Mill Creek at Big Sur

Macrocystis pyrifera (giant kelp) growing in a shallow pool in the intertidal.

Big Sur is one of my favorite places along the northeastern Pacific coast. Here the Santa Lucia Range presses against the Pacific coast, forming rugged rocky shoreline next to steeply cut valleys filled with redwoods and hillside slopes of chaparral and grassland.  

Much of the area is designated as California State Parks or National Forest (including wilderness) land. Big Sur has the usual California problems of invasive species, but the area has historically endured relatively little development. Tourists stream in along Highway 1 (in seemingly greater volume), particularly from the Monterey Peninsula, but much of the shoreline and coast range is too rugged for heavy human use.

I have a few favorite intertidal locations in Big Sur that I’ve visited intermittently over the years to tidepool, photograph marine life, or just collect seaweeds. Actually, quite a bit of the coastline is relatively inaccessible because of its steep topography, or for other reasons. For this month’s early morning spring tides, I visited Mill Creek on the southern Big Sur coast. Because of the early morning tide, I camped Sunday night at Plaskett Creek, and then Monday morning was lucky to have Mill Creek’s rocky stretch of coastline to myself.

Sea stars at Mill Creek, including Henricia leviuscula (center) and two examples of what may be
Leptasterias, a species complex of 6-armed Pacific coast stars. 

Desmarestia munda, acid (!) "kelp".

Excellent low tides notwithstanding, large swells offshore can keep the low intertidal relatively inaccessible for those wishing to stay relatively dry, but one solution to this is to don a wetsuit, at least up to one’s stomach, and make way into the low intertidal and the deeper intertidal pools. With some decent off-shore waves, this trip benefited from that method and I was able to access the deeper pools and photograph quite a few marine treasures with my underwater camera.

Mill Creek has a good mix of seaweeds (large brown seaweeds, foliose and finely-branched red algae, and some green algal species), seagrass (Phyllospadix) and invertebrates (anemones, seastars, mussels, etc.) – an example of a high diversity, less disturbed stretch of central California coastline. The substrate here is a field of large boulders, a cobble beach, and larger bedrocks with areas of coarse sand. The boulders tend to be rather large and are covered generously with algae and invertebrates.

Small seastars were common this month. Many were the whitish Leptasterias spp. (a six armed star typically a few cm across), but some were also juveniles of larger species. These new recruits perhaps represent local evidence of the reported rebound in sea star populations after the wasting disease phenomenon that led to a crash in west coast sea star populations in the last couple years.

Brightly-colored nudibranchs were also abundant and I spent some time photographing these beautiful animals underwater in the shallow pools. I observed at least 5 to 6 species including Okenia rosacea, which has seemed pretty abundant across the central to northern California coast over the last year. Yellow dorids were the most common on this trip ato Mill Creek. 

Two Mill Creek nudibranchs. Left: Triopha catalinae. Right: Dendrodoris fulva or Doriopsilla albopunctata.

Hermissenda crassicornis on articulated red coralline algae.

References

Behrens DW. 1991. Pacific Coast Nudibranchs. Sea Challengers, Monterey, CA.

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

Nudibranchs

Rocky intertidal habitats can burst with color. In Pacific tidepools, among the most colorful organisms are beautiful sea slugs, or nudibranchs. They are roughly similar in size to their shell-less cousins on land, but they are not at all drab like terrestrial slugs.

Scientifically, nudibranchs are classified in an order (Nudibranchia) within a subclass of mollusks known as the opisthobranchs. There are several other groups of opisthobranchs, including sea hares. The nudibranchs themselves are divided into a few groups. The most common are dorid nudibranchs, which have a tuft of gills on the top of the body midway, or towards the posterior end of the animal. Another group, the aeolid nudibranchs, is showy, having rows of protrusions (cerata) along the top of the body. While many molluscs have hard shells for protection (clams and limpets for example), the sea slugs do without. The nudibranchs are predators, feeding on other invertebrates and sometimes on other nudibranchs. Their bright colors may serve as a warning to potential predators that might be tempted to eat these soft-bodied morsels.

Hermissenda crassicornis, an aeolid nudibranch, from Greyhound Rock, Santa Cruz Co, CA, June 2015.

With such delicate bodies, it is a wonder that sea slugs can survive on wave-pounded coasts. Clinging to seaweeds in calm pools at low tide, within a few short hours, the rising tide will bring crashing waves and turbulence. Other intertidal invertebrates – mussels, limpets, chitons and barnacles for example – cling with great tenacity to intertidal rocks to withstand strong hydrologic forces within their environment. The marine algae have a different strategy: they typically have flexible branches or stipes that allow them to be passively whipped back and forth as waves rush over them. How do the delicate nudibranchs make it? Do they retreat into refuges among the rocks when hydrologic chaos is at its greatest?

Triopha catalinea, a dorid nudibranch, at Greyhound Rock. 

