Search Results (26)

A growing body of evidence indicates that freshwater bodies, particularly eutrophic systems, are significant sources of the greenhouse gases (GHGs) carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). Unlike marine environments, freshwater systems are generally shallower and more directly influenced by terrestrial inputs, including nutrient enrichment, organic matter deposition, and steep redox gradients in both the water column and sediments. These conditions promote intense phytoplankton growth, including massive harmful cyanobacterial blooms (HCBs), and stimulate microbial processes that drive GHG production and release. This opinion article examines the biogeochemical mechanisms underlying these emissions and evaluates the potential of mitigation treatments to both enhance carbon sequestration and reduce CH₄ and N₂O emissions. We argue that effective control of HCBs, whether through nutrient load reduction or direct mitigation protocols, would not only provide communities with toxin-free water but also significantly lower GHG emissions from eutrophic waterbodies. As this is an opinion paper rather than a comprehensive review, we intentionally avoided citing widely accepted concepts, since doing full justice to the many excellent contributions across all relevant subfields would not be possible within the scope of this work. Full article

The shoreline and seabed topography are key components of the coastal zone and are essential for hydrographic surveys, shoreline process modelling, and coastal infrastructure management. The development of unmanned aerial vehicles (UAVs) and optoelectronic sensors, such as photogrammetric cameras and airborne laser scanning (ALS) using light detection and ranging (LiDAR) technology, has enabled the acquisition of high-resolution bathymetric data with greater accuracy and efficiency than traditional methods using echo sounders on manned vessels. This article presents a spatial analysis of bathymetric data obtained from UAV photogrammetry and ALS LiDAR, focusing on shallow-water depth estimation and shoreline extraction. The study area is Lake Kłodno, an inland waterbody with moderate ecological status. Aerial imagery from the photogrammetric camera was used to model the lake bottom in shallow areas, while the LiDAR point cloud acquired through ALS was used to determine the shoreline. Spatial analysis of support vector regression (SVR)-based bathymetric data showed effective depth estimation down to 1 m, with a reported standard deviation of 0.11 m and accuracy of 0.22 m at the 95% confidence, as reported in previous studies. However, only 44.5% of 1 × 1 m grid cells met the minimum point density threshold recommended by the National Oceanic and Atmospheric Administration (NOAA) (≥5 pts/m²), while 43.7% contained no data. In contrast, ALS LiDAR provided higher and more consistent shoreline coverage, with an average density of 63.26 pts/m², despite 27.6% of grid cells being empty. The modified shoreline extraction method applied to the ALS data achieved a mean positional accuracy of 1.24 m and 3.36 m at the 95% confidence level. The results show that UAV photogrammetry and ALS laser scanning possess distinct yet complementary strengths, making their combined use beneficial for producing more accurate and reliable maps of shallow waters and shorelines. Full article

Fishponds are regarded as hypertrophic systems accompanied by low biodiversity. We focused on the phytoplankton diversity of 15 fishponds located in Austria. Of the 15 fishponds, 12 waterbodies are aquaculture ponds stocked with common carp, which converted to organic farming some years ago with grain as supplementary feed, and 3 ponds are used for recreational fishing. The trophic state index increased from 59 to 71 in spring to 80 to 93 in autumn and classified the ponds as mid-eutrophic to hypertrophic. The taxa number was surprisingly high (taxa richness up to 100 taxa per pond). The phytoplankton resource use efficiency was in the upper range of eutrophicated waters and did not show seasonal differences (median Chlorophyll-a/total phosphorus = 1.94, Chlorophyll-a/total nitrogen = 0.12). Linking environmental data with the algal community resulted in a distinct temporal community pattern with a significant seasonal shift from the cooler season dominated by Ochrophyta taxa to green algae as the most abundant group in summer and autumn. Our findings challenge general assumptions regarding low phytoplankton diversity with long-lasting Cyanobacteria blooms and conform to the algal dynamics described in the plankton ecology group (PEG) model for temperate shallow lakes. These man-made systems are an ecological asset, highly connected to terrestrial habitats in their vicinity and significantly contributing to the ecological health and long-term sustainability of the region. Full article

