海洋生态与环境科学重点实验室知识库

受人类活动与气候变化双重压力影响，近年来世界范围胶质类浮游动物灾害频发，对生态系统、渔业生产、旅游业、沿岸工业等造成威胁，胶质类浮游动物的成灾原因研究及其防控处置是迫在眉睫的研究课题，开展胶质类灾害浮游生物的捕食者/竞争者及其捕食活动研究有望为胶质类灾害生物防控与资源的合理利用提供科学依据。现有胶质类浮游动物捕食者的研究已为胶质类灾害生物防控提供了较好的理论基础，但是目前亟需对某些天敌生物的捕食率进行定量研究。基于此，本研究在实验室条件下测定了海月水母Aurelia coerulea的干重、C含量、N含量、脂肪酸等生化特征，对潮间带及浅海常见生物、市面常见经济生物以及增殖放流生物进行了水母天敌生物的筛选，筛选出了几种对海月水母捕食较强的捕食者，并测定了捕食率，探索了胶质类生物作为活体饵料的可能性。主要结果如下：

对海月水母的生化特征研究表明，实验室内卤虫喂养条件下海月水母的伞径-湿重关系式为：W(g)=0.0809BD^2.8159（n=166，r²=0.9626），不同阶段海月水母的含水率稳定（>95%）；海月水母的C含量、N含量随伞径的增加而下降。各脂肪酸含量随伞径的增加而减少，C18:1在不同伞径水母体中的占比均最高。从水螅体到水母体阶段只投喂卤虫可能无法满足海月水母正常的能量需求，由此造成海月水母实验室内群体与野生群体的生化特征存在差异。

对潮间带及浅海常见生物、市面常见经济生物和增殖放流生物中海月水母天敌生物筛选发现，16种被筛选生物中紫贻贝、四齿矶蟹、绿侧花海葵、海燕、黑鲷、真鲷6种生物具有捕食特定阶段海月水母的能力。

黑鲷Acanthopagrus schlegelii对海月水母各发育期的捕食情况不尽相同，黑鲷无法直接捕食附着在波纹板上的水螅体；黑鲷可捕食海月水母的碟状体及幼水母体，黑鲷对碟状体的捕食是吞食性的，捕食率最大可达到15.487±1.150 ind·g^-1·d^-1；黑鲷对小伞径水母体的捕食也是吞食性的，对较大伞径水母体的捕食是蚕食性的，捕食能力受自身体长大小和水母伞径大小的双重影响，随着黑鲷体长的增加，它捕食更大伞径水母体的能力越强；黑鲷对水母体的捕食能力存在阈值，增大水母密度，不会导致黑鲷捕食量的增加，高密度下黑鲷更倾向于捕食水母体口腕部分，留下伞部；黑鲷对碟状体及10 mm幼水母体捕食能力最强。

真鲷Pagrus major对海月水母碟状体、幼水母体具有捕食能力，但无法直接捕食附着在波纹板上的水螅体；真鲷对碟状体的捕食是吞食性的，捕食率可达1.494±0.164 ind·g^-1·d^-1，不同体长的真鲷对碟状体的捕食率存在显著差异；真鲷对海月水母水母体的捕食能力较强，体长9 cm和11 cm的真鲷均能捕食伞径≤90 mm的海月水母；与黑鲷类似，真鲷对小伞径水母体的捕食是吞食性的，对较大伞径水母体的捕食是蚕食性的，这种捕食能力存在一个阈值，最大捕食量受体长的影响，当可利用水母量超过最大捕食量时，真鲷会优先捕食水母体的口腕，留下伞部；体长11 cm的真鲷对不同伞径水母体的捕食率较稳定，可能与自身营养需求有关。

紫贻贝Mytilus edulis具有滤食海月水母碟状体的能力。在13℃时，碟状体初始浓度50 ind·L^-1条件下一个壳长4 cm或6 cm的紫贻贝可以滤食17只2 mm直径的碟状体；4 cm、6 cm紫贻贝无法滤食直径4 mm的碟状体；实验室条件下紫贻贝过滤效率已达峰值，实际滤食效率需进一步原位实验确定。紫贻贝等固着性底栖滤食生物可能对海月水母碟状体高死亡率发挥重要作用。

以海月水母喂食黑鲷为例，探索了海月水母作为活体饵料的可能性，实验表明，仅投喂海月水母情况下黑鲷体重出现负增长，以海月水母作为单一饵料无法满足黑鲷正常的生长需求，但能提高黑鲷的C含量与N含量，而人工饵料与海月水母配合投喂可以一定程度上提高黑鲷的生长速度。以水母作为活体饵料，可以提高黑鲷的C18:2ω6、DHA、HUFA脂肪酸水平。

