Silly season is almost upon us! And by that, of course we mean coral spawning season. This weekend, corals throughout the Great Barrier Reef will spawn, releasing their reproductive bundles into the water column in a synchronised event. For our Reef Team this is a very busy time of year!
As a partner of the Boats4Corals project, alongside the Australian Institute of Marine Science (AIMS), a range of local tourism operators, and Traditional Owners, we collect coral spawn and release the larvae into other reef areas which may not get as much natural larval inflow, and are therefore slower to recover from impacts.
The preparation for this year’s spawning has already begun. Last week, the Boats4Corals team inspected 12 sites around the Whitsundays for their readiness to spawn, referred to as gravid coral checks.
During gravid coral checks, we assess several factors to determine whether a site is suitable for coral spawn slick collections. Key considerations include the extent and diversity of hard coral coverage, the presence and development stage of coral eggs, and whether the area is protected or has any environmental or physical barriers that might inhibit slick formation. These elements help us evaluate the site’s potential for successful collection and monitoring.
To answer these last two questions, the team take small samples of coral and look at the skeleton*. Egg bundles are visible as tiny spheres, often in groups, and the developmental stage of the eggs can be inferred by their colour. Generally, eggs start out as white and become pink as they mature.
The team sampled 370 hard coral colonies over two days, approximately two thirds of which had eggs. We have used the data to narrow down our target sites for spawn collection in a fortnight, having identified a subset of sites which are expected to be productive.
Ultimately the amount of spawn we are able to collect is very strongly influenced by the weather on the night. However, the extensive presence of developed eggs throughout the Whitsunday islands is a promising sign for this year’s fieldwork!
Cream (left) and white (right) eggs within Acropora corals. Photos supplied by Lisa McMullen – Daydream Island Living Reef.
Boats4Corals is part of the Whitsunday Reef Islands Initiative. The Reef Islands Initiative is a Great Barrier Reef Foundation program, supported by funding from Lendlease, the Australian Government’s Reef Trust, the Queensland Government and the Fitzgerald Family Foundation.
Thank you to the whole team: AIMS, ZigZag Whitsundays, Red Cat Adventures, Iconic Whitsunday Adventures and Ocean Rafting.
*Please note it is illegal to sample corals without a permit.