【作者】 刘学海；

【导师】 袁业立；

【作者基本信息】 中国海洋大学 ， 物理海洋， 2009， 博士

【摘要】 南黄海是我国重要的近海,研究其生态过程对了解我国近海生态动力控制机制有重要意义；桑沟湾是我国重要的养殖示范区,研究该湾对认识养殖海域的生态状况和科学养殖有重要意义。本文针对两个不同尺度的典型海域进行了生态动力学模型研究。对两个海域,均在建立能够良好地再现水动力过程的物理模型的基础上,选取关键的生态要素和必要的生物化学过程,通过合理地参数化,分别建立两海域的生态动力学模型,通过数值模拟研究两域的生态特征。南黄海的水动力学模型包括了较完整的物理过程(如潮汐、波浪混合、环流等),生态变量包括浮游植物、浮游动物、营养盐和有机碎屑。桑沟湾的水动力学模型考虑了养殖影响,生态要素除以上四个变量外还包括溶解有机物,考虑养殖贝类和大型藻对饵料和营养盐的消耗或释放,在生态模型的基础上根据物质供需平衡关系或营养动态关系分别建立了贝类、大型藻、鱼类的养殖容量模型。主要得到以下结果：对南黄海：1)浪致混合和潮流分别使上、下层水体的垂直扩散系数增加10-3～10-1m2/s,使近岸海域垂向混合更加均匀,深水域上、下混合层厚度加大,温跃层强度增加。考虑潮流,模拟冬季的黄海暖流及沿岸流、夏季的台湾暖流、中国沿岸流及南黄海中部环流均有所减弱,改变了夏季朝鲜沿岸流方向(使其呈逆时针),使南黄海中部海域无潮情况下的北向流改为向南弱流。2)春季初级生产能力最强,浮游植物水平最高,夏季次之,冬季最小。显著水华出现在4月中下旬。南黄海春季的浮游植物净流入一直为正且较大,有助于水华形成；夏季的净流入经常为负。浮游生长大部分海域主要受磷限制。3)西部近岸海域：4月中下旬至9月上旬浮游植物浓度较高,分层不明显。长江口附近海域：总体上是南黄海浮游植物生物量最高的海域,5月出现显著水华；浮游植物生长受光照限制,较强的混合影响浮游植物聚集；浮游植物浓度总体上呈由近岸向外先增后降的趋势。中部海域：4～11月份浮游植物分布存在分层现象,4月中下旬发生显著水华,5月份出现次表层最大化,且次表层深度逐渐增加,8、9月份该层顶部深至30m；10月份次表层最大化逐渐消失。东部陆坡海域：下层存在上升流,营养盐浓度较高；生态特征同中部海域相似。4)浪混合及潮流对生态特征起着重要的控制作用。浪混合对春季水华起着延迟和加强作用,不考虑浪混合将使水华提前13天,分析了模型添加浪混合的必要性。5)长江径流对南黄海浮游植物水平有一定提高,主要影响在长江口附近海域。对桑沟湾：Ⅰ.观测表明养殖活动明显降低了所在水层的流速。通过在模型中布置透水摩擦板实现了养殖对水动力影响的模拟,经数值实验给出基本合理的摩擦系数。不考虑养殖影响该湾的半交换周期为7d,仅考虑贝类养殖为12d,同时考虑贝类和海带养殖半交换周期达16d。湾内西北、西南部水交换能力最差。Ⅱ.该湾总体上冬季浮游植物生物量较小,夏季较大,2月出现弱峰,9月全年最大,该湾的浮游生态特征与贝类养殖有关。海带、牡蛎及扇贝养殖区均有以上浮游特征。贝类养殖区的营养盐在夏、秋季出现高值,与贝类的排泄有关。Ⅲ.扇贝养殖容量：冬、秋季较大,春、夏季较小,4月上中旬最小；以年平均计,该湾平均规格的扇贝的养殖容量为53 ind/m2,扇贝养殖区的总养殖容量为10.1亿粒,目前实际养殖密度不宜扩大。牡蛎养殖容量：冬季较大,夏季较小,8月下旬最小,2月中旬最大；理论养殖容量为76 ind/m2,养殖区养殖总容量在41.1～51.7亿粒范围内,建议保持39333粒/亩的规模。海带养殖容量：养殖区总淡干海带的养殖容量为21250t,单位面积养殖容量384 g/m2,单位面积个体养殖容量3.84 ind/m2,建议4 ind/m2的播苗密度。不添加饵料,鱼类网箱的养殖容量为6.81g/(a·m2);桑沟湾可放养鱼类总容量为850 t/a。更多还原

