海洋生态与环境科学重点实验室知识库

   绿潮是某些海洋大型绿藻类植物，在特定环境条件下，呈现爆发性增殖的一种异常生态现象，而这些能引发绿潮的植物通常被称为绿潮藻类。绿潮通常发生在富营养化程度较高的澙湖、河口、内湾及人类活动影响严重的海岸地区，常多年连续爆发。随着沿岸海域富营养化的加剧，近年来，绿潮频繁爆发，对近岸水域生态环境及其经济物种的影响日益明显。自2008年以来，黄海浒苔Entermorpha绿潮严重威胁着山东半岛南岸海域的生态环境。与此同时，硬毛藻Chaetomorpha绿潮经常在某些重要近岸海域爆发。以上两种绿潮藻腐败降解会导致缺氧、水质恶化、有毒物质急剧增多，从而对重要经济物种，如刺参、鲍鱼等，造成严重损害。

   本研究以青岛崂山湾的浒苔Entermorphapp prolifera与威海天鹅湖的线性硬毛藻Chaetomorpha linum为对象，调查分析了这两种绿潮藻类对典型海域底栖动物生存环境、沉积物营养供给能力、有毒硫化物含量及危害作用的影响。底栖动物生存环境质量以小型底栖动物群落特征来指示。沉积物营养供给能力由其有机质总量与组成指标综合评价。与此同时，分析了沉积物中硫化物与小型底栖动物指标的相关性，以评估绿潮藻类导致沉积物硫化物增多的危害。本研究还以线性硬毛藻与其它饲料原料喂养仿刺参Apostichopus japonicus，测定了其摄食、生长及能量收支情况；同时使用碳稳定同位素分析，研究了仿刺参对不同饲料原料中有机质的摄食偏好性，从而综合评价了线性硬毛藻对仿刺参饵料价值。本研究有助于增进绿潮藻类影响的认知，并建立其对典型海域底栖环境影响的评价体系，为典型海域的科学管理提供相关技术支持。另外，通过线性硬毛藻对仿刺参饵料价值的评价，为其资源化利用提供了新的思路。主要研究结果如下:

1 绿潮藻类对典型海域底栖动物生存环境影响

   浒苔与线性硬毛藻能分别对崂山湾和天鹅湖的底栖动物生存环境产生影响，且既可能为正效作用，也可能为负效作用，这可能由绿潮藻类爆发量所决定。在崂山湾，叶绿素降解产物脱镁叶绿酸含量在2016年9月浒苔沉降后期显著高于2017年9月浒苔未沉降的对照期（p < 0.001），故用于在本研究中指示浒苔沉降量。在2016年9月浒苔沉降后，崂山湾小型底栖动物群落特征与沉积物脱镁叶绿酸含量的回归分析结果表明，浒苔沉降量的升高能使近岸的砂质底区小型底栖动物物种多样性显著升高（香农-维纳指数：R² = 0.83；辛普森指数：R² = 0.94）。以上结果表明，崂山湾在2016年9月时，浒苔的沉降对底栖动物生存环境起改善作用，这可能是由于其增加了典型海域沉积物的营养供给能力。在天鹅湖，夏季线性硬毛藻绿潮爆发时，受影响的海草分布区小型底栖动物总丰度与物种多样性显著降低，而线虫/桡足类丰度比显著升高（p <  0.05），表明线性硬毛藻覆盖海草区会使其底栖动物生存环境恶化；同时，夏季线性硬毛藻爆发对无海草裸露空地的底栖动物生存质量无显著影响（p ^>  0.05）。本研究发现在冬季时，天鹅湖线性硬毛藻影响依然持续，但此时曾有过线性硬毛藻覆盖的区域底栖动物生存环境质量指标优于未受影响区（p <  0.05）。以上的研究结果表明，在天鹅湖，夏季时线性硬毛藻的覆盖不利于底栖动物生存，而其影响持续到冬季时反而使底栖动物生存环境质量有所提高。本研究也初步证实小型底栖动物群落指标可有效指示绿潮藻类对典型海域底栖环境的总体影响。

