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Lefebvre, Lynn W.; Reid, James P.; Kenworthy, W. Judson; Powell, James Arthur, Jr.
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2000 |
Characterizing manatee habitat use and seagrass grazing in Florida and Puerto Rico: implications for conservation and management.
Pacif. Conserv. Biol. 5: 289-298. 1 tab. 2 figs.
–Compares manatee use of seagrasses in the Indian River Lagoon and eastern Puerto Rico, and with reports of seagrass use by dugongs. Manatees grazed more frequently on the locally most abundant species, exhibited possible cultivation grazing, and appeared to prefer Thalassia associated with clumps of Halimeda opuntia, which they pushed aside to get at the Thalassia. Florida manatees are hypothesized to be less specialized seagrass grazers than manatees in tropical regions.
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Di Carlo, Giuseppe; Kenworthy, W. Judson
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2008 |
Evaluation of aboveground and belowground biomass recovery in physically disturbed seagrass beds.
Oecologia 158(2): 285-298. 6 tabs. 5 figs. + online supplementary material.
–Describes, in addition to recovery from anthropogenic damage to seagrass beds in Florida and Puerto Rico, recovery from grazing by Antillean manatees in a Puerto Rican Thalassia bed.
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Waycott, Michelle; Duarte, Carlos M.; Carruthers, Tim J. B.; Orth, Robert J.; Dennison, William C.; Olyarnik, Suzanne; Calladine, Ainsley; Fourqurean, James W.; Heck, Kenneth L., Jr.; Hughes, A. Randall; Kendrick, Gary A.; Kenworthy, W. Judson; Short, Frederick T.; Williams, Susan L.
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2009 |
Accelerating loss of seagrasses across the globe threatens coastal ecosystems.
Proceedings of the National Academy of Sciences 106(30): 12377-12381. 1 tab. 2 figs. DOI: 10.1073/pnas.0905620106. July 28, 2009.
–ABSTRACT: Coastal ecosystems and the services they provide are adversely affected by a wide variety of human activities. In particular, seagrass meadows are negatively affected by impacts accruing from the billion or more people who live within 50 km of them. Seagrass meadows provide important ecosystem services, including an estimated $1.9 trillion per year in the form of nutrient cycling; an order of magnitude enhancement of coral reef fish productivity; a habitat for thousands of fish, bird, and invertebrate species; and a major food source for endangered dugong, manatee, and green turtle. Although individual impacts from coastal development, degraded water quality, and climate change have been documented, there has been no quantitative global assessment of seagrass loss until now. Our comprehensive global assessment of 215 studies found that seagrasses have been disappearing at a rate of 110 km2 yr?1 since 1980 and that 29% of the known areal extent has disappeared since seagrass areas were initially recorded in 1879. Furthermore, rates of decline have accelerated from a median of 0.9% yr?1 before 1940 to 7% yr?1 since 1990. Seagrass loss rates are comparable to those reported for mangroves, coral reefs, and tropical rainforests and place seagrass meadows among the most threatened ecosystems on earth.
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Lefebvre, Lynn W.; Provancha, Jane A.; Slone, Daniel H.; Kenworthy, W. Judson
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2017 |
Manatee grazing impacts on a mixed species seagrass bed.
Marine Ecology Progress Series 564: 29-45. 2 tabs. 9 figs. doi:10.3354/meps11986. Jan. 2016.
–ABSTRACT: The endangered manatee Trichechus manatus is one of few large grazers in seagrass systems. To assess the long-term impacts of repeated grazing on seagrasses, we selected a study site within Kennedy Space Center in the northern Banana River, Brevard County, Florida, that was typically grazed by large numbers of manatees in spring. Two 13 × 13 m manatee exclosures and 2 paired open plots of equal size were established at the study site in October 1990. Shoot counts, biomass, and species composition of the co-dominant seagrass species, Syringodium filiforme and Halodule wrightii, were sampled 3 times per year in all 4 plots between October 1990 and October 1994. We used a Bayesian modelling approach, accounting for the influence of depth, to detect treatment (exclosed vs. open) effects. S. filiforme shoot counts, total biomass, and frequency of occurrence significantly increased in the exclosures. By July 1993, mean biomass values in the exclosures (167 g dry wt m?²) greatly exceeded those in the open plots (28 g dry wt m?²). H. wrightii decreased in the exclosures by 1994. Initially, both S. filiforme and H. wrightii responded positively to release from manatee grazing pressure. As S. filiforme continued to become denser in the exclosures, it gradually replaced H. wrightii. Our findings may be helpful to biologists and managers interested in predicting seagrass recovery and manatee carrying capacity of repeatedly grazed seagrass beds in areas of special significance to manatees and seagrass conservation.
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Bibliography and Index of the Sirenia and Desmostylia 