Wasserqualität durch höhere Wasserpflanzen. — Übersicht zur ökotechnologischen Anwendung —

Improving Water Quality by submerged and emergent Macrophytes. — A Review of Ecotechnological Application. Measures of ecotechnology using submerged and emergent macrophytes in native stands or planted littoral stands on the one hand, ingenious swimming plant mats on the other, may be assessed to be successful if applied in combination with additional measures, for instance — reorganization (sanition) of all the area collecting water — biomanipulation of pelagic food chains. Plantation of submerged macrophytes as oxygenators in standing and impounded waters to improve water quality should be avoided. To the contrary, the strategy should be taking measures in order to maximize the light penetrated euphotic zone (z_eu) and simultaneously minimize the mixed zone (z_mix) in order to improve spontaneous settlements of submerged macrophyte stands.     

马桑根瘤的固氮活性与呼吸强度

马桑Coriaria sinica根瘤固氮与呼吸作用具有一定的依赖关系。根瘤的二氧化碳呼出量与乙烯生成量之日平均比值(CO_2:C_2H_4值)为6.263±1.202。此值在一定程度上反映了固氮对能量的需求,但受土壤温度和湿度的影响而变化甚大。     

南极沿海伯尔顿盐湖双刺镰状水蚤氧代谢的季节变化及其影响因素

对南极沿海伯尔顿盐湖浮游桡足类双剌镰状水蚤的耗氧量进行六个月的连续测定,结果表明,动物在越冬过程中氧代谢呈下降趋势,其耗氧量从8月份的0.2775(μl·mg~(-1)wet·h~(-1))到翌年1月份降为0.0467(μl·mg~(-1)wet·h~(-1));其中8—12月耗氧量变化较为平缓,月平均下降率为14.62％;12—1月耗氧量变化较大,下降率为66.93％。动物的耗氧量与盐湖环境的季节变化和动物自身的一些生理变化有密切的关系,在12月份以前动物耗氧量变化可能主要与湖中浮游植物和溶解氧的减少有关,而12月份以后动物的迅速衰老则可能成为动物耗氧量急剧下降的重要因素。     

塔克拉玛干沙漠腹地流沙下垫面土壤呼吸特征及影响因素分析

通过LI-COR8100A土壤碳通量观测系统分别于2013年1月、5月、10月和11月进行了塔克拉玛干沙漠腹地塔中流沙下垫面土壤呼吸速率测定试验,并分析了相应的土壤水热因子对呼吸速率的影响。结果表明:塔克拉玛干沙漠腹地土壤呼吸速率整体偏低,但具有明显的昼夜波动性和季节变化特征。研究区流沙土壤中可能存在的无机碳过程是导致夜间及凌晨的土壤呼吸速率为负值,白天为正值的主要原因。不同时段的土壤呼吸速率(Rs)分别与土壤表层0~5 cm平均土壤温度(T)和湿度(W)间存在较为同步的昼夜变化趋势且具有良好的回归关系。相对于单因素影响的回归分析,土壤温、湿度的协同作用能够从整体角度更好地解释土壤呼吸速率的变化情况。回归方程Rs=a+bT+cW和Rs=a+bT+cW+dTW可解释不同时段土壤呼吸速率76.0%以上的变化情况。这说明土壤温、湿度是控制土壤呼吸速率的主要环境因子。沙漠腹地土壤极低的水分条件成为土壤呼吸的限制性因子,呼吸速率对于作为限制性因子的土壤湿度的变化响应则更加直接,而对于土壤温度变化的敏感性就有所下降,导致土壤呼吸速率与土壤温度回归关系出现明显的时滞环现象。     

Upscaling plot-scale soil respiration in winter wheat and summer maize rotation croplands in Julu County,North China

