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The River Continuum Concept implies that consumers in headwater streams have greater dietary access to terrestrial basal resources, but recent studies have highlighted the dietary importance of high-quality algae. Algae provide consumers with physiologically important omega-3 (n-3) polyunsaturated fatty acids (PUFA), particularly eicosapentaenoic acid (EPA). However, terrestrial plants and most benthic stream algae lack the long-chain (LC) n-3 PUFA docosahexaenoic acid (DHA, 22:6n-3), which is essential for neural development in fish and other vertebrates. We sampled subalpine streams to investigate how the PUFA composition of neural (brain and eyes), muscle, and liver tissues of freshwater fish is related to their potential diets (macroinvertebrates, epilithon, fresh and conditioned terrestrial leaves). The PUFA composition of consumers was more similar to epilithon than to terrestrial leaves. Storage lipids of eyes most closely resembled dietary PUFA (aquatic invertebrates and algae). However, DHA and arachidonic acid (ARA, 20:4n-6) were not directly available in the diet but abundant in organs. This implies that algal PUFA were selectively retained or were produced internally via enzymatic PUFA conversion by aquatic consumers. This field study demonstrates the nutritional importance of algal PUFA for neural organs in aquatic consumers of headwater regions. Electronic supplementary material The online version of this article (10.1007/s10750-020-04445-1) contains supplementary material, which is available to authorized users.

The amphipod Dikerogammarus haemobaphes is a high-risk carrier of parasites that impact wildlife in its non-native range. Studies using the mitochondrial genes, Cytochrome Oxidase Sub-Unit 1 (cox1) and small-subunit ribosomal RNA gene (16S), provide some nucleotide detail for understanding the evolution and phylogeography of this species. Despite this, the origins of the invasion remain unknown, as do the origins of its parasites. This study provides the full annotated mitochondrial genome (15,460 bp) of D. haemobaphes, consisting of 2 rRNAs, 24 tRNAs and 14 protein coding genes. Mitochondrial genes from the UK isolate are compared to existing data on NCBI and are used in a concatenated phylogenetic approach and identify D. haemobaphes as an early member of the Gammaridae (Amphipoda). Viral, bacterial, protistan and microsporidian parasites are present across the Gammaridae, including D. haemobaphes, suggesting the ancestor of the Gammaridae harboured related diseases, and that further screening of amphipods is likely to reveal further microparasite diversity. This correlation suggests that other gammarid invaders have the potential to harbour a range of microparasites. The mitochondrial genome of this species will act a resource to facilitate our understanding of geneflow, disease epidemiology and evolutionary history in this invasion-disease model.

Conceptual models are derived to indicate the signs and symptoms inherent in nutrient changes to brackish, estuarine and coastal areas of restricted circulation. These give a structured approach to detecting adverse symptoms of hypernutrification and eutrophication at all levels of biological organisation, from effects at cellular levels to the ecosystem approach. The conceptual models illustrate the bottom-up approaches to the detection and control of potential problems and the importance of top-down responses. The bottom-up approaches incorporate mechanisms with regard to inputs, retention of nutrients, biogeochemical cycling and the primary production response. The top-down approaches include the detection of responses in high-profile components of the marine system, such as fisheries, sea mammals and wading birds and seabirds, which are often of paramount socio-economic or conservation importance. The management of the above causes and consequences, and following from the adoption by signatories to proposals given by the Paris Commission (PARCOM), can be accomplished by the derivation of Ecological Quality Objectives (EcoQO) and Ecological Quality Standards (EcoQS). These are given here as a development from the Environmental Quality Objectives and Standards (EQO/EQS) approach. Such EcoQO and EcoQS are regarded as as an aid to monitoring and management of estuaries and coastal waters. That management includes recent proposals within European legislation aimed at monitoring and managing the health and integrity of coasts and estuaries, for example the implementation of the Nitrates, Species & Habitats, and Water Framework Directives. The paper, therefore, discusses both the quality and quantity of data involved in the science required by managers and the way ahead for assessing and managing the fate and effects of nutrients. Using European and U. S. examples, the paper introduces the major challenge of how the concerns highlighted can be addressed by policy action.

