The invasion of Dreissena spp. (zebra mussels, ZM; quagga mussels, QM) caused dramatic ecological effects on the Great Lakes ecosystems, which include changes in fish abundance, extirpation of native mussels and profound changes in benthic invertebrates. Until now most dreissenid control measures have focused on reducing mussel settlement in commercially important raw water plumbing; yet, this provides little benefit to ecosystem restoration which is affected by the dreissenid abundance in the natural environment. However, preliminary research in our laboratories has demonstrated that algae produce chemicals that can stimulate or inhibit dreissenid spawning. The stimulatory chemicals may be the normal triggers of spawning that signal when conditions are amenable to larval development; whereas the inhibitory algal chemicals may be protective or toxic signals that prevent predation by dreissenid mussel adults and larvae. Thus, instead of focusing on toxic non-specific chemicals to kill mussels, as are used in water treatment facilities and power stations, we propose to identify and deploy algal chemicals, which are potentially species specific (and therefore more environmentally benign) natural products to regulate dreissenid mussel reproduction to reduce mussel populations at ecosystem scales.