Emergent Aquatic Vegetation Research Articles

Mapping the dynamics of aquatic vegetation in Lake Kyoga and its linkages to satellite lakes

Lake Kyoga is a shallow, young, flooded basin just north of and about 30m lower than Lake Victoria. The catchment encompasses Lake Kyoga itself, and a constellation of several dozen small satellite lakes following valley contours mostly to its east. The Kyoga basin fish fauna shares many non-cichlid species plus a spectacular, partially endemic radiation of haplochromine cichlids most similar to but still largely distinct from those in Lake Victoria. This fish fauna is of high conservation concern, as it preserves remnants of the regional species flock that have disappeared from Lake Victoria and Lake Kyoga, leaving small remnant populations in some of the satellite lakes. Now, these too are imperiled by limnological dynamics, including fluctuations in the nature and extent of aquatic vegetation. The water bodies in the Kyoga Basin are highly dynamic due both to fluctuation in water level and large amplitude variation in marginal and floating vegetation. This variation has profound evolutionary and conservation implications, since it can create and destroy critical aquatic habitat. It can also alternately anneal and cleave gene flow over time, both between the main lake and its satellites, and among the satellite lakes. The aquatic vegetation cluttering these linkages can create a spatial refugium for many native fish species that are more tolerant of hypoxia than an introduced macropredator, the Nile perch. Anthropogenic impacts to this region have greatly increased in recent years, altering relationships between aquatic vegetation and endangered species, fisheries and other ecosystem services provided by the lake. Understanding these dynamics require a means of mapping aquatic vegetation, connectivity, and habitat through time. Here we develop a new and improved algorithm to map the spatial distribution and dynamics of floating and emergent aquatic vegetation via remote sensing. We utilize a time series of 440 Landsat images dating from 1986 to 2020. A series of water and vegetation indices are designed to reveal change in the aquascape over time. First, two types of water masks are derived using a majority rule - a separate water mask for each image and a composite water mask of the region over the study period. Second, the difference between the two masks is then used to delineate the potential location of macrophytes over the image. Third, an algorithm is developed to separate the floating vegetation from emergent vegetation; this algorithm uses Landsat spectral bands and two additional spatial and temporal metrics that considerably improve classification accuracy. A more extensive analysis of aquascape trajectories using remote sensing can inform fish conservation strategies and fisheries management and illuminate the role of landscape dynamics in macroevolutionary patterns of aquatic taxa.

Drag in Vegetation Canopy: Considering Sheltering and Blockage Effects

AbstractVegetation plays a crucial role in river hydrodynamic processes, and the accurate prediction of canopy drag force is essential for effective river management and ecosystem protection. The interactions within the vegetation canopies must be quantified to understand their impact on drag force. Through a series of flume experiments, we conducted an investigation into the canopy interaction mechanism of rigid emergent aquatic vegetation, particularly focusing on the blockage and sheltering effects. Our experimental design includes various combinations of lateral and longitudinal spacing, as well as special single‐row and single‐column arrangements. This allowed us to provide a more precise understanding of how lateral and longitudinal spacing affect the blockage and sheltering effects. Furthermore, we introduced a unified reference velocity that combines two effects, based on which we have established a widely applicable drag model that can predict drag under various density conditions. Lastly, we proposed a critical characteristic value for quantifying drag. This value is instrumental in revealing the ultimate performance of drag under different spacing arrangements. The findings provide a reliable approach for predicting drag in rigid emergent vegetation canopies, significantly enhancing our understanding of vegetation's influence on hydrodynamic processes and offering a practical tool for river management and ecosystem protection.

Loess chronology and composition as interpreted through the lens of fossiliferous lake sediments in central Illinois, USA

