基于蛋白组学分析杜氏盐藻对不同浓度CO2的响应

用气体混合仪设置不同的CO_2浓度处理组,测定了杜氏盐藻(Dunaliella salina)细胞密度、碳酸酐酶活性、甘油含量等生理指标,结合蛋白质组学分析方法,比较了不同CO_2浓度下细胞内主要代谢路径蛋白表达的差异。结果表明:在一定范围内,随着CO_2浓度的升高,杜氏盐藻的生理活性及光合活性提高;而CO_2浓度过高对盐藻生长呈抑制作用; 3%CO_2浓度最适于本实验杜氏盐藻藻株的生长。随着CO_2浓度的升高,胞外碳酸酐酶活性下降。低浓度的CO_2有利于β-胡萝卜素的积累,且光系统Ⅱ(PSⅡ)光合活性在CO_2浓度0.03%～3%范围内上升, CO_2浓度达9%时降低,与光合作用相关蛋白的表达趋势接近。上述结果说明杜氏盐藻可能通过调节光合作用中叶绿素等捕光色素的合成及相关蛋白的表达笼统,以响应CO_2浓度的变化;而过高浓度的CO_2可对细胞产生氧化损害,引起热激蛋白和超氧化物歧化酶等蛋白含量的上调以应对氧化胁迫。     

不同光照强度下仙掌藻(Halimeda opuntia)对海洋酸化的生理响应

为探讨海洋酸化和光照强度变化对海洋钙化生物的影响,本文选用广泛分布在热带珊瑚礁区的大型钙化海藻仙掌藻(Halimeda opuntia)为研究对象,在室内通过CO2加富(pH=7.50、7.80和8.10)和调控光照强度(30和180μmol photons m2·s-1)的方式,探究其生长、钙化作用和光合作用等生理特征对海洋酸化和光照强度变化的响应。结果表明:海水酸化可以显著抑制仙掌藻的生长率、钙化速率和光合效率,且随酸化程度的加深而加强。酸化条件下(p H 7.50～7.80),生长率、钙化速率和Fv/Fm分别下降了48.29%～58.80%、51.78%～62.29%和2.37%～13.79%;光照强度的增加可以缓解这一抑制作用,高光照下生长率、钙化速率和Fv/Fm分别升高了2.01%～44.55%、29.61%～40.68%和1.68%～6.92%。酸化处理和光照强度变化对色素含量、丙二醛(MDA)和脯氨酸含量影响显著(P 0.01);酸化处理组中的Chl-a含量下降了32.69%～43.44%;而实验第20-28天,低光条件下的类胡萝卜素含量比高光照组高出12.12%～57.45%;酸化胁迫下,MDA在组织中逐渐积累;同时脯氨酸明显升高,以增加藻体自身的抗逆性,缓解胁迫带来的损伤。此外,组织中总碳(TC)和总氮(TN)含量在酸化条件下显著增加(P 0.05),光照强度的增加也一定程度上有利于提高TC和TN含量。通过分析可知,海洋酸化对仙掌藻的威胁是多方面的,对其生长、钙化作用和光合作用等生理过程的抑制作用随着酸化程度的加深而增加,而光照强度的增加一定程度上可以缓解酸化带来的负面效应。这些结果可以为预测未来海洋酸化对钙质生物的影响和珊瑚礁生物的多样性保护提供理论参考。     

Partial Pressure of Carbon Dioxide in Coral Reef Lagoon Waters: Comparative Study of Atolls and Barrier Reefs in the Indo-Pacific Oceans

Factors controlling the CO₂ system parameters, including the partial pressure of CO₂ (PCO₂) in coral reef waters, were investigated in three mid-oceanic reefs of the Indo-Pacific region. Surface water PCO₂ in the lagoons of Majuro Atoll and Palau barrier reef in the Pacific were 25 µatm and 48 µatm higher than those of the offshore waters, respectively, while South Male Atoll lagoon of the Maldives in the Indian Ocean exhibited relatively small difference in PCO₂ compared to the offshore water. Observations from Majuro Atoll and Palau barrier reef are consistent with the view that calcium carbonate production predominates in coral reefs. On the other hand, results from South Male Atoll can be attributed to the thorough flushing of the lagoon, which is connected to the open ocean by numerous deep channels. The offshore-lagoon PCO₂ difference depends on system-level net organic-to-inorganic carbon production ratio while reef topography, especially residence time of the lagoon, has a secondary effect on the magnitude of the offshore-lagoon difference. A potential for releasing CO₂ might be more evident in an enclosed atoll where the reef water has a longer residence time. Oceanic atoll and barrier reef lagoons, which are in the terminal stage of evolutionary history of oceanic volcanic islands, have the potential to release CO₂ to the atmosphere.     

