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1.
Sci Rep ; 9(1): 17528, 2019 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-31772202

RESUMO

The passive sampling method of diffusive gradients in thin-films (DGT) was developed to provide a quantitative and time-integrated measurement of microcystin-LR (MC-LR) in waters. The DGT method in this study used HLB (hydrophilic-lipophilic-balanced) material as a binding agent, and methanol as an eluent. The diffusion coefficient of MC-LR was 5.01 × 10-6 cm2 s-1 at 25 °C in 0.45 mm thick diffusion layer. This DGT method had a binding capacity of 4.24 µg per binding gel disk (3.14 cm2), ensuring sufficient capacity to measure MC-LR in most water matrices. The detection limit of HLB DGT was 0.48 ng L-1. DGT coupled to analysis by HPLC appears to be an accurate method for MC-LR monitoring. Comparison of DGT measurements for MC-LR in water and a conventional active sampling method showed little difference. This study demonstrates that HLB-based DGT is a useful tool for in situ monitoring of MC-LR in fresh waters.

2.
Ecotoxicol Environ Saf ; 185: 109668, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31574372

RESUMO

Microcystins and polycyclic aromatic hydrocarbons commonly co-exist in eutrophic freshwater environments. However, their combined toxicity remains unknown. The aim of this study was to evaluate the combined toxic effects of microcystin-LR (MC-LR) and phenanthrene (Phe) on duckweed (Lemna gibba L.) during a short-term exposure (7 d). L. gibba was exposed to a range of environmentally relevant concentrations of MC-LR (5, 50, 250, 500 µg/L) and Phe (0.1, 1, 5, 10 µg/L), both individually and in MC-LR + Phe mixtures (5 + 0.1, 50 + 1, 250 + 5, 500 + 10 µg/L). Subsequently, biomarkers of toxicity such as growth, chlorophyll-a, and antioxidant enzyme activity (catalase, superoxide dismutase, and peroxidase) were analyzed in L. gibba. Growth and the antioxidant system of L. gibba were not significantly inhibited by Phe alone, whereas higher concentrations of individual MC-LR (≥50 µg/L) significantly inhibited growth and induced oxidative stress. Based on Abott's formula, their interaction effects were concentration dependent. Antagonistic effects were observed when exposed to combinations of lower concentrations of MC-LR and Phe (≤50 + 1 µg/L), while additive or synergistic effects were induced at higher concentrations of both compounds (≥250 + 5 µg/L). Moreover, higher concentrations of Phe (≥5 µg/L) increased the accumulation of MC-LR in L. gibba. Our results suggested that the toxic effects of MC-LR and phenanthrene were exacerbated only when they co-exist in water bodies at relatively high concentrations. Consequently, co-existence of MC-LR and Phe at low levels are unlikely to exacerbate ecological hazards to L. gibba in most aquatic environments, at least based on responses of this plant.


Assuntos
Antioxidantes/metabolismo , Araceae/efeitos dos fármacos , Microcistinas/toxicidade , Fenantrenos/toxicidade , Araceae/enzimologia , Catalase/metabolismo , Clorofila/análogos & derivados , Clorofila/metabolismo , Sinergismo Farmacológico , Estresse Oxidativo/efeitos dos fármacos , Peroxidase/metabolismo , Superóxido Dismutase/metabolismo
3.
Chemosphere ; 234: 34-42, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31203039

RESUMO

Due to excessive loadings of nitrogen (N) and phosphorus (P), frequent blooms of harmful cyanobacteria and their associated cyanotoxins pose serious threats to recreational usage and human health. However, whether cyanobacteria growth and toxin production are limited by N, P, or both N + P is still not clear. Thus, we conducted a nutrient enrichment bioassay in situ in Spring Lake, a eutrophic lake in west Michigan, USA, to examine the influence of nutrient limitation on the proliferation of algal blooms and the production of microcystins (MC). N or P addition alone resulted in a slight increase in the concentration of chlorophyll-a (Chl-a), suggesting a positive effect on phytoplankton growth, but alone, neither were sufficient to induce algal blooms. In contrast, the combination of N and P had a significant and positive influence on phytoplankton growth and MC production. Compared to controls, the N + P treatment resulted in high concentrations of Chl-a and MC, as well as high pH and dissolved oxygen. In addition, significant increases were observed in different MC analogues for each treatment; the highest concentrations of intracellular MC-LR, -RR, -YR, and TMC (total MC) were found in the N + P treatment with values of 9.16, 6.10, 2.57, and 17.82 µg/L, respectively. This study suggests that at least in this temperate coastal lake, cyanobacterial blooms and associated MC are influenced more by combined N and P enrichment than by N or P alone, indicating that managing both nutrients is important for effectively reducing algal blooms and MC production.


