Energetically relevant predator–prey body mass ratios and their relationship with predator body size

Food web structure and dynamics depend on relationships between body sizes of predators and their prey. Species‐based and community‐wide estimates of preferred and realized predator–prey mass ratios (PPMR) are required inputs to size‐based size spectrum models of marine communities, food webs, and ecosystems. Here, we clarify differences between PPMR definitions in different size spectrum models, in particular differences between PPMR measurements weighting prey abundance in individual predators by biomass (r^bio) and numbers (r^num). We argue that the former weighting generates PPMR as usually conceptualized in equilibrium (static) size spectrum models while the latter usually applies to dynamic models. We use diet information from 170,689 individuals of 34 species of fish in Alaskan marine ecosystems to calculate both PPMR metrics. Using hierarchical models, we examine how explained variance in these metrics changed with predator body size, predator taxonomic resolution, and spatial resolution. In the hierarchical analysis, variance in both metrics emerged primarily at the species level and substantially less variance was associated with other (higher) taxonomic levels or with spatial resolution. This suggests that changes in species composition are the main drivers of community‐wide mean PPMR. At all levels of analysis, relationships between weighted mean r^bio or weighted mean r^num and predator mass tended to be dome‐shaped. Weighted mean r^num values, for species and community‐wide, were approximately an order of magnitude higher than weighted mean r^bio, reflecting the consistent numeric dominance of small prey in predator diets. As well as increasing understanding of the drivers of variation in PPMR and providing estimates of PPMR in the north Pacific Ocean, our results demonstrate that that r^bio or r^num, as well as their corresponding weighted means for any defined group of predators, are not directly substitutable. When developing equilibrium size‐based models based on bulk energy flux or comparing PPMR estimates derived from the relationship between body mass and trophic level with those based on diet analysis, weighted mean r^bio is a more appropriate measure of PPMR. When calibrating preference PPMR in dynamic size spectrum models then weighted mean r^num will be a more appropriate measure of PPMR.     

Vulnerability of the global terrestrial ecosystems to climate change

Climate change has far‐reaching impacts on ecosystems. Recent attempts to quantify such impacts focus on measuring exposure to climate change but largely ignore ecosystem resistance and resilience, which may also affect the vulnerability outcomes. In this study, the relative vulnerability of global terrestrial ecosystems to short‐term climate variability was assessed by simultaneously integrating exposure, sensitivity, and resilience at a high spatial resolution (0.05°). The results show that vulnerable areas are currently distributed primarily in plains. Responses to climate change vary among ecosystems and deserts and xeric shrublands are the most vulnerable biomes. Global vulnerability patterns are determined largely by exposure, while ecosystem sensitivity and resilience may exacerbate or alleviate external climate pressures at local scales; there is a highly significant negative correlation between exposure and sensitivity. Globally, 61.31% of the terrestrial vegetated area is capable of mitigating climate change impacts and those areas are concentrated in polar regions, boreal forests, tropical rainforests, and intact forests. Under current sensitivity and resilience conditions, vulnerable areas are projected to develop in high Northern Hemisphere latitudes in the future. The results suggest that integrating all three aspects of vulnerability (exposure, sensitivity, and resilience) may offer more comprehensive and spatially explicit adaptation strategies to reduce the impacts of climate change on terrestrial ecosystems.     

Ecosystem size structure response to 21st century climate projection: large fish abundance decreases in the central North Pacific and increases in the California Current

Output from an earth system model is paired with a size‐based food web model to investigate the effects of climate change on the abundance of large fish over the 21st century. The earth system model, forced by the Intergovernmental Panel on Climate Change (IPCC) Special report on emission scenario A2, combines a coupled climate model with a biogeochemical model including major nutrients, three phytoplankton functional groups, and zooplankton grazing. The size‐based food web model includes linkages between two size‐structured pelagic communities: primary producers and consumers. Our investigation focuses on seven sites in the North Pacific, each highlighting a specific aspect of projected climate change, and includes top‐down ecosystem depletion through fishing. We project declines in large fish abundance ranging from 0 to 75.8% in the central North Pacific and increases of up to 43.0% in the California Current (CC) region over the 21st century in response to change in phytoplankton size structure and direct physiological effects. We find that fish abundance is especially sensitive to projected changes in large phytoplankton density and our model projects changes in the abundance of large fish being of the same order of magnitude as changes in the abundance of large phytoplankton. Thus, studies that address only climate‐induced impacts to primary production without including changes to phytoplankton size structure may not adequately project ecosystem responses.     

