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.  

Northern Elephant Seals at Chimney Rock

Bulls, cows, and pups at Chimney Rock
Photo by Casey Brechbill, 2011, All Rights Reserved. 

Northern elephant seals are amazing creatures.  They spend 80% of their life in the open ocean and most of that time is spent underwater.  They have the farthest migration of any mammal on land or sea because they migrate twice each year!  Northern elephant seals spend the year travelling from the beaches where they breed and have their pups to their feeding grounds far out in the Pacific Ocean, back to the beaches to molt, and then back to their feeding grounds.

Since 1981, when the first breeding pair returned to the Point Reyes National Seashore, the population of northern elephant seals at Chimney Rock has grown by leaps and bounds.  Though they have been seen at Chimney Rock year-round, the best time of year to see them is between December and March, when the seals return to Point Reyes to breed.

While at sea, elephant seals spend much of their time diving for food.  They can dive as deep as 5000 feet and stay down for 40 minutes!  Their normal dive is between 1,000 and 2,000 feet deep, where there are few other predators competing for the same food.  To dive this deep, elephant seals store extra oxygen in their blood, collapse their lungs, and slow their heart rate down to about 10% of normal.  Elephant seals eat fish, squid, octopus, and small sharks.

Bulls often have wounds around their neck from fights. 
 Photo by Casey Brechbill, 2011, All Rights Reserved.

Because they spend so much time in cold water, northern elephant seal s have a thick layer of blubber, or fat, under their skin.  In the 1800’s, northern elephant seals were hunted almost to extinction for their blubber, which was used for lamp oil.  In the 1920’s, Mexico and the United States banned the hunting of elephant seals.  The species has made an amazing recovery, from less than 100 animals to over 100,000.

There is still plenty to learn about elephant seals.  Until recently, much of what was known about them came from studying animals that were deceased.  With improvements in technology, researchers have been able to learn much more.  Northern elephant seals have been fitted with satellite and radio tags as part of the Tagging of Pacific Predators (TOPP) study.  Attaching a tag to a female elephant seal that weighs between 1,000 and 2,000 pounds is quite a process! Studies like these help researchers learn more about elephant seals and about the ocean environment that they travel through. 

Males have an extra large nose and are much larger than females.  
Photo by Casey Brechbill, 2011, All Rights Reserved.

 There are several places to see elephant seals in Point Reyes.  For some of the best viewing, take a drive out to Chimney Rock and walk on the paved trail to the Elephant Seal Overlook.  On weekends and holidays during peak viewing season, the Park operates a shuttle bus service between the Ken Patrick Visitor’s Center at Drakes Beach and Chimney Rock and the Lighthouse.  More information on the shuttle bus can be found here: http://www.nps.gov/pore/planyourvisit/shuttle.htm

For more information on these fascinating mammals, visit our sources: http://www.nps.gov/pore/naturescience/elephant_seals.htm  or  http://topp.org/species/elephant_seals