|Scientific Name:||Halophila decipiens|
|Taxonomic Notes:||This species has often been confused with Halophila ovalis. Halophila decipiens is monoecious, has serrate leaf tips and hairs on both sides of its leaves.|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Short, F.T., Carruthers, T.J.R., Waycott, M., Kendrick, G.A., Fourqurean, J.W., Callabine, A., Kenworthy, W.J. & Dennison, W.C.|
|Reviewer(s):||Livingstone, S., Harwell, H. & Carpenter, K.E.|
Halophila decipiens occurs mostly in the tropics and is circumglobal, widespread and locally abundant. It is found in deeper waters. Halophila decipiens has no major threats partly because it is found in deeper waters. Coastal development can locally affect seagrass beds in more shallow areas, as can reduced water quality. The global population trend for this species is expected to be stable as it is increasing in some regions, although some localized declines have been observed due to sedimentation (limitation of light). Halophila decipiens is listed as Least Concern. However, because of its deep water habitat more research is needed.
Halophila decipiens occurs mostly in the tropics and is circumglobal.
In the Atlantic, this species occurs in the Gulf of Mexico, throughout the Caribbean Sea, Bermuda and eastern Brazil. It also occurs on the northwest coast of Africa and in the Canary Islands.
In the Pacific, H. decipiens is found from southern Japan and the coast of China throughout Southeast Asia and extending east across the Coral Sea to Fiji. It occurs from the Great Barrier Reef across northern Australia. It is also found in the Hawaiian Islands, Midway, and French Polynesia as well as in Mexico at the southern end of the Baja Peninsula (Santamaria-Gallegos et al. 2006).
In the Indian Ocean, H. decipiens is found from southwestern Australia through the Timor Sea, along the coast of Indonesia, Thailand and southern Myanmar (Novak et al. 2009). It is also present in India, on the southeast and mid-west coasts. It is present in the Chagos Archipelago, in the northern Red Sea, and in Yemen. Halophila decipiens also occurs also in the Seychelles and Kenya (McMahon and Waycott 2009) and Madagascar (F. Short pers. obs.).
Native:Australia; Barbados; Bonaire, Sint Eustatius and Saba (Saba, Sint Eustatius); Brazil; China; Colombia; Costa Rica; Cuba; Curaçao; Dominican Republic; Egypt; French Polynesia; Grenada; Guadeloupe; India; Indonesia; Jamaica; Japan; Malaysia; Mauritius; Mexico; Myanmar; New Caledonia; Panama; Papua New Guinea; Philippines; Puerto Rico; Saint Martin (French part); Saint Vincent and the Grenadines; Seychelles; Sint Maarten (Dutch part); Spain; Sri Lanka; Thailand; Trinidad and Tobago; United States; United States Minor Outlying Islands; Vanuatu; Venezuela, Bolivarian Republic of; Virgin Islands, U.S.
|FAO Marine Fishing Areas:||
Atlantic – southwest; Atlantic – western central; Indian Ocean – eastern; Indian Ocean – western; Pacific – eastern central; Pacific – northwest; Pacific – western central
|Range Map:||Click here to open the map viewer and explore range.|
Halophila decipiens is widespread and locally abundant. It can have dense cover but low biomass. This species is often not collected or recorded, as the leaves can be obscured by sediments, and it is found in deeper water. Its global population trend is thought to be stable as it is increasing in some regions, although some localized declines have been observed in other regions due to localized threats.
The Midway Atoll (Hawaiian Islands) population forms dense patches with an average of 24,000 blades per square meter (McDermid et al. 2002).
The Costa Baja population displayed a total biomass of 5.2 ± 1.6 g dry weight (dw)/m² with a leaf-pair density of 2964 ± 778 during the winter months, a total biomass of 8.5 ± 2.2 g dw/m² and a leaf-pair density of 4016 ± 599 during the summer months (Santamaria-Gallegos et al. 2006).
In the west Florida shelf, this species covers an estimated 20,000 km² with an average coverage of 20%. During June of 1999, percent coverage was estimated at 45% in 10 m of water, 4% in 15 m, and 18% in 20 m. During the month of October, 1999, percent coverage was estimated at 74% in 10 m of water, 39% in 15 m, and 10% in 20 m. Biomass ranged from 0.02 to 2.64 g dry weight/m² . This species tends to follow typical sub-tropical seasonal cycles with lower biomass during the fall and winter months (Hammerstrom et al. 2006).
