Welcome to the fifth and final episode of "SubSurface: Resisting Montana’s Underwater Invaders." Today we’re putting our producer Nicky Ouellet in the hot seat to answer some listener questions about mussels.

We’ve heard in previous episodes what it’s like to live with invasive zebra and quagga mussels: the costs they can impose, the changes they bring, the clarity they leave in their wake. We learned how they spread, and how managers are working to stay in front of their advances into Big Sky Country. But what if they get here anyway? What are options then? And what does this invasion mean for the landscape? For us? Today in the fourth episode of SubSurface, we’re looking at Plan B, and thinking about what the mussel invasion tells us about ourselves. This is Active Resistance.

Everyone agrees that the goal is to stop invasive zebra and quagga mussels from spreading, but there isn’t consensus on how to do that. This is where Montana is right now. There are a lot of different groups — state, tribal, federal, local and non-government — working to keep the mussels out, but they’re all working under different systems, with different rules to follow and different ideas about how to move forward.

Today, we’re diving into what we know about the mussels - what are they, where did they come from, how did they get here? What can we do to stop them from spreading? We’re trying to understand how those microscopic mussel babies ended up in two Montana reservoirs last summer -- and what our options are if more of them arrive. In this episode we’re tackling the Science of Spread.

This is "SubSurface: Resisting Montana’s Underwater Invaders." I’m Nicky Ouellet, and in our first episode I’m taking us to the Midwest, to lakes where people have been fighting invasive zebra and quagga mussels for decades, to hear, see and smell what could become Montana’s mussel-encrusted future if a full-blown infestation happens here. These stories are reporting from the future.

Montana was invaded last summer. Not by land, not by air, but by water. A microscopic alien showed up in water samples from the Tiber Reservoir, opening the door to a wide range of potentially devastating impacts for Montana's fisheries, outdoor enthusiasts and industries.