Marine life could feel impact of floods for years to come

With the recent rainstorms, floods and landslides, the chief concern is, quite rightly, their impacts on B.C.’s residents’ safety and health.

We’re also paying attention to the damaged transportation routes that impede our ability to provide help and access to medical care, evacuate people and livestock, and move goods, and to the homes, businesses and farms flooded or destroyed.

But when the year’s storms tail off — and we’re all hoping that happens sooner than March — we’ll be better able to take stock of downstream damage.

For example, we already know this year’s floods could affect salmon stocks for years to come. Raging rivers and streams would have swept away incubating eggs and shot young salmon out to sea before their time, scoured or smothered critical spawning sites, and hampered salmon struggling upstream to spawn.

Other impacts will be less visible and perhaps harder to track. We might not know for some time what all the fertilizer, fuel, garbage, manure, pesticides and who knows what else, in addition to all the sediment flushed out to sea, will do to fish and the critical, fish-supporting eelgrass habitat in B.C. coastal waters. We might not know for months how many shellfish beds those toxic sediment plumes will smother.

We may not see for years the effects of the various bacteria, fungi and other microbes washed from the rich soils of now-flooded Lower Mainland dairy, pig and poultry farms and urban backyards.

But what happens on land can affect critters at sea. In one recent study, researchers from Canada and the U.S. Pacific Northwest pieced together the history of the outbreak of the deadly fungus Cryptococcus gattii in marine mammals.

Beginning on the Island, and then spreading to mainland B.C., Washington, Oregon and California, cases of humans, domestic animals and land-dwelling wildlife becoming infected with the fungi have been reported since 1999. In addition, porpoises and Pacific white-side dolphins in the Salish Sea are known to have died from the fungus. In fact, the first case of C. gattii in the Pacific Northwest likely occurred in a Dall’s porpoise in 1997 — two years before the region’s first-known human case.

Cryptococcus gattii is a land fungus. It lives in soil and trees. To become infected, a person or animal must breathe in the fungus’s spores. Only then can it cause lung and brain disease.

Construction, logging and other soil-disturbing activities can aerosolize the spores. Floods disturb soil and can aerosolize fungus spores, as well as wash them into waterways and out to sea. Once there, churning by waves and even raindrops striking the water can launch the spores into the air, where they can settle just over the sea’s surface, where sea mammals inhale them.

The study shows that marine mammals that died from C. gattii were found near terrestrial C. gattii hotspots.

Another recent study tracks how a parasite that reproduces like mad in the guts of cats affects wildlife in, near and downstream of densely populated urban areas.

The UBC-led study examined 45,000 cases of toxoplasmosis in wild mammals, using data from more than 200 global studies. Many species, including sea otters, seals, sea lions, dolphins and beluga whales, are susceptible to and can die from Toxoplasma gondii infection.

A single cat can poop out as many as 500 million of the parasite’s eggs (called oocysts) in two weeks. The eggs can live for years in soil and water. The researchers found wildlife living near dense urban areas were more likely to be infected than other animals.

In a 2020 study investigating disease and other factors in stranded orcas from the Pacific Northwest, researchers noted that an adult female orca examined had been infected with both Toxoplasma and Sarcocystis, another land-borne parasite that typically occurs in horses and opossums.

The farmyard-sea mammal parasite connection has also been confirmed in Eastern Canada with Neosporum caninum, dogs’ version of Toxoplasma, with cattle being an important intermediary host for the microbe’s spread.

In addition, Cryptosporidium and Giardia, well studied in terrestrial ecosystems, have been found infecting river otters and seals in Puget Sound, and seals and whales in eastern and northern Canada.

The recent rains and floods likely have washed many such land-lubbering parasites into the region’s waterways. How they will affect the vulnerable critters living in the sea downstream, and whether we will see those effects before the sick and dying animals sink beneath the waves, remains to be seen.