I’d like to share a different perspective on shellfish aquaculture in the Gorge. Shellfish rafts especially for oysters, create tremendous three dimensional structure in the water column that supports a very prolific ecosystem. Have a look at the video of the dive I did on Nov 28th at the Bee Islets in the Gorge. Here is the link to the 9 1/2 minute Youtube video Bee Islets Dive https://www.youtube.com/watch?v=ZLumyWyG3nA
There have been concerns that the sheer mass of shellfish growing from these rafts creates tons of fecal waste. As you can see, the oyster clusters and the water around them are clean. The feces are probably being recycled through the anemones, sea cucumbers, tube worms and many more of the creatures that live in association with the oysters.
Over the years, reefs of oyster shell mixed with some plastics and other debris have formed under the rafts. The soft bodies of anemones and sea cucumbers rapidly break down when the animals are dumped overboard during oyster harvesting operations. The sea stars likely survive- I have seen masses of them under there on other dives. Oyster shell and other materials such as some plastic persist in the environment for a long time and sink from the rafts and form a matrix on the bottom. The plastics; line, trays, vexar bags are lost off the rafts and sink to join the substrate. Far from the UV degrading effects of sunlight and with little mechanism for physical break down, these sunken plastics are probably pretty inert.
You will notice in the video that the sediment layer is very light and no deep ooze with bacterial mats exist here. In fact, in diving widely throughout the Gorge, I have seen that most of the bottom is clean rock, sand, gravel and mud. I did a dive at the log dump about 10 years ago and there the cedar and fir bark mulches the bottom creating an anoxic and stagnant environment resulting in a stinking ooze that is covered by bacterial mats.
If the shellfish growers stop the loss of plastics into the water (especially styrofoam and other floating plastics that do breakdown into micro-plastics) and they conduct their operations in harmony with the other human and wildlife populations that use the Gorge, then shellfish aquaculture is a fairly benign and sustainable way to produce protein from the sea.
One other thing that I would like you to consider as you watch the video is that the tidal currents in Active, Porlier and Gabriola Passages and Haro Strait are even more vibrant and jam packed with life as the oyster rafts. Now imagine an oil spill. It’s not just beaches and orca that we need to worry about. It is this whole complex and beautiful ecosystem that is the basis for life in the Salish Sea.
Here is the link to the 9 1/2 minute Youtube video Bee Islets Dive https://www.youtube.com/watch?v=ZLumyWyG3nA