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Archive for the ‘Unit 2-Ecosystems’


Darn nitrogen cycle…

I know this is last chapter (ecosystems/cycles), but I think it illustrates how important knowledge of the nitrogen cycle is for managing an aquarium.

It was a rough weekend for my trout. When I went in to check on them Saturday, I found this…

One of many dead this weekend...

One of many dead this weekend...

…and about 19 more like him! I immediately checked the tank equipment. Seems the artificial filter system had air in the line, and had quit removing wastes and decreased flow in the tank. I quickly primed the pump on the filter, and water started moving again. I sucked the dead trout out of the tank, so their decomposing bodies would not add to the nitrogen spike surely going on in the tank. I immediately changed 5% of the water with fresh water I had on hand. I decided to avoid adding much food for the day also.

When I came in today (Sunday), I found 25 more dead trout! So, if we had an estimated 150 fry at the start of the month then we have lost about 50 total–about 30%! Is that a high mortality rate? I’m not sure since this is my first time managing trout in a 55 gallon aquarium. In the wild, trout (and many fish) have evolved in fast moving streams with little food and numerous predators so they lay hundreds to thousands of eggs–many which do not survive. So, trout experience high mortality rates in the wild.

We’re trying to maintain a simple artificial habitat for these trout, and my students are trying to maintain more complex ones called ecocolumns. These columns have two terrariums and one aquarium built using 2 liter bottles:

Artificial Ecosystems

Artificial Ecosystems

We’ve all experienced a similar phenomenon now–a nitrogen spike. As the living things in the tank feed and produce waste ammonia, the bacteria in the water (and soil in their terrestrial chambers) convert it to nitrites and nitrates. While plants thrive on nitrates, animals find these nitrogen-rich compounds toxic. The range of tolerance for living things is often not very wide, and trout are especially fragile fish. So, I verified the spike was ammonia (instead of nitrates) and quickly did a 15-20% water change to get the stuff out of the water. I also cut back on food again, as decomposing uneaten food can also “feed” the nitrogen cycle.

Perhaps all will be ok. I’m not sure just how many trout we can sustain in a 55 gallon tank long term.

NPP Equation

I just had a question about the NPP=GPP-R equation. The ecosystems with the highest NPP have more producers that are able to convert more solar energy to chemical energy faster. I don’t understand the R values though. Do the higher NPP ecosystems use less energy in respiration? If not, how are their NPP values so high?

Groundwater Gophers

Too funny not to share…Good Luck tomorrow!

Infiltration vs Percolation

Alright, I know that we didn’t go over the hydrologic cycle in class just because it’s been covered so many other times, but looking over question 23 in the study guide and the section in the book explaining the water cycle, I’m still not sure what infiltration and percolation are.  Is it the process of water soaking into the soil then slowly traveling to the aquifers?  If so then what is the difference between the two?

The horizons are not so clear..

Help! Okay so I’m a little confused on question 15 on the study guide when it asks for the 3 soil layers in a soil profile. Is the O Horizon not considered one of the 3 layers? Is it just the A, B, and C horizons that are considered THE 3 layers? What is O if it’s not a layer? Any help with this would be lovely! Thanks

Controlled Experiments Outside the Lab

Hey guys, I was wondering what are the best techniques to use in order to control an experiment in nature rather than the lab. For example, on the practice free response, I talked about isolating trees using netting, but now that I think about it this would probably be relatively ineffective. How else can we ensure that our constants stay constant in nature? (Does this question have anything to do with quadrats, transects, sweep nets etc.?)

Phosphorus Cycle Question

Okay, so Kevin’s post made me look through the diagrams in our book again, and I have a question on the phosphorus cycle. In the diagram, it has phosphates from sewage, mining waste, and fertilizer running off into a lake, but then there are no arrows connecting the lake to the rest of the cycle. Do those phosphates become sediments at the bottom of the lake, or do they join the cycle again through the terrestrial food web (biosphere)? The book’s diagram was just a bit confusing…

Decomposer vs. Detritivore?

While looking over/completing my study guide tonight i was stumped distinguishing between detritivores and decomposers on number 12.  When i looked up the definitions on the back of the book, they seemed almost exactly the same.  Is there an actual difference between the two?  Do they complete two different tasks?  If not, how come they were named two separate things?  I know this is kind of a lot of questions on one, but I’m mainly just concerned in knowing the difference between the two, if there is any, so I can label them on my concept map int he study guide.

Thanks:)

? on the Nitrogen Cycle

So, looking over the cycles in the book, and I realized that the Nitrogen Cycle isn’t complete, at least in the book. On page 57, the cycle shows Nitrogen traveling from soil and runoff of fertilizers into the ocean into “deep ocean sediments”. It does not cycle back, but is depicted as determinately lost, thus shown a hole in the cycle. What happens to the life Nitrogen that gets stuck in the sediments? Is it absorbed by organisms? or slowly weathered?

