Tuesday, August 14, 2018

What's in the Water? - Sentinel Floating Islands


     Water composition is pretty important for ensuring a watershed is healthy. That's why Stream Team checks pH levels and turbidity, for example. It's also why Sylvia brought up conductivity, turbidity, and metal content in her wetland health class at Sentinel High School.

     "What is conductivity?" a student asked.
     "Conductivity - how charged the water is, like how many salt ions are in it," Sylvia explained.
     "What does salt do?" came another question.
     "[It] dehydrates animals," like fish, Sylvia said.

     The students thought of ways metal could get into lakes and streams in Montana. Magnesium chloride could come from road salt that washes into drains. But salts aren't the only metal ions that can enter water. Sylvia hinted that many may come as a result of mining exposing materials to surface water. The students thought some more and suggested arsenic, lead, and mercury. All good answers, but most common in Montana, Sylvia said, are zinc and copper. These minerals aren't that bad for humans, but they are unhealthy for plants.

     One way plants are helpful for wetland ecosystems is by holding soil with their roots. If plants start to die from mineral poisoning, their roots no longer protect the dirt from erosion. Water then can pick up bits of that soil, increasing turbidity. Turbidity is the level of suspended particles in the water. If you've ever waded along a beach or shorefront and seen little clouds of dust kick up under your feet, you've seen turbidity in action. That tends to settle back down, though, when the water doesn't move very much, like in a lake. In a river, the current constantly picks up soil particles and carries them downstream, eroding the riverbed and banks. All these dirt particles in the water make it hard for organisms like fish to see and breathe.

     The plants dying has an additional consequence: their decomposition adds to the layer of silt on the bottom, releasing phosphates and nitrates into the water. "Phosphates and nitrates cause algal blooms," Sylvia said, and "silt and the algal blooms cause higher turbidity."

     "Where does phosphorus come from?" Sylvia asked, starting a diagram on the board.
     After a quick look at posters the students had previously made, they said, "decomposing organic matter."
     "Phosphorus is really unique in that it is never ever in the atmosphere," Sylvia said. This means that phosphorus can only enter the water system when it is released by dead organisms and soil. When contaminated plants die off, they release this nutrient, which algae loves. Algae doesn't need to root itself in the soil, but rather "blooms" on the surface where the sun's light reaches. With fewer roots and more algae, the soil can be stirred up even more easily, causing even higher turbidity. Combined with the reduction of oxygen in the water, the increased turbidity makes it harder for any other organisms to continue to survive.

     Adding floating islands to wetland ecosystems allows additional plants to grow on the water's surface to pull phosphates and nitrates out of the water, preventing algal blooms and maintaining or restoring balance.

     Guiding the students through the natural pollutants of wetlands, Sylvia improves their understanding of how natural processes work when in or out of balance. Knowing how these process work provides a foundation for understanding why and how floating islands can restore wetland placed in the Pattee Creek retaining pond down the street. The wetland processes won't be abstract ideas that happen elsewhere, but physical processes that occur in their very own neighborhood. The strategy of using floating islands for restoration also teaches them that taking care of their environment is feasibly in their own hands, and that environmental damage is not a lost cause.

-Cassie Sevigny
AmeriCorps Team Member
Media Coordinator

No comments:

Post a Comment