Trophic Transfer of Cd, Cu, Pb, Zn, P and Se in Dutch Storage Water Reservoirs.

Heavy metals are naturally omnipresent in aquatic systems. Excess amounts of heavy metals can accumulate in organisms of pollution impacted systems and transfer across a food web. Analysing the food web structure and metal contents of the organisms can help unravel the pathways of biomagnification or biodilution and gain insight in trophic linkages. We measured heavy metals and other elements in mussel bank detritus and organisms of the Biesbosch reservoirs (the Netherlands) and linked those to stable isotopic signatures. The heavy metal contents (cadmium, copper, lead, and zinc) were often lowest in benthivorous, omnivorous and piscivorous species (mainly fish); whereas, phosphorus contents were lower in the autotrophs. Mussel bank detritus contained the highest amounts of heavy metals. The heavy metals were negatively correlated with δ15N values. For selenium no clear trend was observed. Furthermore, there was a negative correlation between fish length and some heavy metals. Based on all 20 analysed elemental contents, similarities between species became apparent, related to niche or habitat. This study confirms that elemental contents of species can differ between feeding guilds and/or species, which can be attributed to metabolic and physiological processes. The organisms in higher trophic levels have adaptations preventing metal accumulation, resulting in lower contents. Within the fish species biodilution occurs, as most metal contents were lowest in bigger fish. Overall, the metals did not seem to biomagnify, but biodilute in the food web. Metal analyses combined with isotopic signatures could thus provide insights in metal transfer and possible trophic linkages within a system.

Initial decomposition of floating leaf blades of Nymphoides peltata (S.G. Gmel.) O. Kuntze (Menyanthaceae): causes, impact and succession.

Background: During a study on the outdoor floating leaf blade production of Nymphoides peltata (S.G. Gmel.) O. Kuntze (Fringed Water Lily), initial leaf blade decomposition was studied by simultaneously measuring infected, damaged and lost area of floating leaf blades. Methods: Data on initial decomposition over time were collected for all leaves during one growth season in four plots: two in outdoor mesocosms and two in an oxbow lake. Each leaf was tagged uniquely upon appearance in a plot. The vegetation in the mesocosms differed with respect to plant species, one contained a monoculture of N. peltata and the other N. peltata associated with Glyceria fluitans (L.) R. Br. and G. maxima (Hartm.) Holmb. The lake plots were situated within a monospecific N. peltata stand, differing in depth and position within the stand. Leaf length, visually estimated percentages of damaged area for each damage type, and decay of the tagged leaves were recorded bi-weekly. When the leaf blades sunk under the water surface or disappeared completely, they were no longer followed. Under water the leaves decayed and were consumed by snails completely, so contributing to the detritus food chain. Results: The observed causes of damage on floating leaves were consumption and/or damage by waterbirds (Fulica atra), pond snails, caterpillars (Elophila nymphaeata, Cataclysta lemnata), chironomid larvae (Cricotopus trifasciatus), infection by a phytopathogenic fungus (Septoria villarsiae), senescence by autolysis, and microbial decay. Successional changes in causes of leaf decomposition and impacts of different causes are discussed.

Plant traits and environment: floating leaf blade production and turnover of Nymphoides peltata (S.G. Gmel.) O. Kuntze (Menyanthaceae).

Background: Nymphaeid macrophytes, rooting in the sediment of water bodies and characterized by floating leaves, play an important role in wetland ecosystems. The present research deals with the effects of limited space, limited nutrient availability, water temperature and an unexpected inundation on the production, turnover and plasticity of floating leaves of the globally widespread species Nymphoides peltata (Fringed waterlily). Methods: The effects of these environmental conditions were studied in two plots in outdoor concrete tanks (CT1, CT2, mesocosms simulating occurrence in small ponds) and in two plots in the floodplain oxbow lake Bemmelse Strang (BS1, BS2). Plot CT1 was situated in a stand coexisting with helophytes, plot CT2 in a monospecific stand, plot BS1 in the center and plot BS2 at the open water border of a monospecific stand. All floating leaf blades within the plots were marked at appearance at the water surface and subsequently length, width and damage of each leaf and maximum and minimum water temperatures were measured bi-weekly. Area and biomass of leaf blades were calculated based on leaf length and width and were used to calculate turnover rates and production. Results: The growth period started in May and ended mid-October with continuous production of floating leaves during nearly the whole vegetation period. In the tanks the water level was very stable, but the lake underwent an inundation by river water, causing a sudden loss of existing leaves. Considering environmental conditions and based on the assumed ranking from low to high nutrient availability, the ranking of the plots was CT1, CT2, BS1, BS2. This order was found for maximum leaf life span and maximum leaf length, and the reverse order was found for number of leaves, new leaves per day and duration of the vegetation period. Turnover rates appeared to be relatively similar for plots CT1, CT2 and BS1, but for the deeper border plot BS2 lower ratios were found. These results indicate that increased enclosure with expected nutrient limitation causes (1) the production of high numbers of small leaves with larger totals for leaf area and biomass, (2) a shift towards increased sexual reproduction by the production of more flowering stem leaves.

