2014 Intertidal Ecology Survey
White Rock State Marine Conservation Area (SMCA)
Field Survey Report
James Landers, March 13, 2014
(Revised November 26, 2014)
Abstract. A small survey plot in the White Rock State Marine Conservation Area at Cambria, California, exhibits less diversity than might be expected of the rocky intertidal along the Pacific coast. The middle and lower intertidal zones are dominated by Brillo Pad algae (Endocladia muricata), stunted Turkish towel (Mastocarpus papillatus) and black turban snails (Tegula funebralis), and about half the rock surface in those zones is encrusted with tar spot algae (Petrocelis). Moreover, animals common in the intertidal of immediately surrounding areas are not found at the location surveyed.
Introduction. This document is the first of several that will report the findings of a 2014 study of the ecology of intertidal invertebrate and marine plant communities between Point Conception and Point Arena on the central California coast. The primary objective of the study is to record detail of environmental conditions and catalogue invertebrate species at selected survey sites. Secondarily, further evaluation will be made of one species, the owl limpet Lottia gigantea, previously observed in 2001 at Fitzgerald Marine Reserve in Moss Beach CA. Finally, related topics of previous research on the intertidal ecology of the California coast will also be considered as opportunity permits.
The data underlying this report are in the accompanying White Rock SMCA Field Observation Data Sheet (see under Category “Field Data”). That document contains detail observations of conditions and specimens in each of the four intertidal zones, as well as photographs of the specimens cited here.
Survey Site. The site surveyed for this report is White Rock State Marine Conservation Area at the Harvey Street Coastal Access in Cambria, California, latitude 35°32’36.48″ N, longitude 121°05’41.01″ W. The shoreline consists of fully exposed open coast with ten to thirty foot bluffs below residential housing, a narrow sand beach with a sewer drain above the beach, and a rocky intertidal consisting of wide, flat shelves of pitted extrusions of upper Cretaceous sandstone cut by narrow boulder-strewn crevices.
The survey date was March 13, 2014. The day was clear and sunny with westerly wind of 0-5mph. At 9:00am high tide there were large breakers eight to ten feet in height; these tapered off by mid-tide around noon. Water quality in the intertidal was slightly turbid due to sand scour. Tides were as follows:
|High level||Low level||Start Time|
|Zone 1||4.89||3.69||8:56 AM|
|Zone 2||3.695||2.5||11:00 AM|
|Zone 3||2.5||1.305||1:00 PM|
|Zone 4||1.305||0.11||3:39 PM|
Maximum tidal ranges this year for this location cited in Tide tables are as follows:
|High Level||Low Level|
Air temperature was 71° Fahrenheit (21.6° Centigrade). Temperature stratification, salinity, specific gravity, and pH were not sampled.
Methods. Mapping of the site was confirmed by reference to California Geological Survey, and National Oceanic and Atmospheric Administration (NOAA), maps. On-site survey methods were modified according to conditions at the site, uneven footing preventing laying out transects and quadrats. Instead, a survey area of rocky intertidal 100 feet x 30 feet (33 meters by 10 meters) was determined and a less rigorous approach of visual observation and scaled estimation of species abundance was employed in an environment where specimens occurred in patches and clumps rather than evenly distributed over a level substrate [Murray, et. al., “Methods for Performing Monitoring….”].
Data for each Zone was recorded separately.
Zone 1. This zone was sparsely populated by small common periwinkles (Littorina planaxis) together with an occasional small checkered periwinkle (Littorina scutulata), ribbed limpets (Lottia, or Acmaea, digitalis) grouped in crevices, but surprisingly by almost no barnacles (Balanus) or any other plants or animals. The surface of the rock shelves in this splash zone were devoid of life, with the exception of one rock that exhibited a large number of tiny barnacles, Balanus spp. [Rev. 2014-11-27: as acorn barnacles are an indicator species for Zone 1, our original assignment of these barnacles to a lower zone had to be an error resulting from not observing the high tide and, so, we reassign them to Zone 1. Furthermore, we reported only one species here; later, after we learned to distinguish Balanus and Chthamalus, re-examination of the photo of this rock showed both species present.]
Zone 2. Here were found a small number of ribbed limpets grouped in crevices, a moderate number of black turban snails (Tegula funebralis) and hermit crabs (Pagarus samuelis) occupying empty black turban snail shells in open pools, and a moderate number of small colonies of aggregating anemones (Anthopleura elegantissima) in crevices.
Rock weed (Pelvitopsis limitata) occurred here and there, among larger beds of Brillo Pad algae (Endocladia muricata) and stunted Turkish towel (Mastocarpus papillatus). Tar spot algae (Petrocelis) encrusted perhaps ten percent of the rocks in this zone.
Conspicuous by their absence were barnacles, mussels, sea stars, shore crabs, and sea urchins.
Zone 3. Barnacles, mussels, sea stars, shore crabs, and sea urchins were also absent from this zone. Petrocelis and Mastocarpus were dominant, covering about fifty percent of the rocks. Mastocarpus mixed in with Endocladia muricata covered the tops of rocks, while Petrocelis encrusted rocks down to the bottom of the zone, where it all stopped at the same level, like a snowline. Just below the Mastocarpus, numerous black turban snails clustered together in crevices.
An occasional ribbed limpet might be found on rock walls at this level, with more hermit crabs scrambling about the sandy bottom. Colonies of aggregating anemones were abundant on rocks, and giant green anemones (Anthopleura xanthogrammica) were common in pools.
One rock only exhibited a large number of tiny barnacles (Balanus).
