亚热带海域玉足海参对海底营养元素循环的影响

Holothuria leucospilota is a primary deposit-feeding sea cucumber species widely distributes along the coast of subtropical South China, which has comparatively high nutritional and medicinal values. So far the influence of H. leucospilota on the subtropical coastal environment have not yet received sufficient attention, and their effects on nutrient cycling of the seabed has not been well understood. In this study, effects of the key ecophysiological processes and bioturbation of H. leucospilota on nutrient cycling of the seabed will be surveyed as follows: (1) semi-in situ flow-through systems will be established to estimated the ingestion rate of H. leucospilota; (2) the food selection and nutrient assimilation efficiencies of sea cucumbers will be evaluated by comparing the component of their guts and the sediment in their habitat; (3) the nutrient regeneration via resperation and excreation of animals will be estimated in situ using the respiration bottle; (4) in situ culture equipments will also be established to measured their growth and bioturbation processes on nutrient cycling of the seabed. Basing on these results, the C, N and P budget equations of the H. leucospilota will be established, and effects of key ecophysiological processes and bioturbation of H. leucospilota on nutrient cycling of the seabed will be estimated, and the influence of this sea cucumber on the pelagic-benthic coupling of their habitat will be evalued. Results of this study will provide useful knowledge for environmental protection and sustainable exploitation and management of sea cucumber resources along the coast of subtropical South China.

玉足海参是一种具有较高食用和药用价值的沉积食性海参，广泛地分布于我国的亚热带海域。目前该海参对亚热带海洋环境的影响尚未引起人们的关注，其在海底营养元素循环中的作用也不清楚。本研究拟从玉足海参的关键生理生态过程和生物扰动出发，以该海参对C、N、P的收支作为主线，采取现场和半现场模拟实验的方法，从以下几个方面探讨玉足海参在海底营养元素循环中所起的作用，包括：(1)采用半现场水槽模拟法考察其对沉积物的摄食率；(2)分析栖息地海参肠道内含物及海底沉积物，确定其对食物的选择与同化作用；(3)利用呼吸瓶法现场测定其呼吸排泄对营养元素的再生作用；(4)利用设施放养实验探讨其生长及生物扰动对海底营养元素循环的贡献。据此，建立玉足海参对C、N、P的收支模型，阐明其对海底营养元素循环的影响机制，并评估其在栖息地“水层—底栖耦合”中的作用。研究结果可为亚热带海洋环境保护以及海参资源的可持续开发利用提供科学依据。

本项目对大亚湾海域的玉足海参的资源进行周期性调查，探明了其自然分布情况及栖息地环境特征。在实验室内考察了玉足海参的排粪率，分析了其对沉积物的选择摄食作用。利用呼吸瓶法测定玉足海参对营养物质的排泄率。结果表明，玉足海参的分布具有明显的时空变化特征，其中东家湾海域海参多分布于离岸30m以内的海域，夏季由于深水区海底缺氧，仅分布于离岸20m以内的海域，该海域玉足海参的平均生物量为30.86g m-2。桔钓沙海域玉足海参多分布于离岸10~50m的海域，其平均生物量为53.18g m-2。各海区玉足海参的排粪率平均为136.22和145.03mg g-1d-1。根据玉足海参的分布及其排粪率，可以计算，每年东家湾和桔钓沙海域玉足海参通过摄食和排粪对海底表层沉积物的搬运能力分别为1565.32和2907.47g m-2。各时期玉足海参粪便有机质、叶绿素a和脱镁叶绿素含量均高于同期食物，这表明玉足海参对沉积物有明显的选择摄食作用。根据各海域玉足海参的生物量，结合其对营养物质的排泄速率，可以计算东家湾海域玉足海参对海底C，P和N再生的贡献为138.98，0.33和9.26 μM m-2d-1，而桔钓沙海域则为219.21，0.52和14.58 μM m-2d-1。总体来说，玉足海参在海底营养循环中扮演着重要的角色。研究结果可为亚热带海洋环境保护及海参资源的合理开发与利用提供科学依据。