Feeding rate and sediment reworking by the holothuroid Holothuria tubulosa (Echinodermata) in a Mediterranean seagrass bed off Ischia Island, Italy

Values of Holothuria tubulosa feeding rate range over 1 order of magnitude [from 0.049 to 0.489 g dw sediment h-') depending on individuals' size and environmental conditions. Feeding rate is correlated with season (increase of water temperature leads to increase of feeding rate) and with the nycthemeral cycle (individuals being more active at night). Feeding rate data allowed the yearly amount of sediment reworked by the H. tubulosa population of the Lacco Ameno seagrass bed to be calculated. Obtained values differ ~n the lower and upper part of the meadow (5.9 and 12 9 k g dw sediment n1r2 yrr' respectively), according to local differences in population structure, light and temperature regime.