Research

29 pages, 6288 KiB

Open AccessFeature PaperArticle

Beyond Eutrophication: Vancouver Lake, WA, USA as a Model System for Assessing Multiple, Interacting Biotic and Abiotic Drivers of Harmful Cyanobacterial Blooms

by Gretchen Rollwagen-Bollens, Tammy Lee, Vanessa Rose and Stephen M. Bollens

Water 2018, 10(6), 757; https://doi.org/10.3390/w10060757 - 10 Jun 2018

Cited by 17 | Viewed by 4969

Abstract

Eutrophication of lakes and reservoirs has contributed to an increase in the magnitude and frequency of harmful cyanobacterial blooms; however, the interactive effects of nutrient availability (eutrophication) and other abiotic and biotic drivers have rarely been comprehensively studied in the field. We undertook [...] Read more.

Eutrophication of lakes and reservoirs has contributed to an increase in the magnitude and frequency of harmful cyanobacterial blooms; however, the interactive effects of nutrient availability (eutrophication) and other abiotic and biotic drivers have rarely been comprehensively studied in the field. We undertook an eight-year (2005–2013) research program that assessed the interaction of multiple factors driving cyanobacterial blooms in Vancouver Lake, a large, shallow eutrophic lake in Washington, USA. Our program consisted of nearly continuous monthly or weekly monitoring of water quality and plankton community composition over eight years, as well as multiple zooplankton grazing experiments over three years. We found a relatively consistent seasonal succession of phytoplankton and zooplankton assemblages, and a pattern of interacting factors influencing cyanobacterial bloom dynamics. Typically, a combined effect of decreased dissolved inorganic nitrogen (N), a sudden increase of dissolved inorganic phosphorus (P), and a cascading effect of zooplankton grazing created a ‘perfect storm’ of conditions that promoted the rapid proliferation of cyanobacteria over the two to three weeks before a bloom. At the blooms’ peaks, cyanobacterial carbon biomass reached as high as 20 µg L⁻¹, with total [chl a] often exceeding 750 µg L⁻¹. In the weeks following the blooms’ peaks, [PO₄-P] and [NH₄-N] dropped and copepod feeding rates fell to near zero, whereas microzooplankton grazing rates reached their maxima. Microzooplankton grazing impact, combined with low nutrient availability, then drove down cyanobacteria abundance. Vancouver Lake serves as a model for understanding multiple, interacting drivers of cyanobacterial bloom dynamics in shallow, temperate lakes, and is therefore an important system in which to investigate new questions related to the science and management of harmful algal blooms. Full article

(This article belongs to the Special Issue Eutrophication of Waterways: An Old Problem with Modern Consequences)

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13 pages, 1650 KiB

Open AccessFeature PaperArticle

Assessment of the Water Treatment Process’s Empirical Model Predictions for the Management of Aesthetic and Health Risks Associated with Cyanobacteria

by Arash Zamyadi, Rita K. Henderson, Kelly Newton, Jose Capelo-Neto and Gayle Newcombe

Water 2018, 10(5), 590; https://doi.org/10.3390/w10050590 - 02 May 2018

Cited by 6 | Viewed by 4940

Abstract

Potentially toxic cyanobacteria have been increasingly detected worldwide in water supply systems in recent years. The management of cyanobacteria in source water and through drinking water treatment processes has been a focus of global research for over thirty years. However, despite the volume [...] Read more.

Potentially toxic cyanobacteria have been increasingly detected worldwide in water supply systems in recent years. The management of cyanobacteria in source water and through drinking water treatment processes has been a focus of global research for over thirty years. However, despite the volume of research outcomes and the publication of guidance documents, gaps still exist in the knowledge base that inhibits the confident application of individual treatment strategies for the mitigation of aesthetic and health risks associated with cyanobacteria and their metabolites at the full-scale. The main objective of this project is to deliver a suite of tools and other resources to the water industry to support the implementation of a regulatory framework for the management of water quality for the assessment and management of aesthetic and toxicity risks associated with cyanobacteria. This study includes (1) the development of a guide (based on real-world examples) for treatment plant operators to perform plant audits and investigative sampling to assess the risk associated with cyanobacteria in their plants, and validate the performance of existing unit processes, and (2) the validation of a treatment model that can be applied at any plant and used to as a guide to the removals of cyanobacteria and metabolites and the expected quality of treated water under a range of challenges from cyanobacteria. Full-scale sampling was undertaken at three Australian regions in 14 water treatment plants to validate the model. The results presented in this paper represent a comprehensive database of full-scale removal efficiencies of 2-methylisoborneol (MIB) and geosmin for a range of water quality and treatment processes. The major findings and conclusions from this project include: (1) the investigative sampling procedures developed are effective and have been successfully applied by utilities; and (2) while routine monitoring data is important, investigative sampling within the water treatment plant provides more detailed and insightful information about the effectiveness of unit processes within the plant. This paper also identifies the knowledge gaps and needs for further studies. Full article

