Biology subjects

Rooney, R. C.

Publications and source records attributed to Rooney, R. C..

3 recordsLinked to original sources

bioRxiv2020

Bioconcentration of glyphosate in wetland biofilms

Wetland biofilms were exposed to the herbicide glyphosate via in situ field exposures and controlled microcosm experiments to measure bioconcentration and metabolism of glyphosate by biofilm organisms. Glyphosate concentrations in biofilms were orders of magnitude higher than the surrounding water, bioconcentration factors averaged 835 and 199 in field- and lab-exposed biofilms, respectively. Glyphosate in water where it had been detected in biofilms at field-exposed sites ranged from below detection (<0.001 ppm) up to 0.13 ppm. Glyphosate bioconcentration in biofilms was inversely proportional to levels in the surrounding water, and the retention kinetics were similar to both adsorption and enzymatic models. Microorganisms present in both the water and biofilms metabolized glyphosate to its primary breakdown product aminomethyl phosphonic acid (AMPA), with increased rates of breakdown in and around the biofilms. Photosynthetic efficiency of the algae within the biofilms was not affected by 24 h glyphosate controlled exposures. Our results demonstrate the role of biofilms in improving wetland water quality by removing contaminants like glyphosate, but also as a potential exposure route to higher trophic levels via consumption. Due to bioconcentration of pesticides, exposure risk to organisms consuming or living in biofilms may be much higher than indicated by concentrations in ambient water samples.

ecology↗

bioRxiv2020

Functional dispersion of wetland birds, invertebrates and plants more strongly influenced by hydroperiod than each other

The relative role of biological and abiotic filters on the assembly of co-occurring taxa is widely debated. While some authors point to biological interactions (e.g., competition) as the stronger driver of ecological selection, others assert that abiotic conditions are more important because they filter species at the regional level. Because communities influenced by a dominant abiotic filter, (e.g., Prairie Pothole Region (PPR) wetlands, each varying in ponded water permanence), often have strong cross-taxon relationships, we can study these communities to better understand the relative influence of abiotic vs biotic filters on community structure. Using functional dispersion as our measure of communities, we test six alternate hypotheses about the relative importance of various pathways representing influence of biological and permanence filters on birds, aquatic macroinvertebrates and wetland plants in the northwest PPR using structural equation modeling. We aimed to understand whether: 1) ponded water permanence alone explained functional dispersion; 2) the influence of permanence on functional dispersion was direct or mediated; and 3) abiotic filtering by permanence was stronger than biotic filtering by co-occurring taxa. The best model suggests that there is a direct influence of permanence on the functional dispersion of each taxonomic group and that both bird and macroinvertebrate functional dispersion are causally related to plant functional dispersion, though for invertebrates the influence of plants is much less than that of permanence. Thus, the relative importance of wetland permanence and the functional dispersion of co-occurring taxa depends on which taxon is considered in PPR wetlands.

ecology↗

bioRxiv2020

Suppression of established invasive Phragmites australis leads to secondary invasion

Invasive Phragmites australis (European Common Reed) is rapidly spreading throughout North American wetlands, with negative impacts on wildlife and native plants. The removal or suppression of P. australis is desired to provide an opportunity for native vegetation and wetland fauna to recover. In Ontario, managers applied a glyphosate-based herbicide to >400 ha of P. australis in ecologically significant Great Lakes coastal marshes, representing the first time this tool was used over standing water to suppress P. australis in Canada. Using a replicated Before-After-Control-Impact monitoring design, we 1) evaluated the efficacy of glyphosate-based herbicide at suppression P. australis along a water depth gradient and 2) assessed the recovery of the vegetation community for two years after treatment in relation to local reference conditions. We found that herbicide reduced live P. australis stem densities by over 99% the first year after treatment and about 95% the second year post-treatment. Treatment was equally effective along the entire water depth gradient (10 - 48 cm). The initial suppression focused management was successful, but sustained monitoring and containment focused follow-up treatment will be required to prevent reinvasion. Two years after treatment, the vegetation community does not resemble reference conditions. Although some treated plots initially increased in similarity to the vegetation communities typical of reference areas, many plots where P. australis was suppressed are on a novel trajectory comprising a vegetation community dominated by non-native Hydrocharis morsus-ranae. Secondary invasions represent a major challenge to effective recovery of native vegetation after P. australis control.

ecology↗