The present paper explores (i) the way silicate concentrations may control the switch from diatom to non-diatom dominated phytoplankton, (ii) the consequence of mixing intensity and nutrient loading on phytoplankton composition (and potentially harmful species), (iii) to what extent trophic interactions may interfere with this abiotic control. The data used for this paper were selected from experiments run in 3-m3 land-based mesocosms (SW Netherlands) since 1993. Various nutrient and/or mixing regimes were applied to seawater incubated for periods varying from 1 to five months. The termination of the initial diatom bloom was induced by silicate concentrations below 2 µM, whereas the subsequent flagellate bloom was limited by N or P availability. Combined high nitrogen loadings and stratification events promoted the development of potentially harmful dinoflagellates but other factors such as grazing and temperature played a decisive role in the appearance of such blooms. Despite their relatively low intrinsic growth rate, copepods were able to control diatoms and microzooplankton development. Microzooplankton efficiently incorporated blooms of small phytoplankton species. These results, combined with previous experiments where nitrogen enrichment induced increases in small phytoplankton biomasses, stress the positive effect of N-enrichment on the microbial food web. Conversely, blooms of large diatom species exemplified the trophic mismatch leading to the accumulation of algal biomass without transfer to higher trophic levels. [KEYWORDS: diatoms, Phaeocystis, Cerataulina marina, stratification, ciliates, copepods]

There is growing interest in large-scale approaches to ecology, for both plants and animals. In particular, macroecological studies enable examination of the patterns and determinants of species richness of a variety of groups of organism throughout the world, which might have important implications for prediction and mitigation of the consequences of global change. Here, we provide richness data for freshwater fishes, which, with more than 13,000 described species, comprise a quarter of all vertebrate species. We conducted an extensive literature survey of native, non-native (exotic), and endemic freshwater fish species richness. The resulting database, called Fish-SPRICH, contains data from more than 400 bibliographic sources including published papers, books, and grey literature sources. Fish-SPRICH contains richness values at the river basin grain for 1,054 river basins covering more than 80% of the earths continental surface. This database is currently the most comprehensive global database of native, non-native and endemic freshwater fish richness available at the river basin grain.

Monitoring of three-dimensional floodplain vegetation structure is essential for ecological studies, as well as for hydrodynamic modelling of rivers. Height and density of submerged vegetation and density of emergent vegetation are the key characteristics from which roughness parameters in hydraulic models are derived. Airborne laser scanning is a technique with broad applications in vegetation structure mapping, which therefore may be a promising tool in monitoring floodplain vegetation for river management applications. This paper first provides an introduction to the laser scanning technique, and reviews previous studies on the extraction of vegetation height and density of forests, low vegetation and meadows or unvegetated areas. Reliable predictions using laser scan data have been reported for forest height (R2=0.64–0.98), parameters related to forest density, such as stem number, stem diameter, biomass, timber volume or basal area (R2=0.42–0.93), and herbaceous vegetation height (summer condition; R2=0.75–0.89). No empirical relations have been reported on density of herbaceous vegetation. Laser data of meadows and unvegetated areas show too much noise to predict vegetation structure correctly. In a case study for the lower Rhine river, the potential of laser scan mapping of vegetation structure was further explored for winter conditions. Three laser-derived metrics that are often reported in the literature have been applied to characterize local vertical distributions of laser reflections. The laser data clearly show the large structural differences both between and within vegetation units that currently are the basis of floodplain vegetation and roughness mapping. The results indicate that airborne laser scanning is a promising technique for extraction of 3Dstructure of floodplain vegetation in winter, except for meadows and unvegetated areas.

