Benthos of Adjacent Mangrove, Seagrass and Non-vegetated Habitats in Rookery Bay, Florida, U.S.A.

Abstract

Benthic faunal abundances and biomasses in adjacent mangrove, seagrass and non-vegetated mud habitats were compared in Rookery Bay, Florida, U.S.A. Although all habitats were intertidal, mangroves received the shortest duration of flooding, and non-vegetated mud received the longest. Replicate cores were taken at high tide in each habitat in July, September and December 1988, and in April 1989. Seagrass substrates were low organic content sands, whereas mangrove and non-vegetated substrates were high organic content sandy clays. Over 300 taxa were recorded, most of them relatively rare, and only 32 taxa were considered dominant (averaging ≥636 individuals m−2or five core−1in any habitat at a given time). Seagrass and non-vegetated mud faunas were more diverse than those of mangrove substrates. Total densities were always higher in red mangrove (Rhizophora mangle) peat than elsewhere, averaging 22 591 to 52 914 individuals m−2. Densities in mixed seagrasses ranged between 6347 and 23 545 individuals m−2, while those in non-vegetated mud ranged between 3611 and 22 465 individuals m−2. Biomasses, however, were always higher in either seagrasses (15·7–87·4 g wet weight m−2) or non-vegetated mud (11·9–26·2 g m−2) than in mangroves (3·6–8·2 g m−2). Tanaids and annelids were the numerical dominants, reaching maximum densities of 35 127 and 31 388 m−2, respectively, in mangroves. Annelids were also the dominant biomass in most habitats each month. Variation in densities of most of the 32 dominant taxa were related to habitat not time. Each habitat harboured four to eight taxa that were significantly more abundant there than in alternate habitats. Feeding guild analysis indicated few differences among habitats, as surface deposit feeders and carnivores were predominant. Red mangrove appear capable of functioning in a manner similar to intertidal marsh habitats by providing high densities of small prey items for mobile consumers able to exploit the intertidal zone during high tide. Experimental verification of this function remains necessary.