Intraspecific variation in crayfish behavioral traits affects leaf litter breakdown in streams.

Although intraspecific trait variation is increasingly recognized as affecting ecosystem processes, few studies have examined the ecological significance of among-population variation in behavioral traits in natural ecosystems. In freshwater habitats, crayfish are consumers that can influence ecosystem structure (e.g., macroinvertebrate communities) and function (e.g., leaf litter breakdown). To test whether crayfish behavioral traits (activity, boldness, and foraging voracity) are major contributors of leaf litter breakdown rates in the field, we collected rusty crayfish (Faxonius rusticus) from eight streams across the midwestern USA and measured behaviors using laboratory assays. At the same streams, we measured breakdown rates of leaf packs that were accessible or inaccessible to crayfish. Our results provide evidence that among-population variation in crayfish boldness and foraging voracity was a strong predictor of leaf litter breakdown rates, even after accounting for commonly appreciated environmental drivers (water temperature and human land use). Our results suggest that less bold rusty populations (i.e., emerged from shelter more slowly) had greater direct impacts on leaf litter breakdown than bold populations (P = 0.001, r2 = 0.85), potentially because leaf packs can be both a shelter and food resource to crayfish. Additionally, we found that foraging voracity was negatively related to breakdown rates in leaf packs that were inaccessible to crayfish (P = 0.025, r2 = 0.60), potentially due to a trophic cascade from crayfish preying on other invertebrates that consume leaf litter. Overall, our results add to the growing evidence that trait variation in animals may be important for understanding freshwater ecosystem functioning.

Leaching of select per-/poly-fluoroalkyl substances, pharmaceuticals, and hormones through soils amended with composted biosolids.

The use of organic amendments to enhance soil health is increasingly being identified as a strategy to improve residential landscapes while also reducing the need for external inputs (e.g., fertilizers, irrigation). Composted biosolids are a re-purposed waste product that can be used in organic amendments to improve the overall sustainability of a municipality by enhancing residential soil carbon content while simultaneously reducing waste materials. However, the biosolids-based feedstock of these compost products has the potential to be a source of organic contaminants. We conducted a laboratory-based soil column experiment to evaluate the potential for different commercially available compost products to act as a source of emerging organic contaminants in residential landscapes. We compared two biosolids-based compost products, a manure-based compost product, and a control (no compost) treatment by irrigating soil columns for 30 days and collecting daily leachate samples to quantify leaching rates of six hormones, eight pharmaceuticals, and seven per- and polyfluoroalkyl substances (PFAS). Detection of hormones and pharmaceuticals was rare, suggesting that compost amendments are likely not a major source of these contaminants to groundwater resources. In contrast, we detected three of the seven PFAS compounds in leachate samples throughout the study. Perfluorohexanoic acid (PFHxA) was more likely to leach from biosolids-based compost treatments than other treatments (p < 0.05) and perfluorobutane sulfonate (PFBS) was only detected in biosolids-based treatments (although PFBS concentrations did not significantly differ among treatments). In contrast, perfluorooctanoic acid (PFOA) was commonly detected across all treatments (including controls), suggesting potential PFOA experimental contamination. Overall, these results demonstrate that commercially available composted biosolids amendments are likely not a major source of hormone and pharmaceutical contamination. The detection of PFHxA at significantly higher concentrations in biosolids treatments suggests that biosolids-based composts may act as sources of PFHxA to the environment. However, concentrations of multiple PFAS compounds found in leachate in this study were lower than concentrations found in known PFAS hotspots. Therefore, there is potential for environmental contamination from PFAS leaching from composted biosolids, but leachate concentrations are low which should be considered in risk-benefit analyses when considering whether or not to use composted biosolids as an organic amendment to enhance residential soil health.

Influence of Water Resource Recovery Facility Effluents on the Presence of Selected Trace Organic Contaminants (TOrCs) in the Reedy River, South Carolina.

Wastewater reclamation facilities are known sources of emerging contaminants associated with human health and sanitation. This study evaluated the contribution of trace organic contaminants to a previously unmonitored river by water resource reclamation facilities. Six sampling events were conducted on the Reedy River in South Carolina. Sampling locations included sites upstream and downstream of two WRRFs located on the river to examine potential contributions under drought conditions where WRRF effluents comprise a large proportion of total stream flow. Five target analytes were monitored including atrazine, carbamazepine, 17ß-estradiol, perfluorooctanoic acid, and sulfamethoxazole. On a mass basis, the WRRFs contributed additional loadings of carbamazepine ranging from 5.4 g/d to 7.2 g/d (mean: 6.3 ± 0.4 g/d), PFOA ranging from 8.6 to 31.9 g/d (mean: 20.0 ± 4.9), and sulfamethoxazole ranging from 49.4 g/d to 75.1 g/d (mean: 62.1 ± 4.8). 17ß-estradiol was detected once and atrazine was not detected.

Dosing the Coast: Leaking Sewage Infrastructure Delivers Large Annual Doses and Dynamic Mixtures of Pharmaceuticals to Urban Rivers.

