Brian A. Whitton

Biology of Cladophora in freshwaters

Abstract The aim of this review is to summarize the literature on Cladophora growing in freshwaters, especially those situations where nutrient enrichment by man has led to the presence of conspicuous and sometimes troublesome growths. Literature reviewed by Van Den Hoek (1963) and Fjerdingstad (1965) is largely omitted. Limited unpublished data is included.

Introduction to the Cyanobacteria

Features of cyanobacteria are introduced for non-specialists by highlighting topics in the various chapters. Aspects where much more is known now than a decade ago are pointed out, such as the importance of cyanobacterial nitrogen fixation in the oceans. This is followed by an account of the recent molecular studies most relevant for ecologists, especially topics not mentioned elsewhere in the book. Several ecological subjects of current interest are discussed, including research which seems important, but has sometimes been overlooked. Topics mentioned include sensing the environment and other organisms and signalling between cyanobacterial cells and between cyanobacteria and other organisms, and methods for studying N and P. The authors air their views on past and present matters concerning cyanobacterial taxonomy and nomenclature. Finally, comments are made on practical topics such as the use of cyanobacteria for inoculating soils, barley straw to control blooms and the likely contribution of cyanobacteria to developments in algal biotechnology during the coming decade.

Biological monitoring of eutrophication in rivers

There is an increasing awareness of the need to assess the impact of nutrient enrichment on river ecosystems separately from the impacts of organic effluents. A range of methods have been proposed and some have moved from the development stage to practical use by water management organizations. The methods can be applied to broad surveys or provide baseline information to assess possible future change. In the latter case it is recommended that several different methods are used, especially where it is important to get reliable information on the long-term impact of improvements in effluent quality. Estimates of biomass measured as chlorophyll a have often been used for phytoplankton and sometimes also for benthic communities. However, a lot of care is needed in applying this method, because of the range of factors besides nutrient concentration which can influence values. Approaches based on the whole community have been developed by a number of research groups, usually involving semiquantitative estimates of abundance. There has also been a rapid increase in the use of indices based on the relative proportions of epilithic diatom species. The methodologies used by a number of research groups in Europe are broadly similar, making it possible to compare results between different regions. The development of indices based on macrophyte floristic composition in relation to river nutrient status is also under development, especially in France and UK. However, interpretation of the results is complicated where long-term changes are taking place in nutrient concentrations in the water, because of the varying contributions of sediment and water to different species of rooted plant. Bioassays can be especially helpful where it is desired to establish whether either N or P is limiting for a population of community.

Diversity, Ecology, and Taxonomy of the Cyanobacteria

The cyanobacteria are photosynthetic prokaryotes possessing the ability to synthesize chlorophyll a and at least one phycobilin pigment; typically water acts as the electron donor during photosynthesis, leading to the release of oxygen. They are by far the largest group of photosynthetic prokaryotes, as judged by their widespread occurrence, frequent abundance, and morphological diversity. Not only are they represented at the present day in most types of illuminated environment, except for those at lower pH values, but they have one of the longest geological records (Schopf and Walter, 1982). Much of the earth’s original atmospheric oxygen was probably formed by organisms quite similar to modern cyanobacteria (Knoll, 1985) and they are still responsible for a considerable proportion of photosynthetic oxygen evolution in the oceans.

Spatial and seasonal variation in denitrification in the Swale–Ouse system, a river continuum

Rates of denitrification were studied in the sediments at five sites along the river continuum of the Swale–Ouse river system, NE England, together with one site on a highly eutrophic tributary (R. Wiske). Intact cores were taken on a monthly basis for 17 months and used to assess denitrification rates under simulated ambient conditions using acetylene blockage methodology. Within the headwater site (2.5 km upstream of start of main river) rates rarely exceeded 20 μmol N m−2 h−1. At the most downstream site (145.0 km down the main river and at the tidal limit) the maximum was 659 μmol N m−2 h−1. The highest rates on all sampling occasions were for the Wiske. Both spatial and seasonal trends were evident. A general trend for the rate to increase moving downstream can be explained largely by two factors: increase in ambient nitrate concentration and changes in sediment composition. Seasonally, a spring peak was evident at all sites, which can again be explained largely by two factors: temperature and nitrate concentration.

Resistance to zinc of Stigeoclonium tenue in the field and the laboratory

Field and laboratory studies have been carried out on the tolerance to zinc of Stigeoclonium tenue growing in flowing waters. Thirty-four different sites in England, France and Germany were included, the majority of them being chosen to represent examples of zinc pollution resulting from past or present mining activities. S. tenue was sometimes abundant in zinc polluted waters, and was found at sites with up to 20·0 mg l-1 of zinc capable of passing through a filter. At sites with field mean zinc levels of about 0·2 mg l-1 and above, populations show increased resistance to zinc in comparison with populations from sites with lower zinc levels, this increased resistance being largely, if not entirely, the result of genetic adaptation. Assays of populations from sites with high calcium levels suggest that these are less tolerant of a particular level of zinc than are populations from sites with low calcium levels. Levels of zinc bringing about a marked reduction in total growth during assay have a relativel...