2 绿潮藻类对典型海域表层沉积物营养供给能力的影响

   浒苔与线性硬毛藻能分别对崂山湾和天鹅湖表层沉积物营养供给能力产生影响。在崂山湾，浒苔对表层沉积物营养供给能力的影响主要表现为对其有机质组成影响。崂山湾砂质底区的表层沉积物总有机质含量在浒苔沉降后期与对照期均没有显著性差异；而在泥质底区，对照期表层沉积物的总有机质含量甚至高于浒苔沉降后期（p <  0.05）。此结果说明，调查期的表层沉积物有机质存量不能有效反应浒苔沉降引发的有机质输入量变化。而在浒苔沉降后期，两种底质区表层沉积物蛋白质含量均显著高于对照期（p <  0.05）。以上结果说明浒苔的沉降显著提高了崂山湾表层沉积物的营养质量，并因此提高了其营养供给能力。天鹅湖在夏季时，线性硬毛藻的爆发区与非爆发区表层沉积物中的总有机质含量没有显著性差异，而在冬季时曾有线性硬毛藻爆发区域的沉积物总有机质含量显著高于未曾受影响区（p <  0.05）。在夏季时，线性硬毛藻爆发使海草区沉积物营养性组分含量降低，而使无海草区升高；而在冬季，线性硬毛藻残留影响作用能使受影响区表层沉积物营养性组分含量显著高于未受影响区（p <  0.05）。这一结果说明线性硬毛藻的沉降显著影响了天鹅湖表层沉积物的营养质量。本研究表明，绿潮藻类对典型海域沉积物有机质总量与组成可能都有影响，但蛋白质等营养性组分的含量对其影响的反应更敏感。

3 绿潮藻类对典型海域表层沉积物硫化物及其危害作用的影响

   浒苔与线性硬毛藻的沉降都会导致典型海域表层沉积物中硫化物含量的升高，然而硫化物的增多对两个典型海域底栖动物生存环境的影响有所不同。在崂山湾，浒苔沉降后的2016年9月，不同底质区的表层沉积物硫化物含量显著高于2017年9月对照期（p <  0.05）。浒苔沉降后期的表层沉积物硫化物含量与指示浒苔沉降量的脱镁叶绿酸含量呈明显正相关关系（砂质底区：R² = 0.68；泥质底区：R² = 0.91），说明浒苔沉降能够引发崂山湾沉积物硫化物含量的升高。与此同时，砂质底区小型底栖动物总丰度、物种多样性等指数也与表层沉积物硫化物含量存在正相关关系（总丰度：R² = 0.92；香农-维纳指数：R² = 0.97），说明此时浒苔引发硫化物增多的负面作用较轻，不足以改变崂山湾底栖动物的生存环境总体质量。在天鹅湖，受线性硬毛藻爆发影响的区域表层沉积物硫化物含量总体上高于未受影响的区域（p <  0.05）。然而，天鹅湖夏季时表层沉积物硫化物含量与底栖小型底栖动物总丰度呈负相关关系（R² = 0.66），说明线性硬毛藻的负面作用在此时较重，足以降低底栖动物生存环境的总体质量；冬季时表层沉积物硫化物含量与小型底栖动物群落物种多样性呈正相关关系（R² = 0.52），说明此时线性硬毛藻的负面作用已经较轻，不足以改变底栖动物生存环境的总体质量。

