Decline in the Primary Productivity of Northwestern European Forests as a Consequence of Climate Aridization

Average annual age-dependent changes of carbon accumulation in the stemwood of major forest species (pine, spruce, and birch) of the taiga zone of the northwestern European Russia (Karelia) were analyzed. The changes in carbon accumulation were assessed by comparing carbon reserves in tree stands of various ages. Net primary productivity of photosynthesis (NPP) and the proportionality coefficient between respiratory decarboxylation and carbon reserves in wood were calculated. NPP clearly decreased with increasing climate aridization (aridity index). However, the time of the attainment of climax state by a stand did not depend on the latitudinal climate gradient. Hence, only the size of heterotrophic part of phytomass determines annual carbon losses in northern-taiga stands. It is concluded that the climate dependency of the long-term carbon storage in the phytomass of boreal forests is mainly determined by the climate effect on photosynthetic carbon sequestration.__________Translated from Fiziologiya Rastenii, Vol. 52, No. 4, 2005, pp. 513–517.Original Russian Text Copyright © 2005 by Voronin, Konovalov, Bolondinskii, Kaipiainen, Mao.     

Influence of the mixing regime on algal photosynthetic performance in laboratory scale enclosures

The photosynthesis of plankton sampled from the eutrophic Lake Loosdrecht was studied in Laboratory Scale Enclosures (LSEs) with regard to the rate of mixing. First, two LSEs were operated at different mixing rates. No significant differences in photosynthetic performance were found, with the exception of a depressed photosynthesis in the afternoon in the LSE which had a low mixing rate. Secondly, when mixing was stopped, the phytoplankton which stayed in the dark due to the steep light gradient in the LSE responded by changing its maximal photosynthetic capacity. The results show that the filamentous cyanobacteria in the lake can respond rapidly to changes in the depth of the mixed layer by altering their photosynthetic performance.This is publication 567 of the Centre for Estuarine and Coastal Ecology.     

In situ Development of Perch Eggs,Perca fluviutilis L. (Pisces,Percidae) in a Small Eutrophic Lake,Lake Plussee,Holstein, Germany

Naturally spawned egg strands of perch, Perca fluviatilis L. were sampled from exposed fir trees submerged in Lake Plußsee, Holstein, Northern Germany from April to May 1989. These were incubated in situ and in the laboratory to estimate the viability, development and abnormalities of the embryos. From the in siru incubated eggs 91.6% embryos were viable, the nonviable portion comprising 1.1 % unfertilized eggs, 5.1 % dead and 2.2 % with abnormalities. As compared to the eggs incubated in the laboratory with 84.1 % viable embryos, the nonviable portion consisting 1.1 % unfertilized eggs, 11.3 % dead and 3.5 % with abnormalities. Incubation rate of P. fluviatilis embryos both in situ and laboratory, ranged from 200-210 ATUs (10°C in situ and 8°C in the laboratory) with incubation period of 20-27 days from fertilization to 50 % hatching.     

In situ recalibration of probes of dissolved gas concentrations in bioreactors without effect on metabolism and growth

This article describes a general method for the in situ recalibration of a probe for dissolved gas concentrations without changing any parameter but the gas composition. Recalibration of an oxygen probe is used as an example.The recalibration procedure can be used for any probe, provided the culture's rate of metabolism and growth is independent of the substrate concentration in the range being measured by the probe during recalibration. The method was tested using a galvanic oxygen electrode in an oxygen-consuming culture of Klebsiella oxytoca and an oxygen-evolving culture of Anabaena variabilis. The recalibration caused no detectable effect on the metabolism and growth of the cultures, provided the dissolved oxygen tension was above 3muM.     

强光下硫化氢通过促进光系统II的活性来缓解水稻的光抑制

以水稻品种‘II优084’为材料,测定了强光胁迫下,水稻光合速率、叶绿素荧光快速诱导曲线（OJIP）以及O2ˉ·和H2O2在水稻叶片中积累的影响。结果表明强光胁迫下,水稻的净光合速率及气孔导度下降;光系统II（PSII）反应中心关闭的比例以及电子传递链中光系统II受体侧原初醌受体（QA）的还原程度增加;PSII反应中心电子传递的量子产额、能量以及传递到下游电子链的比率下降;光抑制下PSII的过剩能量向PSI的状态装换减少;自由基的产生增加。而施加作为硫化氢（H2S）供体的外源硫氢化钠（NaHS）后,上述影响PSII活性的指标的负变化被缓解,捕光天线复合体LHC通过在两个光系统之间的移动,来调节两个光系统的能量分配。强光下H2S处理能促进LHC离开PSII,与PSI结合,从而减少PSII分配的激发能,增加PSI分配的激发能,缓解了PSII的过度还原。以上结果表明外源H2S通过促进PSII的光合活性来缓解水稻光抑制伤害。     

Studies on the Primary Production of Phytoplankton in Suraha Lake (Ballia,India)

The paper describes the seasonal variation in the rate of phytoplankton primary production in Suraha Lake – a large shallow water body – in relation to certain physico-chemical parameters and the abundance and composition of the phytoplankton over a period of two years.     

