Boiler Bay

Boiler Bay rocky intertidal (north of the
small sandy cove). Is this the boiler from
which the site gained its name?

Although I lived in Oregon for several years (including a year and a half on the coast), I did less exploration of the rocky intertidal during those years than I would typically do during the same time span living in California. Oregon’s exceptionally scenic coastline features dunes, sandy beaches, rocky shores, and numerous estuaries. It was the latter ecosystem that I explored the most, working up and down the coast to research Oregon’s tidal wetlands.

For my last rocky shore visit of this month’s spring tide series, I wandered about the shores of Boiler Bay, a small cove north of Depot Bay on the central Oregon coast. A short steep trail leads to a small sandy beach at the head of the cove, with rocky intertidal benches to the north and south. Boiler Bay is apparently a well studied area, as evidenced by bolts and other obvious scientific interventions along the shoreline. I believe it may be a study site for Bruce Menge’s long-term study of Oregon’s rocky intertidal communities. South of the cove there was even a collection of dozens of small pools cut into the bedrock, too uniform in size and location to not be the hard work of a former research project, perhaps the sweat and tears of a graduate student dissertation from years past.

Various evidences of scientific interventions to study the rocky shore at Boiler Bay.

After observing for a few hours, an obvious ecological story of the Boiler Bay rocky intertidal is that of plant versus herbivore. Along the rocky benches south of the cove, large areas – dominated by purple urchins (Stronglyocentrotus purpuratus) in the thousands – are clearly claimed by herbivore. I don’t ever recall seeing intertidal urchins in such high densities anywhere else I’ve wandered on the west coast. The power of the urchins to shape this segment of coastline has even formed a geologic imprint: many of the urchins rest in small cavities carved into the rocks, the gradual work of spines that have eroded the mudstone over however many generations.

Small bull kelp in a tide pool at Boiler Bay.

Large fleshy seaweeds are prolific in other areas, away from the urchins. This means they are more abundant at higher shoreline elevations where urchins probably can’t tolerate the prolonged exposure to air, or in lower tidal areas where urchins perhaps aren’t able to gain high densities for other reasons. The large kelp Saccharina sessile grows in abundance higher on the shore out of reach of the grazing hordes, while Alaria marginata and Nereocystis luetkeana (bull kelp) occur in low intertidal pools or other fortuitous havens of safety. The elegant bull kelps typically occurred in aggregations as small to medium plants that will never reach the much larger stature that plants forming thick forests offshore will attain.

There is one notable kelp species that seems more impervious to the grazing menace of the purple urchins: Costaria costata. Having various common names like seersucker or five ribbed kelp, this striking species consists of a single, highly ruffled brown blade growing out of the base of the plant. Within the extensive urchin enclaves of the low intertidal at Boiler Bay, Costaria was present in remarkable abundance. The plants were typically small, and often tattered, but it was basically the only large seaweed common in the “barrens” where the purple urchins ruled.

Costaria costata sporophytes with abundant purple urchins in the low intertidal zone.

Costaria’s secret may lie in part from being an annual species. With quick growth in the spring, some plants may escape herbivory long enough to produce spores to continue the life cycle. Another possibility is that Costaria is a less preferred food source for the hungry urchins. Alternatively, competition might limit Costaria to urchin-dominated areas. In areas where perennial kelps like Laminaria setchellii or Pterygophora californica are present, perhaps the annual Costaria seldom gains the upper hand in competition with the established plants for space and light.

One important ecological force structuring coastal rocky shore ecosystems in Oregon however, lays obscured in history. Before being hunted severely to near extinction, the sea otter of the northeastern Pacific was a key predator of urchins, keeping grazers in check and promoting kelp abundance. This example of a marine “trophic cascade” was described decades ago in work done by ecologist Jim Estes. In a trophic cascade, healthy predator populations keep herbivore abundance low which favors primary producer populations. Today however, sea otters are essentially absent from Oregon’s coastline, so a key link in the historic web of connected coastal species is missing. Are Oregon urchin populations much higher today than they were several hundred years ago when otters were present? Whatever combination of mechanisms underlies the spatial patterns of distribution of urchins and Costaria, the observations suggest an interesting story.

Sponge in a low intertidal pool.