Pharmaceuticals are commonly detected at low concentrations in surface waters, where they disrupt biological and ecological processes. Despite their ubiquity, the annual mass of pharmaceuticals exported from watersheds is rarely quantified. We used liquid chromatography-mass spectroscopy to screen for 92 pharmaceuticals in weekly samples from an urban stream network in Baltimore, MD, USA, that lacks wastewater treatment effluents. Across the network, we detected 37 unique compounds, with higher concentrations and more compounds in streams with higher population densities. We also used concentrations and stream discharge to calculate annual pharmaceutical loads at the watershed outlet, which range from less than 1 kg to ∼15 kg and are equivalent to tens of thousands of human doses. By calculating annual watershed mass balances for eight compounds, we show that ∼0.05 to ∼42% of the pharmaceuticals consumed by humans in this watershed are released to surface waters, with the importance of different pathways (leaking sewage vs treated wastewater effluent) differing among compounds. These results demonstrate the importance of developing, maintaining, and improving sewage infrastructure to protect water resources from pharmaceutical contamination.

Effects of ciprofloxacin on metabolic activity and algal biomass of urban stream biofilms.

Pharmaceuticals and personal care products (PPCPs), such as the commonly prescribed antibiotic ciprofloxacin, are present and persistent in freshwaters, yet their effects on aquatic ecosystem functions at environmentally-relevant concentrations are rarely explored. Stream biofilms provide multiple functions in stream ecosystems, but their functional response to PPCP contaminants such as ciprofloxacin is unclear. To establish the effect of ciprofloxacin on aquatic biofilms, we colonized biofilms in situ on tiles (n = 80) at four sites along an urban stream in Gainesville, Florida, including two sites above and two sites below a wastewater treatment plant (WWTP). We then incubated the tiles and associated biofilms in the laboratory for 6 d exposing biofilms to either 0, 0.01, 0.1, or 1.0 µg/L (target concentrations) of ciprofloxacin. At the end of the 6 d laboratory exposure, we quantified gross primary production (GPP), respiration (R), and biomass (as chlorophyll a) of biofilms, and calculated response ratios for each response. All response metrics were significantly differed across sites (p < 0.01). Ciprofloxacin significantly decreased GPP (p < 0.05) regardless of treatment concentration, most notably at the site immediately below the WWTP, where there was no measurable GPP on any ciprofloxacin-treated biofilms. In contrast, respiration (R) was not significantly affected by ciprofloxacin, despite an apparent increase in R at the WWTP site. However, the WWTP site R was significantly different from the most upstream and downstream sites (p < 0.001) but was not significantly different from a nearby site upstream of the WWTP (p > 0.05). These results indicate that chronic exposure to ciprofloxacin through WWTP effluent can alter ecosystem functions performed by biofilms, which can have consequences for higher trophic levels and stream processes. By quantifying biofilm metabolic responses to ciprofloxacin exposure, this study supports the concept that pharmaceuticals and personal care products can induce sub-lethal effects on ecological processes at environmentally-relevant concentrations.

Stormwater ponds: An overlooked but plentiful urban designer ecosystem provides invasive plant habitat in a subtropical region (Florida, USA).

Designed ecosystems are built as part of ongoing urban expansion, providing a suite of valued ecosystem services. However, these new ecosystems could also promote disservices by facilitating the colonization and spread of invasive species. We conduct the first assessment of the quantity and invasion of an overlooked designed ecosystem: stormwater ponds. These ponds are commonly recommended for managing urban hydrology, but little is known about their ecology or extent of proliferation. Using a broad-scale survey of pond coverage in Florida, USA, we found that over 76,000 stormwater ponds have been built just in this state, forming 2.7% of total urban land cover. This extensive pondscape of manufactured habitats could facilitate species spread throughout urban areas and into nearby natural waterbodies. We also conducted a survey of the severity of plant invasion in 30 ponds in Gainesville, FL, US across two pond types (dry vs. wet), and a gradient of management intensities (low, medium, high) and pond ages. We unexpectedly found a high number of invasive plant species (28 in just 30 ponds). Ninety-six percent of surveyed ponds contained from one to ten of these species, with ponds exhibiting high turnover in invader composition (i.e., high beta diversity). The bank sections of dry unmanaged ponds exhibited the highest mean invasive species richness (5.8 ± 1.3) and the inundated centers of wet medium managed ponds exhibited the highest mean invasive species cover (34 ± 12%). Invasive plant richness and cover also tended to be greater in dry ponds with higher soil nutrient levels, and in older wet ponds. Therefore, we found that highly maintained and younger wet ponds were the least invaded. Nevertheless, common management practices that limit plant invasions may also limit native species establishment and invasion may increase in the decades following pond construction.

Limnological effects of a large Amazonian run-of-river dam on the main river and drowned tributary valleys.

