Comparison of Microbial Functional Diversity Associated with Artificial Wetlands in an Urbanized River System
Location
SU 214
Department
Biology
Abstract
Decades of anthropogenic forces have permanently altered the ability of urban river systems to support diverse, robust ecosystems. The Chicago River, which flows through most of urban Chicago, is both impaired in its ability to support diverse native communities, and uniquely positioned to be restored through a combination of technology and urban redevelopment. Artificial Floating Wetlands (AFWs) are a relatively new technology that provides habitat and connectivity between urban aquatic and terrestrial environments, features generally lacking in heavily channelized urban river systems. While there is existing research that has focused on the ability of AFWs to treat and filter wastewater, there is a stark lack of research based on the ecological value of these AFWs in urbanized ecosystems. This study assesses the ecological value provided by AFWs to critical components of stream food webs by measuring the differences in functional diversity of microbial communities near planted AFWs versus open river areas, which are lined predominantly with seawall and little vegetation. In June of 2017, the non-profit Urban Rivers installed ~1500 square feet of AFWs in the Chicago River, planted with over 50 native Illinois wetland and prairie plant species. In June of 2018, smaller sets of AFWs were installed in four large mesocosm tanks at the Chicago Botanic Garden. The mesocosm tanks were each filled with 1000 gallons of water drawn directly from the Chicago River. The AFWs in two tanks were left unplanted, while the other two were planted with 20 individuals of 4 different plant species each. Water samples were gathered from directly beneath the AFWs, both in the field and in mesocosms, and at locations at least 10 m away from the AFWs. These samples were then used to inoculate 96-well Biolog EcoPlates. After a 48-hour incubation period, we measured absorbance of wells in EcoPlates at 590 nm in order to determine average well color development (AWCD). AWCD is a metric used to indicate changes in microbial functional diversity based on the differences in the utilization of unique carbon-based substrates within each well of the EcoPlates. Darker color development (higher absorbance values at 590 nm) indicates a greater utilization of the substrate than do lighter colors. Results from the first sampling event (October 2018) revealed that AWCD differed between locations in the field directly adjacent to the AFWs versus locations that were not near AFWs. Samples taken directly below AFWs utilized anywhere from 64.52% to 74.19% of substrates in the EcoPlates, with an average of 70.25%. Samples taken at least 10 m away from AFWs utilized from 45.16% to 61.29% of substrates, with an average of 54.3%. Our results suggest that the presence of more diverse structures in the water column, such as AFWs, might allow for greater functional diversity in microbial communities compared to areas of the river without such substrate complexity. Because microbial communities are directly linked to ecosystem processes, the presence of AFWs may also translate into increased ecosystem functioning.
Comparison of Microbial Functional Diversity Associated with Artificial Wetlands in an Urbanized River System
SU 214
Decades of anthropogenic forces have permanently altered the ability of urban river systems to support diverse, robust ecosystems. The Chicago River, which flows through most of urban Chicago, is both impaired in its ability to support diverse native communities, and uniquely positioned to be restored through a combination of technology and urban redevelopment. Artificial Floating Wetlands (AFWs) are a relatively new technology that provides habitat and connectivity between urban aquatic and terrestrial environments, features generally lacking in heavily channelized urban river systems. While there is existing research that has focused on the ability of AFWs to treat and filter wastewater, there is a stark lack of research based on the ecological value of these AFWs in urbanized ecosystems. This study assesses the ecological value provided by AFWs to critical components of stream food webs by measuring the differences in functional diversity of microbial communities near planted AFWs versus open river areas, which are lined predominantly with seawall and little vegetation. In June of 2017, the non-profit Urban Rivers installed ~1500 square feet of AFWs in the Chicago River, planted with over 50 native Illinois wetland and prairie plant species. In June of 2018, smaller sets of AFWs were installed in four large mesocosm tanks at the Chicago Botanic Garden. The mesocosm tanks were each filled with 1000 gallons of water drawn directly from the Chicago River. The AFWs in two tanks were left unplanted, while the other two were planted with 20 individuals of 4 different plant species each. Water samples were gathered from directly beneath the AFWs, both in the field and in mesocosms, and at locations at least 10 m away from the AFWs. These samples were then used to inoculate 96-well Biolog EcoPlates. After a 48-hour incubation period, we measured absorbance of wells in EcoPlates at 590 nm in order to determine average well color development (AWCD). AWCD is a metric used to indicate changes in microbial functional diversity based on the differences in the utilization of unique carbon-based substrates within each well of the EcoPlates. Darker color development (higher absorbance values at 590 nm) indicates a greater utilization of the substrate than do lighter colors. Results from the first sampling event (October 2018) revealed that AWCD differed between locations in the field directly adjacent to the AFWs versus locations that were not near AFWs. Samples taken directly below AFWs utilized anywhere from 64.52% to 74.19% of substrates in the EcoPlates, with an average of 70.25%. Samples taken at least 10 m away from AFWs utilized from 45.16% to 61.29% of substrates, with an average of 54.3%. Our results suggest that the presence of more diverse structures in the water column, such as AFWs, might allow for greater functional diversity in microbial communities compared to areas of the river without such substrate complexity. Because microbial communities are directly linked to ecosystem processes, the presence of AFWs may also translate into increased ecosystem functioning.
Comments
Pamela Geddes is the faculty sponsor of this project.