LINKAGE BETWEEN ISLANDS AND BENTHOS IN THE OHIO RIVER, WITH IMPLICATIONS FOR RIVERINE MANAGEMENT

Anthropogenic reductions in braiding, meandering, and snag abundance have diminished habitat heterogeneity of regulated rivers, factors directly influencing island formation, retentive capacity of the ecosystem, and community diversity. Habitat heterogeneity associated with riverine islands should, therefore, be of paramount importance to the ecosystem and may require special management protection. To understand the influence of these alluvial formations on riverine benthos, macroinvertebrate assemblages were sampled near three islands in the Ohio River above Louisville, Kentucky, USA. Benthos was collected along six bank-to-bank transects located 1 km above and below islands and near the head, middle, and foot of islands. Islands have significant positive effects on invertebrate density and diversity that appear related to changes in physical habitat characteristics. Current velocity and substrate particle size are diminished in narrow channels between islands and shore, and areal extent of the littoral zone is enhanced within an otherwise deepwater region. Shallow water and slower currents promote growth of submerged vascular plants and macrophytic algae. Because of a relatively low exploitation by humans, islands probably enhance snag formation and input of organic matter, both factors having positive effects on macrofauna. Creation of selected riverine preserves near islands as a management tactic is recommended.