Silty lacustrine and paludal records spanning from the penultimate deglaciation (late Illinois Episode) to the present are preserved in kettles formed during marine isotope stage (MIS) 6 that lie adjacent to the MIS 2 Manito terrace along the valleys of the Sangamon and Illinois Rivers. Geochemical, mineralogical, particle-size, and chronological records from two basins, Smith Lake and Lake Ben, provide a unique opportunity to assess loess age and provenance of the south-central Laurentide ice sheet. Here, I focused on deposits of redeposited loess of the last glaciation (Wisconsin Episode). Other than subtle laminations and fossils of emergent and aquatic plants and animals, the silty texture, chemical composition, and mineralogy of the lake sediment closely resemble Peoria Silt (loess). Sediment-core records sampled from Smith Lake and Lake Ben in Mason County, Illinois, confirm rapid deposition of proximal loess derived from the nearby outwash plain of the Illinois River from ca. 30.9−18.0 calibrated (cal) k.y. B.P. From 18.0−14.7 cal k.y. B.P., deposition of proximal loess was gradually replaced by far-traveled (distal) loess chiefly derived from Superior lobe provenance and global dust. The succession is capped by a cumulic gleysol that was truncated by recent plowing. Proximal loess deposits in lakes Smith and Ben are composed primarily of very fine sand, coarse silt, and medium silt (125−16 µm) compared to the distal facies (fine silt and finer sediment: <16 µm). Proximal loess that originated from outwash of the Lake Michigan lobe contains abundant Ca, Zr, Sr, illite, and magnetic minerals. The distal facies contains relatively abundant Rb, Al, K, Si, Cu, and Pb, and it is enriched in smectite (relative to illite) and depleted in magnetic minerals. Radiocarbon ages on terrestrial gastropod aragonite in loess from the nearby New Cottonwood School and Thomas Quarry sites indicate that Peoria Silt deposition ended between 18 cal k.y. B.P. and 16 cal k.y. B.P. At these localities, the upper part of the record is complicated by the modern soil, which has altered soil organic matter and leached carbonate. At Lake Ben, the radiocarbon record of emergent aquatic vegetation indicates that sediment accumulation rates and the ratio of proximal to distal loess decreased at the correlative interval that yielded the youngest snail shell ages at Cottonwood School. The upward increase in element concentrations such as Al and decrease in coarse/fine silt ratios in the modern soil are prominent features in the Lake Ben record dating from 18−14 cal k.y. B.P. This correlation strongly suggests that many of the features of the modern soil were not developed into uniform parent material but, rather, were inherited from incremental addition of distal loess to proximal loess, collectively identified as Peoria Silt. The paucity of key elements (Cd, Hg, Se, Ag, Au) in this transition zone suggests limited contributions from western lobes (i.e., Des Moines and James lobes), but abundant Ti and Cu suggest a contribution from the Superior lobe. A new wrinkle in this interpretation is that the rise in elements such as Al, Rb, and Si suggests significant additions from generic dust from unknown sources.

Influence of vegetation on soil organic nitrogen composition and mineralization in a subtropical wetland

Studies have investigated the role of litter type on soil organic nitrogen (SON) mineralization and the resulting chemical composition in aerobic soils; however, the role of anaerobic conditions have been limitedly explored. We determined the SON chemical composition and N mineralization rate with depth of two different vegetation types (emergent aquatic vegetation, EAV and submerged aquatic vegetation, SAV) and prevailing flooded soil conditions in a subtropical treatment wetland. The treatment wetland provided similar water quality and climate conditions across the vegetation types. Three soil depths were sampled, the surficial floc, recently accreted soil, and soil present before constructing the treatment wetland. The surficial floc material created from emergent plants exhibited a mean total carbon (TC) and total N (TN) of 364 g C kg−1 and 27 g N kg−1 vs 185 g C kg−1and 12 g N kg−1 for submerged plants. Despite these differences, there were no significant differences in the proportion of N that was soil organic nitrogen (SON). Mean extractable ammonium was lower (95 mg N kg−1) in SAV systems and may be due to increased pH (~9) during the day compared to EAV systems (207 mg N kg−1). For the chemical composition, the N-associated aromatics comprised 4.8% of the SON in SAV areas compared with just 1.6% for EAV, which suggests an increased SON recalcitrance in SAV created floc. The difference in EAV and SAV chemical composition may be important for the long-term storage of SON and future studies should focus on additional environmental factors that favor the formation of stable recalcitrant SON.

