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.

Grayback

Sucker Creek in southwestern Oregon.

I’m toward the beginning of a road tip through the northwest and the first days of the route have been similar to our trip last year about this time of year: tidepooling along the northern California coast and then a jaunt inland into southwestern Oregon near Oregon Caves NM.

Sunday night was spent at a lovely US Forest Service campground near Sucker Creek. The cool temperatures of the northern California coast were broken by a warm afternoon as we headed inland into Oregon. But in the early evening clouds grew to fill the forested sky and the low rumble of thunder could be heard in the distance. The thunder became more imminent and then rains came followed by a few minutes of hail. Rain (or hail), should realistically be expected at almost any time in Oregon. It is the elixir sustaining the evergreen brilliance of western Oregon.

Hail!

The storm was accompanied for a brief period of strong winds too, dislodging Douglas fir cones onto the campsite, swaying the trees above, and suspending sprays of conifer leaves in the air near the forest canopy. I was exhausted from a busy work week followed by two early mornings of intertidal work along the California coast and I fell asleep uncharacteristically early in the evening after the peak of the storm passed through. In the morning, the sky was blue and rays of the sun passed beams through the forest illuminating the humid summer air.

Five-fingered ferns (Adiantum aeluticum) grew on the far back of Sucker Creek across from the campsite. The water moved swiftly, apparently in greater volume than last year which was a drought year for the west. I saw no tiger lilies from afar as I had seen last year, but columbines grew near the base of a thin waterfall on the far bank. This location was impressed into my mind because of the fortunate circumstance of photographing a swallowtail butterfly feeding off the nectar of the lilies, two gorgeous organisms together! With the waterfall and attractive organisms, I recall that this little spot also had an outcropping of serpentine rock, a delightful occurrence of several of my favorites.

Abalones at Shelter Cove

As populated as California is, there are still remote areas that have relatively fewer people, especially in the northern half of the state. Opportunities to get away are protected behind the hassles of winding mountain roads or the labor of long trails. One has to simply be willing to get up earlier or hike farther, and the crowds can be left behind. However even with such effort expended, in California it is rare to be able to completely leave all other people behind. I know of a very small number of coastal areas where this is more or less possible, but I’d rather not name them.

Rocky intertidal at Shelter Cove, looking south.

One less crowded (though by no means secretive) stretch of California coastline is Shelter Cove at the southern end of Humboldt County. It is a small coastal community at the terminus of a torturous narrow road leading from US101 through the coastal redwood “curtain”. To the north and south of Shelter Cove are long stretches of more remote coastline – the King Range area – which I hope to explore more by trail some day.

I was fortunate to catch several of the exceptionally low tides over the Memorial Day weekend. My last stop of three consecutive days was Shelter Cove. It was a lovely morning of tidepooling, marking my return after some 14 years to this site. My first and only other visit was an intertidal adventure memorable in large degree because of a flooded camera. We drove south along US101, leaving the early morning rain in Eureka, and then turned toward the coast. The rain gave way clouds and then eventually to an increasingly sunny morning.

For the coastal explorer, Shelter Cove presents a few kilometers of compelling habitat. I returned to the southern-most stretch of coastline, just north of the cove proper, the approximate site of the deceased camera. Low tide exposed boulders, cobbles, and a meadow of small brown stipitate kelps. Here the usual low tide kelp dominant Laminaria setchellii, was joined by Pterygophora californica in about equal abundance. Some of the plants were tattered from the abuse of surf or herbivores.

Large brown seaweeds in the low intertidal at Shelter Cove. Laminaria setchellii (left)
and Stephanocystis osmundacea (right).

Pterygophora is a species I typically associate with subtidal kelp forests. Curiously, however it was common in the low intertidal zone at all three sites I visited in northern California for the long weekend. Another very common large brown species at Shelter Cove was Stephanocystis osmundacea (older name = Cystoseira osmundacea). Attached by a tough, almost woody base, this species is large enough to form underwater canopies like several of the kelps, but it is classified in a different order of brown seaweeds. The basal portion of the plant consists of flat pinnately-divided fronds. The top portion is more wiry in morphology and contains the most attractive part of the plant in my opinion: the concatenated pneumatocysts that look like strings of brown pearls, and which function by virtue of holding gases to keep the upper part of the plant afloat.

Stephanocystis osmundacea at Shelter Cove. Basal fronds underwater (left) and
apical portion of the plant with pneumatocysts (right).

