Mapping is often a necessary first step in the restoration process. Mapping helps define the extent and health of seagrass in both donor and recipient sites, and can be achieved through methods such as diving examinations, ROV assessment, and SONAR mapping.
One could also utilize remote sensing technology to compile trend and status maps for the study area prior to implementing the rest of the restoration process. Remote sensing techniques include aerial imagery gathered from vehicles to identify and assess the structure of the seagrass meadow.
Click here to see Adam Obaza, from Paua Marine Research Group, explain the mapping of eelgrass beds using divers in Southern California.
The success of restoration projects can often be estimated by means of computer modelling. Using knowledge of species survivability and geographic variations, scientists can make reasonable predictions as to what locations are most suitable for both collecting from and planting on.
The relationship between water quality stressors and seagrass response is imperative for a successful restoration. Monitoring is typically conducted using intensive sampling at a small number of stations.This process is designed to address the link between environmental change and seagrass condition. These studies can link the factors responsible for changes in seagrass structure and function to changes in water quality. Monitoring occurs at least annually in mid-summer, but may also be conducted quarterly.
To assess water quality, underwater sensors at permanent stations need to frequently measure light attenuation, surface irradiance, and water transparency depth.
Click here to hear Tanner Waters talk about how he collects field samples for his PHD project at UCLA, including water quality parameters and analyzing samples in the lab.
Examining the history of a restoration site is useful for determining possible causes for the degradation of marine vegetation habitats.
Looking at the project history of a site is useful because aspects such as location, restoration methodology, and environmental fluctuations, can result in variation in the success rate of the restoration project. Factors to examine include the historical extent and health of the degraded vegetation sites, previous instances of pollution, and causal factors for the deterioration of the sites.
Site selection is dependent on the priorities of the specific restoration project. There are multiple things to consider. A historical examination can help determine the success of a site by reviewing the extent and persistence of the vegetation. It also must be decided whether to address causal factors of reduced health (sedimentation, pollution), or to choose locations that are more forgiving to growing vegetation given current conditions.
Cultural factors tend to drive the intent of restoration projects. For some, restoration can be for restoration’s sake, but given the role of kelp and seagrass as ecosystem builders, restoring sites can help increase the productivity of important fisheries in the area. Choosing sites that maximize recolonization of fishery species can help this goal.
Pollution from human activity can create hostile environments for seagrass and kelp growth. Nutrient loading can spark eutrophication, an overgrowth of algae that blocks out needed light from reaching vegetation on the seafloor. Industrial wastewater can also lower the water quality enough to degrade the aquatic ecosystems. The elimination or reduction of this pollution can allow the area to be recolonized.
Click here to hear Dr. Cassie Gurbisz, from St. Mary's College of Maryland, discuss eutrophication and nutrient-loading as the main issues affecting submerged vegetation around the globe.
A public outreach program and partnership with local government and industry representatives allowed for the improvement of water quality. Manual replanting attempts were unsuccessful, and seagrass was naturally reestablished.
The implementation of secondary sewage treatment allowed for the improvement of water quality.
Ecosystem destruction is occasionally brought upon by the replacement of more aggressive, non-native species. These species are able to outcompete existing plant life. Eradication of invasives frees up the area for recolonization.
Caulerpa taxifolia, an aggressive invasive seaweed, was subjected to field and lab tests which determined chlorine bleach application was the most effective technique to kill individuals. Mechanical disturbance was minimized, as fragments from parent plants were able to survive and implant elsewhere. The plots of C. taxifolia were treated on-site by covering the plants with a tarp and injecting chlorine bleach underneath or introducing in a pelleted form. Besides lethality, the bleach had the additional benefit of inducing a color change which confirmed individual death.
Eradication efforts were successful because the restoration team assumed a rapid response and performed under the assumption that complete eradication was possible. With a sustained, persistent response; intensive, repeated surveys; and quantitative evaluations, complete eradication was achieved.
Disturbances in the food web can lead to an overgrowth of seagrass predators due to a lack of competition. A consequence of this imbalance is the overgrazing of marine vegetation, reducing its extent.
Historic overfishing in the region resulted in a population loss of sea urchin predators and competitors. The sea urchins then exploded in numbers and consumed much of the kelp. Restoration is in progress by means of dive teams manually culling the urchins by crushing or by chemical destruction with quicklime. Kelp naturally regrows in areas where sea urchin numbers have been reduced.
A technique that is not always necessary is the utilization of test plots. These allow restoration techniques to be evaluated for success on a small scale before translating the technique to the entire restoration site. While this allows maximum efficacy to be evaluated, it does tend to require a trial period, delaying the restoration of the site.
When manually re-establishing seagrass beds, seagrass “donor sites” are utilized. Seed collection from several donor sites can provide genetic diversity for the budding colony. The reproductive shoots, which contain the seeds, are removed from the donor site and are usually transported to an aquaculture facility, where the seeds mature before being planted at the recipient sites.
Click here to watch Brooke Landry, from the Maryland Department of Natural Resources, discuss different approaches to seed collection and distribution in small-scale & large-scale Submerged Aquatic Vegetation (SAV) restoration projects.
Click here to watch Kelly Darnell, from the University of Southern Mississippi, discuss how the reproductive ecology of eelgrass impacts seed collection and distribution.
Reproductive shoots were initially harvested by a team of divers. This proved slow and cost-ineffective. A water chestnut harvesting boat was repurposed for cutting and collecting reproductive shoots, which stood taller than the general vegetation and could therefore be harvested without damaging the ecosystem. Seeds were broadcasted by placing the shoots in mesh bags above the sediment, allowing the seeds to drop out when mature. Manual broadcasting was also used to evenly allocate the seeds.
Flowering shoots of eelgrass are placed into mesh bags and attached to buoys over restoration sites. Seeds drop out as they ripen.
Adult plants can be taken in their entirety from donor sites and replanted. This is often done manually, and there exists a variety of techniques for both collection and replanting. Methods for anchoring to the sea floor can include simply burying the shoots, staking the shoots into the ground, burying sod from donor sites, or covering the shoots with a protective mesh.
Click here to watch Adam Obaza, from Paua Marine Research Group, elaborate on his work collecting and transplanting eelgrass for restoration in Southern California.
Click here to watch Amanda Bird discuss her previous experience as the Marine Restoration Coordinator for OC Coastkeeper and how she involved the local community with eelgrass transplants.
Plugs of shoots were collected and planted with a time-release fertilizer, covered in a mesh screen, and monitored and scored for health.
Eelgrass shoots were fastened to bamboo stakes, which were then evenly distributed and anchored into the soil.
Sods from seagrass beds measuring approximately 2 x 1 m were removed from donor sites and buried in restoration sites.
Divers buried single, unanchored shoots with rhizomes by hand. Shoots were placed between 25 and 50mm deep.
PVC frames were constructed and landscape mesh suspended across it. The shoots were then tied to the mesh and the apparatus placed on the seafloor. Once the shoots were established in the sediment, the PVC frames were collected and reused.
Shoots were gathered by hand from eroded edges and low density areas from donor sites. At a lab or nursery, shoots were woven into pre-perforated burlap sacks, transported to the planting site, and anchored with sandbags. Scuba divers pushed shoots into the sediment in places deep enough as to not be significantly disturbed by wave action.