湖泊生态系统弹性系数理论及其应用

在湖泊生态系统健康评价的基础上,分析城市湖泊营养状态的特殊性,论证得出响应型和非响应型湖泊的生态系统健康指数(EHI)与营养状态指数(TSI)近似呈二次函数关系.提出湖泊生态系统弹性系数,对生态系统健康指数(EHI)做出适当改进.改进后的生态系统健康指数(EHI′)能够更好地反映各类型湖泊的健康状态,完善了Xu等的EHI理论并扩展了其应用范围,是目前最为接近Costanza对HI定义的可量化计算的数学公式和方法,并成功用于厦门杏林湾生态系统健康评价.     

Distribution and production ofChironomus salinarius (Diptera: Chironomidae) in a shallow coastal lagoon in the Bay of Cádiz

The abundance, generation time and production ofChironomus salinarius larvae in a lagoon fish-pond system in the Bay of Cádiz were studied by taking monthly samples at 3 sites during 1991 and 1992. Numerical abundance and biomass of larvae showed considerable spatial, seasonal and interannual variation (ANCOVAs,P<0.001). The maximum mean annual density was 7048 larvae m^–2, and corresponded to a biomass of 3.08 g dry weight (DW) m^–2. It was recorded at the site with the lowest rate of water renewal. Seasonal patterns were similar at all sites, with main annual peaks of abundance and biomass in autumn-early winter. Chironomid density was positively related to the biomass of benthic macroalgae (P<0.001). The population studied was multivoltine with a probable average of five generations per year, with overlapping cohorts and a predominance of third- and fourth-instar larvae. Estimates of annual production ranged between 72.2 g DW m^–2 yr^–1 at the site with the lowest rate of water renewal in 1991 and 0.1 g DW m^–2 yr^–1 at the site with the highest rate of water renewal in 1992. Mean annual production and the production/biomass ratio for the system was estimated to be 16.8 g DW m^–2 yr^–1 and 12.7, respectively. Possible factors leading to the observed density fluctuations are discussed, as well as possible sources of error in production estimates.     

不同风浪条件下太湖梅梁湾光合有效辐射的衰减

基于2003年7月12～17日在太湖梅梁湾进行的连续6d原位水下光场观测资料,分析了不同风浪条件下光合有效辐射(PAR)的衰减和真光层深度,探讨了影响水下光合有效辐射的主导因子.结果表明,整个观测期间向下PAR衰减系数为2.63～4.71·m^-1(均值为3.63±0.47·m^-1),对应的真光层深度为0.98～1.75m(均值为1.29±0.18m),显示1.5m以下深度浮游植物、沉水植物基本上无法获取足够的太阳光能进行光合作用.从小风浪到中风浪、大风浪向下PAR衰减系数分别是2.63、3.72和4.37·m^-1,衰减系数分别增加了41%、66%.透明度、PAR衰减系数、真光层深度与悬浮物浓度存在显著性线性相关,并且与悬浮物中无机颗粒物相关性最好,而与叶绿素a、脱镁叶绿素及溶解性有机碳相关性很低.多元逐步线性回归表明,叶绿素a和溶解性有机碳最先被剔除方程,说明在梅梁湾由于风浪扰动引起悬浮物浓度的改变是影响水下光场的主导因素.     

Variable responses within epiphytic and benthic microalgal communities to nutrient enrichment

We evaluated how changes in nutrient supply altered the composition of epiphytic and benthic microalgal communities in a Thalassia testudinum (turtle grass) bed in Florida Bay. We established study plots at four sites in the bay and added nitrogen (N) and phosphorus (P) to the sediments in a factorial design. After 18, 24, and 30 months of fertilization we measured the pigment concentrations in the epiphytic and benthic microalgal assemblages using high performance liquid chromatography. Overall, the epiphytic assemblage was P-limited in the eastern portion of the bay, but each phototrophic group displayed unique spatial and temporal responses to N and P addition. Epiphytic chlorophyll a, an indicator of total microalgal load, and epiphytic fucoxanthin, an indicator of diatoms, increased in response to P addition at one eastern bay site, decreased at another eastern bay site, and were not affected by P or N addition at two western bay sites. Epiphytic zeaxanthin, an indicator of the cyanobacterial/coralline red algae complex, and epiphytic chlorophyll b, an indicator of green algae, generally increased in response to P addition at both eastern bay sites but did not respond to P or N addition in the western bay. Benthic chlorophyll a, chlorophyll b, fucoxanthin, and zeaxanthin showed complex responses to N and P addition in the eastern bay, suggesting that the benthic assemblage is limited by both N and P. Benthic assemblages in the western bay were variable over time and displayed few responses to N or P addition. The contrasting nutrient limitation patterns between the epiphytic and benthic communities in the eastern bay suggest that altering nutrient input to the bay, as might occur during Everglades restoration, can shift microalgal community structure, which may subsequently alter food web support for upper trophic levels.     