The low intertidal into the shallow subtidal was littered with small cobbles which were covered in crustose coralline algae, brightening the substrate with pink and white. Because of their smaller size, the cobbles are likely unstable during periods of high surf, impeding any hope of long-term residence by fleshy seaweeds. The slow-growing, calcium carbonate-encrusted coralline algae however, seemed to find this sufficiently acceptable habitat.

Underwater branching and encrusting coralline algae at Shelter Cove.

In the low intertidal, a little above the water line, I soon discovered my first abalones of the day tucked into a tiny rocky ledge. There were nine individuals! In my experience, it is relatively unusual to find more than a few scattered individual abalones on any stretch of California coastline, but by the end of my wanderings that morning, I ended up counting some 77 or so over about 200 m of coastline.

Red abalones, Haliotis rufescens, in the intertidal at Shelter Cove.

The abalone hunters are well aware of the bounty present at Shelter Cove too. In fact, as I was likely the lone (bipedal) seaweed enthusiast at Shelter Cove that morning, I was quite outnumbered by divers wading in the shallow subtidal with wetsuits and donut-shaped floats looking for specimens of legal size. I have personally never tried the apparent delicacy of the expertly-prepared abalone. Despite my deep enjoyment of many things oceanic, I have generally never been too particularly interested in seafood.

Abalones are even more dedicated seaweed enthusiasts than me, feeding on kelp or other species of macroalgae. The slow-moving mollusks clamp down on a bit of sea salad as it floats by. For some species of abalone, an animal’s choice of seaweeds to dine on can be reflected in shell color. Consumption of red seaweeds, for instance, will lend the shell a reddish color from the pigment rufescine.

Abalones are gastropod mollusks, related to snails, limpets, and slugs. They occur worldwide, but attain their greatest size in the Pacific basin. Along the Pacific coast of North America there are seven species: red, black, green, pink, pinto, white, and flat.

Of these species, red abalones (Haliotis rufescens) seem to be the most common in northern California. It was this species I noted in relatively high abundance at Shelter Cove. The visible part of the tough muscular foot is black in color, protected underneath a generally pinkish to reddish pearly shell. A row of perforations near the margin of the shell are the site where gills expel water. In California this is the only species that can be fished, and even then, it can only be taken north of San Francisco, and by free diving, and during certain periods.

The only other abalone species I definitively recall seeing in the rocky intertidal is the black, H. cracherodii. I found a rare cluster of these organisms while tidepooling at Carmel Pt. south of Monterey in December of last year. Like some of the reds at Shelter Cove, these animals were wedged in a rock crevice. Black abalones occur from Mendocino County south to Baja California and can live at higher elevation in the intertidal than other species.

Black abalones, Haliotis cracherodii, in the intertidal at Carmel Pt.,
Monterey Co., CA, Dec 2016.

Unfortunately abalones tell a tale of coastal resource exploitation. After 20 years of tidepooling throughout California, my experience suggests it is relatively rare to see abalone in any significant number in the intertidal zone. Yet this was not always the case. Older photos from southern California decades ago show intertidal abalones in incredible abundance, covering much of the surface of the rock and crawling on top of each other! Overfishing, El Niño, and disease appear to have contributed to the severe loss of these important coastal ecosystem members. With declining numbers, rehabilitation of populations is now the key focus for these organisms.

Not all west coast species are equally threatened. While a fishery still exists for reds, white abalones (H. sorenseni) are so rare in the wild that they are in danger of going extinct. This species lives in southern California and Baja California in deeper waters. Whites were the first species of marine invertebrate to gain a federal listing of endangered in the United States. NOAA estimates that several thousand individuals still exist in the wild, but these adults may be the last cohort of a species at the edge of extinction. Mating success is dependent in adults being close enough to each other that sperm and eggs have a chance of meeting.

A group of researchers housed at UC Davis’s Bodega Marine Laboratory, are working hard to help recover this species. Black abalones are also federally endangered, having experienced a severe population decline in the last few decades.

References

Calif. Dept Fish Wildlife. No date. White Abalone Recovery Project.

Morris RH, Abbott DP, Haderlie EC. 1980. Intertidal Invertebrates of California. Stanford University Press, Stanford, CA.

NOAA Fisheries. 2015. Deeper understanding of ecosystems critical to recovery of West Coast abalone populations.

NOAA Fisheries. 2016. White Abalone (Haliotis sorenseni).

Ricketts EF, Calvin J, Hedgpeth, Phillips DW. 1985. Between Pacific Tides. 5^th ed. Stanford University Press, Stanford, CA.

Dermasterias imbricata at Shelter Cove.

Stephanocystis osmundacea from below.