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Coral Growth

Corals are slow-growing. Depending on the variety, they can grow less than 2mm a year up to a maximum of 10cm per year.


How Does our Coral Grow?

Corals are slow-growing. Depending on the variety, they can grow less than 2mm a year up to a maximum of 10cm per year. Even the fastest growing coral species grow at a frustratingly slow pace. The effects of coral bleaching and physical damage to colonies can destroy more surface area than the colony is able to replenish.

When not subject to these detrimental effects and left in peace, corals can grow from a collection of tiny individual anemone-like animals (polyps) into enormous, vibrant, massive structures given enough time and the right conditions. When new corals settle they are less than 1mm in diameter and are invisible – the process is called “coral recruitment”.

Coral recruitment is important to monitor as it can help determine the potential for future growth and recovery following disturbance – a reef with a high and successful recruitment rate is likely to be more resilient to external influences like increasing water temperatures and ocean acidification due to climate change. We have noted a lack of recruitment in some degraded areas of Pemban coral reefs and we are not sure why this is; could it be human activities? Predation by coral munching organisms? Physical factors preventing recruitment and survivorship?

To try and answer these questions we set up some experiments in the Kwanini Marine Protected Area (KMPA) where we have been measuring, photographing and recording the location of the coral recruits on four permanent concrete blocks on the seabed since August 2017. We have carried out three surveys of these blocks to-date; August 2017, March 2018 and August 2018 and we have gathered data regarding the number of recruits, how quickly each one grows, as well as losses between each survey period.

The data collected so far suggests that the concrete blocks are a suitable medium for initial coral settlement however the coral recruits are not developing into mature colonies. This could be due to the orientation of the concrete (the blocks are vertical in the water column) or the prevailing current. As part of our research we want to monitor different mediums, orientation in the water column and locations for coral recruitment to determine which is the most suitable, with a view to aiding reef restoration within the KMPA and beyond.

Here’s how you can support:

Help to sponsor an artificial reef structure in our ‘ocean laboratory’ to give us a better understanding of coral recruitment and growth

Support our research team to monitor the progress

Donate to our general research programme

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