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At least 1,099 records · Page 61Linked to original sources
USGS2000

Effects of asynchronous snowmelt on flushing of dissolved organic carbon: A mixing model approach

In many snowmelt-dominated catchments, stream dissolved organic carbon (DOC) levels typically increase rapidly as spring melt commences, peak before maximum discharge, and decrease quickly as melting continues. We present data from Deer Creek (Summit County, CO) that shows this distinctive flushing response of DOC during snowmelt runoff, with DOC stored in landscape soils flushed to the stream in response to infiltrating melt waters. Our prior studies show that asynchronous melting of the snowpack across the landscape causes the spring DOC flush to be initiated at different times throughout the catchment. In this study we quantify characteristics of the asynchronous melt and its effect on DOC flushing. We investigated whether a simple mixing model can be used to capture the essentials of the asynchronous melting of a seasonal snowpack and its controls on DOC transport. We divided the catchment into zones of aspect and elevation, which largely determine spatial and temporal variations in the distribution of snow. TOPMODEL was used to simulate the hydrology in each zone, and the simulated flow paths were routed through a simple DOC mixing model to predict contributions of DOC to the stream. The zonal responses were aggregated to give a predicted response of hydrology and DOC fluxes for the entire catchment. Our results indicate that asynchronous melting-which determines the timing of contributions of discharge and DOC to streamflow from different areas of the landscape-can be quantified using a simple modeling approach.

Hydrological Processes↗
USGS2015

Soil greenhouse gas emissions and carbon budgeting in a short-hydroperiod floodplain wetland

Understanding the controls on floodplain carbon (C) cycling is important for assessing greenhouse gas emissions and the potential for C sequestration in river-floodplain ecosystems. We hypothesized that greater hydrologic connectivity would increase C inputs to floodplains that would not only stimulate soil C gas emissions but also sequester more C in soils. In an urban Piedmont river (151 km 2 watershed) with a floodplain that is dry most of the year, we quantified soil CO 2 , CH 4 , and N 2 O net emissions along gradients of floodplain hydrologic connectivity, identified controls on soil aerobic and anaerobic respiration, and developed a floodplain soil C budget. Sites were chosen along a longitudinal river gradient and across lateral floodplain geomorphic units (levee, backswamp, and toe slope). CO 2 emissions decreased downstream in backswamps and toe slopes and were high on the levees. CH 4 and N 2 O fluxes were near zero; however, CH 4 emissions were highest in the backswamp. Annual CO 2 emissions correlated negatively with soil water-filled pore space and positively with variables related to drier, coarser soil. Conversely, annual CH 4 emissions had the opposite pattern of CO 2 . Spatial variation in aerobic and anaerobic respiration was thus controlled by oxygen availability but was not related to C inputs from sedimentation or vegetation. The annual mean soil CO 2 emission rate was 1091 g C m −2  yr −1 , the net sedimentation rate was 111 g C m −2  yr −1 , and the vegetation production rate was 240 g C m −2  yr −1 , with a soil C balance (loss) of −338 g C m −2  yr −1 . This floodplain is losing C likely due to long-term drying from watershed urbanization.

Virginia↗
USGS2014

Lattice Boltzmann methods applied to large-scale three-dimensional virtual cores constructed from digital optical borehole images of the karst carbonate Biscayne aquifer in southeastern Florida

