基于模糊评价法的洱海稳态阶段分析

稳态转化理论被广泛应用于各种系统的变化,也常常用于描述水生和陆生生态系统状态发生本质、渐进和持续的转变过程。对淡水湖泊生态系统而言,研究其变化过程及驱动因子将有助于理解当前水环境问题的本质特征,为水环境整治与生态修复提供理论支撑。为了确定典型高原湖泊洱海所处的稳态阶段及其转换取向,在野外调查研究及文献资料数据分析的基础上,尝试用模糊评价法分析洱海所处的稳态转换阶段。评价结果表明,洱海1985-2001年处于清水稳态,2002年系统发生跃迁,2003年退化到藻草共存、草藻共存的过渡态。从2009-2010年洱海各阶段的隶属度来看,系统仍有可能转化为藻型浊水稳态,警示对洱海的保护和治理工作不可松懈。在缺乏水生物数据的条件下,模糊评价法可用于稳态转换评价。     

湖泊生态系统稳态转换驱动因子判定方法研究进展

湖泊生态系统会在长期的人为胁迫和短期的强扰动下发生稳态转换,灾变性稳态转换将会导致湖泊水环境在短时间内急剧恶化,进而延缓和加大治理的进程及成本。探求浅水湖泊稳态转换驱动因子是科学合理确定湖泊管理策略的关键所在,现有的驱动因子判定方法主要有实验观测、统计分析和模型模拟。实验观测缺乏对生态系统整体的判断,仅采用观测数据并不能得出导致稳态转换确切的原因和效应;统计分析难以对未来作出预警;模型模拟可有效规避上述2种方法存在的问题,特别是机理模型是今后分析稳态转换的主要方法。有必要加强统计分析与模型模拟的结合、生态模型与传统水质水动力模型耦合等方面的研究工作。     

洱海流域生态-农业系统动态耦合过程分析

以农业面源污染为研究重点,探究兼顾生态与发展职能的流域生态-农业系统的耦合过程与机制,为高原湖泊流域污染治理和生态农业发展提供依据。选择洱海流域为研究对象,运用系统耦合理论,构建系统综合评价模型、系统耦合度测度模型、系统耦合协调模型和系统耦合演化模型,对1994-2015年洱海流域系统耦合度及动态耦合过程进行分析。1994-2015年,洱海流域生态-农业综合发展指数和耦合度均呈上升趋势,经济-生态系统总体向良好状态发展,经济发展对流域生态环境质量的威胁不断弱化,两者协调发展水平维持磨合、提升。1994-2015年洱海流域生态-农业系统耦合协调度为0.46~0.88,经济发展子系统与生态环境子系统总体呈现协调耦合的状态,其中1994-2002年处于拮抗时期,2003-2005年仍然处于拮抗时期但耦合度下降趋势得到扭转,2006-2011年进入磨合阶段,2012-2015年进入高水平耦合阶段但保持与促进难度较大。耦合态势可分为磨合消耗阶段(1994-1998年)、快速消耗阶段(1999-2003年)、快速协调阶段(2004-2007年)和磨合协调阶段(2008-2015年),揭示了生态农业政策的短期效益,预示流域农业面源污染治理的困境。系统耦合测度有效识别了洱海流域生态-农业系统演化阶段与特征,农业生产方式制约着洱海流域生态-农业系统协调耦合,磨合协调阶段下农业面源污染治理需要持续推进。     

