‘I’ve never dealt with a situation like this before,’ fisheries biologist said
State conservation officials found no living fish last week in the East Nishnabotna River south of Red Oak — the result of a massive fertilizer spill at a farmers cooperative.
The only living fish were discovered near Hamburg in far southwest Iowa, downstream of where the river joins with the West Nishnabotna, said John Lorenzen, a fisheries biologist for the Iowa Department of Natural Resources.
However, the handful of surviving carp he saw appeared to be in the process of dying.
“I’ve never dealt with a situation like this before,” Lorenzen said.
He evaluated sections of about 50 river miles over the course of four days to determine the scope of the fish kill. He had not yet fully tallied the estimated number of dead fish on Friday but noted that there were also numerous dead frogs, snakes, mussels and earthworms.
The spill is the result of someone at NEW Cooperative leaving open a hose valve that leaked about 265,000 gallons of liquid nitrogen fertilizer, said Wendy Wittrock, a senior environmental specialist for the DNR.
The leak is believed to have started Saturday and was discovered and stopped by a co-op employee Monday morning, she said.
The company might be subject to large fines and restitution fees for the dead fish.
The effects of the river contamination continued into Missouri, where the Nishnabotna flows about another 10 miles until it reaches the Missouri River. Lorenzen said conservation officials in that state discovered dead fish near the mouth of the river.
In smaller concentrations, the fertilizer contamination can result in a lack of oxygen that kills fish, Lorenzen said.
“However, this was such a large amount of chemical, it more than likely killed the fish from acute toxicity … killing cells at the gills.”
Lab tests to determine the severity of the contamination were still pending on Friday.
The lasting impact on the fish populations is not yet clear. Lorenzen said many of the game fish such as catfish and walleye are likely still in the Missouri River, where they stay during colder months until returning to the Nishnabotna rivers in the spring.
Large numbers of small fish — which the bigger fish feed upon — have died, but those populations can be restored by fish that survived upstream from the spill or in the numerous tributaries that were not affected by it.
It’s possible that the fertilizer killed turtles, too, that buried themselves in sediment of the river bottom for winter. Lorenzen plans to return to the area in late spring to see whether turtle carcasses have floated to the river surface.
The DNR recommends that residents with water wells near the river have their drinking water tested for nitrate, a service that is free through county environmental health departments.
This article first appeared in the Iowa Capital Dispatch.
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