Run-of-river dams are often considered to have lower environmental impacts than storage dams due to their smaller reservoirs and low potential for flow alteration. However, this has been questioned for projects recently built on large rivers around the world. Two of the world's largest run-of-river dams-Santo Antônio and Jirau-were recently constructed on the Madeira River, a major tributary to the Amazon River in Brazil. Here we evaluate the effects of the creation of the Santo Antônio dam on the water chemistry and thermal structure of the Madeira River mainstem and back-flooded valleys of tributaries within the reservoir inundated area. In contrast to the mainstem river, some back-flooded tributaries periodically developed thermal stratification, which is associated with higher water residence times. Additionally, biochemical oxygen demand, partial pressure of CO2, and organic carbon all increased in the tributary valleys inundated by the reservoir, possibly due to increased input of allochthonous organic matter and its subsequent mineralization upon back-flooding-a common feature of newly flooded impoundments. The mainstem did not show detectable dam-related changes in water chemistry and thermal structure. Although the majority of the reservoir area maintained riverine conditions, the lateral valleys formed upon back-flooding-corresponding to ~30% of the Santo Antônio reservoir area-developed lake-like conditions akin to a typical reservoir of a storage dam.

Seeing the light: urban stream restoration affects stream metabolism and nitrate uptake via changes in canopy cover.

The continually increasing global population residing in urban landscapes impacts numerous ecosystem functions and services provided by urban streams. Urban stream restoration is often employed to offset these impacts and conserve or enhance the various functions and services these streams provide. Despite the assumption that "if you build it, [the function] will come," current understanding of the effects of urban stream restoration on stream ecosystem functions are based on short term studies that may not capture variation in restoration effectiveness over time. We quantified the impact of stream restoration on nutrient and energy dynamics of urban streams by studying 10 urban stream reaches (five restored, five unrestored) in the Baltimore, Maryland, USA, region over a two-year period. We measured gross primary production (GPP) and ecosystem respiration (ER) at the whole-stream scale continuously throughout the study and nitrate (NO3- -N) spiraling rates seasonally (spring, summer, autumn) across all reaches. There was no significant restoration effect on NO3- -N spiraling across reaches. However, there was a significant canopy cover effect on NO3- -N spiraling, and directly comparing paired sets of unrestored-restored reaches showed that restoration does affect NO3- -N spiraling after accounting for other environmental variation. Furthermore, there was a change in GPP : ER seasonality, with restored and open-canopied reaches exhibiting higher GPP : ER during summer. The restoration effect, though, appears contingent upon altered canopy cover, which is likely to be a temporary effect of restoration and is a driver of multiple ecosystem services, e.g., habitat, riparian nutrient processing. Our results suggest that decision-making about stream restoration, including evaluations of nutrient benefits, clearly needs to consider spatial and temporal dynamics of canopy cover and trade-offs among multiple ecosystem services.

High mortality in aquatic predators of mosquito larvae caused by exposure to insect repellent.

In the face of mosquito-borne disease outbreaks, effective mosquito control is a primary goal for public health. Insect repellents, containing active compounds such as DEET and picaridin, are a first defence against biting insects. Owing to widespread use and incomplete sewage treatment, these compounds are frequently detected in surface waters, but their effects on aquatic taxa such as mosquito larvae or their naturally occurring aquatic predators are poorly understood. We investigated the effects of environmentally realistic concentrations of commercial products containing DEET and picaridin on survivorship of mosquito larvae, and their potential indirect effects on survival of larval salamanders, a major predator of mosquito larvae. Larval mosquitos were not affected by exposure to repellents containing DEET or picaridin. We found no larval salamander mortality in control and DEET treatments, but mortality rates in picaridin treatments ranged from 45 to 65% after 25 days of exposure. Salamander larvae exposed to repellents containing picaridin began to display tail deformities and impaired development four days after the experiment began. Our findings suggest the possibility that environmentally realistic concentrations of picaridin-containing repellents in surface waters may increase the abundance of adult mosquitos owing to decreased predation pressure.

Nitrogen cycling process rates across urban ecosystems.

Nitrogen (N) pollution of freshwater, estuarine, and marine ecosystems is widespread and has numerous environmental and economic impacts. A portion of this excess N comes from urban watersheds comprised of natural and engineered ecosystems which can alter downstream N export. Studies of urban N cycling have focused on either specific ecosystems or on watershed-scale mass balances. Comparisons of specific N transformations across ecosystems are required to contextualize rates from individual studies. Here we reviewed urban N cycling in terrestrial, aquatic, and engineered ecosystems, and compared N processing in these urban ecosystem types to native reference ecosystems. We found that net N mineralization and net nitrification rates were enhanced in urban forests and riparian zones relative to reference ecosystems. Denitrification was highly variable across urban ecosystem types, but no significant differences were found between urban and reference denitrification rates. When focusing on urban streams, ammonium uptake was more rapid than nitrate uptake in urban streams. Additionally, reduction of stormwater runoff coupled with potential decreases in N concentration suggests that green infrastructure may reduce downstream N export. Despite multiple environmental stressors in urban environments, ecosystems within urban watersheds can process and transform N at rates similar to or higher than reference ecosystems.