Lipid extraction has little effect on the delta N-15 of aquatic consumers

Proper application of stable isotopes (e. g., delta N-15 and delta C-13) to food web analysis requires an understanding of all nondietary factors that contribute to isotopic variability. Lipid extraction is often used during stable isotope analysis (SIA), because synthesized lipids have a low delta C-13 and can mask the delta C-13 of a consumer's diet. Recent studies indicate that lipid extraction intended to adjust delta C-13 may also cause shifts in delta N-15, but the magnitude of and reasons for the shift are highly uncertain. We examined a large data set (n = 854) for effects of lipid extraction (using Bligh and dyer's [ 1959] chloroform-methanol solvent mixtures) on the delta N-15 of aquatic consumers. We found no effect of chemically extracting lipids on the delta N-15 of whole zooplankton, unionid mussels, and fish liver samples, and found a small increase in fish muscle delta N-15 of similar to 0.4%. We also detected a negative relationship between the shift in delta N-15 following extraction and the C:N ratio in muscle tissue, suggesting that effects of extraction were greater for tissue with lower lipid content. As long as appropriate techniques such as those from Bligh and dyer (1959) are used, effects of lipid extraction on delta N-15 of aquatic consumers need not be a major consideration in the SIA of food webs.

Multiproxy evidence for terrestrial and aquatic ecosystem responses during the 8.2 ka cold event as recorded at Hojby So, Denmark

A sediment succession from Hojby So, a lake in eastern Denmark, covering the time period 9400-7400 cal yr BP was studied using high-resolution geochemistry, magnetic susceptibility, pollen, macrofossil, diatom, and algal pigment analysis to investigate responses of the terrestrial and aquatic ecosystems to the 8.2 ka cold event. A reduced pollen production by thermophilous deciduous tree taxa in the period c. 8250-8000 cal yr BP reveal that the forest ecosystem was affected by low temperatures during the summer and winter/early-spring seasons. This finding is consistent with the timing of the 8.2 ka cold event as registered in the Greenland ice cores. At Hojby So, the climate anomaly appears to have started 200-250 yr earlier than the 8.2 ka cold event as the lake proxy data provide strong evidence for a precipitation-induced distinct increase in catchment soil erosion beginning around 8500 cal yr BP. Alteration of the terrestrial environment then resulted in a major aquatic ecosystem change with nutrient enrichment of the lake and enhanced productivity, which lasted until c. 7900 cal yr BP. (C) 2009 University of Washington. Published by Elsevier Inc. All rights reserved.

How to estimate scavenger fish abundance using baited camera data

Baited cameras are often used for abundance estimation wherever alternative techniques are precluded, e.g. in abyssal systems and areas such as reefs. This method has thus far used models of the arrival process that are deterministic and, therefore, permit no estimate of precision.
Furthermore, errors due to multiple counting of fish and missing those not seen by the camera have restricted the technique to using only the time of first arrival, leaving a lot of data redundant. Here, we reformulate the arrival process using a stochastic model, which allows the precision of abundance
estimates to be quantified. Assuming a non-gregarious, cross-current-scavenging fish, we show that prediction of abundance from first arrival time is extremely uncertain. Using example data, we show
that simple regression-based prediction from the initial (rising) slope of numbers at the bait gives good precision, accepting certain assumptions. The most precise abundance estimates were obtained
by including the declining phase of the time series, using a simple model of departures, and taking account of scavengers beyond the camera’s view, using a hidden Markov model.

Recent data suggest no further recovery in North Sea Large Fish Indicator

We detail the calculations of North Sea Large Fish Indicator values for 2009-2011, demonstrating an apparent stall in recovery. Therefore, recovery to the Marine Strategy Framework Directive's good environmental status of 0.3 by the 2020 deadline now looks less certain and may take longer than was expected using data from 2006 to 2008.

Freshwater Reservoir Effects on the Re-Dating of the Eurasian Steppe Cultures: New Data for the Prehistoric Sites of Kazakhstan and South of Siberia

Freshwater reservoir effects (FRE) can cause a major problem with radiocarbon dating human skeletal material in the Eurasian steppe. Recent research has demonstrated that, for the Eneolithic to Early Bronze Age sites of North-Eastern Kazakhstan, the maximum fish-herbivore freshwater reservoir offset observed equals 301±47 14C yrs, as such indicating that 14C dates from aquatic and human samples from the area apparently need to be interpreted with caution as they are likely to be affected by the offset. The current paper presents the new data on the FRE of the Eneolithic to the Early Iron Age sites of Kazakhstan and South of Siberia.

