Weather Watch

How plankton can put on a bioluminescent light show

My son and I went kayaking in Morro Bay last week, launching from the Baywood Park Pier in Los Osos. As we were coming back that evening, my son noticed ‘blue-green sparks’ flying off his paddle.

He was probably seeing a type of dinoflagellate plankton that emits flashes of blue-green light in response to agitation. This is called bioluminescence.

Acting like light sticks at Halloween, it’s the production of light by living organisms through an internal chemical reaction. This can be seen in fireflies back East or even in glow worms that live in Poly Canyon.

Almost all marine bioluminescence is blue-green in color, probably because blue-green light travels farthest in water. On the other end of the light spectrum, red and yellow hues are quickly absorbed by the water column as you descend.

Bioluminescent plankton inhabit all of the world’s oceans but not its freshwater lakes. Upwelling brings cold and nutrient-rich water to the surface along the immediate shoreline. When the northwesterly winds relax and upwelling diminishes, the bioluminescent plankton can multiply rapidly. Combined with the interactions of the deep scattering layer, they can produce just the right conditions for bioluminescence.

The light of just a single dinoflagellate can be seen at night. When millions upon millions of tiny plankton give off their light at the same moment, the ocean can turn into a nearly indescribable light show.

One night, we were diving off San Clemente Island during a period of high bioluminescence activity, and a pod of Pacific white-sided dolphins came swimming by. The dolphins resembled a gaggle of fast-moving, brilliant blue torpedoes with trails of glowing bubbles corkscrewing toward the surface.

One moonless night, while serving in the U.S. Navy and traveling through the strait of Hormuz (situated between the Persian Gulf and the Gulf of Oman) on the guided-missile frigate USS Estocin back in the early 1980s, the bioluminescence was frightfully strong. The greenish wake of our ship could be seen from miles away as an ever-expanding chevron on the surface of an absolutely flat and calm sea as billions of agitated plankton gave off their light.

A few years later, during a nighttime anti-submarine warfare exercise at a sonar range off the Bahamas, we haphazardly took advantage of bioluminescence. Our aircrew was tasked with tracking a British fast-attack submarine with our trusty but outdated H-2 Seasprite Helicopter.

During our brief, we were told that we would probably be able to keep in contact for only a few minutes before the sub would disappear in the dark void of the ocean. Sure enough, we deployed an active sonobuoy from our helicopter on the sub’s last known position and got a couple of pings or echoes from it before we lost contact.

As we were getting ready to deploy another buoy, one of the pilots saw the distinctive blue-green light coming from one area of the ocean. We immediately flew to where the light was coming from and deployed another buoy. Unbelievably, I got a couple of pings! No doubt, the British sub commander was startled and surprised that we still had contact and started to make very aggressive maneuvers. This only caused his sub to produce more bioluminescence, making it easier to track him. After a few hours of tracking this guy, we ran out of buoys. With our fuel beginning to run low, we decided to return to our ship. From that night on, our helicopter crew was considered the anti-submarine warfare masters of the fleet.

Weather forecast

A strong high-pressure ridge in the upper atmosphere will produce hot inland temperatures, while coastal low clouds and fresh to strong (19 and 31 mph) northwesterly onshore winds will keep the beaches and coastal valleys cool.

The monsoonal flow will produce a few mid- to high-level clouds with a slight chance of a thunderstorm developing over the mountains of eastern San Luis Obispo County this afternoon. This subtropical moisture will also produce higher humidity levels, making it feel even warmer.

Today’s temperatures are expected to range from 101 and 105 degrees in the interior of San Luis Obispo County, with an expected high of 103 degrees in Paso Robles.

Elsewhere, temperatures will climb to the high 70s in the coastal valleys. The southwesterly facing beaches (Avila Beach and Cayucos) will range from the low to mid-70s after the coastal stratus burns off.

The northwesterly facing beaches (Los Osos and Morro Bay) will range from the high 50s to the low 60s under mostly overcast skies today. Interesting to note that today’s highs along northwesterly facing beaches could very well be the coolest highs in the United States.

A cooling trend will begin on Monday, as the strong high-pressure ridge responsible for the interior heat retreats back to the Southwest. At around the same time, an approaching low-pressure trough will create a deep marine layer with areas of drizzle along the coastline and will bring cool marine air far into the interior through at least the first few days of the California Mid-State Fair.

The average maximum temperature in Paso Robles at this time of the year is about 93 degrees. High temperatures at the California Mid-State Fair for Wednesday through Friday will be below normal, mostly in the high 80s. Temperatures will reach normal levels on Saturday through next Monday, then above-normal values the following week.

Surf and sea report

Today’s 3- to 5-foot northwesterly (310-degree deepwater) sea and swell (with a 7- to 10-second period) will remain at this height and period through this morning.

The northwesterly (310-degree deepwater) sea and swell will increase to 4 to 6 feet this afternoon and tonight, further building to 5 to 7 feet (with a 7- to 11-second period) on Monday and will remain at this height and period through Wednesday.

A northwesterly 4- to 6-foot (290-degree deepwater) swell (with an 8- to 11-second period) will develop along our coastline on Thursday, decreasing to 3 to 5- feet Friday through Saturday.

Arriving from the Southern Hemisphere: A significant storm developed about 2,000 miles east of New Zealand on July 12. A long-period Southern Hemisphere (200-degree deepwater) swell from this storm will arrive along our coastline on Monday at 1 to 2 feet (with a 22-second period). This swell is forecast to increase to 3 to 4 feet (with a 17- to 19-second period) on Tuesday and will remain at this height but with a gradually shorter period through Thursday.

Seawater temperatures will be about 53 degrees along the immediate coastline.

Summer safety tips

Summer is here, which means lots of fun in the sun! Nevertheless, the weather can get extremely hot and quickly go from fun to dangerous. Extreme heat can be life-threatening. So learn what extreme heat is and how you can protect yourself. To learn more, please go to

John Lindsey is a media relations representative for PG&E. He is also a local weather expert and has lived along the Central Coast for more than 23 years. Send him an e-mail at