How does seasonal calcium hypochlorite use in West Lake affect aquatic ecosystems and regional demand?

How does seasonal calcium hypochlorite use in West Lake affect aquatic ecosystems and regional demand?
Hangzhou's West Lake management applies roughly 7 tonnes of calcium hypochlorite annually across 24 lotus zones covering about 150 mu, just 1% of the lake's total area. The operation, called 'pond clearing,' runs at night over about a week each April. Food-grade calcium hypochlorite is diluted before application, targeting herbivorous fish and algae while sparing native species and birds. The mechanism is irritation of fish gill epithelium, prompting mucus secretion and an avoidance response rather than toxicity. This niche but recurring municipal application highlights a stable, low-volume demand segment for high-purity calcium hypochlorite, distinct from industrial water treatment or aquaculture uses, and underscores quality specifications over sheer volume.