长江中游浅水湖泊沉积物碳氮同位素特征及其来源分析

通过分析长江中游湖北地区4个浅水湖泊（鲁湖、花马湖、野潴湖、三山湖）沉积物中的有机碳（TOC）、总氮（TN）、碳氮比（C/N）、碳稳定同位素（δ13C）以及氮稳定同位素（δ15N）,探究藻型湖泊和草型湖泊沉积物间碳、氮稳定同位素组成差异性,并进行了有机污染评价和有机质与氮素来源分析。结果表明,4个浅水湖泊的有机污染严重,鲁湖、花马湖、野潴湖、三山湖的平均有机指数分别为0.86、1.05、0.53和2.71,均达到了有机污染的程度,平均有机氮污染指数分别为0.34、0.36、0.21和0.54,均达到了有机氮污染程度;藻型湖泊（花马湖和鲁湖）沉积物中δ13C和δ15N的变化范围分别为-3.126%～-2.260%和0.291%～0.731%,均值分别为（-2.885±0.275）%（n=10）和（0.486±0.168）%（n=10）;草型湖泊的δ13C、δ15N变化范围分别为-3.048%～-2.494%和0.411%～0.830%,均值分别为（-2.766±0.213）% （n=10）和（0.617±0.183）%（n=10）,藻型湖泊的δ13C要更加偏负,草型湖泊的δ15N更加偏正;利用C/N与δ13C对有机质来源进行定性分析,发现浮游植物的沉积构成了藻型湖泊沉积物有机质的主要成分,而草型湖泊中浮游植物、土壤有机质和维管束植物均有贡献。利用C/N与δ15N对沉积物氮素来源进行半定量分析,发现本研究所选取湖泊的沉积物氮行为与湖泊的草藻形态没有显著相关关系,需更详细的物源信息才可确定氮素来源。     

江蓠与对虾混养的神经-模糊优化模型初探

根据2003年4月~2004年9月在广东省海丰县联安镇江蓠-对虾鱼塭混养试验所得调查数据,采用神经-模糊系统作为非线性逼近工具,建立了虾藻混合养殖过程中各生物和水环境因子之间非线性关系的神经-模糊系统模型。以鱼塭水环境中可溶性无机氮DIN≤0·2mg·L-1作为富营养化限制标准,模型模拟出了对虾不同养殖阶段混养江蓠所需的最低理论生长速率。其结果较好地反映了混养系统中江蓠的实际生长速率对水环境中DIN所产生的影响。     

三角帆蚌对蓝藻的滤食作用及其对沉水植物生长的影响

双壳贝类是淡水生态系统常见的滤食性动物,以浮游植物和有机物悬浮颗粒为食,其作用可能降低蓝藻浓度,从而促进沉水植物生长。通过构建4组（草＋蓝藻、草＋蓝藻＋低生物量蚌、草＋蓝藻＋高生物量蚌、草）室外微型生态系统,研究了湖泊下风区常见蓝藻堆积浓度下,三角帆蚌（Hyriopsis cumingii）的滤食作用对蓝藻水华和沉水植物苦草（Vallisneria natans）生长的影响。结果表明：（1）蓝藻对苦草的生长具有显著抑制作用,草藻组和草组的相对生长率分别为-7.65mg/g·d和7.19mg/g·d;（2）     

高原湖泊流域生态-农业系统动态耦合过程分析

对于具有耦合关系的流域复杂系统，从演化过程、驱动机制和政策效应等方面分析生态-农业耦合效应，是实现流域生态文明的方法论。论文采用系统耦合测度模型，对洱海流域系统耦合度及动态耦合过程进行分析，揭示流域生态文明下洱海流域生态农业政策的效应。结果表明：①生态农业措施对洱海流域生态-农业系统协调耦合产生积极作用。②1994-2015年，洱海流域生态-农业系统耦合度由0.48提升到0.75，接近0.8的协调耦合阈值，表明生态-农业系统由磨合阶段进入高水平耦合阶段。③耦合态势可分为磨合消耗、快速消耗、快速协调与磨合协调四个阶段，既揭示了初期生态农业政策的短期效益，又预示出中远期流域农业面源污染治理的困境。     

磷的不同动态变化对模拟湖泊生态系统中附草螺类的影响

采用试验围隔模拟湖泊富营养化过程,选取磷的不同动态变化,研究其动态输入模式对附草螺类的影响。结果表明,总量相同时,中短期内低频次的磷输入比高频次的磷输入对螺类生物量的影响更显著,而长期条件下高低频次的磷输入对螺类生物量的影响无显著差异(P>0.05)。营养的添加显著促进螺类生物量(密度和丰度)的增长。试验系统中附植藻类的生物量与螺类的生物量成显著负相关(P<0.05),沉水植物刺苦草(Vallisneria spinulosa)与螺类(Radix)生物量的相关性不显著(P>0.05),表明螺类是螺类-附着藻-沉水植物系统的关键调控因子,而沉水植物可能会因生态系统状态的差异而存在不同的响应机制。     

