OCS Study 

•

MMS 2001-016 

Rocky Intertidal Resource Dynamics 

at Point Loma, San Diego County, 

California 

1996-1998 Report 

Final Technical Summary 

Final Study Report 

U.S. Department of the Interior 

Minerals Management Service

Pacific OCS Region 
2 
Rocky Intertidal Resource Dynamics 

at Point Loma, San Diego County, 

California 

1996-1998 Report 

Final Technical Summary 

Final Technical Report 

Authors 

John M. Engle 

Principal Investigor 

and 

Daniel L. Martin 

David Hubbard 

David Farrar 

Prepared under MMS Cooperative 

Agreement No. 14-35-0001-30761 

by 

Southern California Educational Intiative 

Marine Science Institute 

University of California 

Santa Barbara, CA 93106 

U.S. Department of the Interior 

Minerals Management Service Camarillo

Pacific OCS Region March 2000
4 

Disclaimer 

This report has been reviewed by the Pacific Outer Continental Shelf Region, Minerals Management 

Service, U.S. Department of the Interior and approved for publication. The opinions, findings, 

conclusions, or recommendations in this report are those of the author, and do not necessarily reflect 

the views and policies of the Minerals Management Service. Mention of trade names or commercial 

products does not constitute an endorsement or recommendation for use. This report has not been 

edited for conformity with Minerals Management Service editorial standards. 

Availability of Report

Extra copies of the report may be obtained from: 

U.S. Dept. of the Interior 

Minerals Management Service 

Pacific OCS Region 

770 Paseo Camarillo 

Camarillo, CA 93010 

phone: 805-389-7621 

A PDF file of this report is available at: 

http://128.111.226.115/CMI/ 

Suggested Citation 

The suggested citation for this report is: 

Engle, J., D.L. Martin, D. Hubbard and D. Farrar. Rocky Intertidal Resource Dynamics at Point 

Loma, San Diego County, California. MMS OCS Study 2001-016. Coastal Research Center, Marine 

Science Institute, University of California, Santa Barbara, California. MMS Cooperative Agreement 

Number 14-35-0001-30758. 78 pages. 
i 

Table of Contents 

FINAL TECHNICAL SUMMARY ....................................................................... 1 

FINAL TECHNICAL REPORT............................................................................ 4 

Introduction ............................................................................................................. 4 

Methods ................................................................................................................. 5 

 Resource monitoring sites ................................................................................... 5 

 Physical Characteristics at the Point Loma Sites........................................... 5 

 Biological Characteristics at the Point Loma Sites ....................................... 7 

 Target species assemblages ................................................................................. 8 

 Survey Procedures ............................................................................................... 8 

Results ................................................................................................................. 10 

 Field Activities and Observations ....................................................................... 10 

 Key Species Survey Data..................................................................................... 11 

 Rockweed (Pelvetia fastigiata) ..................................................................... 11 

 Acorn Barnacle (Chthamalus spp.) ............................................................... 11 

 Pink Thatched Barnacle (Tetraclita rubescens) ............................................ 12 

 Goose Barnacle (Pollicipes polymerus)......................................................... 12 

 Mussel (Mytilus californianus)...................................................................... 12 

 Owl Limpet (Lottia gigantean) ...................................................................... 13 

 Red Algal Turf (Corallina spp., et al.)........................................................... 13 

 Surfgrass (Phyllospadix spp.)........................................................................ 14 

 Other Transect Species .................................................................................. 14 

 Black Abalone (Haliotis cracherodii) and 

 Ochre Seastar (Pisaster ochraceus)......................................................... 15 

Discussion................................................................................................................. 15 

Acknowledgments.................................................................................................... 20 

References ................................................................................................................ 20 
ii

LIST OF FIGURES 

Figure 1. Point Loma Rocky Intertidal Monitoring Sites ....................................... 23 

Figure 2. Species Abundances in Rockweed Plots at 5 Point Loma Sites.............. 24 

Figure 3. Species Abundances in Barnacle Plots at 5 Point Loma Sites ................ 25 

Figure 4. Species Abundances in Goose Barnacle Plots at 5 Point Loma Sites ..... 26 

Figure 5. Species Abundances in Mussel Plots at 5 Point Loma Sites................... 27 

Figure 6. Owl Limpet Length Frequencies at Navy North (F96-S98) ................... 28 

Figure 7. Owl Limpet Length Frequencies at Navy South (F96-S98) ................... 29 

Figure 8. Owl Limpet Length Frequencies at Cabrillo I (F96-S98) ....................... 30 

