Investigating internal waves east of the Hainan Island using optical satellite remote sensing data

Marginal water of east Hainan Island was an area that internal waves occurred frequently, however, few studies was found and mechanism for internal waves formation was unclear. In the paper, China Brazil earth Resources Satellite data (CBERS) was used to detect and calculate distribution, direction, wavelength and amplitude of internal waves in marginal water of east Hainan Island and the mechanism of internal waves formation was also analyzed, results showed that direction of internal wave was off shoreward and wavelength was about 150-200m . The mechanism for internal wave’s formation can be postulated as by upwelling or tide tracing back.     

Microbial photosynthesis in coral reef sediments (Heron Reef, Australia)

We investigated microphytobenthic photosynthesis at four stations in the coral reef sediments at Heron Reef, Australia. The microphytobenthos was dominated by diatoms, dinoflagellates and cyanobacteria, as indicated by biomarker pigment analysis. Conspicuous algae firmly attached to the sand grains (ca. 100 μm in diameter, surrounded by a hard transparent wall) were rich in peridinin, a marker pigment for dinoflagellates, but also showed a high diversity based on cyanobacterial 16S rDNA gene sequence analysis. Specimens of these algae that were buried below the photic zone exhibited an unexpected stimulation of respiration by light, resulting in an increase of local oxygen concentrations upon darkening. Net photosynthesis of the sediments varied between 1.9 and 8.5 mmol O₂ m⁻² h⁻¹ and was strongly correlated with Chl a content, which lay between 31 and 84 mg m⁻². An estimate based on our spatially limited dataset indicates that the microphytobenthic production for the entire reef is in the order of magnitude of the production estimated for corals. Photosynthesis stimulated calcification at all investigated sites (0.2–1.0 mmol Ca²⁺ m⁻² h⁻¹). The sediments of at least three stations were net calcifying. Sedimentary N₂-fixation rates (measured by acetylene reduction assays at two sites) ranged between 0.9 to 3.9 mmol N₂ m⁻² h⁻¹ and were highest in the light, indicating the importance of heterocystous cyanobacteria. In coral fingers no N₂-fixation was measurable, which stresses the importance of the sediment compartment for reef nitrogen cycling.     

Characteristics of bottom dissolved oxygen in Long Island Sound,New York

The variability of bottom dissolved oxygen (DO) in Long Island Sound, New York, is examined using water quality monitoring data collected by the Connecticut Department of Environmental Protection from 1995 to 2004. Self-organizing map analysis indicates that hypoxia always occurs in the Narrows during summer and less frequently in the Western and the Central Basins. The primary factor controlling the bottom DO, changes spatially and temporally. For non-summer seasons, the levels of bottom DO are strongly associated with water temperature, which means DO availability is primarily driven by solubility. During summer, stratification intensifies under weak wind conditions and bottom DO starts to decrease and deviate from the saturation level except for stations in the Eastern Basin. For the westernmost and shallow (<15 m) stations, bottom DO is correlated with the density stratification (represented by difference between surface and bottom density). In contrast, at deep stations (>20 m), the relationship between oxygen depletion and stratification is not significant. For stations located west of the Central Basin, bottom DO continues to decrease during summer until it reaches its minimum when bottom temperature is around 19–20 °C. In most cases the recovery to saturation levels at the beginning of fall is fast, but not necessarily associated with increased wind mixing. Therefore, we propose that the DO recovery may be a manifestation of either the reduced microbial activity combined with the depletion of organic matter or horizontal exchange. Hypoxic volume is weakly correlated to the summer wind speed, spring total nitrogen, spring chlorophyll a, and maximum river discharge. When all variables are combined in a multiple regression, the coefficient of determination (r²) is 0.92. Surprisingly, the weakest variable is the total nitrogen, because when it is excluded the coefficient r² only drops to 0.84. Spring bloom seems to be an important source of organic carbon pool and biological uptake of oxygen plays a more crucial role in the seasonal evolution of bottom DO than previously thought. Our results indicate that the reassessment phase of the Long Island Sound Total Maximum Daily Load policy on nitrogen loading will most likely fail, because it ignores the contributions of the spring organic carbon pool and river discharge. Also, it is questionable whether the goal of 58.5% anthropogenic nitrogen load reduction is enough.     