Digital optical borehole images at approximately 2 mm vertical resolution and borehole caliper data were used to create three-dimensional renderings of the distribution of (1) matrix porosity and (2) vuggy megaporosity for the karst carbonate Biscayne aquifer in southeastern Florida. The renderings based on the borehole data were used as input into Lattice Boltzmann methods to obtain intrinsic permeability estimates for this extremely transmissive aquifer, where traditional aquifer test methods may fail due to very small drawdowns and non-Darcian flow that can reduce apparent hydraulic conductivity. Variogram analysis of the borehole data suggests a nearly isotropic rock structure at lag lengths up to the nominal borehole diameter. A strong correlation between the diameter of the borehole and the presence of vuggy megaporosity in the data set led to a bias in the variogram where the computed horizontal spatial autocorrelation is strong at lag distances greater than the nominal borehole size. Lattice Boltzmann simulation of flow across a 0.4 × 0.4 × 17 m (2.72 m 3 volume) parallel-walled column of rendered matrix and vuggy megaporosity indicates a high hydraulic conductivity of 53 m s −1 . This value is similar to previous Lattice Boltzmann calculations of hydraulic conductivity in smaller limestone samples of the Biscayne aquifer. The development of simulation methods that reproduce dual-porosity systems with higher resolution and fidelity and that consider flow through horizontally longer renderings could provide improved estimates of the hydraulic conductivity and help to address questions about the importance of scale.

Water Resources Research↗
USGS2016

Toward more realistic projections of soil carbon dynamics by Earth system models

Soil carbon (C) is a critical component of Earth system models (ESMs), and its diverse representations are a major source of the large spread across models in the terrestrial C sink from the third to fifth assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Improving soil C projections is of a high priority for Earth system modeling in the future IPCC and other assessments. To achieve this goal, we suggest that (1) model structures should reflect real-world processes, (2) parameters should be calibrated to match model outputs with observations, and (3) external forcing variables should accurately prescribe the environmental conditions that soils experience. First, most soil C cycle models simulate C input from litter production and C release through decomposition. The latter process has traditionally been represented by first-order decay functions, regulated primarily by temperature, moisture, litter quality, and soil texture. While this formulation well captures macroscopic soil organic C (SOC) dynamics, better understanding is needed of their underlying mechanisms as related to microbial processes, depth-dependent environmental controls, and other processes that strongly affect soil C dynamics. Second, incomplete use of observations in model parameterization is a major cause of bias in soil C projections from ESMs. Optimal parameter calibration with both pool- and flux-based data sets through data assimilation is among the highest priorities for near-term research to reduce biases among ESMs. Third, external variables are represented inconsistently among ESMs, leading to differences in modeled soil C dynamics. We recommend the implementation of traceability analyses to identify how external variables and model parameterizations influence SOC dynamics in different ESMs. Overall, projections of the terrestrial C sink can be substantially improved when reliable data sets are available to select the most representative model structure, constrain parameters, and prescribe forcing fields.

Global Biogeochemical Cycles↗
USGS2016

Climate change and dissolved organic carbon export to the Gulf of Maine

Ongoing climate change is affecting the concentration, export (flux), and timing of dissolved organic carbon (DOC) exported to the Gulf of Maine (GoM) through changes in hydrologic regime. DOC export was calculated for water years 1950 through 2013 for 20 rivers and for water years 1930 through 2013 for 14 rivers draining to the GoM. DOC export was also estimated for the 21st century based on climate and hydrologic modeling in a previously published study. DOC export was calculated by using the regression model LOADEST to fit seasonally adjusted concentration discharge (C-Q) relations. Our results are an analysis of the sensitivity of DOC export to changes in hydrologic conditions over time since land cover and vegetation were held constant over time. Despite large interannual variability, all rivers had increasing DOC export during winter and these trends were significant ( p < 0.05) in 10 out of 20 rivers for 1950 to 2013 and in 13 out of 14 rivers for 1930 to 2013. All rivers also had increasing annual export of DOC although fewer trends were statistically significant than for winter export. Projections for DOC export during the 21st century were variable depending on the climate model and greenhouse gas emission scenario that affected future river discharge through effects on precipitation and evapotranspiration. The most consistent result was a significant increase in DOC export in winter in all model-by-emission scenarios. DOC export was projected to decrease during the summer in all model-by-emission scenarios, with statistically significant decreases in half of the scenarios.