Processes Towards Sedimentation around a Reed Island in a Shallow Lake

There are many studies on the hydromorphological impacts of emergent aquatic vegetation, but many of these focus on gravity-driven flows in riverine or tidal environments. However, an added effect of emergent vegetation in lakes is that it reduces the main external force (wind) significantly and in a spatially coherent way. We performed long Monte Carlo simulations using a 2D hydrodynamic model and a spectral wind wave model to study resuspension dynamics around a 100-m-wide reed island in southern Lake Fertő/Neusiedl. Wave-current interaction, computed in a post-processing step, was found to enhance maximum bed shear stresses only on the leeward side of the reed island, and even there to a small extent. We have found evidence that the present bed topography is close to an equilibrium where simulated combined wave-current shear stresses have a reasonably uniform exceedance probability over the critical shear stress of the bed sediment. We also found that an artificially flattened lakebed around the reed island would start evolving towards the present bed topography and grain size distribution (both of which were surveyed in the field). Despite the limitations of our modelling framework, our results illustrate the importance of how wind climate is translated to an uneven distribution of sediment entrainment around the reed island, explaining tendencies of sediment accumulation and sorting. Our results lead to a better understanding of the complicated processes involving interaction among wind, vegetation, circulation, wind waves, sediment and bathymetry.

Biogeochemical response of subtropical treatment wetlands to different flow conditions

The biogeochemical response to different flow conditions within two parallel, well-performing flow-ways (FWs) in Everglades Stormwater Treatment Area (STA)-2 was studied. Three flow events in FW1, an emergent aquatic vegetation (EAV) based system and three flow events in FW3, a submerged aquatic vegetation (SAV) dominated system, were carried out between August 2015 and July 2017. These flow events included either low or moderate flow that was preceded and/or followed by no flow. These flow scenarios were designed to simulate different hydraulic and hydrologic conditions that STAs experience during full-scale operations. Hydraulic loading rates (HLRs, flow volume per day/wetland effective treatment area) during the flow events ranged from 0.5 to 10.4 cm d−1 with resulting phosphorus loading rates (PLRs, daily load/wetland effective treatment rate) of 1 to 20 mg P m−2 d−1. The ability of these flow-ways to remove and transform P in the water column under different flow conditions was evaluated using water quality data from autosamplers and weekly grab samples collected at six monitoring stations along each flow-way.Distinct water column concentration gradients of total phosphorus (TP) from inflow to outflow at all phases of the flow events for both flow-ways were observed. The magnitude at which P is removed from the water column increased with fractional distance from the inflow and was greater for the EAV-dominated system (FW1) than the SAV-based system (FW3). This system response translated to higher TP concentration reduction in EAV than SAV. Inflow to outflow TP concentration reductions for EAV were 94, 88, and 86% for moderate (MF), low (LF), and no flow (NF), respectively. For SAV, TP concentration reductions were 73, 71, and 64% for MF, LF, and NF, respectively. A significant increase in TP concentrations [largely dissolved organic P (DOP) and particulate P (PP)] in the SAV-dominated system was observed under no flow condition. The increase was attributed to in-situ production of PP through several mechanisms that likely include phytoplankton growth, periphyton sloughing, litter fragmentation, and resuspension via entrainment or bioturbation. While soluble reactive P (SRP) was the dominant form of inflow TP removed along the EAV FW, PP accounted for most of the reduction in TP concentration along the SAV FW, under both flow and no flow conditions. Particulate P and DOP comprised the residual P pool at the outflow region of each FW with slightly higher concentrations in the SAV than the EAV FW under no flow condition. The removal of P from the water column in the EAV FW was largely attributed to biotic processes (i.e., P uptake by biota) while coupled biotic and abiotic processes regulated P reduction in the SAV FW.

Seasonal and spatial patterns of surface water quality in large-scale treatment wetlands with different vegetation communities

The Everglades Stormwater Treatment Areas (STAs), a network of large, constructed wetlands, were built to reduce phosphorus (P) in water discharged into downstream oligotrophic Everglades ecosystem. These wetlands are colonized by two main types of macrophyte communities: emergent aquatic vegetation (EAV) and submerged aquatic vegetation (SAV). The objective of this study was to compare the seasonal and spatial patterns of surface water quality within two flow-ways (FWs) in STA-2 (FW1 dominated by EAV and FW3 a mixed marsh with both EAV and SAV) and assess how surface water quality was affected by extreme storm events. Surface water samples were collected from three stations (near the inflow, middle of the FW, and near the outflow) along the flowpath of each FW four times from 2016 to 2018. Total P and its fractions generally decreased along the flowpath in both FWs while other elements did not show a consistent trend between seasons. Surface water quality in FW1 had more evident seasonal patterns and was less affected by 2017 storm events compared to that of FW3. The changes and patterns of water quality indicate that the processes (e.g., plant nutrient uptake, microbial assimilation, detritus decomposition and particle settling, etc.), which take the primary role of removing nutrients from the water column in FW1, vary not only due to the differences in plant growth but also to variations of hydraulic and nutrient loadings over wet and dry seasons. In FW3, on the contrary, our results indicate that the occlusion process facilitated by underwater photosynthesis of SAV likely enhanced the capacity of removing P and associated elements from water column and attenuated the seasonal differences. The SAV in FW3 also was susceptible to extreme events, with both short- and long-term adverse effects of storm events on surface water quality.

