SURF SCIENCE: FORECASTER CHRIS BORG ON RED TIDE

John D. of Landlocked, KS writes: Why do I keep hearing about the red tide invading our shores? Should I be concerned?

JD, the phenomena you’re referring to does not involve politics or people. It doesn’t really have anything to do with the tide either and it actually appears in a range of colors. That’s why the more appropriate term for this natural occurrence is algae bloom.

The algal events come in two types, with the most common kind simply called algae blooms, and the less frequent but far more noticeable variety named harmful algae blooms. Those latter ones do tend to have a reddish hue. Harmful or not, each type of bloom is created by alga, infinitesimally little life forms collectively known as phytoplankton. At home in both fresh and salty water, phytoplankton are microscopic organisms usually consisting of a single cell. In comparison, you consist of around 100 trillion cells. But even with our 100,000,000,000,000 to 1 cell superiority, every phytoplankton can do something we can’t do: photosynthesize. Traces of chlorophyll inside the tiny plants enable them to convert light into chemical energy; to transform solar rays into the sugars they need to survive. Phytoplankton photosynthesis is what we need to survive too, since a byproduct of that process provides us with over half the oxygen we breathe and much of the protein we consume.

Phytoplankton: most are good, but there are some bad apples in the bunch. Credit: www.earthobservatory.nasa.gov

In the ocean, phytoplankton form the very bottom link of the food chain. From the smallest to the largest, and either directly or indirectly, all aquatic animals feed on phytoplankton. On the small/direct feeding end of the spectrum are zooplankton. That group includes minute creatures such as copepods and krill, as well as the larval stage of things like crustaceans, mollusks and fish. The ocean’s biggest fish, the whale shark, and its most massive marine mammals, whales, also directly feed on phytoplankton while they gobble up zooplankton too. Other sea creatures and marine animals are indirect consumers of phytoplankton. They follow the food chain chain of command by first eating the smaller/direct feeders and then getting eaten by larger/indirect feeders. This finely tuned system of consumption runs smoothly as long as all of its components are in balance. When that balance is lost the intricate system can collapse.

Like all plants, algae require sunlight, water and certain nutrients such as nitrates and phosphates to live. Floating around in the ocean, phytoplankton always have plenty of water, but water temperatures may or may not be conducive to supporting the algae. The availability of light varies depending on the weather and turbidity/salinity of the sea. The amount of nutrients can be even more sporadic. Since one or more of those essentials is generally in short supply the algae population is kept in check. However, when nutrients are abundant, the sun is shining bright and water conditions are just right, algae numbers can grow exponentially. Usually such a phytoplankton population explosion creates an algae bloom that fattens up the entire food chain. But when the phytoplankton involved are the toxic kind, the resultant harmful algae bloom can shatter that chain and threaten the health of all other life in the water. That includes you!