Trophic field overlap: A new approach to quantify keystone species

It is a current challenge to better understand the relative importance of species in ecosystems, and the network perspective is able to offer quantitative tools for this. It is plausible to assume, in general, that well-linked species, being key interactors, are also more important for the community. Recently a number of methods have been suggested for quantifying the network position of species in ecological networks (like the topological importance metric, TI). Most of them are based on node centrality indices and it may happen that the two most important species in a food web have very similar interaction structure and they can essentially replace each other if one becomes extinct. For conservation considerations it is a challenge to identify species that are richly connected and, at the same time, have a relatively unique and irreplaceable interaction pattern. We present a new method and illustrate our approach by using the Kuosheng Bay trophic network in Taiwan. The new method is based on the interaction matrix, where the strength of the interaction between nodes i and j depends only on topology. By defining a threshold separating weak and strong interactors, we define the effective range of interactions for each graph node. If the overlaps between pairs of these ranges are quantified, we gain a metric expressing how unique is the interaction pattern of a focal node (TO). The combination of centrality (TI) and uniqueness (TO) is called topological functionality (TF). We compare the nodal importance rank provided by this metric to others based on a variety of centrality measures. The main conclusion is that shrimps seem to have the most unique interaction pattern despite that their structural importance has been underestimated by all conventional centrality indices. Also, our network analysis suggests that fisheries disturb the ecosystem in a more critical network position than the impingement by the local power plant.     

赤潮多发区深圳湾叶绿素a的时空分布及其影响因素

于2008年2月至2008年11月分四个季度调查了赤潮多发区深圳湾叶绿素a的时空分布,并分析了叶绿素a与主要环境因子之间的关系.结果表明,深圳湾叶绿素a质量浓度范围为3.07～309.94 mg·m~(-3),年平均值为42.29 mg·m~(-3).四季叶绿素a平均质量浓度由高到低排列分别为:春季(108.33 mg·m~(-3))>夏季(35.2 mg·m~(-3))>秋季(16.68 mg·m~(-3))>冬季(8.96 mg·m~(-3)).叶绿素a的质量浓度在冬季和春季呈现由湾内向湾外递减的分布特征,而夏季和秋季呈现由西岸向东岸递减的分布特征,整体则呈现由湾内向湾外递减的分布特征.相关分析显示深圳湾叶绿素a与水温、COD、TOC、PO_4~(3-)-P和浮游植物密度因子显著正相关,与DIN因子极显著正相关,说明叶绿素a与水温、DIN、PO_4~(3-)-P、COD、TOC和浮游植物密度之间有着比其它因子更为密切的关系.以叶绿素a作为富营养化评价标准,发现深圳湾海域富营养化严重,存在随时爆发赤潮的潜在风险.     

厦门西港近岸沉积物重金属污染历史及源解析

分析厦门西港潮间带柱状沉积物中14种重金属元素(Sc、V、Cr、Co、Ni、Cu、Zn、Sr、Cd、Sb、Tl、Pb、Fe和Hg)的垂向分布特征、污染历史和污染来源.结果表明, 1795年之前,多数重金属元素含量变化趋势较平稳;1795~1849年间,Sc、Cr、Co、Ni、Cu、Sr、Cd、Tl、Pb和Hg含量有明显增加;2001~2011年间,Sc、Cr、Co、Sr、Tl、Pb和Hg含量又有增加趋势.多元统计分析结果表明,沉积柱中重金属元素主要有3大来源:交通和工业活动、自然源、工业和生活污水排放,贡献率分别是72.87%、12.20%和10.99%.柱状沉积物中铅同位素示踪分析表明,铅同位素组成从底层至表层由工业活动及污水排放逐步向机动车尾气排放漂移,厦门西港近岸海域中铅污染主要受交通和工业活动、工业和生活污水排放的影响.     