Internal phosphorus (P) loading is a key driver of waterbody eutrophication. Various sediment P indexes are developed to assess sediment P risks by linking them to water column P, but their seasonal reliability remains underexplored. This study evaluated, for the first time, sediment P status in the Xiashan reservoir, a large shallow reservoir in northern China serving 9.4 million people. The ability of three P indexes, including exchangeable P (Ex-P), Olsen P (Olsen-P), and diluted HCl-extractable P (HCl-P), to predict water column P concentrations was tested across February, May, and August. Sediments in the Xiashan reservoir exhibited moderate total P levels (531–650 mg kg⁻¹) but high P availability, with Ex-P, Olsen-P, and HCl-P in ranges of 19–35, 58–101, and 327–444 mg kg⁻¹, respectively, likely due to sandy composition. Water column P concentrations significantly correlate with August sediment P indexes (r = 0.42–0.81) but not with February and May sediments, highlighting the ability of August sediment P indexes to predict water column P across seasons. Sampling in August is recommended to efficiently identify critical zones for internal P loading, with Ex-P as the preferred indicator given its simple extraction and strong correlation with water column P (r = 0.81). Full article

This technical note aims to present a method for developing a Digital Terrain Model (DTM) of the coastal zone based on topobathymetric data from remote sensors. This research was conducted in the waterbody adjacent to the Vistula Śmiała River mouth in Gdańsk, which is characterised by dynamic changes in its seabed topography. Bathymetric and topographic measurements were conducted using an Unmanned Aerial Vehicle (UAV) and two hydrographic methods (a Single-Beam Echo Sounder (SBES) and a manual survey using a Global Navigation Satellite System (GNSS) Real-Time Kinematic (RTK) receiver). The result of this research was the development of a topobathymetric chart based on data recorded by the above-mentioned sensors. It should be emphasised that bathymetric data for the shallow waterbody (less than 1 m deep) were obtained based on high-resolution photos taken by a UAV. They were processed using the “Depth Prediction” plug-in based on the Support Vector Regression (SVR) algorithm, which was implemented in the QGIS software as part of the INNOBAT project. This plug-in allowed us to generate a dense cloud of depth points for a shallow waterbody. Research has shown that the developed DTM of the coastal zone based on topobathymetric data from remote sensors is characterised by high accuracy of 0.248 m (p = 0.95) and high coverage of the seabed with measurements. Based on the research conducted, it should be concluded that the proposed method for developing a DTM of the coastal zone based on topobathymetric data from remote sensors allows the accuracy requirements provided in the International Hydrographic Organization (IHO) Special Order (depth error ≤ 0.25 m (p = 0.95)) to be met in shallow waterbodies. Full article

The coastal zone is constantly exposed to marine erosion, rising water levels, waves, tides, sea currents, and debris transport. As a result, there are dynamic changes in the coastal zone topography, which may have negative effects on the aquatic environment and humans. Therefore, in order to monitor the changes in landform taking place in the coastal zone, periodic bathymetric and photogrammetric measurements should be carried out in an appropriate manner. The aim of this review is to develop a methodology for performing bathymetric and photogrammetric measurements using an Unmanned Aerial Vehicle (UAV) and an Unmanned Surface Vehicle (USV) in a coastal zone. This publication shows how topographic and bathymetric monitoring should be carried out in this type of zone in order to obtain high-quality data that will be used to develop a Digital Terrain Model (DTM). The methodology for performing photogrammetric surveys with the use of a drone in the coastal zone should consist of four stages: the selection of a UAV, the development of a photogrammetric flight plan, the determination of the georeferencing method for aerial photos, and the specification as to whether there are meteorological conditions in the studied area that enable the implementation of an aerial mission through the use of a UAV. Alternatively, the methodology for performing bathymetric measurements using a USV in the coastal zone should consist of three stages: the selection of a USV, the development of a hydrographic survey plan, and the determination of the measurement conditions in the studied area and whether they enable measurements to be carried out with the use of a USV. As can be seen, the methodology for performing bathymetric and photogrammetric measurements using UAV and USV vehicles in the coastal zone is a complex process and depends on many interacting factors. The correct conduct of the research will affect the accuracy of the obtained measurement results, the basis of which a DTM of the coastal zone is developed. Due to dynamic changes in the coastal zone topography, it is recommended that bathymetric measurements and photogrammetric measurements with the use of UAV and USV vehicles should be carried out simultaneously on the same day, before or after the vegetation period, to enable the accurate measurement of the shallow waterbody depth. Full article

