2014 Intertidal Ecology Survey
Fitzgerald Marine Reserve, Moss Beach CA
Field Survey Report
James Landers, April 7, 2014
Abstract. The Fitzgerald Marine Reserve (FMR) is protected seashore of 32 acres owned by the State of California, managed by San Mateo County as a county park, and supported by an active volunteer group. The reserve is located at Moss Beach CA, twenty miles south of San Francisco, on exposed open coast that extends for three miles from the Montara light to Pillar Point. The reserve’s intertidal zone consists of a formation of flat rock shelves protected by a barrier of several offshore reefs. Close to large metropolitan areas, the reserve is visited by over 100,000 people yearly [Tenera, 2004], placing great pressure on animal and plant life and complicating an understanding of diversity at that location. Although they have been noted as plentiful in the past at this location, this survey found few to no examples of sea stars, shore crabs, and sea urchins; mussels, Mytilus californianus, were abundant in several beds, but barnacles (Balanus) occurred only occasionally. Marine algae, however, are abundant in the FMR intertidal, covering large areas of the rock surface, in particular Endocladia muricata, Brillo Pad algae, and Neorhodomela larix, black pine rockweed, raising questions of how settlement can be accomplished by animals when so much space is taken by plants.
Introduction. This document is the third of several that 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 is in the accompanying Fitzgerald Marine Reserve Field Observation Data Sheet (see under Category “Field Data”). That document contains detail observations of conditions and specimens in each of the four intertidal zone, as well as photographs of the specimens cited here.
Survey Site. The site surveyed for this report is in the Gulf of the Farallones National Marine Sanctuary, at Moss Beach CA, latitude 37°31’25.36″ N, longitude 122°31’03.34″ W. The location is open coast about three miles above the north bight of Half Moon Bay. For the most part, the reserve consists of a sand beach at the foot of sixty-foot bluffs, atop which is a residential area from which drainage effluent flows down onto the beach via San Vicente Creek. Abutting the edge of the sand beach, wide, flat Pleistocene terrace deposits of massive, cross-stratified or laminated sandstone, extend in shelves mixed with boulder and granule conglomerate about fifty meters into the sublittoral. In a line about one hundred meters offshore, several long reefs break the incoming swell and provide a haul out for harbor seals. Two sites were surveyed, one just south of the north access down to the beach at Moss Beach Reef (aka Colorado Reef), and the other about 100 meters south of the first.
The first day of the survey was Sunday, April 6 2014, and between the morning low tide and noon mid-tide several hundred visitors, adults and children, climbed out onto the rock shelf and walked and ran about the survey sites. The morning was clear, then changed to light overcast toward midday. The wind generally was from the west (275°) at 10-15mph. Water quality was clear, and wave action moderate, with three to five foot combers breaking on the offshore reefs, where perhaps a dozen harbor seals were hauled out. Park rangers had roped off parts of the beach close to the harbor seals until later in the morning when the animals dispersed. The tides for this date were:
Maximum tidal ranges for this year at this location are:
|Highest level||Lowest level|
The following environmental conditions at the start of the survey period, between 8:00am and 12:00pm, were recorded.
Air temperature: 60° Fahrenheit (15.5° centigrade).
Water temperature: 57° Fahrenheit (13.8° centigrade).
Temperature stratification: not taken.
Salinity: 38.0 ppt.
Specific gravity: 1.028.
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 utilized one transect of 13.6 meters and five quadrats to quantify organisms in the selected Zone 2site, which encompassed an area of roughly 136 square meters of exposed rocky intertidal. In Zones 1, 3 and 4, a less rigorous approach of visual observation and scaled estimation of species abundance was employed in an environment where marine algae nearly completely covered the sandstone substrate and specimens were found only occasionally and did not occur evenly distributed over a level substrate [Murray, et. al., “Methods for Performing Monitoring….”].
Data for each Zone were recorded separately.
Zone 1. This zone at the FMR survey site is mostly sand beach with one small outcrop of gray and brown sandstone located immediately below the bluff about 50 yards south of the north access to the beach and San Vicente Creek. This small outcrop below the bluff is covered with about 45% tar spot algae (Petrocelis). Occasional solitary barnacles occur at intervals on the rest of the rock not covered by Petrocelis.
In the rock shelves west of the sand beach, occasional small brown sandstone outcroppings rise above the rock surface into Zone 1, and these are populated by Balanus spp. (but only on the brown stone and not on the gray, possibly Petrocelis permeated, stone at the base of the brown outcrops).
There are seven mussel beds 100 meters further south in the second survey area, west of the sand beach, and several are high enough in the intertidal zone to be treated as part of Zone 1. These seven mussel beds total about 60 square meters in a section of rock shelf roughly 90 meters long and varying from 27 to 36 meters wide. A count of mussels in these beds was found to average roughly 270 individuals per square meter (90 individuals per square foot). (Rev. November 27, 2014: a reviewer questions the location of mussels in Zone 1 as they are firmly established as an indicator species for Zone 3. Our estimate was based on visual observation of what appeared to be the relative position of these mussels, and the gooseneck barnacles with them, in the Fitzgerald intertidal zone (see discussion below). Observation of the tide cycle and height of the tide, together with closer examination of the mussel beds for other indicator species such as Cthamalus and Littorina, was not undertaken in our survey and, as a result, we have not sufficient evidence to justify assignment of these animals to Zone 1. As that is the case, and we may also have incorrectly identified all the zones at Fitzgerald, our assignment to zones of all the species we observed is questionable.)