Damped trophic cascades driven by fishing in model marine ecosystems

The largest perturbation on upper trophic levels of many marine ecosystems stems from fishing. The reaction of the ecosystem goes beyond the trophic levels directly targeted by the fishery. This reaction has been described either as a change in slope of the overall size spectrum or as a trophic cascade triggered by the removal of top predators. Here we use a novel size- and trait-based model to explore how marine ecosystems might react to perturbations from different types of fishing pressure. The model explicitly resolves the whole life history of fish, from larvae to adults. The results show that fishing does not change the overall slope of the size spectrum, but depletes the largest individuals and induces trophic cascades. A trophic cascade can propagate both up and down in trophic levels driven by a combination of changes in predation mortality and food limitation. The cascade is damped as it comes further away from the perturbed trophic level. Fishing on several trophic levels leads to a disappearance of the signature of the trophic cascade. Differences in fishing patterns among ecosystems might influence whether a trophic cascade is observed.     

Effect of phytoplankton size diversity on primary productivity in the North Pacific: trait distributions under environmental variability

While most biodiversity and ecosystem functioning (BEF) studies have found positive effects of species richness on productivity, it remain unclear whether similar patterns hold for marine phytoplankton with high local richness. We use the continuous trait‐based modelling approach, which assumes infinite richness and represents diversity in terms of the variance of the size distribution, to investigate the effects of phytoplankton size diversity on productivity in a three‐dimensional ocean circulation model driven by realistic physics forcing. We find a slightly negative effect of size diversity on primary production, which we attribute to several factors including functional trait‐environment interactions, flexible stoichiometry and the saturation of productivity at low diversity levels. The benefits of trait optimisation, whereby narrow size distributions enhance productivity under relatively stable conditions, tend to dominate over those of adaptive capacity, whereby greater diversity enhances the ability of the community to respond to environmental variability.     

Replacement of large copepods by small ones with eutrophication of embayments: cause and consequence

Species and size compositions of the planktonic copepod community were compared between two eutrophic embayments, Tokyo Bay and Osaka Bay. Within these bays, the median body weight of the community was lowest at the innermost station and increased gradually offshore. In Tokyo Bay, which is more eutrophic than Osaka Bay, the dominant species was Oithona davisae and the median carbon weight of the community was ca 0.1 µg. In Osaka Bay, Paracalanus sp., Calanus sinicus and Corycaeus spp. were dominant and the median weight was 1–2 order of magnitude higher (2–78 µg) than in Tokyo Bay. Some 40 years ago, when eutrophication was less prominent, Acartia omorii, Paracalanus sp. and Microsetella norvegica comprised a considerable portion of the community in Tokyo Bay. The proliferation of O. davisae might have been caused with the recent change in food particle composition and/or dissociated life cycle of this species from the benthic anoxic layer. Decrease in the size composition of the copepod community may make the embayment ecosystem unfavorable for planktivorous fish, but not for jellyfish, e.g. Aurelia and Bolinopsis. This may also result in an acceleration of the flux of biogenic materials from the embayment to the outer ocean.     