Many compounds produced by cyanobacteria act as serine protease inhibitors, such as the tetrapeptides aeruginosins (Aer), which are found widely distributed. The structural diversity of Aer is intriguingly high. However, the genetic basis of this remains elusive. In this study, we explored the genetic basis of Aer synthesis among the filamentous cyanobacteria Planktothrix spp. In total, 124 strains, isolated from diverse freshwater waterbodies, have been compared regarding variability within Aer biosynthesis genes and the consequences for structural diversity. The high structural variability could be explained by various recombination processes affecting Aer synthesis, above all, the acquisition of accessory enzymes involved in post synthesis modification of the Aer peptide (e.g., halogenases, glycosyltransferases, sulfotransferases) as well as a large-range recombination of Aer biosynthesis genes, probably transferred from the bloom-forming cyanobacterium Microcystis. The Aer structural composition differed between evolutionary Planktothrix lineages, adapted to either shallow or deep waterbodies of the temperate climatic zone. Thus, for the first time among bloom-forming cyanobacteria, chemical diversification of a peptide family related to eco-evolutionary diversification has been described. It is concluded that various Aer peptides resulting from the recombination event act in chemical defense, possibly as a replacement for microcystins. Full article

Atmospheric deposition (AD) is a less understood and quantified source of nutrient loading to waterbodies. AD occurs via settling (large particulates), contact (smaller particulates and gaseous matter), and precipitation (rain, snow) transport pathways. Utah Lake is a shallow eutrophic freshwater lake located in central Utah, USA, with geophysical characteristics that make it particularly susceptible to AD-related nutrient loading. Studies have shown AD to be a significant contributor to the lake’s nutrient budget. This study analyzes nutrient samples from nine locations around the lake and four precipitation gauges over a 6-year study period using three different methods to estimate AD from the precipitation transport pathway. The methods used are simple averaging, Thiessen polygons, and inverse distance weighting, which we use to spatially interpolate point sample data to estimate nutrient lake loads. We hold that the inverse distance weighting method produces the most accurate results. We quantify, present, and compare nutrient loads and nutrient loading rates for total phosphorus (TP), total inorganic nitrogen (TIN), and ortho phosphate (OP) from precipitation events. We compute loading rates for the calendar year (Mg/yr) from each of the three analysis methods along with monthly loading rates where Mg is 10⁶ g. Our estimated annual precipitation AD loads for TP, OP, and TIN are 120.96 Mg/yr (132.97 tons/yr), 60.87 Mg/yr (67.1 tons/yr), and 435 Mg/yr (479.5 tons/yr), respectively. We compare these results with published data on total AD nutrient loads and show that AD from precipitation is a significant nutrient source for Utah Lake, contributing between 25% and 40% of the total AD nutrient load to the lake. Full article

Temperature-dependent chemical toxicity has become a crucial issue taking into consideration that lakes, especially shallow waterbodies, are impacted by climate change worldwide. In this study, we are looking for an answer to what extent standard ecotoxicity assays being performed under constant and relatively low temperatures are capable of predicting the chemical risk posed by pesticides. Lemna minor test plants were exposed to glyphosate in concentrations in the range of 25, 50, 100, 200, and 400 μg/L at temperatures 10, 15, 20, 25, 30, and 35 °C. Two peaks appeared when growth inhibition was assessed; lower concentrations elucidated higher inhibition, at 20 °C, while higher concentrations were found at a higher temperature of 30 °C. The toxic effect experienced at 20 °C indicates that reported PNEC values cannot be sufficient to protect non-target aquatic species in certain environmental scenarios. In addition to growth inhibition, phytotoxicity was also assessed based on peroxidase (POD) concentrations. In general, POD showed greater sensitivity, already showing a response at the lowest temperature tested, 10 °C. Decreased POD activity was detected in the temperature range of 10–30 °C, most probably indicating damage to cell and plasma membranes. Full article