Assuntos
Lagos/microbiologia , Microcistinas/metabolismo , Nitrogênio/farmacologia , Nutrientes/farmacologia , Fósforo/farmacologia , Fitoplâncton/crescimento & desenvolvimento , Carcinógenos/metabolismo , Eutrofização , Lagos/análise , Fitoplâncton/efeitos dos fármacos
4.
Sci Total Environ ; 650(Pt 2): 1969-1979, 2019 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-30290339

RESUMO

Many riverine wetlands have been drained for the creation of agricultural land; however, global declines in freshwater biodiversity have begun to motivate wetland restoration projects around the world. Legacy phosphorus (P) increases the risk that wetland restoration may liberate excess P to the water column and connecting waterbodies, resulting in a trade-off of restored habitat for degraded water quality. To avoid this trade-off, we dredged a former agricultural parcel prior to hydrologic reconnection, and evaluated restoration success by comparing sediment P dynamics before and after dredging. First, results from P adsorption isotherm experiments suggested that after dredging, the sediment would act as a sink for dissolved P only when water column soluble reactive phosphorus (SRP) concentrations exceeded 40 µg L-1. Additionally, the dredging depth (~1 m on average) exposed sediment with significantly reduced P sorption capacities. Second, P release rates were measured in sediment cores that were incubated under two water temperatures (ambient; +2 °C) and two oxygen levels (oxic; hypoxic). Average maximum total phosphorus (TP) release rates ranged from 40 to 85 mg m-2 d-1 before dredging and from 0 to 7 mg m-2 d-1 after dredging, resulting in a 95-99% reduction in TP release rates after dredging. Similar reductions were measured also for SRP release rates. The significant reduction in sediment P release after dredging now creates a high potential for this restored wetland to reduce net P loads into downstream waters by facilitating the deposition and burial of particulate P. We conclude that sediment dredging can be a useful technique for balancing the goals of habitat restoration and water quality improvements in wetlands restored on former agricultural lands.

5.
Environ Pollut ; 259: 113884, 2019 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-31918143

RESUMO

High concentrations of microcystins (MCs) in sediment pose a serious hazard to aquatic and terrestrial organisms. Hence, we investigated the seasonal variation of dominant MCs (MC-LR, MC-RR and MC-YR) in sediments of Lake Taihu over four seasons for the first time. Sediment MCs varied seasonally (p < 0.01) with concentrations highest in August and lowest in February. The MCs were dominated by MC-LR (61.47%) with the content ranging from 0.02 to 2.37 µg/g dry weight in sediment. The three MC congeners and their proportions were significantly correlated with latitude and longitude. Meiliang Bay in the north had the highest MCs of all sites, while the eastern part of the lake had a high level especially in August. Variation of MC-LR and MC-RR concentrations was significantly correlated (p < 0.05) with water temperature, dissolved total organic carbon, cyanobacteria density, total suspended solid particles, and total organic carbon and total nitrogen in sediment, while MC-YR was negatively correlated (p < 0.01) with nutrients in the water column and heavy metals in sediments. An ecological risk assessment suggested the MCs already pose significant adverse effects on Potamopyrgus antipodarum; although the adverse effects on humans were weak, children were at greater risk than adults.

