Spatial Colonization of Aquatic Macroinvertebrates in Small Streams in the Barrenlands Tundra near Lac De Gras, Northwest Territories, Canada

Aquatic macroinvertebrates are an integral part of stream ecosystems. While this community is well studied in temperate regions, it is much less so at high latitudes, such as on the Arctic tundra.  The Barrenlands region of northern Canada is likely to undergo significant environmental changes as a result of global climate change and increased exploration in the region; therefore, it is important to study the ecosystems before they are altered beyond their natural state. 

Because small arctic streams freeze solid during the winter months, one important component to their functioning is how arctic macroinvertebrates recolonize each year.  To determine the relative importance of different modes of colonization by macroinvertebrates, we placed colonization boxes made from Plexiglas or wood in seven Barrenlands streams in the greater Lac de Gras catchment.  Four types of boxes, each open to only one mode of colonization (upstream, downstream, hyporheic, and aerial) were placed in the streams, along with open and closed control boxes.  Boxes were placed into the streams in pairs immediately following freshet and left for four weeks to ensure that macroinvertebrates had ample opportunity to colonize each type of box.  The boxes were then removed and the all substrates were scrubbed to remove all organisms inside the boxes.  Organisms were preserved within individual containers for later counting and identification down to at least family level.  Surber samples showed that stream communities were dominated by dipterans, especially chironomids and simuliids, but also contained crustaceans, trichopterans, plecopterans, ephemeropterans, coleopterans, oligochaetes, molluscs, and hydrachnidians.  Our closed control boxes succeeded in allowing only a few larval dipterans to colonize the boxes, along with few crustaceans. Conversersly, open control boxes contained large numbers of taxa.  Among the colonization boxes, aerial traps had the fewest taxa while downstream boxes had the most.  Knowing how macroinvertebrates colonize their habitat will help us understand how this community may be affected by the many changes the Barrenlands region can expect due to increased air and water temperatures, treeline expansion, and manipulation due to resource extraction.