The activity pattern is recorded by new techniques of real-time video tracking of the benthic activity. Electronic intelligent sensors allow the time analysis of benthic numeric objects with intensive automated recording sessions. We record the natural behaviour of several animals over 24h cycles. We also look into possible antagonistic behaviour, i.e. how animals feed when they have tubes close to each other and when feeding may occur in the same patches. Comparison is made between active motile surface deposit feeders and tubicolous surface deposit feeders. Activities of Amphiura filiformis, A.chiajei (motile burried Ophiuroids) and Melinna cristata (tubicolous Polychaete) are extracted by image analysis and quantified. Amphiura activity is restricted to its deposit feeding mode and no suspension feeding is present in the experiments. We also examine how addition of phytoplankton to the sediment will affect the feeding activity and if Amphiura and Melinna can locate patches of food. Dynamics of the response to food addition is studied.
Experiments have been conducted without gap during the whole period (27 of March 2000- 6 of April 2000). Ten 0.25 m2 plexiglas boxes have been collected from the deeper parts of the Gullmarsfjord. We found active populations at the sediment interface. We made 28 experiments with replicates within these boxes on benthic activities with a mean length of 5.8h (max 15.4h) with continuous recording and real time activity measuring. This corresponded to a total recording time of 155.8h (6.5 days of constant recording for 10 days spent in the laboratory). An image was processed by the intelligent sensor every 3 second. In the feeding activity recording sessions, 24h recordings were made with an initial recording of natural condition followed by a food addition and a record of the subsequent individual activities. Records have been processed later in Banyuls. We appreciated the easy environment provided by the facility providing a very powerful tool to drive activity measurements (thermoconstant rooms with computer facilities). Records treatment allowed to make a precise measurement of the dynamics of reaction of marine invertebrates to food addition. Importance of the fast and important response of Amphiura to food presence suggest a dominant influence in the use of particulate organic matter sedimenting within the benthic community. The general increase in benthic activity has been measured after food addition. A 10-30% increase of food gathering behaviour is recorded. This increase is mainly the fact of a few species with fast detection/reaction. Among these are Amphiura, terebellide worms, motiles Ophiodromus flexuosos and Melinna cristata. Extractions of individual activities have been made in Banyuls from the original data. This allows to compute the relative reaction to food addition within patches of individuals coming from the same benthic community. 3 complementary experiments on Brissopsis lyrifera digging activity (5-6/4/2000) have been made to record the burrowing behaviour and the length of a complete burrowing event. In these experiments images records were done with a film reconstruction associated to the urchin behaviour.