6.
Artigo em Inglês | MEDLINE | ID: mdl-30257513

RESUMO

Reducing nonpoint source pollution is an ongoing challenge in watersheds throughout the world. Implementation of best management practices, both structural and nonstructural, is the usual response to this challenge, with the presumption that they are effective. However, monitoring of their efficacy is not a standard practice. In this study, we evaluate the effectiveness of two wetland restoration projects, designed to handle runoff during high flow events and serve as flow-through retention basins before returning flow further downstream. The Macatawa Watershed is located in west Michigan, is heavily agricultural, and drains into Lake Macatawa, a hypereutrophic lake with total phosphorus concentrations usually exceeding 100 µg/L. We measured turbidity, total phosphorus, and soluble reactive phosphorus both upstream and downstream of these wetland complexes during base flow and storm events. While both turbidity and phosphorus increased significantly during storm events compared to baseflow, we found no significant difference in upstream vs. downstream water quality two years following BMP construction. We also measured water quality in Lake Macatawa, and found the lake remained highly impaired. Possible reasons for the lack of improved water quality: (1) The restored wetlands are too young to function optimally in sediment and phosphorus retention; (2) the scale of these BMPs is too small given the overall loads; (3) the locations of these BMPs are not optimal in terms of pollutant reduction; and (4) the years following postconstruction were relatively dry so the wetlands had limited opportunity to retain pollutants. These possibilities are evaluated.


Assuntos
Conservação dos Recursos Naturais/métodos , Monitoramento Ambiental , Lagos/química , Fósforo/análise , Poluentes Químicos da Água/análise , Poluição da Água/prevenção & controle , Eutrofização , Michigan , Avaliação de Programas e Projetos de Saúde , Poluição da Água/análise , Áreas Alagadas
7.
Sci Total Environ ; 628-629: 1352-1361, 2018 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-30045556

RESUMO

Eutrophication and recovery of Muskegon Lake resulted from a complex set of interacting factors according to diatom-inferred total phosphorus (TP), geochemical proxies, detailed modeling of land use land cover change in the watershed, and accounts of past point source management and non-native species invasions. Benthic and planktonic diatoms responded to phosphorus environments differently in this lake that receives 95% of its input from one river and has only a 23days average retention time. Planktonic diatoms reflected river conditions more than benthic diatoms, and benthos reflected lake conditions more than plankton. Inferred TP from planktonic diatoms indicated the Muskegon River was relatively nutrient rich compared to inferred TP for Muskegon Lake based on benthic diatoms before Europeans settled the watershed. Early European settlement and logging caused no changes in phosphorus condition in the Muskegon River, but modest increases in phosphorus were indicated in Muskegon Lake during the middle and late thirds of the 19th century. Extensive watershed-scale agricultural activity in the early 20th century apparently had little effect on trophic status of the lake, perhaps because it preceded high fertilizer use on farms. During the industrial and population boom in the watershed during the early half of the 20th century, river conditions changed little, but eutrophication of Muskegon Lake increased greatly. Reduction in river phosphorus by dams occurred during the first half of the 20th century. Phosphorus reduction in the lake was indicated after advanced wastewater treatment for Muskegon Township was implemented in 1973. Current diatom inferred phosphorus concentration in the lake is the same as before European settlement, however many attributes of the lake still differ because other stressors persist.

8.
Environ Pollut ; 240: 44-50, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29729568

RESUMO

A 120-day field study was carried out near Lake Taihu to evaluate the bioaccumulation of microcystin (MC) congeners in a soil-plant system, as well as to assess human health risk when consuming edible plants irrigated with MCs-contaminated water. Natural cyanobacteria bloom-containing lake water (lake water) and half-diluted natural cyanobacteria bloom-containing lake water with tap water (half-lake water) were used to irrigate lettuce and rice. An additional treatment involving fertilization with a cyanobacteria bloom was applied just to the lettuce experiment. MCs in soils, roots, leaves and grains (rice) were detected. In the soil-lettuce system, the three MC congeners in soils fertilized with a cyanobacteria bloom were not detected. The highest concentrations of MCs detected in soils, lettuce roots and leaves were 24.8 (MC-LR 10.1, MC-RR 10.5, MC-YR 4.2) µg kg-1, 424 (MC-LR 168, MC-RR 194, MC-YR 61.5) µg kg-1 and 183 (MC-LR 78.0, MC-RR 76.8, MC-YR 28.1) µg kg-1, respectively, in the lake water treatment. In the soil-rice system, the highest concentration of MCs was accumulated in roots 1504 (MC-LR 634, MC-RR 573, MC-YR 297) µg kg-1, in the lake water treatment. However, the concentration of MCs that accumulated in grains was extremely low with a total MCs concentration of 5.2 (MC-LR 2.1, MC-RR 2.0, MC-YR 1.1) µg kg-1 in the lake water treatment. According to the estimated daily intake (EDI) value, fertilizing with an appropriate amount (0.2% or less, w/w, dry weight (DW)) of a cyanobacteria bloom, as well as consuming rice irrigated with lake water would not pose a threat to human health. However, the EDI values for both adults and children reached tolerable daily intake (TDI) value, assuming they consumed lettuce irrigated with lake water. Results obtained from the growth and yield indicators suggest that MCs bioaccumulation in edible plants is not necessarily coupled with phytotoxic effects.


