The igneous oceanic crust – Earth's largest fungal habitat?

In recent years the igneous oceanic crust has been recognized as a substantial microbial habitat and a scientific frontier within Geology, Biology, and Oceanography. A few successful metagenomic investigations have indicated the presence of Archaea and Bacteria, but also fungi in the subseafloor igneous crust. A comprehensive fossil record supports the presence of fungi in these deep environments and provides means of investigating the fungal presence that complements metagenomic methods. Considering the vast volume of the oceanic crust and that it is the largest aquifer on Earth, we put forward that it is the largest fungal habitat on the planet. This review aims to introduce a yet unexplored fungal habitat in an environment considered extreme from a biological perspective. We present the current knowledge of fungal abundance and diversity and discuss the ecological role of fungi in the igneous oceanic crust.     

Chaos and the (un)predictability of evolution in a changing environment

Among the factors that may reduce the predictability of evolution, chaos, characterized by a strong dependence on initial conditions, has received much less attention than randomness due to genetic drift or environmental stochasticity. It was recently shown that chaos in phenotypic evolution arises commonly under frequency‐dependent selection caused by competitive interactions mediated by many traits. This result has been used to argue that chaos should often make evolutionary dynamics unpredictable. However, populations also evolve largely in response to external changing environments, and such environmental forcing is likely to influence the outcome of evolution in systems prone to chaos. We investigate how a changing environment causing oscillations of an optimal phenotype interacts with the internal dynamics of an eco‐evolutionary system that would be chaotic in a constant environment. We show that strong environmental forcing can improve the predictability of evolution by reducing the probability of chaos arising, and by dampening the magnitude of chaotic oscillations. In contrast, weak forcing can increase the probability of chaos, but it also causes evolutionary trajectories to track the environment more closely. Overall, our results indicate that, although chaos may occur in evolution, it does not necessarily undermine its predictability.     

Ecology and habitats of extremophiles

This review describes the main natural extreme environments, characterized by high temperature, high and low pH and high salinity, that can be colonized by microorganisms. The environments covered are: freshwater alkaline hot springs; acidic solfatara fields; anaerobic geothermal mud and soils; acidic sulphur and pyrite areas; carbonate springs and alkaline soil; and soda and highly saline lakes. The community structure, in terms of available energy sources and representative autotrophic and heterotrophic microorganisms, is discussed for each type of habitat.The authors are with the Department of Biotechnology. Technological Institute of Iceland, Keldnaholt, 112 Reykjavik, Iceland and with the Institute of Biology, University of Iceland, Reykjavik, Iceland     

Some effects of light on the viability of rhodopsin-containing halobacteria

Under starvation conditions, rhodopsin-containing halobacteria show a light-accelerated death under aerobic conditions. This is attributed to photooxidative processes. Under anaerobic conditions, halobacteria die rapidly in the dark, and light prevents death. Since it has been shown by others that lightdriven ATP synthesis can occur under anaerobic conditions, it is postulated that rhodopsin-mediated photophorylation is of survival value for this organism in the brines in which it lives, especially because the solubility of oxygen is low in highly saline waters and anaerobic conditions can often develop.     

Disturbance and patch-specific responses: the interactive effects of woody debris and floods on lotic invertebrates

Disturbance may play an important role in generating patterns of abundance and distribution of biotic assemblages, particularly if its impact differs among habitat patches. Despite much speculation concerning the probable importance of spatial variation in the response of stream fauna to flooding, empirical work on patch-specific responses to spates is largely lacking. Floods typically reduce the abundance of lotic invertebrates dramatically in open-channel areas. We conducted a set of experiments to determine if faunal abundances are less affected in patches more sheltered due to the presence of woody debris dams. Specifically, we tested two hypotheses using chironomids and copepods living in a warmwater, 4th order stream: (1) the effect of flooding on the fauna varies between patches associated with debris dams versus the open channel, and (2) the absence of woody debris in a stream impedes faunal recovery throughout the channel following floods. We tested the first hypothesis by quantifying faunal abundances prior to, during, and following two floods in four patch types: mid-channel sandy patches distant from dams, coarse sediments associated with dams, fine sediments associated with dams, and leafy debris in dams. The second hypothesis was tested by removing all of the woody debris from two stretches of the stream and comparing the impact of a flood on fauna in debris-removed versus control stretches. Across all of the eight study dams, there were patchspecific faunal responses to two floods. Removal of woody debris from the stream did not prevent faunal recovery throughout the channel; however, the presence of woody debris dams did confer greater resistance of fauna to floods (as measured by no decrease in abundance during flooding) in two patch types. Abundances of chironomids and, to a lesser extent, copepods in the leafy debris of dams and in fine sediment patches associated with some dams either did not change or increased during floods, despite the fact that abundances in the dominant patch type of the stream (the sandy mid-channel) were reduced by 75–95%. All instances of faunal increase were limited to fine sediment patches associated with dams, thus entire dams cannot be labeled as flow refugia per se. Statistically, we distinguished fine patches which accumulated animals during floods from the other fine patches based on two physical attributes. Patches accumulating animals were all characterized by low water flux and nearbed flow, which likely contributed to the retention and/or passive deposition of animals. Whole dam attributes (e.g. dam size or complexity) were not useful in predicting which of the dams would accumulate animals in their fine sediments during flooding. Although structural complexity — here in the form of wood and leafy debris — is clearly important in generating biotic pattern in many ecosystems, our work underscores the need to understand what processes are responsible for the link between physical structure and biotic pattern.     