我国自然湿地的基本特点

我国自然湿地的基本特点王宪礼（中国科学院沈阳应用生态研究所,１１００１５）ＴｈｅＦｕｎｄａｍｅｎｔａｌＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｔｈｅＷｅｔｌａｎｄｓｉｎＣｈｉｎａ．ＷａｎｇＸｉａｎｌｉ（ＩｎｓｔｉｔｕｔｅｏｆＡｐｐｌｉｅｄＥｃｏｌｏｇｙ,...     

The effects of diel changes in circulation and mixing on the longitudinal distribution of phytoplankton in a canyon‐shaped Mediterranean reservoir

1. The near‐surface distribution of phytoplankton cells along the thalweg of a canyon‐shaped reservoir (El Gergal, southern Spain) during two surveys is described and interpreted as the result of time‐varying large‐scale circulation patterns, vertical mixing processes and the physiological capacity of algal cells to regulate its position in the water column. 2. Vertical gradients of chlorophyll‐a concentration developed in the water column during the day but disappeared at night, as a result of the shoaling and deepening of the diurnal mixed layer (dml). The changes in the depth of the dml are largely controlled in El Gergal by convectively driven mixing processes. The longitudinal circulation changes, in turn, as a result of weak and diurnal land‐sea breezes. The distribution of algal cells was patchy at all times but did not change during any of the surveys. 3. An expression is proposed to estimate time scales for the development of horizontal patchiness T_P based on simple concepts of transport. It is shown that T_P is in the order of a week, indicating that horizontal patchiness does not respond immediately to hourly changes in the controlling factors. The magnitude of T_P, though, depends on how the vertical distribution of chlorophyll‐a and longitudinal currents change on subdiurnal time scales. In particular, T_P is sensitive to the lag existing between the momentum and heat fluxes through the free surface, driving circulation and vertical mixing.     

基于光子学技术研究弱光胁迫早期拟南芥光合损伤机理

弱光限制植物的光合作用,降低了光合作用效率,造成农业产量下降.本文主要研究了弱光处理早期,拟南芥光合作用相关指标的变化.研究中发现在弱光处理的早期,植株生长表型和最大光化学效率（Fv/Fm）没有明显变化,实际光化学效率Y（Ⅱ）以及光系统电子传递效率（ETR）下降较明显.此外,弱光处理原生质体,利用2 ＇,7＇-二氯二氢荧光素二乙酯（dichlorofluorescin diacetate,H2DCF-DA）染色,共聚焦显微镜观察,发现细胞中有较明显的活性氧（ROS）合成,且定位于叶绿体.该研究结果为植物弱光耐受性的研究提供理论依据.     

The role of iron in phytoplankton photosynthesis,and the potential for iron-limitation of primary productivity in the sea

Iron supply has been suggested to influence phytoplankton biomass, growth rate and species composition, as well as primary productivity in both high and low NO₃ ^– surface waters. Recent investigations in the equatorial Pacific suggest that no single factor regulates primary productivity. Rather, an interplay of bottom-up (i.e., ecophysiological) and top-down (i.e., ecological) factors appear to control species composition and growth rates. One goal of biological oceanography is to isolate the effects of single factors from this multiplicity of interactions, and to identify the factors with a disproportionate impact. Unfortunately, our tools, with several notable exceptions, have been largely inadequate to the task. In particular, the standard technique of nutrient addition bioassays cannot be undertaken without introducing artifacts. These so-called bottle effects include reducing turbulence, isolating the enclosed sample from nutrient resupply and grazing, trapping the isolated sample at a fixed position within the water column and thus removing it from vertical movement through a light gradient, and exposing the sample to potentially stimulatory or inhibitory substances on the enclosure walls. The problem faced by all users of enrichment experiments is to separate the effects of controlled nutrient additions from uncontrolled changes in other environmental and ecological factors. To overcome these limitations, oceanographers have sought physiological or molecular indices to diagnose nutrient limitation in natural samples. These indices are often based on reductions in the abundance of photosynthetic and other catalysts, or on changes in the efficiency of these catalysts. Reductions in photosynthetic efficiency often accompany nutrient limitation either because of accumulation of damage, or impairment of the ability to synthesize fully functional macromolecular assemblages. Many catalysts involved in electron transfer and reductive biosyntheses contain iron, and the abundances of most of these catalysts decline under iron-limited conditions. Reductions of ferredoxin or cytochrome f content, nitrate assimilation rates, and dinitrogen fixation rates are amongst the diagnostics that have been used to infer iron limitation in some marine systems. An alternative approach to diagnosing iron-limitation uses molecules whose abundance increases in response to iron-limitation. These include cell surface iron-transport proteins, and the electron transfer protein flavodoxin which replaces the Fe-S protein ferredoxin in many Fe-deficient algae and cyanobacteria.     