Factors controlling dissolved silica in coral reef surface water of Urasoko Bay, Ishigaki Island, Japan

From August 2006 to August 2007, the concentrations of dissolved silica (Si(OH)₄) were monitored in the surface water of Urasoko Bay and the mouth of the stream that runs into the bay. Urasoko Bay is located on the northern coast of Ishigaki Island, Okinawa, Japan, which is in a subtropical area of the North Pacific Ocean and is surrounded by a relatively poorly developed fringing reef. Added to these samples were freshwater from the upstream area and brackish water that exudes at the beach site, which were collected from April to June 2007. Rainwater samples were also collected during the study period. The concentration of Si(OH)₄ generally decreased from upstream to the bay site, and, on clear days, Si(OH)₄ data from all study sites (the bay, beach, stream mouth, and upstream) plotted against salinity fell on a single straight line. When the influence of rainwater was, the results were scattered below the straight line, which suggests dilution by rainwater with a much lower Si(OH)₄ concentration. These findings show that offshore seawater, rainwater, and upstream freshwater regulate the concentration of Si(OH)₄ in the surface water of Urasoko Bay.     

褐菖鲉网箱养殖试验初报

2001年4月30日在浙江南麂海域3 m×3 m×3 m网箱中放养0.9 g自然海区捕获的褐菖鲉(Sebastiscus marmoratus)苗种,进行为期2年多的养殖试验.结果表明,该鱼生长缓慢,养殖38 d体质量为8.3 g,养殖240 d为24.8 g,养殖787 d为112.3 g.总养殖成活率为20.1%,平均日增体质量0.142 g,平均日增体质量率0.62%.秋末至夏初低水温期是褐菖鲉的主要生长期,在9～13℃较低水温下亦会摄食与生长.饵料系数为3.6.冬春季养殖成活率高于秋夏季,第一年夏季养殖成活率低,仅28.1%.养殖方式以混养为宜.     

南麂列岛大沙岙沙滩贝类的时空分布

南麂列岛作为观光旅游的休闲去处正在日益升温,其中沙滩游玩是最大的活动亮点,大沙岙是南麂列岛最具代表性的沙滩,沙滩内生活着较多贝类,随大量人员的涌入和沿岸环境污染的日趋加重,大沙岙沙滩贝类的栖息地环境受到了较大程度的危害、人为活动正影响着贝类的生长发育。为探明近年来大沙岙贝类种类、数量及群落结构的变化,在南麂列岛国家海洋自然保护区建立初期(1992年)生态调查的基础上,于2003年再次对大沙岙贝类进行了采样分析,结果表明:大沙岙沙滩12种贝类的平均生物量和栖息密度分别为30.16g/m2和20个/m2,北断面开放区贝类的平均生物量和栖息密度(13.98g/m2和11个/m2)明显少于受监控的南断面核心区(46.33g/m2和30个/m2),贝类的平均生物量和栖息密度的垂直分布低潮区(48.43g/m2和31个/m2)高于中潮区(28.03g/m2和20个/m2),贝类的平均栖息密度7月高于3月,北断面贝类的季节变化、多样性和均匀度指数大于南断面。与建区初期同季调查资料比对发现,2003年北断面贝类数量下降幅度(14倍)显著大于南断面贝类下降幅度(1倍)。分析认为,自然环境变化和人为采捕是影响沙滩贝类数量下降的主要外部因子。     

海南岛近海海域7个沉积岩芯的现代沉积速率及其分布特征

利用多道α能谱仪,对2005年8～9月在海南岛近海采集的7个沉积岩芯进行了210Pb的沉积速率测定,探讨了海南岛近海陆架上现代沉积速率的区域性分布特征,结果表明:位于港湾内的B1168站位由于沉积物供应充足,有最高的沉积速率,达2.9 cm/a;位于河口海湾附近且受沿岸流影响的B289站位,有很高的沉积速率,可达1.6 cm/a,沉积环境较稳定;位于西南海底沙脊区北缘且靠近昌化江河口的B97、B135、B10站位也有较高沉积速率,分别达到1.0、0.89和0.47 cm/a,在表层都出现了210Pb放射性活度倒置的现象,表明所处区域有较强混合作用;处于西南外陆架的C4站位受北部湾环流影响,沉积速率为0.6 cm/a;位于东部外陆架的B377站位处于上升流区,沉积速率较低,为0.21 cm/a.可见,海南岛近海陆架上的现代沉积速率存在着明显的区域分布:在物质来源丰富的沿岸流作用区和河口区附近,现代沉积速率很高;在陆架环流沉积作用区,现代沉积速率也较高;在水深较大的外陆架上,由于沉积物供应相对匮乏,沉积速率一般较低;在近岸潮流沙脊区,由于水动力很强,无法形成现代细粒沉积.同时,在陆架上,沉积速率有随着水深的增加而降低的趋势.由此可见,海南岛近海海域的沉积速率与该区的物质供应、水动力条件和海底地形等因素有密切关系.     