Biomass and nutrient storage of aquatic plants along phosphorus gradients in everglades stormwater treatment areas

The Everglades Stormwater Treatment Areas (STAs) are large freshwater wetlands constructed to reduce phosphorus (P) in stormwater runoff discharged to the Everglades Protection Area. The STAs consist of compartmentalized flow-ways (FWs) containing one or more treatment cells, which are managed to promote either emergent aquatic vegetation (EAV) or a mixed marsh of EAV and submerged aquatic vegetation (SAV). This study evaluated biomass, nutrient content, and nutrient storage of common EAV (Typha spp.) and SAV (Chara spp.) species within well performing STA FWs (i.e., P discharges below 20 μg/L). Samples for both vegetation types were collected at inflow, midflow, and outflow locations. Typha samples were partitioned into aboveground and belowground components. All samples were analyzed for biomass, P, nitrogen (N), and carbon. Content (g kg−1) of P and N in Typha were significantly higher in belowground components compared to aboveground for all sites, while storage (g m−2) of P and N was highest at inflow sites compared to midflow and outflow sites. In Chara, P and N content were significantly higher at some midflow sites relative to outflow sites. The ratio of N:P (based on mass storage) typically increased from inflow to outflow, though ratios at most Typha sites indicated N limitation while P limitation was observed primarily at Chara dominated outflow sites. Typha nutrient storage measured in the present study was comparable to storages within floc and recently accreted soil layers measured during concurrent studies, indicating that Typha represents a significant pool of P within the STAs. Evaluations conducted here represent recent in situ biomass and nutrient storages for the most common STA vegetation, which have not been documented thoroughly since early in STA operation, and support ongoing STA biogeochemical modeling efforts.

Distribution of emergent aquatic vegetation leaf inclination angle and its simulation

Leaf normal inclination angle distribution (LAD) determines the interception of radiation by leaves and the transmission of radiation by the vegetation canopy, which affects the distribution of incident photosynthetically active radiation on plant leaves and ultimately directly affects the net primary productivity of vegetation. However, the contact measurement method for leaf inclination angle is difficult to perform due to the complex growing environment of wetland aquatic vegetation. In this study, the method of measuring normal leaf inclination angles was improved for wetland aquatic vegetation based on horizontal digital photography combined with the application of a protractor. Phragmites australis and Typha orientalis, two typical emergent aquatic vegetation (EAV) species growing in wetlands, were used to evaluate the robustness of leaf inclination measurement methods. In addition, LAD values were measured and analyzed for their variations across seasonal and vertical gradients within the canopy. Finally, the applicability of the two simulation algorithms for leaf normal inclination was evaluated and compared. Analysis revealed that Phragmites australis LAD exhibited a variation with seasonal changes and vertical canopy height, which is beneficial for light transmission within the canopy. The LAD of Typha orientalis was always an erectophile pattern and changed only slightly with the seasons. The new findings provided additional insights and evidence on aquatic plant resistance and environmental adaptation. Comparing simulation models for EAV, the trigonometric algorithm outperforms other algorithms in accuracy and deviation. The results of this research provide a valuable reference for exploring radiation transfer within aquatic vegetation canopies and understanding vegetation growth.

