Last updated: May 15, 2017
Natural Healing - Using Sponges for Reef Restoration
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Transcript( music playing ) Hi, Welcome to Biscayne National Park! My name is Emily McGrath and I’m a Biological Science Technician in the Damage Recovery Program, in the Division of Resource Management. Vessel groundings in shallow coral reef and seagrass habitats happen frequently in the Park. Our Program works to assess and restore grounding injuries. This film is about an innovative approach that Park Staff are using to restore coral reef injuries using natural sponges that are naturally found on the reef. The abundance of vessel traffic, along with the many shallow habitats located within the boundaries of Biscayne National Park, result in a high risk for vessel groundings. When groundings occur, vast rubble “fields” can be generated upon impact of a vessel, depending on size and severity of the grounding. This rubble is dynamic and can shift and roll with water motion due to storms or hurricanes. If rubble remains mobile it will slow the recruitment of new corals to the site, and surviving coral may continue to be damaged, slowing natural recovery of the injury. Rubble stabilization is an important part of restoring vessel groundings, and can be managed in several ways. Rubble can be stabilized using cement, relocated to another site, removed for land-based disposal, or left along onsite. Another option is the use of natural materials for rubble stabilization. Biscayne National Park is interested in minimizing the introduction of non-native materials in its restoration practices where possible, and are using several species of branching sponges native to the area in a new restoration project. These sponges naturally bind rubble in reef environments. By naturally fragmenting and attaching to rocks and rubble, they act as initial stabilizing agents. The use of certain species of branching, erect sponges to stabilize rubble has been successful on an experimental scale in other parts of the Caribbean. While sponges hold rubble together, attaching as quickly as 5 days, they allow other carbonate secreting organisms to colonize the rubble, stabilizing it from the inside. Research has also suggested that sponges may form a “biofilm”, secreting chemical signals that may encourage coral larvae to settle. Stabilized rubble also increases complexity of the substrate, providing habitat for fish and invertebrates. (banging) We have recently applied these promising experimental results to a restoration-scale project in the Park. The grounding of an 84’ vessel in 2008 created several hundred square meters of rubble. We gathered rubble at the site into discrete mounds, and then used two sponge species, individually and in combination, as well as concrete, to stabilize the rubble mounds. Control mounds were also created that did not incorporate a stabilizing agent. If sponge-mediated rubble stabilization proves to be a successful method for reef restoration, it will be important to secure a source of sponge material that can be used for restoration without being detrimental to natural sponge populations. As a secondary portion of this restoration project, we assembled sponge “gardens” to evaluate the feasibility of propagating sponges for use in restoration, as well as to ensure that harvesting the sponges for restoration or for propagation is not harmful to the donor sponges. We cut fragments of each species of sponge used and attached them to PVC rods embedded into concrete paver stones using zipties. We also marked the donor sponges from which the fragments were cut, as well as untouched control sponges. In order to keep track of this effort, we will monitor the rubble mounds over the course of five years. Results will be analyzed to look for differences among the sponges and concrete, in terms of rubble stability and recruitment of corals, gorgonians, and other reef organisms. We are also monitoring the sponge gardens over time by measuring the survival and biomass of all three sponge treatments. By comparing these measurements, we can found out several things; if this type of sponge propagation, if fragment removal is harmful to the donor sponge, and if growth rates between harvested sponges and controls are comparable. So far, the sponges in the rubble mounds are surviving and are firmly attached to the rubble pieces they are tied to. However, because this is a recent project, it’s too soon to tell if the sponges are successfully holding the entire rubble mounds together, or if they are enhancing recruitment of reef organisms. Future monitor events will provide more information. In the sponge gardens, most sponge fragments formed some means of attachment after only one week, and after several months have firmly affixed to the PVC rods. The sponges have shown very low levels of death or disease, and all appear to be generally unaffected by the harvesting. These early results suggest that the propagation of sponges for restoration is a sustainable practice that can be used with little impact to donor sponge populations. This initial restoration scale project will give us a better idea if these methods are practical and sustainable for large scale use within the Park and in other reef areas affected by ship groundings. A reef that has experienced a grounding will never be the same. What you just saw was a description of the efforts being made at Biscayne National Park to minimize the damage caused by grounded vessels, restore the injury with fewer man-made materials, and allow the reefs a fighting chance to recover. I encourage you to visit Biscayne National Park and experience your America! My name is Emily McGrath and thank you for watching! ( music playing ) ( music ends )
Natural Healing - Using Sponges for Reef Restoration in Biscayne National Park. Hosted by Emily McGrath.