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Water quality indices are employed by governments largely as a means of communicating the multifaceted nature of water quality and aquatic ecosystem health to the general public. Given the complexi...

Nitrogen is one of the critical nutrients regulating terrestrial and aquatic productivity, and is linked to degradation of water quality of freshwater and marine ecosystems worldwide. The landscape patterns of stream nitrogen components, concentrations and loadings and their relationships with climate variability and landuse, were analyzed and quantified in this study. We used stream nitrogen concentration data collected at 2,125 sites and climate data at 301 weather stations during 1976 to 2005 in 30 eco-regions across British Columbia, Canada. While the patterns of stream nitrogen component, concentration, and loading distributions were found to be related to landscape patterns of climate variability, human activities, landuse, natural vegetation, and relief across British Columbia, the climate variability on both temporal a d spatial scales were found to be the dominant driver of variability in loading and concentrations of nitrogen. Elevated air temperature gradient across the landscape of British Columbia resulted in a significant increase in stream nitrogen loading from terrestrial into aquatic ecosystems. Precipitation, nitrogen deposition, population density and urban area also significantly affected the stream nitrogen components, concentrations and loadings. We suggest that climate change, especially shifts in temperature and precipitation, along with increased human activities tend to have important implications for loading of nitrogen from terrestrial to aquatic ecosystems and associated water quality in aquatic ecosystems

We aimed to investigate mercury level in three species of fish such as Sander lucioperca, Liza aurata, and Rutilus frisii kutum. Sampling was done in the southern coasts of the Caspian Sea. The ranges of mercury level in S. lucioperca, L. aurata, and R. frisii kutum were 104.67-675.33 ppb, 60.66-175.33 ppb, and 123.33-170.33 ppb, respectively. Results revealed that the mercury level in S. lucioperca was more than the allowable limit at several sites, while it was less than the allowable limit in R. frisii kutum and L. aurata at all sampling sites. Further, the target hazard quotient (THQ) index for S. lucioperca was1 at some sites and1 for other species at all sites. The maximum allowable consumption for each species at the study area was measured daily and monthly.

Harmful algal blooms (HAB) release microtoxins that contaminate drinking water supplies and risk the health of millions annually. Crystalline ferrate(VI) is a powerful oxidant capable of removing algal microtoxins. We investigate in-situ electrochemically produced ferrate from common carbon steel as an on-demand alternative to crystalline ferrate for the removal of microcystin-LR (MC-LR) and compare the removal efficacy for both electrochemical (EC) and chemical dosing methodologies. We report that a very low dose of EC-ferrate in deionized water (0.5 mg FeO42− L−1) oxidizes MC-LR (MC-LR0 = 10 μg L−1) to below the guideline limit (1.0 μg L−1) within 10 minutes' contact time. With bicarbonate or natural organic matter (NOM), doses of 2.0–5.0 mg FeO42− L−1 are required, with lower efficacy of EC-ferrate than crystalline ferrate due to loss of EC-ferrate by water oxidation. To evaluate the EC-ferrate process to concurrently oxidize micropollutants, coagulate NOM, and disinfect drinking water, we spiked NOM-containing real water with MC-LR and Escherichia coli, finding that EC-ferrate is effective at 10.0 mg FeO42− L−1 under normal operation or 2.0 mg FeO42− L−1 if the test water has initial pH optimized. We suggest in-situ EC-ferrate may be appropriate for sporadic HAB events in small water systems as a primary or back-up technology.

Microbial adhesion to surfaces and the consequent biofilm formation under various environmental conditions is a common ecological phenomenon. Although biofilms play crucial beneficial roles in many processes, they can also cause serious problems for food, biomedical, environmental, and industrial sectors, leading to higher costs of production and equipment maintenance, and negative public health and environmental impacts. Biofilms are difficult to eradicate due to their resistance to conventional antimicrobial applications. Consequently, attention has been devoted to new emerging nanomaterials for their remarkable antimicrobial function. Understanding the inactivation mechanisms is the key to increase the efficiency of nanoparticles (NPs) and enhance the feasibility of their application against various microorganisms under different environments. In this paper, we review the activities of NPs as antimicrobial agents. We also discuss the mechanisms and factors contributing to antimicrobial properties of NPs. In addition, we describe some of the approaches employing NPs as effective antimicrobial agent, and associated challenges and problems in developing NPs as effective antibiofilm agents.

The unwavering spread of COVID-19 has taken the world by storm. Preventive measures like social distancing and mask usage have been taken all around the globe but still, as of September 2020, the number of cases continues to rise in many countries. Evidently, these measures are insufficient. Although decreases in population density and surges in the public's usage of personal protective equipment can mitigate direct transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), indirect transmission of the virus is still probable. By summarizing the current state of knowledge on the stability of coronaviruses on dry materials, this review uncovers the high potential for SARS-CoV-2 transmission through contaminated surfaces (i.e., fomites) and prompts future research. Fully contextualized data on coronavirus persistence are presented. The methods and limitations to testing the stability of coronaviruses are explored, and the SARS-CoV-2 representativeness of different coronaviruses is analyzed. The factors which dictate the persistence of coronaviruses on surfaces (media, environmental conditions, and material-type) are investigated, and the review is concluded by encouraging material innovation to combat the current pandemic. To summarize, SARS-CoV-2 remains viable on the timescale of days on hard surfaces under ambient indoor conditions. Similarly, the virus is stable on human skin, signifying the necessity of hand hygiene amidst the current pandemic. There is an inverse relationship between SARS-CoV-2 surface persistence and temperature/humidity, and the virus is well suited to air-conditioned environments (room temperature, ~ 40% relative humidity). Sunlight may rapidly inactivate the virus, suggesting that indirect transmission predominantly occurs indoors. The development of antiviral materials and surface coatings would be an extremely effective method to mitigate the spread of COVID-19. To obtain applicable data on the persistence of coronaviruses and the efficiency of virucidal materials, future researchers should understand the common experimental limitations outlined in this review and plan their studies accordingly.

The aim of the present study was to investigate the excisional wound healing activity of a biosurfactant isolated from Bacillus stratosphericus sp. A15 using Catla catla fish fat as economic substrate. The organism was screened on the basis of blood haemolytic activity, cell surface hydrophobicity, oil displacement test and its promising capacity of reducing surface tension (ST). The biosurfactant was identified as surfactin lipopeptide using IR, 1H NMR and mass spectrometric analysis. Mass spectrometric data indicated the presence of amino acid sequence as Val/Asp/Val/Leu/Leu/GluOMe linked with β-hydroxy fatty acid moiety containing 14 carbons in normal, iso or anteiso forms. An ointment of the test biosurfactant enhanced the wound closure (97%) in 10 days compared to the untreated control group (72%) (P < 0.05). Histopathological study confirmed the healing effect of the test biosurfactant in terms of well developed keratinocyte, presence of hair follicles, vacuoles, higher number of intact cells in dermis layer and a thick epidermal layer. The biosurfactant also showed anti-oxidant and antibacterial activity against Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 8739 which established its' additional advantage in wound protection.

