The broad siltstone bench at Pillar Point is one of the most highly visited intertidal sites in California. It’s easily accessible, close to the San Francisco Bay Area, and with recreational users in mind, was intentionally excluded from the system of Marine Protected Areas established in California starting in 2007. Since 2012 it has also been a hub of community science, with a popular and ongoing biodiversity monitoring program coordinated by the California Academy of Sciences and iNaturalist (https://www.inaturalist.org/projects/intertidal-biodiversity-survey-at-pillar-point)
Well before these milestones - including the launch of iNaturalist out of the Bay Area in 2008 - two dedicated biology teachers from California High School in San Ramon had quietly started recording the numbers and species of nudibranchs at Pillar Point. From late 1988 to late 1996, Bill Pence and his former student Douglas Mason, out of pure interest and curiosity, and sometimes accompanied by a few of their students, conducted 103 surveys, frequently twice a month, at Pillar Point, focusing their observations on a set of 10 tide pools on the outer reaches of the bench.
“The original motivation for me was simply to be out in the marine environment interacting with those fascinating creatures and it wasn't until later that questions regarding nudibranch seasonality and abundances occurred to Bill and me, and we started recording data. Our plan then was to visit Pillar Point regularly (twice per month if we could) and record nudibranch species and numbers. In the beginning, we rarely encountered other people out on the shelf and usually had the place to ourselves. I am not sure that we knew how we were going to use the data, but we hoped we might see patterns that would help us understand why, for example, we saw hundreds of Doriopsilla albopunctata in some months and very few of them in other months (I was getting my degree in philosophy at the time and had only taken a few biology courses-- much later I got a degree in biology). Bill and I had hundreds of hours of direct physical and intellectual pleasure gathering that data.”
“We were generally on our hands and knees, slowly crawling through the pools, combing algae, looking under ledges, and in crevices. Since many ‘branchs are tiny (e.g., species of Doto and Cuthona), this type of searching was slow and methodical, and we often used hand lenses for better identification. For difficult identifications, we collected the ‘branch and at the end of our collecting period looked at it under a dissecting scope we had brought with us into the field.”
Bill had been introduced to the richness of the rocky intertidal on an Invertebrate Zoology field trip to Pigeon Point as a freshman at San Jose State University, and Douglas had first been introduced to Pillar Point on an Invertebrate Zoology field trip under Dr. Ned Lyke at CSU Hayward (now CSU East Bay). First Bill, then Douglas carried on that tradition throughout their own teaching careers, which overlapped for years at California High School.
In 2007, soon after I had received a grant to resurvey three sites of historical, multi-year surveys of nudibranchs in California, I happened to meet Ned Lyke at a memorial symposium honoring Dr. Cadet Hand, former Director of the Bodega Marine Laboratory. Ned told me about two teachers - one a former student of his - who had nearly a decade’s worth of regularly collected data on nudibranchs from Pillar Point. He put me in touch with Bill and Douglas, who had been fretting now and then about what to do with their data, and not only did they share their data with me, they also offered to restart sampling Pillar Point as part of the new study!
Long story short, Bill and Douglas, now assisted by Phil Dobry, one of their former students, added another three years to their Pillar Point dataset - and then extended that to 2020! If their sampling frequency at Pillar Point became reduced, it was only because these now unassuming legends had spread out along the coast to explore new sites (and in the process I am certain, regain some of the peace and quiet familiar from their early years at Pillar Point). All years combined, Bill and Douglas made 137 trips to Pillar Point in 100 different months and recorded 14,718 individuals in 56 species (see Table 1: https://drive.google.com/file/d/1FBbNtXVkswsvpZW9MHBEwEDoufe1grec/view?usp=sharing). These numbers are remarkable because they were all nudibranchs and none of the other types of sea slugs, like bubble snails and sacoglossans, that can numerically dominate some sites.
They found the first Phidiana hiltoni known from Pillar Point (in January 1991), recorded exceedingly high densities of Doriopsilla albopunctata s.l. in summer 1989, and during the 2015-16 El Niño Douglas recorded unprecedented numbers of Okenia rosacea.
Bill and Douglas have not only provided an invaluable baseline for future ecological studies on nudibranchs in California, they have built, one identification at a time, a legacy among dedicated California ‘branchers.
Bill and Douglas were included as authors on a scientific 2011 paper in Limnology and Oceanography which relied extensively on their data from Pillar Point through 2008 (see: https://drive.google.com/file/d/1e1-kFHbO3rps6BQFV_H1ZWMEqffakW2l/view?usp=sharing), and the three of us plan a paper focused on the long-term results from Pillar Point. In addition, Bill and Douglas’ results from other sites have contributed significantly to papers published on nudibranch range shifts on the west coast associated with the marine heat waves of 2014-16:
https://drive.google.com/file/d/1ZjxYm05VgAqxWprC22-jGfb55CyLa74L/view?usp=drive_link
https://drive.google.com/file/d/1x-nAcNvFUa2n5mG4G-AaR8zcjs51Bn8r/view?usp=drive_link
https://www.researchgate.net/publication/331688590_Widespread_shifts_in_the_coastal_biota_of_northern_California_during_the_2014-2016_marine_heatwaves
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