Linking substrate organic matter and water quality to invertebrate and fish populations within a constructed wetland treatment system

Abstract

The Orlando Easterly Wetlands is a highly engineered and managed free surface flow constructed wetland treatment system that was constructed for the expressed purpose of removing nitrogen and phosphorus from municipal reclaimed wastewater. The system has been in operation since 1987 and is managed and maintained for water quality. Through the 33 years of operation, the system has accumulated tremendous amounts of organic matter through natural wetland processes. However, this organic matter has caused significant short-circuiting of water flow ultimately leading to the need for removal. Removal of the organics is expensive and time-consuming and results in a complete renovation of the wetland marshes. These renovation projects effectively remove the organics along with the plants and wildlife species that inhabit a given project area. My paper aims to link water quality, accreted organic matter, and wildlife diversity and abundance. I theorized that biodiversity within the system is influenced and driven by the constant input of dissolved nutrients and the associated organic matter accretion. Through substrate samplers, dip netting, and minnow traps, aquatic biota was sampled and correlated with water quality indicators such as chlorophyll-a, carbonaceous biochemical oxygen demand, ammonia, ortho phosphate, total kjedahl nitrogen, total nitrogen, and total phosphorus along with the depths of organic matter. The abundance of macroinvertebrates was strongly correlated with carbonaceous biochemical oxygen demand (r2=0.91) and total nitrogen (r2=0.88). Ammonia displayed a moderate positive correlation and depths of the accreted organic matter were weakly correlated. The presence and abundance of larger more mobile aquatic species were moderately correlated with levels of chlorophyll-a (r2=0.702). OP and TP showed significant negative correlations (r2 = -0.619, -0.628), respectively. Suggesting that as OP and TP concentrations decrease abundance increases. I also document the rapid recolonization of invertebrates within newly renovated marshes in the Orlando Easterly Wetlands and how this system provides outstanding biodiversity.