Maine↗
USGS2017

Estimating belowground carbon stocks in isolated wetlands of the Northern Everglades Watershed, central Florida, using ground penetrating radar (GPR) and aerial imagery

Peat soils store a large fraction of the global soil carbon (C) pool and comprise 95% of wetland C stocks. While isolated freshwater wetlands in temperate and tropical biomes account for more than 20% of the global peatland C stock, most studies of wetland soil C have occurred in expansive peatlands in northern boreal and subarctic biomes. Furthermore, the contribution of small depressional wetlands in comparison to larger wetland systems in these environments is very uncertain. Given the fact that these wetlands are numerous and variable in terms of their internal geometry, innovative methods are needed for properly estimating belowground C stocks and their overall C contribution to the landscape. In this study, we use a combination of ground penetrating radar (GPR), aerial imagery, and direct measurements (coring) in conjunction with C core analysis to develop a relation between C stock and surface area, and estimate the contribution of subtropical depressional wetlands to the total C stock of pine flatwoods at the Disney Wilderness Preserve (DWP), Florida. Additionally, GPR surveys were able to image collapse structures underneath the peat basin of depressional wetlands, depicting lithological controls on the formation of depressional wetlands at the DWP. Results indicate the importance of depressional wetlands as critical contributors to the landscape C budget at the DWP and the potential of GPR-based approaches for (1) rapidly and noninvasively estimating the contribution of depressional wetlands to regional C stocks and (2) evaluating the formational processes of depressional wetlands.

Florida↗
USGS2017

The impact of late Holocene land-use change, climate variability, and sea-level rise on carbon storage in tidal freshwater wetlands on the southeastern United States Coastal Plain

This study examines Holocene impacts of changes in climate, land use, and sea-level rise (SLR) on sediment accretion, carbon accumulation rates (CAR), and vegetation along a transect of tidal freshwater forested wetlands (TFFW) to oligohaline marsh along the Waccamaw River, South Carolina (4 sites) and along the Savannah River, Georgia (4 sites). We use pollen, plant macrofossils, accretion, and CAR from cores, spanning the last 1500-6000 years to test the hypothesis that TFFW have remained stable throughout the late Holocene and that marshes transitioned from TFFW during elevated SLR during the Medieval Climate Anomaly, with further transformation resulting from colonial land-use change. Results show low and stable accretion and CAR through much of the Holocene, despite moderate changes associated with Holocene paleoclimate. In all records, the largest observed change occurred within the last ~400 years, driven by colonial land clearance, shifting terrigenous sediment into riparian wetlands, resulting in order-of-magnitude increases in accretion and C accumulation. The oligohaline marshes transitioned from TFFW ~300-500 years ago, coincident with colonial land clearance. Post-colonial decreases in CAR and accretion occur because of watershed reforestation over the last century. All sites show evidence of recent (decades to century) swamp forest decline due to increasing salinity and tidal inundation from SLR. This study suggests that allochthonous sediment input during colonialization helped maintain TFFW, but that current SLR rates are too high for TFFW to persist, although higher accretion rates in oligohaline marshes increases the resilience of tidal wetlands as they transition from TFFW to marsh.

Georgia, South Carolina↗
USGS2021

Land management strategies influence soil organic carbon stocks of prairie potholes of North America

Soil organic carbon (SOC) stocks of Prairie Pothole Region (PPR) wetlands in the central plains of Canada and the United States are highly variable due to natural variation in biota, soils, climate, hydrology, and topography. Land-use history (cropland, grassland) and land-management practices (drainage, restoration) also affect SOC stocks. We conducted a region-wide assessment of wetland SOC stocks using data from the Canadian and US portions of the PPR under various management types. Natural wetlands with no disturbance history in the wetland basin or surrounding catchment had considerably greater average SOC stocks in the upper (0–15 cm) soil profile than wetlands surrounded by cropland. Hydrologically restored wetlands did not show significantly greater SOC stocks than drained wetlands, but wetlands surrounded by restored grasslands did have greater SOC stocks in the upper soil profile than those surrounded by croplands. Similarities among cropped and restored wetlands likely were due to insufficient time since restoration, as well as high variability attributable to several environmental factors within the region. We conclude that avoided loss of natural wetlands from drainage and avoided loss of native grasslands from cropping have the most benefit for preserving wetland SOC stocks. Robust PPR SOC models that incorporate multiple abiotic, biotic, and land-use factors are required to determine where and when restoration is most effective for SOC sequestration.