Initial decomposition of floating leaf blades of waterlilies: causes, damage types and impacts.

The initial decomposition of large floating-leaved macrophytes, such as waterlilies, can be studied by following changes in leaf damage and area loss of leaf blades tagged in their natural environment. This approach was taken in the present study to examine the initial decomposition patterns of floating leaf blades of Nuphar lutea (L.) Sm., Nymphaea alba L. and Nymphaea candida C. Presl at three freshwater sites differing in nutrient status, alkalinity and pH. Floating leaf blades of the three plant species were tagged and numbered within established replicate plots and the leaf length, percentages and types of damage and decay of all tagged leaves were recorded weekly during the growing season. Microbial decay, infection by phytopathogenic fungi (Colletotrichum nymphaeae) and oomycetes (Pythium sp.), consumption by pond snails, and mechanical factors were the most important causes of leaf damage. Several types of succession comprising different causes of damage were distinguished during the season. For example, young floating leaves are affected by more or less specialized invertebrate species consuming leaf tissue, followed by non-specialized invertebrate species feeding on the damaged floating leaves. In the two investigated hardwater lakes the seasonal patterns of initial decomposition differed between Nymphaea and Nuphar.

Developing a list of invasive alien species likely to threaten biodiversity and ecosystems in the European Union.

The European Union (EU) has recently published its first list of invasive alien species (IAS) of EU concern to which current legislation must apply. The list comprises species known to pose great threats to biodiversity and needs to be maintained and updated. Horizon scanning is seen as critical to identify the most threatening potential IAS that do not yet occur in Europe to be subsequently risk assessed for future listing. Accordingly, we present a systematic consensus horizon scanning procedure to derive a ranked list of potential IAS likely to arrive, establish, spread and have an impact on biodiversity in the region over the next decade. The approach is unique in the continental scale examined, the breadth of taxonomic groups and environments considered, and the methods and data sources used. International experts were brought together to address five broad thematic groups of potential IAS. For each thematic group the experts first independently assembled lists of potential IAS not yet established in the EU but potentially threatening biodiversity if introduced. Experts were asked to score the species within their thematic group for their separate likelihoods of i) arrival, ii) establishment, iii) spread, and iv) magnitude of the potential negative impact on biodiversity within the EU. Experts then convened for a 2-day workshop applying consensus methods to compile a ranked list of potential IAS. From an initial working list of 329 species, a list of 66 species not yet established in the EU that were considered to be very high (8 species), high (40 species) or medium (18 species) risk species was derived. Here, we present these species highlighting the potential negative impacts and the most likely biogeographic regions to be affected by these potential IAS.

Thermal limits in native and alien freshwater peracarid Crustacea: The role of habitat use and oxygen limitation.

