Benthic macrofauna richness and diversity in the Knysna Estuary: A 50 year comparison

A study was initiated in 1997 to assess the diversity, distribution and density of the benthic macrofauna of the soft intertidal sediments of the Knysna Estuary using the same collecting sites and methods reported by Day, Millard & Harrison in 1952. A two-way ANOVA has shown that there is no difference between species richness of belt transects reported in 1952 and 1997. A significant increase in species diversity as measured by the Shannon-Weiner Index (H') in quantitatively sampled sediments in the Zostera zone between 1952 and 1997 is due, it is argued, to intermittent increases in suspensoids in the water column, as a result of poor land-management practices in the catchments of the streams which have run into the estuary during this 50 year period.