The Original Nutrient Cycle Story…

Aldo Leopold is a name you may recall from our environmental history readings.  He is often called the “father of wildlife management,” and you’ll encounter his work again later this year.  He wrote a famous book called A Sand County Almanac and in it, this short story called “The Odyssey.”  It is about “atom X” and its travels…wonder what element and biogeochemical cycle it represents?

“X had marked time in the limestone ledge since the Paleozoic seas covered the land.

Time, to an atom locked in a rock, does not pass. The break came when a bur-oak root nosed down a crack and began prying and sucking. In the flash of a century the rock decayed, and X was pulled out and up into the world of living things. He helped build a flower, which became an acorn, which fattened a deer, which fed an Indian, all in a single year. From his berth in the Indian’s bones, X joined again in chase and flight, feast and famine, hope and fear. He felt these things as changes in the little chemical pushes and pulls that tug timelessly at every atom.

When the Indian took his leave of the prairie, X moldered briefly underground, only to embark on a second trip through the bloodstream of the land. This time it was a rootlet of bluestem that sucked him up and lodged him in a leaf that rode the green billows of the prairie June, sharing the common task of hoarding sunlight. To this leaf also fell an uncommon task: flicking shadows across a plover’s eggs. The ecstatic plover, hovering overhead, poured praises on something perfect: perhaps the eggs, perhaps the shadows,or perhaps the haze of pink phlox that lay on the prairie.When the departing plovers set wing for the Argentine, all the bluestems waved farewell with tall new tassels. When the first geese came out of the north and all the bluestems glowed wine-red, a forehanded deer-mouse cut the leaf in which X lay, and buried it in an underground nest,as if to hide a bit of Indian summer from the thieving frosts. But a fox detained the mouse, molds and fungi took the nest apart, and X lay in the soil again, foot-loose and fancy-free. Next he entered a tuft of side-oats grama, a buffalo chip, and again the soil. Next a spiderwort, a rabbit, and an owl. Thence a tuft of sporobolus.  All routines come to an end. This one ended with a prairie fire, which reduced the prairie plants to smoke, gas, and ashes. Phosphorus and potash atoms stayed in the ash, but the nitrogen atoms were gone with the wind. A spectator might at this point, have predicted an early end of the biotic drama, for with fires exhausting the nitrogen, the soil might well have lost its plants and blown away. But the prairie had two string to its bow. Fires thinned its grasses, but they thickened its stand of leguminous herbs: prairie clover, bush clover, wild bean, vetch, lead-plant, trefoil, and “Baptisia,” each carrying its own bacteria housed in nodules on its rootlets. Each nodule pumped nitrogen out of the air into the plant, and then ultimately into the soil. Thus the prairie savings bank took in more nitrogen from its legumes than it paid out to its fires. That the prairie is rich is know to the humblest deer-mouse; why the prairie is rich is a question seldom asked in all the still lapse of ages.

Between each of its excursions through the biota, X lay in the soil and was carried by the rains, inch by inch downhill. Living plants retarded the wash by impounding atoms; dead plants by locking them to their decayed tissues. Animals ate the plants and carried them briefly uphill or downhill, depending on whether they died or defecated higher or lower than they fed. No animal was aware that the altitude of his death was more important than his manner of dying. Thus a fox caught a gopher in a meadow, carrying X uphill to his bed on the brow of a ledge, where an eagle laid him low. The dying fox sensed the end of his chapter in foxdom, but not the new beginning in the odyssey of an atom.

An Indian eventually inherited the eagle’s plumes, and with them propitiated the Fates, whom he assumed had a special interest in Indians. It did not occur to him that they might be busy casting dice against gravity; that mice and men, soils and songs, might be merely ways to retard the march of atoms to the sea.

One year, while X lay in a cottonwood by the river, he was eaten by a beaver, an animal that always feeds higher than he dies. The beaver starved when his pond dried up during a bitter frost. X rode the carcass down the spring freshet, losing more altitude each hour than heretofore in a century. He ended up in the silt of a backwater bayou, where he fed a crayfish, a coon, and then an Indian, who laid him down to his last sleep in a mound on the river bank. One spring an oxbow caved the bank, and after one short week of freshet X lay again in his ancient prison, the sea.

An atom at large in the biota is too free to know freedom; an atom back in the sea has forgotten it. For every atom lost to the sea, the prairie pulls another out of the decaying rocks. The only certain truth is that its creatures must suck hard, live fast, and die often, lest its losses exceed its gains.”