Editorial

3 pages, 152 KiB

Open AccessEditorial

Interaction among Hydrological, Environmental, and Ecological Processes in Aquatic Ecosystems

by Xin’an Yin, Xufeng Mao, Jianguo Zhou and Zhengjian Yang

Water 2021, 13(23), 3389; https://doi.org/10.3390/w13233389 - 01 Dec 2021

Cited by 1 | Viewed by 1273

In the context of climate change and human disturbance, the hydrological and environmental processes in aquatic ecosystems have undergone significant changes, which could affect the material cycle and energy conversion processes required by aquatic organisms to maintain life [...] Full article

(This article belongs to the Special Issue Interaction among Hydrological, Environmental and Ecological Processes in Aquatic Ecosystems)

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16 pages, 2421 KiB

Open AccessArticle

A Coupled Sampling Design for Parameter Estimation in Microalgae Growth Experiment: Maximizing the Benefits of Uniform and Non-Uniform Sampling

by Hao Li and Enze Zhang

Water 2021, 13(21), 2996; https://doi.org/10.3390/w13212996 - 24 Oct 2021

Cited by 2 | Viewed by 1817

Abstract

As an important primary producer in aquatic ecosystems, the various parameters within the mathematical models are used to describe the growth of microalgae and need to be estimated by carefully designed experiments. Non-uniform sampling has proved to generate a deliberately optimized sampling temporal [...] Read more.

As an important primary producer in aquatic ecosystems, the various parameters within the mathematical models are used to describe the growth of microalgae and need to be estimated by carefully designed experiments. Non-uniform sampling has proved to generate a deliberately optimized sampling temporal schedule that can benefit parameter estimation. However, the current non-uniform sampling method depends on prior knowledge of the nominal values of the model parameters. It also largely ignores the uncertainty associated with the nominal values, thus inducing unacceptable parameter estimates. This study focuses on the uncertainty problem and describes a new sampling design that couples the traditional uniform and non-uniform sampling schedules to benefit from the merits of both methods. Based on D-optimal design, we first derive the non-uniform optimal sampling points by maximizing the determinant of the Fisher information matrix. Then the confidence interval around the non-uniform sampling points is determined by Monte Carlo simulations based on the prior knowledge of parameter distribution. Finally, we wrap the non-uniform sampling points with the uniform sampling points within the confidence interval to obtain the ultimate optimal experimental design. Scenedesmus obliquus, whose growth curve follows a four-parameter model, was used as a case study. Compared with the traditional sampling design, the simulation results show that our proposed coupled sampling schedule can partly eliminate the uncertainty in parameter estimates caused by fixed systematic errors in observations. Our coupled sampling can also retain some advantages belonging to non-uniform sampling, in exploiting information maximization and managing the cost of sampling. Full article

(This article belongs to the Special Issue Interaction among Hydrological, Environmental and Ecological Processes in Aquatic Ecosystems)

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14 pages, 2173 KiB

Open AccessArticle

Comparative Use of Hydrologic Indicators to Determine the Effects of Flow Regimes on Water Quality in Three Channels across Southern Florida, USA

by Ikechukwu S. Onwuka, Leonard J. Scinto and Ali Mahdavi Mazdeh

Water 2021, 13(16), 2184; https://doi.org/10.3390/w13162184 - 10 Aug 2021

Cited by 4 | Viewed by 3432

Abstract

This study determines the relationships between water flow and water quality in three types of channels in southern Florida, USA: Shark River Slough, Peace River, and Hillsboro Canal. Peace River most resembles a natural channel with floodplain connectivity, sinuosity, and uninhibited flow. Shark [...] Read more.

