Where freshwater drainages meet the saltwater of the sea, estuaries offer an ecological bridge. Their shallow, less saline waters are sheltered from oceanic extremes, allowing for myriad forms of aquatic life on earth.

In Southeast Alaska, the watery web of islands and estuarine channels lying between the depths of the North Pacific and the rainforest’s tumbling salmon streams are an especially important link. Here, kelp grows like an undersea forest and beds of eelgrass offer a nursery of the sea for the young of species such as salmon and rockfish. The forage fish that feed these great systems – herring and eulachon, capelin and sandlance – depend on beds of eelgrass for safe harbor during young stages in their development.

These estuarine waters harbor eagles, sea otters, bears, whales, sea lions, and thousands of birds—all attractions for the region’s growing tourism economy. The entire estuarine complex of Alaska’s Alexander Archipelago measures about 12,000 square miles of water area and includes 1,000 islands, with 21,000 miles of shoreline. It’s an estuarine complex without comparison. No other estuaries of the United States can compare: Puget Sound, for one, is less than a tenth its size.

Southeast estuaries remain healthy and relatively little development has occurred, yet threats still exist. The risk of oil spills and development along its shorelines – dredge and fill, upland development, and point and nonpoint sources of pollution – are looming pressures for these rich menageries of life.

The scientific community still has a lot to learn about estuaries. Though we’ve completed detailed GIS inventories of rainforests and now know where the most valuable old-growth lies, we don’t understand estuaries in the same way.  

The Conservancy’s estuary program is changing this. In 2004, the Conservancy helped launch the ShoreZone inventory program in Southeast, which employs a suite of high-tech tools to better understand the connection between Southeast uplands and its estuaries. One result is that the Conservancy and its partners are creating maps documenting the biodiversity of estuaries and nearshore habitats in Southeast for the first time.

“There’s never really been a good inventory of what habitats are out there. And to understand important needs of subsistence and commercial fisheries, we need to know where kelp, eelgrass and other species live and grow. And the ShoreZone habitat mapping being done by the Conservancy and partners can tell us this in great detail,” says coastal and marine ecologist Dr. K Koski. “Once we understand where the most ecologically important areas are, we can help ensure they are protected.”

Nature picture credits (top to bottom, left to right): Photo © Bridget Besaw/TNC (Twenty-mile River, Prince of Wales Island); Photo © Kim Heacox/accentalaska.com (Gustavus Forelands).