Responses of photosynthesis and water relations to rainfall in the desert shrub creosote bush (Larrea tridentata) as influenced by municipal biosolids

Responses of photosynthesis (P_n), stomatal conductance (g_s), pre-dawn leaf water potential (Ψ_lp) and leaf water content (ω_l) of creosote bush to 10 rainfall events in the Chihuahuan Desert were investigated. Infiltration of rainwater was manipulated by applying municipal biosolids. The responses of P_nand water relation parameters to rainfall (>10 mm) were mainly dependent upon drought severity: (1) following a moderate drought, P_n, g_s, Ψ_lpand ω_lrecovered to corresponding values of irrigated plants within 2 days after a 23-mm rainfall; (2) Ψ_lpand g_sresponded to a 15-mm rainfall within 2 days, following a 25-day drought, whereas responses of P_nand ω_lwere delayed for several days; (3) responses of P_n, g_s, Ψ_lpand ω_lto a 14·7-mm rainfall were all delayed for several weeks following a 110-day drought, but the delay was longer in P_n, g_sand ω_lthan in Ψ_lp. Creosote bush responded to small rainfall events (approximately 6 to 8 mm) with an increase in Ψ_lp, but without noticeable changes in g_sand P_n, suggesting a strong stomatal control of water loss even though xylem embolism was reduced. Biosolids applied at high rates (3·4 and 9 kgm⁻²) decreased the soil water by 2 to 4 mm following rainfall events, and this in turn delayed and decreased the responses of P_nand water relation parameters to rainfall.P_nand g_swere linearly related to ω_land exponentially related to Ψ_lp. With the generally coincidental responses of P_nor g_sand ω_lto rainfall, we concluded that the responses of P_nand g_sto rainfall were dependent on leaf rehydration which resulted from restored hydraulic conductance following drought.     

Middle Layer Intrusion as an Important Factor Supporting Phytoplankton Productivity at a Tidal Front in Iyo Nada, the Seto Inland Sea, Japan

Field observations were conducted to examine the processes governing the phytoplankton distribution and photosynthetic activity in and around a tidal front formed in Iyo Nada, the Seto Inland Sea, Japan. The existence of a middle layer intrusion, which, it has been suggested, moves from the mixed region to the stratified region of the tidal front, was ascertained by the phytoplankton distribution in addition to a T-S diagram. Skeletonema costatum, which originally inhabited the mixed region, was used as the indicator to reveal the intrusion. However, the tip of water containing the S. costatum population did not extend deeply into the stratified region. The velocity of the intrusion seemed to be slow enough to make biological processes, such as nutrient uptake by phytoplankton and subsequent growth, as well as the decrease in cell density due to zooplankton grazing, dominate during the transportation. The patchy distribution of copepod nauplii implied that grazing has an influence on the distribution pattern of phytoplankton. The location of high photosynthetic activity did not coincide spatially with the center of high phytoplankton biomass, suggesting the importance of these biological processes. Therefore, it is considered that the middle layer intrusion plays a role as an inducer of subsequent biological processes at the tidal front by not only supplying nutrients from the mixed region but also by increasing the vertical diffusivity.     