In order to predict which species can successfully cope with global warming and how other environmental stressors modulate their vulnerability to climate-related environmental factors, an understanding of the ecophysiology underpinning thermal limits is essential for both conservation biology and invasion biology.Heat tolerance and the extent to which heat tolerance differed with oxygen availability were examined for four native and four alien freshwater peracarid crustacean species, with differences in habitat use across species. Three hypotheses were tested: (1) Heat and lack of oxygen synergistically reduce survival of species; (2) patterns in heat tolerance and the modulation thereof by oxygen differ between alien and native species and between species with different habitat use; (3) small animals can better tolerate heat than large animals, and this difference is more pronounced under hypoxia.To assess heat tolerances under different oxygen levels, animal survival was monitored in experimental chambers in which the water temperature was ramped up (0.25°C min-1). Heat tolerance (CTmax) was scored as the cessation of all pleopod movement, and heating trials were performed under hypoxia (5 kPa oxygen), normoxia (20 kPa) and hyperoxia (60 kPa).Heat tolerance differed across species as did the extent by which heat tolerance was affected by oxygen conditions. Heat-tolerant species, for example, Asellus aquaticus and Crangonyx pseudogracilis, showed little response to oxygen conditions in their CTmax, whereas the CTmax of heat-sensitive species, for example, Dikerogammarus villosus and Gammarus fossarum, was more plastic, being increased by hyperoxia and reduced by hypoxia.In contrast to other studies on crustaceans, alien species were not more heat-tolerant than native species. Instead, differences in heat tolerance were best explained by habitat use, with species from standing waters being heat tolerant and species from running waters being heat sensitive. In addition, larger animals displayed lower critical maximum temperature, but only under hypoxia. An analysis of data available in the literature on metabolic responses of the study species to temperature and oxygen conditions suggests that oxygen conformers and species whose oxygen demand rapidly increases with temperature (low activation energy) may be more heat sensitive.The alien species D. villosus appeared most susceptible to hypoxia and heat stress. This may explain why this species is very successful in colonizing new areas in littoral zones with rocky substrate which are well aerated due to continuous wave action generated by passing ships or prevailing winds. This species is less capable of spreading to other waters which are poorly oxygenated and where C. pseudogracilis is the more likely dominant alien species. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13050/suppinfo is available for this article.

Plant traits and environment: floating leaf blade production and turnover of waterlilies.

Floating leaf blades of waterlilies fulfill several functions in wetland ecosystems by production, decomposition and turnover as well as exchange processes. Production and turnover rates of floating leaf blades of three waterlily species, Nuphar lutea (L.) Sm., Nymphaea alba L. and Nymphaea candida Presl, were studied in three freshwater bodies, differing in trophic status, pH and alkalinity. Length and percentages of leaf loss of marked leaf blades were measured weekly during the growing season. Area and biomass were calculated based on leaf length and were used to calculate the turnover rate of floating leaf blades. Seasonal changes in floating leaf production showed that values decreased in the order: Nymphaea alba, Nuphar lutea, Nymphaea candida. The highest production was reached for Nuphar lutea and Nymphaea alba in alkaline, eutrophic water bodies. The production per leaf was relatively high for both species in the acid water body. Nymphaea candida showed a very short vegetation period and low turnover rates. The ratio Total potential leaf biomass/Maximum potential leaf biomass (P/Bmax) of the three species ranged from 1.35-2.25. The ratio Vegetation period (Period with floating leaves)/Mean leaf life span ranged from 2.94-4.63, the ratio Growth period (Period with appearance of new floating leaves)/Vegetation period from 0.53-0.73. The clear differences between Nymphaea candida versus Nuphar lutea and Nymphaea alba, may be due to adaptations of Nymphaea candida to an Euro-Siberic climate with short-lasting summer conditions.

Phylogenetic relationships within the Phyllidiidae (Opisthobranchia, Nudibranchia).

The Phyllidiidae (Gastropoda, Heterobranchia, Nudibranchia) is a family of colourful nudibranchs found on Indo-Pacific coral reefs. Despite the abundant and widespread occurrence of many species, their phylogenetic relationships are not well known. The present study is the first contribution to fill the gap in our knowledge on their phylogeny by combining morphological and molecular data. For that purpose 99 specimens belonging to 16 species were collected at two localities in Indonesia. They were photographed and used to make a phylogeny reconstruction based on newly obtained cytochrome oxidase subunit (COI) sequences as well as sequence data from GenBank. All mitochondrial 16S sequence data available from GenBank were used in a separate phylogeny reconstruction to obtain information for species we did not collect. COI data allowed the distinction of the genera and species, whereas the 16S data gave a mixed result with respect to the genera Phyllidia and Phyllidiella. Specimens which could be ascribed to species level based on their external morphology and colour patterns showed low variation in COI sequences, but there were two exceptions: three specimens identified as Phyllidia cf. babai represent two to three different species, while Phyllidiella pustulosa showed highly supported subclades. The barcoding marker COI also confirms that the species boundaries in morphologically highly variable species such as Phyllidia elegans, Phyllidia varicosa, and Phyllidiopsis krempfi, are correct as presently understood. In the COI as well as the 16S cladogram Phyllidiopsis cardinalis was located separately from all other Phyllidiidae, whereas Phyllidiopsis fissuratus was positioned alone from the Phyllidiella species by COI data only. Future studies on phyllidiid systematics should continue to combine morphological information with DNA sequences to obtain a clearer insight in their phylogeny.

