南海东北部末次冰期以来沉积环境演变

利用南海东北部上陆坡处所取的D孔(21°23′02″N,116°47′13″E,水深405m)进行硅藻分析,结合粒度分析与碎屑矿物分析结果,探讨该海域末次冰期以来沉积环境演变过程。结果表明:粒度与硅藻分析结果较为吻合,共同显示D孔可分为上下两层,上层(0-2cm)的砂质沉积层为经冰后期海进过程改造的晚更新世残留沉积层;下层(2-130cm)主要是末次冰期形成的浅海沉积。整个柱样可反映出海洋同位素MIS4期海退至MIS3期海进与MIS2期海退至冰后期海进的沉积韵律。     

Distribution patterns of benthic juvenile gobies in and around seagrass habitats: effectiveness of seagrass shelter against predators

The significance of a sheltering effect of seagrass against predators influencing the distribution patterns of benthic juveniles of the streaked goby Acentrogobius sp. was investigated by field experimentation in and around seagrass habitats at Moroiso and Aburatsubo Bays, Miura Peninsula, Japan. In the former bay, juveniles were always restricted to the seagrass bed, whereas at the latter, they also occurred over the surrounding bare sand substrate. Juveniles never occurred inside predator-exclusion cages over unvegetated sand in Moroiso Bay. Additionally, a tethering experiment resulted in similarly small numbers of juveniles being preyed upon in both the seagrass bed and over bare sand, suggesting that the predation risk for juveniles may not differ between the habitat types and was thus not responsible for their distribution patterns. The availability of symbiotic shrimp burrows, which were scarce in bare sand in Moroiso Bay but abundant in a similar area in Aburatsubo Bay, was also hypothesized as a determinant of distribution pattern. In a manipulative experiment at Aburatsubo Bay, however, juveniles showed no response to alterations in the availability of symbiotic shrimp burrows, indicating that neither the sheltering effect of seagrass against predators nor the availability of symbiotic shrimp burrows was a significant factor in streaked goby juvenile distribution. Food availability may be a determinant, because food abundance patterns were concordant with the juvenile distribution pattern.     

长江口海域春季浮游植物的年际变化

于2014年5月在长江口海域采集海水样品,分析了浮游植物种类组成、细胞丰度、优势种等群落结构特征。共鉴定浮游植物105种,其中硅藻30属56种,甲藻19属41种,以及隶属于金藻、蓝藻等的8个种。浮游硅藻以近岸半咸水种为主,优势种类是中肋骨条藻(Skeletonema costatum);浮游甲藻以沿岸广布种为主,典型代表是东海原甲藻(Prorocentrum donghaiense)。为了更好地了解长江口海域浮游植物的年际变化趋势,本文收集整理了该海域1986—2014年间的春季数据,分析了浮游硅藻、浮游甲藻主要群落特征的年际变化,以及浮游硅藻优势种类细胞粒径的变化趋势。结果表明:(1)浮游硅藻、浮游甲藻的种类数均呈现不同程度的上升趋势,浮游甲藻的上升幅度更为明显;(2)浮游甲藻种类数在浮游植物种类数中的占有比例呈上升趋势,而浮游硅藻所占比例呈下降趋势;(3)浮游硅藻优势种类的细胞粒径呈现小型化趋势。     

Off‐reef planktivorous reef fishes respond positively to decadal‐scale no‐take marine reserve protection and negatively to benthic habitat change

The effects of no‐take marine reserve (NTMR) protection and changes in benthic habitat on fusiliers (family Caesionidae) were investigated at four small Philippine offshore islands on time scales of 10–31 years. Fusiliers are highly mobile, schooling, medium‐sized planktivorous fish that generally feed “off‐reef.” For these reasons, and given the small size of the NTMRs (3.6–37.5 ha) in this study, it was predicted that fusilier density would be unlikely to show clear effects of NTMR protection, or to respond to changes in benthic habitat. In contrast to predictions, clear NTMR effects were observed on fusilier density at three of the four NTMRs, with durations of protection from 14 to 31 years. Furthermore, the study provided strong evidence that benthic variables, specifically cover of live hard coral and dead substratum, affect the density of fusiliers. This effect of benthic habitat on density was highlighted by several major environmental disturbances that caused shifts in the benthic habitat from live hard coral to dead substratum. For two of the three most abundant species of fusiliers individually, and for all three of them combined (Pterocaesio pisang + Caesio caerulaurea + Pterocaesio digramma/tessellata), as live hard coral cover decreased, fish density decreased. It is hypothesized that these “off‐reef” daytime feeders may have such a strong association with live hard coral cover because they use this habitat as nocturnal sleeping sites. Multivariate analyses indicated that, across all sites and times sampled, cover of live hard coral and dead substratum accounted for 38% of the variation in fish assemblage structure. These results are important as there are very few reports in the published literature of strong effects of NTMR protection or changes in benthic habitat on the density and assemblage structure of fusiliers.     

冲绳海槽表层沉积硅藻对黑潮流的响应

本文报道了冲绳海槽表层沉积物中优势硅藻种的相对含量、热带远洋种和硅藻组合的分布特征 ,讨论了热带远洋种的相对含量与黑潮流、硅藻组合的分布与物质来源的关系等问题 .结果表明 ,热带远洋种的相对含量 >2 0 %的界线与黑潮流的边界基本上一致 ;优势硅藻种和硅藻组合的分布留下了与物质来源的关系较为密切的记录 .     

