Nature Watch
By Susan Thurn
Cable Natural History Museum
Chilly fall days give us a warning that winter is coming, and in response plants and animals (including we humans) adjustment accordingly.
The changing of the season also affects the behavior of bodies of water. You may have heard people referring to lakes “turning” this time of year, and wondered what that means.
It’s a twice-yearly phenomenon related to water and air temperature—here’s how it works: In late summer, lake surface waters reach their annual maximum temperatures. Deeper waters are cooler—in many lakes, there is a definite stratification or layering of water temperatures that you would feel if you were swimming on the surface and then dove down deep. The warmest, least dense waters lie on top; water temperature decreases with depth, reaching its minimum temperature at the greatest lake depths.
In the summer, a deep lake will have three layers in the water column: the upper, warmest water (the epilimnion); a thin middle layer, where temperatures rapidly decrease (the thermocline or mesolimnion); and the deepest, coldest water (hypolimnion).
In autumn, cooler air temperatures and diminished hours of sunlight result in a loss of heat from the lake’s upper water layer. As these waters cool, they become more dense and when they reach about 50 degrees F, they sink into the middle layer below, erasing the temperature stratification that had developed during summer.
Eventually, all the lake water reaches a uniform temperature, and surface winds then mix all the water. When the winds are strong and fairly constant in direction for an extended time, they establish a water circulation pattern—as surface waters are blown downwind, waters from below must rise along the upwind shore to replace those waters pushed across the surface. To complete the circuit, the downwind shore surface waters, piled up by the wind, sink to replace the rising bottom waters.
In time, the resulting circulations will completely overturn and mix all the lake’s water—hence “fall turning.” The phenomenon can at times produce a rotten-egg odor, since the deep waters, which are low in oxygen and high in sulphur, rise to the surface and release sulphurous gases into the air. The turnover also mixes atmospheric oxygen into the lake water, replenishing the oxygen in deep waters and allowing fish to return to the depths where many will spend the winter.
Of course, after the fall turning cools the lakewater and as winter approaches, surface waters approach the freezing mark. Unlike most compounds, water reaches its maximum density as a liquid just before becoming a solid. Under normal conditions, freshwater is most dense at 39 degrees F, and ice, being less dense than liquid water, floats. So as lake waters cool, they sink when they reach 39 degrees. Colder water remains above, and is eventually covered with ice.
In the spring, the cycle happens again in reverse. Ice cover melts, and cold surface waters warm until they reach the temperatures of the bottom waters. Winds blowing over the lake again set up a full circulation system; as warming continues, the three water layers again become established, and a full turn of the cycle is complete.
For over 42 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and new exhibit, On Lake Owen: The Art of Walter Bohl, in Cable at 13470 County Highway M. Also find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Post your own stories on the Nature Watch blog at cablemuseumnaturewatch.blogspot.com.
Thursday, October 28, 2010
Wednesday, October 20, 2010
Northern Pike
Nature Watch
By Susan Thurn,
Cable Natural History Museum
They were trolling the waters for a big fish, the musky. “Fish on,” were the words heard from the boat as the sound floated across the water. It was a decent sized fish, but it wasn’t a musky. Instead, it was the struggle of a northern pike that was brought into the boat. This tooth-filled mouth earns its place as the second largest predator fish in northern Wisconsin.
Northern Pike have a duck bill shaped long snout that is lined with sharp canine type teeth. Their olive-green upper sides are marked with longitudinal rows of yellow spots. This “handsome-looking” fish can live for more than 20 years.
The northern pike is a cool-water species whose habitat is usually warm, slow, and shallow, heavily vegetated rivers or the weedy bays of lakes. They also can be found in cold, clear, rocky water bodies. A solitary and territorial fish, northern pike ambush their predators, laying in wait at the edge of weed beds to dart out, attacking with surprising speed. Young northern pike feed on immature aquatic insects and then fish. Adults will eat fish, crayfish, ducklings, muskrats, frogs, leeches or mice. Northern pike are known for being less particular about their food choices. They will even eat younger pike fish, making it critical for the young pike to find safe shelter among vegetation. Northerns typically catch their prey sideways, immobilizing their prey with the backward pointing teeth, and then turning the prey headfirst so they can swallow it. Younger pike have been found dead having choked on a pike of a similar size.
