Corals in Our Nursery

Staghorn Corals

The staghorn coral (Acropora cervicornis) is a branching, stony coral with cylindrical branches ranging from a few centimetres to over two metres in length and height. It occurs in back reef and fore reef environments from 0 to 30 m (0 to 98 ft) depth. The upper limit is defined by wave forces, and the lower limit is controlled by suspended sediments and light availability. Fore reef zones at intermediate depths 5–25 m (16–82 ft) were formerly dominated by extensive single-species stands of staghorn coral until the mid-1980s. This coral exhibits the fastest growth of all known western Atlantic fringe corals, with branches increasing in length by 10–20 cm (3.9–7.9 in) per year. This has been one of the three most important Caribbean corals in terms of its contribution to reef growth and fishery habitat.

Elkhorn Corals

Elkhorn coral (Acropora palmata) is an important reef-building coral in the Caribbean. The species has a complex structure with many branches which resemble that of elk antlers; hence, the common name. The branching structure creates habitat and shelter for many other reef species. Elkhorn coral is known to grow quickly with an average growth rate of 5 to 10 cm (2.0 to 3.9 in) per year. They can reproduce both sexually and asexually, though asexual reproduction is much more common and occurs through a process called fragmentation.

Our Work

Although Elkhorn and Staghorn corals dominated the Caribbean in the early 1980s, their populations have since declined dramatically. Scientists estimate that between 1980 and 2006, when these corals were listed under the Endangered Species Act (ESA), their populations decreased by approximately 97%. This decline was caused by various factors, including disease, algae growth, climate change, ocean acidification, and human activity. In May 2006, Elkhorn coral was officially listed as threatened under the ESA, alongside Staghorn coral, another species in the Acropora genus. Conservation efforts are now underway to protect these species and promote greater genetic variability among their populations.

Shelter and Structure

Staghorn and Elkhorn corals have been dominant in reef growth throughout the Caribbean and Tropical Western Atlantic for the past 5,000 years. They provide shelter and structure for many species of reef inhabitants and are visually stunning representatives of coral reef systems. 

Like the foundation of a house, Elkhorn coral support coral reef communities. Their interwoven lattice-like branches create a variety of habitats varying in topography, which in turn, support diverse fish populations. These habitats support fish nurseries and protect fish from predators, increasing reef diversity but they also protect the coastline from storms and heavy waves.

Coral Expansion

At Reef Restoration Team Curaçao, our current method of expansion begins with Coral Tree Nurseries. These nurseries are ladders of PVC to form “coral-trees” that are attached to the bottom with blocks and buoyed with floats that sit just below the surface. This design allows the trees to move freely with the surf and surge of the water, preventing damage both to the tree structure and the corals. Each tree holds a unique genetic strain, or genotype, of coral, and a “full” tree can hold about 100 baby corals. All the trees are made of recycle materials to make it sustainable and eco.

One of the primary benefits of coral nurseries is the care that can be provided to growing corals. Maintenance of nursery sites are critical to maximizing coral health and minimizing incidence of disease, predation, and breakage.

The Coral Tree nursery has proved to be an efficient and effective way to grow and propagate future generations of corals through fragmentation. Fragmentation is a process that occurs naturally when corals reproduce asexually. When a large fish or wave breaks a branch off the coral, the branch will continue to grow into a new coral if the water conditions are favorable. We copy this process in our nurseries by using pliers to cut finger length pieces from existing, large corals. Those fragments are hung back on the same tree, or a new tree with the same marking, creating more corals of the same genotype. This way, the Coral Tree nurseries become a self-sustaining approach to grow corals.

Out Planting

Out planting, or planting coral fragments grown in nurseries back onto reefs, is a type of restoration activity. So after six months of growing in the nursery, our corals are healthy and mature enough to be out planted to a restoration site. Restoration sites are reef sites that are degraded and damaged and would benefit from healthy corals growing there.

Our current method is attaching corals to bamboo structures, placing these strategically in areas where conditions seem favorable. Our corals are tagged to keep track of the genetic information and to allow for short and long-term monitoring.

There are many criteria for selecting a restoration site. A few we take into consideration are existing and historical wild populations, depth, water quality, bottom type, size of the area, predator abundance, wave exposure, and the effects of human activities.

Maintenance and Monitoring

Both coral nurseries and restoration sites are monitored regularly. We check our nurseries for disease, predation, and damage to nursery structures, and more. This helps us to control and prevent issues before they occur. Our nurseries also receive biweekly cleaning in order to prevent the overgrowth of algae and fire coral. At restoration sites, we monitor survival rates, tissue paling, disease, predation and diver damage. Because of this monitoring our corals get a 2^nd chance at success as we ensure that the coral fragments are in the position to mature and prepare for out planting. Our out planted corals will continue to grow until the bamboo structures collapse. When this happens the corals fell into each other creating the strength of the coral reef. Broken fragments would be unable to survive on their own, and can be placed back at the coral tree for a 2^nd change, taking in consideration this would be the same genotype.