The release of data records within confidential reports has given researchers rare access to information that is providing a new insight into the unique reproductive cycles for the remote coral reefs along Western Australia’s (WA’s) coastline.

While the rapid industrial expansion through regions of WA in the last decade has seen an increase in the number of studies of coral reproduction, access to data within confidential reports to industry and government has only now unlocked information relating to tens of thousands of corals and hundreds of species, from over a dozen reefs spanning 20 degrees of latitude.

Project leader Dr James Gilmour from the Australian Institute of Marine Science, along with CSIRO Marine and Atmospheric Researchers found that the results from the Western Australian Marine Science Institution (WAMSI) Dredging Science Node published this month in the journal Peer J carry important management implications.

“Environmental managers aim to minimise human impacts during significant periods of larval production and recruitment on reefs, but doing so requires knowledge of the modes and timing of coral reproduction,” Dr Gilmour said. “From these data we were able to identify broad latitudinal patterns, but many gaps in knowledge remain due to paucity of data, biased sampling, issues with methodology and the profound difficulty in distinguishing coral species.”

Because of WA’s phenomenal diversity of habitats and coral communities, and wide range in reef-level patterns of coral reproduction, the examination of patterns of reproduction has been divided among six regions:

1. Kimberley Oceanic;
2. Kimberley;
3. Pilbara;
4. Ningaloo;
5. Abrolhos and Shark Bay; and
6. Rottnest and southwest WA

Source: Gilmour J, Speed CW, Babcock R. (2016) Coral reproduction in Western Australia. PeerJ 4:e2010 doi.org/10.7717/peerj.2010

Among these regions, the diversity of coral was found to decrease with increasing latitude, with the Houtman Abrolhos Islands having the highest latitude coral reefs in Western Australia.

The study found that mass spawning during autumn occurred on all tropical and sub-tropical reefs. A smaller, multi-specific spawning during spring decreased from approximately one quarter of corals on the Kimberley Oceanic reefs to little participation at Ningaloo.

Within these seasons, spawning was concentrated in March and/or April, and October and/or November, depending on the timing of the full moon. The timing of the full moon was critical to determining the month of spawning within these seasons, and whether spawning was ‘split’ over two consecutive months.

Mixed coral assemblage of spawning and brooding corals (Image: James Gilmour)

Most studies were found to have focused on species of Acropora, which include some of the major corals responsible for building the complexity that supports reef diversity. However, other reefs are dominated by non-Acropora corals, for which far less is known about their reproduction.

Studies conducted by industry and consultants in the Dampier Archipelago highlight the different patterns of reproduction among reefs in WA, according to their contrasting species abundances. For example, functionally important species of massive Porites seemed to spawn through spring to autumn on Kimberley Oceanic reefs and during summer in the Pilbara region.

“Most studies of coral reproduction in WA have been conducted over a few months at several reefs, of which there are few published accounts, leaving large gaps in knowledge,” Dr Gilmour said. “The gaps are significant because the existing data illustrate just how unique the patterns of reproduction displayed by WA coral communities are and the extent to which they vary among habitats and regions.

“Even for reefs and species that are relatively well-studied, the patterns of reproduction are complex,” Dr Gilmour said. “Recent work suggests that within a single site on some northern reefs, colonies within the same species may consistently spawn during different seasons (Gilmour et al. 2016, Rosser 2015), leading to massive genetic differentiation and questions of whether, in a reproductive sense, they are considered the same species. Addressing these issues is again confounded by the morphological and reproductive plasticity for which corals are infamous.”

Related links

Gilmour J, Speed CW, Babcock R. (2016) Coral reproduction in Western Australia. PeerJ 4:e2010 doi.org/10.7717/peerj.2010

Gilmour JP, Underwood JN, Howells EJ, Gates E, Heyward AJ (2016) Biannual Spawning and Temporal Reproductive Isolation in Acropora Corals. PLoS ONE 11(3): e0150916. doi:10.1371/journal.pone.0150916

Rosser, N. L. (2015), Asynchronous spawning in sympatric populations of a hard coral reveals cryptic species and ancient genetic lineages. Mol Ecol, 24: 5006–5019. doi:10.1111/mec.13372

The WAMSI Dredging Science Node is made possible through $9.5 million invested by Woodside, Chevron and BHP as environmental offsets. A further $9.5 million has been co-invested by the WAMSI Joint Venture partners, adding significantly more value to this initial industry investment. The node is also supported through critical data provided by Chevron, Woodside and Rio Tinto Iron Ore.

 

Dredging Science