We present an overview of a large collaborative field campaign, in which we collected a long-term (months) high-resolution (4Hz measurement frequency) hydrodynamic data set for several locations at the mudflat–salt marsh ecosystem and linked this to data on sediment transport and to a biological description of the organisms on the mudflat and the marsh. In this paper, part of this database has been used to identify general relationships that can be used for making hydrodynamic characterisations of mudflat–salt marsh ecosystems. We observed a clear linear relation between tidal amplitude and the maximum current velocity, both at the mudflat as well as within the marsh vegetation. Velocities in the vegetation were however a magnitude lower than those on the mudflat. This relationship offers promising possibilities for making hydrodynamic habitat characterisations and for validating hydrodynamic models. [KEYWORDS: creek ; current velocity ; marsh vegetation ; mudflat ; velocity profiles ; waves]

Understanding of migration patterns is essential in the interpretation of hydro-acoustic stock assessment data of partly demersal partly pelagic fish stocks. In this paper we provide this kind of information for some species that were common in the Mwanza Gulf of Lake Victoria in the 1980s, before and after the upsurge of introduced Nile perch (Lates niloticus). Detritivorous haplochromines and Nile tilapia (Oreochromis niloticus), both stay near the bottom during day and night. Feeding seems to occur predominantly during the day. The zooplanktivorous haplochromines and dagaa (Rastrineobola argentea) dwell near the bottom by day and migrate towards the surface during the night. They seem to follow their prey, zooplankton and lake-fly larvae. Piscivorous nembe (Schilbe intermedius) show similar migration patterns to zooplanktivorous fishes, but their behaviour cannot be unambiguously explained by pursuit of prey. Nile perch to some extend migrate into the column at night, though the majority remains near the bottom. Feeding takes place during day and night.

In a classical paper, Hutchinson (1961) argued that the large number of species in most plankton communities is remarkable in view of the competitive exclusion principle, which suggests that in homogeneous, well-mixed environments species that compete for the same resources cannot coexist. Few ideas in aquatic ecology have evoked more research than this `paradox of the plankton'. This review is an effort to put the main solutions to the paradox that have been proposed over the years into perspective. Hutchinson himself already suggested that the explanation could be that plankton communities are not in equilibrium at all due to weather-driven fluctuations. Subsequent research confirmed that such externally imposed variability can allow many species to coexist. Another important point is that in practice the homogeneous well-mixed conditions assumed in the competitive exclusion principle hardly exist. Even the open ocean, for instance, has a spatial complexity resulting from meso-scale vortices and fronts that can facilitate coexistence of species. Perhaps most excitingly, theoretical work on species interactions has given a counter-intuitive new dimension to the understanding of diversity. Various competition and predation models suggest that even in homogeneous and constant environments plankton will never settle to equilibrium. Instead, interactions between multiple species may give rise to oscillations and chaos, with a continuous wax and wane of species within the community. Long-term laboratory experiments support this view. This chaotic behavior implies among other things that plankton dynamics are intrinsically unpredictable in the long run when viewed in detail. Nonetheless, on a higher aggregation level, indicators such as total algal biomass may show quite regular patterns.

In a classical paper, Hutchinson (1961) argued that the large number of species in most plankton communities is remarkable in view of the competitive exclusion principle, which suggests that in homogeneous, well-mixed environments species that compete for the same resources cannot coexist. Few ideas in aquatic ecology have evoked more research than this 'paradox of the plankton'. This review is an effort to put the main solutions to the paradox that have been proposed over the years into perspective. Hutchinson himself already suggested that the explanation could be that plankton communities are not in equilibrium at all due to weather-driven fluctuations. Subsequent research confirmed that such externally imposed variability can allow many species to coexist. Another important point is that in practice the homogeneous well-mixed conditions assumed in the competitive exclusion principle hardly exist. Even the open ocean, for instance, has a spatial complexity resulting from meso-scale vortices and fronts that can facilitate coexistence of species. Perhaps most excitingly, theoretical work on species interactions has given a counter-intuitive new dimension to the understanding of diversity. Various competition and predation models suggest that even in homogeneous and constant environments plankton will never settle to equilibrium. Instead, interactions between multiple species may give rise to oscillations and chaos, with a continuous wax and wane of species within the community. Long-term laboratory experiments support this view. This chaotic behavior implies among other things that plankton dynamics are intrinsically unpredictable in the long run when viewed in detail. Nonetheless, on a higher aggregation level, indicators such as total algal biomass may show quite regular patterns.

