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Rhythm of river life

River Life: Natural rhythms control the cadence of existence

We live in a rhythmic world and hardly realize it. Usually when we think of rhythm, we think of music and the beat of the drums and bass as they set the tempo for the melody. But nature has its own set of cycles that establishes the cadence of the St. Johns River, for instance, and even the pace of our lives.

This struck me recently as I sat on a bench watching the waves roll by and listening to the slap, slap, splash, as the water hit the dock. There is a certain calming effect to that sound. I think we are drawn to water because of it.

That got me thinking about all the other cycles that influence our very existence, but we seldom think about. And they come in a wide variety of time intervals, which may partially explain why we are so unaware. Seasons are a year-long cycle that, while obvious, we don’t think about how much they control our lives. Depending on where you live, snow in the winter and heat in the summer have a dramatic impact on our activities, mood and attitude.

Then there is the very apparent effect of the day/night cycle, which governs life in so many ways. Some impacts are more evident, as in our sleep patterns. Think about how much changing from standard time to daylight saving time influences our daily behavior, at least for a few days.

Our very existence, and that of many animals, is tightly tied to the daily orbit of earth in relation to the sun. Many animals, humans included, have an internal clock by which we live. If they (and we) are put in a situation of constant daylight or darkness, we revert to that biological clock to regulate daily activity levels. We call it circadian rhythm, because it is almost (circa-) a day (-dian).

That same kind of internal timing exists in some marine animals, too, where it is often linked to the tidal cycle. My doctoral dissertation research was on the intertidal beach animal, Emerita talpoida, commonly called a mole crab or sand flea. They make great pompano bait, but I was interested in learning if they had an internal tidal clock. It turns out they do.

Mole crabs move up and down the beach face in synchrony with the tide. As the tide rises, they migrate up the beach, and as the tide retreats, they move down. Then if you then put them in an aquarium with no tide and monitor their activity, they mimic the tidal cycle with their activity pattern.

River life is full of patterns and rhythms, some more apparent than others, but they control our very existence.

Glad you asked River Life.

What do you consider to be the most challenging river-related issue we are facing today? Are you optimistic that we can solve the problem?

That is a very difficult question because, 1) there are so many issues, and, 2) they are occurring very slowly. We hardly notice until it is almost too late.

For instance, the amount of plastic trash is gradually overwhelming our entire planet. Climate change due to human activity is occurring and causing environmental shifts that we have not experienced before, such as sea level rise.

But our biggest challenge may be to convince people that what they do as an individual can make a difference. We get so awed by the magnitude, we forget the collective positive impact that millions of us working together can have.

Dr. Quinton White

River Life runs the first Tuesday of each month in The Florida Times-Union. Email Quinton White, executive director of Jacksonville University’s Marine Science Research Institute, with questions about our waterways at qwhite@ju.edu. For more on the MSRI, visit ju.edu/msri.