(This article belongs to the Special Issue Eutrophication of Waterways: An Old Problem with Modern Consequences)

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12 pages, 3653 KiB

Open AccessArticle

Bioturbation Effects of Chironomid Larvae on Nitrogen Release and Ammonia-Oxidizing Bacteria Abundance in Sediments

by Xigang Xing, Ling Liu, Wenming Yan, Tingfeng Wu, Liping Zhao and Xixi Wang

Water 2018, 10(4), 512; https://doi.org/10.3390/w10040512 - 20 Apr 2018

Cited by 6 | Viewed by 4428

Abstract

The purpose of this work was to reveal the Chironomid larvae bioturbation impact on N release and to find the mechanism of bioturbation to N conversion at the SWI (sediment–water interface). Sampling at four points during a 35-day incubation experiment was conducted. Two [...] Read more.

The purpose of this work was to reveal the Chironomid larvae bioturbation impact on N release and to find the mechanism of bioturbation to N conversion at the SWI (sediment–water interface). Sampling at four points during a 35-day incubation experiment was conducted. Two in situ techniques (microelectrode and Peeper) were used to capture more realistic and accurate microenvironment information around U-shaped corridors. The results demonstrate that the concentrations of ammonia nitrogen (NH₄⁺) and nitrate nitrogen (NO₃⁻) decreased by 21.26% and 19.50% in sediment and increased by 8.65% and 49.82% in the overlying water compared to the control treatment, respectively. An inverse relationship was observed between NH₄⁺ and NO₃⁻ concentrations in pore water in Chironomid larvae treatment, and they were significantly negatively/positively correlated with AOB (ammonia-oxidizing bacteria) abundance, respectively. This study confirmed that the Chironomid larvae bioturbation promoted the N (NH₄⁺ and NO₃⁻) release from sediment by in situ techniques, and a part of NH₄⁺ converted into NO₃⁻ during their flow into the overlying water through the nitrification affected by AOB. Furthermore, the main depth of bioturbation influence is approximately 12 cm below the SWI and the most significant bioturbation effect was observed from days 15 to 25. Full article

(This article belongs to the Special Issue Eutrophication of Waterways: An Old Problem with Modern Consequences)

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11 pages, 604 KiB

Open AccessArticle

Trophic State and Oxygen Conditions of Waters Aerated with Pulverising Aerator: The Results from Seven Lakes in Poland

by Hanna Siwek, Małgorzata Włodarczyk and Robert Czerniawski

Water 2018, 10(2), 219; https://doi.org/10.3390/w10020219 - 18 Feb 2018

Cited by 11 | Viewed by 4445

Abstract

Eutrophic lakes of all types are marked by oxygen shortage in the bottom waters during the summer season, which results in excessive release of phosphorus load. Therefore, numerous restoration activities (chemical precipitation, aeration) are being taken based on bottom-up control, which consists of [...] Read more.

Eutrophic lakes of all types are marked by oxygen shortage in the bottom waters during the summer season, which results in excessive release of phosphorus load. Therefore, numerous restoration activities (chemical precipitation, aeration) are being taken based on bottom-up control, which consists of limiting the nutrient pool available to lower trophic levels. The present study provides an efficiency analysis of pulverising aeration of waters in two stratified and five unstratified lakes located in Poland. The assessment was based on monitoring data (dissolved oxygen concentration (DO), % oxygen saturation (DO%), visibility of the Secchi disc (ZSD), the concentrations of: chlorophyll a (CHL), total phosphorus (TP) and total nitrogen (TN)) obtained before and after installation of the aerator on the lakes. The study was conducted during the spring and the summer seasons. Throughout the study period, the stratified lakes exhibited oxygen saturation <0.1%. Having completed the restoration activities, TN:TP ratio was found to gradually increase in all analysed lakes, which indicates that aeration may decrease phosphate content in the water column. In three lakes, the ratio was > 17, so phosphorus became the most growth-limiting nutrient. The restoration activities on four unstratified lakes had no significant effect on the changes of the Carlson trophic state indices (TSI). Either individual values of the TSI(TP), TSI(CHL) and TSI(ZSD) were comparable, or the value of TSI(TP) was higher than one or both of the remaining indices for all of the lakes. Full article

(This article belongs to the Special Issue Eutrophication of Waterways: An Old Problem with Modern Consequences)

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13 pages, 1131 KiB

Open AccessArticle

Phosphate Leaching from Green Roof Substrates—Can Green Roofs Pollute Urban Water Bodies?

by Agnieszka Karczmarczyk, Agnieszka Bus and Anna Baryła

Water 2018, 10(2), 199; https://doi.org/10.3390/w10020199 - 13 Feb 2018

Cited by 24 | Viewed by 5067

Abstract

Green roofs are an effective stormwater measure due to high water retention capacity and the ability of delaying stormwater runoff. However, low importance is still given to the pollutant leaching potential of substrates used in green roof construction. The aim of the study [...] Read more.

