The water conditions in the Strait of Georgia have always been marginal for bull kelp. The nutrients and salinity are too low and the temperature is too high in the growing season. Bull kelp needs a temperature of less than 15 degrees to grow properly. Prolonged temperatures over 17 degrees are fatal and temperatures over 19 degrees are immediately fatal. Starting in 2014, the temperatures in the Strait of Georgia rose above the fatal limit for bull kelp. The last time I saw bull kelp up in the Nanoose area was in 2015 at the Dolphin Beach dive site. Every Summer in the last several years, the weather buoys in the Strait of Georgia have been showing temperatures of 19-21 degrees. This year (2022) is a La Nina year which brings cooler temperatures. This Spring has been unusually cold and I was wondering if this would allow some bull kelp to try and grow in the Strait of Georgia. I heard of a sighting of some bull kelp at the dive site at the end of Oak Leaf Drive so I wanted to check on its condition. I only started diving this spot in 2016 when it became accessible from shore so I don't know if there used to be bull kelp here before the temperature increase.
The following images are from the day I dove here (June 25, 2022). They are models from LiveOcean:
You can see the difference in temperature, nutrients (nitrates) and salinity between the Strait of Georgia and the Strait of Juan de Fuca (where bull kelp is thriving). In particular, the nutrient levels in the Strait of Georgia are extremely low so even though the temperature might be just cool enough for the kelp to survive, there aren't enough nutrients for it to grow properly.
As mentioned, I came up here for a dive on June 25, 2022.
The shallows were full of the usual Sargassum (Japanese wireweed), an invasive species that prefers warmer water compared to bull kelp and has become common in warmer areas like the Strait of Georgia and Saanich Inlet.
I reached the bull kelp. There were only 5 plants. 3 of them were 4-6' tall and 2 were less than 1'. The weather buoys on this day were reading 13-14 degrees in the Strait of Georgia and my dive computer's thermometer read 14 degrees near the kelp. This is within the range for bull kelp growth, but the effect of low nutrients and low salinity was obvious with these individuals. While the bull kelp in the Strait of Juan de Fuca is already 20' high and forming large forests, these ones were small, pale and stunted, with thin and short fronds. A few days after I dove here, the temperature warmed up and the weather buoys were showing a temperature of over 17 degrees, which makes me think that this bull kelp will soon die off.
I had heard of some misguided people illegally killing lots of urchins here by stabbing them with their dive knives, probably in an effort to "save the kelp". I still can't understand why so many people still blame urchins for the lack of kelp in the Strait of Georgia, where water conditions are fatal to bull kelp. It's like blaming polar bear predation for alligators not being able to thrive in the arctic. The Strait of Juan de Fuca has lots of healthy bull kelp and lots of urchins and the urchins don't destroy the kelp there. Maybe Strait of Juan de Fuca urchins are really dumb and can't figure out how to devastate kelp beds. Anyway, I saw lots of these killed urchins along the bottom in the shallows.
Instead of wiping out non-existent kelp beds, green urchins graze away the coating of diatoms that smothers the rocks, allowing a hard surface for invertebrate larvae and kelp spores to settle and attach. Much of the rocks here in the shallows were covered with these slimy fuzzy diatom growths. I could see where some green urchins had grazed away areas of it, exposing the rock underneath. Visibility in the shallows by the way, was only about 8-10'.
I swam down along the wall that drops down along the point. The water started to clear below 30' deep and below 60' deep, visibility was 40-50'.
I did a second dive here on the same day. This time I went out to the farther, deeper wall. For years, when I've been diving this area I've seen several semi-large yelloweye rockfish. This spot had the most I've seen anywhere. There were also a few tiger rockfish. Last time I was here (this Winter), they all seemed to be gone. I wanted to dive here again in a different season to see if they were still absent. In previous years, I always saw the individual yelloweye and tiger rockfish in the same spots. Today, these spots were still empty. I didn't see any tiger rockfish. As far as the yelloweye rockfish, most of them still seemed to be gone. I did see 1 small juvenile, 1 smaller semi-adult (maybe only a couple of decades old) and at my deepest depth (130') I saw probably the biggest one I've ever seen (probably over a foot and a half). It still seems strange that most of them are gone. The absence of tiger rockfish seems especially suspicious since they usually don't move far from their tiny territories.