The phylogenetic position of a new species of Plakobranchus from West Papua, Indonesia (Mollusca, Opisthobranchia, Sacoglossa).

Plakobranchus papua Meyers-Muñoz & van der Velde, sp. n. from West Papua (Papua Barat province, Indonesia), is described based on its external morphology, colour pattern, internal anatomy, radula and reproductive system. In a molecular phylogenetic study specimens of this new species were compared with those of ten candidate taxa under the name Plakobranchus ocellatus van Hasselt, 1824. DNA analyses of COI mtDNA showed a clear distinction between Plakobranchus papua sp. n. and "Plakobranchus ocellatus". Plakobranchus papua, sp. n. also differed from all taxa that have been synonymised with Plakobranchus ocellatus. The genus is in dire need of taxonomic revision, preferably based on an integrative analysis involving morphology and DNA of all known Plakobranchus varieties.

Salinity as a barrier for ship hull-related dispersal and invasiveness of dreissenid and mytilid bivalves.

The benthic stages of Dreissenidae and Mytilidae may be dispersed over long distances while attached to ship hulls. Alternatively, larvae may be transported by water currents and in the ballast and bilge water of ships and vessels. To gain insight into dispersal potential and habitat suitability, survival of the benthic stages of two invasive dreissenid species (Dreissena polymorpha and Mytilopsis leucophaeata) and one mytilid species (Mytilus edulis) chosen based on their occurrence in fresh, brackish and sea water, respectively, were tested in relation to salinity. They were exposed to various salinities in mesocosms during three long-term experiments at outdoor temperatures. Mussel survival was studied without prior acclimation, reflecting conditions experienced when attached to ship hulls while travelling along a salinity gradient from fresh or brackish water to sea water, or vice versa. Initially, mussels react to salinity shock by temporarily closing their valves, suspending ventilation and feeding. However, this cannot be maintained for long periods and adaptation to higher salinity must eventually occur. Bivalve survival was monitored till the last specimen of a test cohort died. The results of the experiments allowed us to distinguish favorable (f.: high tolerance) and unfavorable (u.: no or low tolerance) salinity ranges in practical salinity units (PSU) for each species, viz. for D. polymorpha 0.2-6.0 PSU (f.), 7.0-30.0 PSU (u.), for M. leucophaeata 0.2-17.5 PSU (f.), 20.0-30.0 PSU (u.) and for M. edulis 10.5-36.0 PSU (f.), 0.2-9.0 and 40 PSU (u.). At the unfavorable salinities, all mussels died within 14 days of initial exposure with the exception of M. edulis (23-30 days). The maximum duration of survival of single specimens of D. polymorpha was 318 days at a salinity of 3.2 PSU, of M. leucophaeata 781 days at 15.0 PSU and of M. edulis 1052 days at 15.0 PSU. The number of days survived was compared with the duration of actual ship voyages to estimate the real world survival potentials of species dependent of salinity changes, travel distances and durations. The conclusion is that salinity shocks during the trip were survived within the favorable salinity range but that the species tolerate only for a few weeks the unfavorable salinity range. This functions as a barrier for dispersal. However, at faster and more frequent shipping in the future salinity can become no longer very important as a dispersal barrier.

A dominance shift from the zebra mussel to the invasive quagga mussel may alter the trophic transfer of metals.

Bioinvasions are a major cause of biodiversity and ecosystem changes. The rapid range expansion of the invasive quagga mussel (Dreissena rostriformis bugensis) causing a dominance shift from zebra mussels (Dreissena polymorpha) to quagga mussels, may alter the risk of secondary poisoning to predators. Mussel samples were collected from various water bodies in the Netherlands, divided into size classes, and analysed for metal concentrations. Concentrations of nickel and copper in quagga mussels were significantly lower than in zebra mussels overall. In lakes, quagga mussels contained significantly higher concentrations of aluminium, iron and lead yet significantly lower concentrations of zinc66, cadmium111, copper, nickel, cobalt and molybdenum than zebra mussels. In the river water type quagga mussel soft tissues contained significantly lower concentrations of zinc66. Our results suggest that a dominance shift from zebra to quagga mussels may reduce metal exposure of predator species.

Proteomic study of the brackish water mussel Mytilopsis leucophaeata.