Book chapter↗
USGS2017

Fuel-reduction management alters plant composition, carbon and nitrogen pools, and soil thaw in Alaskan boreal forest

Increasing wildfire activity in Alaska's boreal forests has led to greater fuel-reduction management. Management has been implemented to reduce wildfire spread, but the ecological impacts of these practices are poorly known. We quantified the effects of hand-thinning and shearblading on above- and belowground stand characteristics, plant species composition, carbon (C) and nitrogen (N) pools, and soil thaw across 19 black spruce ( Picea mariana ) dominated sites in interior Alaska treated 2-12 years prior to sampling. The density of deciduous tree seedlings was significantly higher in shearbladed areas compared to unmanaged forest (6.4 vs. 0.1 stems m −2 ), and unmanaged stands exhibited the highest mean density of conifer seedlings and layers (1.4 stems m −2 ). Understory plant community composition was most similar between unmanaged and thinned stands. Shearblading resulted in a near complete loss of aboveground tree biomass C pools while thinning approximately halved the C pool size (1.2 kg C m −2 compared to 3.1 kg C m −2 in unmanaged forest). Significantly smaller soil organic layer (SOL) C and N pools were observed in shearbladed stands (3.2 kg C m −2 and 116.8 g N m −2 ) relative to thinned (6.0 kg C m −2 and 192.2 g N m −2 ) and unmanaged (5.9 kg C m −2 and 178.7 g N m −2 ) stands. No difference in C and N pool sizes in the uppermost 10 cm of mineral soil was observed among stand types. Total C stocks for measured pools was 2.6 kg C m −2 smaller in thinned stands and 5.8 kg C m −2 smaller in shearbladed stands when compared to unmanaged forest. Soil thaw depth averaged 13 cm deeper in thinned areas and 46 cm deeper in shearbladed areas relative to adjacent unmanaged stands, although variability was high across sites. Deeper soil thaw was linked to shallower SOL depth for unmanaged stands and both management types, however for any given SOL depth, thaw tended to be deeper in shearbladed areas compared to unmanaged forest. These findings indicate that fuel-reduction management alters plant community composition, C and N pools, and soil thaw depth, with consequences for ecosystem structure and function beyond those intended for fire management.

Alaska↗
USGS2017

Life history constraints explain negative relationship between fish productivity and dissolved organic carbon in lakes

Resource availability constrains the life history strategies available to organisms and may thereby limit population growth rates and productivity. We used this conceptual framework to explore the mechanisms driving recently reported negative relationships between fish productivity and dissolved organic carbon (DOC) concentrations in lakes. We studied populations of bluegill ( Lepomis macrochirus ) in a set of lakes with DOC concentrations ranging from 3 to 24 mg/L; previous work has demonstrated that primary and secondary productivity of food webs is negatively related to DOC concentration across this gradient. For each population, we quantified individual growth rate, age at maturity, age‐specific fecundity, maximum age, length‐weight and length‐egg size relationships, and other life history characteristics. We observed a strong negative relationship between maximum size and DOC concentration; for instance, fish reached masses of 150 to 260 g in low‐DOC lakes but <120 g in high‐DOC lakes. Relationships between fecundity and length, and between egg size and length, were constant across the DOC gradient. Because fish in high‐DOC lakes reached smaller sizes but had similar fecundity and egg size at a given size, their total lifetime fecundity was as much as two orders of magnitude lower than fish in low‐DOC lakes. High DOC concentrations appeared to constrain the range of bluegill life history strategies available; populations in high‐DOC lakes always had low initial growth rates and high ages at maturity, whereas populations in low‐DOC showed higher variability in these traits. This was also the case for the intrinsic rates of natural increase of these populations, which were always low at the high end of the DOC gradient. The potentially lower capacity for fish populations in high‐DOC lakes to recover from exploitation has clear implications for the sustainable management of recreational fisheries in the face of considerable spatial heterogeneity and ongoing temporal change in lake DOC concentrations.

