The seagrasses are an ecologically important clade of marine plants. They have the distinction of being the only fully submerged marine Angiosperms (flowering plants), and have recently been split into more than one taxonomic Family. Originally they were all grouped within the Zosteraceae, but there are now four Families where once there was just one. The other three Families are the Cymodoceaceaae, the Ruppiaceae and the Posidoniaceae. This latter Family, containing the Genus
Posidonia, is notable not only for being an efficient aquatic photosynthesising plant, but for possessing nitrogen fixation capabilities also.
Members of
Posidonia have an odd geographical distribution.
P. oceanica is endemic to the Mediterranean, but all the other members of the Genus are found around the coasts of Western Australia. No member of the Genus is found in any of the intervening 10,000 miles of ocean between those locations.
In the case of the Genus
Zostera (usually known as Eelgrasses), one species living off the coast of South Australia (possibly
Z. mucronata or Z. tasmanica[/i]) plays host to that most rococo of fishes, the Leafy Seadragon.
Seagrasses of various species are important marine nurseries for a range of fishes, including juveniles of Jacks, Fusiliers and several species of Seahorse.
Interesting that this topic should be highlighted for my attention after I spent two days visiting various aquarium shops and photographing the exotic fish there