean. Low pressure takes air inward which results in the water vapor rising and getting cooler with increased elevation. The vapor eventually forms clouds and transfers heat energy to the neighboring air. The pressure of the ocean surface drops as the warm air rises which results in more air entering at the ocean surface; which in turn creates stronger winds and continues to transfer heat from the ocean to the atmosphere (Heron, Morgan, Eakin, Skirving 2009). Hurricanes are classified using the Saffir-Simpson Wind Scale. The following table shows how a hurricane gets classified.

Sustained Winds (MPH)
Types of Damage Due to Hurricane Winds
VERY DANGEROUS WINDS WILL PRODUCE SOME DAMAGE: roof damage to home, power lines and poles damage, results in power outages, large branches of trees will snap, and shallowly rooted trees will topple.
EXTREMELY DANGEROUS WINDS WILL CAUSE EXTENSIVE DAMAGE: roof and siding damage, shallowly rooted trees will be uprooted, near-total power loss lasts several days to weeks.
DEVASTATING DAMAGE WILL OCCUR: snapped trees, electricity and water unavailable for days to weeks, major damage to homes.
CATASTROPHIC DAMAGE WILL OCCUR: homes can sustain severe damage, trees will be snapped or uprooted and power poles will be downed, area will be uninhabitable.
CATASTROPHIC DAMAGE WILL OCCUR: framed homes will be destroyed with roof and wall collapse, area will be uninhabitable for weeks or months.
(National Oceanic and Atmospheric Administration 2013) The simplified version of a hurricane is that it takes in warm ocean water and redistributes it into the atmosphere leaving the ocean water cooler than what it was before. Hurricanes are good for species in the ocean that require specific temperature conditions.
Coral reefs first form when free-swimming coral larvae attach to submerged rocks or other hard surfaces along the edges of islands or continents (National Oceanic and Atmospheric Administration 2008). There are three main types of coral structures which are fringing reefs, barrier reefs, or atoll reefs (National Oceanic and Atmospheric Administration 2008). Fringing reefs encircle islands or border shorelines, barrier Reefs are much like fringing reefs but there is lots of ocean between the reef and the shoreline, and Atoll reefs are usually circular or oval(National Oceanic and Atmospheric Administration 2008). Atoll reefs used to be a barrier reef and then the island or volcano it encircled was submerged in water. Corals can reproduce sexually and asexually (National Oceanic and Atmospheric Administration 2009). Most corals are broadcast spawners, meaning they release their sperm or eggs into the water to distribute their offspring to a wide geographic area (National Oceanic and Atmospheric Administration 2009). There are a vast variety of growth forms of coral which include: table coral, branching coral, “massive” coral (which is not referencing size), and foliase coral; just to name a few. I have attached photos of these along with a brief description of each.
Table Coral. Photo Courtesy of National Oceanic and Atmospheric Administration
Table Coral. Photo Courtesy of National Oceanic and Atmospheric Administration

This type of growth pattern exposes lots of surface area meaning that there is greater area for light to access it. This determines how quickly the it is able to grow. Table coral is very delicate and can be broken easily with large, rough waves that come with a hurricane.

Branching Coral. Photo Courtesy of National Oceanic and Atmospheric Administration
Branching Coral. Photo Courtesy of National Oceanic and Atmospheric Administration

Branching corals are self-explanatory; they have many branches which includes secondary branches. The change in coral formation is related to the movement of the waves in the ocean as well as availability of sunlight. Corals that are closer to the surface of the ocean do not have to be spread out because they are getting direct sunlight whereas corals that are deeper in the ocean should cover a wide area that way they can still absorb sunlight.

"Massive" Coral. Photo Courtesy of National Oceanic and Atmospheric Administration
"Massive" Coral. Photo Courtesy of National Oceanic and Atmospheric Administration

"Massive” coral are very stable and not likely to be harmed by damaging waves. They are usually ball shaped and relatively slow growing.

Folias Coral. Photo Courtesy of Jen Uy
Folias Coral. Photo Courtesy of Jen Uy

There are many spaces in between these petal like structures, this serves as areas of shelter for animals small enough to get into the somewhat tight spaces. The folds in this type of coral increase its surface area, much like the table coral in that way.

