skip to main content


The NSF Public Access Repository (NSF-PAR) system and access will be unavailable from 11:00 PM ET on Friday, July 12 until 2:00 AM ET on Saturday, July 13 due to maintenance. We apologize for the inconvenience.

Title: Emerging investigator series: interacting effects of environmental factors on Daphnia magna removal of Escherichia coli from wastewater
Treatment wetlands can remove a wide range of pollutants from wastewater and stormwater runoff, including microbial pollutants such as Escherichia coli . Filter feeding zooplankton play an important role in improving water quality in treatment wetlands through grazing and subsequent inactivation of E. coli . Understanding how climate change will impact the various processes governing microbial inactivation in treatment wetlands is essential to ensure adequately treated water. We investigated the impact of interacting environmental factors on the E. coli clearance rate of a keystone zooplankton species, Daphnia magna . We utilized a full factorial experimental design to test the impacts of food abundance, food type, and temperature in flow-through mesocosms under environmentally relevant conditions. Temperature and food abundance interactions were significant, which highlights the importance of studying multiple environmental variables when considering the filter feeding contributions of zooplankton. While both food abundance and temperature had a significant impact on clearance rate, daphnids did not exhibit a preference between algae or E. coli , which were the two food sources used in our studies. We observed that at 25 °C, food abundance and type had a larger impact on E. coli clearance rate than at 15 °C, which has important implications when considering resiliency of treatment wetlands in a warming climate. Our findings show that zooplankton filtration behavior will be impacted by environmental conditions that are projected due to climatic changes, but populations can still inactivate E. coli and improve water quality when exposed to these conditions.  more » « less
Award ID(s):
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Environmental Science: Water Research & Technology
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ABSTRACT The fecal indicator bacterial species Escherichia coli is an important measure of water quality and a leading cause of impaired surface waters. We investigated the impact of the filter-feeding metazooplankton Daphnia magna on the inactivation of E. coli . The E. coli clearance rates of these daphnids were calculated from a series of batch experiments conducted under variable environmental conditions. Batch system experiments of 24 to 48 h in duration were completed to test the impacts of bacterial concentration, organism density, temperature, and water type. The maximum clearance rate for adult D. magna organisms was 2 ml h −1 organism −1 . Less than 5% of E. coli removed from water by daphnids was recoverable from excretions. Sorption of E. coli on daphnid carapaces was not observed. As a comparison, the clearance rates of the freshwater rotifer Branchionus calyciflorus were also calculated for select conditions. The maximum clearance rate for B. calyciflorus was 6 × 10 −4  ml h −1 organism −1 . This research furthers our understanding of the impacts of metazooplankton predation on E. coli inactivation and the effects of environmental variables on filter feeding. Based on our results, metazooplankton can play an important role in the reduction of E. coli in natural treatment systems under environmentally relevant conditions. IMPORTANCE Escherichia coli is a fecal indicator bacterial species monitored by the U.S. Environmental Protection Agency to assess microbial water quality. Due to the potential human health implications linked to high levels of E. coli , it is important to understand the inactivation or reduction mechanisms in surface waters. Our research examines the capacities of two types of widespread filter-feeding freshwater metazooplankton, Daphnia magna and Brachionus calyciflorus , to reduce E. coli concentrations. We examine the impacts of different environmentally relevant conditions on the clearance rates. Our results contribute to a better understanding of the importance of metazooplankton in controlling E. coli concentrations and what conditions will reduce or increase grazing. These results provide baseline data to support future efforts to develop a quantitative model relating zooplankton uptake rates to relevant environmental variables. 
    more » « less
  2. Dudley, Edward G. (Ed.)
