ELKHORN CORAL (Acropora palmata) is a widespread reef coral, an unmistakeable species with large branches that resemble elk antlers. The dense growths create an ideal shady habitat for many reef creatures. These include reef fishes of all shapes and sizes, lobsters, shrimps and many more besides. Elkhorn and similar larger corals are essential for the wellbeing both of the reef itself and also its denizens. These creatures in turn benefit the corals and help keep them in a healthy state.
Examples of fish species vital for healthy corals include several types of PARROTFISH, the colourful and voracious herbivores that spend much of their time eating algae off the coral reefs using their beak-like teeth. This algal diet is digested, and the remains excreted as sand. Tread with care on your favourite beach; in part at least, it will consist of parrotfish poop.
Other vital reef species living in the shelter of elkhorn and other corals are the CLEANERS, little fish and shrimps that cater for the wellbeing and grooming of large and even predatory fishes. Gobies, wrasse, Pedersen shrimps and many others pick dead skin and parasites from the ‘client’ fish including their gills, and even from between the teeth of predators. This service is an excellent example of MUTUALISM, a symbiotic relationship in which both parties benefit: close grooming in return for rich pickings of food.
VULNERABILITY TO CLIMATE CRISIS
Formally abundant, over the course of just a couple of decades elkhorn coral (along with all reef life) has been massively affected by climate change. We can all pinpoint the species responsible for much of the habitat decline and destruction, and the primary factors involved. In addition, global changes in weather patterns result in major storms that are rapidly increasing in both frequency and intensity worldwide.
Physical damage to corals may seriously impact on reproductive success: elkhorn coral is no exception. The effects of a reduction of reef fertility are compounded by the fact that natural recovery is in any case inevitably a slow process. The worse the problem gets, the harder it becomes even to survive, let alone recover, let alone increase.
HOW DOES ELKHORN CORAL REPRODUCE?
There are two types of reproduction, which one might call asexual and sexual:
- Elkhorn coral reproduction occurs when a branch breaks off and attaches to the substrate, forming a the start of a new colony. This process is known as Fragmentation and accounts for roughly half of coral spread. Considerable success is being achieved now with many coral species by in effect farming fragments and cloning colonies (see Reef Rescue Network’s coral nurseries)
- Sexual reproduction occurs once a year in August or September, when coral colonies release millions of gametes by Broadcast Spawning
All photos: Melinda Rogers, with thanks as ever for use permission