BACKGROUND: We encountered the opportunity to study proteochemically a brackish water invertebrate animal, Mytilopsis leucophaeata, belonging to the bivalves which stem from the second half of the Cambrian Period (about 510 million years ago). This way, we were able to compare it with the vertebrate animal, the frilled shark (Chlamydoselachus anguineus) that stems from a much later period of geologic time (Permian: 245-286 MYA). RESULTS: The mussel contains a well-adapted system of protein synthesis on the ER, protein folding on the ER, protein trafficking via COPI or clathrin-coated vesicles from endoplasmic reticulum (ER) to Golgi and plasmalemma, an equally well-developed system of actin filaments that with myosin forms the transport system for vesicular proteins and tubulin, which is also involved in ATP-driven vesicular protein transport via microtubules or transport of chromosomes in mitosis and meiosis. A few of the systems that we could not detect in M. leucophaeata in comparison with C. anguineus are the synaptic vesicle cycle components as synaptobrevin, cellubrevin (v-snare) and synaptosomal associated protein 25-A (t-snare), although one component: Ras-related protein (O-Rab1) could be involved in synaptic vesicle traffic. Another component that we did not find in M. leucophaeata was Rab11 that is involved in the tubulovesicular recycling process of H+/K+-ATPase in C. anguineus. We have not been able to trace the H+/K+-ATPase of M. leucophaeata, but Na+/K+-ATPase was present. Furthermore, we have studied the increase of percent protein expression between 1,070 MYA (the generation of the Amoeba Dictyostelium discoideum) and present (the generation of the mammal Sus scrofa = wild boar). In this time span, three proteomic uprises did occur: 600 to 500 MYA, 47.5 to 4.75 MYA, and 1.4 to 0 MYA. The first uprise covers the generation of bivalves, the second covers gold fish, chicken, brine shrimp, house mouse, rabbit, Japanese medaka and Rattus norvegicus, and the third covers cow, chimpanzee, Homo sapiens, dog, goat, Puccinia graminis and wild boar. We hypothesise that the latter two uprises are related to geological and climate changes and their compensation in protein function expression. CONCLUSIONS: The proteomic and evolutionary data demonstrate that M. leucophaeata is a highly educatioanal animal to study.

Experimental quantification of long distance dispersal potential of aquatic snails in the gut of migratory birds.

Many plant seeds and invertebrates can survive passage through the digestive system of birds, which may lead to long distance dispersal (endozoochory) in case of prolonged retention by moving vectors. Endozoochorous dispersal by waterbirds has nowadays been documented for many aquatic plant seeds, algae and dormant life stages of aquatic invertebrates. Anecdotal information indicates that endozoochory is also possible for fully functional, active aquatic organisms, a phenomenon that we here address experimentally using aquatic snails. We fed four species of aquatic snails to mallards (Anas platyrhynchos), and monitored snail retrieval and survival over time. One of the snail species tested was found to survive passage through the digestive tract of mallards as fully functional adults. Hydrobia (Peringia) ulvae survived up to five hours in the digestive tract. This suggests a maximum potential transport distance of up to 300 km may be possible if these snails are taken by flying birds, although the actual dispersal distance greatly depends on additional factors such as the behavior of the vectors. We put forward that more organisms that acquired traits for survival in stochastic environments such as wetlands, but not specifically adapted for endozoochory, may be sufficiently equipped to successfully pass a bird's digestive system. This may be explained by a digestive trade-off in birds, which maximize their net energy intake rate rather than digestive efficiency, since higher efficiency comes with the cost of prolonged retention times and hence reduces food intake. The resulting lower digestive efficiency allows species like aquatic snails, and potentially other fully functional organisms without obvious dispersal adaptations, to be transported internally. Adopting this view, endozoochorous dispersal may be more common than up to now thought.

A comparative study of byssogenesis on zebra and quagga mussels: the effects of water temperature, salinity and light-dark cycle.