Modelling Vegetation-Atmosphere Co2 Exchange By A Coupled Eulerian-Langrangian Approach

A Eulerian-Lagrangian canopy microclimate model wasdeveloped with the aim of discerning physical frombiophysical controls of CO₂ and H₂O fluxes. The model couples radiation attenuation with mass,energy, and momentum exchange at different canopylevels. A unique feature of the model is its abilityto combine higher order Eulerian closure approachesthat compute velocity statistics with Lagrangianscalar dispersion approaches within the canopy volume. Explicit accounting for within-canopy CO₂,H₂O, and heat storage is resolved by consideringnon-steadiness in mean scalar concentration andtemperature. A seven-day experiment was conducted inAugust 1998 to investigate whether the proposedmodel can reproduce temporal evolution of scalar(CO₂, H₂O and heat) fluxes, sources andsinks, and concentration profiles within and above auniform 15-year old pine forest. The modelreproduced well the measured depth-averaged canopy surfacetemperature, CO₂ and H₂O concentrationprofiles within the canopy volume, CO₂ storageflux, net radiation above the canopy, and heat andmass fluxes above the canopy, as well as the velocitystatistics near the canopy-atmosphere interface. Implications for scaling measured leaf-levelbiophysical functions to ecosystem scale are alsodiscussed.     

铁对三角褐指藻生长、光合作用及生化组成的影响

近来许多研究表明,不论是在无机氮丰富还是贫乏的水域,铁元素的供应对于浮游植物的生物量、生长率、种类组成及初级生产力均会产生影响。通过室内培养,研究了铁对三角褐指藻生长、光合作用以及细胞生化组成的影响。实验结果表明,在其他营养盐充足的条件下,海水中铁浓度的变化对三角褐指藻的生长及光合作用均有显着影响。在5×10-7mol/dm3铁浓度时,三角褐指藻可达到其最大光合作用速率。在添加铁的条件下,三角褐指藻细胞多种生化组成受到不同程度的影响,其中叶绿素a含量变化幅度最大,增加了25%～35%,叶绿素c、类胡萝卜素含量也有一定程度的增加,但增长幅度要小于叶绿素a;碳水化合物的含量增加了5%～10%,蛋白质含量的增加幅度在5%～15%之间;超氧化物歧化酶(SOD)的活性及DCMU荧光增强比(F_d/F)也呈明显的增加趋势。铁是海洋初级生产过程中的一种限制因子。     

光强和盐度对龙须菜生长及光合特性的影响

持续降雨会引起光照强度和海水表层盐度的变化。近年来,受梅雨影响,福建省龙须菜(Gracilariopsis lemaneiformis)栽培产量波动明显。为揭示其原因,本实验设置3个盐度梯度(低盐：16,中盐：24,高盐：32)和两个光强水平[低光：30μmol/(m²·s),高光：120μmol/(m²·s)],共6个不同处理组合,研究其对龙须菜生长和光合特性的影响。结果发现：(1)盐度、光照强度和二者交互作用对龙须菜的相对生长速率和净光合速率均具有显著影响(P<0.05),适当降低盐度、增加光照有利于提高藻体相对生长速率和净光合速率,同时盐度适当降低条件下藻体呼吸速率被显著抑制;(2)光照强度和盐度对龙须菜有效光合量子产率、最大相对电子传递速率、光能利用效率均具有显著影响(P<0.05),在光照增加条件下有效光合量子产率和最大相对电子传递速率随盐度增加呈先增加后降低的趋势,光照强度和盐度的交互作用仅对光能利用效率影响不显著(P>0.05);(3)盐度对龙须菜的光合色素含量具有显著影响(P<0.05),在同一光强条件...     

Underwater measurements of carbon dioxide evolution in marine plant communities: A new method

We developed a new methodology to determine CO₂ fluxes in intertidal and shallow subtidal plant communities, namely seagrasses, both when the plants are submerged and when they are air-exposed. The apparatus comprises closed incubation chambers and a gas exchange column, designed to remove carbon dioxide from the water. Different types of incubation chambers were designed and built to adapt the system to distinct environments and incubation requirements. The methodology was tested under a comprehensive range of situations and its advantages and limitations are discussed. Overall, the method provides precise measurements of community carbon dioxide fluxes, through a fast and non-intrusive process, allowing repeatable in situ measurements of carbon uptake both in submerged and air-exposed conditions. As the experimental apparatus is identical, directly comparable measurements of air-exposed and submerged community production may be obtained, allowing sound estimates of daily carbon budgets of intertidal and shallow subtidal communities.     

Is coastal lagoon eutrophication likely to be aggravated by global climate change?

Coastal zones are widely recognised as being particularly vulnerable to future environmental change. Although a significant number of previous papers warn of an increasing tendency in the appearance of eutrophication processes in such systems, very few papers have evaluated the influence of global climate change on eutrophication.