Experimental evidence of gradual size‐dependent shifts in body size and growth of fish in response to warming

A challenge facing ecologists trying to predict responses to climate change is the few recent analogous conditions to use for comparison. For example, negative relationships between ectotherm body size and temperature are common both across natural thermal gradients and in small‐scale experiments. However, it is unknown if short‐term body size responses are representative of long‐term responses. Moreover, to understand population responses to warming, we must recognize that individual responses to temperature may vary over ontogeny. To enable predictions of how climate warming may affect natural populations, we therefore ask how body size and growth may shift in response to increased temperature over life history, and whether short‐ and long‐term growth responses differ. We addressed these questions using a unique setup with multidecadal artificial heating of an enclosed coastal bay in the Baltic Sea and an adjacent reference area (both with unexploited populations), using before‐after control‐impact paired time‐series analyses. We assembled individual growth trajectories of ~13,000 unique individuals of Eurasian perch and found that body growth increased substantially after warming, but the extent depended on body size: Only among small‐bodied perch did growth increase with temperature. Moreover, the strength of this response gradually increased over the 24 year warming period. Our study offers a unique example of how warming can affect fish populations over multiple generations, resulting in gradual changes in body growth, varying as organisms develop. Although increased juvenile growth rates are in line with predictions of the temperature–size rule, the fact that a larger body size at age was maintained over life history contrasts to that same rule. Because the artificially heated area is a contemporary system mimicking a warmer sea, our findings can aid predictions of fish responses to further warming, taking into account that growth responses may vary both over an individual's life history and over time.     

2001—2010年疏勒河流域生态系统质量综合评价

疏勒河流域属于典型的干旱区内陆河流域,生态环境脆弱,对其进行生态系统质量评价意义重大.本文利用多源遥感数据,依据生态系统生产能力指数(EPI)/生态系统稳定性指数(ESI)/生态系统承载力指数(EBCI),建立遥感综合评价模型,对疏勒河流域2001—2010年的生态系统质量进行综合评价.结果表明: 疏勒河流域2001—2010年生态系统质量平均值为43.21,处于较低水平.EPI、ESI和EBCI的均值分别为47.16、58.09和28.52,说明疏勒河流域生态系统承载力较低.2001—2010年,EPI和EBCI分别增加了18.9％和20.1％,ESI下降了9.4％.流域生态系统质量总体呈现出先增加后下降的趋势,2001、2005和2010年生态系统质量年均值分别为 43.71、44.80和41.13.农田生态系统质量最高,水体生态系统质量最低.人工生态系统质量综合评价值为46.43,明显高于自然生态系统.     

生态系统服务价值的市场转化问题初探

为生态系统服务寻找建立特定的、真实的市场环境,将生态系统服务的间接价值转化为直接的经济价值,既有利于区域经济的发展,又可促进人们对生态系统服务功能的维持和保护。提出了生态系统服务价值的市场转化(率)概念,即生态系统服务价值市场转化是指为生态系统服务价值寻找建立特定的、真实的市场环境,使一些生态系统服务能够像普通商品一样进入市场流通,转化为直接的经济价值;而生态系统服务价值市场转化率(Cr)就是能够进入市场流通的服务价值(Va)占生态系统总服务价值(Vg)的比例。阐述了市场转化(率)的应用意义。在此基础上分析了全球及我国各类生态系统服务价值的市场转化情况,并提出了将来的发展思路。     

Capitalizing on nature: how to implement an ecosystem approach

The Natural Capital Initiative (www.naturalcapitalinitiative.org.uk) held its first conference ‘Valuing our life support systems’ at Savoy Place, London, from 29 April to 1 May 2009. The aim of the conference was to discuss different perspectives on, and solutions to, the conservation and sustainable use of ecosystem services. It particularly focused on the link between the environment and the economy, and how to implement an ecosystem approach to environmental management. This event brought together scientists across the natural and social sciences, alongside representatives from government, non-governmental organizations, business and industry.     

恢复生态学——退化生态系统生物多样性恢复的有效途径

人类在改造和利用自然的过程中 ,伴随着对自然环境产生负面的影响 ,这种影响以不同的时空规模出现。某些工业上的突发性事件 ,如前苏联的切尔诺贝尔核电站事故 ,巨大油轮的泄油事件等 ,均可在较大的范围且往往是在有限的区域内引起剧烈的生态变动 ,这种灾难性的环境变化随即会对生物多样性产生影响 ;另一种规模的人类活动的影响所引起的变化 ,如长期的工业污染 ,大规模的森林砍伐以及将大范围的自然生境逐渐转变成农业和工业景观 ,则是逐年的、跨区域的、甚至波及整个大陆 ,但这种变化对生物多样性的影响会持续更长的时间 ,因为某些种类会由…     