Figure 9. Owl Limpet Length Frequencies at Cabrillo II (F96-S98) ...................... 31 

Figure 10. Owl Limpet Length Frequencies at Cabrillo III (F96-S98)..................... 32 

Figure 11. Owl Limpet Abundances at 5 Point Loma Sites ..................................... 33 

Figure 12. Owl Limpet Sizes from 6 plots (combined) at 5 Point Loma Sites......... 34 

Figure 13. Species Abundances in Turf Transects at 5 Point Loma Sites ................ 35 

Figure 14. Species Abundances in Surfgrass Transects at 5 Point Loma Sites ........ 36 

Figure 15. Species Abundances in Boa Kelp Transects at 5 Point Loma Sites........ 37 

Figure 16. Scripps Pier Seawater Temperatures (1989 to 1997) .............................. 38 

Figure 17. Scripps Pier Seawater Temperature Anomalies (1920 to 1997) ............. 39 
iii

LIST OF TABLES 

Table 1. Summary of Key Species Monitored at the Five Point Loma Sites.......... 40 

Table 2. Field Activities for the Point Loma, San Diego County 

 Rocky Intertidal Project..................................................................... 41 

Table 3. Personnel Participating in Point Loma Rocky Intertidal Surveys............. 42 

Table 4. Photoplot Cover at Navy North and Navy South in Fall 1996 ................. 43 

Table 5. Photoplot Cover at Cabrillo I, II, and III in Fall 1996............................... 44 

Table 6. Photoplot Cover at Navy North and Navy South in Spring 1997 ............. 45 

Table 7. Photoplot Cover at Cabrillo I, II, and III in Spring 1997 .......................... 46 

Table 8. Photoplot Cover at Navy North and Navy South in Fall 1997 ................. 47 

Table 9. Photoplot Cover at Cabrillo I, II, and III in Fall 1997............................... 48 

Table 10. Photoplot Cover at Navy North and Navy South in Spring 1998 ............. 49 

Table 11. Photoplot Cover at Cabrillo I, II, and III in Spring 1998 .......................... 50 

Table 12. Photoplot Summary Data for Navy North and Navy South...................... 51 

Table 13. Photoplot Summary Data for Cabrillo I, II, and III................................... 52 

Table 14. Photoplot Primary Taxa Data for Navy North and Navy South................ 53 

Table 15. Photoplot Primary Taxa Data for Cabrillo I, II, and III............................. 54 

Table 16. Density and Size of Owl Limpets at Navy North and Navy 

 South in Fall 1996 ............................................................................. 55 

Table 17. Density and Size of Owl Limpets at Cabrillo I, II, and III in Fall 1996.... 56 

Table 18. Density and Size of Owl Limpets at Navy North and 

 Navy South in Spring 1997 ............................................................... 57 

Table 19. Density and Size of Owl Limpets at Cabrillo I, II, and III in 

 Spring 1997 ....................................................................................... 58 

Table 20. Density and Size of Owl Limpets at Navy North and 

 Navy South in Fall 1997.................................................................... 59 

Table 21. Density and Size of Owl Limpets at Cabrillo I, II, and III in Fall 1997.... 60 
iv

LIST OF TABLES (continued) 

Table 22. Density and Size of Owl Limpets at Navy North and 

 Navy South in Spring 1998 ............................................................... 61 

Table 23. Density and Size of Owl Limpets at Cabrillo I, II, and III in 

 Spring 1998 ....................................................................................... 62 

Table 24. Owl Limpet Summary Data for Navy North and Navy South.................. 63 

Table 25. Owl Limpet Summary Data for Cabrillo I, II, and III............................... 64 

Table 26. Owl Limpet Density and Size Data by Plot at Navy North and 

 Navy South........................................................................................ 65 

Table 27. Owl Limpet Density and Size Data by Plot at Cabrillo I, II, and III......... 66 

Table 28. Line Transect Cover at Navy North and Navy South in Fall 1996........... 67 

Table 29. Line Transect Cover at Cabrillo I, II, and III in Fall 1996 ........................ 68 

Table 30. Line Transect Cover at Navy North and Navy South in Spring 1997 ...... 69 

Table 31. Line Transect Cover at Cabrillo I, II, and III in Spring 1997.................... 70 

Table 32. Line Transect Cover at Navy North and Navy South in Fall 1997........... 71 

Table 33. Line Intercept Cover at Cabrillo I, II, and III in Fall 1997........................ 72 

Table 34. Line Intercept Cover at Navy North and Navy South in Spring 1998 ...... 73 