Soils and Rice-Fields

Cyanobacteria are an important component of many soils. including the surface crusts that sometimes cover extensive areas in semiarid regions and mine spoil wastes. They are also abundant in many areas which are wet or submerged for part of the year. especially rice-fields. Most soils forms have sheaths or mucilage and this polysaccharide has important effects onthe soil. mostly beneficial. such as improved soil structure. but sometimes adverse where a dense surface layer impedes drainage. Nitrogen-fixing species often constitute half or more of the species present in soils not enriched with nitrogenous fertilizer and these can contribute combined nitrogen in several ways to adjacent vascular plants.

Aquatic mosses as monitors of heavy metal contamination in the river etherow, great britain

The use of aquatic mosses to monitor heavy metals was investigated in the River Etherow, near Manchester, Great Britain. The river was visited on five occasions during 1979 and 1980 and samples of water, sediment and submerged aquatic moss were analysed for heavy metals. Zinc in particular was an important pollutant in this river, sometimes exceeding 0·5mg litre−1 in the water. Significant positive correlations were found between concentrations of zinc in water and the terminal 2 cm shoot tips of Fontinalis squamosa and Rhynchostegium riparioides, suggesting that these species may be useful as monitors of zinc contamination in rivers. Data were also obtained for Amblystegium riparium and Fontinalis antipyretica, but these were not sufficiently widespread to enable their value as monitors to be assessed. Although chromium was not detected in the water (<0·01 mg litre−1), detectable concentrations were found in mosses from some sites, suggesting the occurence of intermittent sources of this metal.

Nutrient transport in the Humber rivers

Abstract The results of the weekly and storm sample measurement of the nutrient concentrations in ten Humber rivers over one annual cycle are presented. The nutrients include soluble reactive phosphorus (SRP), total dissolved phosphorus (TDP), total phosphorus (TP), nitrate and silicon (soluble reactive silicon). These data are combined with the river discharge data to calculate the nutrient loads discharged into the intertidal zones. The loads are expressed as the nutrient exports normalised with respect to the catchment areas. The results clearly demonstrate that the majority of the nutrient load is transported in autumn/winter storms. The rivers in the south of the region, i.e. Trent, Don, Aire and Calder, have high nutrient exports compared with the rivers in the north of the region such as the Wharfe, Swale, Nidd and Ure. These differences are attributable to the relative importance of effluent discharges and differences in the land use and extent of urbanisation in the regions. With the exception of the R. Derwent, those rivers with a high nitrate export also have the highest SRP export. The results for the R. Swale, the only river having two monitoring sites, highlight the importance of urban and agricultural impacts in the lowland region of the catchment. The export of silicon is least variable, although a sharp spring minimum in concentration, caused by phytoplankton uptake, is evident for the larger rivers such as the R. Trent. The fractionated forms of phosphorus also varied between the rivers but each of the fractions: SRP, (TDP-SRP), (i.e. mainly organophosphorus and inorganic polyphosphates hydrolysed in digestion procedure), and particulate phosphorus, significantly contributed to the load in all the rivers. For example the phosphorus load in the R. Trent is dominated by the SRP fraction, whereas the R. Swale export is highly influenced by the transport of suspended solids, most of which originates from the lowland region between Catterick and the confluence with the R. Ure. The results of intensive hourly sampling through a storm event on the R. Swale demonstrate the importance of the tributaries in the downstream 54 km section on the river. Although the majority (85%) of the water at the downstream site originates from the upland region north of Catterick, the majority of the nitrate (74%) and SRP (78%) originates from the rivers Wiske and Cod Beck as well as minor tributaries in the southern region of the catchment. A detailed mass balance of the section indicates net losses of nitrate, silicon, SRP and TDP from the water column.

Prokaryotic Metallothionein Gene Characterization and Expression: Chromosome Crawling by Ligation-Mediated PCR

A strategy is described for the characterization of a novel gene employing the polymerase chain reaction, inosine-containing oligonucleotide primers, and ligation mediated, or anchored polymerase chain reaction (APCR). The same primers, designed from the known protein sequence, are used to amplify the coding region of the gene and subsequently to ‘chromosome crawl’ by APCR. This strategy was applied to the characterization of a prokaryotic metallothionein gene, designated smtA, from the cyanobacterium Synechococcus PCC 6301 ( ═ Anacystis nidulans). The abundance of smtA transcripts was examined in extracts from cells exposed to heat shock and elevated concentrations of cadmium, zinc and copper ions. There was no detectable change in smtA transcript abundance following exposure to heat shock, while exposure to all three metal ions led to an increase in abundance. A smtA homologue was also identified in Synechococcus PCC 7942 ( ═ Anacystis nidulans R2).