The Intergovernmental Panel on Climate Change (IPCC) Technical Paper Climate Change and Water draws together and evaluates the information in IPCC Assessment and Special Reports concerning the impacts of climate change on hydrological processes and regimes, and on freshwater resources – their availability, quality, use and management. It takes into account current and projected regional key vulnerabilities, prospects for adaptation, and the relationships between climate change mitigation and water. Its objectives are:

/pdf/climate-change-and-water-2dpc0zbpsj.pdf

Climate change and water.

1 Plant ecology at high elevations.- The concept of limitation.- A regional and historical account.- The challenge of alpine plant research.- 2 The alpine life zone.- Altitudinal boundaries.- Global alpine land area.- Alpine plant diversity.- Origin of alpine floras.- Alpine growth forms.- 3 Alpine climate.- Which alpine climate.- Common features of alpine climates.- Regional features of alpine climates.- 4 The climate plants experience.- Interactions of relief, wind and sun.- How alpine plants influence their climate.- The geographic variation of alpine climate.- 5 Life under snow: protection and limitation.- Temperatures under snow.- Solar radiation under snow.- Gas concentrations under snow.- Plant responses to snowpack.- 6 Alpine soils.- Physics of alpine soil formation.- The organic compound.- The interaction of organic and inorganic compounds.- 7 Alpine treelines.- About trees and lines.- Current altitudinal positions of climatic treelines.- Treeline-climate relationships.- Intrazonal variations and pantropical plateauing of alpine treelines.- Treelines in the past.- Attempts at a functional explanation of treelines.- A hypothesis for treeline formation.- Growth trends near treelines.- Evidence for sink limitation.- 8 Climatic stress.- Survival of low temperature extremes.- Avoidance and tolerance of low temperature extremes.- Heat stress in alpine plants.- Ultraviolet radiation - a stress factor.- 9 Water relations.- Ecosystem water balance.- Soil moisture at high altitudes.- Plant water relations - a brief review of principles.- Water relations of alpine plants.- Desiccation stress.- Water relations of special plant types.- 10 Mineral nutrition.- Soil nutrients.- The nutrient status of alpine plants.- Nutrient cycling and nutrient budgets.- Nitrogen fixation.- Mycorrhiza.- Responses of vegetation to variable nutrient supply.- 11 Uptake and loss of carbon.- Photosynthetic capacity of alpine plants.- Photosynthetic responses to the environment.- Daily carbon gain of leaves.- The seasonal carbon gain of leaves.- C4 and CAM photosynthesis at high altitudes.- Tissue respiration of alpine plants.- Ecosystem carbon balance.- 12 Carbon investments.- Non-structural carbohydrates.- Lipids and energy content.- Carbon costs of leaves and roots.- Whole plant carbon allocation.- 13 Growth dynamics and phenology.- Seasonal growth.- Diurnal leaf extension.- Rates of plant dry matter accumulation.- Functional duration of leaves and roots.- 14 Cell division and tissue formation.- Cell size and plant size.- Mitosis and the cell cycle.- From meristem activity to growth control.- 15 Plant biomass production.- The structure of alpine plant canopies.- Primary productivity of alpine vegetation.- Plant dry matter pools.- Biomass losses through herbivores.- 16 Plant reproduction.- Flowering and pollination.- Seed development and seed size.- Germination.- Alpine seed banks and natural recruitment.- Clonal propagation.- Alpine plant age.- Community processes.- 17 Global change at high elevation.- Alpine land use.- The impact of altered atmospheric chemistry.- Climatic change and alpine ecosystems.- References (with chapter annotation).- Taxonomic index (genera).- Geographical index.- Color plates.- Plant life forms.- The alpine life zone.- Environmental stress.- The human dimension.

Alpine plant life

The Domain-specific Probe EUB338 is Insufficient for the Detection of all Bacteria: Development and Evaluation of a more Comprehensive Probe Set

The discovery that viruses may be the most abundant organisms in natural waters, surpassing the number of bacteria by an order of magnitude, has inspired a resurgence of interest in viruses in the aquatic environment. Surprisingly little was known of the interaction of viruses and their hosts in nature. In the decade since the reports of extraordinarily large virus populations were published, enumeration of viruses in aquatic environments has demonstrated that the virioplankton are dynamic components of the plankton, changing dramatically in number with geographical location and season. The evidence to date suggests that virioplankton communities are composed principally of bacteriophages and, to a lesser extent, eukaryotic algal viruses. The influence of viral infection and lysis on bacterial and phytoplankton host communities was measurable after new methods were developed and prior knowledge of bacteriophage biology was incorporated into concepts of parasite and host community interactions. The new methods have yielded data showing that viral infection can have a significant impact on bacteria and unicellular algae populations and supporting the hypothesis that viruses play a significant role in microbial food webs. Besides predation limiting bacteria and phytoplankton populations, the specific nature of virus-host interaction raises the intriguing possibility that viral infection influences the structure and diversity of aquatic microbial communities. Novel applications of molecular genetic techniques have provided good evidence that viral infection can significantly influence the composition and diversity of aquatic microbial communities.