Table 35. Line Intercept Cover at Cabrillo I, II, and III in Spring 1998 ................... 74 

Table 36. Line Transect Summary Data for Navy North and Navy South ............... 75 

Table 37. Line Transect Summary Data for Cabrillo I, II, and III ............................ 76 

Table 38. Transect Primary Taxa Data for Navy North and Navy South ................. 77 

Table 39. Transect Primary Taxa Data for Cabrillo I, II, and III .............................. 78 
Final Technical Summary - Engle 

1 

FINAL TECHNICAL SUMMARY 

STUDY TITLE: Inventory of Rocky Intertidal Resources in San Diego County 

REPORT TITLE: Rocky Intertidal Resource Dynamics at Point Loma, San Diego County, 

California, 1996-1998 Report 

CONTRACT NUMBER: 14-35-0001-30761 

SPONSORING OCS REGION: Pacific

APPLICABLE PLANNING AREA: Southern California

FISCAL YEAR(S) OF PROJECT FUNDING: FY96, FY97, FY98

COMPLETION DATE OF THE REPORT: September 1999 

COST(S): FY 96 - $44,836, FY 98 - $5,000, FY 99 - no cost extension

CUMULATIVE PROJECT COST: $49,836 

PROJECT MANAGER: John M. Engle

AFFILIATION: University of California, Santa Barbara 

ADDRESS: Coastal Research Center, Marine Science Institute, University of California, 

Santa Barbara, CA 93106 

PRINCIPAL INVESTIGATOR: John M. Engle 

KEY PROJECT PERSONNEL: John M. Engle, Daniel L. Martin, David Hubbard, David 

Farrar, Jessica Altstatt, Cynthia Taylor 

COOPERATING AGENCIES: U.S. National Park Service, U.S. Navy 

BACKGROUND: This is the final report of a study monitoring key rocky intertidal 

resources along the coast of Point Loma, San Diego County. The original work period was 

from November 15, 1996 through February 14, 1998; this period was subsequently extended 

to September 30, 1998. 

This project was carried out with cooperative assistance from the U.S. National Park Service 

and the U.S. Navy. Both agencies supported previous monitoring at the Point Loma sites. The 

National Park Service funded surveys at the 3 Cabrillo National Monument sites from 1990 to 

1995. The Navy funded surveys at Navy North and Navy South in 1995. Both agencies will 

continue the monitoring surveys upon conclusion of this project. 

This final project report provides the results of 4 biannual baseline monitoring surveys 

conducted from Fall 1996 through Spring 1998 at 5 rocky intertidal sites along the outer coast 

of Point Loma Peninsula in San Diego, California. The primary project objective was to 

increase regional understanding of population dynamics of important rocky intertidal species 

in order to help assess and reduce human impacts, including possible effects of oil transport 

accidents and public visitation. The work was carried out with cooperative assistance from the 

U.S. National Park Service and the U.S. Navy, who sponsored prior monitoring at the sites 
Rocky Intertidal Resource Dynamics at Point Loma, San Diego County 

2 

and will continue the monitoring upon conclusion of this project. The National Park Service 

funded surveys at 3 contiguous sites along a visitor use gradient at the Cabrillo National 

Monument at the southern end of Point Loma from 1990 to 1995. The Navy funded surveys 

farther north on the Fort Rosecrans Military Reservation at sites designated Navy North and 

Navy South in 1995 to provide baseline information for minimizing impacts from nearby 

Navy facilities. 

DESCRIPTION: The baseline monitoring for this study utilized the same key species 

protocol that has been employed at over 50 sites ranging from San Luis Obispo County to the 

Mexican Border, thus ensuring compatibility with ongoing studies in southern California that 

comprise a recently-formed Multi-Agency Rocky Intertidal Monitoring Network. Abundances 

of 13 index species plus higher taxa were monitored in fixed plots or transects at the 5 sites 

during fall and spring oceanic seasons. In addition, habitat assessments, species 

reconnaissance observations, overview photographs, and videotapes were taken whenever 

possible. 

STUDY RESULTS: The Fall 1996 and Spring 1997 surveys were relatively uneventful; 

however, the next 2 seasonal samples occurred during a major El Niño event that included 

above normal water temperatures, heavy rainfall, and large storm swells. Fall 1997 surveys 

took place shortly after a period of heavy surf. Spring 1998 surveys occurred after a winter 

characterized by record rainfall, major erosion of seacliffs, and numerous storms generating 

large swells. Site-wide storm effects observed during the El Niño period included large 

quantities of kelp wrack and drift debris, overturned rocks, cobble scoured surfaces, and 

breakouts of sedimentary rock strata. 