Gooseneck barnacles (Pollicipes polymerus) occur in association with the mussel beds, in clumps around mussel bed peripheries, and also mixed in together with the mussels. Along the western edge of the mussel beds there are fourteen clumps of gooseneck barnacles. Each clump averages 120 individuals per square meter (40 individuals per square foot).
Zone 2. In this zone, the first survey site (Moss Beach Reef) is covered almost entirely by marine algae, a large bed of Neorhodomela larix, black pine rockweed, taking up over one half of the area. On the east and west sides of the first survey site, this rockweed transitions abruptly to Endocladia muricata, Brillo Pad algae, mixed with Mastocarpus papillatus, stunted Turkish towel, along the near straight line of Transect A. Anthopleura elegantissima, aggregating anemone, occur in crevices on bare surfaces of rock shelves in numbers of about 10 per square meter. Tegula funebralis, black turban snails, can be found in small numbers on bare rock and under Endocladia, together with occasional limpets and barnacles. Pin cushion algae (Cladophora) and two distinct varieties of so far unidentifiable encrusting algae also are found occasionally among the other algae and rockweed. One owl limpet (Lottia gigantea) – the only one seen at FMR ̶ was found in this zone. One mossy chiton and one plate limpet were also seen here.
Mussels and gooseneck barnacles here are the same as those described above; here they are located at the upper boundary of Zone 2 and merging into Zone 1 (see note in Zone 1).
Zone 3. In this zone, Endocladia, Mastocarpus, and Neorhodomela decline and are replaced toward the west side of the survey site by a salad bowl of other algae, including sea lettuce (Ulva), coral weed (Corallina), and Mazzaella californica, a relation of the Mazzaella sometimes called rainbow leaf. Aggregating anemone in numbers of about 35 per square meter cluster on the vertical rock faces of the occasional crevices dividing the rock shelves of this zone
Zone 4. This zone was under six inches to a foot of water when observed. Species present, in roughly equal numbers, included surf grass (Phyllospadix), coral weed (Corallina officinalis), sea lettuce (Ulva lactuca) and sea cabbage (Saccharina sessilis). Small amounts of black pine rockweed (Neorhodomela larix) were also seen. Not seen in this survey, but noted as present by the 2004 San Mateo County Parks Fitzgerald Marine Reserve Resource Assessment [Tenera, 2004] were:
(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.)
Zonation. Zonation was evident most clearly on the 1 to 1.5 meter high vertical rock faces of crevices that occasionally cut through the rock shelves of the FMR. The rock face shown in the top portion of Figure 1 indicates biotic zonation of one vertical rock face of the Moss Beach Reef shelf, delineating four zones and the biota that determined each (Zone 1 was distinguished by
mussels, goose-neck barnacles, and common barnacles). Zonation on the surface of the flat rock shelves was less obvious, following the gradual slope of the rock shelves over perhaps 20 meters out into the sublittoral. Figure 1 suggests the approximate biotic zonation for the flat rock surface as it corresponded with the same zonation on the vertical rock face.
|Figure 1. Zonation at FMR. The upper portion is a 1 meter high vertical rock face on which biotic zonation is clearly evident. The lower portion is a section of the Moss Beach Reef rock shelf which slopes gradually into the sublittoral. The yellow lines indicate corresponding zonation.|
Algal Cover. Substantial surfaces of our survey site in Zone 2 were occupied by marine algae, predominantly Neorhodomela larix, black pine rockweed, Endocladia muricata, Brillo Pad algae, and Mastocarpus papillatus, stunted Turkish towel. A similar abundance of these algae has been reported in resource assessments at FMR in 1994-98 and 2004 (primarily to determine visitor impact, however relative population size can easily be seen from this data; Tenera, 2004), indicating that algal cover has been consistently dense at this location for over fifteen years at least. The transects for the San Mateo County 2004 resource assessment are stated to have been located in the “upper intertidal zone,” at approximately +3-4 ft MLLW (coinciding approximately with our Zone 2-3); zonation for the 1994-98 transects is not specified for some of that data, but can be determined from the resource assessment diagrams of the survey areas to have been in about the same area (Tenera, 2004, Figure 3-1. Sampling locations on Moss Beach Reef).
Neorhodomela larix, black pine rockweed is a perennial that declines in winter and flourishes quickly in spring and summer [Netarts Bay Today, 2013]. Once established, dense populations of Neorhodomela larix are able to spread by vegetative propagation from existing algae into large mats covering rock surfaces that persist for long periods and “easily monopolize the rocky surface in a tidepool” [Klinkenberg, 2013].
