Respiration and ingestion rates of the filter-feeding bivalve Musculista senhousia: implications for water-quality control

To evaluate the effect of filter-feeding bivalves on water quality, batch a nd now type measurements were recorded to estimate the respiration and inge stion rates of Musculista senhousia, which predominates the macrobenthos of Lake Nakaumi, Japan. The results for the respiration rate experiments had a low stable rate at about 15 mg O-2 day(-1) DFW g(-1) (where DFW means dry flesh weight) at low temperatures (between 5 degrees C and 10 degrees C) t hat increased at middle and high temperatures (from 10 degrees C to 30 degr ees C), reaching a maximum rate of about 200 mg O-2 day(-1) DFN g(-1) at 30 degrees C. The dependence of respiration rate on temperature is significan t, especially between 10 degrees C and 15 degrees C (Q(10) = 6.9). The vert ical 2-BOX numerical model showed that continuous stratification of the wat er column must be averted if M, senhousia are to survive. Ingestion rate of particulate matter also increased with temperature between 10"C and 20 deg rees C. Ingestion rates at 30 degrees C, after being incubated for more tha n 1 day, were almost the same as ingestion rates at 20 degrees C, Filtratio n rates were calculated from concentrations of chlorophyl a (Chl.a), partic ulate total phosphorus (PTP) and particulate total nitrogen (PTN). Obvious differences were observed between the filtration rate calculated from the C hl.a concentration compared to those from PTP and PTN. This may imply that M, senhousia selectively ingested a particular species of phytoplankton, Th e horizontal 2-BOX model showed a relationship between the Chl.a concentrat ion in L. Nakaumi and the water exchange rate. The ingestion potential of o rganic matter by M. senhousia is greater than those of the nutrient loads i n the field and has less risk of depleting dissolved oxygen (DO) in the bot tom layer. If. therefore, the phosphorus and nitrogen supply to M, senhousi a increased, and adult M, senhousia are collected and removed efficiently, water quality in L. Nakaumi would improve. (C) 2000 Elsevier Science B.V, A ll rights reserved.