Despite variability in key species cover dynamics among plots/transects and sites during 1996-

1998, overall patterns of change were fairly consistent at the 5 Point Loma rocky intertidal 

stations. This can be attributed to their proximity along 3.5 km of the peninsula, comparable 

exposure to west-facing sea conditions, and generally similar habitat structure composed of 

gently-sloping wave-cut benches and scattered boulders backed by sedimentary cliffs. Of the 

13 key species monitored at the 3 contiguous Cabrillo National Monument sites from F96 to 

S98, 2 species (black abalone, ochre seastar) were not found and 2 species (sargassum weed, 

aggregating anemone) occurred only in minor amounts. Historically, black abalone and ochre 

seastars were common at Point Loma, but timed searches conducted during each sampling 

since 1990 revealed no black abalone and only 1 ochre seastar. Sargassum weed and 

aggregating anemones were common at the sites, but rare in the sampling because they were 

not primarily targeted in the fixed plots and transects. 

Of the 9 other target species, 5 (pink thatched barnacle, goose barnacle, mussel, red turf, boa 

kelp) remained essentially unchanged, 2 (acorn barnacle, owl limpet) declined slightly, and 2 

(rockweed, surfgrass) declined moderately. Trends mostly were the same for species 

monitored at the 2 Navy sites farther north on Point Loma except that acorn barnacle and 

surfgrass declines here were less, and owl limpet numbers increased substantially. The 

declines in acorn barnacle, rockweed, and surfgrass cover at the Point Loma sites since 1995 

were noteworthy because nearly all occurred after S97, during the strong El Niño event. Other 
Final Technical Summary - Engle 

3 

key species coverages appeared largely unaffected by El Niño, except for storm-induced rock 

breakouts in a few owl limpet, mussel, and goose barnacle plots. 

Trends in key species abundances at the Cabrillo National Monument sites during previous 

monitoring from 1990 to 1995 included major increases in surfgrass, minor declines in goose 

barnacles and owl limpets, and greatly reduced thatched barnacles, mussels, and boa kelp. 

Since 1995, goose barnacles, thatched barnacles, and boa kelp have not recovered to prior 

levels. Mussels have increased to the highest levels ever in Cabrillo I, but have not recovered 

elsewhere. The few remaining mussels throughout Cabrillo II and III areas are older 

individuals, with practically no recruitment. Long-term declines in such species as black 

abalone, ochre seastars, mussels, and boa kelp prior to or since monitoring began in 1990 may 

be related to a 22-year warming trend in southern California waters. 

Since 1995, owl limpet numbers generally have increased to 1990 levels, though variability 

was high due to observer differences in sampling. Acorn barnacle, rockweed, and surfgrass 

cover have now dropped below 1990 values, apparently as a result of “thinning” by the 1997-

1998 El Niño storms. Over past and present surveys, minor seasonal cycles generally were 

evident for 5 key species. Rockweed and surfgrass tended to be less abundant in spring 

periods, while sargassum weed, red algal turf, and goose barnacles (in band transects) tended 

toward lower cover in fall surveys. 

Impacts from human activities at Point Loma may be caused by various types of pollution 

from point and non-point sources, and visitor activities. Contamination from oil was limited to 

scattered tar blobs that were less common than occur at Santa Barbara County monitoring 

sites. Localized impacts from public visitation in Cabrillo I and II were observed during the 

project sampling, but changes in key species abundances associated with visitor use were not 

evident. Some human impacts may be widespread and chronic. Throughout all past and 

current surveys, owl limpets were larger in the protected Cabrillo sites than in the Navy sites 

where collecting may have occurred. The extent of most possible impacts is difficult to 

separate from natural environmental variation without continued long-term monitoring 

coupled with detailed experimental studies. 
Rocky Intertidal Resource Dynamics at Point Loma, San Diego County 

