Factors influencing biodeposit production by the New Zealand freshwater mussel Echyridella menziesii

Laboratory experiments on the New Zealand freshwater mussel Echyridella menziesii were used to investigate the short-term effects (7–8 days) of food type on rates of biodeposition and benthic substrate respiration. Post-feeding biodeposition rates ranged from 0.34 to 1.52 mg g−1 h−1 (mean = 0.50 mg g−1 h−1) and were unaffected by the addition of toxin-producing Microcystis. Addition of suspended sediment (30 mg L−1) visibly altered substrate composition, and increased total and inorganic biodeposit production rates by 24–33% compared to mussels fed commercial phytoplankton stock. Biodeposition rates of mussels in lake bed substrates were 38% higher than those in silica sand for identical feeding regimes, suggesting that a significant proportion of material produced in this experiment could have been derived from feeding on organic matter in the lake bed sediments. Respiration rates were higher in treatments with Microcystis but were unaffected by the presence of mussels. This laboratory study suggests that biodeposition by E. menziesii is resilient to short-term exposure to Microcystis, and highlights the ability of mussels to alter benthic substrate composition by incorporating suspended sediment into substrates.

本研究以新西兰淡水贻贝（Echyridella menziesii）为实验对象开展实验室培育实验，旨在探究为期7~8天的短期周期内，食物类型对生物沉积速率及底栖基质呼吸速率的影响。摄食后的生物沉积速率范围为0.34~1.52 mg·g⁻¹·h⁻¹（均值为0.50 mg·g⁻¹·h⁻¹），且不受添加产毒微囊藻（Microcystis）的影响。添加悬浮沉积物（30 mg·L⁻¹）可显著改变底栖基质组成；与投喂商品浮游植物饵料的贻贝组相比，该组总生物沉积量及无机生物沉积量的生成速率提升24%~33%。在相同投喂方案下，湖床基质中贻贝的生物沉积率较石英砂基质组高38%，这表明本实验中生成的大部分物质可能来源于对湖床沉积物中有机质的摄食。添加微囊藻的实验组呼吸速率更高，但贻贝的存在对呼吸速率无显著影响。本实验室研究表明，E. menziesii的生物沉积作用对短期暴露于微囊藻具有抗逆性，同时证实了贻贝可通过将悬浮沉积物纳入底栖基质来改变其组成。