Anitra Thorhaug

Large-scale seagrass restoration in a damaged estuary

Abstract After several years of environmental planning, and the Port of Miami Expansion Program having been started, a large-scale seagrass restoration project, including a test plot programme, was initiated in a damaged estuary in south-eastern Florida, Biscayne Bay, in 1982. For the project 13 test plots throughout the area were selected, totalling 10.38 acres in area, which is the largest test plot programme implemented to date, with the exception of our ongoing test plot programme in Jamaica (16.9 acres). Three seagrasses, Thalassia testudinum, Halodule wrightii and Syringodium filiforme, were transplanted at each test plot by two methods: 9.4–18.6 months after transplantation, survival and growth of the plants were measured (survival measurements taken by Connell Associates, Inc., 1983). Thalassia sprigs ranked first in survival followed by Halodule sprigs. Test plots differed widely in the survival and growth of the three species. Nine of the 13 plots had one species/method successful enough for further planting. Mid-bay sites damaged by dredging had two species surviving 60% or more. High turbidity sites were the least successful. Only Thalassia sprigs were successful at high energy sites. Syringodium sprigs showed poor survival overall, and are not recommended for transplanting. Thalassia seedlings appeared adequate in low energy sites, but required heavier anchoring in medium energy sites. The major impacts to the test plots were dredging, filling and urban run-off. No industrial effluent sites were included.

A Restored Seagrass (Thalassia) Bed and Its Animal Community

Quarterly sampling of animals in a restored seagrass ( Thalassia ) area in south Biscayne Bay, Florida, was undertaken to determine whether the recolonizing animal community would be similar in structure to a Thalassia community that had never been impacted by thermal effluents or restored. Samplings by 1 m bottom trawl (⅛ inch = 3.2 mm stretch-mesh), 3 replicates at each of 9 stations, and a 15-cm 2 grab (5 replicates at 9 stations) were sorted as to species for most groups and quantified. Strong seasonal differences were found. The results were compared with data from previous work in the area which had been done during thermal emissions from a power-plant. Significant differences were found between the abundance and species of animals in restored areas and a nearby barren area that had never recovered from impact, though differences in species and abundances between the restored Thalassia sites and an unaffected control site were not statistically different. Populations of certain groups such as the commercial Pink Shrimp ( Penaeus duorarum ), caridean shrimps, and juvenile fishes, were numerically far higher in the restored area than in control or naturally reestablishing successional seagrasses, and at least an order of magnitude higher than in barren areas that had never recovered from impact.

Effects of a variety of impacts on seagrass restoration in Jamaica

Abstract For the first time seagrass rehabilitation was attempted in a tropical nation, Jamaica. Repairs to a variety of developmental impact types were attempted with test plots: dredge and fill, bauxite and oil spills, channelization, urban run-off, urban sewage, river bulkheading, jetty construction and artificial beach, industrial lagoons, saline lagoons, thermal effluents, and cement tailings. Three species were routinely planted ( Thalassia testudinum, Halodule wrightii, Syringodium filiforme ) plus Ruppia maritima in saline lagoons, each by two planting techniques. Types of damage which were successfully attempted to be restored for the first time were from heated wastes, bauxite spills, jettied river mouths, small scale oil spills, and diluted urban wastes. Types of pollution damage previously repaired in subtropics and temperate zones, which could be successfully repaired in the tropics also were dredge and fill and urban run-off. Erosion seagrass restoration repair was partially successful at some sites. Attempts to repair high salinity lagoons (up to 160‰) and cement tailings were unsuccessful. Functional species were found which could tolerate ongoing pollutant loads in some cases.

Oil spill clean-up: The effect of three dispersants on three subtropical/tropical seagrasses

Abstract Three seagrasses found throughout the Greater Caribbean tropical/subtropical region as major critical habitat organisms were tested in the laboratory for toxicity limits to three dispersants commonly stockpiled in the region. At concentrations in the recommended dosage level, that is, below 1 ml dispersant with 10 ml oil in 100 000 ml seawater, even for 100 h no large mortality occurred (15–18 barrels per acre as calculated by Exxon, 1985). At an order of magnitude higher, especially for longer time periods, the more sensitive seagrasses Syringodium filiforme and then Halodule wrightii succumbed. The dispersants had widely differing effects, with Corexit 9527 and Arcochem D609 having far less toxic effect than Conco K(K) at the same exposure time and concentration. There was comparatively little difference between effects of oils (Louisiana crude versus Murban). Types and brands of dispersants should be referred to specifically in oil spill contingency plans since such widely varying ecological toxicity occurs among various dispersants. Use of the word ‘dispersant’ as a policy tool should be used with caution, realizing that dispersants vary widely in toxicity effects. Further testing of seagrasses in other ocean basins and those dispersants to be used there is highly recommended.