【Abstract】 South Yellow Sea(SSY) is an important offshore sea for China, and it is significant to study its ecosystem processes for understanding ecological mechanisms. Sanggou Bay(SB) is a typical aquaculture coastal area, and research on its ecosystem status is helpful to appropriate culturing activities in a such sea. The dissertation aims to model ecosystem processes for each of seas in different scale. The fist step is establishing a hydrodynamic model to reproduce physical processes of each sea. Based on the model, an ecosystem model is then developed by selecting variables and parameterizing bio-chemical processes. After validation, the model results are used to analysis the ecological characters for both seas.The hydrodynamic model of SYS almost completely includes the physical processes, such as tides, wind force, wave mixing, circulations, and so on. Variables of the SYS ecosystem model are phytoplankton, zooplankton, nutrients and detritus. For SB models, the effect of aquaculture to hydrodynamics is taken into account, and ecological elements include dissolved organic matter in addition to above variables. The processes of depletion or expiration of baits and nutrients by shellfish and large algae are parameterized. Based on the ecosystem model, the evaluation models of carrying capacity(CC) of shellfish, large algae, and fish are setup according to balance relationships between substance supply and demand or a nutrition dynamic relation respectively. The followings are obtained:For SYS:1) The wave mixing and tidal current make vertical diffusion coefficients crease with 10-3～10-1 m2/s in upper layers and lower layers respectively. They mix the coastal waters more uniform vertically, and enlarge the thickness of the mixed layers of both surface and bottom and increase the thermocline strength in deep sea areas. With tides, the SYS warm circulation and coastal circulations in winter, and Taiwan warm circulation, China’s coastal circulation and circulations of SYS central areas in summer are all weakened compared with results without tides. Besides, the direction of Korea coastal circulation in summer is reversed in counterclockwise. In this case, circulations of SYS central areas are southward and with lower velocities, while northward lack of tidal forces. 2) Both the primary production and the phytoplankton biomass are highest in spring, and second highest in summer, lowest in winter. A significant bloom happens in mid-April. In spring, the net inflow of phytoplankton of SYS is always positive and great, which is helpful to bloom formation. While in summer the net inflow is often negative. In most areas of SYS, the phytoplankton growth is limited to phosphorus.3) In the west coastal area, phytoplankton biomass is high from late April to early September, and stratification is unobvious. In areas near Changjiang River the biomass is highest on the whole in SYS, and the significant bloom appears in May. Along with distance increase from the river inlet, the biomass generally increases firstly and then falls. In the area, phytoplankton growths object to light limitation, and strong mixing processes preclude accumulation of phytoplankton. In SYS central areas, the stratification of phytoplankton is obvious from April to November, and the prominent bloom happens in late April. From May the subsurface layer, which has the highest biomass, deepens gradually. In August and September, the layer’s top is up to 30 m deep. For east areas, the ecological features are similar to central areas. The low layer exist upwelling flows, where nutrient concentration is high.4) Wave mixings and tides play important roles in formation of ecological characters. Wave mixings delay and strengthen the spring bloom. Regardless of the mixings, the bloom moves up 13d. The rationality of addition of the mixing to the model is analyzed.5) Runoff increases SYS biomass, especially for estuary.For SB:1) Observation indicates aquaculture activities reduce flows of culturing layers. By laying porous plates with friction, a model is developed to reproduce physical processes of the area. The friction coefficients are given. The half-exchange duration of SB is 7d without aquaculture,12d with shellfish only, and 16d with both shellfish and kelp culturing. In northwest and southwest areas of SB the water exchange ability is poor.2) As a whole, the phytoplankton biomass is relatively low in winter and high in summer, and appears a weak peak in February and a maximum in September. This is a common feature for culture areas of kelp, oyster and scallop. The ecological characters are related to aquaculture. In shellfish-culture areas, nutrient densities are high in summer and autumn, which is related with shellfish excretion.3) The CC of scallop is great in winter and autumn, small in spring and summer, and minimum in April. The annually averaged CC is 53 ind/m2, and the total CC is 10.1 billion individuals. The present density should not be enlarged. The CC of oyster is high in winter, low in summer, and lowest in late August and highest in mid-February. The CC is 76 ind/m2, and a total CC is 41.1～51.7 billion individuals for oyster-culture areas. The recommended density is 39333 ind per MU. The total CC of kelp is 21250 t, and the CC in density is 384 g/m2 i.e.3.84 ind/m2. A recommended seedling density is 4 ind/m2. Without addition of baits, the CC in a fish cage is 6.81 g/(a·m2). SB may stock 850t/a fish.更多还原