The Effect of Environmental Muck Dredging on Abundance and Community Richness of Benthic Amphipods in the Indian River Lagoon

Abstract

Anthropogenic eutrophication has polluted and degraded estuarine ecosystems throughout the world. The Indian River Lagoon (IRL), a diverse North American estuary, has accumulated an abundance of Fine-Grained Organic-Rich Sediments (FGORS or “muck”) due to eutrophication. Muck creates stressful, sometimes uninhabitable conditions for benthic flora and fauna, with far-reaching ancillary ecosystem impacts. In an attempt to ameliorate negative ecosystem impacts, muck deposits in Turkey Creek were dredged by Brevard County Natural Resources (Florida). One month after the dredging, mean abundance of amphipods rose to 110±90 individuals m-2 from 0±0 individuals m-2 in the dredged muck sites. Four amphipod species colonized muck following dredging, and Cymadusa compta persisted one year after the dredging. Spatial difference in community richness was observed between intermediate sites. Lagoon sites, with less organic content and not directly impacted by dredging, registered high amphipod abundance (maximum: 4400±800 individuals m-2 ) compared to muck sites (maximum: 110±90 individuals m-2 ). Sediment characteristics (organic matter, water weight and silt-clay) and dissolved oxygen (DO) explained most of the variability of amphipod abundance. A distinct amphipod community was observed one year after the dredging. Colonization by amphipods in the sites hit by the dredge shows the promise of Environmental Muck Dredging as a potential technique for restoring benthic habitat in sites with extreme sediment organic content. Long-term monitoring is recommended to better understand Environmental Muck Dredging’s success in benthic habitat restoration.