Inland Freshwater Environments Research Articles

Impacts of rainfall and lakeshore soil properties on microplastics in inland freshwater: A case study in Donghu Lake, China.

Microplastic (MP) pollution has garnered global attention in recent years. Although anthropogenic factors have been extensively studied for their impacts on MP pollution, there is still a lack of research on the relationship between non-anthropogenic factors and MP occurrence in inland freshwater. This study investigated MP pollution in Donghu Lake, the largest urban freshwater lake in China, to examine the effects of rainfall and lakeshore soil properties on MP pollution. The MP abundance in the surface water of Donghu Lake was 5.84 ± 2.95 items per L under the equilibrium state. However, during and after rainfall, the MP abundances significantly increased to 8.27 ± 5.65 items per L and 7.60 ± 4.04 items per L, respectively (p < 0.05). This increase could be attributed to an increase in the amount of MPs transported to the lake via atmospheric deposition and rainfall runoff, as well as the re-suspension of MP debris in sediment during stronger hydrodynamics. A statistically significant negative correlation was observed between MP abundance and lakeshore soil particle size. It suggested that a high proportion of large-sized soil particles created large pores that enabled MPs to be deposited in the surface layer of soil to migrate to deeper layers. As a result, the amount of MPs in the surface soil and transported to the lake via surface runoff was low. It is of practical significance to understand the sources and distribution impact factors of MPs in urban lakes. The fate and effects of MPs retained in the inland freshwater environments should receive more attention.

Design and optimization of wireless in‐situ sensor coupled with gas–water equilibrators for continuous pCO2 measurement in aquatic environments

AbstractAffordable, highly precise, and accurate CO2 sensor is a prerequisite for more extensive CO2 measurements in various environmental settings, and thus more accurate local and global carbon budgets. Here, we propose the use of an autonomous system for the detection of CO2 concentration (mole fraction), appropriate for inland freshwater and eutrophic coastal environments. We describe the construction of a CO2 sensing device (SIPCO2‐II) using off‐the‐shelf commercial products that integrate wireless communication capability. We also report the proof of concept of two newly designed gas–water equilibrators (GWEs) for in‐situ CO2 monitoring to be used with SIPCO2‐II. The performance of the SIPCO2‐II is evaluated in detail, providing information on the sensor sensitivity, detection limit and stability, and comparing these to a commercially available CO2 analyzer (LGR 915‐0011; Los Gatos Research). Comparison results demonstrate good agreement between the two devices with the root mean square error of 5%. The accuracy and precision of SIPCO2‐II against CO2 reference gases are evaluated and values are within 99–104% recovery and 0.9–3 ppm, respectively. The GWEs which comprised either a semi‐passive floater (free‐drifting float equilibrator; FDFE) or a hybrid showerhead‐marble equilibrator (SME) are tested in the laboratory and in the environment. Overall, the SME outperforms FDFE in terms of response time (4 vs. 16 min). The FDFE can cover larger survey areas with lower cost, due to its semi‐passive feature that allows it to drift with water current. The outcome of our study provides an alternative to budget‐constrained CO2 monitoring regimes without compromising the accuracy and precision of the measurements.

Microplastics in inland freshwater environments with different regional functions: A case study on the Chengdu Plain

As an emerging pollutant, microplastic has been demonstrated to widely cover water and sediments in marine and freshwater environments globally. Due to the differences in the regional functions of cities, the abundance and characteristics of microplastic pollution in rivers are different. Taking the Minjiang River as the research object, which flows through the Chengdu Plain, the abundance, composition, shape, and size of microplastics in the water and sediments of the Minjiang River were investigated. The results showed that serious microplastic pollution occurred in the Chengdu section of the Minjiang River, with an abundance ranging from 6.11–44.08 n/L in the water and from 573.84–2878.97 n/kg in the sediments. By using the “regional function index (Q)”, the relationships between the characteristics of microplastic pollution and regional functions were analyzed. Areas with a high Q proved to be more polluted by microplastics. Densely populated areas with large construction areas and high human activity intensity tended to generate microplastics with larger sizes and a more fiber-like shapes. Rayon (RA) and nylon (PA) were identified as typical urban microplastics, while polypropylene (PP) and polyethylene (PE) were identified as typical agricultural microplastics. This study elucidated the microplastic pollution in the Chengdu section of the Minjiang River, a tributary in the upper reaches of the Yangtze River. It also provided a new direction for the study of microplastic pollution characteristics of freshwater environments with different regional functions and microplastic pollution source control.

