Local patchiness of macrobenthic faunal abundance displays homogeneity across the disparate seagrass systems of an estuarine bay

摘要

Spatial variation in the degree of local patchiness of macrobenthic assemblage abundance was assessed across the 16 km(2) warm-temperate Knysna estuarine bay (South Africa) where the seagrass Zostera (Zosterella) capensis grows under a broad spectrum of environmental conditions and supports invertebrate assemblages at a wide range of local density ( 2000- 320000 ind. m(-2)). Macrobenthic assemblage abundance at all 27 representative sites examined displayed low-level but highly-significant spatial patchiness (mean Lloyd's index, I-P = 1.148). Except at high tidal levels, however, the magnitude of this local patchiness did not vary statistically across the system (CV 4.3%) regardless of assemblage abundance, location or species composition. Patchinesses well within +/- 1 standard deviation of Knysna's value also characterise an equivalent Z. (Zosterella) capricorni assemblage in subtropical Queensland (I-P 1.169) and another, Z. (Zosterella) noltei, assemblage in cool-temperate England (I-P 1.135), suggesting that at local scales intertidal dwarf-eelgrass macrobenthic abundance displays a characteristic level of patchiness.