Ultrafine (

Ultrafine particulate SRP may have an important role in the transfer of P from the Everglades Stormwater Treatment Areas (STAs), constructed wetlands designed to reduce phosphorus (P) in stormwater that is discharged to the Everglades Protection Area, to sensitive downstream water bodies due to increases in mobility associated with small particle size. P concentrations in discharges from the STAs are monitored using routine methods for particulate P (>0.45 μm) and dissolved P (<0.45 μm), an approach that does not consider ultrafine particulate P within the <0.45 μm fraction. Ultrafine particulate SRP was determined by ultrafiltration and was operationally defined as SRP associated with particles between <0.45 μm and <3 kDa. This study determined the magnitude and proportion of ultrafine particulate SRP within the <0.45 μm fraction of inflow, outflow, and in some cases, midflow waters from a selection of well-performing (discharge flow weighted mean concentration (FWMC) of P ≤ 20 μg L−1) and under-performing flow-ways (FWs) (FWMC P > 20 μg L−1) containing emergent aquatic vegetation (EAV), submerged aquatic vegetation (SAV) or a mix of EAV/SAV during the wet and dry season. During the wet season, inflow <0.45 μm SRP was predominately (60–100%) truly dissolved SRP (< 3 kDa) in all flow-ways. In the under-performing flow-ways, <0.45 μm SRP remained largely as truly dissolved, highly available SRP from inflow to outflow, whereas in the well-performing flow-ways, the percentage of <0.45 μm SRP present as ultrafine particulate SRP increased up to 100% as the distance from the inflow increased and the amount of truly dissolved SRP was very low. Two flow-ways having 100% particulate SRP at the outflow (STA-3/4 CFW and STA-5/6 FW1) contain an EAV cell followed by an EAV/SAV cell. However, in flow-ways containing more SAV (STA-2 FW3), ultrafine particulate SRP was a smaller proportion of outflow SRP (29%). During the dry season, ultrafine particulate SRP similarly increased from inflow to outflow at some well and under-performing sampling locations, but to a smaller proportion, and ultrafine particulate SRP never made up 100% of the <0.45 μm SRP fraction. These findings reveal that ultrafine particulate SRP is largely present within the <0.45 μm SRP fraction, at times making up >50% of TP, making it an important but poorly understood component of STA P budgets.

Analysis of Resource Potential of Emergent Aquatic Vegetation in the Curonian Lagoon of the Baltic Sea

This paper presents results of an aquatic vegetation resource potential assessment. The study is aimed at assessing the perspective of biotechnological approaches to reducing the biogenic pollution of water bodies by the removal of aquatic vegetation. The article analyzes the dominant species of aquatic vegetation in the Curonian Lagoon, and their productivity and resource potential. It was established that the concentrations of protein and fat in the biomass of four dominant plants are extremely low, making it impossible to speak of their values in terms of biomass processing. Based on elemental composition, we can conclude that the biomass of Phragmites australis should have a high calorie content because it has a high carbon and hydrogen content (49.6% and 7.1%, respectively), resulting in a high energy value. Synchronous thermal analysis revealed that the maximum energy values of biomasses of Phragmites australis and Scirpus lacustris have a net calorific value of 12.62 and 12.55 MJ/kg, respectively. At the same time, the biomass of these plants has a low ash content (around 6.6–7.6%) and a low sulfur content (less than 0.41%). An analysis of the composition of aquatic vegetation biomass samples allowed us to establish that, given the permissible collection time (no earlier than September), the search for directions in the utilization of aquatic vegetation should focus on processing cellulose with the production of crystalline cellulose, biochar, or biofuel via anaerobic digestion. The removal of the excess biomass of aquatic vegetation (Phragmites australis) will allow the reduction of the nitrogen and phosphorus load in the water body by 140 kg/ha and 14 kg/ha, respectively.

How can UAV contribute in satellite-based Phragmites australis aboveground biomass estimating?

• Build an UAV-based reed aboveground biomass (AGB) model by introducing canopy height. • Propose a way to obtain ample reed AGB samples matched with satellite pixel. • Develop a reed AGB satellite-based model and map the AGB in Nandagang Wetland. Phragmites australis (common reed) is a widely distributed emergent aquatic vegetation species in many wetland ecosystems, and its aboveground biomass (AGB) is an important parameter for evaluating the carbon–nitrogen cycle in wetlands. Satellite remote sensing (RS) is a powerful tool used to monitor the spatio-temporal distribution of AGB within reedbeds over a large area. However, when building AGB models based on satellite data, especially medium resolution satellites, it is difficult to obtain ample and properly measured AGB samples which can be matched with image pixels due to the inaccessibility of the wetlands. In this study, we proposed a solution based on the unmanned aerial vehicle (UAV) and Sentinel-2 data, which allowed us to estimate and successfully map the AGB of Phragmites australis in the Nan Da Gang Wetland Reserve (NDG) in China’s Hebei Province close to the Bohai sea. First, in an experimental area (EA) of NDG, an AGB model (R 2 = 0.74, RMSE = 174 g/m 2 ) was built based on NDVI (534, 734) and canopy height derived from UAV data, and an AGB map was obtained of the EA. Second, the AGB map was resampled to the pixel of the Sentinel-2 image, and an AGB sample set was matched with the acquired spatial resolution of the Sentinel-2 image. Finally, based on the sample set, an AGB model (R 2 = 0.59, RMSE = 194 g/m 2 ) was built using RVI derived from the Sentinel-2 image, which allowed us to map the Phragmites australis AGB in the NDG wetland reedbed. The study illustrated well that a UAV can be proficient in obtaining enough AGB samples matched with satellite pixels to build satellite-based AGB estimation models.

