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.  

East Pacific Red Octopus on Tomales Bay

All Rights Reserved Tressa Bronner

Recently, we had a chance to get out onto Tomales Bay on a beautiful sunny afternoon. It was a great day for paddling as well as viewing wildlife. We saw all kinds of tide pool creatures, harbor seals and seabirds. Our most exciting find, however, occurred as we were launching our kayaks into the bay. Just as the first couple of boats paddled away from the ramp, we began to see long, shiny red tentacles emerging out of the water. Soon after, the head and body of a rather large East Pacific Red Octopus followed as the handsome critter slowly and carefully made his way onto shore. Undoubtedly, our stomping around in the mud launching our boats disturbed him from his cool, shady hangout; but it gave us a great chance to check out one of the bays most interesting bottom dwellers up close as he shifted from red to purple to brown.



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The East Pacific Red Octopus, once thought just be the young of North Pacific Giant Octopus, is its own species entirely. These much smaller cousins of the Giant Octopus only grow to be about 20 inches from the top of their head to the end of their tentacles. Like all octopi, they are capable of changing their color, generally ranging from red to brown and occasionally white. While the Giant Octopus is found in the depths of the ocean, East Pacific Reds prefer the warm shallow waters of bays and estuaries.

Unlike other invertebrates, when the East Pacific Red catches a meal, it does not eat it right on the spot. Instead, it gathers a collection of crabs, clams and scallops and brings them home to enjoy at its leisure. When the meal is done, the octopus carefully stacks the empty shells outside the entrance to their home, giving the other animals roaming the bay a clear idea of who lives there.

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In general, the Octopus is thought to be one of the most intelligent of all invertebrates. Research has shown that they are capable of problem solving and retaining memories. In fact, the East Pacific Red Octopus was the first invertebrate in captivity to show signs of having individual personalities.

Obviously in our rush to get out onto the water we had disturbed the little guy from his normal routine; so once we were finished taking his picture, we helped him find his way into the shade under the dock and out of sight of the hungry seagulls flying overhead.

Eelgrass in Tomales Bay

Kayaking on Tomales Bay, near shore and in shallow water, we see long green strands that look a lot like seaweed, but actually, it is eelgrass. Eelgrass moved into the marine environment from land around 65 million years ago. It's actually a flowering plant, one of only two in the oceans.

Embarking on an Eelgrass Adventure, Tomales Bay.
Photo by Joseph Kinyon 2009. All rights reserved.

As the days grow longer, and the water warms, millions of pieces of pollen are released and fertilization takes place. In August these plants will then release hundreds of tiny seeds that will sink to the muddy bottom or be carried away by the current. Eelgrass beds have been the subject of interest for awhile, and scientists have some very cool findings. This plant helps to stabilize the coastal zone. Because their leaves are close together and often interwoven by the tides, they actually reduce the motion of the water. As the water slows, suspended material carried around by the tide and current, sinks to the bottom. The important supply of detritus that the eelgrass beds provide for near shore and off shore systems creates areas 10-100 times richer in animal life      compared to adjacent habitats.

In September, the leaves break away from the roots. Some float away, carried by currents; others fall to the bottom where a large percentage of the leaves decompose. Microscopic organisms begin to break down the leaves into smaller particles, and these become surrounded by bacteria and fungi. Bacteria and fungi are consumed by filter feeders such as clams and scallops. Deposit feeders (such as sea urchins) and sediment feeders (worms and snails) also join in to feast. The adult and larval forms of these invertebrates become food for larger life forms such as fish. The closely packed leaves provide a safe haven for young fish to try to avoid predation, the dense jungle of leaves often deters larger fish from going in too far. Thus the continuous cycle that eelgrass plays such a vital role is illuminated.

Eelgrass is difficult to eat for many birds because it is extremely fibrous. However, Brandts Geese rely on eelgrass to survive their 3000 mile migration. They have a specialized crop to ease digestion. Surf Scoters and Scaups swim down and clip off pieces of eelgrass in order to eat the herring eggs that are developing on the blades.

Dendronotus Iris Nudibranch. Photo by Joseph Kinyon 2009.
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Waterfowl are often easy to spot, but what they are looking for in the eelgrass often eludes us, unless we look carefully. Hiding within the jungle of blades one can find: herring eggs, nudibranch (sea slugs) and their eggs, copepods & isopods (small crustaceans), polychates (marine worms), clams, bryozoans, and varying forms of bacteria and fungus. At least 20 species of commercially valuable fish rely on eelgrass for food and habitat at some point in their lives. Searching for food in the rich, muddy areas surrounding the beds we often see leopard shark, bat rays, and other large predatory fish.

As we learn more and more about eelgrass, we also learn that eelgrass is helping to mitigate the impacts of humans on our waterways. Eelgrass is crucial to maintaining water quality. 1 acre of eelgrass absorbs 6.4 pounds of nutrients. This is equal to the effluent from 490 people for 1 year. Eelgrass plays a significant role in moderating the effects of increased carbon dioxide on our planet. 1 acre of eelgrass removes 7400 pounds of carbon. This is equal to the carbon dioxide emitted from a car traveling 3860 miles. Eelgrass beds are very difficult to restore once they have been destroyed (by pollutants, boat propellers and anchors, dredging and development). Less than 10% of restoration attempts are successful after 10 years.

Splendor in the Eelgrass, Taylor's Sea Hare. Photo by Joseph Kinyon 2009.
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Next time you are out on the water, tread lightly in eelgrass zones and be sure to take a closer look at the eelgrass beneath your boat. For a special treat, check out the eelgrass beds after dark. Bring a headlight and be prepared to get wowed by all of the creatures.

Want more: Check out Joseph Kinyon’s article Splendor in the Grass, on Bay pipefish, an eelgrass resident with some extraordinary adaptations for its environment.
Photos provided by Joseph Kinyon. All rights reserved. To contact Joseph or to see more of his photos, Find his "palustrine" Flickr  page.