MEPS 223:113-119 (2001)  -  doi:10.3354/meps223113

ABSTRACT: Most marine benthic macrofaunal species are buried in the sediment but feed on the sediment surface. We measured benthic faunal activity on the sediment surface in 0.25 m² box-cores from a 75 m depth in a Swedish fjord. The techniques used were video numeric tracking and electronic intelligent sensors, where the activity pattern was continuously recorded. During a 4 h recording, 24% of the examined surface area showed infaunal activity. When phytodetritus was added to the same surfaces, the areas searched by the fauna almost doubled over the next 4 h. Thus, the main part of the sediment surface is most probably covered daily by infaunal activity, particularly when food is available. Arms of Amphiura filiformis and A. chiajei contributed to 40-80% of the total surface area covered by faunal activity, which was >15 times that of tentaculate feeding activity of Melinna cristata. Time frequency recordings showed that the response of the Amphiura species to food supply was strong during the first 25 min, followed by a decline, which probably was related to processing and storage of food in the sediment.

KEY WORDS: Amphiura · Melinna · Video analysis · Actography · Food supply · Foraging