Wisconsin↗
USGS2016

Total belowground carbon flux in subalpine forests is related to leaf area index, soil nitrogen, and tree height

In forests, total belowground carbon (C) flux (TBCF) is a large component of the C budget and represents a critical pathway for delivery of plant C to soil. Reducing uncertainty around regional estimates of forest C cycling may be aided by incorporating knowledge of controls over soil respiration and TBCF. Photosynthesis, and presumably TBCF, declines with advancing tree size and age, and photosynthesis increases yet C partitioning to TBCF decreases in response to high soil fertility. We hypothesized that these causal relationships would result in predictable patterns of TBCF, and partitioning of C to TBCF, with natural variability in leaf area index (LAI), soil nitrogen (N), and tree height in subalpine forests in the Rocky Mountains, USA. Using three consecutive years of soil respiration data collected from 22 0.38-ha locations across three 1-km 2 subalpine forested landscapes, we tested three hypotheses: (1) annual soil respiration and TBCF will show a hump-shaped relationship with LAI; (2) variability in TBCF unexplained by LAI will be related to soil nitrogen (N); and (3) partitioning of C to TBCF (relative to woody growth) will decline with increasing soil N and tree height. We found partial support for Hypothesis 1 and full support for Hypotheses 2 and 3. TBCF, but not soil respiration, was explained by LAI and soil N patterns ( r 2 = 0.49), and the ratio of annual TBCF to TBCF plus aboveground net primary productivity (ANPP) was related to soil N and tree height ( r 2 = 0.72). Thus, forest C partitioning to TBCF can vary even within the same forest type and region, and approaches that assume a constant fraction of TBCF relative to ANPP may be missing some of this variability. These relationships can aid with estimates of forest soil respiration and TBCF across landscapes, using spatially explicit forest data such as national inventories or remotely sensed data products.

Ecosphere↗
USGS2016

Drought resistance across California ecosystems: Evaluating changes in carbon dynamics using satellite imagery

Drought is a global issue that is exacerbated by climate change and increasing anthropogenic water demands. The recent occurrence of drought in California provides an important opportunity to examine drought response across ecosystem classes (forests, shrublands, grasslands, and wetlands), which is essential to understand how climate influences ecosystem structure and function. We quantified ecosystem resistance to drought by comparing changes in satellite-derived estimates of water-use efficiency (WUE = net primary productivity [NPP]/evapotranspiration [ET]) under normal (i.e., baseline) and drought conditions (ΔWUE = WUE 2014 − baseline WUE). With this method, areas with increasing WUE under drought conditions are considered more resilient than systems with declining WUE. Baseline WUE varied across California (0.08 to 3.85 g C/mm H 2 O) and WUE generally increased under severe drought conditions in 2014. Strong correlations between ΔWUE, precipitation, and leaf area index (LAI) indicate that ecosystems with a lower average LAI (i.e., grasslands) also had greater C-uptake rates when water was limiting and higher rates of carbon-uptake efficiency (CUE = NPP/LAI) under drought conditions. We also found that systems with a baseline WUE ≤ 0.4 exhibited a decline in WUE under drought conditions, suggesting that a baseline WUE ≤ 0.4 might be indicative of low drought resistance. Drought severity, precipitation, and WUE were identified as important drivers of shifts in ecosystem classes over the study period. These findings have important implications for understanding climate change effects on primary productivity and C sequestration across ecosystems and how this may influence ecosystem resistance in the future.