This study determines the relationships between water flow and water quality in three types of channels in southern Florida, USA: Shark River Slough, Peace River, and Hillsboro Canal. Peace River most resembles a natural channel with floodplain connectivity, sinuosity, and uninhibited flow. Shark River Slough has a natural, shallow channel with sheet flow, while the Hillsboro Canal is the most modified channel due to dredging, straightening, and regulated flow. Hydrologic indices for each channel were estimated to characterize flow regimes and flow variability, while concentration–discharge (C–Q) relationships were determined to quantify the impact of flow regime on water quality. The greatest variability in flow occurred at the Hillsboro Canal, followed by Peace River and Shark River Slough. Connectivity to floodplains and long durations of low and high flow pulses at Peace River and Shark River Slough contributed to the dilution of water quality constituent concentrations at higher flows. Conversely, the channelized characteristics of the Hillsboro Canal resulted in an enrichment of constituents, especially during high flows. This study suggests that C–Q relationships can be used in canal discharge management to prevent water quality degradation of sensitive downstream wetland and aquatic ecosystems. Full article

(This article belongs to the Special Issue Interaction among Hydrological, Environmental and Ecological Processes in Aquatic Ecosystems)

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15 pages, 4108 KiB

Open AccessFeature PaperArticle

Levels, Inventory, and Risk Assessment of Heavy Metals in Wetland Ecosystem, Northeast China: Implications for Snow Cover Monitoring

by Fuxiang Zhang, Bo Meng, Shang Gao, Rupert Hough, Peng Hu, Zulin Zhang, Shaopeng Yu, Kunyang Li, Zhikun Liu and Song Cui

Water 2021, 13(16), 2161; https://doi.org/10.3390/w13162161 - 06 Aug 2021

Cited by 8 | Viewed by 2009

Abstract

Snow cover is a unique environmental medium in cold regions that can cause potential risks to the ecological environment, due to the release of pollutants that are stored in it. In this study, the Qixing River wetland, located in the Sanjiang Plain of [...] Read more.

Snow cover is a unique environmental medium in cold regions that can cause potential risks to the ecological environment, due to the release of pollutants that are stored in it. In this study, the Qixing River wetland, located in the Sanjiang Plain of China, was taken as the target research area. Heavy metals in snow cover, including Cu, Ni, Cr, Cd, Pb, and Zn were measured at 19 sampling sites. The results showed that the average concentrations of heavy metals were: Zn (103.46 ± 39.16) > Pb (13.08 ± 4.99) > Cr (11.97 ± 2.82) > Ni (9.55 ± 4.96) > Cu (6.19 ± 1.79) > Cd (0.55 ± 0.25) μg·L⁻¹. Cr and Zn were between Class I and Class II in the “Environmental Quality Standards for Surface Water” of China (GB3838-2002). Pb in snow exceeded the upper limit of Class II, and was significantly higher than concentrations measured in water samples from the Qixing River wetland (p < 0.05), indicating that atmospheric deposition during winter was the major source of Pb. The water pollution index (WPI) indicated that 61.0% of samples could be considered of “clean” status, while the contribution of Zn, Pb, and Cr to WPI were 33.3%, 21.0%, and 19.3%, respectively. A preliminary evaluation of heavy metal inventory in snow cover showed that the residue level of Zn was the highest (2313.57 ± 1194.67 μg·m⁻²), while Cd was the lowest (13.91 ± 10.45 μg·m⁻²). The areas with high residues of heavy metals were all located near the buffer zone of the wetland (except for Zn), where snow depth tended to be greatest. Exposure analysis indicated that the risks to winter resident birds from snow ingestion was minimal, but it should be noted that the exposure risk was higher in birds with lower bodyweights. This study provides important information and scientific knowledge on the pollution characteristics and residue inventory of heavy metals in wetland ecosystems, while the results can also provide a monitoring method, reflecting atmospheric environmental quality at a local or regional scale. Full article

(This article belongs to the Special Issue Interaction among Hydrological, Environmental and Ecological Processes in Aquatic Ecosystems)

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23 pages, 6163 KiB

Open AccessArticle

Dependence of Long-Term Dynamics of Zooplankton in the Ob River on Interannual Changes in Hydrological and Hydrochemical Parameters

by Nadezhda Yermolaeva, Serafima Dvurechenskaya, Vladimir Kirillov and Aleksandr Puzanov

Water 2021, 13(14), 1910; https://doi.org/10.3390/w13141910 - 09 Jul 2021

Cited by 6 | Viewed by 2784

Abstract

Here we summarize a long-term study on qualitative and quantitative composition of zooplankton (Cladocera, Copepoda, Rotifera) in the Ob River. We carried out these investigations at 13 sampling stations of the Middle and Low Ob in the years 1994, 1996, 1999, 2001, 2002 [...] Read more.