During 1972 to 1973, this species was reported to have a mean dry biomass of 0.14 g/m² along the northwest Cuban shelf at depths of up to 24.3 m. It was reported to be the least abundant seagrass studied, and accounted for 0.1% of total angiosperm biomass in the 2,000 km² range along the Cuban northwestern shelf (Buesa 1975).
Iverson and Bittaker (1986) reported H. decipiens occurring in small monotypic stands and sometimes occurring among H. wrightii in the northern offshore areas along the Big Bend, Florida in water deeper than five m. Data collected in 2000 showed no occurrence of H. decipiens along the Big Bend, Florida (Hale et al. 2004).
Halophila decipiens is not abundant or common in Bermuda: out of 55 sites sampled 3.6% had this species present; of these, 50% of sites sampled had less than six shoots per m2 (Murdoch et al. 2007).
|Habitat and Ecology:||
Halophila decipiens is typically found on coarse sediments, sand, and muddy bottoms. It is a deep water species but is also found in shallow water under docks and in turbid areas. Halophila decipiens can grow in areas with high sedimentation. Halophila decipiens is monoecious, with male and female flowers occurring on the same spathe. Female flowers produce approximately 30 seeds.
In the Caribbean it can be found to a depth of around 30 m, but in the Indo-Pacific may be found to 58 m (Lee Long et al. 1996). This species tends to be in monospecific seagrass beds (but in the Indo-Pacific it is found with Halophila spinulosa, and in the Caribbean occasionally with H. baillonii). It can be seasonal and has a large seed bank (Zieman 1982, Hemminga and Duarte 2000, Green and Short 2003, Larkum et al. 2006). It is a rapid re-colonizer when beds are disturbed by grazing or trawls.
Halophila decipiens can propagate through budding, but primarily relies on a buried seed bank for population re-establishment in seasonally fluctuating or high disturbance environments (Hammerstrom et al. 2006). It is a highly fecund, annual and opportunistic species (Kenworthy 1993) that may be favoured by disturbance (McMillan 1988), but unable to compete once the other species are established (Preen et al. 1995).
In Thailand, this species was previously thought only to occur in waters 9-36 m in depth but has been found in the intertidal areas where it is exposed during low tide down to the depths of five m. In Malaysian Peninsula, depth limit ranged from 6-24 m in clear water of the east coast, while only about 1.5-3.1 m in the turbid water of the west coast. In the Philippines, it grows primarily at depths of 11-23 m. In Cuba, it was found at a depth of 24.3 m with a biomass of 0.14 g/m². In Veracruz, Mexico it was found in the deeper parts down to 10 m. In the Caribbean, it was found in deep water up to 30 m. In South America, this species is associated with deeper reefs, algal and marl beds, and deeper soft-bottomed vegetative areas.
The first specimen of H. decipiens found in southwestern Australian was collected from the Hardy Inlet near the mouth of Blackwood River in late December 1991 (Kuo and Kirkman 1995). Halophila decipiens is frequently mixed with H. ovalis at a depth of 35 m, as well as in rock pools at the mid-tide level. Dense meadows of this species may cover the entire, gently sloping edge of the river channel. The mature plant produces flowers which fruit in the autumn. Seagrass meadows of this species disappear from the sites during winter (Kuo and Kirkman 1995).
Halophila decipiens is found 3-15 m deep along the Midway Atoll and forms dense patches with an average of 24,000 blades per m2. At the O'ahu Island depth ranges from 1-2 m and along Hawai'i Island, this species is found at depths of 40 m and forms monospecific patches adjacent to, yet not interacting with, Halophila hawaiiana at Midway and O'ahu. Halophila decipiens is the only seagrass to form pure stands in deep waters at the island of Hawai'i (McDermid et al. 2002).
The Costa Baja population was found mainly in subtidal waters with high leaf-pair density and a low biomass with seasonal biomass levels. Highest biomass and plant development were observed during the summer months (Santamaria-Gallegos et al. 2006).
Halophila decipiens has few major threats partly because it is found in deeper waters. Coastal development can locally affect seagrass beds in more shallow areas, as can reduced water quality. Trawls can disturb beds in deeper areas, but these are usually recolonized rapidly.
This species has numerous natural grazers such as turtles, dugongs and fish, and if in high numbers these can reduce biomass considerably.
No specific conservation measures are in place for H. decipiens, party due to its habitat in deeper waters. It is found in some protected areas (e.g., Belize, GBR) but it is often outside Marine Protected Areas (MPAs) because of its depth range. Currently, a seagrass management plan is being developed in Bermuda (Sarkis pers. comm. 2007).
