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.

Wetland water quality assessment in cold and dry regions (Case study: Choghakhor wetland, Iran)

Wetlands are among the most productive ecosystems in the world. They provide numerous beneficial services for people and wildlife. The most important services are improving water quality and wildlife habitats. The complex, dynamic relationships between the organisms inhabiting the wetland environment are called food webs. Both water quality and high levels of nutrients are crucial for improvement of the food web. Many bird species rely on wetlands for food, water and shelter, especially during migration and breeding. The water quality of Choghakhor Wetland was evaluated from April 2010 to March 2011, by measuring some physicochemical parameters and doing benthic macroinvertebrate analysis. Sampling was done in 3 replicates with alternation of 45 days. The resolute was divided into more than 25 identified macroinvertebrate families which belonged to 5 classes and 12 orders. The correlation between biological indices and water quality parameters showed that bioindicators and community indices could be used for the evaluation of water quality in this wetland. The water quality of Choghakhor Wetland was classified as average or in the severe pollution class, according to these indices. It can be concluded that bird migration is at risk due to the decline in the overall health of the Choghakhor Wetland ecosystem.

Enhancement of Agricultural Policy/Environment eXtender Model (APEX) Model to Assess Effectiveness of Wetland Water Quality Functions

The Agricultural Policy/Environmental eXtender (APEX) model has been widely used to assess changes in agrochemical loadings in response to conservation and management led by US Department of Agriculture (USDA). However, the existing APEX model is limited in quantification of wetland water quality functions. This study improved the current model capacity to represent wetland water quality functions by addition of a new biogeochemical module into the APEX model. The performance of an enhanced APEX model was tested against five observed outgoing water quality variables (e.g., sediment, organic N, NO3, NH4 and PO4) from a wetland within the Eastern Shore of Maryland. Generalized Likelihood Uncertainty Estimation (GLUE) was implemented to assess model uncertainty. The enhanced APEX model demonstrated that it could effectively represent N and P cycling within the study wetland. Although improvement of model performance was limited, the additions of wetland biogeochemical routines to the APEX model improved our understanding of inner mass exchanges within N and P cycling for the study wetland. Overall, the updated APEX model can provide policymakers and managers with improved means for assessment of benefits delivered by wetland conservation.