bluuebunny/crossref_metadata_2025_split huggingface dataset:
State of environment indicators of ‘river health’: exploring the metaphor
Authors: Fairweather Peter G. 
Published: March 2003

Summary1. Indicators are crucial to many socio‐political schemes for portraying environmental influences of society. For example, the OECD model for State of the Environment Reporting uses three different sorts of indicators (pressure, condition, response) to differentiate the present condition of the environment from the anthropogenic pressures upon it and from any societal responses made to alleviate those pressures (thereby improving aspects of the overall condition).2. These sorts of indicators have a fundamental technical basis in the science supporting their exposition and usage. However, the criteria used in interpreting the indicator values are likely to be set by considerations that go beyond scientific grounds. That is, indicators are socially determined in the end. However, many scientists find it difficult to involve the public in such reporting.3. Scientists who are uncomfortable with this non‐technical use of their indicator constructs should recognize that it is merely another manifestation of the overall broadening of environmental concern termed ‘ecosystem health’. The emerging field of ecosystem health seeks to take our technical understanding of how the environment functions and combine it with socio‐economic goals, using a human health metaphor and an ethical underpinning.4. River health might be better served by adopting a veterinary approach rather than the model of human health. This is because, like animals, riverine environments come in many different forms and cannot complain of ill health. Desirable interventions will vary with the uses to which we wish to put a river and our reasons for being concerned about a river’s health. A framework for this diagnostic approach is presented.5. An enormous challenge lies ahead in integrating the various measurements of riverine attributes that might together constitute ‘river health’. We need ways to cater for the pluralism of modern societies, and we need more dynamic assessments of river condition, possibly founded on studies of key ecological processes.
New generation water quality guidelines for ecosystem protection
Authors: Hart Barry T. , Maher Bill , Lawrence Ian 
Published: March 2003

Summary1. Water quality guidelines are important for the management of water resources. Initially, guidelines focused on quality for domestic drinking water and for agricultural, recreational and industrial purposes. More recently, the emphasis has been on ecosystem protection, as well.2. This paper discusses the key elements of new risk‐based water quality guidelines being developed in Australia and New Zealand, that should lead to more effective management and protection of aquatic ecosystems.3. There are three essential elements to this new approach: (i) it is ecosystem‐based— ideally the guidelines should be, as far as possible, ecosystem‐specific; (ii) it is issue‐based— the guidelines should focus on the actual issues or problems caused by physical, chemical and biological stressors rather than on the individual indicators, as at present; and (iii) it is risk‐based. There is generally great difficulty in deciding whether adverse biological effects will result from various stressors added to an ecosystem. The new approach develops guideline ‘packages’ for each issue and, where possible, for each ecosystem type. Each ‘package’ consists of specified key performance indicators, trigger levels for these indicators (that is, levels which indicate the degree of risk that adverse biological effects may occur), and for high risk situations (where trigger levels are exceeded) a protocol for considering the effect of ecosystem‐specific factors in reducing (or enhancing) the biological effects.4. This paper presents a case study related to a highly relevant aquatic ecosystem issue in Australia, namely the excessive growth of cyanobacteria (blue‐green algal blooms), to illustrate how the new risk‐based guidelines might be applied.
The pathway to noxious cyanobacteria blooms in lakes: the food web as the final turn
Authors: Elser James J. 
Published: March 2003

1. Cyanobacteria blooms have long been the focus of limnological research as they often represent the ‘end member’ of limnological deterioration under various human impacts. Research over the past several decades has greatly illuminated the ecological factors promoting cyanobacteria blooms but controversy and confusion surround the successful integration of this diverse body of work.2. In this opinion article I attempt to integrate well‐known aspects of cyanobacteria bloom ecology (such as the roles of nutrient loading, N:P ratio, and mixing conditions) with more recent developments that highlight the importance of feedbacks within the food web in regulating cyanobacteria blooms. Food‐web feedbacks involving stoichiometric mechanisms appear to be particularly important, as accumulating data indicate that the food web influences cyanobacteria not just by regulating the rate of grazing mortality. Rather, trophic interactions may also regulate cyanobacteria dynamics by altering the consumer‐driven nutrient recycling regime in a way that shifts the competitive advantage away from cyanobacteria.3. Viewed in this way, cyanobacteria blooms can be seen as probabilistic events that are the end result of a series of key mechanisms involving nutrient loading, physical mixing conditions, and trophic interactions. To successfully manage lake water quality we should take advantage of each node of contingency leading to undesirable blooms. In doing so we will also have a more coherent scientific message to communicate with those directly involved with the socioeconomic politics of water quality decision making.
The ecological organisation of lake districts: general introduction
Authors: Kratz Timothy K. , Frost Thomas M. 
Published: March 2003

