Restoration of tropical seagrass beds using wild bird fertilization and sediment regrading

• Published in: Ecological engineering 2018-03, Vol.112, p.72-81
• Main Authors: Kenworthy, W. Judson, Hall, Margaret O., Hammerstrom, Kamille K., Merello, Manuel, Schwartzschild, Arthur
• Format: Article
• Language: English
• Subjects: Anchors; Biodegradability; Biodegradation; Biological fertilization; Biomass; Calcium; Calcium carbonate; Calcium carbonates; Carbonates; Coverage; Disturbances; Ecological succession; Ecosystems; Environmental conditions; Fertilization; Groundings; Halodule wrightii; Injury prevention; Methods; Plants (botany); Recovery; Rehabilitation; Restoration; Scars; Sea grasses; Seagrass disturbance; Seagrasses; Sediment; Sediments; Shallow water; Statistical analysis; Storms; Substrates; Succession; Thalassia testudinum; Transplants; Tropical climate; Tubes; Vessel injury
• ISSN: 0925-8574; 1872-6992
• DOI: 10.1016/j.ecoleng.2017.12.008

[Display omitted] •Sub-tropical and tropical climax seagrass species such as Thalassia testudinum recover slowly from physical sediment disturbance, and in some environmental conditions may not recover at all without restoration efforts.•The modified “compressed succession” restoration technique (i.e. planting a fast growing seagrass species such as Halodule wrightii) temporarily substitutes for the climax species and facilitates restoration of seagrass ecosystem services.•Experimental results using a novel method of wild bird fertilization and sediment re-grading demonstrate the practical application for accelerating the recovery and restoration of slower growing seagrasses in severely disturbed, phosphorous limited sediment environments. Shallow water seagrass meadows are frequently damaged by recreational and commercial vessels. Severe injury occurs where propeller scarring, hull groundings and mooring anchors uproot entire plants, excavate sediments, and modify the biophysical properties of the substrate. In climax tropical seagrass communities dominated by Thalassia testudinum (turtlegrass), natural recovery in these disturbances can take several years to decades, and in some environmental conditions may not occur at all. During the recovery period, important ecological services provided by seagrasses are absent or substantially diminished and injured meadows can degrade further in response to natural disturbances, e.g. strong currents and severe storms. To determine if we could accelerate rehabilitation and prevent further degradation of injured turtlegrass meadows, we evaluated a restoration method called “modified compressed succession” using the fast-growing, opportunistic species Halodule wrightii to temporarily substitute ecological services for the slower-growing, climax species T. testudinum. In three experiments we showed statistically significant increases in density and coverage rates of H. wrightii transplants fertilized by wild bird feces as compared to unfertilized treatments. In one experiment, we further demonstrated that regrading excavated injuries with sediment-filled biodegradable tubes in combination with wild bird fertilization and H. wrightii transplants also accelerated seagrass recovery. Specific recommendations are presented for the best practical application of this restoration method in the calcium carbonate-based sediments of south Florida and the wider Caribbean region.