    Oysters play an important role in coastal ecology and are a globally popular seafood source. However, their filter-feeding lifestyle enables coastal pathogens, toxins, and pollutants to accumulate in their tissues, potentially endangering human health. While pathogen concentrations in coastal waters are often linked to environmental conditions and runoff events, these do not always correlate with pathogen concentrations in oysters. Additional factors related to the microbial ecology of pathogenic bacteria and their relationship with oyster hosts likely play a role in accumulation but are poorly understood. In this study, we investigated whether microbial communities in water and oysters were linked to accumulation of Vibrio parahaemolyticus, Vibrio vulnificus, or fecal indicator bacteria. Site-specific environmental conditions significantly influenced microbial communities and potential pathogen concentrations in water. Oyster microbial communities, however, exhibited less variability in microbial community diversity and accumulation of target bacteria overall and were less impacted by environmental differences between sites. Instead, changes in specific microbial taxa in oyster and water samples, particularly in oyster digestive glands, were linked to elevated levels of potential pathogens. For example, increased levels of V. parahaemolyticus were associated with higher relative abundances of cyanobacteria, which could represent an environmental vector for Vibrio spp. transport, and with decreased relative abundance of Mycoplasma and other key members of the oyster digestive gland microbiota. These findings suggest that host and microbial factors, in addition to environmental variables, may influence pathogen accumulation in oysters. 
    more » « less
  3. We introduce the facile one-step biosynthesis of a bilayer structured hydrogel composite of reduced-graphene oxide (rGO) and bacterial nanocellulose (BNC) for multiple photothermal water treatment applications. One-step in situ biosynthesis of a bilayered hydrogel was achieved via modification of BNC growth medium supplemented with an optimized concentration of corn steep liquor as a growth enhancer. A two-stage, growth rate-controlled formation mechanism for the bilayer structure was revealed. The final cleaned and freeze-dried reduced-GO embedded BNC bilayer membrane enables versatile applications such as filtration (tested using gold nanoparticles, Escherichia coli cells, and plasmid DNA), photothermal disinfection of entrapped E. coli , and solar water evaporation. Comparable particle rejection (up to ≈4 nm) and water flux (146 L h −1 m −2 ) to ultrafiltration were observed. Entrapment and photothermal inactivation of E. coli cells were accomplished within 10 min of solar exposure (one sun). Such treatment can potentially suppress membrane biofouling. The steam generation capacity was 1.96 kg m −2 h −1 . Our simple and scalable approach opens a new path for biosynthesis of nanostructured materials for environmental and biomedical applications. 
    more » « less
  4. The planktonic copepod Calanus finmarchicus is a fundamental prey resource for the critically endangered North Atlantic right whale Eubalaena glacialis . Incorporation of prey information into E. gla cialis decision support tools could improve management. Zooplankton time series are usually analyzed with respect to abundance, but predators such as E. glacialis forage based on whether prey aggregations exceed energetic thresholds. In order to better understand the distribution and dynamics of the high-abundance end of C. finmarchicus on the northeastern US continental shelf, where E. glacialis feed, we modeled the environmental conditions associated with C. finmarchicus densities that exceed nominal feeding thresholds. Threshold values were chosen based on a review of E. glacialis feeding behavior throughout the domain. Following model selection procedures, we used a random forest model with bathymetry, bottom temperature, bottom salinity, day of year, sea surface temperature, sea surface temperature gradient, bathymetric slope, time-integrated chlorophyll, current velocity gradient, and wind covariates. Model performance was highest with thresholds that matched reported E. glacialis feeding thresholds equivalent to 10000 copepods m -2 . The high-density aggregations of C. finmarchicus had some different covariate responses compared to previous statistical abundance models, such as a warmer temperature range at both the surface and at depth, as well as a much higher degree of spatial variability. The output data layers of the model are designed to link with E. glacialis models used in US governmental decision support tools. Including this type of foraging information in decision support tools is a step forward in managing this critically endangered species. 
    more » « less
  5. Abstract

    Microbial mortality impacts the structure of food webs, carbon flow, and the interactions that create dynamic patterns of abundance across gradients in space and time in diverse ecosystems. In the oceans, estimates of microbial mortality by viruses, protists, and small zooplankton do not account fully for observations of loss, suggesting the existence of underappreciated mortality sources. We examined how ubiquitous mucous mesh feeders (i.e. gelatinous zooplankton) could contribute to microbial mortality in the open ocean. We coupled capture of live animals by blue‐water diving to sequence‐based approaches to measure the enrichment and selectivity of feeding by two coexisting mucous grazer taxa (pteropods and salps) on numerically dominant marine prokaryotes. We show that mucous mesh grazers consume a variety of marine prokaryotes and select between coexisting lineages and similar cell sizes. We show thatProchlorococcusmay evade filtration more than other cells and that planktonic archaea are consumed by macrozooplanktonic grazers. Discovery of these feeding relationships identifies a new source of mortality for Earth's dominant marine microbes and alters our understanding of how top‐down processes shape microbial community and function.

    more » « less