Assuntos
Monitoramento Ambiental , Microcistinas/análise , Folhas de Planta/química , China , Cianobactérias , Humanos , Lagos/microbiologia , Alface/crescimento & desenvolvimento , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/fisiologia , Medição de Risco , Solo
9.
Chemosphere ; 206: 474-482, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29775940

RESUMO

Microcystins and copper commonly co-exist in the natural environment, but their combined toxicity remains unclear, especially in terrestrial plants. The present study investigated the toxicity effects of microcystin-LR (0, 5, 50, 500, 1000 µg L-1) and copper (0, 50, 500, 1000, 2000 µg L-1), both individually and in mixture, on the germination, growth and oxidative response of lettuce. The bioaccumulation of microcystin-LR and copper was also evaluated. Results showed that the decrease in lettuce germination induced by copper alone was not significantly different from that induced by the mixture, and the combined toxicity assessment showed a simple additive effect. Lettuce growth was not significantly reduced by microcystin-LR alone, whereas it was significantly reduced by copper alone and the mixture when copper concentration was higher than 500 µg L-1. High concentrations of microcystin-LR (1000 µg L-1) and copper (≥50 µg L-1),as well as their mixture (≥50 + 500 µg L-1), induced oxidative stress in lettuce. A synergistic effect on the growth and antioxidative system of lettuce was observed when exposed to low concentrations of the mixture (≤50 + 500 µg L-1), whereas an antagonistic effect was observed at high concentrations (≥1000 + 2000 µg L-1). Moreover, the interaction of microcystin-LR and copper can increase their accumulation in lettuce. Our results suggest that the toxicity effects of microcystin-LR and copper are exacerbated when they co-exist in the natural environment at low concentrations, which not only negatively affects plant growth but also poses a potential risk to human health via the food chain.


Assuntos
Cobre/toxicidade , Alface/efeitos dos fármacos , Microcistinas/toxicidade , Humanos
10.
Ecotoxicol Environ Saf ; 156: 141-147, 2018 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-29549737

RESUMO

An experiment was conducted to investigate the effect of farming activities on microcystin-LR (MC-LR) degradation in soils. Three farming activities were assessed: 1) fertilization via addition of different nitrogen sources and organic matter; 2) pesticide application by addition of different commercial pesticides; and 3) irrigation by addition of different amount of water. The contribution of the two major degradation processes of MC-LR in soils, photodegradation and biodegradation, were also evaluated. MC-LR was added into the soil samples to create a concentration of 500 µg kg-1 for each treatment. Results showed that natural degradation of MC-LR in soils was mainly by biodegradation rather than photodegradation. MC-degradation was stimulated by the addition of NaNO3 and humic acid, whereas degradation was inhibited by addition of NH4Cl, glucose, and glycine. Application of high concentrations of glyphosate and chlorothalonil significantly inhibited the degradation of MC-LR in soils and the half-life was almost twice as long as the control. No significant effect was found by addition of CO(NH2)2 and dimethoate. Both low (10%) and high water content (60%) could lead to inhibition of MC-LR degradation. Results from our study help to inform farm practices that could alleviate contamination by MC-LR in agroecosystems.