渤海湾两株H2亚型禽流感病毒的 遗传进化分析

野鸟是禽流感病毒的自然储存库,病毒可以随着宿主的迁徙传播给其他野鸟与家禽。渤海湾是鸟类南北迁徙的重要停歇地,也是东亚-澳大利西亚鸟类迁徙通道的重要组成部分,每年有大量水鸟在渤海湾停歇,促进了禽流感病毒的传播。为了解渤海湾地区禽流感病毒的传播及进化与水鸟迁徙的相关性,2018年春季鸟类迁徙期间的4和5月份,在渤海湾采集鸻鹬类粪便样品2 120份,对样品进行检测,分离出2株H2亚型禽流感病毒。对这2株H2亚型禽流感病毒进行了分子特征及遗传进化分析,并结合渤海湾水鸟的环志回收数据,对H2亚型病毒的重组及遗传进化与水鸟迁徙的联系进行了分析。结果表明,2株分离株的HA蛋白裂解位点符合低致病性禽流感病毒的分子特征,它们的8个基因片段同源性均不高,其中879-H2N7的8个基因片段分别与我国福建和澳大利亚的毒株同源性最高,遗传关系最近;854-H2N8的8个基因片段分别与我国湖南以及日本、韩国、孟加拉国和越南的毒株同源性最高,遗传关系最近。渤海湾水鸟的环志回收数据分析表明,879-H2N7随着野鸟的迁徙在渤海湾、福建沿海和澳大利亚之间进行传播与扩散;854-H2N8可能跨越东亚-澳大利西亚和中亚-印度两条通道之间进行基因重组和进化,并会随着鸟类迁徙进行传播和扩散。     

杭州湾滨海湿地3种草本植物叶片N、P化学计量学的季节变化

动态平衡理论是生态化学计量学的理论基础, 各种有机体是否存在一个固定的化学计量比是生态学研究的热点问题。该文研究了杭州湾滨海湿地3种优势物种海三棱藨草(Scirpus mariqueter)、糙叶薹草(Carex scabrifolia)和芦苇(Phragmites australis)叶片N、P生态化学计量特征的季节变化。结果发现, 3种植物叶片N含量范围分别是7.41-17.12、7.47-13.15和6.03-18.09 mg·g^-1, 平均值(±标准差)分别为(11.69 ± 2.66)、(10.17 ± 1.53)和(11.56 ± 3.19) mg·g^-1; 叶片P范围分别是0.34-2.60、0.41-1.10和0.35-2.04 mg·g^-1, 平均值为(0.93 ± 0.62)、(0.74 ± 0.23)和(0.82 ± 0.53) mg·g^-1; N:P范围分别是7.19-30.63、11.58-16.81和8.62-21.86, 平均值为16.83 ± 8.31、14.53 ± 3.91和16.49 ± 5.51, 可见不同植物其生态化学计量值范围存在一定差异, 但经方差分析发现3种草本植物间生长季节内N、P元素含量差异并不显著(p > 0.05)。各物种叶片N、P含量均表现出在生长初期显著大于其他生长季节(p < 0.05), 生长旺季(6、7月)随着叶片生物量的持续增加, N、P含量逐渐降低并达到最小值, 随后8-9月叶片不再生长而N、P含量逐渐回升, 在10月叶片衰老时N、P含量再次下降; 叶片N:P则在生长初期较小, 在生长旺季先升高后降低, 随后叶片成熟不再生长时又逐渐增加并趋于稳定。     

The role of Steller sea lions in a large population decline of harbor seals

We provide the first direct evidence that Steller sea lions will prey on harbor seals. Direct observations of predation on marine mammals at sea are rare, but when observed rates of predation are extrapolated, predation mortality may be found to be significant. From 1992 to 2002, harbor seals in Glacier Bay declined steeply, from 6,200 to 2,500 (∼65%). After documenting that Steller sea lions were preying on seals in Glacier Bay, we investigated increased predation by sea lions as a potential explanation for the large decline. In five independent data sets spanning 21–25 yr and including 14,308 d of observations, 13 predation events were recorded. We conducted a fine-scale analysis for an intensively studied haul-out (Spider Island) and a broader analysis of all of Glacier Bay. At Spider Island, estimated predation by sea lions increased and could account for the entirety of annual pup production in 5 of 8 yr since 1995. The predation rate, however, was not proportional to the number of predators. Predation by Steller sea lions is a new source of mortality that contributed to the seal declines; however, life history modeling indicates that it is unlikely that sea lion predation is the sole factor responsible for the large declines.     

