|Scientific Name:||Halophila engelmanni|
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Assessor(s):||Short, F.T., Carruthers, T.J.R., van Tussenbroek, B. & Zieman, J.|
|Reviewer(s):||Livingstone, S., Harwell, H. & Carpenter, K.E.|
Halophila engelmanni has a disjunct distribution in the western Atlantic and has wide fluctuations in presence and abundance. It is an uncommon species and its overall population is thought to be decreasing, although it is not known to what extent. Threats are sedimentation and turbidity and local coastal developments. The area of occupancy (AOO) of this species is thought to be near to 2,000 km², and this almost meets the threshold of Vulnerable under B2 overall continuing decline and (b) and fluctuations in population (c). Therefore this species is listed at Near Threatened. This species requires close population trend monitoring and wider observation.
|Range Description:||Halophila engelmanni has a somewhat disjunct distribution in the western Atlantic. It is found sporadically throughout the Gulf of Mexico, along the east coast of Florida and in western Cuba, Puerto Rico and Venezuela. The area of occupancy (AOO) of this species is thought to be near to 2,000 km².|
Native:Bahamas; Cuba; Mexico; Puerto Rico; United States; Venezuela, Bolivarian Republic of
|FAO Marine Fishing Areas:||
Atlantic – western central
|Estimated area of occupancy (AOO) - km2:||2000|
|Lower depth limit (metres):||18|
|Range Map:||Click here to open the map viewer and explore range.|
Halophila engelmanni has a disjunct distribution. It is very habitat-specific, thus it is not very abundant. It is found in disturbed areas but its persistence is unknown. The overall trend of the population is thought to be decreasing.
In the northern coast of Yucatan and in Florida there are wide fluctuations in presence and abundance (van Tussenbroek and Zieman pers. comm.).
Halophila engelmanni had an estimated mean dry density of 0.25 g/m² at depths of up to 14.4 m and accounted for 0.2% of total angiosperm biomass in the 2,000 km² range along the Cuban northwestern shelf between 1972 and 1973 (Buesa 1975).
Hale et al. (2004) reported a decline in occurrence of H. engelmanni along the Big Bend region of Florida (Anclote Key north to Apalachee Bay) when compared to data from 1974 -1980 reported in Iverson and Bittaker (1986). Data collected between 1974 and 1980 show a 12% occurrence for this species compared to the 8% occurrence recorded in 2000. Combining this research results in 30% total loss for this area. These losses occurred in the northern region of the study along the coastline and in the deepest portions of the southern region. This accounts for the loss of at least three m from the maximum depth of distribution (Hale et al. 2004).
This species also was observed in the Johnson Key Basin, Florida Bay, in 1996. Abundance in the western part of Florida Bay appears to have increased as abundance of Thalassia testudinum decreased due to low light levels caused by high turbidity (Durako and Hall 2000).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||
Halophila engelmanni generally occurs as an understory species, commonly associated with Syringodium and Halodule, and only occasionally with Thalassia. It is generally a shallow water species in turbid waters. A very small plant, H. engelmanni rarely exceeds 10 cm in height. Its habitat is generally in sandy and muddy substrates, but it can also be found in areas with gravel or rock bottom.
This species is known to have prolific flowering but nothing is known about seedbank recruitment. (Zieman 1982, Hemminga and Duarte 2000, Green and Short 2003, Larkum et al. 2006). Dispersal is low.
Its depth range in Florida is 1.4 to 18.3 m (Fourqurean et al. 2002). In Cuba, it is found at a depth of 14.4 m with biomass of 0.25 g/m² (Green and Short 2003).
|Generation Length (years):||1|
|Major Threat(s):||Halophila engelmanni has a limited distribution and is thought to be negatively impacted by sedimentation and turbidity. It is also locally threatened by anthropogenic activities such as coastal development, trawling, eutrophication and pollution and tourism.|
Halophila engelmanni is found in some Marine Protected Areas (MPAs).
Research is recommended for its distribution and biology, particularly it resilience capability with regard to seedbanks.
Buesa, R.J. 1975. Population biomass and metabolic rates of marine angiosperms on the Northwestern Cuban Shelf. Aquatic Botany 1: 11-23.
Durako, M.J. and Hall, M.O. 2000. After the die-off: Seagrass dynamics in a perturbed subtropical lagoon. Biologia Marina Mediterranea 7(2): 365-368.
Fourqurean, J.W., Durako, M.J., Hall, M.O. and Hefty, L.N. 2002. Seagrass distribution in south Florida: a multi-agency coordinated monitoring program. In: J.W. Porter and K.G. Porter (eds), The Everglades, Florida Bay, and the coral reefs of the Florida Keys, pp. 497-522. CRC Press, Boca Raton, Florda, USA.
Green, E.P. and Short, F.T. 2003. World Atlas of Seagrasses. University of California Press, Berkeley.
Hale, J.A., Frazer, T.K., Tomasko, D.A. and Hall, M.O. 2004. Changes in the distribution of seagrass species along Florida's central Gulf Coast: Iverson and Bittaker revisited. Estuaries 27(1): 36-43.
Hemminga, M.A. and Duarte, C.M. 2000. Seagrass Ecology. Cambridge University Press, Cambridge.
IUCN. 2010. IUCN Red List of Threatened Species (ver. 2010.3). Available at: http://www.iucnredlist.org. (Accessed: 2 September 2010).
Iverson, R.L. and Bittaker, H.F. 1986. Seagrass distribution and abundance in eastern Gulf of Mexico coastal waters. Estuarine, Coastal and Shelf Science 22: 577-602.
Larkum, A.W.D., Orth, R.J. and Duarte, C.M. (eds). 2006. Seagrasses: Biology, Ecology and Conservation. Springer, Dordrecht.
UNESCO. 1998. CARICOMP-Caribbean coral reef, seagrass and mangrove sites. Coastal region and small island papers. UNESCO, Paris.
Zieman, J.C. 1982. The ecology of the seagrasses of South Florida: a community profile. US Fish and Wildlife Service Biological Services Program FWS/OBS-82/5: 150.
|Citation:||Short, F.T., Carruthers, T.J.R., van Tussenbroek, B. & Zieman, J. 2010. Halophila engelmanni. The IUCN Red List of Threatened Species 2010: e.T173337A6994043. http://dx.doi.org/10.2305/IUCN.UK.2010-3.RLTS.T173337A6994043.en . Downloaded on 08 October 2015.|
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