Integrating trait‐based empirical and modeling research to improve ecological restoration

A global ecological restoration agenda has led to ambitious programs in environmental policy to mitigate declines in biodiversity and ecosystem services. Current restoration programs can incompletely return desired ecosystem service levels, while resilience of restored ecosystems to future threats is unknown. It is therefore essential to advance understanding and better utilize knowledge from ecological literature in restoration approaches. We identified an incomplete linkage between global change ecology, ecosystem function research, and restoration ecology. This gap impedes a full understanding of the interactive effects of changing environmental factors on the long‐term provision of ecosystem functions and a quantification of trade‐offs and synergies among multiple services. Approaches that account for the effects of multiple changing factors on the composition of plant traits and their direct and indirect impact on the provision of ecosystem functions and services can close this gap. However, studies on this multilayered relationship are currently missing. We therefore propose an integrated restoration agenda complementing trait‐based empirical studies with simulation modeling. We introduce an ongoing case study to demonstrate how this framework could allow systematic assessment of the impacts of interacting environmental factors on long‐term service provisioning. Our proposed agenda will benefit restoration programs by suggesting plant species compositions with specific traits that maximize the supply of multiple ecosystem services in the long term. Once the suggested compositions have been implemented in actual restoration projects, these assemblages should be monitored to assess whether they are resilient as well as to improve model parameterization. Additionally, the integration of empirical and simulation modeling research can improve global outcomes by raising the awareness of which restoration goals can be achieved, due to the quantification of trade‐offs and synergies among ecosystem services under a wide range of environmental conditions.     

城市污泥应用于陆地生态系统研究进展

随着城市化进程加快和人口剧增,城市污泥已成为世界许多城市面临的主要环境问题之一,且不合理的管理可引发严重的环境污染.城市污泥含有大量、微量元素和有机质,可能对土壤及其生产力有利,特别对退化土壤能进行有机修复,并改善土壤理化特性,譬如土壤结构和营养含量.目前,污泥作为一种有机肥料已成为普遍措施.但来自工业及生活污水的污泥常含有重金属、病原物及有毒有机物等,潜在的毒性可能对生态系统构成危险,因此必须经过污泥预处理才可安全施用.评述了近年来国内外污泥应用于陆地生态系统4个方面的主要研究进展:(1)污泥处理与处置方法;(2)污泥应用于农田、草地及森林生态系统;(3)污泥对土壤生态系统的影响,包括污泥对土壤理化性质、土壤酶及微生物的影响;(4)污泥应用的环境效应.提出未来我国污泥处置及利用需要重视的研究领域和方向.     

Effects of organism size and community composition on ecosystem functioning

We tested (1) if the size of dominant species influenced ecosystem functioning in food webs consisting of bacteria, algae, and protozoa; (2) whether those effects changed in importance through time; and (3) how those effects compared with differences in diversity among experimental food webs. We constructed food webs using two size fractions of organisms that differed in individual mass by approximately two orders of magnitude. We measured total biomass and respiration (total CO₂ production) as two aspects of ecosystem functioning. We also compared these size‐dependent patterns in functioning across two levels of species richness. Initially, organism size strongly influenced total community biomass. With time, however, biomass and respiration eventually converged in communities dominated by large or small species. We conclude that after sufficient time for community development any differences in ecosystem functioning resulted from differences in community composition, including species richness, but not the size of the dominant organisms.     

