pH variability off Goa (eastern Arabian Sea) and the response of sea urchin to ocean acidification scenarios

The increasing atmospheric CO₂ concentration in the last few decades has resulted in a decrease in oceanic pH. In this study, we assessed the natural variability of pH in coastal waters off Goa, eastern Arabian Sea. pH_T showed large variability (7.6–8.1) with low pH conditions during south-west monsoon (SWM), and the variability is found to be associated with upwelling rather than freshwater runoff. Considering that marine biota inhabiting dynamic coastal waters off Goa are exposed to such wide range of natural fluctuations of pH, an acidification experiment was carried out. We studied the impact of low pH on the local population of sea urchin Stomopneustes variolaris (Lamarck, 1816). Sea urchins were exposed for 210 days to three treatments of pH_T: 7.96, 7.76 and 7.46. Our results showed that S. variolaris at pH_T 7.96 and 7.76 were not affected, whereas the ones at pH_T 7.46 showed adverse effects after 120 days and 50% mortality by 210 days. However, even after exposure to low pH for 210 days, 50% organisms survived. Under low pH conditions (pH_T 7.46), the elemental composition of sea urchin spines exhibited deposition of excess Sr²⁺ as compared to Mg²⁺ ions. We conclude that although the sea urchins would be affected in future high CO₂ waters, at present they are not at risk even during the south-west monsoon when low pH waters reside on the shelf.     

浙江南部外海鱼类种类组成和数量分布

根据2006年5月、9月、11月和2007年2月浙江南部外海渔业资源调查结果,用渔获率作为鱼类资源分布的数量指标,对浙江南部外海的鱼类种类组成、数量分布、季节变化趋势作了定量分析。结果表明,浙江南部外海调查海域鱼类种类约有205种,其中海南鲽鲆、长臂沙鲽是2个东海区新记录种。刺鲳、竹笑鱼、发光鲷、条尾鲱鲤、尖牙鲷、短鳍红娘鱼、短鳄齿鱼、带鱼、多棘腔吻鳕、花斑蛇鲻等22种鱼类是调查海域底拖网的主要捕捞鱼类,约占鱼类总渔获量的64．58％,而其它种类的渔获量较少。不同季节的经济鱼类渔获物组成相差较大,渔获量高峰期主要出现在夏、秋季,主要捕捞刺鲳、竹笑鱼、条尾鲱鲤、短鳍红娘鱼、黄鳍马面钝等,而带鱼主要出现在春、夏季和冬季。资源数量分布较高的海区是27°30′-28°30′N海域以及26°00′-27°00′N、121°30′-123°00′E海域,而春季、秋季和冬季虽然资源密度没有夏季高,秋季和冬季调查海域的鱼类资源数量明显下降,但其数量的地理分布趋势与夏季基本相同。主要种类的空间分布特点如下：刺鲳、带鱼、海鳗、日本红娘鱼、日本方头鱼等的主要渔场分布在80-100m水深海域;黑鲮蟓、真鲷、鲐鱼、高体若鳕等的主要渔场分布在100-200m水深海域;而竹笑鱼、条尾鲱鲤、短鳍红娘鱼等则在整个调查海域都有分布,属于分布范围广的种类。     

