Phytoplankton biomass and size fractions in surface waters of the Australian sector of the southern ocean

We collected surface water along the 142nd E meridian from Tasmania to Antarctica in December 1999. We measured temperature, salinity and total chlorophyll a; additionally, we collected suspended particle size fractions and used fluorometric analysis to determine the quantity of chlorophyll a in each of four cell size classes: picoplankton (<3 μm), two nanoplankton fractions (3–10 μm and 10–20 μm) and microplankton (> 20 μm). Changes in temperature and salinity show that we crossed 6 water masses separated by 5 fronts. We found low abundance (<0.2 mg m⁻³) of chlorophyll in all size classes, with the exception of higher values near the continent (0.2 to 0.4 mg m⁻³). Lowest chlorophyll values (<0.1 mg m⁻³) were found in the Polar Frontal Zone (51° to 54°S). Microplankton made up the largest portion of total chlorophyll throughout most of the region. We conclude that biomass of all phytoplankton fractions, especially pico-and nanoplankton, was constrained by limiting factors, most probably iron, throughout the region and that ecosystem dynamics within a zone are not circumpolar but are regionalized within sectors.     

盐度对六株硅藻生长及脂肪酸组成的影响

在温度为22±1℃,盐度为18‰、28‰和38‰的条件下,用F/2培养基对青岛海洋大学微藻种质库保存的6株硅藻(纤细角毛藻Chaetoceros gracilis B13; 筒柱藻Cylindrotheca fusiformis B211;三角褐指藻 Phaeodactylum tricomutum B114, B118,B221;新月菱形藻 Nitzschia closterium B222) 进行培养,在指数生长期末期进行收获,测定了6株硅藻的生长及脂肪酸组成.实验结果表明: 盐度对六株硅藻的生长及脂肪酸组成均有影响,但作用结果因种而异.B13的相对生长率随着盐度的增加而增加;B114和B222的相对生长率随着盐度的增加而降低.B13的干重随着盐度的增加而增加,在盐度为38‰时达到最大值(0.21);B118、B114、B221 和B222的干重均在盐度为28‰时达到最大值;盐度对B211的干重影响不明显(0.35～0.36).六株硅藻的主要脂肪酸为16:0、16:1(n-7)和20:5(n-3),B211还含有较多的20:4n-6(5.6～7.4‰),B13含有较多的14:0 (20.O～30.9%).B211、B221和B222的饱和脂肪酸总合随着盐度的增加而降低,在盐度为18‰时达到最大值(占总脂肪酸的百分比分别为41.7%、37.6%和31.7%).而B13、B118和B114的饱和脂肪酸总合在盐度为28‰时含量最高(分别为48.1%、31.0%和33.0%).B118、B114、B221和B222的单不饱和脂肪酸总合随着盐度的增加而增加,而B13和B211单不饱和脂肪酸总合随着盐度的增加而降低.B13、B118、B114和B222的多不饱和脂肪酸总合在18‰时含量最高(分别为31.3%、23.4%、19.6%和18.6%).B211和B221的多不饱和脂肪酸总合在28‰时含量最高(分别为25.1%和16.3%).     

Physiological and behavioral responses of Bathynerita naticoidea (Gastropoda: Neritidae) and Methanoaricia dendrobranchiata (Polychaeta: Orbiniidae) to hypersaline conditions at a brine pool cold seep

Bathynerita naticoidea (Gastropoda: Neritidae) and Methanoaricia dendrobranchiata (Polychaeta: Orbiniidae) are two of the most abundant invertebrates associated with cold‐seep mussel beds in the Gulf of Mexico. At the methane seep known as Brine Pool NR‐1 (27 °43.415 N, 91 °16.756 W; 650 m depth), which is surrounded by a broad band of mussels (Bathymodiolus childressi), these species have distinctly different patterns of abundance, with the gastropod being found mostly at the outer edge of the mussel bed (average density in November 2003: 817 individuals·m⁻² in outer zone, 20·m⁻² in inner zone) and the polychaete being found almost exclusively near the inner edge (average density in November 2003: 3155 individuals·m⁻² in inner zone, 0·m⁻² in outer zone), adjacent to the brine pool itself. The salinity of the brine pool exceeds 120, so we hypothesized that M. dendrobranchiata should be more tolerant of high salinities than B. naticoidea. The opposite proved to be true. The gastropods were capable of withstanding salinities at least as high as 85, whereas the polychaetes died at salinities higher than 75. Both species were osmoconformers over the range of salinities (35–75) tested. Behavioral responses of B. naticoidea to salinities of 50, 60, and 70 were investigated in inverted vertical haloclines. Gastropods generally did not enter water of salinity greater than 60, but tolerated short periods at 60. Behavioral avoidance of brine should limit the vertical distribution of B. naticoidea in the inner zone to the top 2.5–5 cm of the mussel bed. Behavior is also a likely (though unproven) mechanism for controlling horizontal distribution of this species across the mussel bed. Methanoaricia dendrobranchiata can tolerate short excursions into the brine, but probably avoids hypersaline conditions by aggregating on the tops of the mussels.     