Impact of a Flood Event on the Planktonic Food Web of the Schelde Estuary (Belgium) in Spring 1998

To evaluate the effect of short-term changes in discharge on plankton dynamics, a station in the upper reaches of the Schelde estuary was monitored during 1 month in spring 1998 with a sampling frequency of 1–2 days. During this monitoring period, a flood event occurred during which discharge increased about 5-fold. This flood event had a strong effect on the composition of the planktonic community. Rotifers were strongly negatively affected by the flood event while densities of heterotrophic nanoflagellates and scuticociliates increased. Chlorophyll a concentration and abundance of bacteria, oligotrich ciliates and crustacean zooplankton did not respond clearly to the flood event. Although the flood event lasted only a few days it took more than 2 weeks for the planktonic community to return to its original composition.     

Development of an in vitro incubation technique for the estimation of the utilizable crude protein (uCP) in feeds for cattle

An in vitro incubation technique based on the first stage of the in vitro digestion technique published by Tilley and Terry (1963) was developed to estimate the utilizable crude protein (uCP) of single feeds and feed mixtures as non ammonia‐N after 24 h of incubation. The results of 25 feed samples showed that there was a significant relationship between the uCP values calculated by regression based on in vivo data sets (Y, CP [g‐kg^‐1 DM]) and those measured by the in vitro incubation technique (X, CP [g‐kg^‐1 DM], 24 h incubation):

y=0.85x+18.0, r²=0.84, P≤0.001.

It was concluded that it can be possible to determine the uCP value of single feeds or feed mixtures by this in vitro incubation technique and to estimate the uCP value of feeds by this regression equation.     

CO2浓度升高对大豆冠层光合速率影响的数值模拟研究

利用美国Li-6200光合测定系统对鲁豆4号叶片光合速率进行了大量测定研究,确定了大豆叶片光-光合作用模式,模式中考虑了CO2浓度对光合作用速率的影响,在此基础上进一步测定了大豆冠层结构,建立了一个大豆冠层光合速率数值模式.利用GXH-305红外线CO2分析仪外接50×50×120cm同化箱对冠层光合速率进行了实际测定,结果表明当CO2浓度低于660ppm时,模式可以较好地模拟出CO2浓度升高对群体光合速率的影响,平均相对误差为7.41%.本文所测得的大量实验数据,为研究CO2浓度升高对大豆生长影响提供了更加可靠的模型参数,同时也为进一步建立自然状况下大豆生长数值模式提供了一定的理论依据.     

The influence of the diel climatic cycle on the depth-time distribution of phytoplankton and photosynthesis in a shallow equatorial lake (Lake Baringo,Kenya)

Lake Baringo is a shallow equatorial lake. This paper reports a diel study of the depth-time distribution of phytoplankton and photosynthesis at one location in Lake Baringo on 10 March 1989. The water column shows a pattern of diurnal stratification probably accentuated by the high turbidity of the water and therefore rapid attenuation of solar energy. This stratified pattern breaks down at night due to atmospheric cooling and the regular onset of winds in the early evening. The phytoplankton is dominated byMicrocystis aeruginosa with some associated epiphytes. It concentrates in the narrow euphotic zone during the diurnal period of stratification due to buoyancy of theMicrocystis; evening breakdown of the thermocline results in the phytoplankton being mixed throughout the water column. A series of measurements of photosynthesis throughout the diurnal period gives an areal rate of 3.8 g O₂ m⁻² d⁻¹. The relationship between this value and the level of fish exploitation in Lake Baringo is discussed. The diel cycle in Lake Baringo is interpreted as dominating over any seasonal limnological cycle in the lake.     

