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獐子岛海域贝类养殖与营养盐限制的关系研究
梁艺
Subtype博士
Thesis Advisor张光涛
2019-05-16
Degree Grantor中国科学院大学
Place of Conferral中国科学院海洋研究所
Degree Name理学博士
Keyword獐子岛海域 虾夷扇贝 底播养殖 营养盐限制 浮游植物群落
Abstract

  养殖贝类可以通过滤食、代谢和生物沉积等作用影响海洋生态系统的物质循环过程,但是在不同的生态系统中观察到的生态效应却各不相同。乐观的观点认为贝类养殖可以作为富营养化修复的手段,悲观的则认为可以导致缺氧等负面生态效应。这种显性生态效应的变异性除了与养殖规模有关,还受海域的自然条件影响。本论文选择在我国典型的离岸贝类养殖海区—獐子岛海域,通过现场调查研究虾夷扇贝(Patinopecten yessoensis)底播养殖的生态效应。海域规律性的物理环境特征和较小的陆源影响有利于从复杂的环境背景过程中识别出贝类养殖的具体影响。

    本论文借助20097月至20106月对獐子岛海域进行周年逐月调查,在比较养殖海区和非养殖海区营养盐、叶绿素含量和浮游植物粒级组成的基础上,识别出贝类养殖的下行控制作用并提出春季硅酸盐限制是最重要的影响;通过2014年春季航次调查,分析了春季限制性营养盐种类和程度的变化,以及对浮游植物群落结构的影响;进一步地,通过研究春季营养盐、生物硅、叶绿素等生源要素的迁移转化特征来分析春季硅酸盐限制发生的原因。引入Unisense微电极的新方法,在2016年春夏季比较不同养殖海域、不同季节沉积物理化性质的变化,以揭示不同养殖海区沉积速率的差异,及其受到环境因子的影响。主要结果如下:

    贝类养殖的下行控制作用会增加无机氮和磷酸盐的消耗,并在外源输入较少的春季,加剧营养盐尤其是硅酸盐限制。根据2009年至2010年的周年调查结果,研究海域在6–10月份水体出现强烈的垂直分层现象,而在冬季温跃层消失,水体混合均匀;盐度的明显降低发生在6–8月份的上层水体中。得益于淡水输入以及温跃层消失过程中的补充作用,水柱平均营养盐浓度在7–12月呈现增加趋势。20102月至3月期间,伴随着叶绿素浓度的增加,营养盐浓度骤降,并在整个春季出现营养盐的净消耗。3月养殖海区的硅酸盐浓度在所有站位均降至浮游植物吸收最小阈值2 µM以下,而在非养殖海区硅酸盐限制最早出现于4月份。养殖海区的无机氮和磷酸盐浓度在全年均低于非养殖海区(P < 0.01)。上述研究结果表明,贝类养殖可以通过下行控制作用降低营养盐的浓度,这种作用在没有外源输入补充时尤为明显,具体表现为导致了硅酸盐限制,进而引起浮游植物群落结构的改变。

    伴随着春季硅酸盐限制,浮游植物群落优势种由硅藻向甲藻转变。研究结果表明,獐子岛春季无机氮浓度一直处于较高水平,3月平均值高达5.74 µM,且随时间变化较小。而磷酸盐和硅酸盐浓度低于浮游植物最低吸收阈值存在于整个春季以及各层水体样品中(磷酸盐浓度除了五月底层水体外)。3月,硅酸盐限制发生频率高达71.2%,水柱平均硅酸盐浓度低至1.7 µM3月至5月,上层水体磷酸盐浓度由0.12 µM降至0.05 µM4月和577.3-90%的站位出现了磷酸盐限制。相应地,浮游植物丰度在春季急剧下降,从3月的7.16×104降至5月的1.70×104 cells L-1;浮游植物粒级组成的占比优势由小型浮游植物逐渐转变为微型浮游植物,群落优势种由硅藻向甲藻转变。从浮游植物种类鉴定结果可知,甲藻优势度和优势种群增加,而硅藻优势种群由3月的具槽帕拉藻变为5月的格氏圆筛藻。结果表明,硅甲藻优势地位的转变是由硅酸盐限制引起的,而磷酸盐缺乏进一步促进了优势种群由硅藻向甲藻转变。浮游植物群落结构的改变是由营养盐的上行控制决定的,而不是贝类选择性滤食(下行控制)的结果。