Large red urchins, Stronglyocentrotus franciscanus, were also relatively common at Boiler Bay, though their numbers are dwarfed by their smaller purple cousins. These grazers tended to be underwater (e.g., in pools), perhaps less tolerant of being exposed to air than their congener. Other intertidal invertebrates included beds of mussels, chitons, a few species of sea stars, and aggregating and solitary anemones. I observed no nudibranchs, but did see a few bright yellow sponges in the low intertidal and a lovely crab which I may try to identify when I am back in the company of a good reference book. 

Low intertidal crab at Boiler Bay.

Incredible plants: Nereocystis

I wrote previously about a fascinating intertidal kelp, the sea palm, found in the northeastern Pacific Ocean. A very close relative of this species is the bull kelp, Nereocystis luetkeana. This very large marine seaweed is a favorite beach find of kids (and more playful adults) since the flexible stipes of the plant make excellent ropes or whips during beach adventures.

Bull kelp forest at Deception Pass State Park, northern Washington, July 2013.

Despite the genetic similarity between Postelsia and Nereocystis, the bull kelp occupies a different habitat than Postelsia and has a rather different morphology. Nereocystis is principally a subtidal species with morphological features that are adapted for maximizing photosynthesis in deeper water. At the ocean bottom, plants are attached to a hard substratum with conical holdfasts that support long, thin, flexible stipes. Each stipe gradually expands into a semi-spherical pneumatocyst, the air bladder of the species. Several smooth strap-shaped blades emerge from the pneumatocyst at the top of each plant. Filled with mostly carbon monoxide (yes, the poison!), the function of the pneumatocyst is to help the blades stay afloat near the water surface.

A Nereocystis blade with sori (dark brown
patches) at Trinidad, Humboldt County,
California, August 2002.

Like all kelp species, the large plants seen along the coast actually only represent half of the kelp life cycle. The macroscopic plants are called sporophytes. The other, microscopic stage of the life cycle begins with the production of spores in tissues (called sori) that develop in the center of the blades of the sporophytes. The sori fall to the sea floor and release spores which develop into gametophytes - multicellular, but microscopic, filaments of cells on rock surfaces (Druehl 2000). Separate male and female gametophytes produce eggs and sperm and after fertilization of the egg, a new sporophyte generation is born.

 Nereocystis is one of only a few kelps worldwide that grows large enough to form subtidal kelp forests. Ecologically, such species are known as “foundation species” (Dayton 1972) because they literally provide the habitat structure upon which an entire ecosystem is built. Kelp forests are home to other numerous other species of macroalgae, invertebrates, fish and marine mammals. In the northern Pacific Ocean (the global hotspot of kelp diversity), other kelp species that are large enough to form forests include Macrocystis (giant kelp), Pelagophycus (elk kelp), and to some degree, Eualaria fistulosa and Egregia menziesii. Nereocystis is the main canopy-forming kelp species north of about Santa Cruz, California. From about Santa Cruz south to Baja California, Macrocystis is the main forest-forming species. In certain areas of the central California coastline, such as Big Sur, Macrocystis and Nereocystis can co-occur.

An intertidal bull kelp sporophyte with Costaria costata, Egregia
menziesii and other seaweeds, Carmel, Monterey County,
California, May 1999.

Like its relative Postelsia, Nereocystis is usually an annual species (Abbott and Hollenberg 1976). Most adult plants last no more than one growing season. With such a short life span and the capacity to attain a length of up to 36 meters, the bull kelp sporophyte has prodigious growth rates – estimated to be as much as 6-17 cm per day (Druehl 2000, Springer et al. 2010)! Though usually subtidal, bull kelps also occasionally grow in the intertidal and can be seen on a calm day at low tide. I love finding small sporophytes anywhere from a few inches to a few feet long during a low tide excursion.

To dive in a Nereocystis kelp forest is a delightful experience. One of my most memorable dives occurred during college at the Big Creek Ecological Reserve south of Monterey on the rugged Big Sur coast. There, in the frigid water I was able to observe the graceful stipes of bull kelps rising like kites up in the sea. The bull kelp is a stout but graceful plant, perfectly depicting the dual beauty and wildness of the Pacific coast.

References

Abbott IA and Hollenberg GJ. 1976. Marine Algae of California. Stanford University Press.

Dayton PK. 1972. Toward an understanding of community resilience and the potential effects of enrichment to the benthos at McMurdo Sound, Antarctica. In: Proceedings of the Colloquium on Conservation Problems in Antarctica.