Here we summarize a long-term study on qualitative and quantitative composition of zooplankton (Cladocera, Copepoda, Rotifera) in the Ob River. We carried out these investigations at 13 sampling stations of the Middle and Low Ob in the years 1994, 1996, 1999, 2001, 2002 and 2009. It was found that the species richness of all zooplankton and abundance of cladocerans and rotifers is significantly determined by the temperature conditions of the month preceding sampling. In contrast, among other factors, we revealed that pH decreases as well as phosphate and nitrate concentrations increase zooplankton abundance. Dissolved oxygen and oxidizable organic substances (BOD₅) were positively correlated to copepod population levels (according to abundance and biomass); on the other hand, an increase in difficult-to-oxidize substances (COD) inhibited their development. During this study, we found that high water levels had a positive influence on zooplankton richness in river itself probably due to being downstream from Ob River floodplain lakes. Full article

(This article belongs to the Special Issue Interaction among Hydrological, Environmental and Ecological Processes in Aquatic Ecosystems)

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21 pages, 3476 KiB

Open AccessFeature PaperArticle

Grading Evaluation of the Structural Connectivity of River System Networks Based on Ecological Functions, and a Case Study of the Baiyangdian Wetland, China

by Kai Tian, Xin-an Yin, Jie Bai, Wei Yang and Yan-wei Zhao

Water 2021, 13(13), 1775; https://doi.org/10.3390/w13131775 - 27 Jun 2021

Cited by 5 | Viewed by 2248

Abstract

River system network (RSN) connectivity is important to maintain the environmental and ecological functions of wetlands. Quantitative evaluation of connectivity can provide crucial support for efforts to improve wetland connectivity and to restore and protect wetland ecosystems. Most existing evaluation methods uniformly generalise [...] Read more.

River system network (RSN) connectivity is important to maintain the environmental and ecological functions of wetlands. Quantitative evaluation of connectivity can provide crucial support for efforts to improve wetland connectivity and to restore and protect wetland ecosystems. Most existing evaluation methods uniformly generalise RSN to form an undifferentiated RSN of edges and nodes that is taken as a whole to evaluate the connectivity. However, actual RSNs comprise rivers, canals, ditches, lakes, and ponds, which differ substantially in their structures, morphologies, and attributes. The mix of RSN elements therefore defines grades that give RSNs distinctive characteristics. Moreover, RSNs with different grades perform different ranges of environmental and ecological functions. The existing evaluation methods, which have some limitations, do not account for these characteristics. To account for these differences, we examined the grade characteristics and their impact on environmental and ecological functions. We established a grading system of RSN elements and a grading method of RSN, and constructed the structural connectivity evaluation indicator system for RSNs at different grades. On this basis, we propose a method for grading evaluation of RSN connectivity. We used China’s Baiyangdian Wetland to demonstrate the use of the system and validate the results. The proposed method provided an objective and accurate evaluation of RSN connectivity and clarified the differences in connectivity among RSNs with different grades, thereby providing improved guidance for the development and maintenance of the environmental and ecological functions of RSNs. Full article

(This article belongs to the Special Issue Interaction among Hydrological, Environmental and Ecological Processes in Aquatic Ecosystems)

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13 pages, 2118 KiB

Open AccessArticle

A Method for Estimating the Velocity at Which Anaerobic Metabolism Begins in Swimming Fish

by Feifei He, Xiaogang Wang, Yun Li, Yiqun Hou, Qiubao Zou and Dengle Shen

Water 2021, 13(10), 1430; https://doi.org/10.3390/w13101430 - 20 May 2021

Cited by 2 | Viewed by 2856

Abstract

Anaerobic metabolism begins before fish reach their critical swimming speed. Anaerobic metabolism affects the swimming ability of fish, which is not conducive to their upward tracking. The initiation of anaerobic metabolism therefore provides a better predictor of flow barriers than critical swimming speed. [...] Read more.