4 线性硬毛藻对仿刺参饵料价值研究

   线性硬毛藻是仿刺参的良好饵料，其对仿刺参的饵料价值高于鳗草Zostera marina，可以替代鼠尾藻Sargassum thunbergii作为仿刺参饲料中的主要成分。室内养殖实验结果表明，以线性硬毛藻为主要饲料的处理组中的仿刺参，特定生长率、食物转化效率与表观消化率显著高于以鳗草为主要饲料的处理组（p <  0.05），且与以优质饲料鼠尾藻为食的仿刺参无显著差异。仿刺参能量收支的结果表明，相比与鼠尾藻与鳗草饲料，线性硬毛藻饲料可以使食物中更高比例的能量用于生长（p <  0.05）。本研究还基于稳定同位素分析建立了饲料原料的一个新指标——碳贡献/碳组成（R_{C_con/C_com}），并证明它可以有效地指示仿刺参对不同饲料原料中有机质的摄食偏好性。根据这项指标的统计结果，仿刺参对线性硬毛藻有机质的摄食偏好性显著高于鳗草（p <  0.05）；同时，海泥虽然因有机质含量远低于以上植物型原料，不能成为主要有机质来源，但仿刺参对其有机质的摄食偏好性显著高于线性硬毛藻等植物型原料。

  The green tide is an abnormal ecological phenomenon caused by the blooming proliferation of several green macroalgae in specific environmental conditions. Green macroalgae which could cause green tide are normally called the green tide macroalgae. The green tides usually happened in lagoons, estuaries, inner-bays, and coastal areas heavily influenced by human beings and eutrophication in consecutive years. With the increasingly serious eutrophication in offshore areas, the green tides had more and more influences on coatal ecosystems and its economical species in recent years. From the year of 2008, Entermorpha green tides of the Yellow Sea has seriously affect the coastal ecosystems along the south shore of Shandong Peninsula. In recent years, Chaetomorpha green tides occurred in many coastal areas of China, including several important coastal. The corruption process will lead to hypoxia, water quality deterioration, and increase of toxic substances, which could seriously harm significant ecological species, such as sea cucumbers and abalones.

  This research focused on the Entermorpha prolifera green tide in Laoshan Bay of Qingdao, and C. linum green tide of the Swan Lake of Weihai. The influences of these green tide macroalgae on the zoobenthos living environment, sediment nutrition supply capacity, toxic sulfide content of sediment and its harm were investigated and evaluated. The meiofauna community features were used to indicate the zoobenthos living environment quality. The quantity and composition features of organic matters in sediment were adopted to indicated its nutrition supply capacity., In order to evaluate the harmful effect of sulfide increase, the relevance of sulfide contents and corresponding meiofauna features in sediment were analyzed. In addition, C. linum was made to fodders and provided to Apostichopus japonicus with other ingredients. The feeding, growth, and energy budget performances of A. japonicus were tested. Meanwhile, the carbon stable isotope analysis were used to evaluate the feeding preferences of A. japonicus to organic matters in different fodder ingredients. By those two approaches, the food value of C. linum to A. japonicus was estimated. This research will be beneficial to improving our understanding to the influences of green tides, and the scientific management to marine ranching by building the benthic environment assessing technology system. Additionally, this research also provided a new approach for the resource utilization of C. linum by assessing its food value to A. japonicus. The main results are:

1 The influence of green tide macroalgae on the zoobenthos living environment

  Entermorpha and C. linum could influence the zoobenthos living environment of Laoshan Bay and Swan Lake, respectively. Depending on the blooming amount of green tide macroalgae, this influence could be either positive or negative. In the sandy bottom area of Laoshan Bay, after sinking of Entermorpha, the meiofauna species diversity increased with the rise of sinking amounts by regression analysis (Shannon-Wiener index: R² = 0.83; Simpson index: R² = 0.94). The above result suggested that Entermorpha sinking could improve the zoobenthos living environment of Laoshan Bay, which might be caused by the increase of sediment nutrition. In the Swan Lake, when C. linum bloomed in summer, the meiofauna abundance and species diversity significantly declined in the seagrass meadows affected by C. linum, and the ratio of benthic nematodes and copepods abundance significantly increased (p^> 0.05), which indicated the zoobenthos living environment be deteriorated in this time. The influence of C. linum could continue to winter although most C. linum and seagrass had disappeared. However, the zoobenthos living environment quality of areas affected by C. linum was better than that unaffected (p ^>  0.05). The results above indicated that influence of C. linum in Swan Lake was negative in the summer, but turned to positive in winter.