    进一步分析发现,春季硅酸盐限制的出现主要归因于浮游植物光合作用对硅酸盐的消耗和本地再生补充的不足。春季昼夜连续观测结果显示,硅酸盐浓度呈现出白天低夜间高的特征,而无机氮和磷酸盐昼夜浓度基本稳定。水体中颗粒态生物硅含量滞后于溶解态硅酸盐,在4月份出现极低值,且底层富集特征不显著。从表层沉积物来看,獐子岛沉积物类型为粉砂质砂,有机质含量仅略高于粉砂质砂和砂质粉砂的莱州湾。与同样是底播养殖的胶州湾相比,獐子岛海域发生底层缺氧的风险更低,但是营养盐限制的可能性更高。结果表明,在獐子岛海域生物沉积物的矿化对水体硅酸盐的补充不能抵消浮游植物的消耗,这是由于贝类养殖并未显著加强生物硅向海底的沉积。

    本论文研究结果表明,即便在相同的养殖规模下,贝类养殖的生态效应也因季节而异。夏、秋季贝类养殖可以消耗水体中过剩的无机氮和磷酸盐,而且不产生明显的负面生态效应;春季则会引发或者加剧硅酸盐限制,导致本论文中观测到的硅/甲藻优势地位的转换。无论是单纯的贝类养殖还是利用贝类养殖缓解水体富营养化,硅酸盐限制和硅/甲藻转换的发生都是一个养殖规模确定的理想指标。基于这种春季“瓶颈期”的初级生产力和浮游植物供饵力水平,可以有效避免对海区生物承载力的高估,实现养殖活动和生态环境的和谐发展。

Other Abstract

  As mariculture expands offshore in response to the increasing demand for seafood, a new set of ecological concerns arises. While bivalve farming is well recognized modifying biogeochemical cycle in water column through filter-feeding and biodeposition, its impacts on nutrient concentrations in various ecosystems may vary from depletion to addition. Located in northern Yellow Sea, waters around the Zhangzi Island (50 km offshore) is a typical offshore shellfish farming area in China, where bottom-seeding aquaculture of Japanese scallops Patinopecten yessoensis has been performed since 1998. As natural variability in this area has been well documented, it was selected as an ideal place to investigate the ecological consequences of shellfish farming.

  Annual variations of nutrients, Chlorophyll-a (Chl-a) and size-fractionated Chl-a concentrations were investigated from July 2009 to June 2010, and compared between mariculture area and open waters, in order to distinguish the effects of scallop farming from influences of natural variabilities. Furthermore, in order to figure out the causes of silicate limitation in spring, the temporal and spatial distribution of nutrients, biogenic silica, Chl-a concentrations as well as physical conditions were investigated in this area from March to May in 2014. We analyzed the occurrence frequency of nutrients limitation and the way in which it regulates the phytoplankton community structure. Additionally, a new method of Danish Unisense microelectrode was applied in our study to determine the physicochemical properties of sediments in the Laizhou Bay, the Muping area, the Jiaozhou Bay and the Zhangzi Island area, so as to explore the correlation between biodeposition and shellfish farming in water columns.

