Impacts of freshwater wetlands on water quality: A landscape perspective

In this article, we suggest that a landscape approach might be useful in evaluating the effects of cumulative impacts on freshwater wetlands. The reason for using this approach is that most watersheds contain more than one wetland, and effects on water quality depend on the types of wetlands and their position in the landscape. Riparian areas that border uplands appear to be important sites for nitrogen processing and retention of large sediment particles. Fine particles associated with high concentrations of phosphorus are retained in downstream wetlands, where flow rates are slowed and where the surface water passes through plant litter. Riverine systems also may play an important role in processing nutrients, primarily during flooding events. Lacustrine wetlands appear to have the least impact on water quality, due to the small ratio of vegetated surface to open water. Examples are given of changes that occurred when the hydrology of a Maryland floodplain was altered.     

Is boldness affected by group composition in young-of-the-year perch (Perca fluviatilis)?

In young-of-the-year perch (Perca fluviatilis), individuals within groups differed in the degree of boldness, estimated by habitat utilisation and feeding activity in visual contact with a potential predator. We looked at changes in individual behaviour in connection with change of group composition. During the first period, perch were randomly assigned to groups, and time spent in open habitat versus in vegetation and number of prey attacks were registered. The perch were then categorised into personality types (shy, bold, intermediate) according to their behaviour. During the second period, fish were observed when sorted into new groups, each containing only one personality type. Shy individuals showed the largest changes in behaviour, and increased both the time spent in the open and the number of prey attacks when placed into the new groups. Feeding activity in shy fish during the second period was affected by group composition during the first period. After regrouping, bold individuals decreased their time in the open, whereas intermediate individuals did not change behaviour. Time in the open habitat was, to some extent, influenced by the behaviour of the other members of the group, but number of prey attacks was not. The behaviour of fish of the different personality types we have defined in this study seemed to be based on innate traits, but also modified by the influence of other group members and by habituation to the environment.Communicated by J.Krause     

Identification of some plasticizers compounds in landfill leachate

In this work it was described a simple method for extraction of plasticizer compounds (mainly phthalate esters and bisphenol A (BPA)) from landfill leachate samples. The samples were submitted to an extraction procedures based on precipitation, solid phase extraction (SPE) and ionic exchange chromatography (IEC). Firstly the landfill leachate sample was acidified by addition of HCl concentrated, in order to precipitate the organic compounds that are less soluble in water. The precipitate was washed with several solvents. The aqueous phase was then submitted to SPE with XAD-4 resin and IEC with Amberlyst A-27 resin. The instrumental analysis was performed by gas chromatography with mass spectrometer detector (GC/MSD) and the compounds were identified by the GC/MSD library (Wiley) and by using some standard substances. These methodologies allow the isolation and identification of the following compounds: dioctylphthalate, diisobutilphthalate, BPA, benzoic acid, palmitic acid and diisopentylphthalate. The methods are very simple, rapid and selective, for plasticizers extraction from landfill leachate matrices.     

Social influence on the correlation between behaviours in young-of-the-year perch

The connection between risk-taking behaviour and exploratory behaviour in young-of-the-year perch (Perca fluviatilis) was studied in aquarium experiments to see whether individual behaviour patterns could be identified in this species and also to investigate how individual behaviour is influenced by their social environment. Risk-taking was defined as the time spent foraging in an open area vs hiding in the vegetation in the presence of a piscivore. Explorative behaviour was measured as latency to enter a passage leading to an unknown area. Groups of four fish were used for the observations, and both behaviours measured were positively correlated with the mean scores of these behaviours in the other group members. Risk-taking and explorative behaviours were correlated only when data was adjusted for the behaviour of the other group members. Individuals that spent more time in the open than their companions also tended to be faster than the others to enter the passage to the unknown area and vice versa. The results indicate that there are consistent individual differences in boldness in perch, but also that behaviour could be modified according to the behaviour of group members.     

A bioassay approach to determine the dioxin-like activity in sediment extracts from the Danube River: ethoxyresorufin-O-deethylase induction in gill filaments and liver of three-spined sticklebacks (Gasterosteus aculeatus L.)

