Filter feeders are key to small microplastic residence times in stratified lakes: A virtual experiment.

Microplastic (MP) is potentially harmful to lake ecosystems, with its uptake into the food web largely controlled by its residence time in the lake water column. Here we combine laboratory and virtual experiments to quantify residence times of small MP (<15 µm) in two contrasting model lakes; Lake Constance (large lake) and Esthwaite Water (a small lake). We compare MP residence times in a purely physical system with MP transport controlled by sinking and mixing to a model where, in addition to physical processes, zooplankton package MP into faecal pellets that are then egested into the water column. The laboratory experiments showed that MP settling velocities increased from ~5 × 10-6-10-3 mm s-1 for pristine MP to ~1 mm s-1 for MP embedded faeces. Modeled lake residence times for the 0.5 and 5 µm particles were >15 years in the abiotic models, while in the biotic simulations they were reduced to ~1 year. There was little difference between abiotic and biotic simulations for the 15 µm particles. The ratio of the MP zooplankton uptake velocity to the sinking velocity (v_up/vs_epi) was used to classify biological vs. physical transport pathways. For the 0.5 and 5 µm particles v_up/vs_epi was ≫1 in all cases for both lakes, while for the 15 µm MP there was a transition between biological and physical processes dominating residence times depending on zooplankton numbers. Our results suggest that packaging of small MP in faecal pellets by zooplankton will control its residence time in lakes. Moreover, the majority of small MP will cycle through organisms before reaching the sediment, increasing the likelihood of negative ecological effects and transfer in the food web.

Age-dependent early complications of hypospadias repair: a single institutional experience.

PURPOSE: To correlate age at hypospadias repair with early post-operative complications and highlight need for adaptation to post-operative care in older children. METHODS: Anecdotal evidence suggests boys with delayed surgery for hypospadias suffer increased rates of early post-operative complication. Hence, a retrospective analysis was conducted of all patients undergoing hypospadias repair between March 2019 and 2022. RESULTS: Ninety eight patients were divided into Group A (< 2years of age at first surgery) or Group B (> 2years). While patients in Group A encountered no early post-operative complications, seven in Group B (11%) suffered a range of complications including dislodged stents (3/7), significant spasmodic pain requiring prolonged hospital stay (2/7) and urinary retention (2/7). More than half of these children required emergency supra-pubic catheter insertion. CONCLUSION: Significantly more children undergoing hypospadias surgery after the age of 2 years suffered complications within the early post-operative period. This resulted in prolonged hospital stays and a number returning to theatre for insertion of a supra-pubic catheter. We recommend a tailored approach to the post-operative care of older children undergoing hypospadias repair, including strict parental education regarding dressing/stent care and medication compliance, as well as efforts to enhance robustness of dressings and stent anchorage in children likely to pull at stents.