Sage Fitzgerald’s Adventures in Coral

Sage Fitzgerald is a Ph.D. student with the Climate Change Cluster at The University of Technology Sydney and a Research Assistant at the Museum of Tropical Queensland and ARC Centre of Excellence for Coral Reef Studies. I recently heard her research on coral on a podcast that I have included below.

Sage is a Marine Biology graduate exploring coral taxonomy. Corals, more than any other group of marine invertebrates with the possible exception of molluscs, were the most sought-after undersea collectables of early expeditions of discovery to the tropical world.

Coral taxonomists of the remote past were not divers and therefore had no idea how species actually appeared in Nature, including variation in their shape, color, and abundance. If a specimen looked different enough it was proclaimed a new species and given a name;

there was no concept of what species actually were. At this time also, corals were swapped or borrowed among naturalists or museums for the price of a postage stamp, perhaps to be returned later, perhaps not.

Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria which typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.

A coral “group” is a colony of very many genetically identical polyps. Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in height. A set of tentacles surround a central mouth opening.

Each polyp excretes an exoskeleton near the base. Over many generations, the colony thus creates a skeleton characteristic of the species which can measure up to several meters in size. Individual colonies grow by asexual reproduction of polyps.

Corals also breed sexually by spawning: polyps of the same species release gametes simultaneously overnight, often around a full moon. Fertilized eggs form planulae, a mobile early form of the coral polyp which when mature settles to form a new colony.

Coral reefs are under stress around the world. In particular, coral mining, agricultural and urban runoff, pollution (organic and inorganic), overfishing, blast fishing, disease, and the digging of canals and access into islands and bays are localized threats to coral ecosystems. Broader threats are sea temperature rise, sea-level rise, and pH changes from ocean acidification, all associated with greenhouse gas emissions. In 1998, 16% of the world’s reefs died as a result of increased water temperature.

Approximately 10% of the world’s coral reefs are dead. About 60% of the world’s reefs are at risk due to human-related activities. The threat to reef health is particularly strong in Southeast Asia, where 80% of reefs are endangered. Over 50% of the world’s coral reefs may be destroyed by 2030; as a result, most nations protect them through environmental laws.