Coral mass spawning is one of the most spectacular natural phenomena. On nights following full moons in late spring and early summer on the Great Barrier Reef (GBR) dozens of coral species spawn within a few hours of each other filling the water with egg-sperm bundles that look a little like an underwater snow storm. I first witnessed coral spawning as an undergraduate student on Orpheus Island in 1993 while volunteering for project looking at the potential for hybridization in reef corals.

The dogma back in the day was that coral mass spawning only occurred on the Great Barrier Reef. Consequently, I was surprised while on a field trip to the Solomon Islands in 1999, this time as a research assistant on a project looking at changes in coral assemblage structure across the Pacific, to find that most of the staghorn corals had mature gametes and were therefore likely to spawn in synchrony following the next full moon. This was later confirmed by a BBC crew who filmed a number of species spawning within hours of each other. We later wrote up these observations resulting in one of my first publications (Baird et al. 2001). While it only takes one contrary observation to falsify a hypothesis, my mission to gather more data to better understand the phenomenon of coral mass spawning had begun. The next important port of call on this mission was Singapore, on route to a conference in Cambridge from Okinawa, where I had recently started a post-doc on the energetics of coral larval dispersal. In Singapore, I met James Guest and together we stumbled upon another example of mass-spawning outside of the GBR  (Guest et al. 2002). My collaboration with James has been one of the most enjoyable and productive of my career. Between us we have now visited hundreds of reefs and meet dozens of colleagues from over 20 countries throughout the Indo-Pacific. Our latest output is “An Indo-Pacific coral spawning database” (Baird et al. 2021). The database includes 6178 spawning observations for over 300 scleractinian species from 101 sites in the Indo-Pacific.

The goal of the database is to provide open access to coral spawning data to accelerate our understanding of coral reproductive biology. The hypothesis that coral mass spawning only occurred on the Great Barrier Reef proved incorrect (Guest et al. 2005), and there are many other ideas, based largely on anecdotal evidence, that remain to be tested. However, confronting these ideas with data was difficult because a lot of spawning observation remain unpublished (just under half of the observations in the Indo-Pacific coral spawning database were unpublished). Spawning is often incidental to the main topic of research, such as larval ecology, and consequently, much important information, such as the exact time of spawning, is often not included. Spawning observation are also by definition descriptive and many journals are reluctant to publish descriptive data. The coral spawning database allows for much of the important information on scleractinian coral spawning to be recorded in the one place. The coral spawning database is a living database, people can contribute at any time, and the database will be updated annually at figshare. We hope the Indo-pacific coral spawning database will advance knowledge on this fascinating and poorly understood topic.

Cited references

Baird AH, Sadler C, Pitt M (2001) Synchronous spawning of Acropora in the Solomon Islands. Coral Reefs 19:286-286

Baird AH, Guest JR, Edwards AJ, et al. (2021) An Indo-Pacific coral spawning database. Scientific Data 8:35

Guest JR, Chou LM, Baird AH, et al. (2002) Multispecific, synchronous coral spawning in Singapore. Coral Reefs 21:422-423

Guest JR, Baird AH, Goh BPL, et al. (2005) Seasonal reproduction in equatorial reef corals. Invertebr Reprod Dev 48:207-218