Mus­sel Up

With the Ottawa River clear of ice, prom­ises to clean up the wa­ter­way will be mak­ing head­lines. Matt Har­ri­son talks to a zo­ol­o­gist about a decades-old prob­lem that is still wreak­ing havoc with the river’s ecosys­tem

Ottawa Magazine - - Contents -

Stem­ming the flow of raw sewage flood­ing into the river af­ter heavy rain­falls is one of the ma­jor prob­lems be­ing ad­dressed by the Ottawa River Ac­tion Plan (ORAP). In­deed, ear­lier phases of the plan have al­ready sig­nif­i­cantly re­duced pol­lu­tion en­ter­ing the river. The fi­nal phase of the ORAP — build­ing large stor­age tanks to con­tain over­flow — is sup­posed to kick into gear this sum­mer, but it re­quires pro­vin­cial and fed­eral fund­ing, and so far, none has been promised. De­spite op­ti­mism from Jim Wat­son’s of­fice, there is al­ways a chance the money won’t be there. Mak­ing bets in a fed­eral elec­tion year is a risky busi­ness. And if the ORAP is put on the back­burner, new think­ing will be re­quired for the cleanup of the beloved his­tor­i­cal river.

But re­think­ing the Ottawa River isn’t such a bad idea. In fact, it may lead to a more holis­tic ap­proach — one that ad­dresses not only over­flow but other fac­tors af­fect­ing the health of the river.

The ze­bra mus­sel — and the her­culean task of res­cu­ing na­tive mus­sel pop­u­la­tions from its death grip — pro­vides a per­fect ex­am­ple.

“When the ze­bra mus­sel was first in­tro­duced into the Great Lakes ecosys­tem, it spread through­out like wild­fire,” says An­dré Mar­tel, a zo­ol­o­gist with the Canadian Mu­seum of Na­ture. Mar­tel ex­plains that since the ar­rival of the ze­bra mus­sel in the Great Lakes in the mid-to-late 1980s, na­tive mussels such as the hick­o­rynut mus­sel have been placed on the en­dan­gered list. So named be­cause of the black-and-white zigzag pat­tern on its shell, the ze­bra mus­sel hitched a ride in the bal­last wa­ter of ships leav­ing their ports in Rus­sia, boats that made their way to the St. Lawrence River and dis­charged that wa­ter — along with the ze­bra mus­sel stow­aways — into the Great Lakes ecosys­tem. Mar­tel sus­pects that ze­bra mussels found their way to Ottawa by cling­ing to the un­der­sides of boats trav­el­ling from Lake Erie, up the Rideau Canal, and into the Rideau River.

Per­haps no one un­der­stands just how dire the sit­u­a­tion is bet­ter than Mar­tel, a 55-year-old marine zo­ol­o­gist and diver who reg­u­larly checks in on the mus­sel pop­u­la­tion in the Ottawa River.

Mar­tel dives in Au­gust, Septem­ber, and Oc­to­ber, when the Ottawa River is fairly clear and the cur­rent is low. Among the sunken trees and other ob­jects, nat­u­ral and man-made, Mar­tel scratches around at the bot­tom of the river, search­ing for signs of na­tive mus­sel life. It is a frus­trat­ing search, be­cause the vast ma­jor­ity of the hick­o­rynut pop­u­la­tion has been wiped out. It can take up to 20 min­utes of un­der­wa­ter div­ing to find a sin­gle living na­tive mus­sel.

For most of us, mussels are some­thing that comes to mind only when we’re order­ing in a seafood restau­rant. Bi­valve crav­ings aside, the hick­o­rynut serves a far more vi­tal func­tion. Like a ca­nary in a coalmine, the hick­o­rynut (and 15 other species of fresh­wa­ter mussels in the Ottawa River basin) re­veals vi­tal clues about the health of a river.

“On the Rideau River, we’ve gone from one of the rich­est rivers — in terms of its na­tive mus­sel species in eastern Canada — to hardly any­thing left. The main rea­son has been due to the ze­bra mus­sel’s in­va­sion,” says Mar­tel.