Anaerobic metabolism begins before fish reach their critical swimming speed. Anaerobic metabolism affects the swimming ability of fish, which is not conducive to their upward tracking. The initiation of anaerobic metabolism therefore provides a better predictor of flow barriers than critical swimming speed. To estimate the anaerobic element of metabolism for swimming fish, the respiratory metabolism and swimming performance of adult crucian carp (Carassius auratus, mass = 260.10 ± 7.93, body length = 19.32 ± 0.24) were tested in a closed tank at 20 ± 1 °C. The swimming behavior and rate of oxygen consumption of these carp were recorded at various swimming speeds. Results indicate (1) The critical swimming speed of the crucian carp was 0.85 ± 0.032 m/s (4.40 ± 0.16 BL/s). (2) When a power function was fitted to the data, oxygen consumption, as a function of swimming speed, was determined to be AMR = 131.24 + 461.26U_s^1.27 (R² = 0.948, p < 0.001) and the power value (1.27) of U_s indicated high swimming efficiency. (3) Increased swimming speed led to increases in the tail beat frequency. (4) Swimming costs were calculated via rate of oxygen consumption and hydrodynamic modeling. Then, the drag coefficient of the crucian carp during swimming was calibrated (0.126–0.140), and the velocity at which anaerobic metabolism was initiated was estimated (0.52 m/s), via the new method described herein. This study adds to our understanding of the metabolic patterns of fish at different swimming speeds. Full article

(This article belongs to the Special Issue Interaction among Hydrological, Environmental and Ecological Processes in Aquatic Ecosystems)

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13 pages, 3561 KiB

Open AccessFeature PaperArticle

Temporal and Spatial Characteristics of CO₂ Flux in Plateau Urban Wetlands and Their Influencing Factors Based on Eddy Covariance Technique

by Yi Wu, Xufeng Mao, Zhifa Zhang, Wenjia Tang, Guangchao Cao, Huakun Zhou, Jianhai Ma and Xinan Yin

Water 2021, 13(9), 1176; https://doi.org/10.3390/w13091176 - 24 Apr 2021

Cited by 7 | Viewed by 2357

Abstract

Urban wetlands, an important part of the urban ecosystem, play an important role in regional carbon cycles and the carbon balance. To analyze the CO₂ source and sink effects of plateau urban wetlands, based on the data measured by an eddy covariance [...] Read more.

Urban wetlands, an important part of the urban ecosystem, play an important role in regional carbon cycles and the carbon balance. To analyze the CO₂ source and sink effects of plateau urban wetlands, based on the data measured by an eddy covariance instrument, the temporal and spatial characteristics of CO₂ flux and their influencing factors in the urban wetland of Xining City in the Qinghai Province of China during a warm season (July to September 2020) were studied. The results show that: (1) On the daily scale, the CO₂ flux exhibited an obvious “U”-type variation, characterized by strong uptake in the daytime and weak emission at night, with an average daily flux of −0.05 mg·m⁻²·s⁻¹. The CO₂ uptake peak of the wetland took place at 13:00 (−0.62 mg·m⁻²·s⁻¹), and the emission peak occurred at 23:30 (0.34 mg·m⁻²·s⁻¹); (2) on the monthly scale, the CO₂ flux of the wetland in the study period showed a net uptake each month. The flux increased month by month, and the maximum value occurred in September (−142.82 g·m⁻²·month⁻¹); (3) from a spatial point of view, the river area showed a weak CO₂ uptake (−0.07 ± 0.03 mg·m⁻²·s⁻¹), while the artificial wetland area showed a strong CO₂ uptake (−0.14 ± 0.03 mg·m⁻²·s⁻¹). The former was significantly lower than the latter (p < 0.01); (4) the regression analysis results show that the CO₂ flux was significantly correlated with PAR, VPD, T_soil, and SWC (p < 0.01). The relationships between the flux and PAR, T_soil, and SWC were rectangular hyperbola (y = 0.2304 − 2 × 10⁻³x/(0.9037 + 0.0022x), R² = 0.64), exponential (y = 0.046exp(0.091x), R² = 0.88), and quadratic (y = −0.0041x² + 0.1784x − 1.6946, R² = 0.83), respectively. Under the joint action of various environmental factors, the urban wetland ecosystem in plateau displayed a strong carbon sink function in warm seasons. This study can establish a data scaffold for the accurate estimation of carbon budget of this type of ecosystem. Full article

(This article belongs to the Special Issue Interaction among Hydrological, Environmental and Ecological Processes in Aquatic Ecosystems)

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