Distribution of macrobenthic crustaceans associated with Thalassia, Halodule and bare sand substrata

Abstract

The influence of macrophyte biomass and species composition on the distribution of macrobenthic crustaceans was examined in 2 vegetated and 2 unvegetated grass bed microhabitats under similar physical-chemical conditions. Vegetated habitats consistently supported higher numbers of individuals and species than either of the unvegetated zones. Correlations between plant biomass in each microhabitat and both animal numbers and diversity suggested that seagrass biomass was a key organizing factor in macrophyte-associated faunal assemblages. The thin-bladed Halodule wrightii supported similar crustacean abundance per core, density and species richness to those found on widebladed Thalassia testudinum, contradicting the predictions of Kikuchi and Peres (1977) that widebladed magnozosterids should have a more abundant and diverse fauna relative to thin-bladed parvozosterids. In addition, after standardization to numbers of individuals per unit plant biomass (or surface area), H. wrightii supported higher abundance than T. testudinum suggesting that seagrass species composition is more important to faunal organization than previously thought. Although similar suites of species inhabited each substratum, relative abundances of individual species were markedly different among the microhabitats. Greatest differences occurred between vegetated and unvegetated zones. Few of the 24 dominant crustaceans (those species with abundances of 1 % or more of the total number of individuals collected) had significantly greater abundances per core on one seagrass species relative to the other. Three species were more abundant on T. testudinum while only 1 occurred in greater numbers on H. wn'ghtii. However, when species abundances per unit plant weight (or surface area) were compared between the 2 vegetation forms, 7 species were significantly more abundant on H. wrightii; only 2 species occurred in higher numbers on T. testudinum. Distribution of crustaceans among seagrass microhabitats appeared to be a complex function involving faunal habitat choice and predation pressure, both of which are affected by the species and biomass of seagrass present.

A Comparison of Macroepifauna Among Vegetated and Unvegetated Habitats in a South Florida Estuary Using a Passive Sampling Gear

“…Our findings that seagrasses support greater overall abundance, richness, and diversity relative to unve- getated substrate are consistent with earlier reports that structurally complex habitats support more individuals and species (Lewis, 1984;Jordan et al, 1997a). The basket shell, pinfish, and rainwater killifish (Lucania parva), for example, displayed dramatic preferences for seagrass over unvegetated substrate, and this contributed to these differences.…”

“…Differences in nekton exist between Thalassia and Halodule (Springer and McErlean, 1962;O'Gower and Wacasey, 1967;Stoner, 1983) because of biomass differences and perhaps because wide-bladed 17wlassia is more structurally complex than narrow-bladed Halodule and Sy1ingodiu.m (Virnstein et a!., 1987;Brown-Peterson et a!., 1993). Stoner (1983) and Lewis (1984) found that for monospecific seagrass beds, fish and crustacean abundance were explained by aboveground seagrass biomass. Stoner (1983) found that in such areas blade density predicted fish abundance better than seagrass biomass, and reported that blade-dense Halodule beds held greater numbers of small fishes than either Thalassia or Syringodium.…”

“…Comparisons of epifauna found in seagrass meadows and adjacent bare substrates have shown that diversity and abundance is higher (Thayer et al, 1975;Orth, 1977;Virnstein et al, 1983;Bell et al, 1984;Lewis, 1984;Orth et al, 1984;Sogard, 1992;Jordan et al, 1997a;Arrivillaga and Baltz, 1999) and predation lower (Virnstein et al, 1983;Summerson and Peterson, 1984) in vegetated habitats. Arrivillaga and Baltz ( 1999), for example, found that crustacean and fish abundances were 7 and 20 times higher, respectively, in meadows of turtle grass ( Thalassia testudinmn) than over sand.…”

Composition and abundance of decapod crustaceans in mixed seagrass meadows in the Paraguaná Peninsula, Venezuela

“…The presence of macrophytes is a major factor that influences the presence and abundance of crustaceans, and it has been shown that vegetated microhabitats consistently support greater species richness and abundance when compared with unvegetated areas (Lewis, 1984;Casares & Creed, 2008). The species richness, abundance, and composition of crustaceans in seagrass meadows is affected by the habitat complexity; notwithstanding, the responses vary along with the characteristics of the specific community and taxa (Lewis, 1984;Bitter-Soto, 1999).…”

“…The species richness, abundance, and composition of crustaceans in seagrass meadows is affected by the habitat complexity; notwithstanding, the responses vary along with the characteristics of the specific community and taxa (Lewis, 1984;Bitter-Soto, 1999). Decapod crustaceans have an important role in structuring the community associated with beds of T. testudimun, as they constitute an important food item in the diet of several juvenile stages of fishes and other crustaceans (Heck & Weinstein, 1989).…”