南沙渚碧礁生态系营养关系的稳定碳同位素研究

利用稳定碳同位素分析技术研究了南沙渚碧礁生态系食物网主要生物类群之间的营养关系。结果表明，生物的稳定碳同位素组成与其营养来源有密切关系。浮游植物的δ^13C为-18.3‰，与其所处海域的环境条件一致，浮游动物的δ^13C值变化较大，范围为-20.4‰～-10.9‰,表明可能存在浮游植物和碎屑两种营养来源。珊瑚和砗磲的碳同位素组成（-17‰～-15‰）与浮游动物相差较大，暗示共生虫黄藻可能在这些珊瑚的营养来源中起重要作用。底栖海参（-9.6‰)和蜘蛛螺（-12.5‰)的碳同位不比组成与它们沉积物食性的营养特征吻合。鱼类的δ^13C值变化范围较大（-17.7‰～-10.9‰），未表现出随营养级升高而增大的趋势，说明影响鱼类碳同位素组成的因素比较复杂。     

Long‐term nutrient enrichment alters nematode trophic structure and body size in a Spartina alterniflora salt marsh

The effects of long‐term experimental nutrient enrichment on nematode trophic guilds and morphometrics were examined in intertidal saltmarsh creeks of Plum Island Estuary, Massachusetts, USA. Nematodes from the marsh‐edge Spartina alterniflora habitat in a reference creek (n = 3300) were sampled annually and compared with nematodes (n = 3100) from a creek in which nitrate and phosphate loading rates were increased approximately 10–15× for 6 years. Trophic guilds in both creeks were dominated by epistrate (diatom) feeders and predators, and natural temporal variability across years was high. However, after 4 years of nutrient enrichment, a shift in the nutrient‐enriched creek was detected from a dominance of epistrate feeders to an increased proportion of predators, even though neither the benthic microalgae biomass nor the total density of nematodes was affected by fertilization. Nematodes also became longer, and longer relative to their diameter over time with nutrient enrichment because of the shift in trophic structure as short‐stout epistrate feeders were replaced with longer, more slender predators. These changes may have been directly related to nutrient enrichment effects on benthic algae or indirectly to the many other effects of enrichments on ecosystem structure or function. Our research indicates that nutrient enrichment alters the nematode community and this alternation may directly or indirectly affect the response of benthic algae to nutrient enrichment and as well as other ecosystem services.     

Diatomeenstratigraphische Untersuchungen zur Trophieänderung und Industrieschlammakkumulation im Traunsee/Österreich

Three cores from Traunsee were investigated and compared with respect to diatom stratigraphy concerning dating of incursions into and rate of accumulation of industrial tailings in the profundal zone.

     

Ecological succession, palaeoenvironmental change, and depositional sequences of Barremian–Aptian shallow-water carbonates in northern Oman

Abstract Barremian and Aptian shallow‐water carbonate facies (uppermost Lekhwair, Kharaib and Shuaiba Formations) are described from outcrops in northern Oman. Based on facies analysis and bedding pattern, three orders of depositional sequences are defined (third to fifth order) and correlated between sections. Over the course of three third‐order sequences, covering the Barremian to Lower Aptian, a third‐order depositional pattern is documented that consists of a succession of three distinct faunal assemblages: discoidal orbitolinids and calcareous algae were deposited during early transgression; microbialites and microencrusters dominate the late transgressive to early highstand facies; and a rudist‐ and miliolid‐dominated facies is typical of the highstand. This ecological succession was controlled largely by palaeoenvironmental changes, such as trophic level and clay influx, rather than sedimentological factors controlled by variations in accommodation space. Orbitolinid beds and carbonates formed by microbialites and microencrusters seem to be the shallow‐water carbonate response to global changes affecting Late Barremian to Aptian palaeoclimate and palaeoceanography.     

南海大眼金枪鱼(Thunnus obesus)摄食生态研究

根据2011年12月—2013年2月于我国南海海域采用金枪鱼延绳钓以及灯光罩网调查捕获的大眼金枪鱼(Thunnusobesus)的各项基础生物学以及胃含物的数据,对其摄食生态进行了分析研究。结果表明:(1)南海海域大眼金枪鱼的食物组成包括鸢乌贼、帆蜥鱼、金色小沙丁鱼、飞鱼、竹荚鱼、鲐鱼、小公鱼属、圆鲹属以及不可辨别的鱼类与虾类,其主要饵料生物为鸢乌贼(%IRI=45.21),其次为金色小沙丁鱼(%IRI=21.36)和帆蜥鱼(%IRI=13.72);(2)空胃率与平均饱满指数随季节变化明显,空胃率在春季时会达到顶峰(37.9%),秋季时最低(16.7%),呈先下降后上升趋势,同时平均饱满指数也在春季达到最高值(0.33),随季节下降并稳定于0.1,空胃率随性腺成熟度的提高有明显上升趋势,平均饱满度指数在性成熟度Ⅰ期与Ⅵ期均呈现高值(1.18、1.04);(3) Shannon-Weiner多样性指数H′和Pielou均匀度指数J随季节变化呈现出明显的变化,Shannon-Weiner多样性指数H′随叉长组基本在1.52—1.72之间变化, Pielou均匀度指数J随性腺成熟度的提高有逐步下降的趋势;(4)营养长度(NR)较高,说明其摄食的饵料成分多、氮来源较复杂,基础食物来源(CR)和生态位总空间(TA)的冬季指标值近乎夏季指标的两倍;通过δ15N稳定同位素法计算大眼金枪鱼的平均营养级为4.73。总体上,南海海域大眼金枪鱼主要以头足类和鱼类为食,其摄食习性与季节和个体发育相关,在食物链中处于较高营养位置。     