Zone 4. Large patches of surf grass (Phyllospadix) grew in the bottom of pools, and red algae (Corallina) occurred less often on rocks. Black turban snails were abundant in crevices below Mastocarpus, colonies of aggregating anemones were common, and giant green anemones frequented the foot of rock walls.
One ten-inch-long reddish-orange gumboot chiton (Cryptochiton stelleri) was observed climbing over rocks at the bottom of a pool.
Discussion. The small scale of observation for this survey is understood to be inadequate to support any substantial conclusions. Larger samples studied over time will always yield more useful data. Therefore, discussion here is intended more as a point of departure for further inquiry.
Algal Cover. The plot surveyed was characterized by (1) the absence of a number of animals that might other be expected in the rocky intertidal of the Pacific coast, and (2) by the dominance in the middle and lower intertidal of Endocladia muricata, Macrocarpus and Tegula. At first, the area gave the impression of a community recovering from an oil spill, but then it became apparent that what looked like oil seepage on the rocks was Petrocelis, the early encrusting stage of Mastocarpus papillatus (the author is grateful to Melissa Boggs, Senior Environmental Scientist at the California Department of Fish and Wildlife, who suggested the identification of Petrocelis), not unexpected where Macrocarpus grows abundantly.
In Zone 3, Petrocelis occupies perhaps half the available rock surface and, as no other animals or plants were observed growing atop Petrocelis, may be a contributing factor to the reduced diversity of intertidal life at this location.
The presence of so large a population of Tegula may be related to the abundance of Macrocarpus, on which Tegula is known to feed [Zavela and Williams], as well as the absence of usual predators such as crabs and sea stars.
Species Diversity. There is no apparent reason why such common species as barnacles, mussels, sea stars, shore crabs, and sea urchins should be absent from the community surveyed. Specimens of these animals are listed consistently as present in immediately surrounding areas by the Coastal Biodiversity Survey of the University of California at Santa Cruz for the years 2001, 2005 and 2008 (see Species Lists in the White Rock Field Observation Data Sheet). Representative species listed included:
Balanus glandula, Acorn barnacle
Mytilus californianus, California mussel
Pachygrapsus crassipes, Striped shore crab
Pisaster ochraceus, Red sea star
Strongylocentrotus purpuratus, Purple sea urchin
California Geological Survey maps, http://www.quake.ca.gov/gmaps/GMC/stategeologicmap.html.
Carefoot, Thomas H., Pacific Seashores: A Guide to Intertidal Ecology, University of Washington Press, Seattle, 1977.
Coastal Biodiversity Survey, University of California, Santa Cruz, http://cbsurveys.ucsc.edu/index.html.
Endocladia muricata, http://depts.washington.edu/fhl/mb/Endocladia_Laura/Endocladia_home.html.
Gibbons, Helen and Bob Rosenbauer, Tom Lorenson, and Randy Imai, “Tar Balls from Southern California Seeps Appear on Central California Beaches,”, CDFG Office of Spill Prevention and Response, April 2008, http://soundwaves.usgs.gov/2008/04/fieldwork2.html
Littler, M. M. and D. S. Littler, 1985, “Nondestructive Sampling,” Pages 161-175 in M. M. Littler, and D. S. Littler, editors. Handbook of Phycological Methods, Cambridge University Press, Cambridge, UK, http://littlersworks.net/reprints/Littler1985d.pdf
Mastocarpus papillatus, http://bioweb.uwlax.edu/bio203/2011/lutz_jose/reproduction.htm
Metaxas, A., & Scheibling, R.E. (1993). Community structure and organization of tide pools. Marine Ecology Progress Series, 98, 187-198.
Murray, S.N. 1997. Effectiveness of marine life refuges on southern California shores. California and the World Ocean 1997. 1453-1465.
Murray, Steven N.et. al., “Methods for Performing Monitoring, Impact, and Ecological Studies on Rocky Shores,” U.S. Department of the Interior, Minerals Management Service, Pacific OCS Region, Camarillo CA, and Southern California Educational Initiative, Marine Science Institute University of California, Santa Barbara, CA, March 2002,http://www.coastalresearchcenter.ucsb.edu/scei/Files/2001-070.pdf.
Ricketts, Edward F. and Jack Calvin, Between Pacific Tides, Stanford University Press, Stanford, CA, 1981.
Smith, G. W., D. G. Howell, and R. V. Ingersoll. 1979. “Late Cretaceous trench-slope basins of central California,” Geology 7:303-306.
Zavala, Angelica and Susan L. Williams, “The Heat Is On: Tegula funebralis Grazing Intensity On Mastocarpus papillatus,” Department of Biological Science, Bodega Marine Laboratory, University of California Davis, undated, http://bml.ucdavis.edu/wp-content/pdf/REUPosters/ZavalaPoster.pdf
 How to tell the difference between encrusted Petrocelis and tar from oil seeps? Comparison of photos of tar from oil seeps on rocks show the deposits generally much blacker than the dark brownish encrusted Petrocelis. The pattern of encrustation can also be different – tar from oil seeps often flows over the face of rocks in recognizable “streams.” A certain indication of tar from oil seeps will be the absence of Mastocarpus papillatus in any form. Cursory inquiry turned up no reference to major oil spills in this area for many years, however studies of “tars and oils from natural seeps, offshore oil and gas platforms, and California shoreline…have shown that virtually all the tar balls that wash up on the California coast come from natural seeps of oil and tar derived from the Monterey Formation” underlying the offshore seabed [Gibbons, et. al. 2008].