2006年冬季北黄海网采浮游植物群落结构

根据2006年12月30日—至2007年1月17日北黄海的调查资料,对该海域浮游植物的种类组成、优势种、丰度及其分布和多样性等基本状况进行了分析。本次调查共鉴定浮游植物4门68属131种,主要以温带近岸和广布性种为主,其中硅藻有53属113种,占总种数的86.3%,甲藻有11属16种,占总种数的12.2%。浮游植物丰度平均值为88.89×104个/m3,硅藻丰度平均值为86.58×104个/m3,甲藻丰度平均值为2.28×104个/m3,硅藻丰度分布趋势决定了浮游植物丰度的分布趋势。辽宁南岸是浮游植物密集区,山东半岛北岸其次,而北黄海中部是浮游植物的稀疏区。优势种为:短角弯角藻(Eucampia zodiacus)、具槽帕拉藻(Paralia sulcata)、尖刺拟菱形藻(Pseu-do-nitzschia pungens)、密连角毛藻(Chaetoceros densus)、柔弱角毛藻(Chaetoceros debilis)、刚毛根管藻(Rhizosolenia setigera)。浮游植物群落Shannon-Weiner物种多样性指数平均值为1.80,Peilou均匀度指数平均值为0.42。与1959年1月相比,2007年1月北黄海浮游植物丰度由150.00×104个/m3降为88.89×104个/m3,下降了近41%,硅藻丰度由148.00×104个/m3降为86.58×104个/m3,而甲藻丰度由1.25×104个/m3上升为2.28×104个/m3,占浮游植物丰度的比例由0.8%上升为2.5%。主要优势种及优势属也发生了一定程度的变化,但浮游植物群落结构仍以硅藻为主、甲藻其次,浮游植物丰度总的分布格局变化不明显。     

Microphytobenthic biomass and species composition in intertidal flats of the Nakdong River estuary, Korea

Intertidal microphytobenthos (MPB) were investigated monthly from August 2006 to March 2008 at four different sites in the sand flats of Nakdong River estuary, Korea. Samples of surface sediment (ca. 1 cm) were collected, and chlorophyll a was extracted as biomass estimation. Species identification and enumeration were carried out by light microscopy, assisted where necessary by scanning electronic microscopy. Biomass varied between 0.47 and 16.58 μg cm⁻³, abundance changed from 5.25 to 414.75 × 10³ cells cm⁻³, while the Shannon diversity indexes ranged between 0.69 and 2.35 H′. Thirty-nine MPB taxa were identified, primarily composed of epipelic diatoms, among which Amphora and Navicula were the most abundant genera. Based on the biomass, abundance, species composition and their dynamics, MPB assemblages of sampling sites were grouped into three distinct communities corresponding to their sediment composition characteristics. Multivariate correlation analysis revealed that biomass was positively related to mud and very fine sand, negatively related to fine and medium sand, but not significantly related to environmental factors such as pore water nutrients, light intensity and salinity, which fluctuated rapidly during emersion period. Cluster analysis corroborated the division of MPB communities according to site types on seasonal scales, and also showed seasonality between sites by cluster of all summer groups. Principal component analysis identified that variability in species composition was significantly affected by mud, very fine sand, fine sand, light intensity, and sediment temperature. This study suggests that sediment composition plays an important role in the functioning of intertidal MPB communities in estuarine ecosystems.     

Effects of iron limitation on intracellular cadmium of cultured phytoplankton: Implications for surface dissolved cadmium to phosphate ratios

This study compares intracellular Cd content (Cd:C) of cultured marine phytoplankton grown under various Fe levels, with estimated particulate Cd:P ratios derived from regression slopes of Cd versus PO₄³⁻ relationships from a global dataset. A 66-fold difference in Cd:C ratios was observed among the seven species grown under identical Fe concentrations, with oceanic diatoms having the highest Cd quotas and prymesiophytes the lowest. Interestingly, all species significantly increased their Cd:C ratios under Fe-limitation (on average 2-fold). The global data set also showed that the mean estimated Cd:P ratio of surface water particulates in HNLC (high nutrient low chlorophyll) regions were approximately 2-fold higher than non-HNLC regions. A sequence of events are proposed to explain high Cd:P ratios in HNLC waters. First, the seasonal relief from Fe-limitation in HNLC regions leads to blooms of large chain forming diatoms with high intrinsic Cd:P ratios. These large blooms may, in theory, deplete surface water CO₂ and Zn concentrations, which ultimately, would result in increased Cd uptake. Eventually these blooms will run out of Fe, which has been shown to further increase intercellular Cd via growth biodilution and increased Cd uptake through non-specific Fe(II) transporters. Ultimately, Fe-limited diatoms with enhanced Cd quotas will sink out of surface waters leading to pronounced regional differences in Cd:P ratios between HNLC and non-HNLC waters in the global ocean.     