Denitrification in Qi'ao Island coastal zone, the Zhujiang Estuary in China

Samples of sediments and the overlying water were collected in the Qi'ao Island coastal zone, the Zhujiang (Pearl River) Estuary (ZE). Denitrification rates, sediment oxygen demand (SOD) , and fluxes of inorganic nitrogen compounds were investigated with N2 flux method, using a self-designed continuous flow through and auto-sampling system. The results indicate that the denitrification rates varied between 222 and 908 μmol/(m2·h) with an average of 499 μmol/(m2·h). During incubation, the sediments absorbed dissolved oxygen in the overlying water with SOD ranging from 300 to 2 363 μmol/(m2·h). The denitrification rates were highly correlated with the SOD (r2 =0.77) regardless of the NO3- + NO2- concentrations in the overlying water, organ- ic carbon contents in sediments and water temperature, suggesting that the SOD was probably the main environ-mental factor controlling the denitrification in the Qi'ao Island coastal zone. There was a net flux of NO3- + NO2-into the sediments from the overlying water. The NH4+ flux from sediments into water as the result of mineraliza-tion was between 12. 3 and 210. 3 μmol/(m2·h) ,which seems limited by both organic carbon content in sedi-ment and dissolved oxygen concentration in the overlying water.     

海南岛西北部莲花山周缘海相地层的区内对比及意义

根据岩性、产状和地貌等特征,对海南岛西北部莲花山周缘海岸出露的前全新世海相地层5个典型剖面进行区内对比,以恢复该套地层的产出序列,并推测海相地层的分布范围。结合海相地层的沉积时代和莲花山周缘海岸的地貌特征,探讨了该海岸带的地貌演化过程:中更新世以前,有河流自东南向西北经德义岭、莲花山入海,海相地层沉积区属于滨岸环境,是该海岸带当时受海水进退作用的主要区域,接受着波浪从北面、河流从南面带来的沉积物;中更新世至今,受雷琼地区火山活动的影响,河流被隆起的火山锥阻挡而截流或改道,海相地层沉积区则被抬升成为陆地,并在全新世海岸侵蚀作用下,形成了现今宽广的海蚀平台,海岸后退平均速率约为10 cm/a。     

大嵛山附近海域游泳动物种类组成和资源现状及其变化分析

2006年1月～10月福建闽东大嵛山附近海域游泳动物调查研究结果表明,该海域的游泳动物有97种,其中鱼类51种（软骨鱼1种,硬骨鱼类50种）,隶属于9目24科42属;甲壳类42种,隶属于2目15科20属;头足类4种,隶属于3目3科3属.暖水性种类为33种,占鱼类总种数的64.7%;暖温性鱼类18种,占鱼类总种数的35.3%,未出现冷温性和冷水性鱼类.种类数的季节变化依次呈夏季〉冬季〉秋季〉春季.生物量的季节变化,依次呈夏季〉秋季〉春季〉冬季;而生物量尾数的季节变化,依次呈夏季〉春季〉秋季〉冬季.平均单位网次渔获生物量和密度分别为9.53kg/h和1 319 ind/h.生物量优势种和密度优势种分别为大黄鱼和中华管鞭虾.扫海面积法估算年平均现存资源量为57 370 ind/km^2和404.51kg/km^2.同时,本文对该海域游泳生物的资源结构现状与历史调查数据作了对比分析,并讨论了多样性结构与生物量的季节性变化规律.结果表明,该海域渔业资源有严重衰退的现象,多样性结构与生物量的季节性变化并不具有必然的一致性.