December 2,4,8: Sediment: Bad can lead to worse

One thing can lead to another. In science we call this a cascade. Sometimes cascades are good. When we cut ourselves, a cascade of biochemical reactions leads to clotting and we don’t bleed to death.

One thing can lead to another in a series of bad effects. Sedimentation is one of these unfortunate cascades.

We filled in a 3X3 grid of ways that sediment might lead to fish dying. Some of the squares stand alone– for example, sediment can clog the gills of fish directly, much like a smoke filled room makes it difficult for lungs to work. This square also brought up the important point that aquatic organisms breath oxygen that is dissolved in the water in little bubbles– they do not separate the oxygen from water. The “O” in H2O is not for breathing.

Other squares were connected to each other in some way. The effect of temperature on metabolism is one example. Warm water holds heat and when fish are warm their metabolisms increase because they are poikilotherms (“cold blooded” in elementary school lingo) and their temperatures change with the environment. Higher metabolism increases the need for oxygen– and we now realize there is less DO in sedimentous water.

Getting all the causes down takes some studying. Start now to build fluency since the list is high in concepts.

We have new wiki posts with new opinions about just how much of the fish demise is related to sediment versus acid rain or chlorine.

In other news: Science symposium project ideas were due! Printed!

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