Feeding behaviour of the green mussel, Perna viridis (L.): : Responses to variation in seston quantity and quality

Abstract

Mussels, Perna viridis (Linnaeus), were exposed to different food suspensions consisting mixtures of sediment and microalgae (the diatom Skeletonema costatum and the green microalga Dunaliella tertiolecta). The designed ranges for the contents were: total particulate matter (TPM: mg l −1) 4.46–24.19, particulate organic matter (POM: mg l −1) 0.75–7.19, particulate inorganic matter (PIM: mg l −1) 2.38–17.00, and organic content of seston ( f) 0.12–0.64. Clearance rates, rates of filtration, pseudofaeces production, ingestion and absorption, were analyzed at these various food quantity and quality. Clearance rates decreased exponentially with the increase of the particulate organic matter. Pseudofaeces production was a positive function of the rate of particle filtration and more pseudofaeces was rejected when filtered matter had a lower organic content. The ingestion rate decreased with the increase of the organic content of seston but the organic ingestion rate increased slowly with the organic content of seston. The pre-ingestive food selection enhanced the rate of particulate organic matter ingestion and the organic enrichment of ingested matter became more pronounced for diets of low food value, of which most filtered matter was rejected as pseudofaeces. The absorption rate was dependent on the content of particulate organic matter and the absorption efficiency increased as the organic content of ingested matter increased. Therefore, feeding processes of green mussels appear well adapted to cope with changes in food quantity and quality. At high particle concentrations but simultaneous low food values in the water column, green mussels have high rates of seston filtration and pseudofaeces production, together with preferential organic ingestion act to compensate for the dilution of organic matter in suspension. The results will be discussed with respect to spatial variations of the food environment and differential growth of P. viridis in Hong Kong waters.