Zebra Mussel (Dreissena polymorpha)

The zebra mussel costs North America over $1 billion annually, a financial impact that dwarfs Burmese Python (Python bivittatus)'s ecological damage. These fingernail-sized molluscs from the Caspian Sea clog water intake pipes with colonies of up to 700,000 per square meter, choking infrastructure. They smother native mussels, reducing their populations by 95% in invaded lakes, and filter plankton so efficiently that they rob fish of food. This outcompetes Burmese Python (Python bivittatus)'s python, which focuses on mammals, as zebra mussels reshape entire aquatic food webs.