EFFECTS OF CLIMATE CHANGE ON GLOBAL SEAWEED COMMUNITIES

Seaweeds are ecologically important primary producers, competitors, and ecosystem engineers that play a central role in coastal habitats ranging from kelp forests to coral reefs. Although seaweeds are known to be vulnerable to physical and chemical changes in the marine environment, the impacts of ongoing and future anthropogenic climate change in seaweed‐dominated ecosystems remain poorly understood. In this review, we describe the ways in which changes in the environment directly affect seaweeds in terms of their physiology, growth, reproduction, and survival. We consider the extent to which seaweed species may be able to respond to these changes via adaptation or migration. We also examine the extensive reshuffling of communities that is occurring as the ecological balance between competing species changes, and as top‐down control by herbivores becomes stronger or weaker. Finally, we delve into some of the ecosystem‐level responses to these changes, including changes in primary productivity, diversity, and resilience. Although there are several key areas in which ecological insight is lacking, we suggest that reasonable climate‐related hypotheses can be developed and tested based on current information. By strategically prioritizing research in the areas of complex environmental variation, multiple stressor effects, evolutionary adaptation, and population, community, and ecosystem‐level responses, we can rapidly build upon our current understanding of seaweed biology and climate change ecology to more effectively conserve and manage coastal ecosystems.     

EFFECTS OF HERBIVORE SIZE AND HUNGER LEVEL ON PERIPHYTON COMMUNITIES1

The effects of herbivore size and hunger level were tested on lotic periphyton community structure and ash-free dry mass (AFDM). My hypotheses were 1) that small herbivores would remove more periphyton per unit biomass than large herbivores of the same species because of energetic demands and 2) that within the same size class, starved herbivores would remove more periphyton than nonstarved herbivores. The herbivore used was the prosobranch snail Elimia clavaeformis Lea. Seven treatments were employed: 1) no snails (control); 2) small “starved” snails; 3) large “starved” snails; 4) small and large “starved” snails; 5) small fed snails; 6) large fed snails; and 7) small and large fed snails. Although snails removed significant amounts of periphyton AFDM relative to controls, neither snail size nor degree of starvation had a significant effect on loss of total AFDM. Small snails removed significantly more erect forms of Stigeoclonium tenue (C. A. Ag.) Kütz. than large snails, but snail size had no other significant effect. Starved snails removed significantly more Cocconeis placentula Ehr. than fed snails, suggesting that after the more susceptible growth forms (e.g. erect Stigeoclonium) were removed, Cocconeis cells became more vulnerable to grazing by hungry snails. When small and large snails were combined in chambers, large snails gained weight over time, whereas small snails lost weight. These results suggest that intraspecific competition may occur within populations of Elimia.     

EFFECTS OF CHRONIC GAMMA IRRADIATION ON LICHEN COMMUNITIES OF A FOREST

Chronic gamma irradiation of an oak-pine forest on Long Island reduced populations of corticolous and terrestrial lichens in approximate proportion to the rate of irradiation. The decline in species diversity was approximately linearly related to logarithmic increases in daily radiation exposure. While a daily exposure of 2700 R/day was estimated to have reduced diversity to 50% in the first year, a linear extrapolation of diversity, coefficient of community and similarity curves to zero suggested that certain lichens would survive 3 years' exposure at daily rates of 5,000–10,000 R, possibly more. There was an apparent threshold at 300 R/day for radiation effects on the composition of lichen communities; changes in relative density occurred at lower exposures. The crustose forms were more resistant than foliose or fruticose forms, an observation which parallels previous observations that the most radio-resistant higher plants tend to be of short, stature.     

土壤因子对次生森林群落物种多样性的影响

利用３０个样方和９０个土样的数据,采用多元线性逐步回归分析,分别探讨了乔木种数,灌木种数,草本植物种数,总个体数,辛柏森指数和香农－魏耐指数等多样性指数及其发育速度与土壤的厚度,含水量,酸碱度,盐基总量,有效氮,速效磷和钙镁总量的相关性。     

模拟气候变化对３种草原植物群落混合凋落物分解的影响

 应用海拔引起的自然温度梯度作为气候变化研究的替代系统,结合网袋法,目的在于评价气候变化对草甸草原、羊草(Leymus chinensis )草原和大针茅(Stipa grandis)草原混合凋落物分解过程的可能影响。结果表明：较之当前气候,在气温升高2.7℃,降水基本保持不变的气候变化情景下,3种凋落物的分解速率分别提高了15.38％、35.83％和6.68％;而在温度升高2.2℃或更高,降水降低20％或更高的气候变化情景下,各种凋落物的分解速率将降低。此外,各种凋落物的分解动态对所模拟的气候变化情景的响应不同,但没有发现凋落物分解速率与凋落物本身C、N、C／N间的密切关系。     

