乳山湾东流区营养状况时,空变化及其评价

有机污染在时间上的变化为，7月前呈有机污染不断加剧的过程，到7月整个东流区均达到严重污染水平；7月后是污染程度逐渐减轻的过程，到9月整个东流区水质恢复到较好水平。有机污染程度在空间上的变化是从湾外向湾内逐渐加剧趋势。6、7和8月整个东流区均达到富营养化水平，但富营养化的程度有所不同，7月富营养化程度最严重，8月较7月减轻，到9月湾内基本恢复正常。与1994年8月比较，1995年8月东流区有机污染和富营养化程度有所加剧。     

辽东湾海蜇生长的研究

本文描述了辽东湾海蜇(Rhopilema esculenta Kishinouye)的生长特征。它与鱼虾类的生长特征不同，没有渐近值，到9月10日后个体收缩。我们用高次方程描绘了辽东湾海蜇的一般生长型。根据海蜇的一般生长型，研究了海蜇的生长速度。     

Annual net production of the five Sargassaceae species in Yoro,western Wakasa Bay,Sea of Japan

ABSTRACT:   Annual net production of the five Sargassaceae species was investigated in Yoro, western Wakasa Bay, Sea of Japan. The Sargassaceae species were collected at a depth of 2.0–2.5 m and subjected to stratified clipping for 13 months. Annual net production was estimated at 2407 g dry wt/m² for Sargassum patens , 2132 g dry wt/m² for Sargassum macrocarpum , 1458 g dry wt/m² for Sargassum siliquastrum , 1197 g dry wt/m² for Myagropsis myagroides , and 1471 g dry wt/m² for Sargassum piluliferum . The ratio of annual net production to maximum biomass (P/B_max) for these species ranged between 1.3 and 1.7, being higher than in previous studies which used the same method. Winter storms with strong wave exposure and relatively calm condition in Yoro were considered to augment P/B_max. The total losses estimated from the different units of stratified clipping were compared. If larger and less segregated units were applied, the total loss would decrease. It was suggested that a 50 cm stratum would be applicable to the larger species (3 m or longer) and a stratum of 20 cm or less would be applicable to mid-sized or smaller species (less than 3 m).     

Effects of tidal flat reclamation on sediment quality and hypoxia in Isahaya Bay

• 1. Ariake Bay, which is located in western Japan, has a large tidal range (>6 m) and a vast tidal flat (200 km²). In the early 1990s, the government‐managed Isahaya Reclamation Project began in the western part of Ariake Bay. A 16‐km² area of tidal flat in the inner part of Isahaya Bay was destroyed through reclamation and separated from the sea by a dyke, which created land and a freshwater reservoir.
• 2. Since the initiation of the project, fishery yields around Isahaya Bay have dramatically decreased. The objective of this study was to clarify the relationship between the work associated with the Isahaya Reclamation Project and the recent environmental deterioration in Ariake Bay, with references to present sediment thickness and organic matter content, and hypoxic water distributions in Isahaya Bay.
• 3. The organic matter load from the reservoir has increased since the initiation of the reclamation project and has been associated with a thick layer of fine sediment at the bottom of Isahaya Bay. The thickness of fine sediment and the total organic carbon content were higher in Isahaya Bay than in the freshwater reservoir.
• 4. Based on measurements in August 2001, hypoxic water spread widely in and around Isahaya Bay; the lowest dissolved oxygen (DO) concentration (0.53 mg L^?1) was observed just outside the dyke. An analysis based on a two‐layered box model using data obtained in August 2001 showed that the DO consumption rate in the bottom layer was high (0.61 mg O₂ L^?1 day^?1), and that 22–41% of the total organic carbon load needed to induce the hypoxic water was derived from the reclamation area.
• 5. Our findings strongly suggest that enclosed seas may suffer from eutrophic and hypoxic conditions because of their low seawater‐exchange rate. A comprehensive conservation programme and environmental assessment including physical and material transport processes in the system is needed to manage the environment of the enclosed sea.

Copyright © 2005 John Wiley & Sons, Ltd.     

红海湾水质营养状况分析

根据 1997年 8月～ 1998年 11月的调查数据 ,分析红海湾水域的营养水平及分布特点 ,以了解红海湾水域营养水平的分布特点及污染状况。红海湾水域的富营养化指数E的分布从北向南呈逐渐递减趋势 ,即长沙湾滩涂养殖区 >长沙湾浅海养殖区 >自然水域、龟龄岛水域 ,其中长沙湾滩涂养殖区和长沙湾浅海养殖区受污染明显 ,分别达高富营养化程度和富营养化程度 ;自然水域和龟龄岛水域则营养状况相似 ,基本上未受到明显的污染。E的季节变化趋势为春季 >秋季 >夏季 >冬季 ,除冬季处于贫营养状况外 ,其余 3个季节均达富营养化程度 ,其中以春季受到的污染最为严重 ,达高富营养化程度。分别根据CN/CP 值和E值所推断出的结论基本相同     

夏季杭州湾南岸慈溪滩涂泥螺种群空间分布格局

2004年7月对杭州湾南岸慈溪自然滩涂的泥螺种群进行了取样调查,分别采用Taylor幂法则、Iwao聚集格局回归分析法及Morisita指数公式计算和统计分析。结果表明:杭州湾南岸7个样地间泥螺种群密度差异极显著,种群空间格局在局域斑块尺度属于聚集型负二项分布。造成样地间密度差异的主要原因是人为干扰,泥螺种群的空间分布格局主要与滩涂上积水区域呈斑块状分布有关。     