The quagga mussel (Dreissena rostriformis bugensis) and zebra mussel (Dreissena polymorpha) are invasive freshwater bivalves in Europe and North America. The distribution range of both Dreissena species is still expanding and both species cause major biofouling and ecological effects, in particular when they invade new areas. In order to assess the effect of temperature, salinity and light on the initial byssogenesis of both species, 24 h re-attachment experiments in standing water were conducted. At a water temperature of 25°C and a salinity of 0.2 psu, the rate of byssogenesis of D. polymorpha was significantly higher than that of D. rostriformis bugensis. In addition, byssal thread production by the latter levelled out between 15°C and 25°C. The rate of byssogenesis at temperatures<25°C was similar for both species. Neither species produced any byssal threads at salinities of 4 psu or higher. At a salinity of 1 psu and a water temperature of 15°C, D. polymorpha produced significantly more byssal threads than D. rostriformis bugensis. There was no significant effect of the length of illumination on the byssogenesis of either species. Overall, D. polymorpha produced slightly more byssal threads than D. rostriformis bugensis at almost all experimental conditions in 24 h re-attachment experiments, but both species had essentially similar initial re-attachment abilities. The data imply that D. rostriformis bugensis causes biofouling problems identical to those of D. polymorpha.

New threats of an old enemy: the distribution of the shipworm Teredo navalis L. (Bivalvia: Teredinidae) related to climate change in the Port of Rotterdam area, the Netherlands.

The effects of four climate change scenarios for the Netherlands on the distribution of the shipworm upstream of the Rhine-Meuse estuary are described. Global warming will cause dry and warmer summers and decreased river discharges. This will extend the salinity gradient upstream in summer and fall and may lead to attacks on wooden structures by the shipworm. Scenarios including one or two degree temperature increases by 2050 compared to 1990 with a weak change in the air circulation over Europe will lead to an increased chance of shipworm damage upstream from once in 36 years to once in 27 or 22 years, respectively; however, under a strong change in air circulation, the chance of shipworm damage increases to once in 6 or 3 years, respectively. The upstream expansion of the distribution of the shipworm will also be manifested in other northwest European estuaries and will be even stronger in southern Europe.

Together or alone?: foraging strategies in Caenorhabditis elegans.

A central goal in Life Sciences is to understand how genes encode behaviour and how environmental factors influence the expression of the genes concerned. To reach this goal a combined ecological, molecular biological and physiological approach is required in combination with a suitable model organism. Such an approach allows the elucidation of all parts of the complicated chain of events that lead from induction of gene expression to behaviour, i.e. from environmental stimulus, sensory organs and extracellular and intracellular neuronal signal processing to activation of effector organs. A particularly good model species with which to take this approach is the nematode Caenorhabditis elegans, as it has been described in great detail at the genomic, cellular and behavioural levels. Different strains of C. elegans display prominent behavioural variation in foraging behaviour. Some strains will form social feeding groups when subjected to certain environmental stimuli, while others do not. This variation is due to the existence of just two isoforms of the gene npr-1, namely 215F and 215V. Here, we describe these behavioural variations at the molecular and cellular levels to attempt to determine the environmental inputs that cause aggregation of these small nematodes. As many different stimuli affect aggregation either positively or negatively, aggregation behaviour seems to be displayed when it improves survival chances. However, not much is known about the ecological context in which C. elegans lives. Investigation of the habitats of different strains of C. elegans would help us to understand why and how a specific foraging strategy enhances survival. The relatively well-understood molecular pathways that direct its social feeding behaviour make C. elegans a highly suitable model organism to test ecological and behavioural hypotheses about the mechanisms that differentiate between aggregation and solitary behaviours.

Brine-induced mortality of non-indigenous invertebrates in residual ballast water.

All transoceanic vessels entering the Great Lakes are required to manage ballast water and ballast tank residuals with ballast water exchange and tank flushing, respectively. While these management procedures effectively reduce the density and richness of biota in ballast waters and thereby reduce the risk of transferring non-indigenous species, some ships are unable to uniformly manage all tanks. Laboratory experiments were conducted to evaluate sodium chloride brine as an emergency treatment for ballast tanks with non-compliant residuals. Invertebrate communities collected from i) Detroit River, ii) exchanged ballast tanks arriving in the Great Lakes, and iii) North Sea ports, were exposed to a range of brine concentrations (15-115‰) until complete mortality was reached. Results indicate that a 1-h exposure to 115‰ brine is a broadly effective treatment (>99.9% mortality) regardless of treatment temperature, taxonomic group, or species' source habitat salinity. A median of 0.00% (range 0.00-5.33) of individuals are expected to survive treatment and the expected number of viable individuals released after treatment is within Canadian and proposed international discharge standards. Before implementation, validation with ship-scale trials is recommended.

Effects of reduced nitrogen and sulphur deposition on the water chemistry of moorland pools.