Winter distribution of euphausiids (Euphausiacea) in the Barents Sea (2000–2005)

The purpose of the study is to analyze the state of the Barents Sea euphausiids populations in the warm period (2000–2005) based on the study of their structure dynamics and distribution under the influence of abiotic and biotic factors. For estimation of their aggregations in the bottom layer, the traditional method was used with the help of the modified egg net (0.2 m² opening area, 564 μm mesh size). The net is used for collecting euphausiids in the autumn–winter period when their activity is reduced, which results in high-catch efficiency. The findings confirmed the major formation patterns of the euphausiids species composition associated with climate change in the Arctic basin. As before, in the warm years, one can see a clear-cut differentiation of space distribution of the dominant euphausiids Thysanoessa genus with localization of the more thermophilic Thysanoessa inermis in the north-west Barents Sea and Thysanoessa raschii in the east. The major euphausiids aggregations are formed of these species. In 2004, the first data of euphausiids distribution in the northern Barents Sea (77–79°N) were obtained, and demonstrated extremely high concentrations of T. inermis in this area, with the biomass as high as 1.7–2.4 g m⁻² in terms of dry weight. These data have improved our knowledge of the distribution and euphausiids abundance during periods of elevated sea-water temperatures in the Barents Sea. The oceanic Atlantic species were found to increase in abundance due to elevated advection to the Barents Sea during the study period. Thus, after nearly a 30-year-long absence of the moderate subtropical Nematoscelis megalops in the Barents Sea, they were found again in 2003–2005. However in comparison with 1960, the north-east border of its distribution considerably shifted to 73°50′N 50°22′E. The portion of Meganyctiphanes norvegica also varied considerably—from 10% to 20% of the total euphausiids population in the warm 1950s–1960s almost to complete disappearing in 1970–1990s. The peak of this species’ occurrence (18–26%) took place in the beginning of warm period (1999–2000) after a succession of cold years. The subsequent reduction of the relative abundance of M. norvegica to 7% might have been mostly caused by fish predation during a period of low population densities of capelin. This high predation pressure may therefore have been mediated both by other pelagic fishes (i.e. herring, blue whiting, polar cod) but also by demersal fishes such as cod and haddock. Similar sharp fluctuations in the capelin stock (the major consumer of euphausiids) created marked perturbations in the food web in the Barents Sea in the middle 1980s and the early 1990s.     

氮、磷对大亚湾大鹏澳海区浮游植物群落的影响Ⅱ种类组成

根据2005年4－5月（春季）、8月（夏季）和11月（秋季）对大亚湾大鹏澳海区表层的现场调查结合营养盐加富实验,探讨了不同季节氮（NO3－或脲氮 (urea)）和无机磷（PO43－）营养元素对浮游植物种类组成的潜在影响。大鹏澳海区浮游植物优势种有明显季节变化,秋季种类组成的平面变化最明显。春季浮游植物平均细胞密度最高但多样性指数最低。实验结果显示,春季至夏季浮游植物优势种翼根管藻模式变型Rhizosolenia alata f. genuina、丹麦细柱藻Leptocylindrus danicus和绕孢角毛藻Chaetoceros cinctus之间的演替可能受氮、磷条件变化的控制。夏季优势种菱形海线藻Thalassionema nitzschioides和威氏海链藻Thalassiosira weissflogii之间的演替可能受营养条件外的因素控制。尽管磷被认为是该海区浮游植物生长的主要限制因子,但夏季无机氮磷比值较高的实验组中未出现磷限制现象,无机氮磷比值的变化对浮游植物种类组成也没有显著影响,而秋季氮对浮游植物种类组成有较明显的潜在影响。     

