Sediment Related Fluvial Transmission Of Contaminants

Author : Lindsey E. Boaz
Publisher :
ISBN 13 :
Total Pages : 193 pages
Book Rating : 4.:/5 (915 download)

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Download or read book Influences of Fluvial Geomorphology on Aquatic-to-terrestrial Hg Transport: Evidence from Protected and Urban Streams of Central Ohio, USA written by Lindsey E. Boaz and published by . This book was released on 2015 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluvial geomorphology is a driver of sediment supply and storage and may therefore affect the accessibility of sediment-bound mercury (Hg) to aquatic organisms, in addition to influencing aquatic food-web structure via physical habitat controls. In particular, benthic insects that in their larval form are aquatic but emerge into the terrestrial environment as winged adults have been shown to be both highly influenced by stream hydrogeomorphology as well as a vector of contaminant transport from aquatic-to-terrestrial systems. Therefore, the potential for fluvial geomorphology to influence both the aquatic-to-terrestrial export of Hg and the potential use of Hg as an aquatic-terrestrial food-web tracer is significant. I first evaluated Hg as a tracer for trophic structure and dynamics for linked stream-riparian systems under differing fluvial geomorphic conditions within a relatively protected watershed. To that end, I investigated potential differences in Hg dynamics and trophic structure between equilibrium (i.e., stable) and adjusting (i.e., unstable) stream reaches as well as the potential for Hg to model linked aquatic-terrestrial food webs at 20 stream-riparian study reaches in Big Darby Creek watershed (OH, USA). At each reach, I conducted geomorphic surveys and sampled sediment, water, benthic and emergent aquatic insects, darters (small, insectivorous stream fish), and two riparian spider families (Tetragnathidae and Pisauridae) for Hg and the stable isotopes 13C and 15N. I provide evidence that fluvial geomorphology may influence Hg availability and aquatic-terrestrial transport (via sediment storage and particle size). Although potential exists for the use of Hg as a food-web tracer, these factors - in addition to opportunistic feeding behavior among consumer groups - may mediate its effectiveness. I next evaluated the influences of fluvial geomorphology on aquatic-to-terrestrial Hg export across a gradient of geomorphic characteristics within an urbanized watershed, where the magnitude and ubiquity of geomorphic adjustment may be a controlling factor in Hg dispersal, bioaccumulation, and export across the aquatic-to-terrestrial boundary. In particular, I investigated the relationships between channel geometry, hydraulics, and amount of fine sediment and (1) Hg loads in sediment, larval, and emergent aquatic insects and (2) aquatic-to-terrestrial contaminant transfer to riparian spiders (Pisauridae and Tetragnathidae). Although fluvial geomorphic characteristics were not related to Hg loads in sediment or larval aquatic insects, I found significant relationships between fluvial geomorphic characteristics and pisaurid spider Hg levels. Fluvial geomorphic characteristics also significantly influenced emergent insect abundance and tended to influence tetragnathid spider Hg levels and emergent insect community composition. Collectively, these results indicate that fluvial geomorphology may be an important player in governing aquatic-to-terrestrial contaminant transport via both sediment dynamics and trophic linkages, although the exact nature of these relationships is likely to differ among systems. In the protected system of my study, fluvial geomorphology also appears to mediate the use of Hg as an aquatic-to-terrestrial food-web tracer through its effects on Hg accessibility and community structure, the latter of which is evidenced in family-level differences in Hg storage.