2 The influence of green tide macroalgae on the sediment nutrition supply capacity

  Entermorpha and C. linum could influence the sediment nutrition supply capacity of Laoshan Bay and Swan Lake, respectively. In the Laoshan Bay, the influence of Entermorpha on sediment nutrition supply capacity mainly reflected in terms of its organic matters composition. There were no significant differences between the total organic matters of Entermorpha sinking period (September in 2016) and comparative period (September in 2017). The result above suggested that the sediment organic matters content couldn’t reflected the organic matters input by Entermorpha sinking in September of 2016. However, in both the sandy and muddy bottom areas, the sediment protein contents of Entermorpha sinking period were significantly higher than that of comparative period (p <  0.05). That result suggested that Entermorpha sinking improved the sediment nutrition supply capacity mainly in terms of raise its nutritive components contents. In the summer of Swan Lake, there were no significant differences between the sediment total organic matters of C. linum affecting areas and others, but in the winter, the sediment total organic matters of areas affected by C. linum were significantly higher than that of areas unaffected (p <  0.05). In the summer, the cover of C. linum reduced the nutritive components contents of sediment in seagrass areas, but increased that in non-seagrass aeras (p <  0.05). In the winter, the sediment nutritive components contents of areas affected by C. linum were significantly higher than that of areas unaffected (p <  0.05). Those results above indicated that C. linum sinking significantly influenced the sediment nutrition quality of Swan Lake. This research also suggested that the influence of green tide macroalgae sediment nutrition supply capacity might reflected both in terms of organic matters amount and composition, but the contents of nutritive components, such as protein and carbohydrate, could reflected the influence of green tide macroalgae more sensitively.

3 The influence of green tide macroalgae on the sediment sulfide content and its harm

  Both Entermorpha and C. linum sinking could lead to the increase of sediment sulfide contents, but the influences of the more sulfide effect on the zoobenthos living environment were different. In the Laoshan Bay, the sediment sulfide content in Entermorpha sinking period was significantly higher than that of comparative period (p <  0.05), and there was the positive correlation between the sediment sulfide contents and Entermorpha sinking amounts (sandy bottom area: R² = 0.68; muddy bottom area: R² = 0.91). Meanwhile, the meiofauna abundance and species diversity were both positive relevant with sediment sulfide contents (abundance: R² = 0.92; Shannon-Wiener index: R² = 0.97), which indicated that the negative influence of sulfide was relative light and had less effect on the zoobenthos living environment. In the Swan Lake, the sediment sulfide contents in C. linum sinking areas were significantly higher than that unaffected (p < 0.05). Meanwhile, in the summer of Swan Lake, there was a negative correlation between the sediment sulfide content and the meiofauna abundance (R² = 0.66), which suggested the relative heavy negative influence of sulfide on the zoobenthos living environment. However, in the winter, there was a positive correlation between the sediment sulfide content and the meiofauna species diversity in Swan Lake (R² = 0.52), which indicated the relative light negative influence of sulfide.

4 The food value of Chaetomorpha linum for Apostichopus japonicus

  C. linum is a good diet ingredient for A. japonicus. The results of indoor culture experiment showed that the specific growth rate, food conversion efficiency, and apparent digestive ratio of A. japonicus fed on C. linum wasn’t significantly different from those fed on traditional diet ingredient Sargassum thunbergii of high nutrition quality. Meanwhile, compared with S. thunbergii more proportion of energy in C. linum was utilized by for growth (p <  0.05). A new food ingredient index, the ratio of carbon contribution to carbon composition (R_{C_con/C_com}) were constructed on the basis of carbon stable isotope analysis, which was proven to be effective to reflect the feeding preference of A. japonicus to organic matters of different diet ingredients. Although muddy sediment couldn’t be a main organic matter source for A. japonicus as its lower organic matter content, the organic matter feeding preference of A. japonicus to muddy sediment was significantly higher than that to other plant ingredients, such as C. linum.