Turtle Grass Colonized by Detritivores
© Richard Mieremet, NOAA

LIFE IN THE SEAGRASSES

Bacteria and Fungi

Bacteria and fungi are responsible for the decomposition of dead seagrass blades. Microfauna and meiofauna colonize the dead seagrass blades, feeding on the bacteria and fungi as well as on the dissolved organic matter released from the decomposing blades. These dissolved organics also support phytoplankton and zooplankton which in turn provide prey for organisms further up the food web.

Caulerpa mexicana
© John Huisman

Algae

Lacking a firm substrate for attachment, seagrass beds contain benthic macroalgae attached to sediments, rocky outcroppings, and the seagrasses themselves. Calcareous algae lives among the seagrasses, producing calcium carbonate which eventually becomes incorporated into the surrounding sediments. Drift algae form large unattached masses along the sea bottom and drift about with any water movement.

Padina gymnospora
© John Huisman

Red algae and brown algae are also common within seagrass habitats. In addition to calcareous algae, the majority of drifting algal masses are species of red algae.

Epiphytes Growing on Turtle Grass
courtesy South Florida Water Management District

Seagrasses dramatically increase the surface area of the habitat for the attachment of epiphytes. On turtle grass (Thalassia testudinum) alone, over 100 species of epiphytic algae have been documented. Epiphytes cover seagrass blades more at the tips than toward the bases in order to receive more sunlight than those lower on the blade. These epiphytes reduce seagrass growth due to shading. Epiphytes, along with the seagrass blades, eventually become part of the detritus.