Catechol, nitrite, and dissolved metals are ubiquitous in source drinking water. Catechol and nitrite have been identified as precursors for halonitromethanes (HNMs), but the effect of metal ions on HNM formation during chlorination remains unclear. The main objective of this study was to investigate the effect of metal ions (Fe³⁺, Ti⁴⁺, Al³⁺) on the formation of trichloronitromethane (TCNM) (the most representative HNM species in disinfected water) on chlorinating catechol and nitrite. Trichloronitromethane was extracted by methyl tert-butyl ether and detected by gas chromatography. The results show that metal ions promoted the formation of TCNM and that the enhancement efficiency followed the order of Fe³⁺ > Ti⁴⁺ > Al³⁺. Trichloronitromethane formation increased greatly within 2 h, and a basic condition (pH 8–9) favored TCNM formation more than acidic or neutral conditions. The conjoint effect of the metal–ion mixtures was shown to be similar to that of the single metal ion having the highest promoting effect on TCNM formation. Our results strongly suggest that metal ions play a significant role in enhancing TCNM formation.

Winter is thought to be a critical period for many fish in the ocean, but their ecology during this time tends to be poorly understood. We quantified the feeding ecology of juvenile Chinook salmon (Oncorhynchus tshawytscha) off the west coast of Vancouver Island in British Columbia, Canada, in autumn and winter to determine how seasonality could affect diet. Using stomach contents and stable isotopes, we tested the hypothesis that the winter diet of juvenile Chinook salmon differs from that of the autumn diet. Stomach-content data showed a shift from a primary reliance on amphipods in autumn to euphausiids in winter. This finding was generally corroborated by the stable isotope analysis, although mixing models suggested a greater contribution of fish prey to the diet in both autumn and winter. Understanding the diet of fish during winter may provide useful information for management as a first step in understanding the factors influencing mortality across life stages.

Recruitment variability in many fish populations is postulated to be influenced by climatic and oceanographic variability. However, a mechanistic understanding of the influence of specific variables on recruitment is generally lacking. Feeding ecology is one possible mechanism that more directly links ocean conditions and recruitment. We test this mechanism using juvenile Chinook Salmon (Oncorhynchus tshawytscha) collected off the west coast of Vancouver Island, British Columbia, Canada, in 2000–2009. Stable isotopes of carbon (δ13C), an indicator of temperature or primary productivity, and nitrogen (δ15N), an indicator of trophic position, were taken from muscle tissues of genetically stock-identified salmon. We also collated large-scale climate indices (e.g., Pacific Decadal Oscillation, North Pacific Gyre Oscillation), local climate variables (e.g., sea surface temperature) and copepod community composition across these years. We used a Bayesian network to determine how ocean conditions influenced feeding ecology, and subsequent survival rates. We found that smolt survival of Chinook Salmon is predicted by their δ13C value, but not their δ15N. In turn, large-scale climate variability determined the δ13C values of salmon, thus linking climate to survival through feeding ecology, likely through qualities propagated from the base of the food chain.

Ciguatera food poisoning (CFP) is widespread in tropical and sub-tropical waters, and it is the most common food poisoning caused by marine biotoxins. The toxins involved, ciguatoxins, are produced by certain dinoflagellates of the genus Gambierdiscus, and undergo biotransfer and biomagnification up the food web to planktivorous and ultimately, top predator fishes. In this paper, we reviewed the factors and processes that regulate the production of ciguatoxins, the ecological distribution and the pathways of their biotransfer, and fish consumption guidelines to prevent ciguatera-related food poisoning. Warm waters are commonly suggested as the most important factor that enhances toxic algal blooms and ciguatoxin production. Ecological distribution of ciguatoxic fish shows great regional specificity. In most endemic areas, carnivores such as groupers and other large fish have higher toxicity than their herbivorous and smaller counterparts, supporting the food chain hypothesis proposed by J.E. Randall (J.E. Randall, Bull. Mar. Sci. 8(3): 236–267, 1958); while in other areas, for example, French Polynesia, the opposite situations also exist, questioning the biomagnification hypothesis. Some countries and regions have taken measurements to prevent ciguatera poisoning through consumption guidelines. In this review, we look at some of the measures that could be used to prevent poisoning, while encouraging people to consume fish. For example, choosing smaller and lower trophic level fish are likely to be safer to consume. We suggest an approach to maintain better databases on ciguatera cases to instruct people on fish consumption safety, and develop a general guideline for fish consumption to reduce CFP.

In the present research, we aimed to investigate organochlorine toxins accumulated in both Rutilus frisii kutum and Liza aurata captured at the southern Caspian Sea. At six sampling stations, organochlorine toxins were measured in fish tissues by the gas chromatography–electron capture detector (GC-ECD) method. Total organochlorine toxins ranged from 2.102 ppb to 9.033 ppb in L. aurata at the study area. The highest content of total organochlorine toxins was obtained at station 5, whereas the lowest content was achieved at station 4. In L. aurata, lindane showed the highest level among the measured components (1.642 ppb), whereas α-lindane showed the highest mean level of the measured components (0.57 ppb). In this investigation, the total amount of organochlorine compounds in R. frisii kutum was more than that in L. aurata, but these compounds indicated no significant difference between the two types of fishes (p > 0.05). Moreover, the measured components in both types of fishes were lesser than the allowable limit.

Small and shallow water bodies often exhibit high rates of biogeochemical activities, yet have not received much attention. Here we test the hypothesis that there is strong diurnal stratification of physicochemical characteristics in a hyper-eutrophic pond, which would lead to a heterogeneous distribution of gas production via biological processes along vertical profile of water column. Accordingly, we focused on quantifying the seasonal and diurnal dynamics of nutrients (NO3−, NH4+, total dissolved nitrogen TDN, PO43−, total dissolved phosphorus TDP), physicochemical environment factors (DO, pH, light intensity, Chlorophyll-a) and gas emission (N2, N2O, O2, CH4) in the vertical profile of an ultra-eutrophic pond located at the subtropical climate zone, China. The strong and persistent stratification of several parameters at the resolution of centimeters along vertical profile of water was observed in summer and autumn. Interestingly, the surface water and sediment–water interface produced much more gas than the middle layers of water column. The quantity and composition of gas collected from the surface water were greatly affected by O2 production, which followed the diurnal cycle of sunlight intensity. Other biological processes, e.g. nitrification and/or denitrification, may also have contributed to the heterogeneous gas production as high N2 and N2O fluxes were detected in the surface layer and sediment–water interface. CH4 production was mainly from the sediment–water interface, especially in summer when the bottom layer developed very low DO concentrations due to strong stratification. Our results demonstrate that besides the unexpectedly long and strong thermal and physicochemical stratification, the shallow eutrophic pond can undergo significant vertical heterogeneity of gas emission due to the strong diurnal stratification of these physicochemical parameters.

