Bioluminescence, Part 1

What’s all the fuss about bioluminescence? What IS bioluminescence? 

Sunset over White Gulch on Tomales Bay.
Photo by Casey Newman, 2011, All Rights Reserved. 

It’s the production of light by living organisms. It can be used to attract prey, to communicate, and to help an organism blend in with its surroundings. Bioluminescence is also responsible for the glow that can sometimes be seen on moonless nights in the waters of the ocean. In several places in the world, including our own Bay Area, conditions are perfect for an annual “bloom” of dinoflagellates, a type of single celled organisms that are bioluminescent.

Dinoflagellates are a type of unicellular planktonic organism (whew, what a mouthful). They drift with the currents of the ocean (planktonic), using two whip-like structures (flagella) to move their single-celled selves around a bit. They can photosynthesize, or get energy from sunlight, but some dinoflagellates also eat other, smaller organisms. Most of them have armored plates made of cellulose for a cell wall, which makes them tough for their size (and also beautiful under a microscope). Some dinoflagellate species cause red tides, and release toxins that are harmful to humans. Other species, like the species that is found in Tomales Bay certain times of year, are bioluminescent.

The species of dinoflagellates that bioluminesce operate on a circadian rhythm- they photosynthesize during the day and they only glow at night. Because they only glow when they are jostled, it is theorized that they glow as a defense mechanism. One of their main predators is a type of shrimp, and if they glow when they are about to be eaten, the light will hopefully attract a fish, which will hopefully eat the shrimp. The flash of light may also act as a distraction, blinding the predator to allow the dinoflagellate time to get away.

During certain times of the year, strong winds push the top layer of coastal water offshore, allowing cold, nutrient-rich water to flow up from the ocean floor. This is known as upwelling, and it is responsible for the surge in nutrients that feed an explosion in the population of single celled algae. One species of those algae are the dinoflagellates that produce the light we see on Tomales Bay. Their bioluminescence can occasionally be seen year round, but tends to be strongest in the summer and early fall. The amount of nutrients in the water affects when we can see the bioluminescence and how long it lasts.

The waters of Tomales Bay are a perfect location for viewing the bioluminescence. Tomales Bay has a narrow opening which limits the amount of water that is exchanged during the tides, concentrating the dinoflagelates in the bay. Beds of eelgrass, a plant with long blades, further trap and concentrate the dinoflagellates in the shallow parts of the bay. The northern end of the bay is relatively undeveloped, which keeps light pollution from washing out the flashes of green light when the organisms are moved. 

A paddle through the bioluminescent waters of Tomales Bay is an amazing experience. As we paddle through the water, our boats, paddles, and even hands can jostle the organisms and make them flash. The bioluminescence does not hurt the dinoflagellates, and they can continue to emit flashes of light for hours. On especially dark nights, fish can be seen setting off the bioluminescence as they swim through the waters underneath our boats. The peaceful waters of Tomales Bay provide a protected location filled with wonderful wildlife to paddle past, and the bioluminescence is truly breathtaking.

Sunset on Tomales Bay.
Photo by Casey Newman, 2011, All Rights Reserved. 

Want to know more about bioluminescence? Check out the Bioluminescence Web Page at http://www.lifesci.ucsb.edu/~biolum/, or tune in next week for more information about bioluminescent critters and about a specific type of bioluminescent fish that returns to Tomales Bay every summer.  

Drakes Estero Trail to Sunset Beach Hike

Details: about 9 miles round trip, approximately 4 hrs with photo stops and a lunch break. This trail is a hiking and biking trail. Note: As of 1/26/11 impassable on a bike after 2 miles, read on for details.

Getting out of the car at the Estero Trail parking lot, was enough movement to necessitate removing a layer. The sun was shining and the bright blue skies were filled with wispy and playful clouds stretching the horizon.

All rights reserved. Photo by Tressa Bronner 2011.

The first mile or so meanders through a thick pine stand. We welcomed the shady start to our hike as we were overdressed for this beautiful day. Amongst the trees we found several groupings of mushrooms poking out from beneath the duff. Once out of the pine stand, we reach the bridge across Home Bay. I have often stood on the bridge and watched countless leopard sharks swim beneath, in and out of the shallow feeding area past the bridge. But not today, the tide was out and only a small channel of water remained in the labyrinth that was the exposed mud of Home Bay. I stood and looked into the water reflecting the clouds and marveled, but not at sharks.

Looking Southwest into Home Bay from Bridge
All rights reserved. Photo By Tressa Bronner 2011

After the bridge, the trail proceeds uphill with views overlooking the estero. Bring your binoculars along as you are often within range to check out shorebirds and rafts of migrating water fowl. After about 3/4 of a mile, the trail got a bit tricky. Cows graze in the area and at some points it seems as if you are just following a cow trail, not an actual park trail. As we descended a shaded hill the wet mud had been trudged by cows and all that remained was a 4 inch wide bridge that was solid enough to support the weight of an adult. This bridge often shifted, as it was the residual non-path of the cows, so hopping back and forth between bridges was necessary to avoid the muddy hoof holes filled with puddles. This left us wondering how one would pass when the bridges were trampled. The trail continued in this way for quite some time: dry sections, muddy sections, followed by muddy almost impassable sections that left me wishing for rain boots but wondering about the bike tire tread tracks I saw, followed by dry sections. I enjoyed the challenge, but this trail is not suitable for all abilities nor bikes at this not-quite-dry time.

Lone Eucalyptus.
All rights reserved. Photo by Tressa Bronner 2011.

We decided on the trail out to Sunset Beach, the shorter of the two options, since we had a time restraint.  If you stay on the main path, you can continue on to Drakes Head and beyond.  The trail out to the beach has lovely views and a couple of fresh water ponds. We stopped at the bench for a picnic in the sunshine. There is also a trail that continues on, but since we weren't there for the sunset, we opted not to get out feet wet. Walking past the large sandbar we stopped to watch the harbor seals catching rays on their temporary beach. About thirty seals were gathered, stretched out, enjoying the balmy weather.

Turning around we received flyovers by two flocks of American White Pelicans that were roaming the estero. At one point they circled around us three times before finally coming in for a landing on a fresh water pond. What a treat to hear their wing flaps and watch their splash landing into the pond.

Estero Trail Overlook
All rights reserved. Photo by Tressa Bronner 2011.

All in all, a lovely day, gorgeous scenery, solitude, just a bit sloshy at points. This bike/hike will be much easier in summer and fall once dried out. I would say kayaking is the best way to explore the estero during these lovely winter days, as long as you check the tide first. Mud in your boots, while not fun, is much easier than a mud flat to cross in your kayak. Get out there soon! The estero closes annually to kayakers for harbor seal protection on March 1st until June 30th.