Sediment samples from the upper Danube River in Germany have previously been characterized as ecotoxicologically hazardous and contaminants in these sediments may contribute to the observed decline of fish populations in this river section. For the investigation of sediment toxicity there is a need for development, standardization and implementation of in vivo test systems using vertebrates. Therefore, the main objective of this study was to apply and evaluate a recently established fish gill EROD assay as a biomarker in sediment toxicity assessment by using extracts of well characterised sediment samples from the upper Danube River. This to our knowledge is the first application of this novel assay to sediment extracts. Sediments from four different sites along the upper Danube River were Soxhlet-extracted with acetone and dissolved in DMSO. Three-spined sticklebacks (Gasterosteus aculeatus L.) were exposed for 48 h to various concentrations of the extracts, to the positive control beta-naphthoflavone or to the solvent. Measurements of EROD activity in gill filaments and liver microsomes followed the exposure. Concentration-dependent induction of EROD in both gill and liver was found for all sediment extracts. The highest EROD-inducing potency was determined for extracts of sediments from the sites "Opfinger See" and "Sigmaringen" and the EROD activities in gill and liver correlated well. The results from the gill and liver assays were in accordance with in vitro results of previous investigations. The EROD activities measured in the present study corresponded with the concentrations of PAHs, PCBs and PCDD/Fs in the sediment samples derived in a previous study. The sticklebacks in this study were in the reproductive phase and a stronger EROD induction was obtained in the females than in the males. Implementation of the EROD assay in testing of sediment extracts gave highly reliable results which make this assay an ecotoxicologically relevant method for assessment of contamination with Ah receptor agonists in sediments.     

Quantitative determination of fluorochemicals in municipal landfill leachates

Twenty-four fluorochemicals were quantified in landfill leachates recovered from municipal refuse using an analytical method based on solid-phase extraction, dispersive-carbon sorbent cleanup, and liquid chromatography/tandem mass spectrometry. The method was applied to six landfill leachates from four locations in the US as well as to a leachate generated by a laboratory bioreactor containing residential refuse. All seven leachates had the common characteristic that short-chain (C₄-C₇) carboxylates or sulfonates were greater in abundance than their respective longer-chain homologs (?C₈). Perfluoroalkyl carboxylates were the most abundant (67 ± 4% on a nanomolar (nM) basis) fluorochemicals measured in leachates; concentrations of individual carboxylates reaching levels up to 2800 ng L⁻¹. Perfluoroalkyl sulfonates were the next most abundant class (22 ± 2%) on a nM basis; their abundances in each of the seven leachates derived from municipal refuse were greater for the shorter-chain homologs (C₄ and C₆) compared to longer-chain homologs (C₈ and C₁₀). Perfluorobutane sulfonate concentrations were as high as 2300 ng L⁻¹. Sulfonamide derivatives composed 8 ± 2.1% (nM basis) of the fluorochemicals in landfill leachates with methyl (C₄ and C₈) and ethyl (C₈) sulfonamide acetic acids being the most abundant. Fluorotelomer sulfonates (6:2 and 8:2) composed 2.4 ± 1.3% (nM basis) of the fluorochemicals detected and were present in all leachates.     

Mineralization of particulate organic matter derived from coral-reef organisms in reef sediments of the Gulf of Aqaba

In situ and laboratory incubation experiments in a fringing reef in the Gulf of Aqaba were performed to study degradation rates of particulate organic matter in reef sediments. Coral mucus, clam eggs, and zooxanthellae were used as model particulate organic compounds for these experiments. Aerobic and anaerobic mineralization rates were calculated by dissolved inorganic carbon (DIC) and O₂ fluxes from the sediments under different particulate organic matter additions. Fast enhancement (approximately twofold) of O₂ and DIC fluxes were found with the addition of coral mucus and clam eggs compared with control incubations without addition. Most of the degradation is believed to have occurred anaerobically rather than aerobically (DIC:O₂ ratios were 4.3-28.1). Higher degradation rates of coral mucus and clam eggs were estimated in carbonate sediment than in silicate sediment (1.2-1.6-fold), which was attributed to the different physical and chemical properties of both sediments. Our study shows the significance of the reef sediment as a suitable site for microbial degradation of particulate organic material excreted from different reef community organisms. This may increase the regeneration of nutrients in the reef environment necessary to sustain high biological productivity.     