Sources and spatial distribution of polycyclic aromatic hydrocarbons in coastal sediments of the Basque Country (Bay of Biscay)

This contribution characterises the sources and distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments of the Basque coast (Bay of Biscay). Different source characterisation approaches (i.e. GIS assisted-chemometrics, PAH diagnostic ratios and analyses of composition profiles) were used in combination to successfully identify the factors determining the origin and distribution of PAHs. Urban/industrial combustion processes were identified as the main PAH source. However, the analysis of PAH composition patterns and diagnostic ratios identified secondary natural and petrogenic PAH sources on small spatial scales. The median ∑18PAH concentration ranged from 66 μg kg^?1 (d.w.) to 7021 μg kg^?1 (d.w.). The Ibaizabal estuary, which supports most of the anthropogenic pressure in the region (i.e. urban development, industrialisation, commercial and recreational harbours), also showed the highest PAH concentrations. On the shelf, human activities, hydrodynamic conditions and geomorphological features led to spatial differences in the PAH concentrations among sectors: the offshore and west sectors were characterised by higher concentrations, while the lowest values were found in the mid and east sectors. The results enhance the knowledge on PAH-related contamination processes and could be used to support the environmental assessment process required under current European marine legislation.     

厦门湾空气质量对新冠疫情管控的响应

通过对厦门湾城市群在COVID-19封锁前后6周内（2020-01-11~2020-02-21）的空气污染物浓度变化进行分析,以确定影响本区域空气质量的主要人为污染源.在春节假期与封锁叠加期间,SO₂、NO₂、CO、PM₁₀和PM_2.5浓度相比于节前1周的下降幅度分别为6%~22%、53%~70%、34%~48%、47%~64%和53%~60%,而O₃浓度变化没有一致的规律性;与2018~2019年历史同期相比,PM_2.5、PM₁₀、CO和NO₂的下降幅度更大,但SO₂的下降幅度相当;在复工复产后,NO₂的反弹幅度最大（38%~138%）,远高于SO₂（2%~42%）,显示交通源相对于固定源更易受到疫情管控的影响;春节后风速增大和降水增多也为SO₂、NO₂和PM的下降提供了正向影响.利用反距离插值权重法,得到管控前后厦门湾城市群不同污染物的空间分布变化特征,显示NO₂浓度高值区的变化与交通源高度相关,CO和SO₂空间分布特征保持稳定,复工后PM_2.5和PM₁₀在人口与路网密集区变化不明显,而在工地相对集中区域有明显上升,O₃空间分布的低值区与NO₂的高值区具有较好的空间匹配性,显示NO₂对O₃滴定作用明显,可为进一步O₃污染减排措施的制定提供参考.     

基于数值模拟的海湾环境容量价值损失的预测评估 ——以厦门同安湾围填海为例

基于海湾环境容量价值影响因素的分析,采用环境经济学的影子工程法,结合水动力数值模型及其与污染物扩散的耦合模型,建立了围填海导致的海湾环境容量价值损失的预测评估模型和方法,并以厦门同安湾为例,对同安湾4个围填海规划方案可能造成的环境容量价值的损失进行了预测评估.结果表明,方案1~方案4围填海面积依次为1.98,7.73,9.38,19.24km2,围填海造成的环境容量的损失依次为12281.3,48418.6,60706.6,132800.1万元/a,单位面积的损失依次为62.03,62.64,64.72,69.02元/(m2×a).围填海活动带来的环境成本不容忽视.基于评估结果,针对厦门围填海的现状提出了相关的政策建议.     

