Water Ways: Got oxygen? More of the story ...

Last month I introduced a very important water-quality measurement that monitors at Stillwaters Environmental Center test for every month in the Carpenter Creek watershed – dissolved oxygen. Since oxygen is so critical to all aquatic life, here are a few more oxygen facts. The map below was created by Kingston’s own Walt Elliott to give you a better sense of the location of our monitoring sites. The letters and numbers correspond with those referenced here.

As described last month, all of our freshwater sampling sites meet the water-quality standards set to protect adult fish and benthic (bottom dwelling) insects. However, at Site #2 we have measured some dips in oxygen levels during the time salmon eggs are incubating in reds (gravel nests) that go below the level studies say is optimum for eggs (8 mg/l).

In our estuarine stations (where salt and freshwater meet), we have additional forces affecting the water’s ability to retain dissolved oxygen. Again, temperature plays a big role – cooler water holds more oxygen. In saltwater though, dissolved salt forces dissolved gas out of water, lowing oxygen’s solubility. However, as water moves over rocks and woody debris, or is blown by wind, air is mixed into the water. As marine water is moved by the tides, oxygen is introduced.

At Site A, the brackish marsh, oxygen levels have been measured as low as 5.53 in late summer and early fall. Site B, which is more influenced by salt water, has exhibited its lowest oxygen levels in fall and in February each year, around 7 mg/l. Both Arness Park (Site C) and the end of the Kingston marina dock (Site D) have measured lows around 6.9 in September and also sometimes in February.

What does this tell us about our freshwater and marine systems? As we can see from the data, and the observations the monitors make every month, each site is different! Even sites that are just several hundred feet apart (Site 1 and Site A) have very different morphology (shapes of the stream channels) and very different water chemistry (fresh and brackish) that influence the magical oxygen dissolved in the water. We also see that those channel shapes can change rapidly with big storms.

At Site 2, the water, wood and other debris have been carving out a pool where only shallow water use to be. At Site 3 the significant rain events of last November and December moved cobble-sized stones so dramatically they laid a new rock and gravel bar that has moved the stream out of its original channel path.

All this tells us the Carpenter Creek system is a changing place. Those changes can be caused by natural rain events or by other alterations that tip the delicate physical and chemical balance. What we humans do can tip towards more or less oxygen in many ways.

Betsy Cooper is a board member and stream monitor at Stillwaters Environmental Education Center. She also serves on the Kingston Citizens’ Advisory Council.

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