Green roofs are an effective stormwater measure due to high water retention capacity and the ability of delaying stormwater runoff. However, low importance is still given to the pollutant leaching potential of substrates used in green roof construction. The aim of the study is to estimate the concentrations and loads of P-PO₄³⁻ in runoff from extensive and intensive substrates. To achieve this goal, several commonly-used fresh substrates were analyzed for P-PO₄³⁻ leaching potential in different scale experiments, from laboratory batch tests, leaching column experiments, and long-term monitoring of open air green roof containers. The results of the study confirmed that fresh green roof substrates contain phosphorus in significant amounts of 17–145 mg∙P-PO₄³⁻/kg and, thus, can contribute to eutrophication of freshwater ecosystems. High correlation between phosphate content estimated by HCl extraction and cumulative load in leachate tests suggests that the batch HCl extraction test can be recommended for the comparison and selection of substrates with low potential P leaching. Volume-weighted mean concentrations and UALs of P-PO₄³⁻ leaching from fresh substrates were higher in cases of intensive substrates, but there was no clear relationship between substrate type and the observed P-PO₄³⁻ concentration range. To avoid increasing eutrophication of urban receivers the implementation of P reduction measures is strongly recommended. Full article

(This article belongs to the Special Issue Eutrophication of Waterways: An Old Problem with Modern Consequences)

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2821 KiB

Open AccessArticle

200 kHz Sonication of Mixed-Algae Suspension from a Eutrophic Lake: The Effect on the Caution vs. Outbreak Bloom Alert Levels

by Andinet Tekile, Ilho Kim and Jai-Yeop Lee

Water 2017, 9(12), 915; https://doi.org/10.3390/w9120915 - 24 Nov 2017

Cited by 5 | Viewed by 7969

Abstract

For effective ultrasonic algae removal, several studies have considered the ultrasound equipment linked factors, such as power and frequency. However, studies on the response of mixed algal cultures and associated water quality parameters to ultrasound are limited. In this lab-scale sonication, the removal [...] Read more.

For effective ultrasonic algae removal, several studies have considered the ultrasound equipment linked factors, such as power and frequency. However, studies on the response of mixed algal cultures and associated water quality parameters to ultrasound are limited. In this lab-scale sonication, the removal of cyanobacteria at a pre-set frequency of 200 kHz on mixed algae suspensions collected from a eutrophic lake was investigated. The caution (17.5 µg/L) and outbreak (1450 µg/L) alert levels in terms of chlorophyll-a (Chl-a) concentrations of the initial samples were each sonicated for 10, 15, and 20 min, and then kept in an incubator. Fifteen minutes of sonication resulted in best removal efficiency of 0.94 and 0.77, at an ultrasonic dose of 30 kWh/m³ at the outbreak and caution level concentrations, respectively. Immediately after 15 min sonication, and after standing in the incubator for a day, chlorophyll-a removal efficiencies of 0.28 and 0.90 were achieved in the outbreak level, respectively, and the matching removal efficiencies for the caution level were 0.23 and 0.64. Even though the removal was substantial in both cases, the final 147 µg/L chlorophyll-a concentration of the outbreak, which is itself still in the outbreak level range, shows that ultrasonication is not effective to satisfactorily remove algae from a concentrated suspension. Total dissolved nitrogen and chemical oxygen demand were reduced, overall, due to sonication. However, total dissolved phosphorus of the concentrated level was increased during the treatment. Although sonication needs further replicated experimental testing in whole-lake systems, our results show that 200 kHz sonication was able to reduce chlorophyll-a concentrations in small-scale laboratory tests. Full article

(This article belongs to the Special Issue Eutrophication of Waterways: An Old Problem with Modern Consequences)

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1286 KiB

Open AccessArticle

The Biomass and Physiological Responses of Vallisneria natans (Lour.) Hara to Epiphytic Algae and Different Nitrate-N Concentrations in the Water Column

by Fenli Min, Jincheng Zuo, Yi Zhang, Qingwei Lin, Biyun Liu, Jian Sun, Lei Zeng, Feng He and Zhenbin Wu

Water 2017, 9(11), 863; https://doi.org/10.3390/w9110863 - 22 Nov 2017

Cited by 13 | Viewed by 4972

Abstract

Increasing N concentration and the high density of epiphytic algae are both key factors leading to the decline of submerged macrophytes in many eutrophic lakes. In order to investigate the impacts of increased nitrate-N concentration and the growth of epiphytic algae on the [...] Read more.