代谢异速生长理论及其在微生物生态学领域的应用

新陈代谢是生物的基本生理过程,影响生物在不同环境中参与物质循环和能量转化的过程.代谢速率作为生物体重要的生命过程指标,几乎影响所有的生物活性速率,且在很多研究中均表现出异速生长现象.所谓代谢异速是指生物体代谢速率与其个体大小(或质量)之间存在的幂函数关系.代谢异速生长理论的提出,从机制模型角度解释了代谢异速关系这一普遍存在的生命现象.该理论利用分形几何学及流体动力学等原理,从生物能量学角度阐释了异速生长规律的机理,证实了3/4权度指数的存在;但同时有研究表明,权度指数因环境因素等影响处于2/3-1范围之间而非定值.随着研究工作的深入,代谢异速生长理论研究从起初的宏观动植物领域拓展到了微生物领域,在研究微生物的代谢异速生长理论时,可将微生物的可操作分类单元(Operational taxonomic unit,OTU)或具有特定功能的功能群视为一个微生物个体,基于其遗传多样性和功能多样性特征进行表征,以便于将微生物群落多样性与其生态功能性联系起来,使该理论在微生物生态学领域得到有效的补充和完善.尽管细菌具有独特的生物学特性,但与宏观生物系统中观测到的现象表现出明显的一致性.有研究表明,3个农田土壤细菌基于遗传多样性的OTU数的平均周转率分别为0.71、0.80和0.84,介于2/3与1之间,可能与生物代谢异速指数有一定关联,为微生物代谢异速指数的研究提出了一个参考解决方案.鉴于微生物个体特征和生物学特性,在分析代谢速率与个体大小关系中,从微生物单位个体的定义、个体大小表征到计量单位的统一,仍需更多的理论支持.分析了代谢异速生长理论在微生物与生态系统功能关系研究中的可能应用,延伸了该理论的应用范围,并对尚待加强的研究问题进行了评述和展望.     

Population dynamics of the long-snouted seahorse (Hippocampus guttulatus Cuvier, 1829) in the Mar Menor coastal lagoon

A 10-year monitoring program was developed to quantify the population dynamics of the long-snouted seahorse population in the Mar Menor coastal lagoon. Based on 985 underwater visual censuses, we estimated the long-snouted seahorse (Hippocampus guttulatus Cuvier, 1829) population size in the Mar Menor lagoon and its reduction in size in the last decades, as well as the effect of eutrophication crises in 2016 and 2019 on the species. The annual recruitment for the 2013–2020 period was estimated by comparing the relative abundance of early seahorse life stages in the ichthyoplankton. The density ranged from 0.0458 specimens/m³ at the beginning of the sampling period to 0.0004 at the end, showing a statistically significant difference between the three analyzed periods (H_gl=2 = 14.0, p = 0.001). The long-snouted seahorse population from the Mar Menor lagoon exemplifies the impact of fishing activities and human pressure, especially euxinic episodes and habitat destruction. As a result of this, the Mar Menor population has decreased from several million specimens to a few thousand, in only three decades. This species showed considerable resilience, the seahorse population began to recover once fishing activity stopped. In contrast, the long-snouted seahorse showed high vulnerability to habitat loss and an episodic flooding event. Adult seahorses showed preferences for highly complex habitats, especially Caulerpa prolifera–Cymodocea nodosa mixed meadows and habitats of high complexity and anthropogenic origin, such as harbors, jetties, or breakwaters. In contrast, juvenile seahorses preferred monotonous seabeds with low complexity, such as the sandy beds that are characteristic of the Mar Menor lagoon littoral.     

Warming alters community size structure and ecosystem functioning

Global warming can affect all levels of biological complexity, though we currently understand least about its potential impact on communities and ecosystems. At the ecosystem level, warming has the capacity to alter the structure of communities and the rates of key ecosystem processes they mediate. Here we assessed the effects of a 4°C rise in temperature on the size structure and taxonomic composition of benthic communities in aquatic mesocosms, and the rates of detrital decomposition they mediated. Warming had no effect on biodiversity, but altered community size structure in two ways. In spring, warmer systems exhibited steeper size spectra driven by declines in total community biomass and the proportion of large organisms. By contrast, in autumn, warmer systems had shallower size spectra driven by elevated total community biomass and a greater proportion of large organisms. Community-level shifts were mirrored by changes in decomposition rates. Temperature-corrected microbial and macrofaunal decomposition rates reflected the shifts in community structure and were strongly correlated with biomass across mesocosms. Our study demonstrates that the 4°C rise in temperature expected by the end of the century has the potential to alter the structure and functioning of aquatic ecosystems profoundly, as well as the intimate linkages between these levels of ecological organization.