Research on the biology of this species is recommended because of its deep water habitat.
Buesa, R.J. 1975. Population biomass and metabolic rates of marine angiosperms on the Northwestern Cuban Shelf. Aquatic Botany 1: 11-23.
Cambridge, M.L. and McComb, A.J. 1984. The loss of seagrasses in Cockburn Sound, Western Australia. I. The time course and magnitude of seagrass decline in relation to industrial development. Aquatic Botany 20: 229-243.
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.
Hammerstrom, K.K., Kenworthy, W.J., Fonseca, M.S. and Whitfield, P.E. 2006. Seed bank, biomass, and productivity of Halophila decipiens, a deep water seagrass on the west Florida continental shelf. Aquatic Botany 84(2): 110-120.
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.
Kenworthy, W.J. 1993. Conservation and restoration of the seagrasses of the Gulf of Mexico through a better understanding of their minimum light requirements and factors controlling water transparency. In: H.A. Neckles (ed.), Seagrass Monitoring and research in the Gulf of Mexico – Draft report of a workshop held at Mote Marine Laboratory in Sarasota, Florida. Sarasota, FL.
Kenworthy, W.J. 2000. The role of sexual reproduction in maintaining populations of Halophila decipiens: implications for the biodiversity and conservation of tropical seagrass ecosystem. Pacific Conservation Biology 5: 260–268.
Kuo, J. and Kirkman, H. 1995. Short Communication: Halophila decipiens Ostenfeld in estuaries of southwestern Australia. Aquatic Botany 51: 335-340.
Larkum, A.W.D., Orth, R.J. and Duarte, C.M. (eds). 2006. Seagrasses: Biology, Ecology and Conservation. Springer, Dordrecht.
Lee Long, W.J., Coles, R.G. and McKenzie, L.J. 1996. Deepwater seagrass in Northeastern Australia - how deep, how meaningful? In: J. Kuo, R.C. Phillips, D.I. Walker and H. Kirkman (eds), Proceedings of an International Seagrass Biology Workshop. Rottenest Island, Western Australia.
McDermid, K.J., Gregoritza, M.C. and Freshwater, D.W. 2002. A new record of a second seagrass species from the Hawaiian archipelago: Halophila decipiens Ostenfeld. Aquatic Botany 74: 257-262.
McMahon, K.M. and Waycott, M. 2009. New record for Halophila decipiens Ostenfeld in Kenya based on morphological and molecular evidence. Aquatic Botany 91(4): 318-320.
McMillan, C. 1988. Seed germination and seedling development of Halophila decipiens Ostenfeld (Hydrocharitaceae) from Panama. Aquatic Botany 31: 169-176.
Murdoch, T.J.T., Glasspool, A.F., Outerbridge, M., Ward, J., Manuel, S., Gray, J., Nash, A., Coates, K.A., Pitt, J., Fourqurean, J.W., Barnes, P.A., Vierros., M., Holzer, K. and Smith, S.R. 2007. Large-scale decline of offshore seagrass meadows in Bermuda. Marine Ecology Progress Series: 123-130.
Novak, A.B., Hines, E., Kwan, D., Parr, L., Tun, M.T., Win, H. and Short, F.T. 2009. Revised ranges of seagrass species in the Myeik Archipelago, Myanmar. Aquatic Botany 91(3): 250-252.
Preen, A.R., Lee Long, W.J. and Coles, R.G. 1995. Flood and cyclone related loss, and partial recovery, of more than 1,000 km² of seagrass in Hervey Bay, Queensland, Australia. Aquatic Botany 52: 3-17.
Santamaría-Gallegos, N A., Riosmena-Rodríguez, R. and Sánchez-Lizaso, J.L. 2006. Occurrence and seasonality of Halophila decipiens Ostenfeld in the Gulf of California. Aquatic Botany 84(4): 363-366.
Schils, T. 2002. Macroalgal assemblages of the Socotra Archipelago. Conservation and sustainable use of biodiversity of Socotra Archipelago. Marine habitat, biodiversity and fisheries surveys and management. In: M. Apel, K.I. Hariri and F. Krupp (eds), Final report of phase III. Senckenberg Research Institute, Frankfurt a.M., Germany.
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., Waycott, M., Kendrick, G.A., Fourqurean, J.W., Callabine, A., Kenworthy, W.J. & Dennison, W.C. 2010. Halophila decipiens. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 22 November 2014.|
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