Soil respiration (R_s) data from 45 plots were used to estimate the spatial patterns of R_s during the peak growing seasons of winter wheat and summer maize in Julu County, North China, by combining satellite remote sensing data, field-measured data, and a support vector regression (SVR) model. The observed R_s values were well reproduced by the model at the plot scale, with a root-mean-square error (RMSE) of 0.31 μmol CO₂ m⁻² s⁻¹ and a coefficient of determination (R²) of 0.73. No significant difference was detected between the prediction accuracy of the SVR model for winter wheat and summer maize. With forcing from satellite remote sensing data and gridded soil property data, we used the SVR model to predict the spatial distributions of R_s during the peak growing seasons of winter wheat and summer maize rotation croplands in Julu County. The SVR model captured the spatial variations of R_s at the county scale. The satellite-derived enhanced vegetation index was found to be the most important input used to predict R_s. Removal of this variable caused an RMSE increase from 0.31 μmol CO₂ m⁻² s⁻¹ to 0.42 μmol CO₂ m⁻² s⁻¹. Soil properties such as soil organic carbon (SOC) content and soil bulk density (SBD) were the second most important factors. Their removal led to an RMSE increase from 0.31 μmol CO₂ m⁻² s⁻¹ to 0.37 μmol CO₂ m⁻² s⁻¹. The SVR model performed better than multiple regression in predicting spatial variations of R_s in winter wheat and summer maize rotation croplands, as shown by the comparison of the R² and RMSE values of the two algorithms. The spatial patterns of R_s are better captured using the SVR model than performing multiple regression, particularly for the relatively high and relatively low R_s values at the center and northeast study areas. Therefore, SVR shows promise for predicting spatial variations of R_s values on the basis of remotely sensed data and gridded soil property data at the county scale.     

Trends in carbon sink along the Belt and Road in the future under high emission scenario

Over the past three decades, the drawdown of atmospheric CO₂ in vegetation and soil has fueled net ecosystem production (NEP). Here, a global land-surface model (CABLE) is used to estimate the trend in NEP and its response to atmospheric CO₂, climate change, biological nitrogen (N) fixation, and N deposition under future conditions from 2031 to 2100 in the Belt and Road region. The trend of NEP simulated by CABLE decreases from 0.015 Pg carbon (C) yr^?2 under present conditions (1936–2005) to ?0.023 Pg C yr^?2 under future conditions. In contrast, the trend in NEP of the CMIP6 ensemble changes from 0.014 Pg C yr^?2 under present conditions to ?0.009 Pg C yr^?2 under future conditions. This suggests that the trend in the C sink for the Belt and Road region will likely decline in the future. The significant difference in the NEP trend between present and future conditions is mainly caused by the difference in the impact of climate change on NEP. Considering the responses of soil respiration (RH) or net primary production (NPP) to surface air temperature, the trend in surface air temperature changes from0.01°C yr^?1 under present conditions to 0.05°C yr^?1 under future conditions. CABLE simulates a greater response of RH to surface temperature than that of NPP under future conditions, which causes a decreasing trend in NEP. In addition, the greater decreasing trend in NEP under future conditions indicates that the C–climate–N interaction at the regional scale should be considered. It is important to estimate the direction and magnitude of C sinks under the C neutrality target.摘要目前, 在区域尺度, NEP趋势变化的强度和影响机制还存在很大的不确定性. 针对这一问题, 我们选取了一带一路覆盖的区域为研究对象, 基于全球陆面模式 (CABLE)和第六次国际耦合模式比较计划 (CMIP6), 评估了历史和未来NEP趋势的变化, 分析了影响的机制. 从过去到未来, CABLE结果表明NEP的趋势从 0.015 Pg C yr^?2 减少到 –0.023 Pg C yr^?2; CMIP6结果为从0.014 Pg C yr^?2转变为–0.009 Pg C yr^?2. 气候变化是引起这一变化的主因. 我们的研究结果强调了碳-气候-氮相互作用的重要性, 这对碳中和目标下碳汇潜力的准确估算尤为重要.     

Distribution of amphipods Ischyrocerus on the red king crab, Paralithodes camtschaticus: Possible interactions with the host in the Barents Sea

The determination of costs and benefits experienced by crustaceans as a result of occupation by their symbionts has received increased attention from marine ecologists. However, the interactions between some important species and their associates remain unclear. We examined the distribution of amphipods in the genus Ischyrocerus on the red king crab Paralithodes camtschaticus, a commercially important species, in two areas of the Barents Sea. Ischyrocerus commensalis was found on 30.5% of crabs in Dalnezelenetskaya Bay (DZB) with the mean number per crab being 55.1, in Dolgaya Bay (DLB) these rates were 28.6% with 19.3 specimens per crab. Sympatric species Ischyrocerus anguipes was found on 13.5% of crabs in DZB with a mean of 7.3 individuals per host, in DLB it had much lower occurrence (1.3% and 1.5 specimens per host). There were no significant differences between proportions of male and female crabs infested by amphipods in both areas examined. Prevalence of amphipods was similar among years examined except for I. commensalis on small crabs (carapace length CL <90 mm) and I. anguipes on large crabs (CL >90 mm) in DZB. We found that I. commensalis and I. anguipes are not egg predators of P. camtschaticus in the Barents Sea, at least in summer. High numbers of I. commensalis occur in crab gills, and both mean intensity of the amphipods and their empty tubes increased with crab size. In the gills, I. commensalis predominated in the section nearest the mouth parts. Possible negative impacts for the hosts due to gills infestation are discussed. In contrast, I. anguipes were predominately found on the carapace and limbs of crabs and appears to be a less specific symbiont of P. camtschaticus. Both amphipod species seem to be commensals, however possible negative impacts for the host could not be excluded.     

