Variation in meiofaunal abundance and composition across an estuarine bay: Are meiofauna just macrofauna writ smaller, or do they display different patterns?

Is division of marine animals into macrofauna and meiofauna merely an
arbitrary convenience, or, as has been claimed, does their size difference
render them distinct and independent entities evolved under different
ecological constraints? To investigate this, the ecological patterns of
meiofaunal distribution, abundance, and composition were investigated
across the disparate regions of Knysna estuarine bay (South Africa). The
locality was represented by ten specific seagrass and bare-sediment sites
at which the equivalent macrofaunal characteristics had recently been
established. Thus it was possible to compare meiofaunal and macrofaunal
responses to the same suite of contrasting situations. Nematodes, copepods
and ostracods, totalling 95.7% of numbers, dominated the epibenthic
meiofauna which showed low (but not necessarily locally atypical)
abundance: per core sample values of 19-886 (mean 211) 10 cm-2. Numbers
were subequal or greater in seagrass beds than in bare sediment, and
peaked in the clean delta sands of the mouth. Relative abundance of total
macro- and meiofauna showed comparable patterns along the system's
longitudinal axis, but each major component taxon, whether macrofaunal or
meiofaunal, responded differently to the gradients concerned and no common
within-group or contrasting between-group macrofaunal or meiofaunal
responses were apparent. Indeed the strongest correlation was between
distribution and abundance of the meiofaunal harpacticoids and macrofaunal
gastropods. The macrofaunal 'opportunistic polychaete to
amphipod' and meiofaunal 'nematode to copepod' indices of
ecological quality yielded differing (but in both cases unrealistic)
results. The Knysna macro- and meiofauna did not behave as distinct and
discrete ecological entities, their individual component taxa displaying
disparate patterns independent of their allocation into the two size
classes.