Negligible effect of hypolimnetic oxygenation on the trophic state of Lake Jyväsjärvi,Finland

Hypolimnetic oxygenation by pumping oxygen-rich surface water to the hypolimnion (HLO) is a commonly used tool for the restoration of nutrient-loaded dimictic lakes. However, in recent years its effectiveness has been questioned. In this case study we evaluated monitoring data covering a period of 23-years to show that, although experimental cessation of HLO drastically changed the lake's temperature and dissolved oxygen regimes, it did not significantly affect its trophic status. Thus, we recommend that the limited financial resources available are better directed towards further lowering the lake's external phosphorus load than continuing HLO.     

南黄海叶绿素a与初级生产力之间的相关分析

本文依据南黄海海域的调查资料,探讨了叶绿素ａ与初级生产力和真光层内叶绿素ａ积分值之间的相关关系。并对表层叶绿素ａ是否可以作为海洋中浮游植物蕴藏量的指标加以验证。验证的具体方法是分析表层叶绿素ａ（ＳＣ）;真光层内叶绿素ａ积分值（ＩＣ）和初级生产力（ＰＰ）三者之间的相关关系。分析表明：在叶绿素ａ含量高且变化梯度大的高生产力海域,ＳＣ、ＩＣ和ＰＰ之间存在着非常显著的相关性,ＳＣ可以作为某海域浮游植物现存量及其生产力的指标;而在叶绿素ａ和初级生产力低且分布均匀的海域,ＳＣ、ＩＣ和ＰＰ之间不相关。故指出利用ＳＣ作为某海域浮游植物蕴藏量和初级生产力指标时应慎重。     

Retrieval of chlorophyll and nitrogen in Norway spruce (Picea abies L. Karst.) using imaging spectroscopy

The research evaluated the information content of spectral reflectance (laboratory and airborne data) for the estimation of needle chlorophyll (C_AB) and nitrogen (C_N) concentration in Norway spruce (Picea abies L. Karst.) needles. To identify reliable predictive models different types of spectral transformations were systematically compared regarding the accuracy of prediction. The results of the cross-validated analysis showed that C_AB can be well estimated from laboratory and canopy reflectance data. The best predictive model to estimate C_AB was achieved from laboratory spectra using continuum-removal transformed data (R²cv = 0.83 and a relative RMSEcv of 8.1%, n = 78) and from hyperspectral HyMap data using band-depth normalised spectra (R²cv = 0.90, relative RMSEcv = 2.8%, n = 13). Concerning the nitrogen concentration, we observed somewhat weaker relations, with however still acceptable accuracies (at canopy level: R²cv = 0.57, relative RMSEcv = 4.6%). The wavebands selected in the regression models to estimate C_AB were typically located in the red edge region and near the green reflectance peak. For C_N, additional wavebands related to a known protein absorption feature at 2350 nm were selected. The portion of selected wavebands attributable to known absorption features strongly depends on the type of spectral transformation applied. A method called “water removal” (WR) produced for canopy spectra the largest percentage of wavebands directly or indirectly related to known absorption features. The derived chlorophyll and nitrogen maps may support the detection and the monitoring of environmental stressors and are also important inputs to many bio-geochemical process models.     

基于TM数据的太湖叶绿素A浓度定量反演

利用TM(ETM)数据与准实时地面采样数据,建立太湖叶绿素浓度反演模型。结果表明,TM3/(TM1+TM4)与叶绿素A浓度的相关性最好,并以此建立了太湖叶绿素A浓度线性反演模型,但反演精度并不高,因此,建立了一个两层BP神经网络模型反演太湖的叶绿素A浓度,结果表明,神经网络模型的反演精度远高于线性反演模型,16个测试样本表明,神经网络模型反演的相对误差小于30%的有15个点,占总测试样本93.75%,而线性反演模型反演相对误差在30%以下的仅有3个点,这表明对于太湖这样一个光谱特征复杂的二类水体,可以利用神经网络模型反演水质参数。     

