Ocean Watch
By Susan Scott
Last week, while snorkeling across the mouth of Hanauma Bay, my friend Tim called me over. Glowing mysteries dwell
among oceanic nutrients"There's something in the water that looks like pieces of blue glitter," he said. "Come tell me what it is."
I swam over but saw nothing. A few minutes later, he called me again. "Susan. Come look. What are these things?"
Again I swam over. Again I saw nothing.
"I can't believe it," he said. "They were right here!"
We swam together for a while, and then I drifted off, scanning this wide-open space for big animals, like manta rays or dolphins. A few feet away, I could see Tim diving down, reaching out to touch something I could not see. The man needs to get more sleep, I thought. (Tim works nights.)
And then, there they were right in front of me: a ballet of blue dots, each glowing bright as a neon light. I dove down, reached out -- and the lights disappeared. Tim joined me, and we both tried to catch one. No luck. "They're turning themselves on and off," he said. "What the heck are these things?"
Tim was right. Whenever we reached out to touch a blue sparkle, it disappeared.
It was another magical moment in the weird world of plankton.
Before I got to know plankton, I thought it was boring. Who cared about a bunch of nearly invisible plants and animals drifting aimlessly around the ocean? But I learned to care a lot because these tiny organisms keep us, and everything else on this planet, alive. Besides that, some are out-of-this-world beautiful.
The word plankton refers to tiny organisms swimming, or suspended in the water, near the surface. Most plankton can move up and down in the water but are too small to move against the ocean's currents. Planktonic organisms are true drifters.
Plankton comes in two forms: plants, called phytoplankton, and animals, called zooplankton. Besides phytoplankton forming the base of the marine food chain, its uptake of carbon dioxide and release of oxygen keeps our atmosphere habitable.
Tiny plants called dinoflagellates are a significant part of phytoplankton. Some of these dinoflagellates are known as fire algae because they glow in the dark. When we stamp our feet in wet beach sand at night, the greenish light that sometimes appears is the glow of dinoflagellates.
As for zooplankton, a huge number of fish and invertebrates pass through a planktonic larval stage in their life cycles. Some don't resemble their parents at all during this phase and look more like tiny aliens. These strange little life forms make up much of the ocean's zooplankton, and therefore are at the mercy of the ocean's currents and carnivores.
This may not seem the best way to grow up, but in the ocean it has its advantages. First, tiny larvae can graze on the richest food source in the world, phytoplankton. Second, ocean currents can carry larvae great distances, giving them a chance to settle in new habitats or replenish diminishing ones. We in Hawaii should be grateful for this roaming. It's the reason we have as many marine animals as we do.
A third advantage of young marine animals having their own shapes and drifting away from home is that it eliminates competition between adult and offspring. The young and old occupy different spaces and eat different food.
OK, so what were the blue dots? Plants? Animals? Creatures from outer space?
I have absolutely no idea. If you know what this organism might be, please tell me. Tim is waiting.
Marine science writer Susan Scott's Ocean Watch column
appears weekly in the Star-Bulletin. Contact her at http://www.susanscott.net.
