Engelmann's sea grass (Halophila engelmannii)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Plantae · Phylum: Tracheophyta · Class: Magnoliopsida · Order: Alismatales · Family: Hydrocharitaceae · Genus: Halophila.

Accepted name: Halophila engelmannii · Authority: Ascherson, 1875 · Taxonomic status: accepted · AphiaID: 374722.

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=374722 (CC BY 4.0). Accessed 2026-09-25.

Biology and life history (SeaLifeBase)

Measured values published by SeaLifeBase for Halophila engelmannii. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Habitat zone: sessile · Aquarium trade: never/rarely.

Source: SeaLifeBase species summary (SpecCode 141792) — https://www.sealifebase.se/summary/Halophila-engelmannii.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-25.

Distribution and occurrence records (GBIF)

6,329 georeferenced occurrence records for Halophila engelmannii are published through GBIF from 5 countries or marine areas. The map above plots 7 distinct locations from a sample of 3,000 records, omitting 16 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.

Most records by country or area: United States of America (6,300); Mexico (23); Bahamas (3); Belize (2); Cayman Islands (1).

The full country table, WoRMS marine regions and the sampling notes are on this species' Distribution page.

Source: GBIF Occurrence Search (taxonKey 5329618) — https://www.gbif.org/occurrence/search?taxon_key=5329618&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=374722 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-25.

Conservation status (IUCN Red List)

The IUCN Red List assesses Halophila engelmanni Asch. as Near Threatened (code NT). No trend, population estimate or threat analysis is given here, because none is available from this source without the Red List API; follow the source link for the full assessment, including its date.

Source: IUCN Red List of Threatened Species (taxon 173337) — https://www.iucnredlist.org/species/173337/0; GBIF IUCN Red List category endpoint (taxonKey 5329618) — https://api.gbif.org/v1/species/5329618/iucnRedListCategory. Accessed 2026-09-25.

Description and natural history (Wikipedia)

Halophila is the only genus of seagrass lacking basal sheaths on the leaf stems. Like other seagrasses, Halophila engelmannii has rhizomes that run along near the surface of sand or mud, with roots at the nodes to anchor them in place.

Each leaf stem grows from a node and has a pair of scales halfway up and another pair at the base of the leaf blades. There are 4 to 8 blades on each stem, each of which is up to 30 mm long and 6 mm wide. Each blade is oval, has 6 to 8 veins and a finely serrated margin.

Halophila engelmannii is found on the coasts of Florida, Texas, the Bahamas, Cuba and the West Indies. It can grow in deeper waters than do some other species of seagrass, at depths down to 14.4 m. It is one of three species of Halophila found in the Indian River Lagoon, Florida, the others being Halophila decipiens and Halophila ovalis in the form of Johnson's seagrass. They often form mixed seagrass meadows at greater depths than other seagrasses normally grow.

Flowering occurs in the early summer when the water temperature reaches at least 22 C. Fragments of the plant that become detached are able to grow into new plants. The seagrass meadow acts as habitat and food source for many invertebrates and fish. In the Indian River Lagoon, animals that feed on Halophila engelmannii include sea turtles, sea urchins, parrotfish, surgeonfish and possibly pinfish. The sea slug Elysia serca preferentially feeds on it by sucking sap.

Source: Wikipedia: Halophila engelmannii — https://en.wikipedia.org/wiki/Halophila_engelmannii (CC BY-SA 4.0). Accessed 2026-09-25.