厚壳贻贝的同化率及其生物沉积作用

Assimilation efficiency and biodeposition of mussel Mytilus crassitesta

2001年3～9月在青岛海区自然养殖状态下,利用沉积物收集器测定厚壳贻贝(Mytiluscrassitesta)的生物沉积及其对物质的输运,并采用灰分比例法计算厚壳贻贝的同化率。结果显示,厚壳贻贝的同化率分别为:小个体(壳长42～49mm)43 2%～59 9%、中等个体(壳长54～60mm)41 3%～56 1%、大个体(壳长65～74mm)47 6%～53 5%,平均值分别为51 6%、49 5%和52 5%。厚壳贻贝通过生物沉积作用加速海洋中颗粒物质的沉积,生物沉积率随个体的增大而增加,呈正相关关系,分别为:小个体[(42 3±4 4)～(77 9±10 8)]mg·ind-1·d-1,中等个体[(68 5±5 8)～(134 1±12 7)]mg·ind-1·d-1和大个体[(83 4±10 4)～(167 1±10 8)]mg·ind-1·d-1。海水温度和环境中饵料数量是影响厚壳贻贝的生物沉积的重要因子。

Studies on marine bivalves have demonstrated that suspension-feeding bivalves scan influence the function of ecosystems to a great extent.In dense populations,bivalves can dominate total ecosystem metabolism,nutrient cycling,and grazing of primary producers.Mussel(Mytilus crassitesta) is not only one of the most important aquaculture bivalves,but also the most widely distributed species in the neritic waters in the Bohai Sea and the Yellow Sea.Mussels farming has been bringing great economic benefit,and the filtration,excretion and ejection of mussels would influence the neritic ecosystem.To estimate the effects of mussels on neritic ecosystem,the experiments were monthly conducted near Xiao Qingdao Island(Qingdao) from March to September 2001.The biodeposition by Mytilus crassitesta and the effects of biodeposition on material flux were measured using biodeposit collector under natural cultivation conditions.The assimilation efficiency of Mytilus crassitesta was determined with the method used by Conover(1966) and Granford(1990).The mussels used in experiments,shell length 79.8-125.0 mm and dry tissue weight 0.96-3.35g,were collected from experimental ship bottom near Xiao Qingdao Island.The mussels were divided into three groups according to their shell length,which were small size (80-95mm),middle size (95-110mm) and big size (110-125mm).For each group,three parallel experiments were set.As determined,the assimilation efficiency of Mytilus crassitesta was 43.2%-59.9%,41.3%-56.1% and 47.6%-53.5% for small size,middle size and big size of Mytilus crassitesta,and the mean values were 51.6%,49.5% and 52.5%,respectively.The biodeposition rates were(42.3±4.4)-(77.9±10.8)mg·ind-1·day-1,(68.5±5.8)-(134.1±12.7)mg·ind-1·day-1 and (83.4±10.4)-(167.1±10.8)mg·ind-1·day-1 for each group.The amount of biodeposit was correlated positively with the shell length and body weight.With the water temperature rising form March to September,the Chla concentration in sea water increased from (1.6±0.3)g·L-1 to (7.3±0.5)g·L-1and reached peak values in June,then went down until September.TPM,POM,POC and PON had the same changing trend.As a consequence,the biodeposition by each group increased from(42.3±4.4)mg·ind-1·day-1 to (77.9±10.8)mg·ind-1·day-1,(68.5±5.8)mg·ind-1·day-1 to (134.1±12.7)mg·ind-1·day-1and (83.4±10.4)mg·ind-1·day-1 to (167.1±10.8)mg·ind-1·day-1,then decreased to (50.4±7.6)mg·ind-1·day-1,(93.4±9.1)mg·ind-1·day-1 and (122.6±13.7)mg·ind-1·day-1 in August or September,respectively.Those demonstrated that water temperature and food concentration were important factors to affect biodeposition of Mytilus crassitesta.