1. Here we introduce a special issue of Freshwater Biology that focuses on the landscape‐scale spatial and temporal patterns exhibited by multiple lakes within lake districts. We call this patterning, and the processes that lead to it, the ‘ecological organisation of lake districts.’2. Papers in this special issue share the common goal of examining landscape‐level processes that lead to spatial and temporal patterns of lake characteristics in individual or multiple lake districts. Several papers focus on the degree to which multiple lakes have synchronous among year variability in various physical, chemical, and biological variables. Others focus on the landscape‐level processes that lead to spatial patterning of lake characteristics. Finally, a few papers examine the relationship between spatial patterning and temporal dynamics. Papers in this special issue present results from 10 lake districts from North America, Europe, and Antarctica.
Inter‐specific differences in photosynthetic carbon uptake, photosynthate partitioning and extracellular organic carbon release by deep‐water characean algae
Authors: Sorrell Brian K. , Hawes Ian , Schwarz Anne‐Maree , Sutherland Donna 
Published: March 2003

1. The effect of light intensity on photosynthesis and the fate of newly fixed organic carbon was compared for three characean algae collected at the same depth (10 m) but differing in their depth distributions. For each species we determined photosynthesis–irradiance (P–E) responses, the partitioning of newly fixed carbon into four intracellular pools (low molecular‐weight compounds, polysaccharides, lipids and proteins) and the extracellular organic carbon (EOC) release at a range of photon flux densities (PFD) 0–60 μmol m–2 s–1.2. The P–E responses differed between the three species, with the light compensation point (Ec) and dark respiration rate highest in the shallowest species (Chara fibrosa), intermediate in the mid‐range species (C. globularis) and lowest in the deepest species (C. corallina). Photosynthetic efficiency (α) and photosynthesis: respiration ratios were lowest in C. fibrosa and highest in C. corallina.3. In all three species, the low molecular weight pool was the principal photosynthetic product (>60% of fixed C) at 3 μmol m–2 s–1 PFD, but its proportional contribution decreased rapidly with increasing irradiance. Polysaccharide rose to become the major product (>35% of fixed C) at saturating PFD (35 μmol m–2 s–1).4. Protein synthesis was saturated at 5 μmol m–2 s–1 in all species and was consistently a lower proportion of the fixed carbon in C. corallina than the other species. The fraction incorporated in the lipid pool increased slightly with irradiance but was always less than 10% of fixed C, while the proportion lost as EOC was unaffected by light, being significantly higher in C. fibrosa than the other species.5. A kinetic experiment with C. fibrosa at 35 μmol m–2 s–1 PFD revealed a continued increase in net polysaccharide, protein and lipid synthesis during a 22.5‐h light period, whereas the net size of the low molecular weight pool remained constant. In a subsequent dark period, protein and lipid synthesis continued at the expense of the polysaccharide and low‐molecular‐weight pools. The EOC release rose to a constant low release in the light, then peaked slightly immediately after the dark–light transition before returning to the same rate as in the light. Extrapolating these data over 24 h suggests that the proportion of fixed carbon lost as EOC may be as high as 10% in this species.6. The interspecific differences in carbon acquisition between the three species reflected their depth distributions, with the deeper species having more efficient photosynthetic metabolism, lower P:R ratios and less EOC release, although no apparent differences in internal partitioning of photosynthate.
Abrupt change in primary productivity in a littoral zone of Lake Biwa with the development of a filamentous green‐algal community
Authors: Nozaki Kentaro 
Published: March 2003

1. Some characteristics of the photosynthesis and primary production of benthic and planktonic algal communities were investigated in a littoral zone covered with gravel in the north basin of Lake Biwa, paying special attention to the recent development of filamentous green algae (FGA) in the benthic algal community.2. Pmax (maximum gross photosynthesis rate) values of the benthic algal community (0.1–1.2 mg C mg chl. a−1 h−1) obtained from photosynthesis–irradiance (P–I) curves were lower than those of the planktonic algal community (2.4–11.5 mg C mg chl. a−1 h−1). This is apparently a result of the high degree of self shading in the benthic algal community and its low turnover as compared with that of the planktonic algal community.3. Relatively high Ik values (150–200 μmol photon m−2 s−1) were observed in the benthic algal community only in June–July when a FGA, Spirogyra sp., was abundant. This reflected a photosynthetic characteristic of the Spirogyra itself, in which photosynthesis was saturated at high light intensity.4. The FGA community established in the layer between planktonic and sessile (benthic algae except for FGA) algal communities. It brought about extraordinarily high organic matter production in the littoral zone at the expense of production in the sessile algal community.
Evaluation of methods for estimating macroinvertebrate species richness using individual stones in tropical streams
Authors: Melo Adriano S. , Froehlich Claudio G. 
Published: March 2003