The purpose of this study was to develop the multiple regression models to evaluate the formation of trihalomethanes (THMs) and haloacetonitriles (HANs) during chlorination of source water with low specific ultraviolet absorbance (SUVA) in Yangtze River Delta, China. The results showed that the regression models of THMs exhibited good accuracy and precision, and 86-97 % of the calculated values fell within ±25 % of the measured values. While the HANs models showed relatively weak evaluation ability, as only 75-83 % of the calculated values were within ±25 % of the measured values. The organic matter [dissolved organic carbon (DOC) or UV absorbance at 254 nm] and bromide exerted the most important influence on the formation of HANs. While for THMs, besides the organic matter and bromide, reaction time was also a key factor. Comparing the models for total THMs (T-THMs) in this study with others revealed that the regression models from the low SUVA waters may have low DOC coefficients, but high bromide coefficients as compared with those from the high SUVA waters.

Pharmaceuticals and personal care products (PPCPs) are emerging chemicals of concern detected in surface waters globally. Recent reviews advocate that PPCP occurrence, fate, and exposure need to be better predicted and characterized. The use of pharmaceutical prescription rates to estimate PPCP concentrations in the environment has been suggested. Concentrations of 7 pharmaceuticals (acetylsalicylic acid, diclofenac, fenoprofen, gemfibrozil, ibuprofen, ketoprofen, and naproxen) were measured in municipal wastewater using gas chromatography/ion trap-tandem mass spectroscopy (GC/IT-MS/MS). Subregional pharmaceutical prescription data were investigated to determine whether they could predict measured effluent concentrations (MECs) in wastewaters. Predicted effluent concentrations (PECs) for 5 of the 7 pharmaceuticals were within 2-fold agreement of the MECs when the fraction of parent pharmaceutical excreted was not considered. When the fraction of parent pharmaceutical excreted was considered, the respective PECs decreased, and most were within an order of magnitude of the MECs. Regression relationships of monthly PECs versus MECs were statistically significant (p < 0.05) but weak (R(2) = 0.18-0.56) for all pharmaceuticals except ketoprofen. This suggests high variability in the data and may be the result of factors influencing MECs such as the analytical methods used, wastewater sampling frequency, and methodology. The PECs were based solely on prescription rates and did not account for inputs of pharmaceuticals that had a significant over-the-counter component or were from other sources (e.g., hospitals).

SummaryAims The aims of this study were to investigate the temporal variation in Escherichia coli density and its sources at the drinking water intake of Comox Lake for a period of 3 years (2011–2013). Methods and Results Density of E. coli was assessed by standard membrane filtration method. Source tracking of E. coli were done by using BOX-A1R-based rep-PCR DNA fingerprinting method. Over the years, the mean E. coli density ranged from nondetectable to 9·8 CFU 100 ml−1. The density of E. coli in each of the years did not show any significant difference (P > 0·05); however, a comparatively higher density was observed during the fall. Wildlife was (64·28%, 153/238) identified as the major contributing source of E. coli, followed by human (18·06%, 43/238) and unknown sources (17·64%, 42/238). Although the sources were varied by year and season, over all, the predominant contributing sources were black bear, human, unknown, elk, horse and gull. Conclusions The findings of this investigation identified the multiple animal sources contributing faecal bacteria into the drinking water intake of Comox Lake and their varying temporal occurrence. Significance and Impact of the Study The results of this study can reliably inform the authorities about the most vulnerable period (season) of faecal bacterial loading and their potential sources in the lake for improving risk assessment and pollution mitigation.

Trophic interactions within and among species vary widely across spatial scales and species’ ontogeny. However, the drivers and implications of this variability are not well understood. Juvenile Chinook salmon Oncorhynchus tshawytscha have a wide distribution, ranging from northern California to the eastern Bering Sea in North America, but it is largely unknown how their feeding ecology varies and changes with ontogeny across this range. We collected juvenile Chinook salmon and zooplankton using standardized protocols along the coastal Northeast Pacific Ocean. Using a combination of stomach contents and stable isotopes of nitrogen (δ15N) and carbon (δ13C) to characterize feeding ecology, we found regional differences in prey utilization by juvenile Chinook salmon. With growth and ontogeny, juvenile salmon in all regions became equilibrated with oceanic isotopic values. There were regional differences in the δ13C values of juvenile Chinook salmon that may correspond to regional differences in sea surface temperature. There were also regional differences in stable isotope-derived trophic level, and these estimates differed from those derived from stomach contents, possibly due to the different periods over which these metrics integrate. Dietary niche width, as indicated by stable isotopes, corresponded to the expected dietary diversity from stomach contents, combined with the isotopic variability seen in baseline values. Our results indicate strong geographic and ontogenetic differences in feeding ecology of juvenile Chinook salmon. These differences are likely influenced by a combination of ocean-entry date, ocean-entry size, ontogeny, growth rates and regional conditions.

Many organisms experience fasting in their life time, and this physiological process has the potential to alter stable isotope values of organisms, and confound interpretation of food web studies. However, previous studies on the effects of fasting and starvation on stable isotopes show disparate results, and have never been quantitatively synthesized. We performed a laboratory experiment and meta-analysis to determine how stable isotopes of δ (15)N and δ (13)C change with fasting, and we tested whether moderators such as taxa and tissue explain residual variation. We collected literature data from a wide variety of taxa and tissues. We surveyed over 2000 papers, and of these, 26 met our selection criteria, resulting in 51 data points for δ (15)N, and 43 data points for δ (13)C. We determine that fasting causes an average increase in the isotopic value of organisms of 0.5‰ for δ (15)N and that the only significant moderator is tissue type. We find that the overall effect size for δ (13)C is not significant, but when the significant moderator of tissue is considered, significant increases in blood and whole organisms are seen with fasting. Our results show that across tissues and taxa, the nutritional status of an organism must be considered when interpreting stable isotope data, as fasting can cause large differences in stable isotope values that would be otherwise attributed to other factors.

The use of nitrogen stable isotopes to discriminate between conventionally and organically grown crops has been further developed in this study. Soil and irrigation water from different regions, as well as nitrogen fertilizers used, have been examined in detail to determine their effects on nitrogen isotope composition of spinach, lettuce, broccoli and tomatoes. Over 1000 samples of various types of organically and conventionally grown produce of known origin, along with the samples of nitrogen fertilizers used for their growth, have been analysed in order to assemble the datasets of crop/fertilizer correlations. The results demonstrate that the developed approach can be used as a valuable component in the verification of agricultural practices for more than 25 different types of commercially grown green produce, either organic or conventional. Over a period of two years, various organic and non-organic greens, from different stores in Seattle (WA, USA) and Victoria (BC, Canada), were collected and analysed using this methodology with the objective of determining any pattern of misrepresentation.

