Human Influence Past and Present – Relationship of Nutrient and Hydrologic Conditions to Urban Wetland Macrophyte Distribution

Urban wetlands can provide valuable ecological services through filtration and moderation of non-point source pollutants. They provide habitat for wildlife, green space, and recreational opportunities for nearby human populations. We investigated an isolated section of an urban wetland in the Cleveland metropolitan area to determine the overall quality of the vegetation and to evaluate the site for possible rehabilitation. We also researched the distribution of plant species in relation to existing hydrologic, soil, and nutrient conditions in order to identify possible impacts of historic or present human activities in the surrounding watershed. Vegetation composition and physical/chemical parameters were measured in 1.0 × 1.0 m plots along three transects. Canonical correspondence analysis (CCA) was used to directly correlate species distributions to nutrient concentrations, soil carbon content, and water depth. Our sample area was dominated by Typha angustifolia, Leersia oryzoides, and Sparganium eurycarpum. A few high quality species were present, but the overall macrophyte community was indicative of human disturbance. Historic information revealed a long history of disturbance at the site and continuing anthropogenic impact. Patchiness in nutrient and water depth gradients results from historic and current human impacts in the study area. Our results indicate any rehabilitation efforts of the site need to take into account past and current anthropogenic stressors. We recommend aggressive removal of invasive species and re-introduction of nutrient-tolerant native taxa to achieve successful rehabilitation at the site. OHIO J SCI 105 (5):125-132, 2005 Manuscript received 8 March 2004 and in revised form 18 February 2005 (#04-07). Corresponding Author INTRODUCTION The value of wetlands in mediating and processing watershed inputs is well known. They provide valuable ecological services including groundwater recharge and water quality improvement, as well as providing fish and wildlife habitat (for example, Mitsch and Gosselink 2000). More than 90% of Ohio’s wetlands have been lost as a result of human related activities (Dahl 1990). It is, therefore, all the more important that we work to rehabilitate and restore those wetlands that remain. Present day urban wetlands are particularly vulnerable to loss. They often function differently as a result of surrounding land-use practices that alter hydrology and increase nutrient inputs. Many of these wetlands are small, isolated ‘islands’ in the urban landscape. Often they are perceived of as ‘disposable’ or of little significance. However, they contribute to the ecological integrity and biodiversity of the regional landscape by providing stopover spaces or refugia for migrating and regional wildlife. Additionally, in contrast to their rural counterparts, urban wetlands provide human-related services such as green space and recreational opportunities that otherwise are limited in urban environments (Ehrenfeld 2000). Lake Abram, Cuyahoga County, OH (41.3789 ̊ N, 81.8388 ̊ W) lies in the Rocky River catchment and is surrounded by extensive wetlands, the majority of which lie south and west of the lake (Fig. 1). The site is a recent acquisition of the Cleveland Metro Park system. Once part of the extensive Podunk Swamp, the wetland has shrunk from an original size of several hundred acres to a mere 80 acres at present due to extensive human modification and increased urbanization. Despite this loss, it remains the largest natural wetland in Cuyahoga County. Lake Abram and its surrounding wetland lie in a glacial kettle. It is categorized as a riparian, kettle lake, depressional wetland (Mack and others 2000). Today, the wetland is surrounded on all sides by varying amounts of residential, commercial, and industrial development. Land-use impacts on wetlands may manifest themselves through changes in plant communities, altered