Murray State University
Interspecific Competition of Hexagenia bilineata and Chironomus major in Kentucky Lake, Kentucky
Institution
Murray State University
Faculty Advisor/ Mentor
David White
Abstract
Benthic (bottom dwelling) organisms are a major component of the food web in lakes. They not only act as food for higher levels (e.g., for fish), but also recycle carbon and nutrients back into the water column (Edsall 2001). These organisms are important in trophic dynamics and can be reliable indicators of ecosystem health using biomass and production estimates. Hexagenia bilineata (the burrowing mayfly) is a dominant and conspicuous component of the benthos in Kentucky Lake and other Midwestern reservoirs (Wetzel 2001, Ramsey et al. submitted). Over the past 20 years, a second species, Chironomus major (burrowing midge) has become very abundant in Kentucky Lake but not in other Midwestern reservoirs (Balci et al. 2005). Ramsey et al. (submitted) have shown that Hexagenia bilineata contributes less to overall benthic energy flow in Kentucky Lake (185 mg¯² yr¯¹) than would be expected compared with previously studied reservoirs and lakes. They attributed this low production to possible interspecific interference competition with the large-bodied Chironomus major. Hexagenia build residential “U” shaped burrows. The burrows may extend 10-15 cm deep into the bottom muds. Hexagenia gills are in constant motion bringing water and food through the burrow. The similar sized Chironomus major (up to 6 cm long) does not build a residential burrow, but instead is constantly moving through the sediments creating 8-20 cm long vertically oriented burrows. Ramsey et al. (submitted) have speculated that of Chironomus major may interfere with the hydraulic functioning of Hexagenia burrows if they happened to intersect, limiting the distribution of Hexagenia to less productive habitats along the margins of the lake shore where Chironomus major does not occur. Further, Chironomus major larvae may consume the eggs and young naiads in a situation similar to what Plant et al (2003) observed occurring between tube-dwelling chironomids and Hexagenia in Lake Erie. My research involves field and laboratory studies of the burrowing behavior of the two species to determine if interspecific competition is indeed occurring or if there are other factors contributing to lowered production of Hexagenia.
Interspecific Competition of Hexagenia bilineata and Chironomus major in Kentucky Lake, Kentucky
Benthic (bottom dwelling) organisms are a major component of the food web in lakes. They not only act as food for higher levels (e.g., for fish), but also recycle carbon and nutrients back into the water column (Edsall 2001). These organisms are important in trophic dynamics and can be reliable indicators of ecosystem health using biomass and production estimates. Hexagenia bilineata (the burrowing mayfly) is a dominant and conspicuous component of the benthos in Kentucky Lake and other Midwestern reservoirs (Wetzel 2001, Ramsey et al. submitted). Over the past 20 years, a second species, Chironomus major (burrowing midge) has become very abundant in Kentucky Lake but not in other Midwestern reservoirs (Balci et al. 2005). Ramsey et al. (submitted) have shown that Hexagenia bilineata contributes less to overall benthic energy flow in Kentucky Lake (185 mg¯² yr¯¹) than would be expected compared with previously studied reservoirs and lakes. They attributed this low production to possible interspecific interference competition with the large-bodied Chironomus major. Hexagenia build residential “U” shaped burrows. The burrows may extend 10-15 cm deep into the bottom muds. Hexagenia gills are in constant motion bringing water and food through the burrow. The similar sized Chironomus major (up to 6 cm long) does not build a residential burrow, but instead is constantly moving through the sediments creating 8-20 cm long vertically oriented burrows. Ramsey et al. (submitted) have speculated that of Chironomus major may interfere with the hydraulic functioning of Hexagenia burrows if they happened to intersect, limiting the distribution of Hexagenia to less productive habitats along the margins of the lake shore where Chironomus major does not occur. Further, Chironomus major larvae may consume the eggs and young naiads in a situation similar to what Plant et al (2003) observed occurring between tube-dwelling chironomids and Hexagenia in Lake Erie. My research involves field and laboratory studies of the burrowing behavior of the two species to determine if interspecific competition is indeed occurring or if there are other factors contributing to lowered production of Hexagenia.