Rapid urbanization in China has dramatically deteriorated the water quality of streams and threatening aquatic ecosystem health. This study aims to 1) assess the impacts of urbanization on water quality and macroinvertebrate composition and 2) address the question of how urbanization affects macroinvertebrate distribution patterns. Environmental variables over multispatial scales and macroinvertebrate community data were collected on April (dry season) and September (wet season) of 2014 and 2015 at 19 sampling sites, of which nine had a high urbanization level (HUL), six had moderate urbanization level (MUL) and four had low urbanization level (LUL), in the Liangjiang New Area. The results of this study showed that macroinvertebrate assemblages significantly varied across the three urbanization levels. The sensitive species (e.g., EPT taxa) were mainly centralized at LUL sites, whereas tolerant species, such as Tubificidae (17.3%), Chironomidae (12.1%), and Physidae (4.61%), reached highest relative abundance at LUL sites. The values of family biotic index (FBI) and biological monitoring working party (BMWP) indicated the deterioration of water quality along urbanization gradient. Seasonal and inter - annual changes in macroinvertebrate communities were not observed. The results of variation partitioning analyses (CCAs) showed that habitat scale variables explained the major variation in macroinvertebrate community composition. Specifically, the increased nutrient concentrations favored tolerant species, whereas high water flow and substrate coarseness benefitted community taxa richness, diversity and EPT richness. Considering the interactions between scale-related processes, the results of this study suggested that urbanization resulted in less diverse and more tolerant stream macroinvertebrate assemblages mainly via increased nutrient concentrations and reduced substrate coarseness.

Occurrence of halonitromethanes (HNMs) in drinking water has been a concern recently due to the potentially high human health risks of HNMs. Mechanisms of formation of HNMs during disinfection has remained controversial. The objective of this study was to investigate the effects of nitrite on the formation of trichloronitromethane (TCNM), a dominant HNM species occurring in chlorinated water. Polyhydroxy-phenols (hydroquinone, catechol, resorcinol, and phloroglucinol) and sugars (glucose, maltose, and lactose) were compared as surrogates/model compounds of common organic precursors of humic and non-humic substances in natural organic matter, respectively. The results showed that TCNM was not detectable after chlorinated sugars with the addition of nitrite. Upon chlorinating the polyhydroxy-phenols, TCNM formation varied greatly among different compounds, i.e., resorcinol > phloroglucinol > catechol >> hydroquinone. The results demonstrated that TCNM formation in the presence of nitrite was a function of aromaticity as well as the position and number of hydroxyl groups on the benzene rings of a compound, and the TCNM formation potential of humic substances was greater than that of non-humic substances. For catechol, resorcinol, and phloroglucinol, TCNM formation varied greatly with pH but generally remained stable with the increase of reaction time and temperature.

Rapid urbanization in China has been causing dramatic deterioration in the water quality of rivers and threatening aquatic ecosystem health. In this paper, multivariate techniques, such as factor analysis (FA) and cluster analysis (CA), were applied to analyze the water quality datasets for 19 rivers in Liangjiang New Area (LJNA), China, collected in April (dry season) and September (wet season) of 2014 and 2015. In most sampling rivers, total phosphorus, total nitrogen, and fecal coliform exceeded the Class V guideline (GB3838-2002), which could thereby threaten the water quality in Yangtze and Jialing Rivers. FA clearly identified the five groups of water quality variables, which explain majority of the experimental data. Nutritious pollution, seasonal changes, and construction activities were three key factors influencing rivers' water quality in LJNA. CA grouped 19 sampling sites into two clusters, which located at sub-catchments with high- and low-level urbanization, respectively. One-way ANOVA showed the nutrients (total phosphorus, soluble reactive phosphorus, total nitrogen, ammonium nitrogen, and nitrite), fecal coliform, and conductivity in cluster 1 were significantly greater than in cluster 2. Thus, catchment urbanization degraded rivers' water quality in Liangjiang New Area. Identifying effective buffer zones at riparian scale to weaken the negative impacts of catchment urbanization was recommended.

In aquatic systems, the ratio of pre - dator mass to prey mass (PPMR) is an important constraint on food web structure, and has been correlated with environmental stability. One com- mon approach of estimating PPMR uses nitrogen stable isotopes (δ 15 N) as an indicator of trophic position, under the assumption that the discrimi - nation between diet and tissue is constant with increasing diet δ 15 N (an additive approach). How- ever, recent studies have shown that this assump- tion may not be valid and that there is a negative trend between the δ 15 N of the diet and the dis- crimination value (a scaled approach). Here, we estimated PPMR for a simulated food web using both the traditional additive approach and the improved scaled approach, and then tested our predictions with isotope samples from a North Sea food web. Our simulations show that the additive approach yields incorrect estimates of PPMR, and these biases are reflected in North Sea PPMR esti- mates. The extent of the bias is dependent on the baseline δ 15 N and trophic level sampled, with the greatest differences for samples with low baseline δ 15 N sampled at lower trophic levels. The scaled approach allows for the comparison of PPMR across varying δ 15 N baselines and trophic levels, and will refine estimates of PPMR.

Understanding how environmental “bottom-up” conditions affect the production or survival of higher trophic levels is an integral component of ecosystem management. However, linking environmental conditions to higher trophic levels is difficult because of differences in turnover time. Carbon (δ 13 C) and nitrogen (δ 15 N) isotopes in animal tissues can elucidate these links because they can potentially integrate variability in nutrient concentrations, primary production, and food web structure on a time-scale that reflects the tissue turnover time of consumers. Here we assess environmental and trophic correlates of zooplankton stable isotopes in the Strait of Georgia and three adjacent coastal regions. Zooplankton stable isotopes show strong seasonal variability, and are typically highest in the summer. Regional δ 15 N signatures appear to be synchronized with the timing of production maxima in each region, and broadly reflect variability in nitrate and chlorophyll. In contrast zooplankton δ 13 C have relatively weak regional signatures. The environmental variables that best explain zooplankton stable isotopes vary between regions, and between seasons. On the west coast of Vancouver Island, zooplankton δ 15 N is significantly correlated with sea surface temperature throughout the year. In the Strait correlations between zooplankton stable isotopes and environmental variables are season-specific. In the spring, δ 15 N and δ 13 C are correlated with chlorophyll, zooplankton biomass and nitrate, but in the summer zooplankton δ 15 N is only weakly correlated with the biomass of carnivorous zooplankton. In both regions, between-year variability in zooplankton stable isotopes appears to reflect between-year variability in oceanographic conditions. A time-series of stable isotopes collected from a copepod ( Neocalanus plumchrus ) from the Strait of Georgia suggests that chlorophyll, nitrate and zooplankton biomass varied dramatically between 2001 and 2006, and sheds light on environmental conditions that accompanied that collapse of this important prey species. We discuss the implications of our findings for an ecosystem management approach to conservation.