The influence of experience on risk taking: results from a common-garden experiment on populations of Eurasian perch

Predation is often thought of as an unforgiving and strong selective force, quickly selecting against maladaptive behaviour in the prey. It is argued that experience is likely to have low influence on the phenotypic response to predation, as failing to react correctly to a predator may mean death to the prey and no second chance to learn and correct the behaviour. Individuals from different populations of Eurasian perch are known to differ in risk-taking behaviour. Variation in predation pressure has been suggested as a key factor causing these differences, but little is known about the underlying mechanism by which predation generates risk-taking phenotypes in perch. We compared the degree of boldness between two natural populations of Eurasian perch, living under different predation regimes, and the same populations hatched and reared under identical conditions, free from predation. By this common-garden approach, we sought to investigate patterns in the influence of inheritance and experience on boldness phenotype. The wild fish differed in risk taking, with fish from the low predation-risk population acting bolder than fish from the high-risk environment. In the reared fish, both populations behaved equally bold. Only the fish originating from the high predation population showed different behaviour when comparing wild and reared ecotypes. Our results suggest that experience has an important impact on the response to predators and that geographic variation in risk taking between populations of Eurasian perch to a high degree is shaped by adjustments to the current environment. Habituation had an effect of risk-taking behaviour over the experimental period, but consistent differences between individuals were also found. Furthermore, we also show, by the estimation of variance components, that the behaviour we observe is affected by a range of random effects, such as aquaria and group membership, that in concert shapes the behaviour of an individual perch.     

Mineralization of particulate organic matter derived from coral-reef organisms in reef sediments of the Gulf of Aqaba

In situ and laboratory incubation experiments in a fringing reef in the Gulf of Aqaba were performed to study degradation rates of particulate organic matter in reef sediments. Coral mucus, clam eggs, and zooxanthellae were used as model particulate organic compounds for these experiments. Aerobic and anaerobic mineralization rates were calculated by dissolved inorganic carbon (DIC) and O₂ fluxes from the sediments under different particulate organic matter additions. Fast enhancement (approximately twofold) of O₂ and DIC fluxes were found with the addition of coral mucus and clam eggs compared with control incubations without addition. Most of the degradation is believed to have occurred anaerobically rather than aerobically (DIC:O₂ ratios were 4.3–28.1). Higher degradation rates of coral mucus and clam eggs were estimated in carbonate sediment than in silicate sediment (1.2–1.6-fold), which was attributed to the different physical and chemical properties of both sediments. Our study shows the significance of the reef sediment as a suitable site for microbial degradation of particulate organic material excreted from different reef community organisms. This may increase the regeneration of nutrients in the reef environment necessary to sustain high biological productivity.     

Photosynthetic performance of giant clams, Tridacna maxima and T. squamosa, Red Sea

Two species of giant clams, Tridacna maxima and T. squamosa, coexist in the Red Sea, but exhibit distinctly different depth distributions: T. maxima mostly occurs in shallow waters (reef flat and edge), while T. squamosa may occur down to the lower fore-reef slope. Giant clams have been described as mixotrophic, capable of both filter-feeding and photosynthesis due to algal symbionts (zooxanthellae), therefore, observed depth preferences were investigated in relation to possible differences in autotrophy vs. heterotrophy. This study was conducted from April to June 2004, at the reef near the Marine Science Station, Aqaba, Gulf of Aqaba, Red Sea, and in May 2007, at a reef near Dahab, Sinai Peninsula, Egypt. In situ measurements using a submersible pulse amplitude modulated fluorometer (Diving PAM), revealed no significant differences in effective PSII quantum yield (ΔF/Fm′) and relative electron transport rates (ETR) between the two species; but rapid light curves (ETR vs. light, photosynthetically active irradiance, PAR) showed significant differences in maximum photosynthetic rates (ETR_max), with 20% higher values in T. maxima. Chamber incubations displayed higher net and gross oxygen production by T. maxima (88.0 and 120.3 μmol O₂ cm⁻² mantle area day⁻¹) than T. squamosa (56.7 and 84.8 μmol O₂ cm⁻² mantle area day⁻¹); even under shading conditions (simulated depth of 20 m) T. maxima still achieved 93% of the surface gross O₂ production, whereas T. squamosa reached only 44%. A correlation was found between ETR and net photosynthesis measured as oxygen production (T. maxima: R ² = 0.53; T. squamosa: R ² = 0.61). Calculated compensation depth (CD) (gross photosynthesis equals respiration) in T. maxima (16 m) matches the maximum depth of occurrence in this study (17 m). By contrast, the CD of T. squamosa (9 m) was much shallower than the maximum vertical range (42 m). Findings suggest T. maxima is a strict functional photoautotroph limited by light, whereas T. squamosa is a mixotroph whose photoautotrophic range is extended by heterotrophy. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.