鄱阳湖湖口水位特性及其对水环境的影响

水位作为重要的湖泊水文因子,对湖泊水动力过程、化学过程和生态过程具有重要的影响。根据2007～2008年鄱阳湖湖口水位、水环境实测数据,分析了湖口水位及水体各环境因子的变化特征,阐述了各水环境因子对水位变化的响应,并建立了水位与各水环境因子的回归方程。结果表明:湖口的水位及各水环境因子均呈季节性变化,湖口水位与长江水位(九江站)呈直线正相关;湖口的水位变化对其水体各环境因子均存在明显的影响,其中水体透明度随水位上升而增大,悬浮物、溶解氧、高锰酸盐指数、氮化物和磷化物浓度随水位上升而下降。     

太湖夏季不同类型湖区浮游植物群落结构及环境解释

2010年9月对太湖不同类型湖区31个站点的浮游植物群落结构进行了调查。结果表明,共检测到120种浮游植物,蓝藻门、绿藻门和硅藻门物种占据了相当大的比例。所有站点都有微囊藻出现,微囊藻是草型湖区和藻型湖区的数量单一优势种,导致31个站点的群落多样性指数值都较低。在环境变量的作用下,31个站点被分为3种类型,即草型湖区(组Ⅰ)、藻型湖区(组Ⅱ)和五里湖(组Ⅲ)。草型湖区物种数和多样性指数较高、浮游植物密度和营养盐浓度较低,总磷(TP)浓度极显著低于藻型湖区(t=-3.84,P=0.001)。在一定浓度范围内,微囊藻密度随着悬浮物(SS)浓度的增大而上升。太湖生态修复应以降低水体悬浮物浓度、提高水体透明度为目标,为草型湖泊生态系统的培植创造条件。     

Change in habitat associations and geographic distribution of thorny skate (Amblyraja radiata) in the southern Gulf of St Lawrence: density‐dependent habitat selection or response to environmental change?

We describe changes in the habitat associations and geographic distribution of thorny skate during their feeding season in the southern Gulf of St Lawrence, based on 32 yr of monitoring by a bottom‐trawl survey. In the 1990s, geographic range contracted sharply and distribution shifted into a narrow band of warm deep waters. These changes appeared to reflect altered habitat selection by individual skates, rather than local depletion of the skates that had habitually occupied the vacated areas or a change in the timing of seasonal migrations. Changes in skate distribution coincided with a decline in skate biomass and a cooling of bottom waters. The contraction in the geographic range of skates appeared to be a density‐dependent response, more closely linked to the decline in skate abundance than to the change in environmental conditions. The cause of the shift in habitat associations is less certain. An index of the distribution shift was more strongly correlated with skate biomass than with an index of temperature conditions, and the change in temperature associations is in the direction predicted by density‐dependent bioenergetic considerations. However, the shift into deeper waters is into a depth zone where skate condition is relatively low, contrary to the expectation that fish should be concentrated in optimal habitat at low population size. On the other hand, while the shift into warm deep waters coincided with a cooling of waters at intermediate depths, distribution failed to shift back to the earlier pattern as these waters warmed in the late 1990s.     

Density of juvenile brown trout and Atlantic salmon in natural and man-made riverine habitats

The density of juvenile brown trout (Sulmo trutta L.) and Atlantic salmon (Salmo salar L.) was significantly higher along river bank areas protected against erosion than along natural river banks in the River Gaula, Central Norway. A habitat shift appeared in Atlantic salmon, and a behavioural shift was demonstrated by brown trout from August October. The effect of habitat on densities of juvenile salmonids should be taken into account as mitigation measures on eroded river banks and when assessing fish production in rivers.     

A test for a regime shift

This note describes a formal statistical approach to testing for a regime shift based on population time series for a system of interacting species or groups. Under this approach, a regime shift is said to occur if the system switches abruptly from varying around one locally stable steady state to varying around another. This allows the problem to be formulated as testing for a changepoint in a vector autoregressive process. The test is illustrated using data from the North Sea covering the period 1963–97.     