Increasing N concentration and the high density of epiphytic algae are both key factors leading to the decline of submerged macrophytes in many eutrophic lakes. In order to investigate the impacts of increased nitrate-N concentration and the growth of epiphytic algae on the decline of submerged vegetation, we conducted a 2 × 4 factorial experiment with the submerged macrophyte Vallisneria natans (Lour.) Hara by measuring the biomass of plants and some physiological indexes in leaves of V. natans under four nitrate-N concentrations in the water column (0.5, 2.5, 5, and 10 mg/L) and two epiphytic groups (epiphytic algae group and no epiphytic algae group). The results suggested that epiphytic algae could impose adverse effects on the biomass accumulation of V. natans, while the increasing nitrate-N concentration (0.5–10 mg/L) could oppositely promote this process and counteract the adverse effect of epiphytic algae. When nitrate-N concentration was 5 mg/L, the total chlorophyll content in leaves of V. natans in the epiphytic algae group was prominently lower compared with the no epiphytic algae group, while MDA, free proline, and anti-oxidant enzyme (SOD, POD, CAT) activities were significantly higher. Overhigh nitrate-N concentration in the water column also directly imposed adverse effects on the physiology of V. natans. When nitrate-N concentration was over 5 mg/L, the total chlorophyll content and free proline decreased in the no epiphytic algae group, while soluble carbohydrates and soluble proteins decreased when nitrate-N was over 2.5 mg/L. Meanwhile, epiphytic algae and nitrate-N content imposed a synergetic effect on the anti-oxidant enzyme activities of V. natans. When nitrate-N concentration was over 5 mg/L, SOD, POD, and CAT activities kept constant or decreased, which indicated that the oxidation resistance of V. natans was inhibited by stress. Our results indicate that epiphytic algae and increasing nitrate-N concentration in the water column could severally or synergistically impose adverse effects on the physiology of submerged macrophytes and are both key factors leading to the decline of submerged macrophytes. Full article

(This article belongs to the Special Issue Eutrophication of Waterways: An Old Problem with Modern Consequences)

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1148 KiB

Open AccessArticle

Sediment-Water Methane Flux in a Eutrophic Pond and Primary Influential Factors at Different Time Scales

by Xinhong Liu, Yan Gao, Zhenhua Zhang, Jia Luo and Shaohua Yan

Water 2017, 9(8), 601; https://doi.org/10.3390/w9080601 - 14 Aug 2017

Cited by 15 | Viewed by 4557

Abstract

Water bodies are major areas for methane release. Eutrophic water bodies may promote methane flux. The sediment-water interface is the major location for methane release, and studies on sediment-water interactions are necessary to regulate methane release in water. However, relevant studies on methane [...] Read more.

Water bodies are major areas for methane release. Eutrophic water bodies may promote methane flux. The sediment-water interface is the major location for methane release, and studies on sediment-water interactions are necessary to regulate methane release in water. However, relevant studies on methane flux at the sediment-water interface are limited due to methodological difficulties. Using an innovative gas trapping device, this study investigated the seasonal characteristics and diel variation in summer methane flux from eutrophic water bodies and analyzed the correlations between temperature, dissolved oxygen (DO), different forms of nitrogen and the methane flux at different time scales. The results showed that methane flux in the eutrophic pond was high and had distinct seasonal variations and diel variations: the average value was 2.81 ± 0.19 mmol m⁻² h⁻¹ in summer, which was significantly greater than that in spring (0.62 ± 0.14 mmol m⁻² h⁻¹), autumn (0.63 ± 0.10 mmol m⁻² h⁻¹) (p < 0.01) and winter (approached zero). The diel characteristics of methane flux in summer exhibited a unimodal pattern of increase at night and decrease during the day. The correlation analysis showed that the sediment-water methane flux rate of the water body was significantly positively correlated with the temperature and NH₄⁺ concentration and significantly negatively correlated with DO, NO₃⁻ and NO₂⁻ concentration. Meanwhile, among different time scales, the correlations between NO₃⁻/NH₄⁺ concentration and methane flux were the highest at the diel scale in summer (R² = 0.68, 0.87 respectively) when the temperature and DO vibration was low and the relationship between temperature/DO and methane flux was poor (R² = 0.45, 0.87 respectively). This study considered that higher NH₄⁺-N and lower NO₃⁻-N/NO₂⁻-N content in eutrophic water could have an effect on the high methane flux in summer as well as the low dissolved oxygen content. Full article

(This article belongs to the Special Issue Eutrophication of Waterways: An Old Problem with Modern Consequences)

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