Toxic activity from cultures of Karlodinium micrum (=Gyrodinium galatheanum) (Dinophyceae)—a dinoflagellate associated with fish mortalities in an estuarine aquaculture facility

The goal of this study was to test for, and partially characterize, toxic activity associated with the dinoflagellate Karlodinium micrum. Since 1996, three fish kill events associated with blooms of K. micrum have occurred at HyRock Fish Farm, an estuarine pond aquaculture facility raising hybrid striped bass on the Chesapeake Bay, MD, USA. Using an assay based on the lysis of rainbow trout erythrocytes, cultures of a Chesapeake Bay isolate of K. micrum have been shown to produce toxic substances which are released upon cell disturbance or damage. The LC₅₀ for hemolysis of a sonicated cell suspension was 2.4×10⁴ cells ml⁻¹, well within the range of cell concentrations observed associated with fish kills. The toxic activity from K. micrum cells and culture filtrates was traced to two distinct fractions that co-elute with polar lipids. The LC₅₀ for hemolysis of the larger of these two fractions (Tox A) was 284 ng ml⁻¹ while the LC₅₀ of the second, smaller, fraction (Tox B) was 600 ng ml⁻¹. For comparison, the LC₅₀ for the standard hemolysin saponin was 3203 ng ml⁻¹. At concentrations of 800 and 2000 ng ml⁻¹, respectively, Tox A was further shown to be ichthyotoxic to zebrafish (Danio rerio) larvae (80% mortality), and cytotoxic to a mammalian GH(4)C(1) cell line (100% LDH release). At a concentration of 600 ng ml⁻¹ Tox B was shown to be cytotoxic to a mammalian GH(4)C(1) cell line (>30% LDH release), but not ichthyotoxic to zebrafish (D. rerio) larvae up to a concentration of 250 ng ml⁻¹. Although treatment with either algicidal copper or potassium permanganate caused significant lysis of K. micrum cells (>70%), toxic activity was released after treatment with copper and eliminated following treatment with potassium permanganate. This observation in cultures is consistent with observations made at HyRock Fish Farm where significantly higher mortality was observed following treatment of a K. micrum bloom with copper sulfate compared to treatment with potassium permanganate. This study represents the first direct evidence of the toxicity of K. micrum isolated from the Chesapeake Bay.     

Naltrexone prevents footshock-induced performance deficit in rats

Three experiments demonstrate that inescapable footshock delivered to unrestrained rats produces analgesia as well as performance deficits in subsequent one-way shuttle acquisition. Both the performance and the antinociceptive effects are prevented by pretreatment with as little as 0.1 mg/kg i.p. of the opiate antagonist, naltrexone. These studies suggest that both effects are mediated through opiate receptors with similar underlying naltrexone pharmacodynamics.     

Determinants of preferred intertidal feeding habitat for Eastern Curlew: A study at two spatial scales

Abstract Broadscale habitat use by Eastern Curlews (Numenius madagascariensis) in their non‐breeding range in eastern Australia was assessed using low tide surveys on feeding grounds, where 60 skilled volunteers made repeated counts of the birds on intertidal flats, across 41% (9500 ha) of the intertidal habitat within Moreton Bay, Australia. We analysed 32 defined sections of intertidal flat, of roughly equal area (mostly 200–400 ha), which varied greatly in their curlew density (2–47 birds per 100 ha) and also in substrate and other environmental features. Sites with the least resistant substrates had densities three times those with the most resistant substrates. Of 10 environmental characteristics measured for each site, substrate resistance was the best predictor of curlew density (r² = 0.45). Characteristics that were poor predictors included distance to the nearest roost, level of human disturbance and distance to urban settlement. For a finer‐scale assessment, microhabitat use and feeding behaviour were recorded during low tide within 12 intertidal flats, which varied in size (23–97 ha), substrate, topography and other features. Across all flats, curlews strongly preferred to feed relatively close (0–50 m) to the low‐water line. They fed on a variety of substrates (including sand, sandy‐mud, mud and seagrass) in broadly similar proportions to their occurrence in the habitat. There was a statistically significant preference for sand, although its magnitude was not strong. These results indicate that curlews select habitat most strongly at a between‐flat rather than within‐flat scale.