Benthic Communities of the lnfralittoral in the N. Sporades (Aegean Sea): a Variety of Biotopes Encountered and Analysed

Abstract. The infralittoral benthos was studied on three islands of the Northern Sporades in the Aegean Sea. Thirteen stations were sampled on both hard and soft substrata and 408 taxa were identified, some of zoogeographical interest. Multivariate statistical methods such as classification, ordination and Similarilies Terms Analysis were combined with existing ecological information to delineate the various communities present and to point to the indicator species characterising them. The communities were then defined using the indicator species and their affinities to typical biocoenoses. The main factor responsible for the observed distribution proved to be the type of substratum (algal cover or sediment type), which reflects the light and hydrodynamic conditions. The observed bathynietric zonation was similar lo that of the Balearic Islands in the western Mediterranean.     

南海晚第四纪的硅藻遗体及其地质意义Ⅶ.方格罗氏藻

方格罗氏藻[Roperia tesselata(Roper)Grunow]的壳面外形和壳缘构造多样，笔者在南海晚第四纪的三个柱状样沉积物中都采到，统计1303个壳体。分析结果表明：在冰期的沉积物中，壳面呈圆形，壳缘平滑无齿状隆起线的壳体占绝对多数；在间冰期的沉积物中，壳面呈卵形，少数近圆形，壳缘具齿状隆起线的壳体明显增多。因此，该种壳面的两类不同形状和构造的数量差异，可应用于探讨南海晚第四纪古气侯旋回。     

The early Matuyama Diatom Maximum off SW Africa: a conceptual model

An important discovery during Ocean Drilling Program Leg 175, when investigating the record of upwelling off Namibia, was the finding of a distinct Late Pliocene diatom maximum spanning the lower half of the Matuyama reversed polarity chron (MDM, Matuyama Diatom Maximum) and centered around 2.6–2.0 Ma. This maximum was observed at all sites off southwestern Africa between 20°S and 30°S, and is most strongly represented in sediments of Site 1084, off Lüderitz, Namibia. The MDM is characterized by high biogenic opal content, high numbers of diatom valves, and a diatom flora rich in Southern Ocean representatives (with Thalassiothrix antarctica forming diatom mats) as well as coastal upwelling components. Before MDM time, diatoms are rare until ca. 3.6 Ma. After the MDM, in the Pleistocene, the composition of the diatom flora points to increased importance of coastal upwelling toward the present, but is accompanied by a general decrease in opal and diatom deposition. Here we present a simple conceptual model as a first step in formalizing a possible forcing mechanism responsible for the record of opal deposition in the upwelling system off Namibia. The model takes into account Southern Ocean oceanography, and a link with deepwater circulation and deepwater nutrient chemistry which, in turn, are coupled to the evolution of North Atlantic Deep Water (NADW). The model proposes that between the MDM and the Mid-Pleistocene climate revolution, opal deposition off Namibia is not directly tied to glacial–interglacial fluctuations (as seen in the global δ¹⁸O record), but that, instead, a strong deepwater link exists with increased NADW production (as seen in the deepwater δ¹³C record) accounting for higher supply of silicate to the thermocline waters that feed the upwelling process. The opal record of Site 1084 shows affinity to eccentricity on the 400-kyr scale but not for the 100-kyr scale. This points toward long-term geologic processes for delivery of silica to the ocean.     

Use of Cell-Specific PAM-Fluorometry to Characterize Host Shading in the Epiphytic Dinoflagellate Gambierdiscus toxicus

Abstract. Cell‐specific fluorescence characteristics were used to characterize the light tolerance of the toxic benthic dinoflagellate Gambierdiscus toxicus. The fluorescence parameter F_v : F_m was measured using pulse amplitude modulation (PAM) fluorometry on individual cells collected from foliose red algae growing in the sub‐tidal margin of South Water Cay, Belize. Samples were collected over several days during sunny and cloudy conditions and compared to samples incubated in situ. The data from individual cells were used to generate both F_v : F_m frequency histograms and averages. Maximum individual cell values of F_v : F_m reached 0.81 in pre‐dawn samples, a value near the theoretical maximum for PAM fluorometry. In field samples from macroalgal hosts, average F_v : F_m values declined only slightly during the day, but cells incubated in bottles under 47 % incident sunlight showed a significant mid‐day depression. In freshly collected samples, near‐maximum F_v : F_m values could be found in individual cells during the entire day; however, the frequency histograms indicated a greater range in F_v : F_m values during the afternoon than in the morning. In contrast, cultures of G. toxicus showed a tight distribution around a mean. Field samples showed a rapid recovery to near‐maximum F_v : F_m within 2 min when assayed using a standardized actinic light series. Similar results were obtained in laboratory cultures of G. toxicus grown at 73 µmol photons · m^‐2 · s^‐1, but not at 383 µmol photons · m^‐2 · s^‐1. These data provide empirical support for suggestions that G. toxicus exploits the three‐dimensional structure of the algal host thallus to minimize light exposure. This strategy permits G. toxicus, a high‐light intolerant species in culture, to thrive in shallow, well‐lit tropical seas. It may also partially explain the observed preference of G. toxicus for complex, foliose macroalgae as hosts.