ASH LEAF RUST ON CHOPTANK
During the month of June 2017, we received mutiple reports of an orange-colored film over large stretches (2-5 miles) of the Choptank. After some investigations, it was determined to be fungus from ash leaf rust that was concentrating on the water. The shoreline in this area is lined with ash trees, most of which are infected with the fungus, and the marshes are filled with spartina and cord grass, the primary and secondary hosts of the fungus. The cause of the fungus is uncertain. We have been advised that the fungus is nontoxic and not a health concern for humans.
We have received reports of fish kills on Pinks Pond in Cambridge and on the Miles River.
Fish, like all other complex life forms, need oxygen to survive. They get theirs in the form of oxygen gas dissolved in the water. Warm water holds less dissolved oxygen than cold water. Many fish kills in the summer result from low concentrations of dissolved oxygen in the water.
Fish kills are most frequently caused by pollution from agricultural runoff or biotoxins. Ecological hypoxia (oxygen depletion) is one of the most common natural causes of fish kills. The hypoxic event may be brought on by factors such as algae blooms, droughts, high temperatures and thermal pollution.
When the dissolved-oxygen concentration drops too low for fish, a die-off can occur. This can happen as a result of purely natural conditions or because of human activity that adds nutrients, nitrogen and phosphorus, to water systems. Nutrients come from many sources: fertilizers, automobiles, sewage, manure, and others. An excess of nutrients tends to speed up the growth of algae and diminish the availability of dissolved oxygen. Low dissolved oxygen can also result from other factors, such as toxic compounds, poor flushing or circulation, dredging, or a sudden rain after a dry spell.
For more information, contact Matt Pluta at firstname.lastname@example.org or 443.385.0511.