Decomposing seaweed, algal bloom, sea foam, and tuna crab near the lagoon’s inlet

If you have spent time at Cardiff Reef or at the beach near the inlet, you might at times wonder, What is that smell?  Seaweed in the lagoon’s inlet is doing its thing — decomposing — and creating a sulfur-like scent.

Click on the video below to learn more about this naturally occurring event with
Doug Gibson, Conservancy Executive Director and Principal Scientist:

Doug GIbson Youtube.PNG

We’re at the end of our winter storms, and kelp and red corraline algae often get pushed into the inlet. Once it gets in here, it settles out and starts to decay. When that happens, it creates hydrogen sulfide, or an egg smell. As we get into summer, this will soon dissipate. The water is healthy. If you want to take a look at the natural process, come down to the inlet and see the algae.

Decomposing_Red Coralline copy

Decomposing kelp, and red coralline algae (Calliarthron sp.), in the lagoon inlet channel

Heron_Red Coralline copy

Graceful wetland birds, like the Great Blue Heron, wade through the algae at the inlet in search of a next meal.

At other times while at Cardiff Reef or at the beach near the inlet, you may have noticed sea foam and/or an algal bloom, other natural occurrences.

Seafoam2

This photo, taken after the recent inlet dredging, shows sea foam at the base of the sand piles placed on Cardiff State Beach.

Sea foam occurs when kelp and algae buried in the inlet channel create a hypoxic condition that contributes to the lowering of oxygen levels. When decomposing, this material is agitated, and a foam will develop that usually lasts a few tidal cycles.

AlgaBloom3

Within days of an inlet closure algal blooms can occur. These algal blooms quickly use dissolved oxygen in an already stressed system. By day three of the recent inlet closure, the fish in the lagoon were not receiving enough oxygen.

Recently you may also have noticed Pelagic red crabs, or tuna crabs, on the beach.

Crab1

Tuna crabs are usually more associated with warm water events, like El Nino. They get washed in with the winds, such as our recent upwelling, and offshore red tide event.

Every visit to the lagoon and to the beach is unique and holds many discoveries. 

Thank you for following Lagoon Connections.

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