I’ve seen quite a few nudibranchs on intertidal trips this year to the central California coast. For example, during a very brief stop at Greyhound Rock in northern Santa Cruz County in June I found four different species in the low intertidal. The most colorful was a single individual of Triopha catalinae, a few centimeters long. Clinging to a strand of feather boa kelp (Egregia menziesii) right at the water’s surface, the milky white body punctuated with bright orange spots was a striking contrast with the chocolate brown kelp below.

One of the most common nudibranch species this year has been the distinctive Okenia rosacea, or Hopkin’s rose. I found close to a dozen animals in just a half hour of tidepooling at Greyhound Rock. In fact, I’ve seen this species on many of the intertidal trips I took this spring in California: Pigeon Point in San Mateo County, Glass Beach in Mendocino County, and at Sand Dollar and Mill Creek in Big Sur. Essentially a hot pink mess of slug, there is nothing quite like it on the coast and you can’t miss it!

Okenia rosacea (formerly known as Hopkinsia rosacea) from Pigeon Point,
San Mateo County, CA, October 2009.

References

Behrens DW. 1991. Pacific Coast Nudibranchs. Sea Challengers, Monterey, CA.

 ...also, check out the Sea SlugForum

Carmel tidepools

Costaria costata, 2014.

The Monterey Bay area is one of the coastal gems of California: strikingly beautiful marine life, diverse and easily accessible tide pools, and a rich tradition of marine research and education. Ever since my undergraduate days at UC Santa Cruz, I've loved to explore tidepools from the San Mateo County coastline south to Monterey and Big Sur. Spring-time low tides are an ideal period to visit the rocky intertidal, though that often necessitates an early rise of 5 or 6 AM to catch the action.

Carmel Point is one of my favorite places to tidepool. It is a few minutes south of the Monterey Peninsula by car. The town of Carmel is probably one of the most affluent coastal communities in California, but it is small and has a laid back feel. Carmel Point is a short stretch of rocky coastline that interrupts two more-or-less crescent shaped coves of sandy beach to the north and south. Offshore kelp forests run right into the low intertidal, so at the right times one can literally walk through a grove of giant kelp by just getting wet up to the knees.

Panorama at Carmel Point. Tidepools extend to the south. The Monterey peninsula is in the distance at center and right.

Corallina officinalis, 2014.

Carmel Point is an incredible spot for seaweed lovers like myself. There are interesting finds in all of the three major phyla of marine seaweeds. Green seaweeds are represented by alluring plants like "dead man's fingers" (Codium fragile) and the delicate Bryopsis. Reds appear in their varied hues, including the rich blades of Chondracanthus and Erythrophyllum delesserioides. There are various species of branching coralline algae in the lower to mid intertidal, lending a vibrant pink to the mosiac of benthic organisms on the rocks. 

Low intertidal Macrocystis pyrifera, 2007.

And, of course the large and conspicious brown algae are very diverse here. In addition to long strands of giant kelp (Macrocystis pyrifera) in the intertidal, there is bull kelp (Nereocystis), low intertidal groves of Laminaria setchellii and occurrences of feather boa kelp (Egregia menziesii) and Alaria marginata. The higher rocks host several species of rockweeds: Fucus distichus, Pelvetiopsis limitata, Silvetia compressa and Hesperophycus californicus.

Chondracanthus exasperatus, 2014.

I've made a half dozen or so trips to this site over the years, so I'm starting to have a few places I can check for favorite seaweed species. For instance, I've observed during intermittent visits a mid-intertidal population of the sea palm, Postelsia palmaeformis. The population this year grew on only a single rock, and plants looked a little tattered. One of my all time favorite kelp species, Costaria costata, appeared to be pretty common this spring. I found it in a usual pool just south of the Postelsia rock and in a high density at another low intertidal spot.

The nudibranch Triopha maculata on an opaque tunicate, 2014.

While tidepooling, my attention is usually taken with the seaweeds, but occasionally I notice some showy invertebrates too. This spring I found three species of colorful nudibranchs. On a previous visit I found a really cool green shrimp, its body colored perhaps from ingesting green algae.

Super cool green shrimp, 2009.

A small bull kelp, Nereocystis luetkeana,
submerged in a tidepool, 2010.

One thing I thought of during my visit this spring to Carmel was the intellectual challenge of understanding the ecology of these diverse rocky intertidal communities. There are literally hundreds of species of benthic algae and invertebrates packed tightly into the complex amalgam of bedrock, boulders and sand. Sure, there is the obvious vertical zonation of species that is driven heavily by the tides, but there is also so much three dimensional habitat structure creating seemingly infinite combinations of light, wave energy, sand scour and temperature. Add to these physical gradients the host of possible biological interactions (competition, herbivory, facilitation) among the dozens of co-existing species, and the unique life history patterns of immense phylogenetic diversity, and comprehension of the grand picture can seem unattainable. So, an observation here or experiment there that lends insight into these incredible ecosystems is a tremendous intellectual reward.

The strawberry anemone, Corynactis californica, growing underwater in the low intertidal, 2014. 

This is a small red alga, Pterosiphonia dendroidea, that I captured with my macro lens growing in a sandy area at Carmel Point in 2009. Most fronds of this plant are only a few cm in length. I love how individual cells can be seen on this plant!