Assuntos
Biodegradação Ambiental , Luz , Microcistinas/química , Fotólise , Solo/química , Água/química , Agricultura , Cloreto de Amônio/análise , Fenômenos Químicos , Fertilizantes/análise , Substâncias Húmicas/análise , Nitratos/análise , Nitrogênio/química , Microbiologia do Solo , Microbiologia da Água
11.
Sci Rep ; 7(1): 15954, 2017 11 21.
Artigo em Inglês | MEDLINE | ID: mdl-29162925

RESUMO

Irrigation with eutrophic water containing cyanobacteria toxins poses a potential risk to soil animals. To evaluate ecotoxicological effect of microcystins (MCs) on earthworms, filter paper acute toxicity test, avoidance test and a 14-d artificial soil test were carried out. No acute toxicity was found in the filter paper test, and earthworms showed no avoidance response to MCs exposure. In the artificial soil test, Eisenia fetida were allowed to grow in presence or absence of MCs (0, 1, 10, 100, 1000 µg kg-1 of soil) for 1, 7, and 14 d. Results showed that MCs could bioaccumulated in earthworm. A stimulatory effect on catalase and glutathione oxidase activities induced by MCs was found on day 1, and both of them were significantly inhibited at 100 and 1000 µg kg-1 on days 14. The superoxide dismutase activity was relatively insensitive. Significant increase of malondialdehyde content and decrease of neutral red retention time were observed at 100 and 1000 µg kg-1 on days 7 and 14. Our results suggest that MCs induces oxidative stress on earthworms, which leads to disruption of the antioxidant system and lipid peroxidation, as well as alterations in lysosomal membrane stability.


Assuntos
Toxinas Bacterianas/toxicidade , Toxinas Marinhas/toxicidade , Microcistinas/toxicidade , Oligoquetos/efeitos dos fármacos , Oligoquetos/metabolismo , Testes de Toxicidade , Análise de Variância , Animais , Aprendizagem da Esquiva/efeitos dos fármacos , Bioensaio , Membranas Intracelulares/efeitos dos fármacos , Membranas Intracelulares/metabolismo , Lisossomos/efeitos dos fármacos , Lisossomos/metabolismo , Oligoquetos/enzimologia
12.
Harmful Algae ; 68: 168-177, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28962977

RESUMO

Cyanobacterial harmful algal blooms are prevalent around the world, influencing aquatic organisms and altering the physico-chemical properties in freshwater systems. However, the response of bacterial communities to toxic cyanobacterial blooms and associated microcystins (MC) remain poorly understood even though global concentrations of MC have increased dramatically in the past few decades. To address this issue, the dynamics of bacterial community composition (BCC) in the water column and how BCC is influenced by both harmful cyanobacterial blooms and environmental factors were investigated on a monthly basis from August 2013 to July 2014 in Lake Taihu, China. Non-metric multidimensional scaling (NMDS) revealed that seasonal variation in BCC was significant, and that the succession of BCC greatly depends on changes in environmental conditions. Redundancy analysis (RDA) results showed that the overall variation of BCC was explained mainly by dissolved oxygen (DO), nitrate nitrogen (NO3--N), and Microcystis. The alpha biodiversity of the bacterial community was different among months with the highest diversity in February and the lowest diversity in October. Furthermore, significant negative relationships were found between alpha biodiversity indices and Microcystis abundance as well as with intracellular MC concentrations, indicating that Microcystis and associated MC may influence the bacterial community structure by reducing its biodiversity. This study shows that potential associations exist between toxic cyanobacterial blooms and bacterial communities but more investigations are needed to obtain a mechanistic understanding of their complex relationships.