Species Diversity. Our survey results for animal populations also can be compared to results from the same San Mateo County resource assessments from previous years (Tenera, 2004), which establish a general baseline for FMR that we have not had for previous surveys this season (despite the different purpose of the earlier studies of accessing visitor impact, the data can still serve for background information here; the findings for animals also pertain roughly to our Zone 2-3). Significant in the following figures for the FMR Moss Beach Reef survey area is the rarity of barnacles in any number, sea stars other than a rare bat star, shore crabs, and sea urchins (and owl limpets, unless they were reported under the Family name Lottidae). Mussels however are present at FMR in large numbers.
Anecdotal opinion from casual observations by visitors to FMR suggests that diversity at this location has fallen dramatically over the years since we first surveyed owl limpets here in 2001. FMR Ranger Joel Cervantes related that in just the first six months he had been assigned to FMR many people told him that the seashore has changed a great deal. These observations were also noted in the San Mateo County resource assessment [Tenera, 2004, 3-57].
Sea Stars. In 2004, the San Mateo County survey (Tenera, 2004) found sea stars (Pisaster ochraceus) relatively common between Moss Beach Reef and Pillar Point, counting 144 Pisaster ochraceus on Frenchman’s Reef and noting that only one Pisaster ochraceus had been counted the year before (Tenera, 2004, 3-57). Our survey found no Pisaster ochraceus at all, and saw only two bat stars (Asterina miniata). This fluctuation likely is complicated further by the presence of star fish wasting syndrome in the Pacific coast population of sea stars.
Urchins. The purple sea urchin Strongylocentrotus purpuratus typically ranges from the intertidal to the subtidal, however that species is not listed among the those present in the FMR intertidal in the studies previously cited for either the periods 1994-98 or 2004. Neither were any purple urchins found in the FMR intertidal by this survey. The absence of urchins may be the result of a catastrophic die off of urchins and several other species, including sea stars and mollusks, that took place on the Sonoma coast, fromsouth of Bodega Bay north to Anchor Bay, in August of 2011 at the same time as a large red tide algae bloom [DFG Marine Management News, 2011]. Perceptible recovery of urchins in this intertidal does not yet appear to have taken place after more than two years.
Mussels. San Mateo County monitored mussel (Mytilus californianus) populations in beds the length of the FMR reserve over a period of ten years from 1994 to 2004 and found no significant change in numbers. Counts were summarized for reporting so they cannot be compared with the counts made by this survey.
Owl Limpets. The baseline offered for the owl limpet (Lottia gigantea) population at FMR is Levine (2004) in which 140 owl limpets were counted, with densities in the Moss Beach Reef area averaging “almost one owl limpet per square meter” [Tenera, 2004]. The San Mateo County study stated that owl limpets “were in highest abundance and were larger in size on Moss Beach Reef,” and this in spite of high visitor use, perhaps because of close surveillance by FMR staff and volunteers.
In her article “LiMPETS: Long-term Monitoring Yields More than Data” [Between the Tides, September 2012], Amy Dean reported that the FMR owl limpet population was steady between 2006 and 2011, but that there was a 30 percent decline in population for 2012.
Our study found one owl limpet in the FMR intertidal. In 2011, when we conducted a prior study of owl limpets at FMR, there was much greater abundance in the same survey area, although exact counts were not made then. Our results now indicate a drastic decline of Lottia gigantea in the Moss Beach Reef intertidal of FMR.
Limpets. In the San Mateo study (Tenera, 2004), Figures 3-22 and 3-15, above, show relative populations of several limpets at FMR. In the 1994-98 period, Lottia scabra were found in the largest numbers, with about half as many L. digitalis; L. asmi, L. limatula, and L. pelta occurred infrequently. In 2004, the mean abundance of L. scabra appears to have fallen off substantially, along with that of L. limatula; L. asmi and L. pelta were still rare. These numbers suggest an overall decline in the population of limpets at FMR. In our survey, we sampled quadrats along the rock surface of Zone 2 in the Moss Beach Reef area and only occasionally found Lottia (Acmaea) digitalis on bare rock surface not covered with Endocladia or Neorhodomela. We did observe limpets more frequently in other areas, on bare rock surfaces free of algae.
Shore crabs. In the San Mateo study (Tenera, 2004), Figures 3-22 and 3-15, above, striped shore crabs Pachygrapsus crassipes were found occasionally in 1994-98, but had negligible presence in 2004. Our survey saw no shore crabs.
Impact of Species Loss. Removal experiments would seem to have established the interrelationships of predator and prey in intertidal communities, and how the presence, decline, or absence of one species can cause the population of another species to fluctuate. Moreover, some research on the of loss of species from an intertidal community proposes that the removal of “more than one species often result in interactive effects, suggesting a high degree of complexity and unpredictability” [Crowe, 2005]. One hypothesis advanced is that the interaction is “idiosyncratic,” which is to say it depends on which species is lost and which species feels the impact. An example of the idiosyncratic view would be an algae that grows when limpets are absent, or when mussels are present and prevent limpets from grazing, and that does not grow when limpets are present and unimpeded.
In the case of FMR, it is possible that as the predators of marine algae, urchins and limpets, have declined from the FMR intertidal community, algae such as Neorhodomela, Endocladia, Mastocarpus, and Petrocelis have had increasing opportunity to grow and thrive.
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