Chagos 3.0 - Day 6: Corals Spawn and Constellations

Doing fieldwork in remote areas has its challenges but also its many rewards, and one of these is being in the right place at the right time for some of nature’s most amazing shows.

Coral spawn floats to the surface

We’re anchored on the northern bank of the Great Chagos Bank, catching and tagging sharks as part of an ongoing collaboration between Stanford University, the University of Western Australia and the Bertarelli Foundation. The tagging going on into the night as sharks are active after dark when planktonic food rises to the surface and a multitude of fishes feed. While tending the line we have had a real treat today as endless drifts of coral spawn, released to coincide with the total darkness of a new moon, swirl past the boat. Corals synchronise their spawning to overcome the armies of predators for which these events are a feeding bonanza, so the water is filled with millions of floating eggs that mirror the Milky Way in the sky above as they pass the underwater lights. It’s a rare treat to be in just the right place to see this happen, particularly in the midst of flat calm seas and clear skies, and for most of us it is the first time we have witnessed this spectacle. We scoop a sample of the planktonic soup into a container for inspection under a magnifying lense, which reveals a mass of spherical eggs, together with myriad small crustaceans and other free floating ocean dwellers.

Peering at the plankton

Every day in the field has these moments, whether it is rescuing a Wilson’s Storm Petrel that has become stranded on deck, or seeing one of the sky filling sunsets that have been a regular feature of this trip, and it helps remind us of the unique opportunity we have in being able to study places like Chagos.

Aaron rescues a Wilson's storm petrel