We gathered taxonomic information regarding the occurrence of rotifers in Antarctica and Subantarctica, producing a database of more than 1100 records from all 93 papers published on the region since the start of research expeditions in the far South. From this literature review, we outline a history of rotifer research in Antarctica. Then, using the database, we address specific questions on biogeographic patterns in species richness in rotifers in Antarctica and Subantarctica. We highlight a complex scenario of differences between areas and latitudinal gradients, differentially affected by problems in sampling bias. The number of species of monogonont rotifers seems to decrease with increasing absolute latitudes, whereas the number of species of bdelloid rotifers generally increases with increasing absolute latitudes.

The Netherlands are a small, low-lying delta in W. Europe (42 000 km 2;50degrees-54degrees N; 3degrees-8degrees E), mainly consisting of alluvial deposits from the North Sea and from the large rivers Rhine and Meuse. The country was 'created by man'. The conversion of natural aquatic and terrestrial ecosystems into drained agricultural land was a major cultural operation over the past 1000 years. Roughly 55% of the country's surface area is still agricultural land. Some decades ago, The Netherlands' landscape was characterised by an armoured coastline and bridled estuaries, a drastically reduced area of saline and freshwater marshes, fully regulated rivers and streams, and numerous artificial lakes. The aquatic ecosystems beyond the influence of the large rivers, the Pleistocene raised bogs and moor lands, have almost been completely annihilated in the past. Acidification and eutrophication led to the deterioration of the remaining softwater lake vegetation. Last but not least, an artificial drainage system was constructed, leading to an unnatural water table all over the country, high in summer, low in winter. Only very recently, some 25 years ago, the tide has been turned and ecological rehabilitation and restoration of disturbed ecosystems are in full swing now, enhanced by the European Union policy to set aside agricultural land in the Netherlands in favour of the development of 'nature'. The state of the art of aquatic and semi-aquatic ecological restoration projects in the Netherlands is given. Starting from the conceptual basis of restoration ecology, the successes and failures of hundreds of restoration projects are given. Numerous successful projects are mentioned. In general, ecological restoration endeavours are greatly benefiting from progressive experience in the course of the years. Failures mainly occur by insufficient application of physical, chemical or ecological principles. The spontaneous colonisation by plants and animals, following habitat reconstruction, is preferred. But sometimes the re-introduction of keystone species (e.g. eelgrass; salmon; beaver) is necessary in case the potential habitats are isolated or fragmented, or when a seed bank is lacking, thus not allowing viable populations to develop. Re-introduction of traditional management techniques (e. g. mowing without fertilisation; low intensity grazing) is important to rehabilitate the semi-natural and cultural landscapes, so characteristic for the Netherlands. For aquatic ecosystems proper (estuaries, rivers, streams, larger lakes) the rule of thumb is that re-establishment of the abiotic habitat conditions is a pre-requisite for the return of the target species. This implies rehabilitation of former hydrological end geomorphological conditions, and an increase in spatial heterogeneity. The 'bottom-up' technique of lake restoration, viz. reduction in nutrient loadings, and removal of nutrient-rich organic sediment, is the preferred strategy. The 'top-down' approach of curing eutrophicated ecosystems, that is drastic reduction of fish stock, mainly bream, and introduction of carnivorous fish, may be considered as complementary. For semi-aquatic ecosystems (river-fed and rain-fed peat moors, brook valleys, coastal dune slacks) it also counts that the abiotic constraints should be lifted, but here the species-oriented conservation strategy, the enhancement of the recovery of characteristic plant and animal species, is mainly followed. An important pre-requisite for the rehabilitation of the original natural or semi-natural vegetation is the presence of viable seed bank.Restoration of salt-marsh vegetation has to deal with a short-lived persistent seed bank, which means that transport of seeds by water currents is important. Isolated softwater ecosystems may rely on the long-lived seeds of the aquatic macrophytes. The paper ends with some notes on the predictability of the outcome of ecological restoration measures and the societal position of restoration ecology as a science. Scientists hold different views on the predictability of restoration measures. A fact is that the predictability of ecosystem development increases, with increasing knowledge of the underlying environmental processes.