Seasonal variation and risk assessment of microplastics in surface water of the Manas River Basin, China

The ubiquity of microplastics in the environment has caused great influence to ecosystems and seriously threatened human health. To better understand the variation in microplastics in different seasons in an inland freshwater environment and determine the sources of microplastic pollution and its migration features, this study investigated the characteristics of microplastic pollution during dry (April) and wet (July) seasons in surface water of the Manas River Basin, China. The size, color, shape, area distribution and compound composition of microplastics were studied. Moreover, the risk of microplastic contamination was explored based on risk assessment models. The results demonstrated that the degree of pollution caused by microplastic abundance was minor in this study area. The average abundance of microplastics in April (17 ± 4 items/L) was higher than that in July (14 ± 2 items/L). The range in the abundance of microplastics in April and July were 22 ± 5–14 ± 3 items/L and 19 ± 2–10 ± 1 items/L, respectively. Highly hazardous polymers such as Polyvinyl chloride (PVC) and Polycarbonate (PC) have a significant impact on the results of the evaluation of the presence of microplastics. This study is an important reference for understanding the characteristics of the seasonal variation in microplastics in inland freshwater environments and has practical significance, as it will allow relevant agencies to accurately assess the pollution level of microplastics in different seasons. It is of practical significance to understand the sources and sinks of microplastics in inland freshwater environment.

Genetic diversity, virulence factors and farm-to-table spread pattern of Vibrio parahaemolyticus food-associated isolates

Vibrio parahaemolyticus is the leading bacterial cause of seafood-associated gastroenteritis worldwide. Moreover, infections and outbreaks caused by V. parahaemolyticus has kept increasing over the last two decades. In this study, we investigated the genetic diversity, virulence factors and farm-to-table spread pattern of V. parahaemolyticus by analyzing 383 genomes of food-associated isolates. These strains were isolated from diverse sample types from six provinces of China in 2014, being classified into three tiers of the farm-to-table spread process: food production, circulation and consumption. The genetic diversity of V. parahaemolyticus in different classifications, including geographical location, sample type, source and spread tier, was similar, as the median number of pairwise SNPs within each classification was between 33,013 and 33,659. Specifically, there was no clear boundaries in genetic diversity of the isolates from inland vs. coastal provinces, as well as of those from freshwater vs. seawater products. Moreover, the virulence genes and genomic islands were only found in a small number of isolates, indicating a low disease risk of the food-associated isolates in this study. By further exploring 28 recently emerged clonal groups, we identified seven farm-to-table spread events, showing a common pattern of single-source radial spread accompanied with occasional gene gain/loss events. Generally speaking, our work highlighted the colonization of V. parahaemolyticus in inland provinces and freshwater environment, and provided a snapshot of the farm-to-table spread pattern of V. parahaemolyticus food-associated isolates. Our results showed the feasibility of tracking the farm-to-table spread of foodborne pathogen, which would help construct the whole genome sequencing-based molecular tracking network in the future.

Molecular Diversity of Cyanopodoviruses in Two Coastal Wetlands in Northeast China.

Although bacteriophages are the most abundant biological entities on the planet, their genetic diversity, especially in natural wetlands, is poorly understood. In this study, the genetic diversity of cyanopodoviruses in sediments of two coastal wetlands in Northeast China was investigated by targeting the DNA polymerase (pol) gene. A total of 66 DNA pol clones were obtained. A BLAST search at the amino acid level showed that the obtained sequences had the highest identity ranged from 83 to 99% to the known sequences. A phylogenetic tree showed that the distribution patterns of DNA pol sequence were different between two wetland soils, and 29 clones of this study formed four wetland-specific groups, which suggested that unrevealed novel groups of cyanopodovirus inhabited in wetlands. In addition, nonmetric multidimensional scaling (NMDS) analysis of all DNA pol sequences from various environments showed that cyanopodovirus communities of coastal wetlands are in the intermediate position between marine water environments and terrestrial freshwater environments, which highlights that the coastal wetlands as transitional zones between inland freshwater environments and marine environments.