Assuntos
Cianobactérias/fisiologia , Proliferação Nociva de Algas/fisiologia , Lagos/microbiologia , Microbiota , Biodiversidade , China , Clorofila A/análise , Microcistinas/análise , Estações do Ano , Fatores de Tempo
13.
Ecotoxicol Environ Saf ; 145: 431-435, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28778041

RESUMO

We conducted an indoor culture experiment to evaluate the phytotoxic effect of microcystins (MCs) on rice. After a 30day exposure, MCs induced a clear inhibition in rice growth, as well as a disruption of its antioxidant system and lipid peroxidation. We observed an increase in root membrane permeability; the conductivity of the leakage solution of the roots at 50 and 500µgL-1 was significantly increased by 77% and 136%, respectively, compared to the control. Uptake of microelements (Fe, Mn, Cu and Zn) was generally not affected after the 30day exposure to MCs. In contrast, uptake of macroelements, with the exception of K, was stimulated by MCs. Ca content in roots exposed to 500µgL-1 showed the greatest increase, by 47%, compared to the control. We propose the following mechanisms to explain our experimental results: exposure of rice roots to MCs leads to root damage and loss of membrane integrity, resulting in greater permeability and uptake of elements.


Assuntos
Permeabilidade da Membrana Celular/efeitos dos fármacos , Microcistinas/toxicidade , Oryza/efeitos dos fármacos , Raízes de Plantas/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Antioxidantes/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Microcistinas/metabolismo , Oryza/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Raízes de Plantas/metabolismo , Poluentes Químicos da Água/metabolismo
14.
Environ Pollut ; 231(Pt 1): 134-142, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28797902

RESUMO

A 30-day indoor incubation experiment was conducted to investigate the effects of different concentrations of microcystin (1, 10, 100 and 1000 µg eq. MC-LR L-1) on soil enzyme activity, soil respiration, physiological profiles, potential nitrification, and microbial abundance (total bacteria, total fungi, ammonia-oxidizing bacteria and archaea) in two lakeside soils in China (Soil A from the lakeside of Lake Poyanghu at Jiujiang; Soil B from the lakeside of Lake Taihu at Suzhou). Of the enzymes tested, only phenol oxidase activity was negatively affected by microcystin application. In contrast, dehydrogenase activity was stimulated in the 1000 µg treatment, and a stimulatory effect also occurred with soil respiration in contaminated soil. The metabolic profiles of the microbial communities indicated that overall carbon metabolic activity in the soils treated with high microcystin concentrations was inhibited, and high concentrations of microcystin also led to different patterns of potential carbon utilization. High microcystin concentrations (100, 1000 µg eq. MC-LR L-1 in Soil A; 10, 100 1000 µg eq. MC-LR L-1 in Soil B) significantly decreased soil potential nitrification rate. Furthermore, the decrease in soil potential nitrification rate was positively correlated with the decrease of the amoA gene abundance, which corresponds to the ammonia-oxidizing bacterial community. We conclude that application of microcystin-enriched irrigation water can significantly impact soil microbial community structure and function.


Assuntos
Monitoramento Ambiental , Microcistinas/toxicidade , Microbiologia do Solo , Poluentes do Solo/toxicidade , Solo/química , Amônia/metabolismo , Archaea/metabolismo , Bactérias/metabolismo , China , Lagos/química , Lagos/microbiologia , Microcistinas/metabolismo , Nitrificação , Oxirredução
15.
Chemosphere ; 184: 299-308, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28601663

RESUMO

Phytoplankton and bacterioplankton are integral components of aquatic food webs and play essential roles in the structure and function of freshwater ecosystems. However, little is known about how phyto- and bacterioplankton may respond synchronously to changing environmental conditions. Thus, we analyzed simultaneously the composition and structure of phyto- and bacterioplankton on a monthly basis over 12 months in cyanobacteria-dominated areas of Lake Taihu and compared their responses to changes in environmental factors. Metric multi-dimensional scaling (mMDS) revealed that the temporal variations of phyto- and bacterioplankton were significant. Time lag analysis (TLA) indicated that the temporal pattern of phytoplankton tended to exhibit convergent dynamics while bacterioplankton showed highly stable or stochastic variation. A significant directional change was found for bacterioplankton at the genus level and the slopes (rate of change) and regression R2 (low stochasticity or stability) were greater if Cyanobacteria were included, suggesting a higher level of instability in the bacterial community at lower taxonomy level. Consequently, phytoplankton responded more rapidly to the change in environmental conditions than bacterioplankton when analyzed at the phylum level, while bacterioplankton were more sensitive at the finer taxonomic resolution in Lake Taihu. Redundancy analysis (RDA) results showed that environmental variables collectively explained 51.0% variance of phytoplankton and 46.7% variance of bacterioplankton, suggesting that environmental conditions have a significant influence on the temporal variations of phyto- and bacterioplankton. Furthermore, variance partitioning indicated that the bacterial community structure was largely explained by water temperature and nitrogen, suggesting that these factors were the primary drivers shaping bacterioplankton.


