Mass balanced and dynamic simulations of trophic models of kelp ecosystems near the Mejillones Peninsula of northern Chile (SE Pacific): Comparative network structure and assessment of harvest strategies

Mass balanced trophic models for kelp ecosystems which include subsystems dominated by Macrocystis integrifolia, Lessonia trabeculata and areas of barren ground (BG) were constructed for subtidal areas near the Mejillones Peninsula (SE Pacific), Chile. Information on biomass, P/B ratios, catches, food spectrum, consumption and dynamics of commercial and non-commercial populations was obtained and examined using Ecopath with Ecosim software analyses. The biomass of blades of L. trabeculata and M. integrifolia represented the compartments most relevant to the subsystems studied. Within the herbivores, the sea urchin Tetrapigus niger was dominant, followed by the snails Turritella sp. and Tegula sp. The fishes Pinguipes chilensis and Cheilodactylus variegatus were the dominant predators, followed by the asteroids Heliaster helianthus and Meyenaster gelatinosus. The highest system throughput (72,512 g wet weight m⁻² year⁻¹) was calculated for the subsystem dominated by M. integrifolia. The mean trophic level of the catch ranged from 1.1 (subsystem dominated by L. trabeculata) to 1.3 (subsystem dominated by M. integrifolia) to 3.2 (barren ground subsystem), showing that harvesting in each system was concentrated either on primary producers (blades of kelp species) or top predator fishes. Although the values for the Relative Ascendency (A/C) fluctuated from 36.5 to 45%, suggesting that all the systems were immature, the subsystem dominated by M. integrifolia emerged as the least resistant to external disturbances (e.g. fisheries). This result agreed with the high value of the system recovery time (SRT) for the M. integrifolia subsystem as a response to combined fisheries scenarios. The results obtained using mixed trophic impact (MTI) and Ecosim [increasing the fishing mortality F_i by 4×] showed that in most of the cases the predictions had the same qualitative tendencies. One of the most important results obtained in this study was that exploitation of kelp blades as an alternative strategy to harvesting the whole plants appeared to be ecologically sustainable, since harvesting the blades propagated only small effects on the entire subsystem. The fish P. chilensis may be considered as a top predator species with a strong top-down control since an increase in its fishing mortality in the subsystem dominated by M. integrifolia produced a high SRT value, and the F_MSY was less than the originally entered F_i in Ecopath. Based on the results obtained, it was concluded that the trophic mass balanced models and simulated management scenarios offered good possibilities for the planning of interventions and manipulations or the planning of more sustainable management strategies in highly disturbed natural systems.     

Critically evaluating best management practices for preventing freshwater turtle extinctions

Ex situ conservation tools, such as captive breeding for reintroduction, are considered a last resort to recover threatened or endangered species, but they may also help reduce anthropogenic threats where it is difficult or impossible to address them directly. Headstarting, or captive rearing of eggs or neonate animals for subsequent release into the wild, is controversial because it treats only a symptom of a larger conservation problem; however, it may provide a mechanism to address multiple threats, particularly near population centers. We conducted a population viability analysis of Australia's most widespread freshwater turtle, Chelodina longicollis, to determine the effect of adult roadkill (death by collision with motor vehicles), which is increasing, and reduced recruitment through nest predation from introduced European red foxes (Vulpes vulpes). We also modeled management scenarios to test the effectiveness of headstarting, fox management, and measures to reduce mortality on roads. Only scenarios with headstarting from source populations eliminated all risks of extinction and allowed population growth. Small increases in adult mortality (2%) had the greatest effect on population growth and extinction risk. Where threats simultaneously affected other life‐history stages (e.g., recruitment), eliminating harvest pressures on adult females alone did not eliminate the risk of population extinction. In our models, one source population could supply enough hatchlings annually to supplement 25 other similar‐sized populations such that extinction was avoided. Based on our results, we believe headstarting should be a primary tool for managing freshwater turtles for which threats affect multiple life‐history stages. We advocate the creation of source populations for managing freshwater turtles that are greatly threatened at multiple life‐history stages, such as depredation of eggs by invasive species and adult mortality via roadkill.     