To assess changes as a result of reduced acidifying deposition, water chemistry data from 68 Dutch moorland pools were collected during the periods 1983-1984 and 2000-2006. Partial recovery was observed: nitrate- and ammonium-N, sulphur and aluminium concentrations decreased, while pH and alkalinity increased. Calcium and magnesium concentrations decreased. These trends were supported by long term monitoring data (1978-2006) of four pools. Increased pH correlated with increases in orthophosphate and turbidity, the latter due to stronger coloration by organic acids. Increased ortho-phosphate and turbidity are probably the result of stronger decomposition of organic sediments due to decreased acidification and may hamper full recovery of moorland pool communities. In addition to meeting emission targets for NO(x), NH(x) and SO(x), restoration measures are still required to facilitate and accelerate recovery of acidified moorland pools.

Explaining abundance-occupancy relationships in specialists and generalists: a case study on aquatic macroinvertebrates in standing waters.

1. A positive interspecific abundance-occupancy relationship is one of the most robust patterns in macroecology. Yet, the mechanisms driving this pattern are poorly understood. Here, we use biological traits of freshwater macroinvertebrates to gain a mechanistic understanding and disentangle the various explanations. We ask whether mechanisms underlying the abundance-occupancy relationship differ between species, and whether information on individual species can be used to explain their contribution to the interspecific relationship. 2. We test the hypothesis that the importance of metapopulation dynamics or niche differences in explaining the relationship differs between species, varying in relation to their habitat breadth. In addition, we analyse how a species' biological traits shape its habitat breadth and its abundance and occupancy. 3. The abundance and occupancy of the 234 different aquatic macroinvertebrate species were strongly and positively related. Marked differences were found between habitat specialists and habitat generalists in the goodness-of-fit of abundance-occupancy relationships. The occupancy-frequency distribution was bimodal for habitat generalists, allowing 'satellite species' to be distinguished from 'core species'. 4. Habitat generalists appeared to be more widespread but less abundant than habitat specialists, suggesting that the jack-of-all-trades may be master-of-none. Species traits (trophic position and other life-history traits) explained a significant part of the variation around the general relationship. Among habitat specialists, more species showed synchronized life cycles, a low dispersal capacity or clustered oviposition, being better adapted to predictable habitats. Among habitat generalists, more species had long-lived adults, spreading reproductive effort in time and space, and were strong dispersers, being better adapted to unpredictable habitats. 5. Interspecific abundance-occupancy relationships can be best understood by examining the contribution of individual species. For habitat specialists, the interplay between niche differences (diet and habitat use) and the underlying spatial distribution of environmental conditions result in competitive displacement and differences in species' success. For habitat generalists, differences in colonization and extinction rates between species are more important. Therefore, both metapopulation dynamics and niche differences can operate simultaneously but apply to different species, thus constituting different endpoints of the same continuum.

Population dynamics of the migratory fish Prochilodus lineatus in a neotropical river: the relationships with river discharge, flood pulse, El Niño and fluvial megafan behaviour

The relative importance of flood pulse dynamics and megafan behaviour for the Sábalo (Prochilodus lineatus) catches in the neotropical Pilcomayo River is studied. The Sábalo catches can mainly be explained by decreased river discharges in the preceding years resulting in smaller inundated areas during rainy season floods and thereby in a decreased area of feeding grounds for the fishes. The decreased river discharges and the related decline of Sábalo catches in the 1990's can be linked to the 90-95 El Niño event. In 2007 the Sábalo catches were comparable to the catches before the "El Niño" event. The connectivity (continuity) between the main river and flood plain areas, which is influenced by sedimentation processes, is also of great importance and very probably plays a more important role since the late 1990's.

Se ha estudiado la importancia relativa de la dinámica del pulso de inundación y el comportamiento del sistema megafan para las capturas del Sábalo (Prochilodus lineatus) en el río Pilcomayo. Las capturas del Sábalo puede explicarse fundamentalmente por los bajos caudales del río en los años anteriores, resultando en menores superficies de las zonas inundadas durante la temporada de lluvia y por lo tanto en una área menor de alimentación para los peces. La disminución del caudal del río y la declinación relativa de capturas de Sábalo en los años 1990 pueden estar relacionadas con el 90-95 evento de El Niño. En 2007, la captura de Sábalo fue comparable a las capturas antes del evento de "El Niño". La conectividad (continuidad) entre el río principal y las llanuras aluviales, que son influenciadas por los procesos de sedimentación, son también de gran importancia y muy probablemente juegan un papel muy importante desde finales de los años '90.