Macroalgae and Cyanobacteria

Macroalgae (fleshy and calcareous seaweeds), along with sponges, stony and soft corals, hydroids, bryozoans, and tube-building polychaete worms are the critical building blocks of biological habitats of nearshore hardbottom reefs of east Florida. Physical characteristics of these foundation species enhance available shelter for fish and invertebrates, stabilize substrate, and alter water flow and sedimentation impacts. The structure of macroalgal assemblages is much like that of terrestrial forests with “canopy” and “understory” species that provide micro-habitat between layers, cycle detrital material, as well as form the energetic basis of the marine trophic food web. Turf and upright macroalgae provide refuge and foraging habitat that support conspicuous and cryptic organisms such as amphipods, sea urchins, juvenile lobster, crabs, shrimps, polychaetes, and juvenile fishes. Further, macroalgae, especially turf species, form the primary diet of juvenile green turtles as well as diverse fish species that consume micro- or macroalgae at different life stages or throughout their life. Data compiled from multiple studies revealed that over 300 macroalgae and cyanobacteria taxa exist on Florida’s east coast nearshore reefs. This is likely a conservative value. One general observation is that macroalgae biomass on nearshore reefs of east Florida appears comparatively higher near the biogeographic transition zone of warm-temperate and subtropical waters. This and other distribution patterns may be the result of latitudinal differences in nutrients (a function in part of the proximity of oligotrophic waters of the Florida Current), wave dynamics, and/or differences in fish/invertebrate grazing communities. The latter explanation may be further supported by the relatively higher composition of physically- and chemically-defended macroalgae present in southeast Florida.