Earlier onset of the spring phytoplankton bloom in lakes of the temperate zone in a warmer climate

The decoupling of trophic interactions is potentially one of the most severe consequences of climate warming. In lakes and oceans the timing of phytoplankton blooms affects competition within the plankton community as well as food–web interactions with zooplankton and fish. Using Upper Lake Constance as an example, we present a model‐based analysis that predicts that in a future warmer climate, the onset of the spring phytoplankton bloom will occur earlier in the year than it does at present. This is a result of the earlier occurrence of the transition from strong to weak vertical mixing in spring, and of the associated earlier onset of stratification. According to our simulations a shift in the timing of phytoplankton growth resulting from a consistently warmer climate will exceed that resulting from a single unusually warm year. The numerical simulations are complemented by a statistical analysis of long‐term data from Upper Lake Constance which demonstrates that oligotrophication has a negligible effect on the timing of phytoplankton growth in spring and that an early onset of the spring phytoplankton bloom is associated with high air temperatures and low wind speeds.     

Bioassay for phosphate demand in phytoplankton from acidified lakes: Lake Njupfatet,an example of phosphate deficiency induced by liming

A bioassay was developed, involving steady-state ATP level determinations, for estimation of phosphate demand and deficiency in natural phytoplankton communities. The studies were performed on phytoplankton from the moderately acidified Lake Njupfatet in central Sweden before and after liming. Phytoplankton samples from in situ enclosure experiments with low-dose enrichments of nitrate and phosphate and removal of large (> 100 µm) zooplankton and from the lake water were collected. The phytoplankton were concentrated by through-flow centrifugation and post-cultured in the laboratory with or without the addition of phosphate. A relative increase in the ATP:chlorophyll a ratio after the phosphate treatment as compared to samples without phosphate enrichment was found to be a highly reproducible indicator of phosphate deficiency in the natural phytoplankton population. In contrast, the absolute ATP:chlorophyll a ratio varied substantially between different sampling occasions. No phosphate deficiency was detected in phytoplankton from the acidic lake or from fertilized in situ enclosures. However, phytoplankton from in situ enclosures without added nutrients showed evidence of phosphate limitation after 21 days incubation. Also, the phytoplankton community developed a significant phosphate deficiency the summer after lake liming. The results from the ATP analyses are compared with chemical data of the lake water, phytoplankton community structure and phosphatase activities in the lake before and after liming. The average total biomass of phytoplankton and the average Tot-P measured during May to September decreased with appr. 30% after liming while Tot-N was essentially unaffected and the phosphatase activities increased by 1000–2000%.     

A test of a model for estimating production in the sea

Primary productivity was measured in the sea off the coasts of Florida and Georgia with the radiocarbon method at four stations during March, 1971. Integral photosynthesis per square meter surface was determined with a mathematical model from empirical data gathered from in situ and shipboard incubation experiments. The mathematical model provided shipboard incubators to be used to estimate primary production rates while overcoming the problem of relating light quality and quantity simulated by the incubators to that found in the euphotic zone. The use of shipboard incubation can allow for measurements to be made on a moving vessel, more stations visited per day and water samples incubated at a constant light intensity. Primary productivity at the four sampling stations ranged from 0.026 to 0.042 mg C/M² hr.     

Light, nutrients and primary productivity in Lake Biwa: An evaluation of the current ecosystem situation

Simple correlation and multiple regression analyses were performed to examine the relationship between primary productivity and environmental factors in the north basin of Lake Biwa. The primary production rates used in the analyses were estimated monthly or bimonthly during the growing season (April–November) in 1992, 1996 and 1997 with the ¹³C method. Elemental (C, N and P) contents of seston were used to assess nutrient conditions. Analyses revealed that 86% of variance in depth-integrated primary production rates (areal PP) can be explained by changes in light intensity, and sestonic C, N and P concentrations. Water temperature had no effect on areal PP. To assess relative effects of light and nutrients on PP, the P:B ratio was estimated by normalizing PP with sestonic C. The areal P:B ratio correlated most significantly with the sestonic N:P ratio, followed by light intensity. When regression analyses were made at each depth, however, the P:B ratio correlated significantly only with the sestonic N:P ratio at 0 and 1 m depths, while light intensity was also incorporated into the regressions at deeper than 2.5 m. In these regressions, the P:B ratio was negatively correlated with sestonic N:P ratio but positively with light intensity. The results suggest that the primary production rate in this lake was mainly limited by P relative to N supply rates, but was not free from light limitation in a large part of the epilimnion. In Lake Biwa, the vertical water mixing regime as well as the nutrient supply seem to be important in determining the growth and composition of primary producers, since the surface mixing layer extends into 10–15 m depths during most of the growing season.