Location #2

Southeast Alaska gets two high tides and two low tides each day. Our tides can range 24 feet from high tide to low at a full or new moon, and all that water needs to flow through this narrow strait over a 6 hour period. Take a look at the flow of the water now – is it flowing toward town? In this case, the tide is rising. If it’s flowing away from town, toward Frederick Sound, the tide is falling. Lots of water flow like this can create back-eddies near shore, so if it’s difficult to determine the direction of flow, look for a bird, stick or bit of seaweed floating farther out towards the middle of the channel. Which way is it moving? If you don’t see much flow in either direction, we are at “slack water,” the short period of calm just when the tide changes directions. As you can imagine, these tide changes and currents impact the lives of all Petersburg residents, from humans to birds, invertebrates to seaweeds. Seaweed and animals living in the intertidal zone have adapted to stay anchored in place, even when the strong flows in the Narrows are trying to pull them free. You may see the long whip-like seaweed known as bull kelp floating or washed up on shore. Bull kelp wraps fleshy fingers called a “holdfast” around rocks or other heavy structures to keep it from washing away. Mussels use thin tendrils called byssal threads to tie themselves down, and barnacles generate their own fast-curing cement to anchor themselves permanently to their rocks. While this might not seem like an easy life, adapting to these conditions pays off: nutrients wash past in the near-constant flow of water, making easy pickings for filter-feeders like these.