洱海入湖河口湿地干湿季沉积物氮、磷、有机质垂向分布特征及污染风险差异性

以云南洱海罗时江河口湿地为典型对象,利用柱状底泥分层采样器采集罗时江河口湿地表层(0~10 cm)、中层(10~30 cm)和底层(30~60 cm)沉积物样品,分析干、湿季沉积物总氮(TN)、总磷(TP)、有机质(OM)垂向分布特征,并对沉积物进行污染风险评价.结果表明:1干季罗时江河口湿地表层、中层和底层沉积物TN平均含量分别为1.734、1.453和1.255g·kg~(-1),TP平均值分别1.085、1.034和0.992 g·kg~(-1),OM平均值分别为59.051、47.730和42.133 g·kg~(-1);湿季罗时江河口湿地表层、中层和底层沉积物TN平均含量分别为1.147、0.948和0.895 g·kg~(-1),TP平均值分别0.599、0.523和0.519g·kg~(-1),OM平均值分别为53.098、46.897和43.395 g·kg~(-1);干、湿季各指标含量垂向分布随沉积深度的增加呈下降趋势,表层富集明显;三层沉积物各指标含量均为干季高于湿季,且除OM外,TN和TP均达到显著差异(P0.01).2单因子指数(PI)、有机氮指数(ON)和有机指数(OI)评价结果表明,整体上干季沉积物氮磷属于重度污染,有机质属于中度污染;湿季沉积物氮和有机质均为中度污染,磷为轻度污染;总体上沉积物氮、磷、有机质污染水平为干季高于湿季,且干、湿季各污染指数均为表层最高,中层次之,底层最低,表层污染最为严重.3干、湿季罗时江河口湿地污染来源存在差异,干季以外源为主,湿季以内源为主;干季沉积物营养盐潜在释放风险较湿季大,且以表层释放风险最大.     

普者黑岩溶湿地干湿季沉积物氮、磷、有机质分布及污染风险评价

探究典型岩溶湿地沉积物营养物质的污染状况及其富营养化风险,以期为岩溶湿地水-沉积物污染的控制与治理提供参考和依据.以典型岩溶流域普者黑为研究区,运用抓斗式底泥采样器对流域内河流湿地、湖泊湿地、沼泽湿地和库塘湿地的表层沉积物进行采样,并采用国家标准方法对沉积物中总氮（TN）、总磷（TP）及有机质（OM）的含量进行测定,并运用单因子指数法、有机指数法及有机氮指数法对普者黑岩溶流域不同类型湿地沉积物的污染程度进行评价.结果表明：①在干季,河流湿地TP含量最高,为1.18 g·kg^-1,沼泽湿地TN和OM含量最高,分别为2.93、2.71 g·kg^-1;库塘湿地TN、TP和OM含量最低,分别为1.44、0.63、1.43 g·kg^-1.在湿季,河流湿地TP和OM含量最高,分别为0.95、2.16 g·kg^-1,湖泊湿地TN含量最高,为2.22 g·kg^-1;沼泽湿地TP和OM含量最低,分别为0.42、1.28 g·kg^-1,库塘湿地TN含量最低,为1.22 g·kg^-1.②普者黑不同类型湿地沉积物TN、TP、OM在干、湿季下的污染程度不同.在干季,河流湿地和沼泽湿地沉积物磷污染均为重度污染,4种湿地沉积物氮污染均为重度污染,有机污染除库塘湿地属于轻度污染外,其他3种湿地均为中度污染.在湿季,河流湿地沉积物磷污染为重度污染,河流湿地和湖泊湿地沉积物氮污染均为重度污染,湖泊湿地沉积物有机污染属于重度污染.总体上看,各类湿地沉积物氮磷污染干季的污染程度比湿季严重,干季以外源为主,湿季以内源为主;故干季湿地沉积物营养盐潜在释放风险较湿季大.     

寒冷地区流域水污染防治问题

我国寒冷地区河流冰封期最长可达180天,其间水体自净功能差,加之城镇污水处理水平低于全国平均水平,工业点源污染负荷沉重,流域水污染问题显得格外突出,水环境压力巨大.因此,有针对性地解决寒冷地区流域水环境问题已经成为协调资源供求、经济发展与环境保护的核心问题.通过分析寒冷地区流域水污染特点及成因,提出了建立流域水污染防治...     

大连海域入海污染源中PFASs的赋存、输入通量和季节特征

本文对大连海域入海河流和入海排污口中19种PFASs和2种PFOS新型替代品Cl-PFESAs进行了分析,估算其入海通量,并分析了季节变化特征.结果表明,研究区域入海河流中总PFASs的含量范围为9. 85～757 ng·L~(-1)(浓度中位数为74. 7 ng·L~(-1)),与国内外其他河流相比,大连海域入海河流中总PFASs的含量处于中等或较低水平;入海排污口中总PFASs的含量范围为9. 19～801 ng·L~(-1)(浓度中位数为29. 5 ng·L~(-1)).入海河流和入海排污口中PFASs的主要贡献要素为PFOS和PFOA,其中入海河流、市政污水和污水处理厂出水中总PFASs含量未发现明显的季节差异特征,但工业废水中冬季含量显著高于夏季.计算结果显示,大连海域总PFASs入海通量约123 g·d~(-1)(44. 7 kg·a~(-1)),入海河流和入海排污口的贡献相当.全氟/多氟醚类磺酸化合物(Cl-PFESAs)检出率较低,其中8∶2Cl-PFESA均为检出.     

