Johnson's seagrass: Difference between revisions
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|name = Johnson's seagrass |
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|image = Johnsons seagrass.jpg |
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|image_caption = Closeup of a bed of Johnson's seagrass |
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Both the [[Green sea turtle]] and the [[West Indian manatee]] are known to feed upon the plant, as well as some [[herbivorous]] fish. However, the main threat to species survival is probably human activity.<ref name=2002_recovery_plan/> Processes that threaten the plant include [[eutrophication]], [[dredging]], [[turbidity]], and [[thermal pollution]].<ref name=tnc>[http://www.natureserve.org/explorer/servlet/NatureServe?searchName=Halophila+johnsonii ''Halophila johnsonii''.] [[The Nature Conservancy]].</ref> |
Both the [[Green sea turtle]] and the [[West Indian manatee]] are known to feed upon the plant, as well as some [[herbivorous]] fish. However, the main threat to species survival is probably human activity.<ref name=2002_recovery_plan/> Processes that threaten the plant include [[eutrophication]], [[dredging]], [[turbidity]], and [[thermal pollution]].<ref name=tnc>[http://www.natureserve.org/explorer/servlet/NatureServe?searchName=Halophila+johnsonii ''Halophila johnsonii''.] [[The Nature Conservancy]].</ref> |
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==Removal U.S. Federal List of Threatened and Endangered Species== |
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In 2022 the National Marine Fisheries Service (NMFS) and National Oceanic and Atmospheric Administration (NOAA) ruled to remove ''Halophila johnsonii'' (Johnson's seagrass) from the Federal Endangered Species Act (ESA).<ref>{{cite web | url=https://www.federalregister.gov/documents/2022/04/14/2022-08029/endangered-and-threatened-wildlife-and-plants-removal-of-johnsons-seagrass-from-the-federal-list-of | title=Federal Register :: Request Access }}</ref> This ruling was based on recent genetic data obtained that show that Johnson's seagrass is not a genetically unique taxon. Johnson's seagrass is genetically similar to the Indo-Pacific species, ''H. ovalis'', based on findings from multiple publishing's. As Johnson's seagrass is not genetically diverse, it no longer meets the requirements set by the ESA to be considered a species. The ESA defines a species as "any subspecies of fish or wildlife or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature 16 U.S.C. 1532". All gene samples of Johnson's seagrass from Indian River Lagoon over a 17 year study were genetically uniform. In the same study it was determined that due to the lack of genetic diversity, Johnson's seagrass was a clone of ''H. ovalis'', closely related to populations in Africa and Antigua. The clone may be derived from a recent introduction from one of those regions.<ref>{{cite journal | doi=10.3389/fmars.2021.740958 | doi-access=free | title=Genomics-Based Phylogenetic and Population Genetic Analysis of Global Samples Confirms Halophila johnsonii Eiseman as Halophila ovalis (R.Br.) Hook.f. | date=2021 | last1=Waycott | first1=Michelle | last2=Van Dijk | first2=Kor-Jent | last3=Calladine | first3=Ainsley | last4=Bricker | first4=Eric | last5=Biffin | first5=Ed | journal=Frontiers in Marine Science | volume=8 | hdl=2440/134004 | hdl-access=free }}</ref> |
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==References== |
==References== |
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Revision as of 18:46, 22 March 2024
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| Closeup of a bed of Johnson's seagrass | |
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| Species: | H. johnsonii
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| Binomial name | |
| Halophila johnsonii Eiseman and McMillan[2]
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Halophila johnsonii, or Johnson's seagrass, is a small, asexual seagrass in the family Hydrocharitaceae (the "tape-grasses"). It occurs only on the southeastern coast of Florida, and was the first marine plant listed on the United States endangered species list, though it was removed from listing in April 2022.[3] Female flowers have been observed, but even with decade long observational studies, neither male flowers nor seed have ever been observed.[2]
