Modeling sinking rate of zooplankton carcasses: Effects of stratification and mixing

Abstract

Using the carcass sinking rate and density determined in laboratory for several freshwater zooplankton species, we developed a model of zooplankton carcass sinking as affected by turbulence and stratification. The model was subsequently used to estimate the residence time of zooplankton carcasses in the water column of Lake Stechlin, a typical temperate dimictic lake in northeastern Germany. The residence time varied among the different species and was strongly affected by thermal stratification. At the peak of summer stratification, the carcasses stayed up to 5 d in the 70 m-deep water column before reaching the lake bottom. Residence time was long enough that zooplankton carcasses could serve as an important matter and energy source for bacteria in the lake's pelagic zone and hence have the potential to significantly affect aquatic carbon and nutrient cycling. The proposed model of sinking rates, based on physically sound relationships, can be easily applied to other passively sinking particles, and be integrated into large ecosystem models.

A low‐cost underwater particle tracking velocimetry system for measuring in situ particle flux and sedimentation rate in low‐turbulence environments

“…Indirect estimations from sediment traps provide instead varying results with a speed as low as 1.7 m d −1 for freshwater zooplankton carcasses (Dubovskaya et al ) and up to 500 m d −1 for marine snow (Asper ; Peterson et al ; Trull et al ; Armstrong et al ; Xue and Armstrong ). However, numerical simulations by Kirillin et al () for zooplankton carcasses 1 mm in size revealed a sinking rate of [38–100] m d −1 , which is in the same range as those measured with our 3D‐PTV system.…”

“…c shows that ρ P varied between 999 and 1013 kg m −3 , with an average of 1002 kg m −3 . These values were smaller than in vitro estimations of zooplankton carcasses by Kirillin et al () and Simoncelli et al (), but the excess density ρ P − ρ W was in agreement with in situ measurements of marine snow (Alldredge and Gotschalk ).…”

Habitat structure and ecological drivers of disease

“…The spreading mechanism here is important for the link to habitat: Chaoborus can disperse yeast spores into the epilimnion where both the host (Threlkeld 1979) and Chaoborus (von Ende 1979) migrate at night. These spores can remain suspended and contact new hosts; otherwise, hosts dying from infection likely would sink to the lake bottom before spores escaped (Cá ceres et al 2009;Johnson et al 2009;Kirillin et al 2012). But why did lakes with stronger stratification have greater density of Chaoborus?…”

Paradox reconsidered: Methane oversaturation in well‐oxygenated lake waters

“…6 3 10 23 m 2 s 21 for Lake Stechlin (Kirillin et al 2012). We also estimated the diffusive loss at the water surface using the boundary layer equation:…”