Now that we’ve entered the rainiest part of the year, I’ve been thinking about how all this water washing over the land and swelling the streams is affecting Puget Sound and the life it supports.

While our annual rains are important events ecologically, they also wash away certain byproducts of human land use, eventually delivering a disturbing array of substances into the Sound. Certainly a complex issue and by no means a new concern, stormwater runoff has gotten attention from regulatory and environmental agencies over the years, leading to numerous inter-organizational studies and closures of shellfish harvesting.

To be certain, the sudden influx of nutrients and water is a required signal for salmon to start heading upstream, but sometimes contaminants in the water disorient the fish’s senses, causing them to behave erratically, bump into things, roll belly-up and eventually die before they can successfully spawn.

I’ve seen this firsthand while volunteering with the U.S. Fish & Wildlife Service during fall salmon surveys in West Seattle’s Longfellow Creek. We would don chest waders and walk right through the middle of the creek, using a big walking stick for balance and poking into dark corners, trying to find resting fish. The vast majority of the salmon in this urban creek, and in some years upwards of 95 percent, would suffer what we called “pre-spawn mortality” and would die still full of eggs and sperm. Hydrocarbon byproducts of petroleum combustion have been thought to contribute, and studies are still ongoing. However, it is known that small amounts of copper can affect salmon’s sensory organs, preventing them from migrating properly and avoiding predators.

The state Department of Ecology (DOE) estimates that 33 to 80 tons of copper from terrestrial pesticides, brake pads and roofing materials enter Puget Sound via stormwater each year. Besides confusing salmon, copper substances are also known to kill algae, fish and crustaceans.

According to King County and DOE, storm runoff is the single largest contributor to toxic chemicals in Puget Sound and amounts to a third of the total water pollution. Just last month, DOE published its 297-page Toxics Loading Study, detailing the pathways, sources and impacts of some of the more ecologically dangerous chemicals. Not surprisingly, the state found that the “toxic load” of chemicals being delivered by our streams into the Sound is highest during rainstorms. Copper, petroleum products and mercury are rated as some of the highest priority chemicals washing into our collective waterways. DOE’s data show that 8,500 to 11,000 tons of oil and grease get washed into Puget Sound annually, mainly from motor oil leaks and minor gas spills during vehicle fueling. Most of the mercury being flushed into the Sound is from improper disposal of consumer products. All of these substances are toxic for many animals even at small concentrations.

Although they have a high impact, chemicals are only a small constituent of overall water runoff.  Nutrients, bacteria and sediment are the most common toxins in stormwater. Nutrients such as nitrogen and phosphorus are toxic only because of their overabundance, stimulating algal blooms that lead to oxygen-deprived waters, dead fish and toxic shellfish.

On Vashon, the nitrogen-loading study of Quartermaster Harbor has garnered much attention. The study has found that 17 percent of the total nitrogen originates from nearshore septic systems and a whopping 63 percent comes from stream runoff, the top sources of which are animal waste and agricultural fertilizers.

Fecal coliform bacteria, also from animal wastes, are a serious problem and have led to the closure of many shellfish and swimming beaches. In 1993, an EPA study found that three days of 100 dogs’ droppings is enough to close a bay to swimming and shellfish harvesting. Sediment mostly comes from construction sites and natural erosion processes. Too much sediment smothers all life, killing beds of eelgrass and fish eggs and destroying habitat.

We are so intimately connected to the water that it is easy to take it for granted. Keep in mind that anything and everything found on the ground can end up in stormwater runoff and can mean life or death for animals that live in the water. You can help by fixing leaks in your car, taking proper erosion control when clearing land, disposing of your trash and pet waste properly and not using or minimally using fertilizers and pesticides.

Clearly every one of us contributes to the toxic substances loading the water surrounding our Island. DOE director Ted Sturdevant said it best when he stated: “There is no single guilty culprit or industrial source. Most toxic chemicals are used in some way by all of us. They are in our homes and gardens. They’re produced when we develop land without adequate runoff controls, when we burn wood, when we drive and park our cars. We all share responsibility for finding solutions. If we want to protect Puget Sound, we need to find and use less toxic alternatives as we do our business and live our lives.”

— Adria Magrath is a biologist, teacher and nature photographer, as well as a Vashon Beach Naturalist.