EFFECTS OF CHIRONOMID (INSECTA: DIPTERA) TUBE-BUILDING ACTIVITIES ON STREAM DIATOM COMMUNITIES1,2

Chironomid retreats, constructed out of sand grains upon submerged wood debris, increase the surface area available for diatom colonization. The three dimensional substratum afforded by chironomid tubes supports up to twelve times the diatom biavolume found upon adjacent, unmodified substratum in a northern Michigan stream. Diatom enumeration within scrapings from small defined areas on artificial substrata, combined with examination of intact natural substrata through scanning electron microscopy (SEM), reveals distinct, microdistribution patterns. The larval retreats of two major taxa of tube-dwelling chironomid's (Micropsectra sp. and Pseudodiamesa cf. pertinax Garrett) display significantly different diatom communities relative to adjacent masonite substratum. Substratum without chironomid tubes is primarily colonized by Achnanthes minutissima Kütz. and Cocconeis placentula Ehr., exhibiting the lowest species diversity of microhabitats examined. The diatom flora upon sand tubes of Micropsectra sp. is dominated by Opephora martyi Herib., as is the flora of sand grains collected from the stream sediment load. These two micro-habitats exhibit a high community similarity (SIMI). The SIMI index also suggests that the flora of P. pertinax tubes is highly similar to that of sand grains. Diversity, however, is almost three times greater on P. pertinax tubes and SEM observations reveal that this microhabitat is characterized by a more spatially complex flora; Nitzschia and Navicula spp. dominate the upperstory, and O. martyi is located on underlying sand grains. Results indicate that tube-building chironomids in Carp Creek affect diatom microdistribution by: (1) stabilizing sand grains and associated flora within their retreats, (2) providing a ‘refugium’ for upperstory diatom taxa from the mayfly grazer, Baetis vagans McDunnough (Insecta: Ephemeroptera), and (3) through local nutrient enrichment.     

寡聚糖生物农药对棉花体内细菌数量和作物生长的作用

通过常规分离方法,测定寡聚糖生物农药对中棉12品种的棉茎体内细菌群落数量的影响。2批实验结果表明喷寡聚糖后棉茎体内细菌群落数量均低于对照,喷寡聚糖10d后棉茎体内细菌群落数量显著下降(8.0×10     

几个主要地面因子对草原群落蒸发蒸腾的影响

 在中国科学院内蒙古草原生态系统定位研究站,采用“土柱称重法”,观测了几个主要地面因子对草原群落蒸发蒸腾的影响。主要研究结果如下：1．土壤因子的影响：(1)在通常情况下,草原群落蒸发、蒸腾及蒸散均随土壤水分增加而增大;当土壤水分过多时,群落蒸腾由于植物受涝而降低。(2）在低土壤含水量条件下,群落蒸发随土壤粘粒含量增加呈线性降低;在高土壤含水量条件下,群落蒸发随土壤粘粒含量增加而升高。(3)不同土壤含水量的群落蒸发,均随土壤紧实度增大而升高,并先后达最高值。土壤含水量愈低,蒸发达最高值愈滞后。 2．放牧因素的影响：群落蒸腾与牧压呈线性负相关;群落蒸发与牧压呈线性正相关。群落生物量随牧压增大而降低是导致群落蒸发和蒸腾与牧压呈正、负相关的主要原因。 3．退化群落及其恢复群落的蒸发蒸腾：群落退化导致群落蒸发升高,蒸腾降低;相应的群落恢复导致群落蒸发降低,蒸腾升高。在—定程度上,群落退化及其恢复演替虽然能明显改变群落T／E值1）,但却不会引起群落蒸散值的明显变化。     

广东森林群落排序分析

本文应用极点排序和位置向量排序的方法对广东13个森林群落进行排序分析,并分别用极点排序图和位置向量排序的二维图和三维图表示排序的结果。同时对排序图的生态学意义及排序方法的优缺点进行讨论。结果表明,三维位置向量排序图能较好地把性质相近的群落类型聚在一起,可作为植被分类的辅助方法;积点排序图从一定程度上反映了植被的连续变化;极点排序与位置向量排序虽然取得一定结果,但由于同属线性排序,损失的信息量较多,寻求非线性排序方法是研究的方向。     