Assuntos
Cianobactérias/fisiologia , Ecossistema , Fitoplâncton/fisiologia , China , Lagos/microbiologia , Nitrogênio/análise , Temperatura Ambiente , Fatores de Tempo
16.
J Great Lakes Res ; 43(3): 161-168, 2017 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-30034084

RESUMO

A comprehensive inventory of ecosystem services across the entire Great Lakes basin is currently lacking and is needed to make informed management decisions. A greater appreciation and understanding of ecosystem services, including both use and non-use services, may have avoided misguided resource management decisions in the past that have resulted in legacies inherited by future generations. Given the interest in ecosystem services and lack of a coherent approach to addressing this topic in the Great Lakes, a summit was convened involving 28 experts working on various aspects of ecosystem services in the Great Lakes. The invited attendees spanned a variety of social and natural sciences. Given the unique status of the Great Lakes as the world's largest collective repository of surface freshwater, and the numerous stressors threatening this valuable resource, timing was propitious to examine ecosystem services. Several themes and recommendations emerged from the summit. There was general consensus that 1) a comprehensive inventory of ecosystem services throughout the Great Lakes is a desirable goal but would require considerable resources; 2) more spatially and temporally intensive data are needed to overcome our data gaps, but the arrangement of data networks and observatories must be well-coordinated; 3) trade-offs must be considered as part of ecosystem services analyses; and 4) formation of a Great Lakes Institute for Ecosystem Services, to provide a hub for research, meetings, and training is desirable. Several challenges also emerged during the summit, which are discussed in the paper.

17.
Environ Monit Assess ; 189(1): 37, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28013476

RESUMO

Diatom bioassessment of streams/rivers does not distinguish between live (cells with intact chloroplasts) and dead (empty cells) individuals, even though most diatom samples collected from the field will be composed of a mixture of both. This study aimed to evaluate whether percentage of live diatoms (PLD), live diatom density and chlorophyll a, and diatom species compositions can be used as indicators of hydrologic disturbance in an urban stream. We deployed artificial substrates on a monthly basis and collected periphyton samples weekly over the course of one calendar year (n = 182) in three tributaries of urbanized Ruddiman Creek (Michigan, USA). We also collected samples before and after six major storm events (>0.5 cm rain). We found no temporal patterns in PLD (Mann-Kendall test p > 0.05) or species composition (non-metric multidimensional scaling (NMDS) ordination), which may be explained by a diatom composition already tolerant to frequent disturbance. There was no difference in PLD before and after storm events, which might partially be explained by their disturbance resistance due to different assemblage ages (1, 2, and 4 weeks old) before the storms. High flow had differential effects on diatom species; loosely attached Navicula and Nitzschia species were more easily removed compared to stalk-forming Gomphonema parvulum. The most important environmental variable that was found to affect live diatom density and chlorophyll was stream width, which has an indirect effect (as a measure of discharge) on periphyton assemblages. In conclusion, PLD was found to be unsuitable metric for assessing stormwater runoff in urban streams where periphyton may not have enough time to form mature communities.


Assuntos
Diatomáceas/fisiologia , Poluição da Água/análise , Qualidade da Água , Clorofila/análogos & derivados , Clorofila/análise , Clorofila A , Monitoramento Ambiental/métodos , Michigan , Chuva , Rios/química , Urbanização , Movimentos da Água
18.
Environ Sci Pollut Res Int ; 23(22): 22596-22605, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27557962

