Macrobenthos

What are benthic macrofauna? (continued)

Choice of a 1.0 or 0.5 mm sieve aperture is arbitrary. In estuarine sediments there are large amounts of organic detritus which needs to be sorted under a microscope to find the animals. Compared to samples collected with a 1.0 mm sieve, samples collected with a 0.5 mm sieve take 3-4 times longer to sort and many of the extra animals retained are juveniles that can not be identified to species. Since this work required identification to species we considered it more appropriate to use a 1.0 mm sieve and use the time saved to sort a larger sample.

During our survey 44,477 animals belonging to 275 taxa were collected. The most common group were annelid worms (33% of species, 20% of individuals), crustaceans (32% of species, 43% of individuals) and molluscs (18% of species, 30% of individuals). Unlike the river samples where insects are an important component of the benthos, insects made up only 4% of the species and 2% of the individuals in the estuarine samples.