黄海中南部头足类的群落结构与生物多样性

为掌握黄海中南部头足类的群落结构及数量分布,作者根据2010~2011年间春、秋、冬3个季节的底拖网调查资料,对黄海中南部头足类的种类组成、生物量分布及生物多样性进行了研究。结果显示:3个季节共捕获头足类13种,隶属3目6科6属。各季节的优势种及其生物量比重分别为:春季——双喙耳乌贼(Sepiola birostrata)50.07%、秋季——针乌贼(Sepia esculenta)40.88%、冬季——枪乌贼(Loligo spp.)68.20%。各季节头足类平均资源密度分别为春季4.85 kg/km2、秋季2.52 kg/km2、冬季12.72 kg/km2,春秋两季间差异性不显著(P0.05),冬季与其他两季差异性显著(P0.05)。黄海中南部不同季节头足类的生物量分布变化较大,春季以西南及东北部密度最高,秋季以西南部密度最高,冬季以中部及东北部密度最高。头足类在各水深的垂直分布随季节变化。无论根据生物量还是丰度,种类丰富度指数、均匀度指数及Shannon-Wiener指数等多样性指数均以冬季最高,其次是春季,秋季最低。春季与冬季群落结构相似性较高,秋季与其他两个季节的群落结构相似性均较低。与1998~2000年同期相比,头足类种类数增加5种,相对资源密度增长了12%,枪乌贼类的生物量比重仍最高,耳乌贼类的比重提高,太平洋褶柔鱼的比重则大幅下降。     

白令海北部悬浮体含量分布及其颗粒组分特征

对中国第四次北极科学考察期间在白令海北部获取的海水样品进行悬浮体含量及其颗粒组分特征的分析。结果表明,白令海陆架海区悬浮体含量大体呈现出表层浓度低而底层浓度高的特点。表层海水悬浮体含量在白令海峡西侧和陆架东侧靠近阿拉斯加沿岸含量较高,而底层海水中悬浮体含量则在白令海峡西侧,以及白令海陆架西南部的圣马修岛西北侧较高。陆架流系对底床物质的再悬浮作用致使白令海悬浮颗粒物浓度的高值区多位于近底层海水中。受白令陆坡流沿陆架坡折带输运作用,研究区西南部悬浮体浓度较高。白令海陆架水以及阿纳德尔流携带悬浮颗粒向北输运,使得底层悬浮体浓度呈现出自南向北逐渐减弱的模式。圣劳仑斯岛以北靠近楚科奇半岛一侧海域,受高营养盐的阿纳德尔流的影响,悬浮颗粒物以藻类为主;东侧阿拉斯加沿岸流区悬浮颗粒则以陆源的碎屑矿物为主。     

饲料中添加胜肽和益生菌对大黄鱼生长性能和体组成的影响

以初始体重为48.23±1.25 g的大黄鱼(Larimichthys crocea)为试验对象,研究饲料中添加胜肽和益生菌对大黄鱼生长性能、体组成的影响.添加胜肽试验组所用饲料为添加500mg/kg胜肽产品配制成软颗粒饲料;添加胜肽-益生菌试验组所用饲料为添加500mg/kg胜肽产品和500mg/kg益生菌产品配置成的软颗粒饲料;对照组所用饲料为未添加胜肽和益生菌产品而以相同配方配制成的软颗粒饲料.整个养殖试验的周期为12周,并于海水浮式网箱中进行.结果表明,饲料中添加胜肽和胜肽-益生菌均显著提高大黄鱼的终末体质重(FW)、特定生长率(SGR)、鱼体增重率(WGR)、饲料效率(FE)和粗脂肪含量(p0.05);饲料中添加胜肽对大黄鱼水分、粗蛋白、灰分、肝脏指数(HSI)、内脏指数(VSI)和肥满度(CF)的影响不显著(p0.05);添加胜肽-益生菌饲料组VSI显著高于添加胜肽饲料组和对照组(p0.05).