Silver nanoparticles flow in an aquatic trophic chain

Silver nanoparticles (AgNP) have been produced and applied in a variety of products ranging from personal care products to food package containers, clothing and medicine utilities. The antimicrobial function of AgNP makes it very useful to be applied for such purposes. Silver (Ag) is a non-essential metal for organisms, and it has been historically present in the environment at low concentrations. Those concentrations of silver increased in the last century due to the use of Ag in the photographic industry and lately are expected to increase due to the use of AgNPs in consumer products. The presence of AgNP in the aquatic environment may pose a risk for aquatic species, and the effects can vary from lethal to sublethal effects. Moreover, the contact of aquatic organisms with AgNP may not cause immediately the death of individuals but it can be accumulated inside the animals and consequently transferred within the food chain. Considering this, the objective of this work was to study the transfer of silver nanoparticles in comparison to silver ions, which was used as silver nitrate, within an aquatic food chain model. To achieve this goal, this study was divided into four steps: the toxicity assessment of AgNP and AgNO3 to aquatic test-species, the bioaccumulation assessment of AgNP and AgNO3 by Pseudokirchneriella subcapitata and Daphnia magna under different exposure scenarios, and finally the evaluation of the trophic transfer of Ag through an experimental design that included the goldfish Carassius auratus in a model trophic chain in which all the species were exposed to the worse-case scenario. We observed that the bioconcentration of Ag by P. subcapitata is mainly driven by ionic silver, and that algae cannot internalize these AgNPs, but it does internalizes dissolved Ag. Daphnia magna was exposed to AgNP and AgNO3 through different exposure routes: water, food and both water and food. The worse-case scenario for Daphnia Ag bioaccumulation was by the joint exposure of contaminated water and food, showing that Ag body burdens were higher for AgNPs than for AgNO3. Finally, by exposing C. auratus for 10 days through contaminated water and food (supplied as D. magna), with another 7 days of depuration phase, it was concluded that the 10 days of exposure were not enough for fish to reach a plateau on Ag internal concentration, and neither the 7 days of elimination were sufficient to cause total depuration of the accumulated Ag. Moreover, a higher concentration of Ag was found in the intestine of fish when compared with other organs, and the elimination rate constant of AgNP in the intestine was very low. Although a potential for trophic transfer of AgNP cannot be suggested based in the data acquired in this study, there is still a potential environmental risk for aquatic species.

Assessment of the mineralogenic toxicity of aquatic pollutants

In ecotoxicology a major focus is in the aquatic environment, not only because it presents a great economic value to man but it is an ecosystem widely affected by the growing anthropogenic pollution. Most of the studies performed relate to adverse effects in development, reproductive or endocrine disruption but little is known about the possible effects in bone formation and skeletal development. In this study, we set out to evaluate the effects of 8 aquatic pollutants on the skeletal development using an in vivo system, the zebrafish larvae aged 20 days post-fertilization, through chronic exposure. Several endpoints were considered such as the cumulative mortality, total length, occurrence of skeletal deformities and marker gene expression. We were able to establish LD50 values for some pollutants, like 3-methylcholanthrene, lindane, diclofenac, cobalt and vanadate and found that the total length was not affected by any of the pollutants tested. Cobalt was the most harmful chemical to affect hatching time, severely affecting the ability of the zebrafish embryos to hatch and overall the number of deformities increased upon exposure to tested chemicals but no patterns of deformities were identified. We also propose that 3-methylcholanthrene has an osteogenic effect, affecting osteoblast and osteoclast function and that op levels can act as a mediator of 3-methylcholanthrene toxic stress to the osteoblast. In turn we found naphthalene to probably have a chondrogenic effect. Our results provided new insights into the potential osteotoxicity of environmental pollutants. Future studies should aim at confirming these preliminary data and at determining mechanisms of osteotoxicity.

Ecotoxicological aspects related to the presence of pharmaceuticals in the aquatic environment

Pharmaceuticals are biologically active and persistent substances which have been recognized as a continuing threat to environmental stability. Chronic ecotoxicity data as well as information on the current distribution levels in different environmental compartments continue to be sparse and are focused on those therapeutic classes that are more frequently prescribed and consumed. Nevertheless, they indicate the negative impact that these chemical contaminants may have on living organisms, ecosystems and ultimately, public health. This article reviews the different contamination sources as well as fate and both acute and chronic effects on non-target organisms. An extensive review of existing data in the form of tables, encompassing many therapeutic classes is presented.

