CORAL REEFS: AN INTRODUCTION.

Everybody knows what a coral reef is, right? Well just in case here is a recap.....

Coral reefs are the rainforests of the ocean. Coral Reefs are biologically and ecologically important ecosystems that have a very high biodiversity. They account for less than 1% of the earth’s surface but host 25% of all marine species (Mulhall 2007). Most coral reefs were formed after the last glacial period  when snow melted, sea levels rose and continental shelves were flooded.

A coral is marine organism from the class Anthozoa. Typically they live in compact colonies of many identical individual ‘polyps’. Each polyp secretes a calcium carbonate shell which acts as protection from the sea and its inhabitants. These shells form a raised mound called a reef. Corals have a mutual relationship with zooxanthellae (single celled algae) which provide energy from photosynthesis in return for nutrients, protection and being held closure to the ocean surface, and therefore the sun.   

Reefs are typically found in latitudes between 30˚N and 30˚S as they are limited in geographical distribution to the clear, warm and sunlit waters of the tropical ocean. Reef forming corals flourish only in water under 30 metres deep (the photic zone, where light penetrates the surface layer of water) and warmer than 22 ˚C. Consequently coral reef hot spots include the Indo-Pacific around Indonesia, the Philippians and Papua New Guinea. The Caribbean (Atlantic Ocean), although less of a hot spot, still contains a number of common species.

This specificity means corals are highly susceptible to current climate change through ocean acidification, rising sea levels and warmer ocean temperatures.

Over the next ten weeks I will explore the scientific literature, the news and follow fellow coral bloggers to try and piece together a comprehensive understanding of how corals have coped in the past, the present and what the future might hold for them.

Join me later in the week for a review of the corals’ evolutionary history.

Mulhall, M. 2007. Saving rainforests of the sea: An analysis of international efforts to conserve coral reefs. Duke Environmental Law and Policy Forum. 19: 321-351.