Food and feeding habits of Octopus insularis in the Veracruz Reef System National Park and confirmation of its presence in the southwest Gulf of Mexico

Octopuses are active predators that feed on a wide range of prey including crustaceans, fishes, and mollusks. They are important components of coral reef systems and support local and artisanal fisheries in the Gulf of México. Octopus insularis has been found to be one of the most relevant components in catches from the coral reef system of Veracruz in the southwestern Gulf of Mexico, and its role in the ecosystem requires assessment. To corroborate the morphological identification of O. insularis, six octopuses were identified by genetic methods. And to understand the trophic relationships between this octopus species and its prey, 394 octopuses caught during 2016 and 2017 by an artisanal fleet were sampled and their stomach contents analyzed. Results showed that crustaceans are the most frequently consumed group, with the genera Mithraculus and Etisus being the most important in the diet. Fishes, bivalves, and gastropods were identified as uncommon prey items in the diet. Their presence in the stomachs could be related to the movement of this octopus outside of the coral reef. Considering that our samples were of medium‐ and large‐sized individuals, cannibalism could be discarded for O. insularis in this size range in the Veracruz reef system. These findings suggest a generalist and opportunistic predation of O. insularis on the most abundant and available prey in the study area, namely the crustaceans. These represents an effective transfer of biomass from the low trophic levels to top predators in the coral reef system.     

长江口邻近海域浮游植物粒级结构特征及其与环境的响应关系

浮游植物的分粒级研究是监测浮游植物特征的重要工具,对于深入了解浮游植物动态的作用也不容忽视。本文的研究目的在于揭示长江口邻近海域春秋季不同粒级的浮游植物分布动态,分析浮游植物粒级结构与环境因素以及浮游动物群落结构的关系。通过2010年春季和秋季对粒径分级叶绿素a浓度的现场调查研究发现：春季,浮游植物主要以微型浮游植物占优势;秋季,微微型浮游植物和微型浮游植物共同占优势。相关分析结果表明,温度和富营养化状况是影响微型和微微型浮游植物对总叶绿素a贡献的重要因素。浮游动物的摄食压力可能对小型浮游植物对总叶绿素a的贡献起着重要的作用。     

丹江口水库的饵料生物资源及水体营养状态评价

根据1992年12月至1993年9月的调查,丹江口水库的饵料生物资源量为1．845×10~6t．其产鱼潜力为1．615×10~4t．是现有鱼产量（包括捕捞产量和不投饵网箱产量）的5倍左右．就水体营养状态而言,汉江库区为中营养型,丹江库区属贫一中营养型．文中还对丹江口水库的渔业发展和水质保护进行了讨论．     

Spatial and seasonal variations in the ecological characteristics of the free-living nematode assemblages in a large microtidal estuary

This study has determined the ways in which the density, number of species, species composition and trophic structure of free-living nematode assemblages in the subtidal waters of a large southern hemisphere microtidal estuary change spatially and seasonally, and has explored whether those four biotic characteristics are related to certain environmental factors. Based on data derived from samples collected seasonally at 12 sites throughout the estuary, the densities and number of species of nematodes decreased progressively with distance from estuary mouth, to reach a minimum at sites where salinities were most variable, and then increased slightly in the uppermost part of the estuary where salinities were least. Densities were also generally greatest in spring, due largely to increases in the abundance of epistrate-grazing species at this time and thus when the amount of primary food (microphytobenthos) peaked. The spatial distribution of the composition of the nematode assemblages was closely correlated with salinity and, to a lesser extent, grain-size composition and amount of particulate organic material (%POM) in the sediment. Although species composition changed sequentially along the estuary, the change was particularly pronounced between sites above and below the area where salinities started to decline markedly and become more variable and %POM increased markedly. This reflected, in particular, far greater abundances of Spirinia parasitifera at the six downstream sites and of Theristus sp. 1 at the six sites further upstream. Species composition underwent pronounced seasonal cyclical changes at all sites, presumably reflecting interspecific differences in the timing of peak reproduction and thus of recruitment. The trophic structure of the nematode assemblages changed both spatially and temporally in relation to the relative abundance of different food sources. Thus, for example, non-selective deposit feeders, such as Theristus sp. 1, dominated samples in the upper estuary, where %POM was by far the greatest, and was rare or absent at downstream sites. Conversely, epistrate grazers, such as species of the Chromadoridae, were most abundant at downstream sites in spring, when the density of the microphytobenthos reached its maximum.