转基因鲤鱼与对照鲤肠道微生物群落差异研究

以转“全鱼”生长激素基因鲤(Cyprinus carpio L.)和野生对照鲤为对象, 采用454高通量测序技术对其肠道微生物16S rRNA基因进行测序并分析了3个不同发育阶段微生物群落结构的变化, 进而探讨了转基因鲤与对照鲤肠道微生物群落的差异。基于转基因鲤和对照鲤不同发育时期(6日龄、2月龄、5月龄)肠道微生物群落组成的DCA排序分析显示, 2月龄转基因鲤与对照鲤肠道微生物组成不同。Alpha多样性及均匀度都显示转基因鲤肠道微生物多样性高于对照鲤。从门水平的比较分析发现, 转基因鲤肠道中存在较多的厚壁菌门(Firmicutes)细菌, 而对照鲤中拟杆菌门(Bacteroidetes)细菌较多, 其中2月龄转基因鲤肠道内Bacteroidetes/Firmicutes比值低于对照鲤。研究结果表明, 在所分析的3个发育时期, 转基因鲤的肠道微生物组成与对照鲤相比发生了改变, 且在2月龄时存在差异。该研究为进一步揭示转基因鱼肠道微生物与宿主的相互影响和作用机制提供了很好的参考。     

放牧对内蒙古锡林河流域草地群落植物茎叶生物量资源分配的影响

以内蒙古锡林河流域沿水分梯度分布的灰脉苔草(Carex appendiculata)、贝加尔针茅(Stipa baicalensis)、羊草(Leymus chinensis)、大针茅(Stipa grandis)、小叶锦鸡儿(Caragana microphylla)和冷蒿(Artemisia frigida) 6个草地群落为对象, 研究了围封禁牧与放牧样地中144个共有植物种的高度、丛幅面积、茎、叶和株(丛)生物量、茎叶比等性状。结果表明: 1)在个体水平上, 放牧样地中植物的生殖枝高度、营养枝高度、丛幅面积、单株(丛)生物量、茎、叶生物量和茎叶比均显著低于围封禁牧样地, 植物在放牧干扰下表现出明显的小型化现象; 2)在群落水平上, 放牧亦显著降低了群落总生物量和茎、叶生物量; 3)过度放牧显著改变了物种的资源分配策略, 使生物量向叶的分配比例增加, 向茎的分配比例减少。资源优先向同化器官分配可能是植物对长期放牧干扰的一种重要适应对策; 4)轻度放牧对物种的资源分配没有显著影响, 单株(丛)生物量和群落茎、叶及总生物量均表现出增加趋势, 这与过度放牧的影响正好相反。过度放牧引起的植物个体小型化改变了生态系统中物种的资源分配策略, 进而对生态系统功能产生重要的影响。     

长江中游湖泊不同鱼类养殖方式对浮游植物群落的影响

为研究水产养殖对湖泊生态系统的影响, 于2015年7月至9月对长江中游23个湖泊的浮游植物群落及生物多样性情况进行了调查, 所研究的湖泊包括以下4组: 水库组(A组)、禁养组(B组)、低密度养殖组(C组)、高密度养殖组(D组)。结果显示, 4组湖泊的优势类群间存在一定差异。A组优势种有假鱼腥藻(Pseudanabaena, Y=0.642, Y为优势度)、浮鞘丝藻(Planktolyngbya, Y=0.064), B组优势种有平裂藻(Merismopedia, Y=0.428)、浮鞘丝藻(Planktolyngbya, Y=0.118)、假鱼腥藻(Pseudanabaena, Y=0.133)、栅藻(Scenedesmus, Y=0.066), C组优势种为假鱼腥藻(Pseudanabaen, Y=0.395)、平裂藻(Merismopedia, Y=0.097)、浮鞘丝藻(Planktolyngbya, Y=0.122), D组的优势种为平裂藻(Merismopedia, Y=0.308)、微囊藻(Microcystis, Y=0.118)、假鱼腥藻(Pseudanabaena, Y=0.077)。A组浮游植物丰度显著低于B组、C组及D组(P<0.05)。各组间浮游植物群落的Shannon-Wiener多样性指数、Margalef丰富度指数及Pielou均匀度指数均不存在明显差异。研究表明鱼类养殖对湖泊浮游植物的丰度及优势类群会产生影响, 对湖泊生态系统的管理具有一定的参考意义。     

东湖异养细菌群落的分类结构和聚类分析

对东湖异养细菌群落结构采用系统分类和微机聚类分析方法作了比较研究。169株由东湖Ⅰ、Ⅱ、Ⅲ站水体中分离的异养细菌分别隶属于30个细菌属。其中以芽孢杆菌属居于明显优势,其次是微球菌属。在不同水域或水层,细菌的分布表现有一定的差别,但各站间多样性指数值没有明显的差异。基于113项生物学特性检测结果,采用lBM PC/XT微机聚类分析后计算各站细菌的多样性指数发现:Ⅰ站明显高于Ⅱ、Ⅲ两站,43项检测系统所得结果与此表现了一致的趋势。这与东湖各站水环境的理化分析参数是比较吻合的。作者对以上结果作了讨论。