鄱阳湖生态经济区资源环境综合承载力评价

随着社会经济的发展,人口、资源与环境之间的矛盾日趋加剧.因此,资源环境承载力问题成为各国（地区）政府所关注的焦点问题之一.本文通过对鄱阳湖生态经济区内资源、环境的现状及问题进行调查分析,选取土地资源、水资源、生物资源、矿产资源、生态-地质环境、水环境及大气环境作为评价准则层,在对上述7个单因素进行评价基础之上,以县（市、区）为评价单位,采用状态空间法对全区的资源环境承载力进行综合评价.结果表明：当前全区内生物资源较丰富,大气、水环境质量良好,地质环境整体较稳定,制约因素主要为土地资源、水资源和矿产资源;全区资源环境承载力表现为可载状态,但部分县（市、区）表现为超载状态.利用状态空间法进行区域资源环境综合承载力研究是可行的,具有意义明确、评价精度高等优点,可为区域资源环境综合承载力评价提供另一种途径.     

Enhancing the performance and interpretation of freshwater biological indices: An application in arid zone streams

We assessed the performance of biological indices developed for invertebrate assemblages occurring in arid zone streams: a multimetric index (MMI) and an O/E index of taxonomic completeness. Our overall goal was to advance our understanding of the factors that affect performance and interpretation of biological indices. Our specific objectives were to (1) develop biological indices that are insensitive to natural environmental gradients, (2) develop a general method to determine if the biological potential of an assessed site is adequately represented by the population of reference sites, (3) develop a robust method to select metrics for inclusion in MMIs that ensures maximum independence of metrics, and (4) determine if a fundamental sample property (the evenness of taxa counts within a sample) affects index performance. Random Forest modeling revealed that both individual metrics and taxa composition were strongly associated with natural environmental heterogeneity, which meant both the MMI and O/E index needed to be based on site-specific expectations. We produced a precise, responsive, and ecologically robust MMI by using principal components analysis to identify 7 statistically independent metrics from a list of 31 candidate assemblage-level metrics. However, the O/E index we developed was relatively imprecise compared with O/E indices developed for other regions. This imprecision may be the consequence of low predictability in local taxa composition associated with the relatively high spatial isolation of aquatic habitats within arid regions. We were also able to assess the likelihood that the biological potential of assessed sites were adequately characterized by the population of reference sites by developing and applying a multivariate, nearest-neighbor test that determined if an assessed site occurred within the environmental space of the reference site network. This approach is robust and applicable to all biological indices. We also demonstrate that the evenness of taxa counts within a sample is positively related to estimates of sample taxa richness and thus the scores of both indices. The relationship between richness and sample evenness can potentially compromise inferences regarding biological condition, and post hoc adjustments for the effects of evenness on index scores might be desirable. Further improvements in the performance and interpretation of biological indices will require simultaneous consideration of the effects of incomplete sampling on characterization of biological assemblages and the physical and biological factors that influence community assembly.     

Long-term fire frequency variability in the eastern Canadian boreal forest: the influences of climate vs. local factors

The influence of climatic and local nonclimatic factors on the fire regime of the eastern Canadian boreal forest over the last 8000 years is investigated by examining charred particles preserved in four lacustrine deposits. Herein, we compare the distribution of fire-free intervals (FFIs) and the synchronicity of fire events among sites, using Ripley's K -function to determine the extent of the role of local-scale vs. large-scale processes with respect to fire control. Between 8000 and 5800 cal. bp (calibrated years before present) the climatic and ecological conditions were less conducive to fire events than after this date. After 5800 cal. bp , the number of fires per 1000 years (fire frequency) progressively increased, reaching a maximum ca. 3400 cal. bp . There was a sharp decrease in fire frequency during the last 800 years. Between 8000 and 4000 cal. bp , comparable FFIs and synchronous fire episodes were determined for the study sites. During this period, the fire frequency was predominantly controlled by climate. After 4000 cal. bp , two sites displayed independent fire histories (different FFI distributions or asynchronous fire events), underlining the important influence of local factors, including short-term fuel wetness, characteristics of the watershed and landscape connectivity, in determining fire occurrence. We conclude that climatic changes occurred during the last 4000 years that induced a rise in the water table; this may explain the high spatial heterogeneity in fire history. Current and projected global climatic changes may cause similar spatial variability in fire frequency.     

River Otter Latrine Site Selection in Arid Habitats of Western Colorado,USA

ABSTRACT River otters (Lontra canadensis) select specific habitat features when establishing latrines, but no studies have described latrine features in arid and semiarid environments. We developed a model describing those habitat features that influence otter latrine site selection on rivers in arid and semiarid watersheds of western Colorado, USA. River otters selected latrine sites with the presence of beaver (Castor canadensis) activity, large prominent rocks, adjacent to deeper water, with shading over the site, and rock or cliff overstory. Our model provides a robust predictive tool for identifying river otter latrine sites in arid environments of southwestern North America.