刺参围堰养殖中大叶藻的生态功能

Ecological function of seagrass Zostera marina L.bed in sea cucumber pond

为阐明围堰池塘内海草——大叶藻的生态功能并为将其引入刺参池塘养殖提供理论基础,对大叶藻区和裸露砂质底质区的温度、溶氧进行了比较测定,对刺参及其食物组成的同位素进行了分析,并与邻近自然海域草场系统进行对比。结果显示,春夏季大叶藻区底部温度比裸露砂质底质区温度低约0～0.33°C;0～25%的低大叶藻盖度下,海草区和裸露底质区溶氧差异不显著,50%～100%的中高盖度下,海草区表层溶氧显著高于裸露底质区,高约0.12～0.62 mg/L,底层溶氧低于裸露底质区,约0～0.38 mg/L;春季末,该海草环境下的刺参δ13C和δ15N比值分别为–15.27‰和8.11‰,具有与相邻自然草场系统中刺参明显不同的同位素特征值（–20.12‰和10.95‰）。混合模型的分析表明,其食物组成中来自大叶藻的贡献约为13%～52%,高于底栖硅藻（4%～49%）、悬浮颗粒有机物POM（23%～39%）以及附着生物（0～22%）。而邻近的自然草场中,来自POM和褐藻海蒿子的食物贡献最大,0.95置信水平下的置信区间（CI）分别为24%～54%和1%～53%,而海草丛生大叶藻的贡献为0～27%。本研究表明,大叶藻可以在一定程度上降低夏季池塘底部水温,增加水体溶氧,同时为刺参提供重要的食物来源,这在池塘组成相对简单的环境下是尤为重要的。

In order to determine the ecological function of seagrass Zostera marina L. in sea cucumber culture, water temperature and dissolved oxygen in the eelgrass bed of a sea cucumber pond were determined and compared with the adjacent sandflat. Food sources used by sea cucumber Apostichopusjaponicas were determined by comparing their stable isotope signatures （δ13C, δ15N） with those of food source. Proportions of different carbon sources were estimated using the SIAR mixing model on δ13C and δ13N values. The results showed that water temperature at eelgrass patch bottom was 0 to 0.33 ℃ lower than the naked sandflat. Surface and bottom dissolved oxygen showed no differences between low eelgrass coverage （0 to 25%） area and sandflat, while in area with mid-to-high eelgrass coverage, resolved oxygen was 0.12 mg/L-0.62 mg/L higher in surface water. Bottom dissolved oxygen was lower in mid-to-high eelgrass coverage （0 to 0.38 mg/L）. Stable isotope signatures δ13C and δ15N of sea cucumbers A. japonicus was -15.27% and 8.11‰, which differed from those in adjacent coastal seagrass habitat （-20.12% and 10.95‰）. A strong role of Z. marina matter as food sources was indicated from the estimation of SIAR mixing model. The model gave higher upper and lower limits of 0.95 credibility interval （CI） （from 13% to 52%） for Z. marina relative to microphytobenthos, particle organic matter POM and epiphyte, for which 0.95 CI ranged from 4% to 49%, 23% to 39% and 0 to 22%, respectively. However in adjacent coastal seagrass bed A. japonicus showed different stable isotope signatures with -20.12‰ and 10.95‰ for δ13C and δ15N, respectively. 0.95 CI of SPOM and brown seaweed ranged from 24% to 54% and 1% to 53% while seagrass Z. caespitosa matter only contributed to 0-27%. These results demonstrate that Z. marina could reduce the bottom temperature in the pond and increase surface dissolved oxygen. Cultured A. japonicus consume relatively higher amounts of Z. marina than other organic sources in this pond. This implied the importance of seagrass habitat in the pond environment. The importance of seagrass habitats in sea cucumber pond was discussed and the necessity and feasibility to transplant seagrass to sea cucumber pond was highlighted.