Genus-Level Mapping of Invasive Floating Aquatic Vegetation Using Sentinel-2 Satellite Remote Sensing

Invasive floating aquatic vegetation negatively impacts wetland ecosystems and mapping this vegetation through space and time can aid in designing and assessing effective control strategies. Current remote sensing methods for mapping floating aquatic vegetation at the genus level relies on airborne imaging spectroscopy, resulting in temporal gaps because routine hyperspectral satellite coverage is not yet available. Here we achieved genus level and species level discrimination between two invasive aquatic vegetation species using Sentinel 2 multispectral satellite data and machine-learning classifiers in summer and fall. The species of concern were water hyacinth (Eichornia crassipes) and water primrose (Ludwigia spp.). Our classifiers also identified submerged and emergent aquatic vegetation at the community level. Random forest models using Sentinel-2 data achieved an average overall accuracy of 90%, and class accuracies of 79–91% and 85–95% for water hyacinth and water primrose, respectively. To our knowledge, this is the first study that has mapped water primrose to the genus level using satellite remote sensing. Sentinel-2 derived maps compared well to those derived from airborne imaging spectroscopy and we also identified misclassifications that can be attributed to the coarser Sentinel-2 spectral and spatial resolutions. Our results demonstrate that the intra-annual temporal gaps between airborne imaging spectroscopy observations can be supplemented with Sentinel-2 satellite data and thus, rapidly growing/expanding vegetation can be tracked in real time. Such improvements have potential management benefits by improving the understanding of the phenology, spread, competitive advantages, and vulnerabilities of these aquatic plants.

The Importance of Lake Emergent Aquatic Vegetation for Estimating Arctic‐Boreal Methane Emissions

AbstractAreas of lakes that support emergent aquatic vegetation emit disproportionately more methane than open water but are under‐represented in upscaled estimates of lake greenhouse gas emissions. These shallow areas are typically less than ∼1.5 m deep and can be detected with synthetic aperture radar (SAR). To assess the importance of lake emergent vegetation (LEV) zones to landscape‐scale methane emissions, we combine airborne SAR mapping with field measurements of vegetated and open‐water methane flux. First, we use Uninhabited Aerial Vehicle SAR data from the NASA Arctic‐Boreal Vulnerability Experiment to map LEV in 4,572 lakes across four Arctic‐boreal study areas and find it comprises ∼16% of lake area, exceeding previous estimates, and exhibiting strong regional differences (averaging 59 [50–68]%, 22 [20–25]%, 1.0 [0.8–1.2]%, and 7.0 [5.0–12]% of lake areas in the Peace‐Athabasca Delta, Yukon Flats, and northern and southern Canadian Shield, respectively). Next, we account for these vegetated areas through a simple upscaling exercise using paired methane fluxes from regions of open water and LEV. After excluding vegetated areas that could be accounted for as wetlands, we find that inclusion of LEV increases overall lake emissions by 21 [18–25]% relative to estimates that do not differentiate lake zones. While LEV zones are proportionately greater in small lakes, this relationship is weak and varies regionally, underscoring the need for methane‐relevant remote sensing measurements of lake zones and a consistent criterion for distinguishing wetlands. Finally, Arctic‐boreal lake methane upscaling estimates can be improved with more measurements from all lake zones.