It may be that the catch and release fishing of my family has been the best way to catch glimpses of a northern pike. A swirl or swish at the water’s surface makes me take a second look, hoping for a view of a fish. These fish are just one of the many enjoyable experiences we can look forward to experiencing in our northwoods back yard.
For over 42 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and new exhibit, On Lake Owen: The Art of Walter Bohl, in Cable at 13470 County Highway M. Also find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Post your own stories on the Nature Watch blog at cablemuseumnaturewatch.blogspot.com.
By Susan Thurn,
Cable Natural History Museum
They were trolling the waters for a big fish, the musky. “Fish on,” were the words heard from the boat as the sound floated across the water. It was a decent sized fish, but it wasn’t a musky. Instead, it was the struggle of a northern pike that was brought into the boat. This tooth-filled mouth earns its place as the second largest predator fish in northern Wisconsin.
Northern Pike have a duck bill shaped long snout that is lined with sharp canine type teeth. Their olive-green upper sides are marked with longitudinal rows of yellow spots. This “handsome-looking” fish can live for more than 20 years.
The northern pike is a cool-water species whose habitat is usually warm, slow, and shallow, heavily vegetated rivers or the weedy bays of lakes. They also can be found in cold, clear, rocky water bodies. A solitary and territorial fish, northern pike ambush their predators, laying in wait at the edge of weed beds to dart out, attacking with surprising speed. Young northern pike feed on immature aquatic insects and then fish. Adults will eat fish, crayfish, ducklings, muskrats, frogs, leeches or mice. Northern pike are known for being less particular about their food choices. They will even eat younger pike fish, making it critical for the young pike to find safe shelter among vegetation. Northerns typically catch their prey sideways, immobilizing their prey with the backward pointing teeth, and then turning the prey headfirst so they can swallow it. Younger pike have been found dead having choked on a pike of a similar size.
It may be that the catch and release fishing of my family has been the best way to catch glimpses of a northern pike. A swirl or swish at the water’s surface makes me take a second look, hoping for a view of a fish. These fish are just one of the many enjoyable experiences we can look forward to experiencing in our northwoods back yard.
For over 42 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and new exhibit, On Lake Owen: The Art of Walter Bohl, in Cable at 13470 County Highway M. Also find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Post your own stories on the Nature Watch blog at cablemuseumnaturewatch.blogspot.com.
Wednesday, October 13, 2010
Slugs
Nature Watch
By Susan Thurn,
Cable Natural History Museum
“I’ve been slimed!” That’s the comment that came out of my mouth this week as I discovered a host of slugs underneath the log I had just lifted. With the rain we have had this summer and fall, the slugs seem to be more easily observed. It is not just their slug trails that are fascinating to learn about.
Slugs and snails are related and are called gastropods. Like other land snails, most slugs have two pairs of 'feelers' or tentacles on their head. The upper pair senses light while the lower pair is their sense of smell. When disturbed, they retract either pair, and if damaged, they can re-grow the tentacles. Slugs move through muscular contractions on the underside of their foot. Slugs feed on plant materials with a rasping, specialized mouthpart. Slugs can stretch their bodies to 20 times their normal length, allowing them to squeeze through the tiniest spaces to get to their food. They produce mucus to assist them with movement. The mucus secreted by their foot contains fibers to keep the slug from slipping down steep surfaces. Their bodies are made of mostly water, so their soft tissues need to always stay moist. A thicker mucus coats their entire body for protection from elements and predators. When attacked, slugs can contract their body, making their bodies more compact, which when combined with the slippery mucus, makes it difficult to grab. The mucus also is distasteful as a deterrent. For us, just touching this slime can be a deterrent!
The slime trail slugs leave behind has other effects than just assisting with transportation. A slug can use its own trail again and again to find its way around. Other slugs recognize the trail as their own species, leading to success in finding a mate. The trails can also be used by other slugs to find a good plant food source. Carnivorous slugs will also use the trails to find other slugs as a meal. Finally, many slugs will secrete slime cords to lower themselves to the ground.
Slugs feed mostly at night, seeking shelter during the day in soil or under leafy debris. They become more inactive during dry, hot weather, and more active after rain because of the moisture. In drier conditions, they hide in damp places such as under leaves, tree bark, logs, rocks, and man-made structures to retain their body moisture.