Effects of irradiance on benthic and water column processes in a Gulf of Mexico estuary: Pensacola Bay, Florida, USA

We examined the effect of light on water column and benthic fluxes in the Pensacola Bay estuary, a river-dominated system in the northeastern Gulf of Mexico. Measurements were made during the summers of 2003 and 2004 on 16 dates distributed along depth and salinity gradients. Dissolved oxygen fluxes were measured on replicate sediment and water column samples exposed to a gradient of photosynthetically active radiation. Sediment inorganic nutrient (NH₄⁺, NO₃⁻, PO₄³⁻) fluxes were measured. The response of dissolved oxygen fluxes to variation in light was fit to a photosynthesis–irradiance model and the parameter estimates were used to calculate daily integrated production in the water column and the benthos. The results suggest that shoal environments supported substantial benthic productivity, averaging 13.6 ± 4.7 mmol O₂ m⁻² d⁻¹, whereas channel environments supported low benthic productivity, averaging 0.5 ± 0.3 mmol O₂ m⁻² d⁻¹ (±SE). Estimates of baywide microphytobenthic productivity ranged from 8.1 to 16.5 mmol O₂ m⁻² d⁻¹, comprising about 16–32% of total system productivity. Benthic and water column dark respiration averaged 15.2 ± 3.2 and 33.6 ± 3.7 mmol O₂ m⁻² d⁻¹, respectively Inorganic nutrient fluxes were generally low compared to relevant estuarine literature values, and responded minimally to light exposure. Across all stations, nutrient fluxes from sediments to the water column averaged 1.11 ± 0.98 mmol m⁻² d⁻¹ for NH₄⁺, 0.58 ± 1.08 mmol m⁻² d⁻¹ for NO₃⁻, 0.01 ± 0.09 mmol m⁻² d⁻¹ for PO₄³⁻. The results of this study illustrate how light reaching the sediments is an important modulator of benthic nutrient and oxygen dynamics in shallow estuarine systems.     

Influence of river discharge on plankton metabolic rates in the tropical monsoon driven Godavari estuary,India

To examine the influence of river discharge on plankton metabolic balance in a monsoon driven tropical estuary, daily variations in physico-chemical and nutrients characteristics were studied over a period of 15 months (September 2007 to November 2008) at a fixed location (Yanam) in the Godavari estuary, India. River discharge was at its peak during July to September with a sharp decrease in the middle of December and complete cessation thereafter. Significant amount of dissolved inorganic nitrogen (DIN, of 22–26 μmol l⁻¹) and dissolved inorganic phosphate (DIP, of 3–4 μmol l⁻¹) along with suspended materials (0.2–0.5 g l⁻¹) were found at the study region during the peak discharge period. A net heterotrophy with low gross primary production (GPP) occurred during the peak discharge period. The Chlorophyll a (Chl a) varied between 4 and 18 mg m⁻³ that reached maximum levels when river discharge and suspended loads decreased by >75% compared to that during peak period. High productivity was sustained for about one and half months during October to November when net community production (NCP) turned from net heterotrophy to autotrophy in the photic zone. Rapid decrease in nutrients (DIN and DIP by ∼15 and 1.4 μmol l⁻¹, respectively) was observed during the peak Chl a period of two weeks. Chl a in the post monsoon (October–November) was negatively related to river discharge. Another peak in Chl a in January to February was associated with higher nutrient concentrations and high DIN:DIP ratios suggest possible external supply of nitrogen into the system. The mean photic zone productivity to respiration ratio (P:R) was 2.38 ± 0.24 for the entire study period (September 2007–November 2008). Nevertheless, the ratio of GPP to the entire water column respiration was only 0.14 ± 0.02 revealing that primary production was not enough to support water column heterotrophic activity. The excess carbon demand by the heterotrophs could be met from the allochthonous inputs of mainly terrestrial origin. Assuming that the entire phytoplankton produced organic material was utilized, the additional terrestrial organic carbon supported the total bacterial activity (97–99%) during peak discharge period and 40–75% during dry period. Therefore, large amount of terrestrial organic carbon is getting decomposed in the Godavari estuarine system.