  According to the annual survey in the Zhangzi Island area, strong vertical stratification was observed from June to October and disappeared in winter with vertical homogeneity. Significant decrease of salinity was observed in the upper layers from June to August. Nutrient concentrations in monthly average showed similar trends in mariculture area and open waters, increasing continuously from July to December. This can be attributed to the coefficient supplement by freshwater discharge of the Yalu River and the collapse of the YSCWM. From February to March, nutrient concentrations decreased dramatically and net consumption occurred overwhelmingly in spring. Correspondingly, increase in Chl-a concentration was recorded in March. Silicate concentration lower than the minimum threshold for phytoplankton growth occurred in March in all stations in mariculture area, while in open waters silicate limitation was recorded firstly in April in upper layers. Dissolved inorganic nitrogen (DIN) and phosphate concentrations were significantly lower in mariculture area compared to those in open waters all through the year (P < 0.01). Silicate concentration, however, was higher in mariculture area in summertime (July to September) and lower during November-June (P < 0.05). According to our results, shellfish farming can work as nutrient sink through top-down control on nutrient concentration and structure. Nutrients removal was extremely significant in spring when exogenous supplement is scarce, leading to silicate limitation and shift in size-fractionized phytoplankton community structure.

  Along with silicate limitation, dominance shift from diatoms to dinoflagellates was recorded in phytoplankton community. The monthly averaged DIN concentration was comparatively high, with the maximum of 5.74 µM in March and slight change during the sampling period. Phosphate and silicate deficiencies were recorded in spring in all layers (except the bottom layer in May for phosphate). Silicate limitation presented at up to 71.2% of stations, with the average concentration as low as 1.7 µM in March. Meanwhile, phosphate concentration decreased from 0.12 to 0.05 µM in the upper layers from March to May. Stoichiometric ratios and absolute concentrations indicate that 77.3-90% of stations showed phosphate limitation in April and May. Accordingly, phytoplankton abundance decreased sharply in spring, from 7.16×104 cells L-1 in March to 1.70×104 in May. The dominant species in phytoplankton community changed from diatoms to dinoflagellates. On species level, both increased dominance of dinoflagellate and shift in dominant diatom species were observed. The dominant diatom species changed from Paralia sulcate in March to Coscinodiscus granii in May. It suggested that diatom/dinoflagellate shift in dominance was triggered by silicate limitation and further promoted by phosphate deficiency. The dominance shift was proposed to be determined by bottom-up control of nutrient concentrations rather than selective feeding of scallop (top-down).

  Specifically, the silicate limitation in spring was attributed to net consumption of photosynthesis and defficiency in local re-mineralization. During continuous observation in spring, silicate concentration in water column was significantly higher in nighttime than daytime, whereas that of DIN and phosphate showed no diel difference. Comparing to dissolved silicate, biogenic silica concentration was lowest in April (one month later), and bottom enrichment was not evident. The sediment type in the Zhangzi Island area is silty sand, and the organic matter content was slightly higher than that in the Laizhou Bay, where the sediment type is a mix of silty sand and sandy silt. Compared with the Jiaozhou Bay, another bottom seeding shellfish farming area, the probability of hypoxic conditions is lower in the Zhangzi Island area, but that of nutrient limitation is higher.

  It is thus concluded that, even in the same shellfish farming area, the observed ecological consequences may vary with seasons. In summer and autumn, the farmed shellfish population helped in removal of extra DIN and phosphate, without any significant negative impacts on nutrient structure and phytoplankton community, whereas in spring it resulted in silicate limitation and in turn diatom/dinoflagellate shifted. On future perspective, presence of silicate limitation can be used as an index of over cultivation in shellfish farming for both seafood production and eutrophication mitigation. On the other hand, the “bottle-neck” effect of nutrient limitation on food availability in spring suggests that carrying capacity might be originally overestimated, when calculated from averaged annual primary production.