RESUMO

We studied the phosphorus dynamics in a former wetland, which had been converted to a celery farm, and now consists of two shallow, flooded ponds that are being proposed for aquatic habitat restoration. However, like many agricultural areas, this site is plagued by phosphorus legacy issues. Proposed restoration includes hydrologic reconnection of these ponds to its adjacent stream, which are now isolated from one another by an earthen berm, to create a wetland complex. One of the two flooded ponds was partially dredged, whereas the other one has remained undredged. Water column, sediment pore water, and sediment total phosphorus concentrations were significantly greater in the undredged pond compared to the dredged pond, but in both cases phosphorus levels in the water columns (mean TP 929 vs. 133 µg/L in undredged vs. dredged ponds, respectively) would exacerbate downstream water quality issues if hydrologic reconnection occurred without first addressing the phosphorus issue. Sediment isotherm and maximum sorption data indicated that the sediments are close to phosphorus saturation in the undredged pond; simulated dredging of the cores revealed that exposure of deeper sediment layers would increase sorption capacity. Pore water SRP concentrations increased with sediment depth and were significantly greater in the undredged vs. dredged pond at both the 1-4-cm depth (2249 vs. 112 µg/L) and 14-17-cm depth (5506 vs. 222 µg/L). This study provides a framework for other projects that need to balance the competing demands of habitat restoration vs. water quality when restoring wetlands that have been converted to agricultural production.


Assuntos
Recuperação e Remediação Ambiental , Fazendas , Fósforo/química , Áreas Alagadas , Sedimentos Geológicos , Tanques , Poluentes Químicos da Água/análise
19.
Sci Rep ; 6: 31097, 2016 08 08.
Artigo em Inglês | MEDLINE | ID: mdl-27499175

RESUMO

Although there have been numerous studies on microcystin (MC) accumulation in aquatic organisms recently, the bioaccumulation of MCs in relatively small sized organisms, as well as potential influencing factors, has been rarely studied. Thus, in this study, we investigated the bioaccumulation of three MC congeners (-LR, -RR and -YR) in the chironomid larvae of Tanypus chinensis (an excellent food source for certain fishes), the potential sources of these MCs, and potentially relevant environmental parameters over the course of one year in Lake Taihu, China. MC concentrations in T. chinensis varied temporally with highest concentrations during the warmest months (except August 2013) and very low concentrations during the remaining months. Among the three potential MC sources, only intracellular MCs were significantly and positively correlated with MCs in T. chinensis. Although MC concentrations in T. chinensis significantly correlated with a series of physicochemical parameters of water column, cyanobacteria species explained the most variability of MC accumulation, with the rest primarily explained by extraMC-LR. These results indicated that ingestion of MC-producing algae of cyanobacteria accounted for most of the MC that accumulated in T. chinensis. The high MC concentrations in T. chinensis may pose a potential health threat to humans through trophic transfer.


Assuntos
Chironomidae/metabolismo , Microcistinas/metabolismo , Animais , China , Cianobactérias/crescimento & desenvolvimento , Eutrofização , Lagos/química , Lagos/microbiologia , Larva/metabolismo , Estações do Ano , Microbiologia da Água
20.
Environ Sci Pollut Res Int ; 23(18): 18512-23, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27289374

RESUMO

Much attention had been paid to reducing external loading of nutrients to improve water quality, while internal loading from sediment, which has been largely neglected, is also an important source for water eutrophication. The internal load in deep lakes or reservoirs is not easy to be detected and be quantified. In this study, three different methods (mass balance method, Fick's law, and regression equation) were combined to calculate the gross or/and net P release from sediment using limited data. Our results indicated that (1) the methods of mass balance and regression equation give similar results of sediment P release rate, with values of 0.889 and 0.902 mg m(2) d(-1), respectively, while the result of Fick's law was much lower (0.400 mg m(2) d(-1)); (2) Hot periods of sediment releasing were suggested to occur from March to April and from August to September, which correspond to periods of high risks of algae blooms. The remaining months of the year were shown as net nutrient retention; (3) for the whole region, Baihedam and Chaohekuqu were identified as zones with a higher possibility to release P from sediment. (4) P loading to the Miyun Reservoir was greater in the inflow than in the outflow, suggesting a portion of the inflow P load was retained in the water or sediment; hence, release of sediment P may continue to be a major source of phosphorus in the future.


Assuntos
Sedimentos Geológicos/química , Lagos/química , Qualidade da Água , China , Eutrofização
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