[1] Drinking water purveyors are increasingly relying on land conservation and management to ensure the safety of the water that they provide to consumers. To cost-effectively implement any such landscape initiatives, resources must be targeted to the appropriate spatial scale to address quality impairments of concern in a cost-effective manner. Using data gathered from 40 Canadian rivers across four ecozones, we examined the spatial scales at which land use was most closely associated with drinking source water quality metrics. Exploratory linear mixed-effects models accounting for climatic, hydrological, and physiographic variation among sites suggested that different spatial areas of land-use influence drinking source water quality depending on the parameter and season investigated. Escherichia coli spatial variability was only associated with land use at a local (5–10 km) spatial scale. Turbidity measures exhibited a complex association with land use, suggesting that the land-use areas of greatest influence can range from a 1 km subcatchment to the entire watershed depending on the season. Total organic carbon concentrations were only associated with land use characterized at the entire watershed scale. The Canadian Council of Ministers of the Environment Water Quality Index was used to calculate a composite measure of seasonal drinking source water quality but did not provide additional information beyond the analyses of individual parameters. These results suggest that entire watershed management is required to safeguard drinking water sources with more focused efforts at targeted spatial scales to reduce specific risk parameters.

The objective of the study was to evaluate the survival response of multi-drug resistant enteropathogenic Escherichia coli and Salmonella paratyphi to the salinity fluctuations induced by a saltwater barrier constructed in Vembanadu lake, which separates the lake into a freshwater dominated southern and brackish water dominated northern part. Therefore, microcosms containing freshwater, brackish water and microcosms with different saline concentrations (5, 10, 15, 20, 25 ppt) inoculated with E. coli/S. paratyphi were monitored up to 34 days at 20 and 30 °C. E. coli and S. paratyphi exhibited significantly higher (p < 0.05) survival at 20 °C compared to 30 °C in all microcosms. Despite fresh/brackish water, E. coli and S. paratyphi showed prolonged survival up to 34 days at both temperatures. They also demonstrated better survival potential at all tested saline concentrations except 25 ppt where a significantly higher (p < 0.0001) decay was observed. Therefore, enhanced survival exhibited by the multi-drug resistant enteropathogenic E. coli and S. paratyphi over a wide range of salinity levels suggest that they are able to remain viable for a very long time at higher densities in all seasons of the year in Vembanadu lake irrespective of saline concentrations, and may pose potential public health risks during recreational activities.

We present here the draft genome sequence of Pseudoalteromonas tetraodonis strain MQS005, a bacterium possessing potential quorum-sensing regulatory activity. This strain was isolated from water from the South China Sea, People's Republic of China. The assembly consists of 4,252,538 bp and contains 144 contigs, with a G+C content of 41.85%.

The reliability of using caffeine (1,3,7-trimethyl xanthine) as an anthropogenic marker of human mediated contaminants in the inland water system has been studied from the Lake Simcoe watershed in Central Ontario, Canada. Both water and sediment samples were collected on a biweekly interval from five sampling locations for a period of 8 months from May to December 2010. In addition, bacterial indicators of the water quality was monitored by enumerating the total coliform and fecal coliform ( Escherichia coli ) in the water and sediment samples from these sampling locations. The results showed the occurrence of caffeine in all samples collected throughout the study period indicating the presence of human domestic waste in these locations. The coliforms and caffeine in water were negatively correlated while a positive correlation was obtained between these parameters in sediment samples. The study showed a statistically significant variation in caffeine between the sampling locations over the study period with the maximum value recorded at Site 2, the most anthropogenically disturbed area. The seasonal variation of caffeine concentration showed higher values in summer months compared to others and this corresponded to the increased human activities in this area during this period. To conclude, monitoring of caffeine coupled with the bacterial indicators could help to track the origin of contaminants in the inland water systems.

The abundance and composition of zooplankton, fish and seabirds show dramatic interannual variability in temperate coastal regions. Understanding links between this variability and bottom-up processes is an important goal for biological oceanographers. Because zooplankton stable isotopes (d 15 N and d 13 C) are potentially influenced by variability in phytoplankton nutrient utilization, primary production, and zooplankton trophic structure, they have the potential to elucidate links between bottom-up processes, food web structure, and abundance or species composition of higher trophic levels. Here we measure correlations between zooplankton stable isotopes and oceanographic variables in two time series from the west coast of Vancouver Island, upstream of the California Current upwelling system. We then relate interannual variability in zooplankton stable isotopes to interannual variability in zooplankton species composition. Zooplankton stable isotopes show striking patterns of seasonal, regional and interannual variability. A strong positive correlation between annual averages of zooplankton d 15 N and sea-surface temperature is evident in both time series. Zooplankton d 15 N is also negatively correlated with interannual anomalies of subarctic copepod biomass in both time series. We propose two different mechanisms to explain these correlations: variability in the strength and direction of horizontal advection, or local fluctuations nutrient availability. We conclude that they are most likely caused by local, temperature-driven fluctuations in nitrate concentrations and primary production. We show that the positive correlation between zooplankton d 15 N and temperature is widespread, extending to regions outside of the California Current system. Our findings suggest that interannual variability in zooplankton composition is linked with bottom-up variability in nitrate availability and primary production in the upstream portion of the California Current system. Our results also highlight the potential of integrating biochemical parameters in zooplankton time series for elucidating links between bottom-up processes and the survival of higher trophic levels in the ocean.

Summary 1. The importance of species diversity for the stability of populations, communities and ecosystem functions is a central question in ecology. 2. Biodiversity experiments have shown that diversity can impact both the average and variability of stocks and rates at these levels of ecological organization in single trophic-level ecosystems. Whether these impacts hold in food webs and across trophic levels is still unclear. 3. We asked whether resource species diversity, community composition and consumer feeding selectivity in planktonic food webs impact the stability of resource or consumer populations, community biomass and ecosystem functions. We also tested the relative importance of resource diversity and community composition. 4. We found that resource diversity negatively affected resource population stability, but had no effect on consumer population stability, regardless of the consumer’s feeding selectivity. Resource diversity had positive effects on most ecosystem functions and their stability, including primary production, resource biomass and particulate carbon, nitrogen and phosphorus concentrations. 5. Community composition, however, generally explained more variance in population, community and ecosystem properties than species diversity per se. This result points to the importance of the outcomes of particular species interactions and individual species’ effect traits in determining food web properties and stability. 6. Among the stabilizing mechanisms tested, an increase in the average resource community biomass with increasing resource diversity had the greatest positive impact on stability. 7. Our results indicate that resource diversity and composition are generally important for the functioning and stability of whole food webs, but do not have straightforward impacts on consumer populations.