象山港海洋病毒时空分布特征及其环境影响因素

分别于2007年的7月(夏季)、11月(秋季)与2008年的1月(冬季)、4月(春季)采集样品,研究了象山港海域的水样(表层海水和上覆水)中的浮游病毒及沉积物中的底层病毒丰度的时空分布特征,并采用主成分分析及多元逐步回归分析方法研究了影响浮游病毒丰度时空分布的主要因素,结果表明,调查期间象山港海域表层海水、上覆水及沉积物样品中浮游(底层)病毒丰度实测值的变化范围为6.48×104~1.01×108cells/mL,均值分别为1.55×107,1.03×108,1.13×108cells/mL.季节分布特征为秋季 > 夏季 > 春季 > 冬季.病毒丰度垂直分布表现为上覆水均大于表层海水;平面分布均为从港底到港口递减、养殖区高于非养殖区、电厂附近海域出现较高值的趋势.近岸人类活动的陆源污染及水产养殖污染是造成此空间分布特征的主要原因.溶解氧、水温及叶绿素a是制约表层海水浮游病毒丰度的主要影响因素;营养盐含量及浮游细菌丰度是制约上覆水中浮游病毒丰度的主要影响因素,沉积物中的病毒丰度与细菌丰度具有显著正相关性(P < 0.01).     

大鹏湾环境容量研究Ⅰ:自净能力模拟分析

在估算大鹏湾污染源强及统计海水污染物浓度的基础上,采用三维水动力模型及污染物扩散模型,模拟了大鹏湾的海水交换及污染物扩散过程,分析了大鹏湾海水交换与生化降解对自净能力的贡献.结果表明,大鹏湾潮差小,约为1m,潮流弱,污染物难于向湾外扩散,其物理自净能力差,湾内海水自净主要取决于生化降解.在吐露港海区与沙头角海区,污染排放较大,水深较小,海水难于交换,容易受到污染.     

Monitoring, modeling, and management impacts of bivalve filter feeders in the oligohaline and tidal fresh regions of the Chesapeake Bay system

Populations of bivalve filter feeders are distributed throughout the oligohaline waters of the Chesapeake Bay system and, to a lesser extent, in tidal fresh waters as well. Previous studies indicate these bivalves significantly diminish phytoplankton concentrations in one major tributary, the Potomac River, and observed chlorophyll concentrations suggest bivalve influence on phytoplankton in other oligohaline reaches. We incorporated a model of these bivalves into an existing eutrophication model of the system. The model indicated that bivalves may reduce phytoplankton concentrations in oligohaline and tidal fresh waters throughout the system but the most significant effects were noted in the Potomac and Patuxent tributaries. Bivalve impacts were related to hydraulic residence time. The greatest phytoplankton reductions occurred in the regions with the longest residence time. Model carbon and nutrient budgets indicated bivalves removed 14% to 40% of the carbon load, 11% to 23% of the nitrogen load, and 37% to 84% of the phosphorus load to the regions where their impact on computed chlorophyll was greatest.     

深圳湾海域营养盐的时空分布及潜在性富营养化程度评价

根据深圳湾海域2008年2、5、8、11月4个航次的海水中营养盐监测数据,分析了深圳湾海域海水中营养盐的时空分布特征,应用Si：N：P比及潜在性富营养化评价模式对整个海域水质富营养化程度进行了评价。结果表明：深圳湾海域氮磷营养盐污染严重,劣于四类海水水质标准;且受珠江口水系夏季带来的高氮低磷低硅的海水的影响,整个深圳湾海水中氮磷硅营养盐的时空分布不尽相同：夏季DIN的分布由湾口向湾内逐渐降低;冬、春、秋3季DIN的分布和4个季节PO43--P、SiO32--Si的分布都是由湾内向湾口逐渐降低;受陆源输入的影响,秋季DIN和PO43--P表现出由西岸向东岸逐渐降低的趋势;受海底沉积物交换的影响,夏季SiO32--Si表现出由西岸向东岸逐渐升高的分布趋势。冬季整个海域都处于氮限制状态,基本无赤潮发生风险;春季整个海域基本处于富营养状态,是赤潮的高发期;夏季整个海域从湾内到湾口由氮限制逐渐过渡到磷限制状态,处于赤潮发生的危险期;秋季整个海域处于轻微的磷限制状态,也是深圳湾赤潮的高发期,但危险性较春季有所降低。