Larval mosquito development is directly impacted by environmental water temperature. Shallow water less than 1 m deep is a common larval mosquito habitat. Existing mathematical models estimate water temperature using meteorological variables, and they range in complexity. We developed a modification of an existing one-layer heat balance model for estimating hourly water temperature and compared its performance with that of a model that uses only air temperature and water volume as inputs and that uses air temperature itself as an indicator of water temperature. These models were assessed against field measurements from a shallow tidal wetland—a known larval habitat—in southwest Western Australia. We also analysed publicly available measurements of air temperature and river height to determine whether they could be used in lieu of field measurements to allow cost-effective long-term monitoring. The average error of the modified version of the heat balance equation was −0.5 °C per hour. Air temperature was the second-best performing method ($\overline{x}$ error = −2.82 °C). The public data sources accurately represented the onsite water temperature measurements. The original heat balance model, which incorporates a parameterisation of evaporative heat flux, performed poorly in hot, dry, windy conditions. The modified model can be used as an input to larval mosquito development models, assisting Local Government Environmental Health officers to determine optimal mosquito development periods and the timing of mosquito monitoring activities to enhance mosquito control. Full article

This research concerns the restoration of the strongly eutrophied Lake Łajskie (Masurian Lake District, Poland) that received pollutants from the agricultural catchment. It is a shallow (max depth 7.4 m) and small (area 48 ha) reservoir with a wide profundal zone characterized by complete deoxidation in summer. Due to its important natural and social role, the lake has undergone a restoration process. Artificial oxygenation is the main method of improving water quality. Due to unfavorable morphometric conditions, the necessity to use multi-point aeration was assumed. An experimental installation based on eight reactors selectively oxygenating only the over-bottom waters was launched in 2019. In 2021, spatial studies of the effectiveness of aerators’ work were carried out at 96 measuring points grouped into 12-test fields around each reactor. The investigations were performed three times during the summer season. It was shown that, in the water of the deepest layers of Lake Łajskie, the oxygen concentration around all reactors increased to an average level of 1–2 mg L⁻¹. The oxygenation efficiency was varied and related to the distance from the aerator and the location in relation to the direction of oxygenated water outflow. The results of the research indicate the legitimacy of designing multi-point oxygenation systems in the restoration of waterbodies degraded as a result of the impact of agriculturally transformed catchments. Full article

Changes in the seafloor relief are particularly noticeable in shallow waterbodies (at depths up to several metres), where they are of significance for human safety and environmental protection, as well as for which the highest measurement accuracy is required. The aim of this publication is to present the integration data model of the bathymetric monitoring system for shallow waterbodies using Unmanned Aerial Vehicles (UAV) and Unmanned Surface Vehicles (USV). As part of this model, three technology components will be created: a hydroacoustic and optoelectronic data integration component proposed by Dąbrowski et al., a radiometric depth determination component based on optoelectronic data using the Support Vector Regression (SVR) method, and a coastline extraction component proposed by Xu et al. Thanks to them, it will be possible to cover the entire area with measurements in the coastal zone, in particular between the shallow waterbody coastline and the min. isobath recorded by the echo sounder (the area is lacking actual measurement data). Multisensor data fusion obtained using Global Navigation Satellite System (GNSS)/Inertial Navigation System (INS), Light Detection And Ranging (LiDAR), Real Time Kinematic (RTK), UAV, and USV will allow to meet the requirements provided for the International Hydrographic Organization (IHO) Special Order (horizontal position error ≤ 2 m (p = 0.95), vertical position error ≤ 0.25 m (p = 0.95)). To this end, bathymetric and photogrammetric measurements shall be carried out under appropriate conditions. The water transparency in the tested waterbody should be at least 2 m. Hydrographic surveys shall be performed in windless weather and the water level is 0 in the Douglas sea scale (no waves or sea currents). However, the mission with the use of an UAV should take place in appropriate meteorological conditions, i.e., no precipitation, windless weather (wind speed not exceeding 6–7 m/s), sunny day. Full article