The history of water salinity in the Pearl River estuary,China, during the Late Quaternary

This research reconstructed the Late Quaternary salinity history of the Pearl River estuary, China, from diatom records of four sedimentary cores. The reconstruction was produced through the application of a diatom–salinity transfer function developed based on 77 modern surface sediment samples collected across the estuary from shallow marine environment to deltaic distributaries. The statistical analysis indicates that the majority of sediment samples from the cores has good modern analogues, thus the reconstructions are reliable. The reconstructed salinity history shows the older estuarine sequence formed during the last interglacial was deposited under similar salinity conditions to the younger estuarine sequence, which was formed during the present interglacial. Further analysis into the younger estuarine sequence reveals the interplays between sea level, monsoon‐driven freshwater discharge, and deltaic shoreline movement, key factors that have influenced water salinity in the estuary. In particular, a core from the delta plain shows the effects of sea‐level change and deltaic progradation, while cores from the mouth region of the estuary reveal changes of monsoon‐driven freshwater discharge. This study demonstrates the advantages of quantitative salinity reconstructions to improve the quality of reconstruction and allow direct comparison with other quantitative records and the instrumentally observed values of salinity. Copyright © 2010 John Wiley & Sons, Ltd.     

湖相深水细粒物质的混合沉积作用探讨*

沉积物的混合是自然界的普遍现象,湖盆中广泛发育的深水细粒沉积岩本身就是一类混积岩。以东营凹陷古近系沙河街组三段下亚段—沙河街组四段上亚段细粒沉积岩为研究对象,通过厘米级岩心观察描述、小型沉积构造解剖、岩石薄片观察、X射线衍射全岩矿物分析及微量元素测试等方法,研究细粒物质的产出状态和混合方式;分析湖盆流体、气候及水体性质对细粒物质迁移、混合、沉积的控制作用,尝试探讨细粒物质的混合沉积机制。结果表明,湖相深水细粒沉积岩既有物质成分上的混合,也有结构的混合,且在宏观与微观的不同尺度均存在混合;混合沉积作用有均匀混合、纹层叠置混合、不均匀团块状混合等类型。纹层叠置混合沉积是最主要的混合沉积方式,依据纹层接触关系、所占比例及矿物产出状态可分为泥砂—灰纹层叠置混合型、泥—灰纹层叠置混合型、泥砂粒序—灰纹层叠置混合型、灰—泥—云纹层叠置混合型等。湖相深水细粒物质的混合沉积作用类型多且往往受多个因素同时控制,气候及水动力条件是控制细粒混合沉积岩发育的最主要因素,不同流体(浊流和底流)作用下的细粒沉积物混合作用存在差异。气候引起湖水性质变化及水体分层,从而控制不同类型细粒物质的絮凝沉降及化学沉积。不同构造部位、不同水体深度的混合作用不同;相同构造部位在垂向上也存在混合沉积方式的差异。     

温度和盐度对龙虎斑存活与摄食的影响

龙虎斑是由棕点石斑鱼(Epinephelusfuscoguttatus♀)和鞍带石斑鱼(Epinepheluslanceolatus♂)的杂交种。研究水温及盐度在骤变和渐变情况下龙虎斑的存活和摄食情况,结果表明:龙虎斑在温度为14³5℃的海水中均能存活和摄食,最适宜温度环境为2535℃的海水中均能存活和摄食,最适宜温度环境为25³5℃;温度从30℃骤变至20、25、35℃时,龙虎斑100%存活;从30℃骤变至10℃和15℃时,龙虎斑全部死亡;水温从30℃开始渐变,下降幅度为1℃/d,当下降至24℃时摄食减少,13℃时停止摄食,下降至11℃时出现死亡。龙虎斑在盐度为135℃;温度从30℃骤变至20、25、35℃时,龙虎斑100%存活;从30℃骤变至10℃和15℃时,龙虎斑全部死亡;水温从30℃开始渐变,下降幅度为1℃/d,当下降至24℃时摄食减少,13℃时停止摄食,下降至11℃时出现死亡。龙虎斑在盐度为1⁵5的海水中均能存活和摄食,摄食适宜海水盐度为455的海水中均能存活和摄食,摄食适宜海水盐度为4⁴5;盐度从30骤变至5、10、15、20、25、35、40、45、50、55等盐度时,龙虎斑100%存活,骤变至0时,4 h内存活率100%,16 h存活率55.5%;盐度从30渐变,每天降低2,降至6后,每天降低1,盐度降到1时,龙虎斑的活动和摄食明显减少,渐变至0时,36 h出现死亡,48 h内全部死亡。     