Dispersant use for Tropical Nearshore Waters: Jamaica

ABSTRACT Jamaicas shoreline is at the intersection of five major petroleum tanker shipping routes, and is a cargo transshipment point for the Caribbean. The natural coastline resources are valuabl...

Habitat restoration after pipeline construction in a tropical estuary: seagrasses

Abstract In 1981 the Florida Keys Aquaduct Authority permitted the construction of a new water transmission pipeline through the Florida Keys, USA. The seagrasses Halodule wrightii and Thalassia testudinum in an estuary and wetland area north of Key Largo would be removed by a portion of the pipeline construction. Consequently, government construction permit conditions required restoration of these seagrasses. After construction, Halodule shoots were planted over the pipeline trench in an area 6.1 × 975 m on 0.9 m centres. Additional transplantation of Halodule and Thalassia was deemed necessary, especially in areas lateral to the pipeline trench, and was done later in 1981 by a second party. Results after ten months showed that 31.1 ± 0.9% ( X ± S.E. ) of the area in the pipeline trench was covered by Halodule shoots. 1261 Thalassia seedlings were observed in the entire affected pipeline area. This is the first report of pipeline damage restored with seagrasses.

DISPERSED OIL EFFECTS ON TROPICAL HABITATS: PRELIMINARY LABORATORY RESULTS OF DISPERSED OIL TESTING ON JAMAICA CORALS AND SEAGRASS

ABSTRACT The island of Jamaica experiences six small- to medium-sized oil spills per year. Major ports for petroleum entry are close to mangrove, seagrass and coral resources. Mangrove and coral habitats form important nurseries for fish and shrimp populations. The coral reefs and white sand beaches of the north and west coasts are the basis of the tourism industry, which generates

The flowering and fruiting of restored Thalassia beds: A preliminary note

406 million U.S. dollars per year, and accounts for 55 percent of the islands foreign exchange earnings. Thus, protecting these resources from the effects of spilled oil is of priority to the government. Mechanical means are clearly not the solution in a variety of spills. Also, no maps exist to guide the on-scene coordinator (OSC) in oil spill management. To initiate a study of dispersed oil and formulate a command map, habitat-dispersed oil toxicity testing on three species of seagrasses, three indicator species of coral, and three mangroves has been conducted in Jamaica. Ten dispersants and their dispersed oil toxicity in ...

Management and Rehabilitation of Coastal Resources in the Third World: Jamaican Model for Seagrass Restoration

Abstract The bed of the subtropical—tropical marine seagrass Thalassia testudinum Banks ex Konig in an estuarine area previously denuded by thermal effluents (diverted permanently offstream at the time of restoration) in Biscayne Bay, Florida, was restored in August 1973 by planting thousands of seeds. In January 1976, non-restored areas contained 0–10 blades of Thalassia or 0.6 g dry wt. m−2, while restored areas had 1010 blades, 53 g dry wt. m−2, and control areas had 1794 blades or 60.8 dry wt. m−2. Spring 1977 abundance values in restored Thalassia beds averaged 2030 blades m−2, almost equivalent to the 2295 of the control areas. Flowering occurred in the restored bed in April 1977 and subsequent fruiting in August 1977. This is the first report of time to sexual maturity for Thalassia testudinum as well as the first report of a restored Thalassia bed resseding the recipient area into which it has been transplanted.

Thermal Pollution Effects on an Estuary in a Developing Nation: Impact and Rehabilitation of Seagrass

Abstract The Global Conservation Strategy launched by the United Nations Environmental Program emphasized the importance of wise resource use and management of coastal resources. The Caribbean Action Plan signed in 1982 pointed out the importance of coastal resources to environmental health of the Caribbean. Some developing nations such as Jamaica already had realized the importance of their coastal resources. Jamaica has approximately 200 miles of coastline which is fringed by mangrove forests and beaches, has large seagrass meadows and offshore corals. In the process of development of urban centers, infrastructure, and industries, tens of thousands of acres of seagrasses have been decimated. An important step in making seagrass resources and their fisheries nursery function sustainable was to transfer the technology of seagrass rehabilitation to Jamaica. It had never before been attempted in the tropics or the Third World. A set of 20 test locations for seagrass rehabilitation was jointly decided upon, including various portions of the coastline, various major types of pollution impacts and different environments (open ocean, coastline and estuary). At each site, the major types of seagrasses found in the area were planted. The results of this project show that the technology of seagrass rehabilitation can be transferred to the tropics. Test plots grew well on a variety of impacts. In some cases, seagrass beds coalesced in four months.