/pdf/virioplankton-viruses-in-aquatic-ecosystems-30m49tuwrn.pdf

Virioplankton: viruses in aquatic ecosystems

The finding that total viral abundance is higher than total prokaryotic abundance and that a significant fraction of the prokaryotic community is infected with phages in aquatic systems has stimulated research on the ecology of prokaryotic viruses and their role in ecosystems. This review treats the ecology of prokaryotic viruses ('phages') in marine, freshwater and soil systems from a 'virus point of view'. The abundance of viruses varies strongly in different environments and is related to bacterial abundance or activity suggesting that the majority of the viruses found in the environment are typically phages. Data on phage diversity are sparse but indicate that phages are extremely diverse in natural systems. Lytic phages are predators of prokaryotes, whereas lysogenic and chronic infections represent a parasitic interaction. Some forms of lysogeny might be described best as mutualism. The little existing ecological data on phage populations indicate a large variety of environmental niches and survival strategies. The host cell is the main resource for phages and the resource quality, i.e., the metabolic state of the host cell, is a critical factor in all steps of the phage life cycle. Virus-induced mortality of prokaryotes varies strongly on a temporal and spatial scale and shows that phages can be important predators of bacterioplankton. This mortality and the release of cell lysis products into the environment can strongly influence microbial food web processes and biogeochemical cycles. Phages can also affect host diversity, e.g., by 'killing the winner' and keeping in check competitively dominant species or populations. Moreover, they mediate gene transfer between prokaryotes, but this remains largely unknown in the environment. Genomics or proteomics are providing us now with powerful tools in phage ecology, but final testing will have to be performed in the environment.

Ecology of prokaryotic viruses

The diatom distribution in the sediment of four alpine lakes in the central alpine area (Otztaler Alpen, Tyrolia, and Molltal, Carinthia) has been analysed in order to assess possible influences of atmospheric pollutants on remote lakes. The lakes are located more than 2000 m above sea level on poorly buffered bedrock (granite, gneiss and mica schist) and are therefore susceptible to acidification by acid deposition. The pH history of the lakes has been calculated by using Index B from Renberg & Hellberg (1982), which has been adjusted to central European conditions and applied in this region for the first time. The results indicate that there have been no pH decreases in three of the lakes, while in one lake diatom composition and distribution change significantly towards the sediment surface. But taxonomical’ problems and difficulties in the pH classification of the rarely found diatoms complicate the interpretation of the results. Important taxa will be discussed in view of their ecological significance.

Diatom distribution and diatom inferred pH in the sediment of four alpine lakes

Protistan community grazing rates upon both bacterioplankton and autotrophic picoplankton were estimated using fluorescently-labeled prey and by measurement of extracellular hydrolysis of 4-methylumbelliferyl (MUF) β-N-acetylglucosaminide in a eutrophic reservoir and an oligo-mesotrophic lake during phytoplankton blooms. In addition, enzyme methods were optimized in bacterivorous flagellate cultures by two enzyme assays, based on fluorometric detection of protistan digestive activity, which were compared and calibrated independently against flagellate bacterivory. Enzymatic hydrolyses of MUF β-N,N′,N″-triacetylchitotriose and MUF β-N-acetylglucosaminide were measured in cell-free (sonicated) and whole-cell (unsonicated) samples. The hydrolysis of both substrates, using the whole-cell enzyme assay at in situ pH, was correlated significantly with total grazing rate of Bodo saltans. Thus the whole-cell enzyme assay with MUF β-N-acetylglucosaminide was used for freshwater samples. High-affinity (K

 m
 < 1 μmol 1−1) and low-affinity (K

 m
 > 100 μmol 1−1) enzymes were distinguished kinetically in most samples from both systems studied. Activities (V

 max
 ) of the high-affinity enzyme varied from 0.24 to 1.43 nmol 1−1 h−1. Protistan community grazing on bacterioplankton was in the range of 0.15–1.36 μg C 1−1 h−1. both for lake and reservoir, the differences being observed in grazing on picocyanobacteria (lake, 0.03-0.22 μg C 1−1 h−1. reservoir, 0.35–1.56 μg C 1−1) h−1. The enzyme activities were correlated significantly with the protistan grazing both on bacterioplakton (r

 s
 = 0.62, P < 0.001) and total procaryotic picoplankton (the sum of organic carbon grazed from bacteria and picocyanobacteria, r

 s
 = 0.73, P < 0.001) in the eutrophic reservoir. Weaker relationships (r

 s
 = 0.42) with a lower slope were found for the oligo-mesotrophic lake. Ingestion rate studies are time-consuming and the digestive enzyme assay with MUF β-N-acetylglucosaminide presents a rapid alternative for estimating total protistan prokaryotic picoplanktivory in freshwaters.