The paper reviews the past, present and future of eight anadromous fish species inhabiting the Lower Rhine (The Netherlands), viz. -sturgeon (Acipenser sturio), whitefish and houting (Coregonus lavaretus, C. oxyrinchus), smelt (Osmerus eperlanus), allis and twaite shad (Alosa alosa, A. fallax), sea trout (Salmo trutta) and salmon (Salmo salar). All species are under threat or became extinct (e.g. sturgeon, allis shad). It is not possible to single out a specific factor for the decline or disappearance. A combination of factors is responsible, as the degradation of the spawning and nursery areas, river correction for shipping, building of sluices and hydropower dams, extraction of sand and gravel and river pollution. The likelihood that a species will return via natural recovery, or restocking is assessed. The return of the sturgeon is unlikely. Present observations of sturgeon can be attributed to releases of unwanted sturgeon hybrids. A natural stock of coregonids in Dutch waters seems not feasible any more due to irreversible habitat degradation. Present day catches originate from German releases. The anadromous smelt, heavily reduced in numbers, still inhabits some of our waters, the non-migratory smelt is still very common. The allis shad is extinct and unlikely to recover. The species never spawned in the Dutch part of the Rhine. Twaite shad, declining in numbers, are still observed in the lower reaches of Rhine and Meuse. Sea trout is presumably still present in the same varying numbers as before. Spawning in our waters has not been documented. The salmon, once fished in large numbers, is now the subject of restocking programmes in Germany. Observations of individuals can partly be attributed to these programmes but also to straying salmon. Restocking programmes should be considerably improved before noticeable success is to be met.

A collaborative international project funded by the European Union's INCO-DC programme is undertaking limnological, fish biological, environmental and socio-economic research in five tropical lakes and reservoirs in Sri Lanka, Thailand and the Philippines over the period 1998-2001. The aim is to determine their trophic structure and their capacity to sustain both their existing Fisheries and present and future aquaculture. In some cases, these activities could potentially be expanded for the benefit of rural communities and of the local market within the bounds of social and environmental sustainability. This paper describes the concepts and methods involved in this innovative multidisciplinary project which aims to integrate limnological, fisheries and socio-economic issues in a comparative approach involving Asian and European research teams. [KEYWORDS: Asia; reservoirs; lakes; food web interaction; fish biology; aquaculture; fisheries; ecosystems; socio-economic development Resources management; sri-lanka; perspective; growth]

In many European rivers, including the major streams of the Rhine and Elbe basins, the nutrient load (N and P) still exceeds target levels. In this paper, a model is presented that describes the river nutrient load as a function of nutrient sources, runoff and lithology in the upstream basin. The model was tested with independent data on nutrient sources (input) and nutrient river load (output) for 130 specific combinations of sub-basins and 5 year periods. A wide range of river systems within the Rhine and Elbe basins were included and the analysis covers a period of 25 years from 1970 to 1995. Most of the observed spatial and temporal variation in the average annual river nutrient load was successfully described by the model. It is therefore concluded that the model can be used to predict the effect of changes in nutrient sources (e.g. reduction of livestock numbers, further improvement of waste water treatment plants etc.) on the average annual nutrient loads of the rivers Rhine, Elbe and their main tributaries.