Effect of Long-Term Low-Salinity Culture on the Survival,Growth, and Nutrient Composition of Mud Crab Scylla paramamosain

This study investigated the effects of long-term low-salinity on the growth performance,proximate composition,amino acid and fatty acid profiles of Scylla paramamosain.The salinity of the low-salinity-culture group(LC)and maintained-salinity-cul-ture group(MC)were set at 5 and 25 respectively.After rearing for 30 d,the survival rate(SR)of the LC group was significantly lower,whereas the average daily molting frequency(ADMF)was significantly higher than those in MC group(P<0.05).There were no significant difference for weight gain rate(WGR)and specific growth rate(SGR)between the two groups.The moisture content of the LC group was slightly higher than the MC group without significant difference.The contents of ash,crude lipid and crude pro-tein in the LC group were lower than those in the MC group,but no significant differences were found except for ash content.A total of 17 free amino acids and 23 fatty acids were identified from the muscle of S.paramamosain.The total amino acids(TAA),essen-tial amino acids(EAA)and essential amino acid index(EAAI)had no significant difference between the two groups.The crabs from LC group had a significantly higher HUFA,including EPA,DHA,ARA.The percentage of n-3 PUFA and the ratio of n-3/n-6 PUFA were significantly higher in the LC group.These results indicated that S.paramamosain rearing at low salinity had significantly de-creased SR;however,the low-salinity environment significantly promoted the accumulation of unsaturated fatty acids(UFAs),espe-cially the n-3 PUFA,which might be related to the osmoregulation mechanism.     

利用量子力学势能数据预测温度、压力、盐度和沉积物孔径对甲烷水合物形成和分解的影响

介绍一个预测不同温度、压力、盐度和沉积物毛细管孔径条件下甲烷水合物 溶液 气体多相平衡模型。该模型以Van der Waals和 Platteeuw热力学模型、量子力学从头算粒子相互作用势能、DMW 92状态方程和Pitzer电解质理论为基础,能在很宽广温压范围内预测温度、压力、盐度和毛细管力对甲烷水合物形成和分解的影响。通过对比本模型的预测结果与实验数据,可知本模型能够准确地预测海水和多孔介质中甲烷水合物的相平衡条件。对于一定盐度下多孔介质中甲烷水合物的形成温压条件的在线计算可浏览: www.geochem model.org/models.htm。     

The role of salinity in fluvio-deltaic morphodynamics: A long-term modelling study

Salinity difference between terrestrial river discharge and oceanic tidal water plays a role in modifying the local flow field and, as a consequence, estuarine morphodynamics. Although widely recognized, recent numerical studies exploring the long-term morphological evolution of river-influenced estuaries with two-dimensional, depth-averaged models have mostly neglected salinity. Using a three-dimensional morphodynamic model, we aim to gain more insight into the effect of salinity on the morphodynamics of fluvio-deltaic systems. Model results indicate that the resultant estuarine morphology established after 600 years differs remarkably when a salinity gradient is included. A fan-shaped river-mouth delta exhibits less seaward expansion and is cut through by narrower channels when salinity is included. The inclusion of salinity tends to generate estuarine circulation, which favours landward sediment transport and hence limits the growth of the delta while enhancing the development of intertidal areas. The formation of deltaic channel–shoal patterns resulting from morphodynamic evolution tends to strengthen salinity stratification, which is characterized by an increased gradient Richardson number. The direction of the depth-averaged residual sediment transport over a tide may be opposite to the direction of residual velocity, indicating the significant influence of baroclinic effects on the net sediment transport direction (and hence morphological change). The effect of salinity on morphological evolution becomes less profound when the strength of tidal or fluvial forcing is dominant over the other. The effects of sediment type and flocculation, which are particularly important when salinity gradients are present, are also discussed. Overall, this study highlights that neglecting salinity to simulate long-term estuarine morphodynamics requires more careful justification, particularly when the environment is characterized by fine sediment types (favouring suspended transport), and relatively large river discharge and estuarine depth (favouring baroclinic effects). © 2020 John Wiley & Sons, Ltd.