Exploring the Effect of Development on Coral Reefs


Image: SVII surveying over a coral reef in the Maldives

 

 

Living on the doorstep of a coral reef

 

I first visited the Maldives with my family in 1997 as a newly certified SCUBA diver ready to explore the underwater environment and I was amazed by the huge amounts of fish life and vivid colors of the reef. The news of the 1998 bleaching event in the country, causing mass mortality of corals, triggered me to pursue a career in marine biology and conservation and it is therefore a great privilege to be involved with bringing the Catlin Seaview Survey to the Maldives to survey this coral reef nation.

 

The Maldives is one of the most vulnerable nations to the effects of human induced climate change.  The imminent threat of sea level rise is a reality for the island nation, creating the need for landfill in large sections of reef flats to make islands bigger and higher above predicted sea level estimates.

 

The Maldives is also an extremely popular tourism destination, welcoming over 1 million tourists last year alone. Many tourists come to experience the pristine beaches and extraordinary coral reefs, however tourism comes at a cost with increased development on resorts and increased fishing pressure for the insatiable appetite for reef fish.

 

The main goal of my PhD is to see if developments in the Maldives are having an effect on the distributions of coral cover and the different types of coral found.  We are teaming up with the Maldivian Marine Research Centre and IUCN project Regenerate, with the hope that information from our surveys will be used for effective decision making in protecting the reefs of the Maldives.

 

 

 

Growth strategy for competitive success

 

Coral reefs that are vital to the Maldives as a source of economic growth and coastal protection are experiencing stress at both global and local levels. The hard corals that build reefs cope with stress and disturbance in different ways.  Therefore it is extremely important to understand how various types of stress can affect the distribution of important coral reef building species, in order to make effective decisions about managing the marine environment.

 

Corals differ in size and shape, which means they also provide different functional roles to the fish life and other marine life that live on the reef.  A coral starts out as a single polyp, overcoming the odds to settle on the reef and form a new colony. The way the specific coral grows and forms clones of itself will determine its success for survival, and is known in scientific terms as the corals “life history strategy”.

 

 Some corals, such as most branching Acropora species, prefer a quick growth strategy to outcompete any other coral and/or macro algae for valuable real estate on the reef.  Other corals, such as massive Porites species prefer a slow growth strategy but are more tolerant to stress events, such as storms and rising sea temperature. If we think of corals as the infrastructure in a big metropolitan city, we know building quickly and cheaply they will not last as long as a building with a solid foundation that has been expensive and time consuming to build.  For example if a cyclone comes through a city, buildings without a solid foundation will be destroyed, however they can be rebuilt quickly. This is the same for Acropora species that are often found in reef flats exposed to high wind. They can be impacted by high wind and heating events but have the ability to grow quickly and outcompete slower growing corals for space. The slow growth strategy of many massive bouldering corals such as Porites, leads to a very dense calcium carbonate structure, leaving them with the ability to withstand higher wave action and defensive capability to fend off other corals or marine organisms.

 

 

Human influence on coral reefs

 

Human developments can lead to increased stress on the marine environment, such as increased sedimentation or nutrient load in the water column. This can affect the quicker growing corals growth rate, as they spend more time defending themselves, therefore favoring the slow growing species.  This has become evident in the Caribbean reefs where there is a higher amount of massive/bouldering Montastrea coral species.  During the Maldives expedition we are surveying regions with varying degrees of human influence, 3-4 with low population influence, and 3-4 with high population influence. It will be interesting to see the comparisons between the coral reef communities.

 

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