Development of paper-based color test-strip for drug detection in aquatic environment: Application to oxytetracycline

The wide use of antibiotics in aquaculture has led to the emergence of resistant microbial species. It should be avoided/minimized by controlling the amount of drug employed in fish farming. For this purpose, the present work proposes test-strip papers aiming at the detection/semi-quantitative determination of organic drugs by visual comparison of color changes, in a similar analytical procedure to that of pH monitoring by universal pH paper. This is done by establishing suitable chemical changes upon cellulose, attributing the paper the ability to react with the organic drug and to produce a color change. Quantitative data is also enabled by taking a picture and applying a suitable mathematical treatment to the color coordinates given by the HSL system used by windows. As proof of concept, this approach was applied to oxytetracycline (OXY), one of the antibiotics frequently used in aquaculture. A bottom-up modification of paper was established, starting by the reaction of the glucose moieties on the paper with 3-triethoxysilylpropylamine (APTES). The so-formed amine layer allowed binding to a metal ion by coordination chemistry, while the metal ion reacted after with the drug to produce a colored compound. The most suitable metals to carry out such modification were selected by bulk studies, and the several stages of the paper modification were optimized to produce an intense color change against the concentration of the drug. The paper strips were applied to the analysis of spiked environmental water, allowing a quantitative determination for OXY concentrations as low as 30 ng/mL. In general, this work provided a simple, method to screen and discriminate tetracycline drugs, in aquaculture, being a promising tool for local, quick and cheap monitoring of drugs.

Water quality and ecology of the River Lee: mass balance and a review of temporal and spatial data

A regional overview of the water quality and ecology of the River Lee catchment is presented. Specifically, data describing the chemical, microbiological and macrobiological water quality and fisheries communities have been analysed, based on a division into river, sewage treatment works, fish-farm, lake and industrial samples. Nutrient enrichment and the highest concentrations of metals and micro-organics were found in the urbanised, lower reaches of the Lee and in the Lee Navigation. Average annual concentrations of metals were generally within environmental quality standards although, oil many occasions, concentrations of cadmium, copper, lead, mercury and zinc were in excess of the standards. Various organic substances (used as herbicides, fungicides, insecticides, chlorination by-products and industrial solvents) were widely detected in the Lee system. Concentrations of ten micro-organic substances were observed in excess of their environmental quality standards, though not in terms of annual averages. Sewage treatment works were the principal point source input of nutrients. metals and micro-organic determinands to the catchment. Diffuse nitrogen sources contributed approximately 60% and 27% of the in-stream load in the upper and lower Lee respectively, whereas approximately 60% and 20% of the in-stream phosphorus load was derived from diffuse sources in the upper and lower Lee. For metals, the most significant source was the urban runoff from North London. In reaches less affected by effluent discharges, diffuse runoff from urban and agricultural areas dominated trends. Flig-h microbiological content, observed in the River Lee particularly in urbanised reaches, was far in excess of the EC Bathing Water Directive standards. Water quality issues and degraded habitat in the lower reaches of the Lee have led to impoverished aquatic fauna but, within the mid-catchment reaches and upper agricultural tributaries, less nutrient enrichment and channel alteration has permitted more diverse aquatic fauna.

Macrophyte community structure and species occurrence in relation to environmental determinants in the ephemeral aquatic habitats of Gavdos, Greece

The aims of this study were to explore the environmental factors that determine the distribution of plant communities in temporary rock pools and provide a quantitative analysis of vegetation-environment relationships for five study sites on the island of Gavdos, southwest of Crete, Greece. Data from 99 rock pools were collected and analysed using Two-Way Indicator Species Analysis (TWINSPAN), Detrended Correspondence Analysis (DCA) and Canonical Correspondence Analysis (CCA) to identify the principal communities and environmental gradients that are linked to community distribution. A total of 46 species belonging to 21 families were recorded within the study area. The dominant families were Labiatae, Gramineae and Compositae while therophytes and chamaephytes were the most frequent life forms. The samples were classified into six community types using TWINSPAN, which were also corroborated by CCA analysis. The principal gradients for vegetation distribution, identified by CCA, were associated with water storage and water retention ability, as expressed by pool perimeter and water depth. Generalised Additive Models (GAMs) were employed to identify responses of four dominant rock pool species to water depth. The resulting species response curves showed niche differentiation in the cases of Callitriche pulchra and Tillaea vaillantii and revealed competition between Zannichellia pedunculata and Chara vulgaris. The use of classification in combination with ordination techniques resulted in a good discrimination between plant communities. Generalised Additive Models are a powerful tool in investigating species response curves to environmental gradients. The methodology adopted can be employed for improving baseline information on plant community ecology and distribution in Mediterranean ephemeral pools.

