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:

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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.

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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 effect of different phosphorus loads (LP) on the phosphorus (P) and carbon (C) con- tent (biomass) of algae and bacteria was assessed in continuous culture. We tested if a mixed fresh- water microbial assemblage co-cultured with a phytoflagellate (Cryptomonas phaseolus) would com- ply with the 'phytoplankton-bacteria paradox' (sensu Bratbak & Thingstad 1985). This hypothesis states that the ratio of bacterial to algal abundance changes to the benefit of bacteria with decreasing LP. However, the phenomenon was originally investigated by simultaneously altering LP and micro- bial growth rates, and it is unclear to which extent it can be assigned to either parameter. Therefore, we set up 3 chemostat systems in triplicate at equal dilution rates, but with daily LP of 21, 41 or 62 µg l -1 d -1 (corresponding to 50, 100 and 150 µg P l -1 ). Higher LP led to a 5-fold increase in total algal abundance and biomass but to less than a doubling of these parameters in the bacterial assemblage. Total biomass ratios of bacteria to algae changed from 0.18 to 0.06 with increasing LP, while the bac- teria-algae total phosphorus ratios decreased from 0.80 to 0.17. The cellular C:P ratio of algae remained similar at all P concentrations, whereas the molar C:P ratios of bacterial cells significantly increased at higher LP (from 44 to 73). An enrichment experiment with the 50 µg P l -1 treatment demonstrated that bacteria at the lowest LP were co-limited by P and C, and that increased P stimu- lated mainly the algal fraction. The phytoplankton-bacteria paradox at the level of a mixed microbial assemblage is thus characterised by the following aspects: (1) bacteria profit from their high affinity to P and are better competitors at lower LP; (2) although algae compete with bacteria for P, P-limited algae release extracellular C that stimulates growth of their bacterial competitors; (3) when bacteria depend on algae as their sole source of organic C, this provides a feedback mechanism by which algae limit the abundance of their competitors at higher LP; (4) large oscillations in the bacteria-algae ratios at the lowest LP point to a greater instability of this interaction with stronger P competition. However, bacteria were not able to outcompete C. phaseolus, as algae were their only C source.

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Effects of phosphorus loading on interactions of algae and bacteria: reinvestigation of the 'phytoplankton-bacteria paradox' in a continuous cultivation system

Microbial communities are known to exist in extremely hot environments such as hydrothermal vents, but what about extremely cold regions? In their Research Commentary, Psenner and Sattler discuss results reported in the same issue by
 Priscu
 et al.
 in which a microbial assemblage was discovered in Antarctic lake ice. Although this environment is marked by permanent ice cover, pockets of liquid water can form during part of the year, allowing active growth and reproduction of organisms.

Life at the freezing point.

Distribution and diversity of autotrophic bacteria in groundwater systems based on the analysis of RubisCO genotypes.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1992.37.5.1092

Are rapid changes in bacterial biomass caused by shifts from top-down to bottom-up control ?

The in situ growth rates of dominant ciliate species were studied during and shortly after phytoplankton peaks in two water bodies: the eutrophic Ri'mov Reservoir (South Bohemia, Czech Republic) and the oligo-mesotrophic Piburger See (Tyrol, Austria). Growth rate estimates based on changes in ciliate abundances in incubated pre-screened samples (EN) were compared with those derived from the ciliate cell volume and ambient temperatures (£T). The values of EN were always rather lower than those of £T. During the studies, the food supply limited the ciliate growth depending on the ciliate feeding mode. An ecological grouping into filter feeding versus raptorial feeding ('hunt- ing') species, on the one hand, and attached/crawling (browsing) versus free swimming species, on the other hand, clearly affected experimental estimation. Both fine filter feeders (namely attached) and browsers exhibited a calculated £N closer to the theoretical (maximum) £T than did hunters and coarse filter feeders. It was apparent, for example, comparing £N and £T (day1) of the following species: filter feeders Halieria grandinella (£N = 0.42; £T >1.4), Strobilidium hexakinetum (0.34; >1.9), Pelagohalte- ria viridis (0.27; >0.9), Vorticella aquadulcis complex (0.75; >1.0); raptorial Balamon planctonicum (0.65; >1.5), Urotricha furcata (in Ri'mov Reservoir 0.65; >2.1; in Piburger See 0.20; >1.5), Rhab- doaskenasia minima (0.22; >1.0), Askenasia acrostomia (0.12; >0.6); opportunistic Cyrtolophosis mucicola (0.42; >1.6) and Cinetochilum margaritaceum (0.86; >1.4). Predation by rotifers apparently affected measurements in several samples containing —400 rotifers I"1; however, it seemed to be of little importance in the water column.

Roland Psenner

Papers

Effects of phosphorus loading on interactions of algae and bacteria: reinvestigation of the 'phytoplankton-bacteria paradox' in a continuous cultivation system

Life at the freezing point.

Distribution and diversity of autotrophic bacteria in groundwater systems based on the analysis of RubisCO genotypes.

Are rapid changes in bacterial biomass caused by shifts from top-down to bottom-up control ?

Growth rates of dominant planktonic ciliates in two freshwater bodies of different trophic degree