Evaluation of Implicit and Explicit Wave Dissipation Models for Submerged and Emergent Aquatic Vegetation

Ascencio, J.A.; Jacobsen, N.G.; McFall, B.C.; Groeneweg, J.; Vuik, V., and Reniers, A.J.H.M., 2022. Evaluation of implicit and explicit wave dissipation models for submerged and emergent aquatic vegetation. Journal of Coastal Research, 38(4), 807–815. Coconut Creek (Florida), ISSN 0749-0208. To address the important research question of whether implicit (bottom friction) or explicit (stem drag) dissipation models are most appropriate for the prediction of wave attenuation due to aquatic vegetation, the Simulating Waves Nearshore (SWAN) spectral wave model has been extended with an explicit frequency-dependent dissipation model for submerged and emergent vegetation. The new explicit model is compared to existing explicit and implicit dissipation models in SWAN, and the distinguishing features of each of the dissipation models are quantified. The present work verifies the implementation of the new and existing dissipation models, outlines their distinguishing features, and compares model predictions against experimental data. The emphasis is on the transformation of the spectral wave periods Tm0,1 and Tm–1,0 over a canopy. Model evaluation based on academic and laboratory cases allows for recommendations regarding applicability of the three dissipation models, where the new method has the broadest applicability, since it bridges the gap in applicability between the other two dissipation models. The implementation of Jacobsen, McFall, and van der A (2019; A frequency distributed dissipation model for canopies; Coastal Engineering, 150, 135–146) is publicly available in SWAN version 41.31B.

Recognition of aquatic vegetation above water using shortwave infrared baseline and phenological features

Accurate monitoring of emergent aquatic vegetation (EAV) and floating-leave aquatic vegetation (FAV), is vital because vegetation provides a critical habitat for aquatic animals and plays a critical role in protecting biodiversity. However, owing to the interference of water spectrum signals, it is difficult to extract the emerging aquatic vegetation information from remote sensing images, especially to distinguish between EAV and FAV. This study first proposed an enhanced aquatic vegetation index based on the difference in two short-wave infrared (SWIR) bands to extract the aquatic vegetation above the water surface, and then, the EAV and FAV were further distinguished coupled with the phenological characteristics, subsequently, a case study of Taihu Lake for accurately extracting seasonal and annual distributions. The results demonstrate that the proposed aquatic vegetation index is highly sensitive to EAV and FAV, and can further distinguish EAV from them coupled with phenological difference. Additionally, the dramatic changes in EAV and FAV in time and space indicated that human purse seine culture has had a great influence on the succession of aquatic vegetation, which may lead to the deterioration of the water ecology environment. Using the SWIR bands coupled with phenological difference is a promising method for recognizing aquatic vegetation above the water surface owing that it can weaken and eliminate the impact of algal bloom at the same time.

Invasive water chestnut hinders tidal wetland development

AbstractConsistent shoreline development and urbanization have historically resulted in the loss of wetlands. However, some construction activities have inadvertently resulted in the emergence of new tidal wetlands, with prominent examples of such anthropogenic wetlands found within the Hudson River Estuary. Here, we utilize two of these anthropogenically created tidal wetlands to explore the sedimentary and hydrologic conditions driving wetland development from a restoration perspective. Tivoli North is an emergent freshwater tidal marsh, while Tivoli South is an intertidal mudflat with vegetation restricted to the seasonal growth of invasive water chestnut during summer months. Using a combination of sediment traps, cores, and tidal flux measurements, we present highly resolved sediment budgets from these two protected bays and parameterize trapping processes responsible for their divergent wetland evolution. Utilizing a 16‐year tidal flux dataset, we observe net sediment trapping in Tivoli North for most years, with consistent trapping throughout the year. Conversely, flux measurements at Tivoli South reveal net sediment loss over the study period, with trapping constrained to the summer months. Here, we explore potential mechanisms responsible for these contrasting accumulation regimes, including initial geological differences, sediment loading, and human land use changes, with a focus on the invasion of emergent aquatic vegetation. Results suggest that water chestnut is contributing to these divergent morphologies by inhibiting sediment trapping and facilitating erosion, thereby preventing marsh nucleation in Tivoli South. The longevity of this dataset highlights the capacity of aquatic vegetation to regulate sediment exchange and geomorphology in enclosed bays when provided with an opportunity to colonize. The results of this project provide evidence to inform the management of restoration projects in river systems with tidal wetlands, especially those affected by invasive species of aquatic vegetation.

Relationship between anuran larvae occurrence and aquatic environment in septentrional east Palearctic landscapes

The presence of amphibian larvae is restricted by both biotic and abiotic variables of the environment. Some of these variables are still undetermined in the septentrional eastern Palearctic where Rana amurensis, Strauchbufo raddei and Dryophytes japonicus are found in large numbers. In this study, we sampled 92 sites across Mongolia, Russia and the Democratic People’s Republic of Korea and measured biotic and abiotic water variables, as well as the height of flooded terrestrial and emergent aquatic vegetation at the breeding site. We determined that the presence of anuran larvae is generally, but not always, linked to pH and temperature. Rana amurensis was not significantly affected by any of the variables measured, while S. raddei was impacted by water conductivity and D. japonicus by pH, temperature and vegetation. Our results highlight a potential risk for these species due to the changes in aquatic variables in response to desertification.