Manure and fertilizer applications can increase soil productivity and land economic values, but the controversial result can be a decline of water quality due to the increased nutrient exports from soils to the streams. The impacts of landuse, manure and fertilizer application on nutrient exports from soils to the streams were analyzed using the SWAT (Soil Water Assessment Tool) model for the Salmon River watershed in south-central British Columbia, Canada. The results showed that the animal farms had the highest rates of nutrient exports from soils to the streams and the natural forested lands had the lowest. It was estimated that the whole Salmon River watershed would export approximately 11.52 t·yr-1 of organic nitrogen (ON), 8.05 t·yr-1 of nitrate nitrogen (NO3-N), 2.30 t·yr-1 of organic phosphorus (OP) and 1.36 t·yr-1 of soluble reactive phosphorus (SRP) if the whole watershed was covered by natural vegetation without human disturbance. Current landuse changes, by converting natural vegetation lands to agriculture and animal farms and associated manure and fertilizer applications, have in-creased approximately 53.30 t·yr-1 of ON, 9.68 t·yr-1 of NO3-N, 22.69 t·y-1 of OP and 6.23 t·y-1 of SRP exports to the streams in the whole watershed. The SWAT model predicted that a daily 100 kg·ha-1 of fresh manure deposit from grazing cows during grazing season from later spring to later fall could increase 2.57 kg·ha-1·yr-1 of ON, 0.39 kg·ha-1·yr-1 of NO3-N, 2.35 kg·ha-1·yr-1 of OP and 0.48 kg·ha-1·yr-1 of SRP export to the streams. Fertilization could increase 1.57 kg ha-1 yr-1 of ON and 4.02 kg·ha-1·yr-1 of NO3-N export to the streams if 100 kg·ha-1·yr-1 of nitrogen (NH4NO3) fertilizer was applied in spring. Also fertilization could increase 1.18 kg·ha-1·yr-1 of OP and 0.20 kg·ha-1·yr-1 of SRP export to the streams if 100 kg·ha-1 phosphorus (P2O5) fertilizer was applied in spring.

The effect of species diversity on ecosystem function is commonly studied within a single trophic level, but less is known about how resource diversity affects species interactions between trophic levels. We conducted a grazing experiment to determine how resource species diversity affects rates of consumption by three species of freshwater zooplankton consumers. We measured the effect of resource diversity on rates of consumption for several resource community compositions. These compositions varied in terms of palatability for the consumers. The effect of resource diversity on consumption rates depended on the diet breadth of the consumer species (from specialist to generalist) and the community composition of resources. Overall, high resource diversity commonly caused a decline in consumption rates of consumers. The most selective grazer showed reduced consumption for nearly all community compositions, whereas the most generalist grazer showed accelerated consumption when all resource species were palatable. Our results demonstrate that resource species diversity can modulate rates of consumption through the action of multiple different mechanisms.

Ideas on how various measures of nutrient limitation relate to plankton biomass and species composition are re-examined. While long-term and multi-lake studies typically focus on determining overall biomass, seasonal studies are more focused toward understanding species composition. We use physiological assays to assess short-term nutrient deficiency of nitrogen and phosphorus in two moderately fertile lakes. While biomass in the lakes was considered to ultimately be limited by total phosphorus, nutrient assays were variable in time. Nutrient ratios (TN:TP, PN:PP, PC:PP and PC:PN) did not predict short-term deficiencies, notably that nitrogen deficiency occurred in these phosphorus-limited lakes. In one of our study lakes, there was a relaxation of phosphorus deficiency despite phosphate concentrations occurring below traditional detection limits. Following this period, there was an autumn bloom of Aphanizomenon flos-aquae. This relationship corresponds with other studies that have found A. flos-aquae to be a poor competitor for phosphorus. In contrast, phosphorus deficiency remained high prior to the autumn diatom bloom in our other study lake. Deficiency measures remain an excellent means of assessing physiological status of plankton communities and provide greater insight into species compositional changes, especially when other potential indicators like dissolved nutrient concentrations are inconclusive. Regardless of the nutrient limitation indicator used for a given study, it is critical to consider the appropriate scale of the measure.

A bacterial water quality model (BWQM) was developed and used to evaluate the impacts of cattle farming and climate change on the stream fecal coliform pollution in the Salmon River watershed in south-central British Columbia, Canada. The accuracy of the model simulation was evaluated using the Nash-Sutcliffe coefficient of efficiency (COE). The BWQM simulated the observed field data well, with the values of the COE ranging from 0.76 to 0.78 for the stream flow, from 0.55 to 0.60 for the fecal coliform (FC) concentration, and from 0.85 to 0.89 for the FC loading. The BWQM captured more than 79%, 66%, and 90% variation of the daily stream flow, FC concentration, and FC loading, respectively. The BWQM predicts that between 70% and 80% of the FC were transferred from the cattle farm to the Salmon River through the snowmelt-caused surface runoff during late winter and early spring, with the balance 20% to 30% coming from the soil-lateral flow and the groundwater return flow. The model also indicates that the stream FC concentration is sensitive to the distance of the cattle farm to the Salmon River. The model scenario analysis reveals that the climate change, at an assumed 1°C increment of daily air temperature, results in an increase in the stream FC concentration in the spring, fall, and winter, but there is also a decrease in the summer. The increased air temperature also changes the seasonal pattern of the stream FC concentration. Rainfall can reduce the stream FC concentration and mitigate the impact of the increased air temperature on the stream FC concentration as long as it does not result in a surface runoff or flooding event.

Divergence in habitat use among closely related species is a common characteristic of adaptive radiations. Large differences in the size structure of prey between habitats could strengthen disruptive selection on generalist predators and lead to a divergence in trophic position among species in an adaptive radiation. Using threespine stickleback (Gasterosteus aculeatus) in freshwater lakes as a model system, we examined whether divergence in habitat use coincides with shifts in trophic position. We examined the habitat use and trophic position of individual sticklebacks from divergent lake environments that have only one stickleback species (allopatric lakes) and from lakes that have a pair of benthic and limnetic stickleback species (sympatric lakes). In two sympatric lakes, the limnetic species had a higher trophic position than the benthic species, and in both allopatric and sympatric lakes, sticklebacks specializing on pelagic prey had a higher trophic position for a given size than sticklebacks specializing on benthic prey. Furthermore, the trophic position of pelagic specialists was correlated with individual variation in their gill raker length. Our results indicate that gill raker length is an important trait that underlies differentiation in both habitat use and trophic position among stickleback species, populations, and individuals.

Characterizing trophic flows is central to our understanding of energy transfer in marine ecosystems. The food webs of coastal systems are difficult to study because the proportion of autochthonous to allochthonous sources often varies seasonally and is often overlaid on a seasonal cycle of zooplankton composition. Here, we use a combination of fatty acids and stable isotopes to disentangle the trophic pathways in a productive coastal system (the Strait of Georgia (SoG), Canada). Over the span of a year, Metridia pacifica, a ubiquitous omnivorous copepod, can utilize a wide range of dietary items including diatoms, flagellates, bacteria, detritus, and microzooplankton. M. pacifica can switch from herbivory to carnivory in response to declining chlorophyll concentrations after the spring bloom and can occasionally utilize detrital sources. These findings are discussed in the context of previous knowledge of the SoG ecosystem, the current state of ecosystem modeling in the region, and the use of stable isotopes and fatty acids to assess trophic dynamics.

The competitive exclusion principle poses the pressing question of how biodiversity is maintained in nature. Many mechanisms have been proposed to explain diversity and to resolve what has become known as the “paradox of the plankton”. We propose a dichotomy among these mechanisms in order to enable empiricists to begin testing their relative importance. Specifically, the mechanisms can be categorized as being internally generated or as depending on forces external to the competitive community. Here we tested whether the internal competitive dynamics of a phytoplankton assemblage or externally generated resource variability (a disturbance) were more effective at maintaining species diversity over time. We also tested whether the species composition of assemblages was important in determining the persistence of species diversity. We employed controlled microcosm experiments in which we either imposed exogenous variability in nutrient availability via serial dilution or allowed the communities to ...