The construction of a storm-surge barrier in the mouth of the Oosterscheide caused important hydrodynamical and morphological changes that could influence the macrobenthic populations. This paper is one in a series of five all dealing with the effects of the storm-surge barrier on macrozoobenthos and analyses the spatial and temporal distribution of macrozoobenthos in the Oosterschelde and its relationship with some environmental parameters, based on two large scale sampling campaigns, one before and one after the completion of the barrier. The sediment of the sampling stations was fine, well sorted sand, with an average mud content of about 2.5%. Only in the Krabbenkreek the sediment was coarser in 1989. The tidal elevation of the sampling sites decreased significantly in 1989. The density of macrozoobenthos was significantly lower, the biomass higher in 1989. The density was dominated by deposit feeders, the biomass by filter feeders. The difference in biomass between both years was mainly due to a substantial increase of the biomass of filter feeders in 1989. The number of species per station was significantly smaller in 1989 than in 1985. Between 1985 and 1989, frequency of occurrence decreased in 34 versus 13 which increased, density increased in 13 species and decreased in 34 species, biomass increased in 18 species and decreased in 29 species. Based on TWINSPAN several clusters of stations, each with a different faunal composition, were identified. These clusters did not form distinct zones on the tidal flats but were dispersed widely. The relationship between density and biomass of different trophic groups and the mud content of the sediment and the depth was analysed. This relationship sometimes differed clearly between years. The correlation coefficient of a multiple regression between density and biomass of individual species and environmental factors, although significant in most cases, was very low, indicating that only a small proportion of the species variability was explained. The relationship between benthos and environmental factors was further analysed by canonical correlation analysis and multivariate discriminant analysis that gave different results for the 1985 and 1989 data. This is probably due to the broad tolerance of the species to the range of the environmental variables found in our study area. From a TWINSPAN of the density data of 1985 and 1989 together we could conclude that, although the environmental parameters in a group of stations, showing a large faunal similarity in one year, did not change, the faunal composition did. This indicates that faunal changes are not necessarily linked to changes in the measured environmental parameters. In the discussion the different factors affecting macrobenthic populations are situated and it is suggested that the macrobenthic populations are probably more towards the nonequilibrium end of the continuum between nonequilibrium and equilibrium communities as defined by Wiens (1984). Although the impact of the construction of the barrier on the macrobenthic community seems at present to be rather small this does not mean that on the long-term there will be no effect.

Weighted averaging regression and calibration form a simple, yet powerful method for reconstructing environmental variables from species assemblages. Based on the concepts of niche-space partitioning and ecological optima of species (indicator values), it performs well with noisy, species-rich data that cover a long ecological gradient (>3 SD units). Partial least squares regression is a linear method for multivariate calibration that is popular in chemometrics as a robust alternative to principal component regression. It successively selects linear components so as to maximize predictive power. In this paper the ideas of the two methods are combined. It is shown that the weighted averaging method is a form of partial least squares regression applied to transformed data that uses the first PLS-component only. The new combined method, ast squares, consists of using further components, namely as many as are useful in terms of predictive power. The further components utilize the residual structure in the species data to improve the species parameters (‘optima’) in the final weighted averaging predictor. Simulations show that the new method can give 70% reduction in prediction error in data sets with low noise, but only a small reduction in noisy data sets. In three real data sets of diatom assemblages collected for the reconstruction of acidity and salinity, the reduction in prediction error was zero, 19% and 32%.

International audience; Although several studies have examined the functional diversity of freshwater macroinvertebrates, the variety of methodologies combined with the absence of a synthetic review make our understanding of this field incomplete. Therefore, we reviewed the current methodology for assessing functional diversity in freshwater macroinvertebrate research. Our review showed that most papers quantified functional diversity using biological traits, among which feeding habits were the most common traits probably due to the assumed links between feeding and ecosystem functions. A large number of diversity measures have been applied for quantifying functional diversity of freshwater macroinvertebrate assemblages, among which Rao’s quadratic entropy looks like the most frequent. In most papers, functional diversity was positively related to taxon richness, and functional redundancy was a key concept in explaining this correlation. Most studies detected strong influence of the environmental factors as well as human impact on functional diversity. Finally, our review revealed that functional diversity research is biased towards European running waters and is hindered by yet insufficient information on the autecology of macroinvertebrates.