California↗
USGS2022

Multiple resource limitation of dryland soil microbial carbon cycling on the Colorado Plateau

Understanding interactions among biogeochemical cycles is increasingly important as anthropogenic alterations of global climate and of carbon (C), nitrogen (N), and phosphorus (P) cycles interactively affect the Earth system. Ecosystem processes in the dryland biome, which makes up over 40% of Earth's terrestrial surface, are often distinctively sensitive to small changes in resource availability, likely because levels of many resources are low. However, data also suggest that simultaneous changes in the availability of multiple resources may be necessary to affect a response in these low-resource systems, offering an opportunity to test patterns and controls of co-limitation, serial limitation, and individual limitation in soil environments. While drylands may play a governing role in key aspects of Earth's C cycle, and while an improved understanding of resource limitation could substantially improve our forecasts of dryland responses to change, our understanding of interacting controls on soil C cycle processes remains notably poor in these dry systems. Here, we address multiple fundamental hypotheses of resource controls over ecosystem function to test how water, C, N, and P regulate soil C cycling individually and interactively in a dryland ecosystem on the Colorado Plateau. Using a series of laboratory incubations, we found that, while water, C, and N limited C cycling through serial limitation, water alone resulted in an extremely small respiratory response from target organisms, whereas water + C resulted in a dramatic increase in soil C cycling, suggesting a degree of functional co-limitation. Nitrogen additions alone resulted in no changes to soil C cycling, but when N was added in concert with water and C, N greatly increased soil C cycling rates relative to additions of water and C without N. Phosphorus additions had no effect on the C cycle either alone or synergistically. These patterns were consistent with the stoichiometry of the system and interactions among resources were surprising in ways that inform our understanding of critical theories in ecology, such as the Transient Maxima Hypothesis, supporting the suggestion that multiple resource limitation explains pulse-dynamic C cycling in drylands better than water limitation alone.

Utah↗
USGS2016

Effects of carbon dioxide on juveniles of the freshwater mussel ( Lampsilis siliquoidea [Unionidae])

Carbon dioxide (CO 2 ) has shown promise as a tool to control movements of invasive Asian carp, but its effects on native freshwater biota have not been well studied. The authors evaluated lethal and sublethal responses of juvenile fatmucket ( Lampsilis siliquoidea ) mussels to CO 2 at levels (43–269 mg/L, mean concentration) that bracket concentrations effective for deterring carp movement. The 28-d lethal concentration to 50% of the mussels was 87.0 mg/L (95% confidence interval [CI] 78.4–95.9) and at 16-d postexposure, 76.0 mg/L (95% CI 62.9–90.3). A proportional hazards regression model predicted that juveniles could not survive CO 2 concentrations >160 mg/L for more than 2 wk or >100 mg/L CO 2 for more than 30 d. Mean shell growth was significantly lower for mussels that survived CO 2 treatments. Growth during the postexposure period did not differ among treatments, indicating recovery of the mussels. Also, CO 2 caused shell pitting and erosion. Behavioral effects of CO 2 included movement of mussels to the substrate surface and narcotization at the highest concentrations. Mussels in the 110 mg/L mean CO 2 treatment had the most movements in the first 3 d of exposure. If CO 2 is infused continuously as a fish deterrent, concentrations <76 mg/L are recommended to prevent juvenile mussel mortality and shell damage. Mussels may survive and recover from brief exposure to higher concentrations.

Environmental Toxicology and Chemistry↗
USGS2020

Temperature‐related responses of an invasive mussel and 2 unionid mussels to elevated carbon dioxide

Zebra mussels (Dreissena polymorpha) have exacerbated the decline of native freshwater mussels (Order Unionida) in North America since their arrival in the 1980s. Options for controlling invasive mussels, particularly in unionid mussel habitats, are limited. Previously, carbon dioxide (CO2) showed selective toxicity for zebra mussels, relative to unionids, when applied in cool water (12 °C). We first determined 96 h lethal concentrations of CO2 at 5 and 20 °C to zebra mussels and responses of juvenile plain pocketbook (Lampsilis cardium). Next, we compared the time to lethality for zebra mussels at 5, 12, and 20 °C during exposure to partial pressure of CO2 (PCO2) 110¬–120 atmospheres (atm; 1 atm = 101.325 kPa) and responses of juvenile plain pocketbook and fragile papershell (Leptodea fragilis). We found efficacious CO2 treatment regimens at each temperature that were minimally lethal to unionids. At 5 °C, plain pocketbook survived 96 h exposure to the highest PCO2 treatment (139 atm). At 20 °C, the 96 h LC10 (lethal concentration to 10% of animals) for plain pocketbook [173 atm PCO2, 95% confidence interval (CL) 147–198 atm] was higher than the LC99 for zebra mussels (118 atm PCO2, CL 109–127 atm). Lethal time to 99% mortality (LT99) of zebra mussels in 110 to 120 atm PCO2 ranged from 100 h at 20 °C to 300 h at 5 °C. Mean survival of juvenile unionids exceeded 85% in LT99 CO2 treatments at all temperatures. Short-term infusion of 100 to 200 atm PCO2 at a range of water temperatures could reduce biofouling by zebra mussels with limited adverse effects on unionid mussels.