[ILLUSTRATION OMITTED] Scientific talent is desperately needed to address the challenges we will face globally in the years and decades to come. Yet there is evidence from around the world that high achieving science undergraduates are becoming increasingly rare (Bohannon, 2007; Clery, 2007; Wood, 2008), though the situation for biology may, be less dire than for other sciences. Little is currently known about what might attract students into university biology programs and, from there, into specific careers. How do we increase the application rates of high school students in college and university biology (life-science) programs? In particular, how can we increase the numbers of women and aboriginals who choose scientific careers in our discipline? These are but two of the focal questions for a large interdisciplinary team that brings together natural scientists, cognitive scientists, educational and (career) counseling psychologists, and (science, mathematics, technology, literacy) educators as part of one of five centers funded by the Natural Sciences and Engineering Council of Canada. One way in which the Pacific Center for Scientific Literacy approaches answering the focal question is by providing high school students with opportunities to experience firsthand "authentic science practice," a form of realizing that "the future of school science lies outdoors" (Slingsby, 2006). Authentic practice goes beyond simple visits, as in the British Salter's Nuffield Advanced Biology visits (e.g., Dunkerton, 2007), because students spend an extended period of time with scientists participating in the ongoing research. Although authentic science projects in schools take biology students considerably beyond what they normally do and learn (e.g., Roth & Bowen, 1995), participating in real everyday activity such as scientific research or environmental activism changes the psychology of learning all together (van Eijck & Roth, 2007). * Authentic Science & Laboratory Internship As its cognates "cognitive apprenticeship" and "community of practice," authentic science practice has been advocated as a means of assisting students in developing (a) usable and transferable scientific skills and knowledge (b) understanding of the sciences as epistemic (knowledge-generating) disciplines (Roth, 1995), and easing the fear of entering into science programs. Some universities adopt this approach for introducing their first- and second-year students to teach them the fundamental skills of science and the process of scientific discovery (e.g., The Center for Authentic Science Practice in Education [http://www.purdue.edu/dp/caspie/]). Our Center has been designed, in part, to provide and study high school student learning (cognitive, psycho-social, emotional, career-related) when students are provided with opportunities for internship experiences in university-based biology laboratories. The notion of authentic practice was created after research had shown that much of what people do in their everyday lives and on the job is unaffected by the mathematics and science they learned in school (Lave, 1988; Scribner, 1984; Traweek, 1988). A recent study suggests that the number of high school courses students take in a subject correlates with their university grade point average in the same field, but not with their grade point average in other sciences (Sadler & Tai, 2007). In the wake of cognitive scientific and cognitive anthropological findings, science and mathematics educators began to understand knowledge and skills in terms of practices--the patterned actions scientists and mathematicians deploy in their working lives--rather than as procedural and declarative information stored in their heads (van Eijck & Roth, 2007). Thus, it was proposed that students of mathematics and science engage in activities that bear considerable family resemblance with the activities in which scientists, mathematicians, or historians normally are engaged. …

Many science educators encourage student experiences of “authentic” science by means of student participation in science-related workplaces. Little research has been done, however, to investigate how “teaching” naturally occurs in such settings, where scientists or technicians normally do not have pedagogical training and generally do not have time (or value) receiving such training. This study examines how laboratory members without a pedagogical background or experience in teaching engage high school students during their internship activities. Drawing on conversation analysis, we analyze the minute-by-minute transactions that occurred while high school students participated in a leading environmental science laboratory. We find that the participation trajectory was based on demonstration-practice-connect (D-P-C) phases that continually recurred in the process of “doing” science. Concerning the transactional structures, we identify two basic conversation patterns—Initiate-Clarify-Reply (I-C-R) and Initiate-Reply-Clarify-Reply (I-R-C-R)—that do not only differ from the well-known Initiate-Reply-Evaluate (I-R-E) patterns previously observed in science classrooms, but also could be combined to constitute more complex patterns. With respect to the organization of natural pedagogical conversations, we find that there were not only of preferred and dispreferred modes of responding but also ambiguous dispreferred modes; and the formulating organization not only includes self-formulating but also other-formulating. These natural pedagogical conversations helped, on the one hand, students to clarify their understanding and, on the other hand, technicians (or teachers) to teach toward different needs for different students in different contexts. © 2009 Wiley Periodicals, Inc. J Res Sci Teach 46: 481–505, 2009

Although food quality is thought to play an important role in the survival of marine organisms, the extent of natural variability in food quality over long time scales remains poorly char- acterized. We present a 6 yr time series of fatty acid data from the calanoid copepod Neocalanus plumchrus, an important contributor to mesozooplankton biomass in the Strait of Georgia and the northeast Pacific Ocean. Fatty acid profiles indicate significant spatiotemporal differences in the diet of this copepod. Spatially, oceanic specimens display fatty acid signatures characteristic of omnivo- rous copepods while coastal animals display primarily herbivorous, diatom-based signatures. Tempo- rally, the fatty acid profiles of coastal N. plumchrus shifted from an omnivorous oceanic diet to an her- bivorous, diatom-based diet between 2001 and 2006. The ratio of diatom to flagellate fatty acid markers increased over time, peaking from 2005 to 2006. The composition of flagellate markers also changed from primarily dinoflagellate markers (rich in docosohexaeonic acid) to green algal markers (poor in this essential fatty acid). The diet of N. plumchrus as deduced from fatty acids correlates with phytoplankton community composition. The abundance of coastal N. plumchrus in the Strait of Geor- gia was strongly correlated with the ratio of docosahexaeonic acid to eicosapentaeonic acid in the lipids of these copepods. We also discuss the potential for an imbalance of essential fatty acids sup- plied by a diatom-rich diet to limit the growth and survival of N. plumchrus in the Strait of Georgia.

International audience; Plankton particle size is a central issue for aquatic ecologists. In this field study, we examined essential fatty acids (EFAs) in different plankton particle sizes and obtained initial estimates of how EFA concentrations, and thus high dietary lipid quality for consumers, vary with seston size. We measured EFA concentrations in three seston size classes (i.e. micro = 0.7–35 μm; meso = 35–64 μm and macroseston = 64–100 μm) and in cladocerans and calanoid copepods of monomictic, coastal lakes. Algal pigment analysis identified a mixture of Chlorophyta, Cryptophyta, diatoms and Cyanophyta in all seston size classes. Total EFA concentrations did not vary with increasing seston size. There was no difference in linoleic (LIN), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid concentrations among the three seston size classes; however, α-linolenic (ALA) and arachidonic (ARA) acid concentrations were significantly higher in microseston. For herbivorous zooplankton, concentrations of LIN, ALA and EPA did not differ significantly between cladocerans and calanoid copepods; however, ARA concentrations were significantly higher in cladocerans and DHA concentrations were significantly higher in calanoid copepods. Our results indicate that microseston represents the most nutritious dietary component, per unit biomass, with respect to ALA and ARA and that seston size alone does not predict EFA concentrations, i.e. dietary access to larger seston particle sizes is not necessarily associated with access to particles with higher EFA concentrations.