本文研究结果丰富了海月水母的捕食者清单，一定程度上证实“胶质类生物—水母”并非能量传递的“死胡同”，为海月水母的生物防控的可能性奠定了理论基础，为实现水母灾害可能的高值化利用提供了理论支撑。

Massive and recurrent outbreaks of gelatinous zooplankton communities occurred in several coastal waters worldwide in recent years, which may relate to global climate change and human activity. The outbreaks of gelatinous zooplankton may negatively impact ecosystems, fisheries, tourism and coastal industries. Therefore, it is urgent to develop technologies for control and disposal. The predator / competitor research of gelatinous zooplankton is expected to realize the prevention and control of bloom and the rational utilization of resources. Based on this, we explored the biochemical characteristics(such as dry weight, total C, total N and fatty acid) of moon jellyfish Aurelia coerulea and sought their predators, quantified their ingestion rate and explored the possibility of using gelatinous zooplankton as bait. Results revealed that:

Biochemical characterization of moon jellyfish showed that: the relationship between wet weight（W） and bell diameter（BD） was W=0.0809BD^2.8159, moisture content during different stage were constant（>95%）, the C/N content and fatty acid decreased with increasing bell diameter and C18:1 was the highest in fatty acid. There were many differences between in-lab and wild individuals, feeding artemia all the way from polyp to medusae may not meet the normal energy requirements of moon jellyfish.

To find the predators of A. coerulea, we collected economic organisms, intertidal organisms and stocking organisms. Results revealed that: Mytilus edulis, Pugettia auadridens, Anthopleura fuscoviridis Carlgren, 1949, Asterina pectinifera, Acanthopagrus schlegelii and Pagrus major could predate on moon jellyfish, gelatinous zooplankton were not trophic dead ends.

Black sea bream could not prey on polyps attached to the corrugated plate; the maximum ingestion rate of black sea bream on ephyrae was attained at 15℃ and the highest ingestion rate was 15.487±1.150 ind·g^-1·d^-1; total length of black sea bream and bell diameter of jellyfish affected the ingestion rate. With the increase of black sea bream, it can prey on larger jellyfish individual. There is a threshold of predation ability of black sea bream on jellyfish with given umbrella diameter, giving more jellyfish will not increase the predation amount. Black sea bream Sparus macrocephalus preferred to eat the oral of jellyfish. The results provide a new possibility for understanding the high mortality rate of ephyrae, and provide a theoretical basis for understanding the disappearance of gelatinous zooplankton.

Red sea bream had the ability to prey on ephyrae and larvae medusea, but they could not prey on polyps attached to the corrugated plate. The maximum ingestion rate of red sea bream on ephyrae was 1.494±0.1644 ind·g^-1·d^-1, and there was a significant difference in the ingestion rate between different total body length. A fish which total length were 9/11 cm could prey on medusae whose diameter was 90 mm, so the ability of red sea bream prey on medusae was powerful. Similar to black sea bream, there is also a threshold of predation ability with given umbrella diameter, giving more jellyfish will not increase the predation amount, red sea bream might eat all the oral of jellyfish when the jellyfish were excessive. The predation rate of 11cm red sea bream on jellyfish with different diameter was constant, which might be related to their nutritional requirements.

Based on a review of the literature, we quantified the filtration rate of mussel Mytilus edulis on ephyrae. A mussel (shell length, 4 or 6 cm) could consume 17 discs at an initial concentration of 50 ind·l^-1 at 13℃, but they could not consume discs lager than 4mm. The filtration rate was affected by prey concentration, temperature, size of individual, etc. Therefore, further investigation may focus on the actual filtration rate in situ.

The possibility of using gelatinous zooplankton as live bait was explored with black sea bream and moon jellyfish. Using jellyfish alone as bait could not meet the normal growth demand of black sea bream, but could improve the C, N content of black sea bream, and the growth rate of fish with both artificial diet and moon jellyfish was improved. Using jellyfish as live bait can improve the fatty acid content of C18:2ω6, DHA and HUFA of black sea bream.

The results provide a theoretical basis for the biological prevention and control of gelatinous zooplankton bloom, a new explanatory basis for understanding the mortality of moon jellyfish, and a possibility for high-value utilization of gelatinous zooplankton bloom.