Fall is a great time for slugs. This time of year they lay up to fifty eggs in the soil, where the eggs will wait through winter or sometimes for years until moisture conditions are right. Their egg clusters look like colorless jelly. During the winter, some slug species overwinter in hibernation under ground while with other species, the adults die in the autumn.
To some gardeners slugs are considered to be pests because of the destruction they can create in our gardens. However, many slug species play an important role in our ecosystem by eating decaying plant matter. Some slugs eat other slugs and snails, earthworms, or even carrion. They are also food to snakes, salamanders, turtles, birds, toads and even humans. Explore your own back yard, as you never know what slime trails you might run into!
For over 42 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and new exhibit, On Lake Owen: The Art of Walter Bohl, in Cable at 13470 County Highway M. Also find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Post your own stories on the Nature Watch blog at cablemuseumnaturewatch.blogspot.com.
By Susan Thurn,
Cable Natural History Museum
“I’ve been slimed!” That’s the comment that came out of my mouth this week as I discovered a host of slugs underneath the log I had just lifted. With the rain we have had this summer and fall, the slugs seem to be more easily observed. It is not just their slug trails that are fascinating to learn about.
Slugs and snails are related and are called gastropods. Like other land snails, most slugs have two pairs of 'feelers' or tentacles on their head. The upper pair senses light while the lower pair is their sense of smell. When disturbed, they retract either pair, and if damaged, they can re-grow the tentacles. Slugs move through muscular contractions on the underside of their foot. Slugs feed on plant materials with a rasping, specialized mouthpart. Slugs can stretch their bodies to 20 times their normal length, allowing them to squeeze through the tiniest spaces to get to their food. They produce mucus to assist them with movement. The mucus secreted by their foot contains fibers to keep the slug from slipping down steep surfaces. Their bodies are made of mostly water, so their soft tissues need to always stay moist. A thicker mucus coats their entire body for protection from elements and predators. When attacked, slugs can contract their body, making their bodies more compact, which when combined with the slippery mucus, makes it difficult to grab. The mucus also is distasteful as a deterrent. For us, just touching this slime can be a deterrent!
The slime trail slugs leave behind has other effects than just assisting with transportation. A slug can use its own trail again and again to find its way around. Other slugs recognize the trail as their own species, leading to success in finding a mate. The trails can also be used by other slugs to find a good plant food source. Carnivorous slugs will also use the trails to find other slugs as a meal. Finally, many slugs will secrete slime cords to lower themselves to the ground.
Slugs feed mostly at night, seeking shelter during the day in soil or under leafy debris. They become more inactive during dry, hot weather, and more active after rain because of the moisture. In drier conditions, they hide in damp places such as under leaves, tree bark, logs, rocks, and man-made structures to retain their body moisture.
Fall is a great time for slugs. This time of year they lay up to fifty eggs in the soil, where the eggs will wait through winter or sometimes for years until moisture conditions are right. Their egg clusters look like colorless jelly. During the winter, some slug species overwinter in hibernation under ground while with other species, the adults die in the autumn.
To some gardeners slugs are considered to be pests because of the destruction they can create in our gardens. However, many slug species play an important role in our ecosystem by eating decaying plant matter. Some slugs eat other slugs and snails, earthworms, or even carrion. They are also food to snakes, salamanders, turtles, birds, toads and even humans. Explore your own back yard, as you never know what slime trails you might run into!
For over 42 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and new exhibit, On Lake Owen: The Art of Walter Bohl, in Cable at 13470 County Highway M. Also find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Post your own stories on the Nature Watch blog at cablemuseumnaturewatch.blogspot.com.
Saturday, October 9, 2010
Fall Color Pigmentation
Nature Watch
By Susan Thurn,
Cable Natural History Museum
As we go through another peak season of autumn colors, the mornings begin with a blaze of color as the sun shines on the leaves, and the night’s silence brings comfort and solace. The colors this year were golden! But just what do all those colors do?
First we have the magical chlorophyll, the special ingredient that converts sunlight into sugars. Chlorophyll absorbs red and blue parts of the light spectrum, so it reflects to our eyes as green. Just as sunlight can fade our fabrics colors, or damage our skin, sunlight also causes chlorophyll to break down. Green plants continually create new chlorophyll throughout the warm summer. Fall’s cooler temperatures slow down chlorophyll production, which is when leaves begin showing other colors than green.
