Impact of macroalgal blooms and wader predation on intertidal macroinvertebrates: experimental evidence from the Mondego estuary (Portugal)

The effect of macroalgal blooms and predation by wading on benthic macroinv ertebrates was examined in the Mondego estuary, Portugal, during spring 199 7. Introduced macroalgal cover and exclusion of predators were used to exam ine changes in density of macroinvertebrates using univariate and multivari ate analyses. There was no evidence of changes in numbers of macroinvertebr ates due to predation. Macroalgae were, however, responsible for a decrease in abundance of the worms Amage adspersa (Grube) and Streblospio shrubsoli i (Buchanan), and a substantial increase in numbers of Capitella capitata ( Fabricius). The density of the worm Hediste diversicolor (O.F. Muller) incr eased during the first month and decreased after 2 months, associated with macroalgal cover. There were no differences in abundances of macroinvertebr ates between different depths. Overall, only polychaete species were affect ed by macroalgae. Multivariate analysis also showed clear differences in as semblages of macroinvertebrates due to the presence of macroalgae. (C) 2000 Elsevier Science B.V. All rights reserved.