流沙湾养殖结构优化与生态环境生物修复技术

建立了一种贝-鱼-藻养殖结构优化与生态环境生物修复系统,该系统通过网栏设置33.3hm2半封闭的养殖海区进行试验研究,在示范海区内设置3个功能不同的养殖区,贝类养殖与珍珠培育区、鱼类网箱养殖区、大型海藻栽培区,进行鱼类与大型海藻间养和珍珠培育。经过10个月的结构优化养殖和生态环境生物修复控制,示范海区水域水质和生物环境得以明显改善。示范海区透明度显著高于毗邻海区(P<0.05),悬浮物含量显著低于毗邻海区(P<0.05);示范海区总氮、总磷营养盐浓度随养殖期的延长逐渐升高,到9月份达到最高值,以后则逐渐下降;示范海区水域浮游生物数量随养殖时间的延长逐渐升高,浮游生物量明显高于毗邻海区(P<0.05)。示范海区养殖生物生长良好,共收获鱼类21365kg、大型海藻3091.3kg、珍珠33.5kg。育珠贝存活率为73.9%、育珠贝留核率为49.9%,优质珠比率13.7%、珠层厚度平均472μm,珍珠质量明显提高。示范海区光能利用率为0.20%,总能量转化效率为34.58%,单位净产量耗总能为2.8919MJ/kg。     

Hydrodynamic method for estimating production carrying capacity of coastal finfish cage aquaculture in Southeast Asia

This paper presents the development of a simple and generally applicable hydrodynamic method for the estimation of production carrying capacity (PCC) of coastal finfish cage aquaculture. Dimensional analysis was used to find significant and general interdependencies between the hydrodynamics at fish farm locations and particulate wastes deposited on the seafloor by fish farms. Modeled ratios of deposition to emission of particulate wastes underneath fish farms were found to be primarily a function of the flow Reynolds numbers at the farming locations and the non-dimensional settling velocity of emitted wastes. In the non-dimensional model, farming conditions include daily feed rate, proportion of unconsumed feed, and carbon content in feed and fish feces. The relationship can be used to estimate the PCC of floating net cages imposing a threshold value for deposition. Results of in-situ assessments of the benthic impacts of several fish farms in an aquaculture site in the northwest of Bali, Indonesia were used to validate and demonstrate the effectiveness of the method. Predicted results were able to clearly identify fish farms operating beyond ecologically sustainable carrying capacity. The proposed method has broad applicability and could help make decisions regarding the estimation of production potential of individual farms in pristine areas, for providing first estimates in sites that have scarce data, and for assessment, expansion, and optimization of the currently operating aquaculture sites in Southeast Asia, China and potentially other data-poor island nations. As the method relies on dynamic models, it enables straightforward assessments over the entire aquaculture region.     

Microcystin production during algal bloom occurrence in Laguna de Bay, the Philippines

ABSTRACT:   The amount of microcystin in Microcystis aeruginosa bloom was investigated during the rainy season of 1999 in Laguna de Bay, the Philippines. Bloom samples taken from the West Bay and East Cove stations of the lake were studied in relation to the characteristics of environmental conditions. Four types of microcystins, microcystin-LR (MC-LR), microcystin-RR (MC-RR), 6(Z)-Adda-microcystin-RR, and 3-desmethylmicrocystin-LR were identified from the natural bloom samples among which MC-LR was the most dominant type of microcystin. Production of microcystin (88.6 µg/100 mg dried cells) was highest during the first sampling week that coincided with high water transparency and high conductivity. The occurrence of a strong typhoon during the second sampling week had changed the environment drastically, which was characterized by low water transparency, high turbidity, low water temperature, and with trace amounts of MC-LR detected at the East Cove station. Thus, toxin production over time as well as the relationship between Microcystis production and toxin concentration could not be fully evaluated.     

Culture of Macrobrachium rosenbergii (De Man 1879) in experimental cages in a freshwater eutrophic lake at different stocking densities

Macrobrachium rosenbergii (de Man 1879) juveniles (0.4 g) were cultured in experimental cages (L × W × H: 2.5 × 1 × 1 m) in Laguna de Bay, the largest lake in the Philippines. The following stocking densities at four replicates each were used: 15, 30, 60 and 90 prawns m⁻² of cage bottom. The mean sizes at harvest after 5 months of culture ranged from 14.3 g for the highest stocking density to 26.3 g for the lowest. The mean size at harvest, daily growth rate and size class distribution were significantly influenced by stocking density, with those at the lowest stocking density showing significantly better growth and overall proportion of larger prawns. Heterogeneous individual growth (HIG) was fairly evident in all treatments. The percentage of blue‐clawed males was not influenced by treatment but the mean weight was significantly higher in the lower stocking densities. Both the percentage and mean weight of berried females were significantly higher in the lowest stocking density. Survival was the highest in the lower stocking densities (55.3%, 54.0%, 52.7% and 36.9% for 15, 30, 60 and 90 prawns m⁻² respectively). Feed conversion ratio (FCR) improved with decreasing stocking density, ranging from 2.1 to 3. As expected, yield per cropping increased with stocking density and ranged from 450 to 1089 g m⁻² yr⁻¹ of actual cage area. Production values obtained in the cage cultured M. rosenbergii were comparable to or even higher than those reported from pond culture, given that the stocking densities used in this study were generally higher than in ponds. The results show that the farming of M. rosenbergii in cages in lakes is a viable alternative to pond culture and has the potential of improve aquaculture production in lakeshore fish farming communities.