Druehl LD. 2000. Pacific Seaweeds. Harbour Publishing.

Springer Y et al. 2010. Ecosystem based management of Nereocystis. Oceanography and Marine Biology: An Annual Review.

Deception Pass

This post is the final of 3 about my trip in early July to the Olympic Peninsula and Whidbey Island.

Heading out of Bowman Bay in Deception Pass State Park.

Luckily our trip to Washington coincided with some decent morning low tides. Since we had a new kayak with us, it was a great chance to do some “tidepooling" – not from land, but from the ocean's point of view. I launched the kayak at Bowman Bay in Deception Pass Stake Park and paddled on the north side of the bay towards Rosario Head. It was the same route that I took with my wife and oldest son a few years ago when we paid for a local kayaking tour. 


Map of Bowman Bay and Roasario Head. The red asterisk
marks the approximate location of the Cymathere population I found.





I explored the bull kelp (Nereocystis luetkeana) forests and a few of the rocky outcrops and islets that are so common in Puget Sound and the San Juan Islands. The exposed intertidal rocks were covered in large barnacles, and patches of cabbage kelp (Saccharina sessilis) and other seaweeds. I even saw a sea otter saunter down the from the exposed rocks of the intertidal and slip into the water. I've had no idea that otters made excursions onto land, but perhaps this animal was in search of tasty bivalves.

An otter notwithstanding, my scientific inclinations usually cause me to pay most attention to the plants. There was one particularly exciting find along a section of rugged coastline north of Rosario Head: a small population of several individuals of the kelp Cymathere triplicata. These long strapped shaped kelps were growing in shallow subtidal water right near the short surf zone. I hovered in place for some time trying to get some pictures of the Cymathere blades swirling hear the surface of the water.

Cymathere triplicata.

Cymathere is somewhat of a novelty for me because it does not occur in California or Oregon. It is distributed from Washington to Alaska (Druehl 2000). It is a relatively easy kelp to identify because of the presence of three ribs that run longitudinally down the thick blades. The north Pacific is the center of kelp diversity in the world, and this species is a special Washington treat.

The day had a little adrenaline too. At one point while observing the Cymathere specimens, I got a little too close to the surf zone and started to get pushed into rocks. Later in the day I took the kayak out a second time out of Bowman Bay and proceeded south into Deception Pass. The large wakes from the boats were a concern, but an even larger problem was that I began to be swept into the strong tidal currents that move tremendous volumes of water into the Pass and south towards Seattle. I realized what was occurring pretty quickly and turned around to make my way out of the pass, but found that I was essentially making no ground whatsoever despite paddling with all of my effort. I figured that the currents would be weaker closer to shore and found that I was able to make some progress on my return closer to the rocky shoreline. I wasn't in any particular danger, but if I had not been successful in turning around, I would have had to land at a beach somewhere else in the park and created a lot of work for myself to get the kayak back to the car.

The Washington Islands are a magical place and I have had the fortune to explore, kayak, collect seaweeds and conduct intertidal research among them.

References

Druehl, L.D. 2000. Pacific Seaweeds. Harbour Publishing, British Columbia.


Bull kelp forest in Bowman Bay.



  

Sand and snow

Usually the ocean moderates climate here on the west coast, pushing down summer temperatures and keeping winters mild.  However, sometimes winds shift or other meteorlogical magic occurs and the coast has a strange day.  I recall, for example, a warm summer morning on the beach in Monterey before a camping trip and another warm beach day in November at Pigeon Point north of Santa Cruz a few years ago.  This year, coastal Oregon turned bitterly cold the week of Thanksgiving.  That monday night there was a chance of snow right down to the coast.  I was excited when I took a peek through the window at flakes coming down during the middle of the night, and later woke up to a light covering of white powder at our house just a few blocks from the beach.  The rare snow event distrupted the routine here - schools closed and roads were very slick.  I went into work a little late on tuesday, intending to check out the coastal dunes and see how close the snow made it to the sea.  In the back dunes, leaves of salal cradled little accumulations of snow; ends of branches of the  coastal pine, Pinus contorta, were dusted white.  Thin snow drifts had accumulated in the little valleys between dunes.  The snow and surface crust of frozen ground extended right down onto the beach, perhaps as far as the last high tide had reached during the night.  Sure, it was modest and short-lived, but drift bull kelps (Nereocystis) in the sand mingled with ice crystals for a brief time.