Towards a more ecologically relevant assessment of the impact of heavy metals on the photosynthesis of the seagrass,Zostera capricorni

This in situ study used photosynthetic activity (measured as chlorophyll a fluorescence) and photosynthetic pigment concentrations to assess the effect of copper, cadmium, lead and zinc on the seagrass Zostera capricorni. Custom-made portable in situ exposure (PIE) chambers were developed so seagrasses could be dosed within the meadow. Z. capricorni was exposed to 0.1 and 1 mg l⁻¹ of metal solutions for 10 h. During this time and for the subsequent four-day recovery period, the effective quantum yield of photosystem II (PS II) (ΔF/Fm^′) was measured. While the results were variable, copper and zinc exposed samples had a depressed ΔF/Fm^′ during the exposure period. Samples exposed to zinc recovered to pre-exposure levels but those exposed to copper did not. Cadmium and lead did not impact on the chlorophyll a fluorescence and the chlorophyll pigment data supported these findings. This study presents an innovative new application of chlorophyll a fluorescence stress assessment.     

Harmful algal blooms (HABs) in Daya Bay, China: An in situ study of primary production and environmental impacts

A month-long investigation of phytoplankton biomass and primary production (PP) was carried out during a harmful algal bloom (HAB) in Daya Bay, China, in 2003. During the bloom, the phytoplankton community was dominated by Scrippsiella trochoidea and Chattonella marina. The phytoplankton biomass (Chl a) and PP reached peak levels of 519.21 mg m⁻³ and 734.0 mgC m⁻³ h⁻¹, respectively. Micro-phytoplankton was the key contributor to Chl a and PP in a cage-culture area and in the adjacent HAB-affected waters, with percentages of up to 82.91% and 84.94%, respectively. The HAB had complicated relationships with hydrological and meteorological factors in Daya Bay. However, the water around the cage-culture area always showed statistically greater phytoplankton biomass and nutrient loadings than in adjacent waters, suggesting that this was the “trigger area” of the bloom. The spatial and temporal distribution of diverse HABs in Daya Bay, their ecological characteristics, and their environmental impacts are also discussed in this paper.     

Primary production processes in the Taiwan Strait——Spatial and temporal variations of phytoplankton biomass and productivity

INTRODUCTIONAsthefundamentalbasisofthewholebiogeOChemicalcyclingofcarbon,primaryproduction.TIsWOrkwassupportedbyfUndsfmtheStateEducation~ssboandFujianaudienceFOUndstion.processesswitchontheflowofmaterialsandenergyintheoceanicecosystem,supportlargeamountoffisheryproductiononwhichourhumanbeingsrelyonfacesupply.Althoughconsistingonly8%oftheglobaloceanarea,coastalregionssupply26%oftheglobaloceanicbiologicalproductsand2/3--3/4oftotalfisheryresources.Therefore,theinvestigationsonphytoplank…     

低温对玉米幼苗生理反应的影响

将玉米晚熟品种吉单159三叶期幼苗进行6 ℃、10 ℃低温处理3天、6天,发现幼苗脯氨酸含量明显增加,电导率提高,可溶性蛋白含量随着低温处理时间的延长先增加后减少,叶绿素SPAD值减少,光合速率下降。     

东、黄海典型海域叶绿素a含量的垂向变化与周日波动

2000年10月21至11月5日对东海与黄海典型海区进行了叶绿素a浓度的现场周日观测，地理环境和水文状况的差异使各海区的垂向变化与日波动表现各自的特征：东海观测站位在垂向上的分布比较单一，多数呈上混合层均匀分布型并在跃层以上递减；长江口受潮流影响大，偶而在底层峰值，而南黄海观测站位垂向布出现了均匀分布型与次表层双峰型两种，受潮流等影响，叶绿素a浓度的日变化在各海区间及各自的垂向上都有所差异；出现层化的测站，跃层以上日波动层以下明显；在E7测站的表层和长江口测站的底层都以半日周期为，而南黄海测站以全日周期为主。