1. The most straightforward way to assess diversity in a site is the species count. However, a relatively large sample is needed for a reliable result because of the presence of many rare species in rich assemblages. The use of richness estimation methods is suggested by many authors as a solution for this problem in many cases.2. We examined the performance of 13 methods for estimating richness of stream macroinvertebrates inhabiting riffles both at local (stream) and regional (catchment) scales. The evaluation was based on (1) the smallest sub‐sample size needed to estimate total richness in the sample, (2) constancy of this size, (3) lack of erratic behaviour in curve shape and (4) similarity in curve shape through different data sets. Samples were from three single stream sites (local) and three from several streams within the same catchment basin (regional). All collections were made from protected forest areas in south‐east Brazil.3. All estimation methods were dependent on sub‐sample size, producing higher estimates when using larger sub‐sample sizes. The Stout and Vandermeer method estimated total richness in the samples with the smallest sub‐sample size, but showed some erratic behaviour at small sub‐sample sizes, and the estimated curves were not similar among the six samples. The Bootstrap method was the best estimator in relation to constancy of sub‐sample sizes, but needed an unacceptably large sub‐sample to estimate total richness in the samples. The second order Jackknife method was the second best estimator both for minimum sub‐sample size and constancy of this size and we suggest its use in future studies of diversity in tropical streams. Despite the inferior performance of several other methods, some produced acceptable results. Comments are made on the utility of using these estimators for predicting species richness in an area and for comparative purposes in diversity studies.
Life on the edge: the plankton and chemistry of Beaver Lake, an ultra‐oligotrophic epishelf lake, Antarctica
Authors: Laybourn‐Parry Johanna , Quayle Wendy C. , Henshaw Tracey , Ruddell Andrew , Marchant Harvey J. 
Published: March 2003

1. Beaver Lake, a large epishelf lake in eastern Antarctica was sampled on two occasions during the austral summer of 2000. Two sites, one 1 km offshore and another 6 km offshore were sampled at intervals to depths of 40 and 110 m, respectively.2. The lake is an end member of ultra‐oligotrophic lake systems with a very low carbon pool. Dissolved organic carbon concentrations ranged between 95 and 652 μg L–1. Nutrient levels were generally low with soluble reactive phosphorus ranging from undetectable to 8.4 μg L–1, ammonium ranged between 1.8 and 5.0 μg L–1, nitrate from undetectable to 161 μg L–1 and nitrite 1.1–5.3 μg L–1.3. Chlorophyll a concentrations (0.39–4.38 μg L–1) showed an unusual distribution with the highest levels close to the lake bottom at the offshore site (110 m) where the phototrophic nanoflagellates (PNAN) displayed strong autofluorescence.4. Bacterial concentrations were low, with a maximum of 7.60 × 107 L–1, as were the concentrations of heterotrophic nanoflagellates that exploit them.5. Primary production ranged between 19.7 and 25.49 μg C L–1 day–1 and bacterial production from 0.32 to 1.15 μg C L–1 day–1.6. In common with other continental Antarctic lakes, the system was dominated by a microbial plankton. However, a dwarf variety of the calanoid copepod, Boeckella poppei, occurred below 25 m at concentrations of 3–5 L–1.7. The data suggest that primary production and bacterial production were not limited by nutrient availability, but by other factors, e.g. in the case of bacterial production by organic carbon concentrations and primary production by low temperatures.
The effects of vertical mixing on a phytoplankton community: a modelling approach to the intermediate disturbance hypothesis
Authors: Elliott J. A. , Irish A. E. , Reynolds C. S. 
Published: March 2003

1. Connell’s (1978) intermediate disturbance hypothesis (IDH) has been proposed as one explanation of why diversity is often highest at intermediate levels of disturbance. We used a model phytoplankton responses to environmental change (PROTECH) to investigate the validity of this hypothesis.2. In a simulated phytoplankton assemblage of eight species, we found that the relationship between the increased intensity of a single forcing event and diversity was described by a positively skewed curve.3. A progressive increase in forcing frequency introduced a sharp decrease in diversity at a threshold frequency. However, the highest diversity values were found at an intermediate frequency of disturbance.4. We described the shape of this breakpoint response as like a ‘cliff’ and reconcile it with multiple stable‐point theory. It is argued that the IDH should possibly be represented by this ‘cliff’ relationship, which may be applied to (or encourage the re‐examination of) many previous studies.
Geographical patterns of species turnover in aquatic plant communities
Authors: Virola Teija , Kaitala Veijo , Lammi Antti , Siikamäki Pirkko , Suhonen Jukka 
Published: March 2003