Environmental Toxicology and Chemistry↗
USGS2020

Toxicity of carbon dioxide to freshwater fishes: Implications for aquatic invasive species management

Carbon dioxide (CO 2 ) has been approved by the US Environmental Protection Agency as a new aquatic pesticide to control invasive Asian carps and other aquatic nuisance species in the United States. However, limited CO 2 toxicity data could make it challenging for resource managers to characterize the potential risk to nontarget species during CO 2 applications. The present study quantified the toxicity of CO 2 to 2 native riverine fishes, bluegill ( Lepomis macrochirus ) and fathead minnow ( Pimephales promelas ), using 12‐h continuous flow‐through CO 2 exposure at 5, 15, and 25 °C water temperatures. Resulting survival indicated that bluegill (median lethal concentration [LC50] range 91–140 mg/L CO 2 ) were more sensitive to CO 2 than fathead minnow (LC50 range 235–306 mg/L CO 2 ) across all water temperatures. Bluegill were also more sensitive to CO 2 at 5 °C (LC50 91 mg/L CO 2 , 95% CI 85–96 mg/L CO 2 ) than at 25 °C (LC50 140 mg/L CO 2 , 95% CI 135–146 mg/L CO 2 ). Fathead minnow showed an opposite response and were less sensitive at 5 °C (LC50 306 mg/L CO 2 , 95% CI 286–327 mg/L CO 2 ) relative to 25 °C (LC50 235 mg/L CO 2 , 95% CI 224–246 mg/L CO 2 ). Our results show that CO 2 toxicity can differ by species and water temperature. Data from the present study may inform decisions related to the use of CO 2 as a control tool. Environ Toxicol Chem 2020;39:2247–2255. Published 2020. This article is a U.S. government work and is in the public domain in the USA.

Environmental Toxicology and Chemistry (ET&C)↗
USGS2024

Carbon dioxide toxicity to zebra mussels (Dreissena polymorpha) is dependent on water chemistry

Carbon dioxide (CO 2 ) is gaining interest as a tool to combat aquatic invasive species, including zebra mussels ( Dreissena polymorpha ). However, the effects of water chemistry on CO 2 efficacy are not well described. We conducted five trials in which we exposed adult zebra mussels to a range of CO 2 in water with adjusted total hardness and specific conductance. We compared dose–responses and found differences in lethal concentration to 50% of organisms (LC50) estimates ranging from 108.3 to 179.3 mg/L CO 2 and lethal concentration to 90% of organisms (LC90) estimates ranging from 163.7 to 216.6 mg/L CO 2 . We modeled LC50 and LC90 estimates with measured water chemistry variables from the trials. We found sodium (Na + ) concentration to have the strongest correlation to changes in the LC50 and specific conductance to have the strongest correlation to changes in the LC90. Our results identify water chemistry as an important factor in considering efficacious CO 2 concentrations for zebra mussel control. Additional research into the physiological responses of zebra mussels exposed to CO 2 may be warranted to further explain mode of action and reported selectivity. Further study could likely develop a robust and relevant model to refine CO 2 applications for a wider range of water chemistries. Environ Toxicol Chem 2024;00:1–8. Published 2024. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Environmental Toxicology and Chemistry↗