Koen MartensEditor-in-ChiefYou are now consulting Volume 600 of Hydrobio-logia. It has just appeared, in the middle of a fast-changing world of scientific publishing. A mere 10years ago, scientists wrote a manuscript, put threehard copies in an envelope and submitted it to ajournal. Subsequently, if all went well, it wasaccepted, publishers printed the paper, librariesbought the journals and scientists spent a few hoursevery week in the library going through newly arrivedjournals, and that was that, nothing to it, everybodyhappy. Or were they?In a relatively short period of time, many more anddifferent opportunities have arisen for authors,libraries and publishers. For starters, nearly allinternational journals now have online submissionand web-based editorial systems. More hidden fromauthors, but not of any less interest to them, is thestreamlined production process, almost invariablyoutsourced and using uniform software systems.Librarians also saw their metier changing fast: theyhad to adapt to the fact that there were significantshifts from paper to online consultation of journals(and one may well ask if paper versions of journalsare doomed), as well as from library-based funding ofpublication (journal subscriptions) to pay-per-paperin open-access forums. In addition, rather than sellindividual journals to individual libraries, publishersnow like to sell large packages of journals (a 1,000titles or more) to a consortium of users, for examplethe consortium of Canadian universities.What has all this meant to members of thescientific communities at large, who are, simulta-neously, authors, referees and readers? For you also,times have been a-changing. The most considerableof these over the last 10 years, I dare guess, havebeen an increased work load, higher pressure toproduce, and a decrease in time available to do whatyou are generally paid to do: to think! This hasresulted in some measurable effects. First, there is acommon decrease of what constitutes ‘‘the leastpublishable unit’’, because authors are forced topublish more and to do so in higher ranked journals.

The aquatic colonial stalked diatom, Didymosphenia geminata, has acquired notoriety in recent years because of huge increases in many rivers of temperate regions. However, in some streams in northern England it has probably or, in the case of the R. Coquet (Northumberland), certainly been abundant for many decades. The paper describes the nutrient environment and phosphatase activities of Didymosphenia in Stony Gill (N. Yorkshire), a fast-flowing stream draining an upland catchment with peaty soils overlying limestone. Organic phosphate formed 85% of the filtrable phosphate in the water during the study (January–August 2000), with a maximum in April. Colonies were most abundant in June, but had disappeared by August. Surface phosphomonoesterase (PMEase) and phosphodiesterase activities assayed from March to July showed low PMEase activity in early March, but otherwise both were high throughout the period and especially so in June and July. Use of BCIP-NBT staining procedure showed that PMEase activity occurred in the stalks. A more detailed study of colony structure and staining with material from the R. Coquet in June 2006 also showed marked PMEase activity, with staining localized in the upper part of the stalks and the cells remaining unstained. It is suggested that organic phosphate is hydrolyzed in the stalk and the inorganic phosphate passes to the cell via a central tube in the stalk. It seems likely that organic phosphate as a major P source is a key factor favouring the success of Didymosphenia. The possible impact of environmental changes in the catchment such as climatic warming, C loss from peat and atmospheric N deposition is discussed.

In recent years, it has been recognized that the laser diffraction gives valuable information on particle size distribution for all types of dry inorganic or even organic materials. With use of the laser diffraction and the laser granulometer, this paper presents the changes occurring in the granulometric distribution of algal agglomerates and the changes in values of percentiles 10, 50 and 90%, determined basing on volume distribution. While assessing the granulometric composition, the existence of a proportional relationship between the diameter values corresponding to the percentile of 10, 50 and 90% was observed. What is more, the obtained results give insight into the possibility of application of the general Avrami equation to describe the granulometric composition of the algal suspension through the analogy of crystals formation from saturated solutions. The analysis shows that the model described by the modified Avrami equation adequately matched the regression to the experimental data on the granulometric composition of algal suspensions. The values of the correlation coefficients were close to 1, which proves that the regression model explained nearly all cases by the dependent variable V i = F(d i ).

The Second International Symposium on Research and Management of Eutrophication in Coastal Ecosystems took place 20–23 June 2006 in Nyborg, Denmark. The Symposium was attended by more than 200 persons with a specific interest in eutrophication processes as well as a common interest in science-based management and implementation of nutrient reduction strategies. More than 120 oral presentations were made, mostly focussing on both science and management of nutrient enrichment and eutrophication. The papers in this Special Issue of Hydrobiologia are all based on presentations made at the Symposium.