Incorporation of in situ and biomarker assays in higher-tier assessment of the aquatic toxicity of insecticides

This study was designed to test the feasibility of integrating in situ, single species exposures and biomarker analysis into microcosm studies. Experimental ponds were dosed with pirimiphos methyl (PM) and lindane. C. riparius fourth instar larvae were deployed for 48 h on nine separate occasions during the study period before and after treatment. Surviving larvae were analysed for acetylcholinesterase activity (AChE). Survival and biomarker data were compared to chironomid assemblage analysis by monitoring insects emerging from the microcosms. Survival of chironomids within the in situ systems commenced on day + 16 after treatment with 31.6% and 53.3% survival in the lindane and PM treated ponds, respectively. In contrast, the first emergence from the microcosms occurred on days + 27, in respect to lindane, and + 59 for the PM treated ponds. Thus the in situ bioassay was able to demonstrate gradual reduction in toxicity within the sediment before this was evident from macroinvertebrate monitoring. Significant ACNE inhibition was only detected on exposure to PM. Levels decreased from 75% on day + 16 to 26% by day +29. The biomarker analysis confirmed that, by the end of the study, the insecticide was no longer exerting an effect. We discuss how the use of in situ bioassays could also aid comparison of microcosm studies by adding a standardized dimension. (C) 2003 Elsevier Ltd. All rights reserved.

PIXE analysis of chromium phytoaccumulation by the aquatic macrophytes Eicchornia crassipes

The uptake of hexavalent chromium in free living floating aquatic macrophytes Eicchornia crassipes cultivated in non-toxic chromium-doped hydroponic solutions is presented. A Cr-uptake bioaccumulation experiment was carried out using healthy macrophytes grown in a temperature controlled greenhouse. Six samples of nutrient media and plants were collected during the 23 day experiment. Roots and leaves were acid digested with the addition of an internal Gallium standard, for thin film sample preparation and quantitative Cr analysis by PIXE method. The Cr(6+) mass uptake by the macrophytes reached up to 70% of the initial concentration, comparable to former results and literature data. The Cr-uptake data were described using a non-structural first order kinetic model. Due to low cost and high removal efficiency, living aquatic macrophytes E. crassipes are a viable biosorbent in an artificial wetland of a water effluent treatment plant. (c) 2009 Elsevier B.V. All rights reserved.

Chromium ions phytoaccumulation by three floating aquatic macrophytes from a nutrient medium

In the present work, the trivalent and hexavalent chromium phytoaccumulation by three living free floating aquatic macrophytes Salvinia auriculata, Pistia stratiotes, and Eicchornia crassipes was investigated in greenhouse. These plants were grown in hydroponic solutions supplied with non-toxic Cr3+ and Cr6+ chromium concentrations, performing six collections of nutrient media and plants in time from a batch system. The total chromium concentrations into Cr-doped hydroponic media and dry roots and aerial parts were assayed, by using the Synchrotron radiation X-ray fluorescence technique. The aquatic plant-based chromium removal data were described by using a nonstructural kinetic model, obtaining different bioaccumulation rate, ranging from 0.015 to 0.837 1 mg(-1) d(-1). The Cr3+ removal efficiency was about 90%, 50%, and 90% for the E. crassipes, P. stratiotes, and S. auriculata, respectively; while it was rather different for Cr6+ one, with values about 50%, 70%, and 90% for the E. crassipes, P. stratiotes, and S. auriculata.

Evidence of a Ca(2+)-(center dot)NO-cGMP signaling pathway controlling zoospore biogenesis in the aquatic fungus Blastocladiella emersonii

The sporulation stage of the aquatic fungus Blastocladiella emersonii culminates with the formation and release to the medium of a number of zoospores, which are motile cells responsible for the dispersal of the fungus. The presence in the sporulation solution of 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), a potent and selective inhibitor of nitric oxide-sensitive guanylyl cyclases, completely prevented biogenesis of the zoospores. In addition, this compound was able to significantly reduce cGMP levels, which increase drastically during late sporulation, suggesting the existence of a nitric oxide-dependent mechanism for cGMP synthesis. Furthermore, increased levels of nitric oxide-derived products were detected during sporulation by fluorescence assays using DAF-2 DA, whose signal was drastically reduced in the presence of the nitric oxide synthase inhibitor N omega-Nitro-L-arginine methyl ester (L-NAME). These results were confirmed by quantitative chemiluminescent determination of the intracellular levels of nitric oxide-derived products. A putative nitric oxide synthase (NOS) activity was detected throughout sporulation, and this enzyme activity decreased significantly when L-NAME and 1-[2-(Trifluoromethyl)phenyl]imidazole (TRIM) were added to the assays. NOS assays carried out in the presence of EGTA showed decreased enzyme activity, suggesting the involvement of calcium ions in enzyme activation. Additionally, expressed sequence tags (ESTs) encoding putative guanylyl cyclases and a cGMP-phosphodiesterase were found in B. emersonii EST database (http://blasto.iq.usp.br), and the mRNA levels of the corresponding genes were observed to increase during sporulation. Altogether, data presented here revealed the presence and expression of guanylyl cyclase and cGMP phosphodiesterase genes in B. emersonii and provided evidence of a Ca(2+)-(center dot)NO-cGMP signaling pathway playing a role in zoospore biogenesis. (C) 2009 Elsevier Inc. All rights reserved.