Synthetic pyrethroids (Type II) and freshwater fish culture: Perils and mitigations

As a new class of agricultural insecticides, synthetic pyrethroids are widely used to control insect pests. Synthetic pyrethroids have been shown to enter the aquatic environment from agricultural runoff or drift from aerial and ground-based spraying applications posing threat to fishes which are less tolerant to pesticides through direct exposure. These insecticides interfere with the sodium channel of the nervous system resulting in prolonged sodium tail current. Widespread application of these chemicals has warranted the attention of the ecologist to understand the impact of these chemicals on the aquatic environment. In this perspective, an updated account of toxicological evaluation of three type II synthetic pyrethroids, viz. deltamethrin, cypermethrin and fenvalerate in terms of their physico-chemical, metabolic, hematological, histological, behavioral and reproductive aspects with respect to the fishes has been presented which may be useful for policy makers, academics, environmental scientists and agricultural professionals needing ready access to this information. The aim of the present synoptic literature appraisal was to summarize the main effect of current use, type II synthetic pyrethroids (deltamethrin, cypermethrin and fenvalerate) on aquatic environment due to their persistence and accumulation. This article will focus on non-target organisms in inland fresh water environment with special reference to fin fishes and will critically evaluate the toxicity of these pyrethroids in terms of growth inhibition, metabolic disorders, neurotoxicity, reproductive failure, enzymatic dysfunction, haematological alterations, and tissue damages. The rationalized information in this milieu may be useful in ecological risk evaluation and human health management as fish serves as an important bio-indicator for aquatic systems health.

New perspectives on habitat selection by the Black-faced Spoonbill Platalea minor based upon satellite telemetry

SummaryIn 2011 the Black-faced Spoonbill Platalea minor census recorded a 22% drop in numbers from 2010, particularly at the known large coastal wintering sites. During this period, we discovered two new inland wintering sites for the species using satellite telemetry data, one located in China, where the individual followed the Yangtze river as far as Wuhan (500 km inland), and the other across the Vietnam-Cambodia border (70–200 km inland). Long periods of concentrated use of various freshwater habitats were in evidence for these two tagged individuals (China: 79 days, Vietnam/Cambodia: 91 Days) and in the latter case visual confirmation indicated a larger group of at least five individuals. The importance and potential of inland freshwater environments is highlighted towards the further conservation of the recovering population.

Ecosystem Engineering Impact ofLimnoperna fortuneiin South America

Limnoperna fortunei, or golden mussel, has invaded aquatic ecosystems in the Americas following it introduction from Southeast Asia. It is not only an aggressive invasive species, it is also a very effective ecosystem engineer, altering both ecosystem structure and function, and causes great ecological and economic impacts. This paper describes its impact as an ecosystem engineer (on benthic communities and the water column). A review of the existing scientific literature is presented, and the impact and the mechanisms by which the golden mussel modifies, maintains, and creates new environmental conditions in the invaded South American inland freshwater environments are analyzed. Understanding the ecosystem engineering roles of L. fortunei is important for its management and/or control in the invaded areas, and in cases of future invasions.

Potential Impact of Filter-feeding Invaders on Temperate Inland Freshwater Environments

Since the 1990s, biological invasions have captured the attention of the scientific community as an important element of global change and a major threat to biodiversity. The inland waters of South America provide two examples of biological invasions. This review examines bivalve invasions in South America, summarizes the research results for two species, the Asian clam (Corbicula fluminea) and the golden mussel (Limnoperna fortunei), and suggests further studies. The rapid expansion of invasive bivalves into these environments involves significant changes. Until now, C. fluminea, the Asian clam, did not produce generalized macrofouling in the Neotropical region, as is common in the Holarctic region. However, the first specific cases of macrofouling by C. fluminea were recently detected in heat interchangers of power stations in Brazil. On the other hand, L. fortunei is provoking new economic impacts in South American freshwaters through macrofouling. Before the invasion by the golden mussel, macrofouling was recorded only in the marine and estuarine environments of the Neotropical region. The impact caused by invasive bivalves in this region is not only economic, however. Rapid changes in the benthic community, favoring the presence of Oligochaeta and Hirudinea, as well as the displacement of native species of mollusks, are among the problems related to the presence of the golden mussel. Another issue is the settlement of golden mussels on native bivalves. This bivalve is now a new element in the diet of some native fish species, being the main food item in some cases.