Pressure Changes

Meg Freer

She hovers in a sunny spot by the stream
until something interesting happens.

A forging hammer in the factory
a mile away falls six feet with the force
of 35,000 pounds. The ground trembles.

Salmon leave the sea and remain
a few days in the brackish estuary
then enter the stream’s freshwater.

At day’s end the streamside
sinks into fox-shade.

The Science

This poem explores various meanings for the phrase ‘pressure changes’ and was prompted by the fact that salmon are anadromous fish, able to live in both saltwater and freshwater. When most saltwater fish are put into freshwater, their cells will burst. But salmon have adapted – their water-drinking habits change and their kidneys function differently in the two environments, and their gills have a special enzyme that facilitates the transportation of the electrolytes Na+ (Sodium) and Cl- (Chloride) into or out of the salmon’s blood. There is an acclimatization period going both directions, necessitating time spent in the mouth of the stream where there is a mix of freshwater and saltwater.

The Poet

Meg Freer grew up in Montana and lives in Ontario, where she writes and teaches piano. Her award-winning prose, photography, and poems have appeared in many journals, and she has published three poetry chapbooks. She is a member of the Ontario Poetry Society and the League of Canadian Poets and holds a Graduate Certificate in Creative Writing from Toronto’s Humber School of Writers. She is currently Poet-in-Residence for the Arthur B. McDonald Canadian Astroparticle Physics Research Institute.