Evaluation of extracellular, high-affinity β- N -acetylglucosaminidase measurements from freshwater lakes: An enzyme assay to estimate protistan grazing on bacteria and picocyanobacteria

A 24 m deep mesotrophic lake was sampled at 25 cm depth intervals throughout the whole water column for flow cytometric analysis of bacterioplankton, with the object of (1) assessing the suitability of image analysis algorithms to objectively discriminate bacterial subgroups in natural samples; (2) testing 2 models to evaluate the effect of changes in signal intensity versus changes in the relative abundance of the individual subgroups on bulk cell properties of the bacterial commu- nity; and (3) to examine the suitability of a numerical index for quantifying small-scale spatial vari- ability in cell abundance. Within the heterotrophic bacterial community, 5 subgroups were detected by image analysis of DAPI fluorescence versus side scatter (SSC) histograms. On average for the whole profile, 91% (range: 86 to 94%) of all measured bacteria belonged to the 5 subgroups. Along the depth profile, abundances within these subgroups showed trends which were different from that for the bacterial community as a whole. The comparison of the 2 numerical models suggested that shifts in average DAPI and SSC signals of the whole community are better explained by changes in relative abundance within individual subgroups rather than by signal shifts within individual subgroups. Spatial variability in cell abundance for most of the heterotrophic bacterioplankton subgroups was highest in the upper 4 m of the water column, corresponding to the zone of turbulent mixing, and between 9 and 12 m, at the depth of maximum picocyanobacterial abundance. Our results show that flow cytometry in combination with image analysis of DAPI-SSC histograms at the level of bacterial subgroups allow objective assessment of the structure of the bacterial community and underpin potential sources of small-scale variability in bacterioplankton distribution.

https://www.int-res.com/articles/ame2004/36/a036p107.pdf

Tools for discrimination and analysis of lake bacterioplankton subgroups measured by flow cytometry in a high-resolution depth profile

Response of Alpine lakes to major environmental gradients, as detected through planktonic, benthic and sedimentary assemblages

Flagellates of different nutrition modes (hetero-, mixo-, osmo-, autotrophic) from batch cultures and natural freshwater samples were examined for abundance, cell size and biovolume changes after fixation and staining. The methods used were formaldehyde fixation and staining with 4,6-diamidino-2-phenylindole (DAPI) or fixation with Bouin's solution combined with a quantitative protargol stain (QPS). The values estimated with these protocols were compared to a live drop counting method and inspection of living organisms. Cell dimensions were measured with a semi-automatic image analysis system. We observed cultured species of Bodo saltans, Chilomonas paramaecium-group, Cryptomonas sp., Entosiphonomonas cf. sulcatum, Goniomonas cf. truncata and Paraphysomonas cf. vestita. Chemical treatment caused cell loss of up to 56%. In contrast lower abundance of field samples was determined via live counting than via formaldehyde and DAPI treatment. The number of living flagellates <5 μm in length was severely underestimated due to lower magnifications recommended for live drop counting. Formaldehyde and DAPI gave the best results conceming the abundance whereas Bouin's solution followed by a QPS could not be used to distinguish between autotrophic and heterotrophic flagellates. Examinations of the effects of preservation on cell size differed markedly for the flagellate taxa examined, with shrinkage down to 19 % and inflation up to 137 % of live cell volumes. These effects, observed even within a group of Dinobryon species, lead us to conclude that no single conversion factor for computing biovolume on preserved flagellates from natural samples is applicable.

Roland Psenner

Papers

Diatom distribution and diatom inferred pH in the sediment of four alpine lakes

Evaluation of extracellular, high-affinity β- N -acetylglucosaminidase measurements from freshwater lakes: An enzyme assay to estimate protistan grazing on bacteria and picocyanobacteria

Tools for discrimination and analysis of lake bacterioplankton subgroups measured by flow cytometry in a high-resolution depth profile

Response of Alpine lakes to major environmental gradients, as detected through planktonic, benthic and sedimentary assemblages

Comparison of three methods for determining flagellate abundance, cell size, and biovolume in cultures and natural freshwater samples