Subject Area海洋科学
MOST Discipline Catalogue理学::海洋科学
Table of Contents

1 绪论... 1

1.1 我国贝类养殖发展概况... 1

1.2 贝类养殖和环境相互作用的机制和途径... 3

1.3 贝类养殖生态效应的区域变异性和原因分析... 6

1.4研究思路和目标... 9

2 獐子岛营养盐外源输入和养殖贝类的下行控制作用... 11

2.1 材料与方法... 12

2.1.1 采样时间与站位布设... 12

2.1.2 样品采集与测定分析... 13

2.1.3 数据分析... 14

2.2 结果... 15

2.2.1 温度和盐度的周年变化... 15

2.2.2 营养盐周年变化及营养盐限制... 16

2.2.3 叶绿素浓度和粒级结构的周年变化... 19

2.3 讨论... 22

2.3.1 外源营养盐补充... 22

2.3.2 贝类养殖对营养盐的下行控制作用... 24

2.4小结... 26

3 春季硅酸盐限制和硅甲藻转换:下行还是上行控制... 27

3.1 材料与方法... 28

3.1.1 研究海域与站位布设... 28

3.1.2 样品采集与测定... 29

3.1.3 数据分析... 30

3.2结果... 30

3.2.1 春季温度和盐度的时空分布... 30

3.2.2 春季营养盐限制随时间变化... 31

3.2.3 春季浮游植物群落随时间变化... 35

3.3 讨论... 39

3.3.1 贝类养殖加剧养殖海区的营养盐限制... 39

3.3.2硅甲藻优势地位转变的上行控制... 41

3.4 小结... 42

4 从硅酸盐和生物硅分布看春季硅酸盐限制的成因... 45

4.1 材料与方法... 46

4.1.1 研究海域与站位布设... 46

4.1.2 样品采集与现场调查... 46

4.1.3 实验室测定分析... 47

4.1.4 数据分析... 47

4.2 结果... 48

4.2.1 溶解性硅酸盐的时空分布特征... 48

4.2.2 生物硅的时空分布特征... 50

4.2.3 溶解性营养盐昼夜连续变化特征... 51

4.3 讨论... 52

4.3.1 光合作用对硅酸盐的净吸收... 52

4.3.2 生物硅对硅酸盐循环的作用... 53

4.4 小结... 54

5 不同贝类养殖海区的沉积物特征比较... 55

5.1 材料与方法... 56

5.1.1 研究海域与站位布设... 56

5.1.2 样品的采集与预处理... 59

5.1.3 样品的测定分析... 59

5.1.4 数据分析... 60

5.2结果... 60

5.2.1 不同养殖海区表层沉积物理化性质... 60

5.2.2 不同养殖海区沉积物溶解氧随时间的变化... 63

5.2.3 不同季节表层沉积物溶解氧含量的差异... 65

5.3 讨论... 68

5.3.1 不同养殖海区生物沉积速率的比较... 68

5.3.2 近岸养殖海区生物沉积强度高于离岸海域... 68

5.3.3 海区沉积物溶解氧的季节差异... 69

5.3.4 沉积物理化性质测定的新方法... 70

5.4 小结... 71

6 獐子岛营养盐限制对贝类生物滤器和生物承载力评估的启示 73

6.1贝类养殖去除营养盐的效果和限制条件... 75

6.1.1 贝类养殖缓解富营养化的有效性... 75

6.1.2 “贝类生物滤器的应用条件... 78

6.2 营养盐限制对生物承载力评估的影响... 79

6.2.1 营养盐限制作为养殖规模超出生物承载力的指标... 79

6.2.2 营养盐限制对生物承载力评估的瓶颈效应. 80

7 结论与展望... 83

7.1 主要结论... 83

7.2 论文的创新点及展望... 85

参考文献... 87

... 101

作者简历及攻读学位期间发表的学术论文与研究成果... 103

 

Pages127
Language中文
Document Type学位论文
Identifierhttp://ir.qdio.ac.cn/handle/337002/156784
Collection胶州湾海洋生态系统国家野外研究站
Recommended Citation
GB/T 7714
梁艺. 獐子岛海域贝类养殖与营养盐限制的关系研究[D]. 中国科学院海洋研究所. 中国科学院大学,2019.
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