2020年冬季大亚湾西南海域主要渔业生物碳氮稳定同位素研究

为了解大亚湾西南海域食物网的营养结构特征, 本研究于2020年1月份使用底拖网采集了该海域的渔业生物, 并分析了35种主要渔业生物的碳氮稳定同位素值。根据δ¹³C和δ¹⁵N值, 计算出该海域食物网6种营养结构的生态指标和主要渔业生物的营养级, 并绘制了连续营养谱。本次调查渔业生物主要为鱼类和虾蟹类, 鱼类的δ¹³C和δ¹⁵N值范围分别为-17.63‰ ~ -14.85‰和12.92‰~15.46‰, 平均值分别为-16.47‰和13.80‰; 虾蟹类的δ¹³C和δ¹⁵N值范围分别为-17.67‰ ~ -15.51‰和11.05‰~12.62‰, 平均值分别为-16.30‰和11.85‰。根据δ¹⁵N值, 用相加模型(trophic position by the additive model, TPA)和缩比模型(trophic position by the scaled model, TPS)分别计算了主要渔业生物的营养级, 结果显示两个模型计算的结果无显著性差异(P>0.1), 呈现鱼类平均营养级>虾蟹类的趋势。本研究发现大亚湾西南海域食物网初始食物来源较为单一, 存在食物链营养层级较少和长度不足, 食物网营养级多样性较低和营养结构冗余程度高的现象。与30多年前相比, 大亚湾近年高营养级生物量减少, 食物网结构由复杂趋向简单化, 生态系统稳定性较差。本研究结果不仅为了解大亚湾食物网结构组成提供了基础资料, 也为保护大亚湾渔业资源, 维持生态系统结构的稳定性提供参考依据。     

西洞庭湖天然和人工改造湿地中克氏原螯虾(Procambarus clarkii)与日本沼虾(Macrobrachium nipponense)的食性差异

栖息地退化和外来物种入侵都是淡水生态系统中的主要威胁因素,因此,量化不同人类活动干扰强度下外来入侵生物和本土生物的食性组成差异,对于明确种间竞争强度,制定适合的管理对策至关重要.本研究应用碳、氮稳定同位素分析技术,比较了长江中下游西洞庭湖湿地受人类活动干扰程度不同的天然湿地和人工改造湿地中的入侵种克氏原螯虾(Procambarus clarkii)与本土种日本沼虾(Macrobrachium nipponense)的食性组成及差异.2017年8月8-18日在西洞庭湖区不同人类干扰强度的栖息地中采集了两种消费者和5种潜在食物来源样品,共计91个.测定碳氮稳定同位素含量后,使用贝叶斯混合模型,估算不同食物来源对消费者的贡献.研究发现:在两种栖息地中克氏原螯虾与日本沼虾食性均有重叠,且在改造湿地中重叠度更大.与克氏原螯虾相比,日本沼虾消费更多的动物性食物.与天然湿地相比,在改造湿地中由于克氏原螯虾数量更多,与本土种竞争食物资源,克氏原螯虾和日本沼虾δ¹³ C比值都显著升高,食性组成均发生了变化,植物性食物来源比重增加.由于食性改变,在改造湿地中仅日本沼虾δ¹⁵ N比值显著下降,克氏原螯虾在两种栖息地中δ¹⁵ N比值无显著变化.本研究证明,随着人类干扰强度增大,受干扰湿地中外来入侵生物对本土生物的影响增大.     

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.

     

珠江流域西江支流贺江浮游藻类群落特征及水质分析

为了解珠江流域西江支流贺江浮游藻类的分布并评价其水质情况,于2013年丰水期和枯水期对贺江的浮游藻类群落结构进行调查和分析,结果表明:调查期间共检出浮游藻类7门130种,其中丰水期7门63种,枯水期5门103种,浮游藻类群落组成以绿藻门、硅藻门和蓝藻门为主,丰水期绿藻门居多,硅藻门次之,藻细胞丰度平均值为2.13×106cells/L;枯水期硅藻门最多,藻细胞丰度平均值为3.71×106cells/L;优势种主要有水华微囊藻、卷曲鱼腥藻、小颤藻、啮蚀隐藻、短小舟形藻、变异直链藻、颗粒直链藻、四尾栅藻、集星藻、小球衣藻和小球藻.RDA分析表明,影响贺江浮游藻类群落分布的主要环境因子是氮、磷营养盐,综合营养状态指数显示贺江处于中营养水平.     

水生高等植物-浮游植物关系和湖泊营养状态

本文根据中国一些湖泊的资料,从湖泊营养化角度分析了水生高等植物的生物量,分布和优势种以及浮游植物,透明度和湖泊营养状态的关系,表明高等植物和浮游藻类这两种初级生产者的生产在浅水湖泊中呈负相关,并反映在水质指标和湖泊营养状态下,同是,简要讨论了光限制,营养供给和生化抑制作用在浮游植物与水生高等植物关系中的作用。     

2004年夏季台湾海峡上升流海域悬浮颗粒物粒径谱分析

利用2004年夏季台湾海峡南部海域的现场激光粒度仪剖面测量数据,运用海洋食物链的粒径谱理论,分析了悬浮颗粒物的Sheldon谱图和正态化谱图的剖面分布精细结构。横跨台湾海峡沿岸及浅滩外斜上升流的A和B两断面Sheldon粒径谱类型相近,正态化谱图的斜率r的范围从-0.79到-0.65,在明显高于寡营养海域的水平上波动。斜率r的高值带或高变幅带,在上升流系高叶绿素带及叶绿素最大层的周边或前端的呈斑状分布。海洋食物链的粒径谱分析结果支持关于台湾海峡南部上升流生态系高生产力、短食物链和高营养转换效率的宏观认识,并深化对营养转换效率分布精细结构的了解。现场激光粒度仪可发展为探索海洋食物链时空分布精细结构的常备传感器。     

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.     

Stable isotope analysis of consumer food webs indicates ecosystem recovery following prolonged drought in a subtropical estuarine lake

Assessing changes in food-web structure provides a useful monitoring tool for gauging the resilience of ecosystems in the face of climatic impacts. We consider the ecological resilience of a large estuarine lake (St Lucia Estuary, South Africa) in the wake of an extreme climatic event (prolonged drought). Using carbon and nitrogen stable isotopes, food-web structure was assessed at five sites across the estuary during the winter and spring of 2013. Sampling occurred approximately three years after heavy rains flooded the system and returned it to a relatively diluted state following an almost decade-long drought that decimated food webs in the upper parts of the estuary due to hypersalinity effects. Comparisons of niche width and variance of consumer food webs among sites revealed a general homogenisation of food webs across the entire system, contrasting with the spatial differentiation of food webs documented during the drought phase. Our results indicate that the estuary is able to maintain ecological resilience at the whole-system level in the face of an extreme drought. This is likely facilitated by source pools of species residing in the relatively stable lower estuary, which are able to rapidly recolonise areas denuded by drought in the upper estuary.