DEVELOPING AN EFFICIENT MACROFAUNA MONITORING INDEX FROM AN IMPACT STUDY - A DREDGE SPOIL EXAMPLE

Data from an initial impact study were used to develop a labour-effici ent index for biological monitoring of dredge spoil disposal. Each of 12 indicator species was assigned a score, based primarily on the rati o of its abundance in control vs impacted samples. The 'Index' value w as the average score of those indicator species present in the sample. The Index was tested during a second survey. Sample processing for In dex calculation took only 25% of the time required to process all macr ofauna, The Index value provided a sensible, semi-quantitative indicat ion of impact on benthic macrofauna, Index values of <2, 2-6 and >6 we re indicative of 'severe','patchy' and 'no' impact respectively. Mean Index value correlated with mean macrofaunal richness (r=0.93, P<0.05) and abundance (r=0.92, P<0.05), While the Index is site-and impact-sp ecific, the process of developing efficient monitoring tools from an i nitial impact study should be widely applicable. (C) 1998 Elsevier Sci ence Ltd. All rights reserved.