PROBLEMCAUSES OF CORAL BLEACHINGCoral reefs require very specific conditions to survive and be able to continue to thrive. Some conditions they require include: specific water temperature ranging from 23-29°C, specific levels of salinity anywhere from 32 to 42 parts per thousand, and consistent water clarity and light levels throughout the year. If these specific conditions are not maintained, corals become stressed and begin to expel their symbiotic zooxanthellae (National Oceanic and Atmospheric Administration 2012). Zooxanthellae is a photosynthetic algae that has a symbiotic relationship with corals, and are responsible for the colors that stony corals can be. Zooxanthellae are the reason corals have to be in clear water. Temperature increases, reduced salinity, sediment smothering, and/or increased ultra-violent irradiation can cause corals to expel their zooxanthellae which can eventually lead to coral bleaching if the conditions are not reversed. Coral bleaching has negative impacts, making colonies more susceptible to mechanical damage, disease, and/or mortality (Mallela, Crabbe 2009). Once corals are bleached, recovery is a slow process. Corals are not only facing one problem anymore; they are undergoing multiple disturbances simultaneously for the first time (Mallela, Crabbe 2009) which is reducing the resiliency of many coral reef ecosystems (National Oceanic and Atmospheric Administration 2012).

While hurricanes have both positive and negative impacts on corals, the worst of the two will be discussed first. Large, powerful waves that hurricanes cause can break apart or flatten large coral heads and scatter fragments (National Oceanic and Atmospheric Administration 2012). Not only does this break the corals it can also lead to sedimentation; this results in the ocean water being cloudy and not clear like coral reef environment must be to be able to thrive due to zooxanthellae requiring light for photosynthesis. This will basically cause coral reefs to starve because zooxanthellae require light to be able to generate food by the process of photosynthesis. If zooxanthellae aren’t producing food then the coral reefs become starved and this is just another stressor that is put on them.
As discussed earlier, coral reefs must maintain a temperature range from 23-29°C. Although corals can continue to thrive outside these limits for short periods of time, corals begin to bleach when temperatures stay outside that range for longer than said short period. Once a hurricane forms it takes up the warm water from the ocean surface and leaves behind cooler water changing the waters that are too warm for corals and bringing the temperature of the water back to their desired temperature range. And, while hurricanes can break coral, this can actually result in a positive effect for corals. If a piece of coral is broken off it can eventually form a new colony if is ends up in a suitable place (Tunnicliffe 1981). This in turn could lead to growth of new corals increasing their current population. Reattachment can occur in two different ways: live coral can continue to grow and touch where coral had broken off and fallen or fallen coral can be reattached to an underlying foundation thanks to the many organisms that prosper on corals (Tunnicliffe 1981). It seems as if the good outweighs the bad, in this situation. This can lead to the spread of corals, which would be very beneficial to them because their numbers a beginning to dwindle. But, this will do no good unless something is done about the underlying problems.
Coral reefs cover less than one percent of Earth’s surface, yet one quarter of all ocean species rely on them for something, whether is be food or shelter (The Ocean Portal Team date unknown). Some species which rely on coral reefs include fish, lobsters, clams, seahorses, and sea turtles just to name a few (National Ocean and Atmospheric Administration 2013). Some of these fish are plankton eaters, others feed on corals, and there are also “grazers” which ingest algae and other ocean vegetation (National Geographic date unknown). Coral reefs are food webs of their own. Larger fish such as sharks can eat on the fish which eat on the plankton eaters. Without coral reefs animals as well as many organisms will begin to die off and this has a negative effect on humans because some humans rely on these types of animals for food as well as for many other things. It is absolutely amazing how everything seems to be interconnected.
WAYS TO PROTECT/SAVE CORAL REEFSThe following video is one person’s attempt to “regrow” corals and in turn encourages fish and other wildlife to come feed and thrive on the artificial corals. This is an attempt to draw tourists to visit this area rather than other coral reefs to help and keep them alive and growing.

Although this is a good attempt to help the current coral reef population continue to grow, overall if global warming is not taken care of, even these corals that are being regrown will not be able to survive because of the temperatures of the water, unless they begin to adapt to the warmer temperatures of water and this can only happen if gradual changes are made, not drastic ones.