The spring zooplankton community in the Strait of Georgia (British Columbia, Canada) is characterized by the presence of several calanoid copepod species which collectively make up ~90% of the mezozooplankton biomass. Here, we investigate interspecific, interannual, and geographic variability in the diets and trophic positions of these copepods using a combination of fatty acids and stable isotopes. To characterize geographic variability in diet, we compare our findings from the Strait of Georgia with similar data from Ocean Station P in the subarctic northeast Pacific. Both fatty acid and stable isotope signatures indicate the existence of three trophic levels, even within the limited size range of these copepods: Neocalanus plumchrus and Calanus marshallae are primarily omnivorous, while Euchaeta elongata is carnivorous and Eucalanus bungii is herbivorous. Fatty acid markers of trophic position (e.g., DHA/EPA, 18:1n-9/18:1n-7) correlate significantly with δ15N, while markers indicating the proportion of diatoms to flagellates in the diet (e.g., 16PUFA/18PUFA and DHA/EPA) correlate significantly with δ13C, after the effect of lipid concentration on δ13C is accounted for. Despite the general correlation between stable isotopes and fatty acids, the former are not sensitive enough to capture the range of interannual variability observed in the latter, and can only capture substantial shifts in the diet over geographic scales. However, regardless of variability in food quality, the relative trophic positions of these copepods do not change significantly either spatially or temporally.

Concentrations of Fe, Mn, Cu, dissolved organic matter (DOM), and pH were synthesized from 30 publications to determine the factors regulating concentrations and behavior of metals in freshwater systems. Results from the review suggest that contrasting watershed land use can directly (erosion and runoff) and indirectly (in-lake processes including metal-DOM-pH interactions) affect the metal concentrations in freshwater systems. Among the watershed land uses considered here, concentrations of Fe, Mn, and Cu were observed in the following order: arctic lakesforestedagriculturalurbanizedmined. A drastic difference in mean metal concentrations has been observed when undisturbed or low impact watersheds (arctic and forested) were changed by agricultural, urban, and mining developments. Relationships between metal concentrations and pH revealed that metals precipitate at high pH (pH5). Additionally, at pH5, metal concentrations were significantly correlated with DOM due to metal-DOM complexation. High ratios of metal: DOM occur only at low DOM concentrations. Collectively, two general conclusions can be drawn from this review. First, lakes, rivers, and streams with urbanized watersheds are the most susceptible to increased concentrations of metals. Secondly, these results also suggest that regardless of high or low DOM in the water column, pH would affect metal concentrations in freshwater systems. Nonetheless, free metal ions would be higher in freshwater systems with acidic water and low DOM.

The major objective of the present study was to investigate the contribution of major biomolecules, including protein, carbohydrates and lipids, in predicting DBPs formation upon chlorination of algal cells. Three model compounds, including bovine serum albumin (BSA), starch and fish oil, as surrogates of algal-derived proteins, carbohydrates and lipids, and cells of three algae species, representing blue-green algae, green algae, and diatoms, were chlorinated in the laboratory. The results showed that BSA (27 microg mg(-1) C) and fish oil (50 microg mg(-1) C) produced more than nine times higher levels of chloroform than starch (3 microg mg(-1) C). For the formation of HAAs, BSA was shown to have higher reactivity (49 microg mg(-1) C) than fish oil and starch (5 microg mg(-1) C). For the algal cells, Nitzschia sp. (diatom) showed higher chloroform yields (48 microg mg(-1) C) but lower HAA yields (43 microg mg(-1) C) than Chlamydomonas sp. (green algae) (chloroform: 34 microg mg(-1) C; HAA: 62 microg mg(-1) C) and Oscillatoria sp. (blue-green algae) (chloroform: 26 microg mg(-1) C; HAA: 72 microg mg(-1) C). The calculated chloroform formation of cells from the three algal groups, based on their biochemical compositions, was generally consistent with the experimental data, while the predicted values for HAAs were significantly lower than the observed ones. As compared to humic substances, such as humic and fulvic acids, the algal cells appeared to be important precursors of dichloroacetic acid.

We investigated how the history of local disturbances in a watershed can influence the regional coherence of ecosystem properties in lakes that have similar morphometry and climatic conditions. We measured sedimentary δ13C, δ15N, C:N and %BSiO2 in Sooke Lake Reservoir (SOL) and Shawnigan Lake (SHL), which are located within 4 km of each other on Vancouver Island, Canada. SOL is an impounded lake whose watershed has been fully protected over the last century, although the lake level has been raised 3 times via impoundment during this period. SHL has a similar limnological regime, but the surrounding watershed has been developed extensively for residential uses. We investigated how a pulse disturbance regime in SOL (i.e. repeated dam raising) and a press disturbance regime in SHL (i.e. persistent development) influenced the variability of paleoindicators in each system over time. We found that these contrasting disturbance regimes reduced the regional temporal coherence of aquatic productivity between the two lakes (indicated by %BSiO2), but did not influence the regional coherence of nutrient status or the main carbon sources of the lakes (indicated by %C, %N and δ13C). In contrast, an indicator of the sources and cycling of nitrogen (δ15N) showed increased coherence. Local disturbances also affected the variability of the paleoindicators within each system over time. In SOL, impoundments led to both declines (%N, δ15N) and increases (δ13C) in the variability of paleoindicators. In SHL, persistent watershed development led to lower variability of two paleoindicators (%N, %BSiO2). Overall, our data suggest that local disturbances can influence the %BSiO2 and C:N ratio of lake sediments, but are less likely to alter the regional coherence of %C, %N and δ13C between lakes.

Summary 1. Stable isotopes of nitrogen are useful for quantifying the trophic structure of food webs, but only if the variation in trophic enrichment (ΔN), which is the difference in δ15N between a consumer and its food, is small relative to the value of ΔN itself. 2. We examined the sources of variation in zooplankton ΔN by measuring the trophic enrichment (ΔN) of seven species of freshwater cladocerans, and by testing for an effect of age and temperature on the ΔN of Daphnia pulicaria. 3. We found that ΔN was similar among Cladocera and was not correlated with body size. Overall, the ΔN for D. pulicaria was 1.4‰ (SE = 0.69, n = 57), as was expected for the detritus diet that we used in our experiments. We found no effect of temperature (15–25 °C) on ΔN, but found that ΔN of D. pulicaria increased with increasing age (10–30 days). 4. We developed a new method to test for trophic-level variation in a group of consumers that explicitly accounts for the uncertainty in ΔN. Using this approach, we confirmed that natural assemblages of zooplankton feed at several trophic levels in lake food webs.