It may have the most limited distribution of all seagrasses. It occurs only in lagoons along roughly 200 km of the Florida coastline between Sebastian Inlet and the northern part of Biscayne Bay, where it grows in small patches of a few centimeters to a few meters in diameter at depths ranging from the intertidal zone down to 3 meters.[2]
Prior to 1980, the species designation was uncertain. It was sometimes referred to as either Halophila decipiens or H. baillonis Ascherson, despite most closely resembling H. ovalis.[2]
Morphologically, Johnson's seagrass is recognized by the presence of pairs of linearly shaped foliage leaves, each with a petiole formed on the node of a horizontally creeping rhizome. The rhizome is located at or just below the sediment surface and is anchored to unconsolidated substrate by unbranched roots. The leaves are generally 2-5 cm long (including the petioles), and the rhizome internodes rarely exceed 3-5 cm in length, making this species appear diminutive relative to the larger seagrasses.[2]
Both the Green sea turtle and the West Indian manatee are known to feed upon the plant, as well as some herbivorous fish. However, the main threat to species survival is probably human activity.[2] Processes that threaten the plant include eutrophication, dredging, turbidity, and thermal pollution.[4]
Removal U.S. Federal List of Threatened and Endangered Species
In 2022 the National Marine Fisheries Service (NMFS) and National Oceanic and Atmospheric Administration (NOAA) ruled to remove Halophila johnsonii (Johnson's seagrass) from the Federal Endangered Species Act (ESA).[5] This ruling was based on recent genetic data obtained that show that Johnson's seagrass is not a genetically unique taxon. Johnson's seagrass is genetically similar to the Indo-Pacific species, H. ovalis, based on findings from multiple publishing's. As Johnson's seagrass is not genetically diverse, it no longer meets the requirements set by the ESA to be considered a species. The ESA defines a species as "any subspecies of fish or wildlife or plants, and any distinct population segment of any species of vertebrate fish or wildlife which interbreeds when mature 16 U.S.C. 1532". All gene samples of Johnson's seagrass from Indian River Lagoon over a 17 year study were genetically uniform. In the same study it was determined that due to the lack of genetic diversity, Johnson's seagrass was a clone of H. ovalis, closely related to populations in Africa and Antigua. The clone may be derived from a recent introduction from one of those regions.[6]
References
- ^ Short, F.T.; Carruthers, T.J.R.; van Tussenbroek, B.; Zieman, J.; Kenworthy, W.J. (2010). "Halophila johnsonii". IUCN Red List of Threatened Species. 2010: e.T173324A6990996. doi:10.2305/IUCN.UK.2010-3.RLTS.T173324A6990996.en. Retrieved 24 December 2022.
- ^ a b c d e f National Marine Fisheries Service. 2002. Recovery plan for Johnson's Seagrass (Halophila johnsonii). Prepared by the Johnson's Seagrass Recovery Team for the National Marine Fisheries Service, Silver Spring, Maryland.[1]
- ^ "Endangered and Threatened Wildlife and Plants; Removal of Johnson's Seagrass From the Federal List of Threatened and Endangered Species Including the Corresponding Designated Critical Habitat". unblock.federalregister.gov. 2022-04-14. Retrieved 2023-07-26.
- ^ Halophila johnsonii. The Nature Conservancy.
- ^ "Federal Register :: Request Access".
- ^ Waycott, Michelle; Van Dijk, Kor-Jent; Calladine, Ainsley; Bricker, Eric; Biffin, Ed (2021). "Genomics-Based Phylogenetic and Population Genetic Analysis of Global Samples Confirms Halophila johnsonii Eiseman as Halophila ovalis (R.Br.) Hook.f." Frontiers in Marine Science. 8. doi:10.3389/fmars.2021.740958. hdl:2440/134004.
External links
- Removal of Johnson's Seagrass From the Federal List of Threatened and Endangered Species NOAA Fisheries page with details of de-listing of Johnson's seagrass