The orange color we have seen so much of this fall season is the same color of many fruits and vegetables such as tomatoes, carrots, sweet potatoes, marigolds, pumpkins and even egg yolks and butter. These orange pigments are called carotene. In our bodies, carotene is essential for normal vision, for healthy skin and organs. It is believed to have protective properties against some types of cancer, and against ultraviolet rays of the sun. In plants, carotene absorbs sunlight energy, but instead of photosynthesizing like chlorophyll, it just passes the energy on to the chlorophyll. Carotenes are not damaged as easily by sunlight, so when chlorophyll disappears from the leaves in the fall, the carotene color is left behind for a longer time.
Finally, there are the anthocyanins, which show red and purple colors. These pigments are formed when plant proteins interact with sugars inside the plants cells. The colors formed are based on their acid levels. If the sap in the cells is acidic, the red colors will be brighter, and if less acidic, the color will show more purple. Anthocyanins do not play a part in photosynthesis, so there is some debate over what their purpose is in the leaves. Some believe that they provide a sunscreen for the leaves, allowing the leaves to reabsorb nutrients before they drop to the ground. Anthocyanins are also water-soluble, so can change the freezing point in the leaves, and so may protect a plant’s water supply. Blueberries and so many other fruits and vegetables are filled with anthocyanins, and also have healing powers. Whatever their role, they bring beauty to the colored autumn horizon.
Such a treat another fall has brought us. It brings joy to our eyes, and the rustle of the drying leaves brings a different music to our ears. Additionally, they can bring a variety of colors in our yard, gardens, and kitchens! Enjoy the benefits of these pigments in our foods, and enjoy the wonder of the seasons from our own back yards!
For over 42 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and new exhibit, On Lake Owen: The Art of Walter Bohl, in Cable at 13470 County
By Susan Thurn,
Cable Natural History Museum
As we go through another peak season of autumn colors, the mornings begin with a blaze of color as the sun shines on the leaves, and the night’s silence brings comfort and solace. The colors this year were golden! But just what do all those colors do?
First we have the magical chlorophyll, the special ingredient that converts sunlight into sugars. Chlorophyll absorbs red and blue parts of the light spectrum, so it reflects to our eyes as green. Just as sunlight can fade our fabrics colors, or damage our skin, sunlight also causes chlorophyll to break down. Green plants continually create new chlorophyll throughout the warm summer. Fall’s cooler temperatures slow down chlorophyll production, which is when leaves begin showing other colors than green.
The orange color we have seen so much of this fall season is the same color of many fruits and vegetables such as tomatoes, carrots, sweet potatoes, marigolds, pumpkins and even egg yolks and butter. These orange pigments are called carotene. In our bodies, carotene is essential for normal vision, for healthy skin and organs. It is believed to have protective properties against some types of cancer, and against ultraviolet rays of the sun. In plants, carotene absorbs sunlight energy, but instead of photosynthesizing like chlorophyll, it just passes the energy on to the chlorophyll. Carotenes are not damaged as easily by sunlight, so when chlorophyll disappears from the leaves in the fall, the carotene color is left behind for a longer time.
Finally, there are the anthocyanins, which show red and purple colors. These pigments are formed when plant proteins interact with sugars inside the plants cells. The colors formed are based on their acid levels. If the sap in the cells is acidic, the red colors will be brighter, and if less acidic, the color will show more purple. Anthocyanins do not play a part in photosynthesis, so there is some debate over what their purpose is in the leaves. Some believe that they provide a sunscreen for the leaves, allowing the leaves to reabsorb nutrients before they drop to the ground. Anthocyanins are also water-soluble, so can change the freezing point in the leaves, and so may protect a plant’s water supply. Blueberries and so many other fruits and vegetables are filled with anthocyanins, and also have healing powers. Whatever their role, they bring beauty to the colored autumn horizon.
Such a treat another fall has brought us. It brings joy to our eyes, and the rustle of the drying leaves brings a different music to our ears. Additionally, they can bring a variety of colors in our yard, gardens, and kitchens! Enjoy the benefits of these pigments in our foods, and enjoy the wonder of the seasons from our own back yards!
For over 42 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and new exhibit, On Lake Owen: The Art of Walter Bohl, in Cable at 13470 County
Subscribe to:
Posts (Atom)
