Moonlit Journey

The word plankton is from the Greek planktos meaning errant wanderer or drifter.

Aquatic ecosystems support plankton in the form of tiny aquatic animals called zooplankton.

Zooplankton are conveyed by currents, but many species have a means of locomotion. Locomotion is often used by zooplankton to forage and to avoid predatory consumption. Zooplankton move by the paddling of cilia, antennae, and jointed appendages, or by muscle contractions creating jet propulsion.

Zooplankton
by Cindy Jo Mendoza

Light-induced migration of zooplankton in arctic marine environments during winter's absence of sunlight was once believed to be non-existent. Recently marine scientists have observed reflected moonlight and lunation causing predictable zooplankton migration cycles.

"During the permanently dark and extremely cold Arctic winter, these tiny marine creatures, like mythical werewolves, respond to moonlight by undergoing mass migrations."
― Kim S. Last, Scottish Association for Marine Science

During sunlight-starved winter months, zooplankton use their means of locomotion to travel downward to greater depths on a daily cycle as the moon rises above the horizon. The zooplankton also sink en masse from the surface to depths of about 50 meters (164 ft) every 29.5 days corresponding to the reflected light of the full moon.

It is believed this downward moonlit journey gives zooplankton the cloak of darkness to avoid predation by carnivorous marine life and birds.

Ctenophores, commonly known as comb jellies
source: University of California Museum of Paleontology

"[...] it is a strange thing that most of the feeling we call religious, most of the mystical outcrying which is one of the most prized and used and desired reactions of our species, is really the understanding and the attempt to say that man is related to the whole thing, related inextricably to all reality, known and unknowable. This is a simple thing to say, but the profound feeling of it made a Jesus, a St. Augustine, a St. Francis, a Roger Bacon, a Charles Darwin, and an Einstein. Each of them in his own tempo and with his own voice discovered and reaffirmed with astonishment the knowledge that all things are one thing and that one thing is all things—plankton, a shimmering phosphorescence on the sea and the spinning planets and an expanding universe, all bound together by the elastic string of time. It is advisable to look from the tide pool to the stars and then back to the tide pool again."
― John Steinbeck

REFERENCES

• In Arctic winter, marine creatures migrate by the light of the moon, ScienceDaily, 7 January 2016.
• Moonlight Drives Ocean-Scale Mass Vertical Migration of Zooplankton during the Arctic Winter, Kim S. Last, Laura Hobbs, Jørgen Berge, Andrew S. Brierley, Finlo Cottier, Cell Press, 7 January 2016.
• The Log from the Sea of Cortez, John Steinbeck, Penguin Books, 18 January 2001.
• Zooplankton, Wikipedia.

Seasonal Change

Early Autumn / Early Spring
Mississippi River, north
of Lock and Dam No. 1

Seasons are distinguished by changes in weather, ecology, and hours of daylight. What accounts for seasonal changes?

“One must maintain a little bit of summer, even in the middle of winter.” ― Henry David Thoreau

A common misconception is that seasons occur because of differences in the distance between the Earth and the Sun throughout the year.

Seasons are not caused by variations in distance between the Earth and the Sun. The variation is distance between the Earth and the Sun is relatively small.

The perihelion, when the Earth is closest to the sun (94,445,000 miles), occurs around January 4th (position 1, left).

The aphelion, when the Earth is furthest from the sun (94,555,000 miles), occurs around July 3rd (position 2, left).

A number of years ago, the documentary “A Private Universe,” about how we misperceive the world around us, was filmed at Harvard’s commencement. Twenty-three faculty members, alumni and graduating seniors were asked, “Why is it warm in the summer and cold in the winter?” All but two answered incorrectly, saying the Earth was closer to the sun in the summer than in the winter (it’s actually closer in January). ― John Edward Huth

Four Seasons

The four seasons of the year are caused by variations is sunlight due to the 23.5° tilt of Earth's axis.

When summer occurs in a hemisphere, it is receiving more direct sunlight than the opposite hemisphere where it is winter.

In winter, sunlight hits the earth at oblique angles so it is less concentrated.

Seasonal changes become more pronounced as our absolute latitude increases (i.e., as we move farther from the equator).

In the northern hemisphere, summer is warmer than winter because sunlight hits the Earth at a more direct angle. Summer days in the northern hemisphere are much longer than the nights.

Much of our literature has been written with a northern hemisphere bias:

“What good is the warmth of summer, without the cold of winter to give it sweetness.”
― John Steinbeck, Travels with Charley: In Search of America

The carousel-like change experienced traveling on what Buckminster Fuller popularized as Spaceship Earth, is captured in Joni Mitchell's song The Circle Game:

And the seasons they go 'round and 'round
And the painted ponies go up and down
We're captive on the carousel of time
We can't return we can only look behind
From where we came
And go round and round and round
In the circle game

REFERENCES

• Earth's Orbit, Wikipedia.
• Losing Our Way in the World, by John Edward Huth, New York Times, July 20, 2013.
• Season, Wikipedia.