Relationship between instream habitat characteristics, emergent insects, and riparian bird communities

Streams and riparian areas can be intricately connected via physical and biotic interactions that influence habitat conditions and supply resource subsidies between these ecosystems. Streambed characteristics such as the size of substrate particles influence the composition and the abundance of emergent aquatic insects, which can be an important resource for riparian breeding birds. We predict fine sediment abundance in small headwater streams directly affects the composition and number of emergent insects while it may indirectly affect riparian bird assemblages. Streams with abundant fine sediments that embed larger substrates should have lower emergence of large insects such as phemeroptera, Plecoptera and Trichoptera. Streams with lower emergent insect abundance are predicted to support fewer breeding birds and may lack certain bird species that specialize on aquatic insects. This study examined relationships between streambed characteristics, and emergent insects (composition, abundance and biomass), and riparian breeding birds (abundance and richness) along headwater streams of the Otter River Watershed. The stream bed habitats of seven stream reaches were characterized using longitudinal surveys. Malaise traps were deployed to sample emergent aquatic insects. Riparian breeding birds were surveyed using fixed-radius point-counts. Streams differed within a wide range of fine sediment abundances. Total emergent aquatic insect abundance increased as coverage by instream substrates increased in diameter, while bird community was unresponsive to insect or stream features. Knowledge of stream and riparian relationships is important for understanding of food webs in these ecosystems, and it is useful for riparian forest conservation and improving land-use management to reduce sediment pollution in these systems.

Impact of copper mine tailings (stamp sand) on survival and development of aquatic organisms near Gay, Michigan

Heavy metal-rich copper mine tailings, called stamp sands, were dumped by mining companies directly into streams and along the Lake Superior shoreline, degrading Keweenaw Peninsula waterways. One of the largest disposal sites is near Gay, Michigan, where tailings have been moved along the shoreline by currents since mining ceased. As a result, the smallest sand particles have been washed into deeper water and are filling the interstitial spaces of Buffalo Reef, a critical lake trout spawning site. This research is the first to investigate if stamp sand is detrimental to survival and early development of eggs and larvae of lake sturgeon, lake trout, and Northern leopard frogs, and also examines if the presence of stamp sands influences substrate selection of earthworms. This study found that stamp sand had significantly larger mean particle sizes and irregular shapes compared to natural sand, and earthworms show a strong preference for natural substrate over any combination that included stamp sand. Additionally, copper analysis (Cu2+) of surface water over stamp sand and natural sand showed concentrations were significantly higher in stamp sand surface water (100 μg/L) compared to natural sand surface water (10 μg/L). Frog embryos had similar hatch success over both types of sand, but tadpoles reared over natural sand grew faster and had higher survival rates. Eggs of lake sturgeon showed similar hatch success and development over natural vs. stamp sand over 17 days, while lake trout eggs hatched earlier and developed faster when incubated over stamp sand, yet showed similar development over a 163 day period. Copper from stamp sand appears to impact amphibians more than fish species in this study. These results will help determine what impact stamp sand has on organisms found throughout the Keweenaw Peninsula which encounter the material at some point in their life history.