This paper analyses the establishment of equilibrium states in relation to natural disturbances in epilithic diatom assemblages. Sterilized limestone bricks were exposed between April 2008 and 2009 in the Torna-stream and were removed one by one on every third day in the first month and then weekly until May 2010. Physical and chemical parameters were measured on the field and in laboratory. Equilibrium states were restricted to three separate months: July 2008, May and January 2009 taking the consistence of biomass (chlorophyll-a) into consideration. Cocconeis placentula sensu lato, Fragilaria vaucheriae, Gomphonema parvulum, G. olivaceum, Navicula gregaria, N. lanceolata, Nitzschia linearis, and Surirella brebissonii took part in the equilibrium assemblages, two of which dominated by a single species. Analyses of environmental constancy during equilibrium phases allowed concluding that resilience of a developed equilibrium phase may ensure biotic constancy even though the underpinning environmental background fluctuates at higher amplitude. The conclusions of our study on attached stream diatom assemblages are similar to those found for temperate lakes: equilibrium states are rare, unpredictable, ephemeral, may occur both in relatively stable and strongly fluctuating environments, and are mostly characterized by monodominance, but contrary to phytoplankton, their establishment requires a longer time to develop corresponding to differences in generation times.

The past few years have seen an absolute revolution in genomic technologies and their potential applications to ecology and evolutionary biology research. Such advances open up a range of opportunities for research on non-model organisms and individuals drawn from wild populations. This has resulted in exciting new research seeking to identify the genetic polymorphisms important in adaptation and speciation and how they are organised within the genome. Building on this, there is great interest in the extent to which similar evolutionary patterns are found across multiple populations, particularly whether consistent genetic mechanisms are associated with recurrent phenotypes. A powerful context for disentangling these mechanisms is to focus on highly diverse radiations, where phenotypes vary in and across environments. Therefore, the high diversity found within and among species of salmonid fishes such as charr (Salvelinus) make for an ideal ‘non’-model for genomic research. This paper outlines some of the current approaches available in ecological genomics and highlights some recent advances in salmonid research. It also suggests avenues for the sort of predictions that can be derived from ecological genomics, with the aim of understanding the genetics behind the fantastic diversity of salmonid fishes.

A Wetland Change Model has been developed to identify the vulnerability of coastal wetlands at broad spatial (regional to global (mean spatial resolution of 85 km)) and temporal scales (modelling period of 100 years). The model provides a dynamic and integrated assessment of wetland loss, and a means of estimating the transitions between different vegetated wetland types and open water under a range of scenarios of sea-level rise and changes in accommodation space from human intervention. This paper is an overview of key issues raised in the process of quantifying broad-scale vulnerabilities of coastal wetlands to forcing from sea-level rise discussing controlling factors of tidal range, sediment availability and accommodation space, identification of response lags and defining the threshold for wetland loss and transition.

In this paper, a monitoring and modelling concept for ecological optimized harbour dredging and fine sediment disposal in large rivers is presented. According to the concept, first a preliminary assessment should be performed previous to the dredging and dumping procedure to derive knowledge about the current status in hydrodynamics, morphology and instream habitat quality. During the performance of the maintenance work, a high-resolution monitoring program has to be organized to measure flow velocities, the suspended sediment concentrations and the extent of the occurring plume. These data can then be compared with natural suspended sediment conditions and serve as input data for numerical sediment transport modelling. Furthermore, bathymetric surveys and biotic sampling enable the detection of possible effects of dredging and disposal in the post-dumping stage. Based on sediment transport modelling approaches, short- to mid-term developments of the sediment plume can be predicted with an additional and final habitat evaluation at the end of the project. This concept was applied and optimized during the maintenance work at the case study winter harbour Linz at the Danube River. The findings of the presented study highlight the necessity of integrated monitoring and modelling approaches for harbour dredging especially in large river systems.