We aimed to determine the effects of water level and habitat heterogeneity on gastropod fauna in the littoral zone, and the differentiation of functional feeding guilds (FFG) of gastropods. Two periods were analyzed: 2012 (low water level, LWL) and 2013 (high water level, HWL) in the littoral zone of two shallow waterbodies (Sutla backwater, NW Croatia). Waterbody S1, covered with Ceratophyllum demersum, was sampled in the macrophyte stands, and the littoral benthal area, while waterbody S2, without macrophytes, was sampled only in the littoral benthal area. It was observed discovered that among the macrophyte stands in S1, gastropods were significantly more abundant during LWL. The same trend was observed in the littoral benthal area of S2. In contrast, gastropod abundance was higher in the littoral benthal area of S1 during HWL. Comparing gastropods in the two waterbodies, the abundance in S1 was ten times higher than in S2. The most abundant species was Gyraulus parvus, which accounted for 51–92% of the gastropods observed among the macrophytes of S1 and 86% in the adjacent benthic zone. Among the FFG groups, grazers (particularly those feeding on gymnamoebae and rotifers) had the largest proportion, followed by shredders feeding on small pieces of macrophytes. In our research, we indicate the important role of microhabitat diversity and submerged macrophytes as a rich food source for gastropods and safe shelter from predators. Full article

The environmental loss of nitrogen in agricultural landscapes has pervasive consequences, including human health implications, eutrophication, loss of habitat biodiversity and greenhouse gas emissions. The efficacy of mitigation strategies designed to control or prevent nitrate contamination of waterbodies requires an understanding of catchment scale pressures and processes. Groundwater and stream nitrate concentrations fluctuate over temporal scales ranging from the daily to the decadal. Identifying spatiotemporal trends and dominant drivers of nitrate in water is challenging as the drivers are intertwined. The effects of agronomic, meteorological and hydrogeological drivers on groundwater and stream nitrate were investigated over seven years in two well-drained agricultural catchments, dominated by tillage and grassland farming, respectively. A significant positive temporal trend in nitrate concentration was observed in the tillage catchment, whereas no long-term trend was observed in the grassland catchment. Agronomic, meteorological and hydrogeological factors were significantly related to temporal nitrate changes across both catchments. Clearly identifying the drivers influencing temporal changes in nitrate concentrations is critical to improving water quality. The study highlighted that to reduce groundwater nitrate levels in areas of high risk (thin soils, low clay content and shallow groundwater), nitrogen applications need to be reduced and/or tailored, particularly at times of restricted crop growth. Full article

Hydrographic surveys enable the acquisition and processing of bathymetric data, which after being plotted onto nautical charts, can help to ensure safety of navigation, monitor changes in the coastal zone, and assess hydro-engineering structure conditions. This study involves the measurement of waterbody depth, identification of the seabed shape and geomorphology, the coastline course, and the location of underwater obstacles. Hydroacoustic systems mounted on vessels are commonly used in bathymetric measurements. However, there is also an increasing use of Unmanned Aerial Vehicles (UAV) that can employ sensors such as LiDAR (Light Detection And Ranging) or cameras previously not applied in hydrography. Current systems based on photogrammetric and remote sensing methods enable the determination of shallow waterbody depth with no human intervention and, thus, significantly reduce the duration of measurements, especially when surveying large waterbodies. The aim of this publication is to present and compare methods for determining shallow waterbody depths based on an analysis of images taken by UAVs. The perspective demonstrates that photogrammetric techniques based on the SfM (Structure-from-Motion) and MVS (Multi-View Stereo) method allow high accuracies of depth measurements to be obtained. Errors due to the phenomenon of water-wave refraction remain the main limitation of these techniques. It was also proven that image processing based on the SfM-MVS method can be effectively combined with other measurement methods that enable the experimental determination of the parameters of signal propagation in water. The publication also points out that the Lyzenga, Satellite-Derived Bathymetry (SDB), and Stumpf methods allow satisfactory depth measurement results to be obtained. However, they require further testing, as do methods using the optical wave propagation properties. Full article