Links between the recruitment success of northern European hake (Merluccius merluccius L.) and a regime shift on the NE Atlantic continental shelf

The distribution of northern European hake (Merluccius merluccius L.) extends from the Bay of Biscay up to Norwegian waters. However, despite its wide geographical distribution, there have been few studies on fluctuations in the European hake populations. Marine ecosystem shifts have been investigated worldwide and their influence on trophic levels has been studied, from top predator fish populations down to planktonic prey species, but there is little information on the effect of atmosphere–ocean shifts on European hake. This work analyses hake recruitment success (recruits per adult biomass) in relation to environmental changes over the period 1978–2006 in order to determine whether the regime shift identified in several abiotic and biotic variables in the North Sea also affected the Northeast Atlantic shelf oceanography. Hake recruitment success as well as parameters such as the sea surface temperature, wind patterns and copepod abundance changed significantly at the end of the 1980s, demonstrating an ecological regime shift in the Northeast Atlantic. Despite the low reproductive biomass recorded during the last decades, hake recruitment success has been higher since the change in 1989/90. The higher productivity may have sustained the population despite the intense fishing pressure; copepod abundance, warmer water temperatures and moderate eastward transport were found to be beneficial. In conclusion, in 1988/89 the Northeast Atlantic environment shifted to a favourable regime for northern hake production. This study supports the hypothesis that the hydro‐climatic regime shift that affected the North Sea in the late 1980s may have influenced a wider region, such as the Northeast Atlantic.     

Effect of wind stress on the catch of Japanese anchovy Engraulis japonicus off northwestern Kyushu, Japan

Effect of wind stress on the annual catch of Japanese anchovy Engraulis japonicus off northwestern Kyushu for the period between 1963 and 2009 was investigated. Regime shift analysis detected several step changes in catch and environmental variables. Since the mid-1980s, the anchovy catch in the coastal fishery zones has declined, while the catch in the offshore zone has increased. The decline of catch in the coastal zones showed a significant correlation with the long-term variations in prevailing north-northeastward wind stress over the Goto-Nada Sea during spring spawning season. The results indicated that weakened north-northeastward winds caused the recent low recruitment of anchovy through low levels of wind-induced eggs and larval transport from the offshore spawning ground to the coastal nursery areas, resulting in the potential shift of nursery area to the northwestern offshore region. Thus, as well as the growth-favorable ambient temperature, transport process would play a key role on long-term fluctuations in anchovy abundance in these coastal seas.     

The shift to smaller zooplankton in Lake Victoria cannot be attributed to the ‘sardine’ Rastrineobola argentea (Cyprinidae)

After the population increase of introduced Nile perch (Lates niloticus) in Lake Victoria, a decrease in the relative abundance of herbivorous cladocerans and calanoids was reported for the pelagic zone. The shift from large herbivores to small-bodied predatory cyclopoids has been attributed to the increase of the zooplanktivorous cyprinid dagaa (Rastrineobola argentea), which rose concomitantly with the Nile perch. However, we observed that in the Mwanza Gulf of the lake cyclopoids dominated the zooplankton community already before the rise of dagaa. Furthermore, there are indications that dagaa takes fewer calanoids than expected from their representation in the environment, although a slight preference for cladocerans may exist. Calanoids dominated the diet of small Nile perch of about 4 cm length, but juvenile Nile perch did not occur in the study area until after the size shift in zooplankton. The lumped biomass of dagaa and small Nile perch is lower than the biomass of the original haplochromine-dominated community of zooplanktivorous fish. Thus, the decline of large zooplankters in the lake cannot be explained by intensified predation after the replacement of zooplanktivorous haplochromines by dagaa and Nile perch. Increased eutrophication, resulting in a shift in predominance from diatoms to cyanophytes, is suggested as an alternative explanation for the shift in zooplankton composition.     

Variation in the distribution of ocean shrimp (Pandalus jordani) recruits: links with coastal upwelling and climate change

In this analysis, an atypical northward shift in the distribution of age‐1 ocean shrimp (Pandalus jordani) recruits off Oregon in 2000 and 2002–2004 was linked to anomolously strong coastal upwelling winds off southern Oregon (42°N latitude) in April–July of the year of larval release (t?1). This is the first clear evidence that strong upwelling winds can depress local recruitment of ocean shrimp. Regression analysis confirmed a long‐term negative correlation between log_e of ocean shrimp recruitment and April sea level height (SLH) at Crescent City, California, in the year of larval release, for both northern and southern Oregon waters. The regional pattern of ocean shrimp catches and seasonal upwelling winds showed that, although the timing of the spring transition as reflected in April SLH drives ocean shrimp recruitment success off Oregon generally, the strength and consistency of spring upwelling limits the distribution of large concentrations of ocean shrimp at the southern end of the northern California/Oregon/Washington area. A northward shift in 1999 and 2001–03 in the northern edge of this ‘zone of maximum upwelling’ is the likely cause of the weak southern Oregon recruitment and resulting atypical distribution of ocean shrimp observed off Oregon in 2000 and 2002–04, with a return to a more typical catch distribution as spring upwelling moderated in subsequent years. It is noted that a northward shift in the conditions that produce strong and steady spring upwelling winds is consistent with many predictions of global climate models under conditions of global warming.     