Like many in­va­sive species, the ze­bra mus­sel has no nat­u­ral enemies in Canada, which means there is lit­tle to slow its spread. Nor has it evolved along with the na­tive species. Ze­bra mussels are picky eaters — they con­sume only the good al­gae while leav­ing the bad. This can am­plify a pre-ex­ist­ing prob­lem of toxic al­gae that might ex­ist in an area as a re­sult of hu­man ac­tiv­ity, thereby re­duc­ing the oxy­gen in the river and suf­fo­cat­ing fish. And the hunger ze­bra mussels have for the good plank­ton can de­prive small fish of an im­por­tant food source.

Mean­while, the na­tive mussels can’t do much in re­sponse, be­cause ze­bra mussels are re­ally good at at­tach­ing them­selves to ev­ery­thing — in­clud­ing the shells of na­tive mussels. All that ex­tra weight im­pedes the na­tive mussels’ abil­ity to open and close their shell. It also pre­vents them from us­ing their “feet” — mus­cu­lar ap­pendages that they con­tract to bur­row in the sand. In what Mar­tel calls the “earth­worm ef­fect”, na­tive mussels use their foot to dig into the river bot­tom, carv­ing oxy­genat­ing canals. But with a ze­bra mus­sel — or two or three — on their back, they can’t move so well, which means the na­tive mussels can’t do their job of oxy­genat­ing the soil.

The bur­row­ing also al­lows mussels to at­tract fish with their “eye.” Yes, in ad­di­tion to feet, some fe­male na­tive mussels have an eye — it acts like a an­gler’s lure — that at­tracts large fish. Stur­geon, in par­tic­u­lar, get tricked into think­ing the eye be­longs to a small fish and ap­proach the mus­sel. When the big fish swims by,

the mus­sel re­leases its em­bryos onto the gills and fins of the fish; those em­bryos hang on un­til they’re ready to “hatch” — thus spread­ing through­out the river.

But with ze­bra mussels pre­vent­ing bur­row­ing, those crit­i­cal feet and eyes aren’t given the chance to do their re­spec­tive jobs and re­pro­duc­tion isn’t pos­si­ble.

There is some good news. Last June, Canadian con­ser­va­tion au­thor­i­ties an­nounced the suc­cess­ful use of liq­uid fer­til­izer — potash — to kill in­va­sive mussels on a test site in Man­i­toba.

More­over, an im­por­tant dis­cov­ery last sum­mer gave re­searchers some­thing to cheer about. Mar­tel and oth­ers found what is po­ten­tially the largest pop­u­la­tion of the rare hick­o­rynut mus­sel in Canada near the town of Waltham, Que­bec, in the Ottawa River. This means that there are still pock­ets of the river where the hick­o­rynut is do­ing its job — and thriv­ing. And it gives ex­perts like Mar­tel a clue to how to re­ha­bil­i­tate the river and re­vive na­tive mus­sel pop­u­la­tions.

But all the blame for the state of the Ottawa River can’t be placed on mussels. Af­ter all, what species in­tro­duced ze­bra mussels into the rivers in the first place? (Hint: it rhymes with sch­mu­mans).

As Mar­tel points out, we are also re­spon­si­ble for cre­at­ing other stresses, such as dams, on na­tive mus­sel species. “The Ottawa River is no ex­cep­tion. We’ve got dozens of dams on the river — it’s one of the more heav­ily im­pounded rivers in Canada,” says Mar­tel.

Dams block the migration of fish up and down the river and pre­vent gene ex­change among species, which re­duces ge­netic bio­di­ver­sity. They also pre­vent some species from spawn­ing and al­ter the shape of rivers, of­ten turn­ing them into lakes, which quashes any species that rely on shal­lower depths and mov­ing wa­ter, ex­plains Mar­tel. The stur­geon, a fish that plays a vi­tal role in the re­pro­duc­tion of mussels, thrives in rivers — not lakes.

Last fall, when coun­cil­lors at city hall were ap­prov­ing Wind­mill’s plan to de­velop at Chaudière Falls — and not re­turn the falls to their for­mer nat­u­ral state, sans dam — it is doubt­ful that the well-be­ing of the stur­geon was on the agenda. But if Chaudière is to be one of the most sus­tain­able com­mu­ni­ties on the planet, the on­go­ing in­va­sion by the ze­bra mus­sel, the plight of the hick­o­rynut mus­sel, and the ef­fects of the var­i­ous dams, not to men­tion the dump­ing of raw sewage, should be part of the con­ver­sa­tion.

Matt Har­ri­son is the se­nior edi­tor of

Ottawa Mag­a­zine.

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