According to Schuttenberg and Marshall (2009), if action is taken using five strategies, coral reefs could be given the best opportunity to survive while responding to global climate changes. Those five strategies are discussed below, the first is that efforts are made to limit sea temperature increases to 2°C and maintain ocean carbonate ion concentrations (Schuttenberg, Marshall 2009). Limiting the sea temperature increases give the coral reefs a chance to survive because as studies have shown, a drastic change for any species is able to wipe that species completely out. If temperature changes are kept to a minimum, this in turn reduces the frequency and severity of bleaching events (Schuttenberg, Marshall 2009) which gives coral reefs a chance to heal in between bleaching events rather than get stressed and eventually just dying off.

The next strategy is to integrate resilience into Marine Protected Area Networks (Schuttenberg, Marshall 2009). Including the following into MPA networks can help MPAs play a role in supporting coral reef ecosystem resilience to mass bleaching: Refugia: which are sites with natural resistance or tolerance to mass coral bleaching, Representation and replication: MPAs should focus on all reef types and associated habitats at replicate sites, Connectivity: associating highly protected areas along with flourishing coral reefs can help the recovery at multiple coral reef sites, and Good Ecosystem Condition: maintaining high coral cover, abundant fish populations, and good water quality all support recovery (Schuttenberg, Marshall 2009).

The next approach to protect coral reefs is to reduce local stressors to build tolerance to bleaching (Schuttenberg, Marshall 2009). There are many things that cause coral reef stress including: water pollution, over fishing, and elevated tourism. When corals get stressed, this reduces their ability to repair an injury, fight off pathogens, or be able to fight against competitors (Schuttenberg, Marshall 2009). If water pollution was managed, fishing of coral reefs managed and decreased, as well as decreasing tourism; just these three things could help to protect and possibly lengthen the life of many coral reefs.

Protect, maintain or enhance the conditions that promote ecosystem recovery (Schuttenberg, Marshall 2009) is the fourth scenario to help protect coral reefs. Water quality standards, fishing managers, and reef managers need to make sure that conditions are best for coral reefs because when a coral first arrives and is trying to grow is the most susceptible time for it and because multiple stressors on coral reefs need to be limited as much as possible so that they continue to survive. Multiple stressors do not allow sufficient mending time for the coral reefs and this is ultimately when they end up just dying off.

The final approach to protect coral reefs is to engage stakeholders that rely on coral reefs (Schuttenberg, Marshall 2009). The more people that know about a problem the more likely they are going to do what they can to help and spread the word. There are so many uses for coral reefs including: shoreline protection, production of compounds for new medications, people relying on them for food, coastal problems, and their livelihoods (Reef Resilience date unknown).

Hurricanes can damage coral reefs but, they actually help coral reefs survive as well. Climate models predict that tropical cyclone storms are likely to be more intense due to global climate change (Kleypas, Hoegh-Guldberg 2009). Global climate change is obviously something that has already begun, but people can make a difference. Just because things are bad does not mean that they have to continue to be. There are ways to help prevent further damage to our environment and atmospheric conditions which all have an effect on coral reefs. Hurricanes are only a small fraction of the cause of coral reefs being harmed; there are a whole slew of other causes including anthropogenic or threats caused by humans that can all be prevented or at least reduced. It would be amazing if all people would think about what is happening and what is going to happen to our environment if something doesn’t change. It may not happen in our lifetime but that doesn’t mean that we can’t make changes now so that our nation and Earth can continue to be a place to live. Humans are the ultimate cause of coral reefs being harmed because the things we do on a daily basis affect and have caused global warming which is in turn affecting coral reefs. We, as humans need to take positive action, because there are many things that we can do to prevent further damage to coral reefs.

Here is a link to check out that I saw 07-21-2013 on yahoo news: This is just another way that Americans are disturbing the oldest coral reef around, The Great Barrier Reef off the coast of Australia. It's a good thing that the bombs didn't explode, that would have caused major sedimentation along with just destroying the corals with an explosion. This could have been an extremely devastating event for the oldest coral reef around.
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Last edited by author: 7/23/2013 @ 1520 M. Lucas