Tanner crab Chionocetes bairdi Rathbun haemocyte classification and an evaluation of using differential counts to measure infection with a fungal disease

Abstract. The circulating haemocytes of the tanner crab, Chionocetes bairdi , were studied and classified as hyalinocytes, intermediate granulocytes and eosinophilic granulocytes. Differential haemocyte counts of normal crabs and crabs infected with an apparently pathogenic unnamed ascomycete fungus revealed a shift in the hyalinocyte-granulocyte ratio in infected crabs. There was a highly significant increase in the percentage of granulocytes and a corresponding decrease in hyalinocytes in infected crabs. This shift was thought to be caused by a marked increase in the relative number of eosinophilic gianulocytes. There was also a highly significant statistical relationship between the severity of the internal fungus infection, established by histopathological analysis of the major organ systems, and the increased number of circulating eosinophilic granulocytes. The results of the study indicate that differential haemocyte counts may be a valuable tool in monitoring the health of C. bairdi populations.     

Diet shift of larval and juvenile landlocked Ryukyu-ayu <Emphasis Type="Italic">Plecoglossus altivelis ryukyuensis</Emphasis> in the Fukuji Reservoir,Okinawa Island,Japan

ABSTRACT:   The diet shift of larval and juvenile Ryukyu-ayu Plecoglossus altivelis ryukyuensis was investigated for the landlocked population stocked in the Fukuji Reservoir, Okinawa Island. Gut contents of 274 specimens (5.1–31.4 mm in body length) including 31 yolk-sac larvae (5.7–8.0 mm) were examined. The diet of larval and juvenile landlocked P. a. ryukyuensis was mainly composed of zooplankton such as dinoflagellates, rotifers, copepods, and cladocerans. Feeding incidence was 48% in total and it gradually increased with growth. Diet analysis clearly demonstrated a diet shift during the larval and juvenile periods. For yolk-sac larvae and 5.0–19.9 mm fish, the diet was dominated by dinoflagellates Gymnodinium sp., and Peridinium sp., both numerically and by frequency, followed by rotifers that mainly consisted of Polyarthra spp. Diet breadth (Levin's standardized index B_A) diversified with growth, and feeding on copepods and cladocerans gradually increased in 10.0–14.9 mm fish. Diet overlap (Morisita's index: C) showed that diet drastically changed in 20.0–24.9 mm fish with a specialization on cladocerans Bosminopsis deitersi and Diaphanosoma brachyurum . This diet shift probably corresponded with an increase of feeding ability resulting from an enlargement of the mouth, increased swimming ability, and the development of sense organs.     

Species range shifts along multistressor mosaics in estuarine environments under future climate

Range shifts are a key mechanism that species employ in response to climate change. Increasing global temperatures are driving species redistributions to cooler areas along three main spatial axes: increasing latitudes, altitudes and water depths. Climate‐mediated range shift theory focuses on temperature as the primary ecological driver, but global change alters other environmental factors as well, and these rarely work in isolation. Ecosystems are often characterized as mosaics of overlapping environmental stressors, resulting in temporal and spatial heterogeneity which differs between stable, low complexity mosaics (e.g. open ocean) and highly variable, highly complex mosaic environments (e.g. estuaries). We propose a multistressor mosaic of climate‐mediated species range shift across abiotic environmental gradients, typical for mobile species (e.g. fish) in variable coastal environments. We conceptualize how climate‐driven changes in salinity, temperature, dissolved oxygen and pH can drive redistribution of estuarine species in a future world. Non‐thermal drivers are a critical component of species range shifts and when not considered, underestimate the impact of global change on species populations and ecosystem services.