Did you know that Kachemak Bay and Cook Inlet are also both “estuaries”? And that Kachemak Bay has been designated as a NOAA National Estuarine Research Reserve since 1999 and Cook Inlet is one of the largest estuaries in the United States?

So, let’s see what makes up an estuary, and why we are celebrating them with #IHeartEstuaries events during the week of Feb. 10-17.

Estuaries are bodies of water where rivers meet the sea — where salty seawater mixes with fresh water draining from the land — and provide homes for fish and wildlife, support economies like our Kachemak Bay communities, fight climate change, and more.

Estuaries are often called the “nurseries of the sea,” because so many animals love to reproduce and spend the early part of their lives there. Most of the fish and shellfish we eat — including salmon, herring, crabs, clams and oysters — spend some or all of their life in estuaries.

Estuaries are also a major stopover point for migratory animals such as waterfowl and provide marine mammals, like sea otters, seals and whales, with places to feed, rest and raise their young.

Coastal communities, in the Cook Inlet region and nationally, rely on estuaries for jobs, shipping, fishing and tourism. Estuaries are great places to fish, hunt, watch birds, take photographs, hike, canoe and kayak, and observe wildlife. They also play important roles in protecting communities from the impacts of climate change, with salt marshes and seagrass beds helping to reduce erosion from storms and coastal flooding.

With all these benefits, estuary regions are popular places for people to live, which can bring challenges from human activities on land and water that can harm estuary health, and degrade living conditions for species that live in or visit estuaries.

NOAA works nationally to protect and restore estuaries — locally, the Kachemak Bay NERR and NOAA Kasitsna Bay Laboratory work with many partners to provide our communities with sound science information, technical expertise and education about this rich estuary ecosystem, as well as the challenges it faces from climate change, development, invasive species, harmful algal blooms and more.

Check out https://accs.uaa.alaska.edu/kbnerr/ and https://coastalscience.noaa.gov/project/ecological-assessment-for-kachemak-bay-alaska-science-tools-to-inform-management/ if you are interested in finding out more about what we are learning.

As one example (especially for ocean trivia fans), here are some fun facts from our monthly oceanography surveys.

While most people keep an eye on big tides, which are some of the largest in the world with up to a 28-foot vertical range, you may not know that the tidal currents aren’t strong enough to mix in the large amount of fresh water that comes from rain, snowpack and melting glaciers.

For much of the year Kachemak Bay has a fresher surface layer that’s just 30-50 feet deep, with saltier water underneath it all the way up to Bear Cove at the head of the bay.

Plankton, fish, birds and marine mammals all use these estuary water layers, so we keep track of how they change during the year and between different years.

Strangely enough, fresh water flowing out at the bay surface also causes saltier ocean water to flow into the bay at deeper depths (estuary physics!).

To measure this flow, we put out satellite-tracked drifting buoys off Nanwalek last August that are designed to float below the surface layer, and then watched as one buoy moved into Kachemak Bay and a second buoy moved up the east side of Cook Inlet to Nikiski, before scooting over to the west side of the Inlet and out to the ocean.

We were surprised the deep estuary inflow into the bay was even strong enough to beat the tidal current, as the buoy slowed down, but did not get turned around by the outgoing tide.

Always something new to learn about our estuary!

We invite everyone to help us celebrate estuaries and learn more about Kachemak Bay with #IHeartEstuaries events in February— hope to see you there!