1. A classic theory in biogeography predicts that high latitude communities are unstable. This may be because of decreased species richness or decreased environmental predictability and productivity towards the poles.2. We studied latitudinal patterns in long‐term community persistence of aquatic vascular plants in 112 Finnish lakes, situated within a 1000‐km range from the northernmost to the southernmost lake.3. Contrary to theoretical predictions, we found that the turnover rate of plant species in 45 years was inversely related to latitude. That is, plant communities in northern lakes were more persistent than communities in southern lakes. When we used multiple regression to find the best predictors of species turnover rate (TR), latitude was the only variable that was highly significantly related to species turnover rate. Area, species number, water transparency, pH and change in transparency did not notably explain the gradient observed.4. The latitudinal trend was mainly because of lower species immigration rates at higher latitudes, whereas extinction rate did not so strongly decrease with increasing latitude. Immigrations and extinctions in the lakes were not in balance: the species numbers between the 1930s and 1980s increased more strongly in the southern than northern lakes.5. We suggest that the inverse relationship between latitude and plant species TR in Finland is most probably caused by human influence on lakes, especially eutrophication and immigration of new species in southern latitudes. In addition, although species richness per lake did not decrease towards the north, the total species pool probably does, which means that in the north there are fewer species that can actually immigrate.
A hydrogeomorphological context for ecological research on alpine glacial rivers
Authors: Smith Barnaby P. G. , Hannah David M. , Gurnell Angela M. , Petts Geoffrey E. 
Published: March 2003

1. This paper presents a framework for the analysis of glacial stream ecosystems based upon the hierarchy of physical processes that operate over timescales varying from diel to millennial. Linked conceptual models propose interrelationships between climate, hydrology and fluvial geomorphology in alpine catchments.2. These conceptual models are illustrated using data from the Taillon/Gabiétous catchment, French Pyrénées. Secondary sources provide information concerning the long‐term sequence of climatic and geomorphological controls on contemporary catchment processes. Detailed hydrogeomorphological field data collected over three consecutive summer melt seasons (1995–97) permit identification of marked changes in shorter‐term (diel, seasonal and inter‐annual) physical processes.3. Clear differences in the response of water quality and quantity variables were observed between years as climatic conditions varied. In two of the three study years, a precipitation‐driven regime was imposed upon the typical ablation‐driven river discharge pattern in alpine streams. Clear changes in water quality and quantity were evident with increasing distance from the glacier: (i) discharge increased although specific discharge decreased markedly, (ii) the mean and variability in water temperature increased, and (iii) base concentrations of suspended solids decreased.4. The physical processes incorporated in the conceptual models presented in this paper have ecological implications because they underpin a nested suite of disturbance regimes operating over timescales from diel to millennial.
Effects of light and nutrients on the net accumulation and elemental composition of epilithon in boreal lakes
Authors: Frost Paul C. , Elser James J. 
Published: March 2003

1. Two experiments in the Experimental Lakes Area (ELA) in north‐western Ontario, Canada examined the effects of light and two key elements on the net accumulation and elemental composition of epilithon. In Lake (L) 224, benthic algae were grown under different light intensity and phosphorus supply, while in L302S we provided three levels of two different carbon sources (bicarbonate and glucose) to algae colonizing nutrient‐diffusing substrata. After 1 month of accumulation, we sampled biofilms for chlorophyll (chl), carbon (C), phosphorus (P) and algal C.2. Increased C supply did not significantly affect algal growth (C or chl) or elemental composition (C/P ratios) in L302S. However, P enrichment increased chl and algal C, dramatically reduced the C/P ratio of epilithon, and did not affect total organic C in L224. Phosphorus enrichment also increased the proportion of algal material in the total particulate organic matter and altered the taxonomic composition of algae in L224 biofilms. Shading had no significant effect on the C/P ratio and total organic C in epilithon from the L224 experiment.3. Our results demonstrate that P supply affects the elemental composition of organic matter that collects on rock substrata. It thus appears that low availability of P relative to C and light drives the formation and retention of high C/P organic matter on rock surfaces in oligotrophic boreal lakes.
Changes in genetic structure of North American Bythotrephes populations following invasion from Lake Ladoga, Russia
Authors: Berg David J. , Garton David W. , Macisaac Hugh J. , Panov Vadim E. , Telesh Irena V. 
Published: March 2003

1. We used allozyme electrophoresis to compare Bythotrephes longimanus (Crustacea: Onychopoda: Cercopagididae) from recently founded North American populations with those from native European populations, and to examine changes in genetic structure of North American populations over time.2. The genetic structure of North American populations in 1996 was similar to that of European populations, because of the disappearance of founder effects which distinguished North American from European populations in 1989.3. The Lake Ladoga, Russia population was more closely related to North American populations than to other European populations, consistent with non‐genetic evidence implicating Lake Ladoga as the source of North American populations.4. Our results provide additional evidence of the presence of an invasion corridor that allows Urasian and Ponto‐Caspian species to be introduced into North American freshwater ecosystems, and show that founder effects can erode over time following establishment of invasive species.