**This blog entry orginally appeared on the website oceanspaces.org.**/p>
After finishing our survey of the Reading Rock SMR (see Part III) and waiting out our first big north coast storm of the season, we left Humboldt Bay on what seemed to be a break in the weather. Our research vessel (see Part I) was headed south to the Mattole Canyon SMR, a deep canyon that extends offshore from the Mattole Valley, which is located between Cape Mendocino and Punta Gorda. This section of the coast is part of the “lost coast” and it is the most remote part of the California coastline. The lost coast contains high rugged mountains that meet the ocean with sheer cliff faces. It is a geologically active landscape that has little shelter for ocean going vessels.
My survey plan for the Mattole Canyon SMR would start with dives on both rocky and soft bottom habitats found on the shelf area surrounding the canyon. Next we would survey the north and south sides of the canyon walls, including the interface between the self and the canyon. Lastly we would dive deep to the bottom of the canyon to a depth of 400 meters. “Two days should do it”, I said as we pulled away from the dock. One day I will live that statement down.
During the first three survey days wind gusts exceeding 25 knots combined with rough seas and very strong currents made surveying the canyon almost impossible. Each day we would leave the only nearby protected anchorage, Shelter Cove, and make the 3.5 hour trip to take advantage of the morning calm. After an hour or so on the bottom, the wind and seas would set in and we would have to leave. By day four I was starting to feel like I would never get this site done and I would have to leave with only a portion of my survey plan completed. On day five we woke at 5:30 am and the weather had finally turned in our favor; finally a full survey day to finish the deep dives.
With the Mattole Canyon SMR survey completed, I began to understand just of how dynamic that part of the coast can be. The soft bottom habitats there were very active, with strong currents sweeping across the shelf as they headed for the canyon. Typical soft bottom habitats at these depths have many traces of biological activity such as mounds, tracks and holes visible in the sediment, but not there. It is likely that the current scoured most of them away leaving only minimal traces behind. The occasional flat fish and small octopus were the most common inhabitants we saw on the shelf soft bottom habitats.
Patches of rocky reef were scattered throughout the self and there we found fish taking refuge from the strong currents. Canary rockfish and lingcod were the most common at the edge of the rock outcroppings, while quillback, rosy and yelloweye rockfish took shelter in the interior of the reef. Basket stars perched atop the rocks with their arms raised up into the current to feed, while both soft and hard corals took hold throughout the higher rocky reefs.
As we moved toward the edge of the canyon, fish were lined-up behind exposed rock outcroppings as the current flowed over the edge and downward into the canyon. The current was so strong there that I was almost unable to control the ROV over the transition. Feather stars held tight as the current ripped by, while juvenile canary and lingcod scanned the water for a “quick” meal. These downward flowing currents were observed on both sides of the canyon.
As I flew the ROV into the canyon, I passed over steep walls and rock faces. Small red octopus and numerous species of flatfish were seen on the steep soft bottom canyon slopes. Exposed rock walls protruded out into the canyon and were covered in a variety of colorful anemones, sponges and corals. As I decended the ROV, we spotted a giant Pacific octopus holding tight as it rested on one of the vertical rock walls, as did many thornyheads and aurora rockfish.
Our most difficult dive took us to the canyon floor at just over 400 meters deep. On the bottom, we observed a strong outward flowing current carrying debris, including marine organisms, out to sea. Sablefish, flatfish and big skates hunkered down on the canyon floor to likely take advantage of any small organism that got caught in the current. I set the ROV on the bottom to observe the current flow and was amazed by the volume of debris moving down the canyon. I took a moment and reflected on what I had seen so far. That on each side of the shelf, near the edge, there were currents flowing toward the canyon and once they reached the edge they flowed down with incredible force, like underwater waterfalls. The currents reached the canyon floor and flowed outward into the abyss, rich with marine debris. “Where does it go next and who is taking advantage of it?” I pondered.
With Mattole Canyon SMR behind us, we said good bye to the lost coast and continued our journey south toward Fort Bragg. Along the way we take a quick moment to demonstrate to some 7th grade students the extreme pressures associated with taking something to the bottom of the ocean. We also pick up a new friend and show him the place his family had always fished, but is now closed. Our next stop is the Ten Mile SMR, the last marine reserve we survey this season.