Structural changes in benthic macrovegetation and associated epibenthic faunal communities

Abstract

Mobile epibenthic fauna was quantitatively assessed using a drop-trap in two shallow-water (0 to 1.5 m) soft-bottom areas on the Swedish west coast during spring and autum in three to four years during the period 1981 to 1990. Changes in commmunity structure and distribution of benthic macroalgae with increased dominance with filamentous algae were observed in the two study areas. Concurrent changes in both quantity and structure of mobile epibenthic fauna were registered, suggesting a causal relationship. Increased abundance of benthic epifauna and a shift in species composition were observed when increases from low to moderate vegetation cover occured. Heavy overgrowth by filamentous algae on Zostera marina was accompanied by a reduction in the epibenthic faunal quantity. Shallow coastal areas have high value as feeding grounds and nursery areas for many commercially important fish species. A change in habitat structure will probably have considerable consequences for these species. Among coastal fish populations, eel would be favoured by an increase of filamentous algae, whereas plaice would be negatively affected.