Long‐term accumulation of macro‐ and secondary elements in subtropical treatment wetlands

AbstractThe Everglades Stormwater Treatment Areas (STAs) are a complex of large constructed wetlands that are an integral component of the State and Federal efforts to restore the Everglades ecosystem. The overall objective of this study was to determine the accumulation rates of macro‐elements including carbon (C), nitrogen (N), phosphorus (P), sulfur (S), and associated secondary elements including calcium (Ca), magnesium (Mg), aluminum (Al), and iron (Fe) in two Everglades STAs over their periods of operation. The study was conducted in STA‐2 with parallel flow‐ways consisting of emergent aquatic vegetation (EAV) and submerged aquatic vegetation (SAV) and the Western flow‐way of STA‐3/4 with EAV and SAV cells operated in series. Elemental accumulation rates were determined in the unconsolidated surficial sediments (floc) and recently accreted soil (RAS) that have accumulated on top of the antecedent soil over the 14‐ and 10‐yr periods of operation for STA‐2 and STA‐3/4, respectively. Flow‐ways with SAV were more efficient than EAV in accreting mineral matter, resulting in increased bulk density and higher accumulation rates of elements. Average C accumulation in the floc and RAS of SAV flow‐ways was 320 g·m−2·yr−1 with approximately equal proportions of inorganic and organic C, while in the EAV flow‐ways accumulation rates of C ranged from 116 to 147 g·m−2·yr−1 with mostly organic C. Phosphorus accumulation rates were approximately 2–3 times higher in SAV than in EAV flow‐ways. Differences in accumulation of elements between SAV and EAV were largest for Ca with 17–42 times more Ca in SAV than EAV systems. This suggests that in the SAV systems, possible occlusion of macro‐elements and metals during CaCO3 precipitation facilitated accretion of material with high mineral content. In EAV, biomass turnover and associated biotic processes regulated organic matter accumulation rates. The spatial accumulation patterns of P, C, and N in the EAV areas of STA‐2 and STA‐3/4 were similar to those observed in the EAV areas of the natural wetlands in Water Conservation Areas, suggesting that constructed wetland systems function similarly to natural wetlands dominated by EAV areas in retaining and storing macro‐ and secondary elements.

Mineralogy of particulate inputs and P-speciation and mineralogy of recently accreted soils within Everglades stormwater treatment wetlands

Phosphorus (P) biogeochemical processes in wetlands are influenced by the chemical composition of both recently accreted and native soils. The evaluation of biogeochemical processes influencing P transformations requires an understanding of the participating chemical components. Here, we use X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy-dispersive X-ray fluorescence spectroscopy (EDS), X-ray absorption near-edge P spectroscopy (P-XANES), and microprobe X-ray fluorescence (μ-XRF) to examine the mineralogy and P speciation of solid phases entering and within selected Everglades Stormwater Treatment Areas (STAs). Suspended particulates in the source waters (upstream of the STAs) to the STAs were examined and compared with those of recently-accreted soil (RAS) from inflow, mid-flow, and outflow locations of two flowways (FWs) within STA-2: one dominated by emergent aquatic vegetation (EAV) and the other dominated by submerged aquatic vegetation (SAV). Source water particulates included carbonates and silicates, whereas mineralogies of STA RAS were less diverse, dominated by CaCO3 and having a lower silicate content, suggesting a strong autochthonous influence on STA RAS composition. No P minerals were detected via XRD. Discrete CaP particles were evident, though uncommonly observed, in two of three STA RAS samples analyzed via SEM/EDS. P-XANES of STA RAS indicated the presence of apatitic minerals. The potential presence of apatitic minerals was supported by μ-XRF correlation analysis that revealed strong correlations of P with both Ca and K. Apatitic minerals are a relatively refractory form of P and their presence in the RAS of both EAV and SAV systems indicate that remobilization and release of this P from the STAs will have a smaller effect on the downstream oligotrophic conditions of the Florida Everglades than more labile forms of P.