Biomass Turnover Rates of Snag Chironomid Larvae in a Second Order Stream of Middle China

ABSTRACT

During June 2003 to June 2004, annual production and Production/Biomass (P/B) ratios were estimated for the larval chironomid assemblage found on the submerged branches and leaves (snag) of Heizhuchong Stream, a second order river of Hanjiang River basin, China. Temperature-specific growth rate equations from field growth studies were applied to the biomass values from quantitative field samples to obtain mean daily production on a monthly basis throughout the year. The annual production of the filtering collector Rheotanytarsus spp. was 32.1g'm⁻²'y ⁻¹ for snag surface area, and productions for the gathering collectors Polypedilum spp. and Rheocricotopus spp. were 10.9 g'm⁻²'y⁻¹ and g'm⁻²'y⁻¹, respectively. These production estimates are among the highest ones ever reported for chironomids in freshwater ecosystems, mainly owing to extremely high P/B ratios. Annual PB ratios were 177 for Rheocricotopus spp., 261 for Polypedilum spp. and 194 for Rheotanytarsus spp.