Short-term impact of clam harvesting on sediment chemistry, benthic microbes and meiofauna in the Goro lagoon (Italy)

The effects of clam harvesting on sediment organic matter, bacteria, heterotrophic nanoflagellates, ciliates and meiofauna were investigated through a short-term experiment carried out in the Goro lagoon during summer 2000. Sediment samples were collected in two areas: an impacted and an undisturbed (both 25 m2), before and after (5, 24 and 48 h) clam harvesting. Immediately after sediment reworking, total organic matter content decreased for about 20%. Different organic compounds displayed different redeposition patterns resulting in the alteration of the biochemical composition of sediment organic matter. Bacterial abundance decreased significantly after clam harvesting, but microbial enzymatic activities and bacterial C production were relatively unaffected. Heterotrophic nanoflagellates displayed a positive response to sediment disturbance, whereas ciliate and meiofaunal abundance did not display any significant response. Results of this short-term field experiment suggest that clam harvesting determines a positive impact on nutritional availability of sediment organic matter, thus facilitating organic carbon transfer to higher trophic levels of the benthic microbial loop.