Water hyacinth has practical uses
By PAUL G. JANTZEN
Contributing writer
Having breakfast on the shore of Clear Lake near Houston, we noticed a large collection of floating plants crowded against the bulkhead (retaining wall). Our daughter sees them only after topical storms. On closer inspection, I noticed swellings in the stems and leaf stalks which I assume to be floating devices. Some of the plants appear to have been uprooted. They must have been brought in by the outgoing tide. The next day, they had floated on the incoming tide in the opposite direction toward Clear Creek, probably their place of origin.
The main factor producing tides of Earth's seas is the moon which exerts gravitational attraction on the water closest to the moon. On the opposite side of Earth, the moon's attraction is weaker, and inertia tends to throw the seas out from Earth. Thus, the seas bulge outward on the sides closest and farthest from the moon. Between bulges, the sea is depressed.
While Earth's oceanic bulges and depressions depend on the moon's position, Earth is spinning around its own axis (within the sea's bulges and depressions), so any one location on Earth's seas experiences two high tides and two low tides with each rotation.
Since the moon revolves around Earth while Earth rotates about its own axis, the moon requires 24 hours and 50 minutes to return to the same position in the sky. So there are roughly two high tides and two low tides each day.
On the second day, two older men were walking along the lake shore, stopping periodically to perform some procedure, then moving on to repeat the procedure. I knew that there must be something I could learn from them. One was Roy Rash, an electronic technician; the other was Bob Bell, a metallurgist. They explained that leaks were developing in the bulkhead designed to keep the shore from eroding into the lake. The aluminum piling was corroding, the dissolving metal allowing the soil to wash out to the lake. With their voltmeter, they were measuring the electric potential between the aluminum, the lake water, and the soil. They will probably recommend burying rods of a more active metal that would be a substitute target of corrosion and save the aluminum.
And what is the plant the tide had brought into the lake shore, I asked. That, they informed me, is the water hyacinth. I had read of this invasive aquatic plant but had never seen it. The recent heavy rains apparently uprooted the plants and washed them down Clear Creek on into Clear Lake. Then the rising tide reversed their direction back toward Clear Creek.
The water hyacinth, native to Central and South America, was brought to the United States in the 1880s for an exhibition in New Orleans. A woman took one of the handsome blue-flowered plants to her backyard in Florida, and within 10 years, the species had become a public nuisance. It not only crowded out native aquatic plants; it also blocked boating traffic in ponds, canals, and rivers. Without its natural enemies, it thrived in Florida's nutrient-rich waters, doubling its population every two weeks, and spreading quickly to other southeastern states.
A variety of control methods were tried: mechanical choppers, deadly sodium arsenate, the herbicide 2, 4-D, the endangered herbivorous Florida manatee (sea cow), a large herbivorous fish imported from the Soviet Union, and an herbivorous water snail imported from Puerto Rico. A more promising natural predator of the hyacinth is a species of weevil imported from Argentina which feeds only on hyacinth.
Research by the National Aeronautic and Space Administration suggests several practical uses of the water hyacinth: absorbing toxic substances from sewage treatment lagoons, conversion to a fuel similar to natural gas through fermentation, providing a protein and mineral supplement for cattle, and fertilizing and conditioning the soil.
Just think, without tides, I may never have seen a water hyacinth.
