Al­gae a bloom­ing prob­lem in Nova Sco­tia lakes

Harm­ful blue-green bac­te­ria “seems worse and worse each year,” says Dal­housie pro­fes­sor.


The head­lines are fre­quent and omi­nous. A quick Google search sum­mons warn­ing af­ter warn­ing: satel­lite im­ages of green spi­ral­ing across Lake Erie; health warn­ings plas­tered along rivers in Al­berta; three dogs in New Brunswick, dead.

Hal­i­fax is not im­mune. In Au­gust, the mu­nic­i­pal­ity is­sued a blue-green al­gae warn­ing for two Dart­mouth lakes, Banook and Mi’kmaq. Both ad­vi­sories re­main in place, now four weeks later.

Tri Nguyen-Quang, a pro­fes­sor of engi­neer­ing at Dal­housie Univer­sity, isn’t sur­prised. Across the prov­ince, he says, the blooms “seem worse and worse each year.”

Nguyen-Quang has been study­ing blue­green al­gae since 2009, try­ing to an­swer the fun­da­men­tal ques­tions of how and why these blooms hap­pen. He’s been busy. He mon­i­tors a cou­ple dozen lakes in Nova Sco­tia. It’s a task that keeps him work­ing at a fu­ri­ous pace—sam­pling, an­a­lyz­ing, re­port­ing, rinse and re­peat.

Every sum­mer it’s the same fran­tic rou­tine. But an­swer­ing the ques­tions of why and how takes plenty of data. Af­ter four years of sam­pling, only now does Nguyen-Quang say his small team can be­gin to build pre­dic­tive mod­els.

Blue-green al­gae are a kind of bac­te­ria— cyanobac­te­ria—in­clud­ing over 2,000 species. Mi­cro­scopic in size, cyanobac­te­ria are one of na­ture’s great­est min­i­mal­ists. Be­cause they need so lit­tle, they can sur­vive al­most any­where—from African deserts to Antarc­tic ice.

But Nova Sco­tia, home to 3,000 lakes, is no longer just a sur­viv­able habi­tat. The prov­ince’s wa­ters are be­com­ing ideal. Un­sur­pris­ingly, the fac­tors re­spon­si­ble are dis­tinctly hu­man.

There are un­con­trol­lable fac­tors at cause, like light, hu­mid­ity and tem­per­a­ture. And con­trol­lable fac­tors? It comes down to ni­tro­gen and phos­pho­rus, leech­ing into the wa­ter­shed from cracked sep­tic tanks, leak­ing sewage and the ubiq­ui­tous use of fer­til­iz­ers.

It’s the com­bi­na­tion of these fac­tors that’s par­tic­u­larly wor­ry­ing. As our planet con­tin­ues to warm, and if our wa­ter­sheds re­main ne­glected, Nguyen-Quang fears the blooms will only be­come worse.

If con­di­tions are right, cyanobac­te­ria— which usu­ally re­main at un­ob­tru­sive lev­els— re­pro­duce fu­ri­ously. One al­gal cell be­comes two, two be­come four; quickly a dar­ling swim­ming hole be­comes messy, cloudy soup. It hap­pens in fresh­wa­ter, it hap­pens in salt­wa­ter. Some blooms last days. Oth­ers, months.

And the list of symp­toms as­so­ci­ated with ex­po­sure is dis­turb­ing: rashes, red eyes, fevers, nau­sea and vom­it­ing, to name a few. Lists of al­gal tox­ins, on the other hand, are down­right ter­ri­fy­ing: neu­ro­tox­ins, hep­a­to­tox­ins, der­ma­tox­ins—even one un­set­tlingly chris­tened the Very Fast Death Fac­tor.

To make mat­ters worse, while many prov­inces ex­pe­ri­ence a short rash of sum­mer blooms, in Nova Sco­tia they’re start­ing to ap­pear as late as Novem­ber.

Shut­ting down af­fected lakes is a good first step, Nguyen-Quang says. But it’s a tem­po­rary so­lu­tion. In the fu­ture, “we should think se­ri­ously about long-term mon­i­tor­ing.”

If you see signs of a bloom—blue or green scum on the sur­face of the wa­ter—keep on dry land, he ad­vises.

If you sus­pect an al­gal bloom contact HRM by calling 311 or email Nguyen-Quang at


Blooms in Dart­mouth’s Lake Banookand, inset, Yar­mouth

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