鄱阳湖流域多尺度C、N输送通量及其水质参数变化特征

本文选取鄱阳湖流域内从初级支流到最大干流再到湖区(香溪→架竹河→赣江→鄱阳湖)这一联通水系线路为研究对象,通过对丰水期和枯水期内各级河流对应流域及鄱阳湖湖区内水体中的各形态C、N浓度进行监测,计算各级河流间C、N元素运移通量,探讨鄱阳湖流域水体C、N迁移过程机制和水质参数变化特征,为鄱阳湖流域生态系统的综合健康管理提供科学依据.结果表明:(1)鄱阳湖通江流域的C、N浓度呈明显季节变化,其中TIC、TOC、TC浓度丰水期较高,而NO_3~--N和DTN浓度枯水期较高.丰水期TC增加的主要原因是TIC增加,丰水期TN主要以非溶解态存在,而枯水期TN主要以DTN中的NO_3~--N形式存在.(2)鄱阳湖通江流域的C、N输出通量呈明显季节变化,其中香溪各形态C丰水期通量较枯水期小,架竹河、赣江各形态C丰水期通量较枯水期大,香溪、架竹河、赣江流域各形态N在丰水期通量大多较枯水期小,各形态C、N通量与径流量在99%的置信水平上呈极显著正相关关系.(3)鄱阳湖流域水体参数丰水期COND、TDS、pH小于枯水期,丰水期ORP大于枯水期.     

HYDROLOGIC EFFECTS OF CLEARCUTTING AND STRIPCUTTING LOBLOLLY PINE IN THE COASTAL PLAIN1

ABSTRACT: Harvesting 29-year-old loblolly pine (Pinus taeda L.) plantations on six small catchments in the Coastal Plain of west Tennessee caused variable but generally minor increases of storm-flow volumes during the four years following harvest. The increases were primarily associated with decreases of rainfall interception rather than with soil disturbance. Harvesting had no effect on stormflow volumes in six nearby catchments of 37-year-old loblolly pine to which the same treatments were applied. Postharvest increases of flow-weighted sediment concentrations averaged higher for the catchments with greater flows at both locations. During the fourth through eighth years after harvest, average sediment concentrations for harvested catchments at each location approximated closely the base rate of 62 mg L^-1 previously defined for undisturbed pine types. Thus, relatively minor postharvest increases of stormflow volumes in the six 29-year-old plantations and increases of sediment concentrations in all 12 catchments were limited to about four years. Nevertheless, because of potential channel erosion, the findings confirm the need to extend stream management zones well up into drainages with intermittent and ephemeral flows wherever water quality is a concern. Despite certain undesirable effects of logging (baring of mineral soil, decreased weight and depth of forest floor, increased soil bulk density), the results demonstrate the high resilience developed by pine planted on severely eroded sites in the southern Coastal Plain.     

基于CMAQ的大气环境容量计算方法及控制策略

利用空气质量模型CMAQ建立了真实条件下基于不同达标率的大气环境容量计算方法,为大气环境质量管理提供了科学依据。采用CMAQ建立研究区域的空气质量模型系统,设置多层嵌套网格(最小网格分辨率3km),获得了2006年1月、4月、7月、10月(四季代表月)的小时污染物浓度值。通过调整研究区域的污染源排放量,并结合空气质量监测数据和环境空气质量标准,建立了不同污染物的达标率与环境容量关系曲线。研究证明,该方法可以确定可吸入颗粒污染物、二氧化硫和二氧化氮在不同达标率下的大气环境容量,并充分反映三种污染物环境容量的季节性变化特征。研究结果不仅有利于环境管理者制定针对研究区域的空气总量控制方案,还有助于构想基于季节性变化的污染控制策略。     

Hybrid economy research in remote Indigenous Australia: seeing and supporting the customary in community food economies

Hybrid economy research in remote Indigenous Australia is what Gibson-Graham [2008. Diverse economies: performative practices for “other worlds”. Progress in Human Geography, 32 (5), 613–632] describe as a performative ontological project. This research seeks to address the marginalisation of customary economic activities that contribute to the well-being of Indigenous Australians. It aims to make the customary sector more real, more credible and more viable as an object of policy and activism, challenging the dual dominance of the state and the market as the focus of development (cf. Gibson-Graham 2008 Gibson-Graham, J. K. 2008. Diverse economies: performative practices for “other worlds”. Progress in Human Geography, 32(5), 613–632. doi: 10.1177/0309132508090821[Crossref], [Web of Science ®] , [Google Scholar]). This paper outlines how hybrid economy research has sought to broaden views of the economic landscape in remote Indigenous Australia amid the withdrawal of key policy and programmatic support by the Australian Government. This research draws on Canadian national surveys of Indigenous peoples, harvest studies and programmatic support for customary harvest – hunting, fishing and gathering of bush foods – to identify ways in which the Australian Government might better see and support Indigenous community food economies.