4 

FINAL STUDY REPORT 

INTRODUCTION 

Bedrock intertidal reefs comprise 14% of the coastline of San Diego County, with the 

remaining 86% consisting of sand, gravel, or cobble beaches (Smith et al. 1976). Most rocky 

intertidal shores in the county occur on the Point Loma and La Jolla peninsulas, with 

relatively few isolated reefs farther north. Rocky intertidal communities along the oceanfacing side of Point Loma are the most extensive and diverse in San Diego County. With the 

majority of the peninsula owned by the U.S. Navy, restrictions on public visitation, except at 

the Cabrillo National Monument, have preserved this coast as one of the few remote stretches 

of mainland rocky shoreline in southern California. Visitors at the Cabrillo tidepools are 

fortunate to be able to see fascinating assemblages of plants and animals where the marine life 

is protected from collecting activities. However, the rich communities found in these tidepools 

and rocky reef habitats are subject to influences from a multitude of human activities 

associated with the large metropolitan area of San Diego, including harbor commerce, 

nearshore shipping of oil and other products, wastewater runoff and outfalls, onshore 

development, and direct disturbance or illegal collecting by beach explorers. Effective 

management of increasingly-valued intertidal resources requires dynamic baseline surveys to 

determine what is there and to understand how key components of this land/water interface 

ecosystem respond to natural environmental variations and human impacts. 

Federal, state and local agencies have recognized the importance of baseline 

information for coastal ecological resources by funding the establishment of regional rocky 

intertidal monitoring stations in central and southern California. The goals of shoreline 

resource monitoring include the following: 

• To maintain permanent representative monitoring sites to help assess and reduce 

human impacts and document long-term climatic changes. 

• To increase understanding of population dynamics of important rocky intertidal 

species by comparing key species abundance changes among plots, seasons, years, 

and sites (to the extent possible) throughout central and southern California. 

• To provide relevant information to resource agencies that will lead to more 

effective management of rocky intertidal ecosystems. 

Assessing ecological conditions is a complex and often expensive undertaking. During 

the 1980’s, Channel Islands National Park developed a cost-effective intertidal monitoring 

program that has become a model for rocky shore surveys throughout the Southern California 

Bight (Richards & Davis 1988; Davis & Engle 1991; Ambrose et al. 1995; Engle & Davis 

1996a,b,c; Dunaway et al. 1997; Engle et al. 1997; Engle et al. 1998a,b). Instead of detailed 

surveys of all species at many sites, ecological conditions at representative locations are 

evaluated by concentrating on selected key species assemblages that are monitored seasonally 

in fixed plots. Qualitative reconnaissance surveys yield inventory data and provide ecosystem 

perspective for the key species monitoring. The baseline surveys for this study utilized this 
Final Study Report – Engle 

5 

key species monitoring approach, thus ensuring compatibility with other ongoing studies in 

central and southern California. Following a workshop last year (Engle et al. 1997), a MultiAgency Rocky Intertidal Monitoring Network was established to coordinate related projects at 

over 50 sites ranging from San Luis Obispo County to the Mexican Border (Dunaway et al. 

1997). 

In 1990, the Cabrillo National Monument in San Diego County began long-term rocky 

intertidal monitoring at three sites on the southern tip of Point Loma (Davis & Engle 1991; 

Engle & Davis 1996a,b). In 1995 the U.S. Navy sponsored the establishment of two additional 

sites along central Point Loma (Engle & Davis 1996c). However, funding ceased for 

Monument and Navy surveys by the end of 1995. After a gap in sampling in Spring 1996, the 

current MMS-sponsored project has continued the monitoring from Fall 1996 through Spring 

1998. The Cabrillo National Monument and U.S. Navy will continue the surveys in Fall 1998 

and thereafter. 

METHODS 

Resource monitoring sites 

The locations of the 5 rocky intertidal sites surveyed for this project along the outer 

coast of Point Loma are shown in Figure 1. The 3 sites in the Cabrillo National Monument 

were established in 1990 to assess effects of public use. Public access to the monument’s 

intertidal zone was restricted to a single point approximately 800 m north of the peninsula tip. 

From this point, visitors could explore about 1 km of exposed shoreline without crossing deep 

channels that extend to the base of steep cliffs, or moving around the southern end of the Point 

into San Diego Bay. This situation created a gradient of diminishing public use extending 

from the access location downcoast to the Point. The resource monitoring stations were 

stratified into 3 contiguous areas (Cabrillo I, II, and III) along this human use gradient, with 

each area encompassing roughly 330 m of shoreline. In 1996, Cabrillo III was closed to the 

public to further protect resources and to provide a control site for public use effects. 

The 2 sites north of the Cabrillo National Monument on the Point Loma Peninsula 

were established for the U.S. Navy in 1995 to provide baseline information to aid in 

minimizing impacts from nearby Navy facilities. Conditions evaluated in choosing the 2 

survey sites included reasonable and safe access, regional representation of stable (bedrock or 

large boulder) habitats, sufficient abundances of the same key species monitored at the 

Cabrillo National Monument, and adequate bedrock surfaces for establishing fixed plots. The 

physical and biological characteristics of the Navy and Monument sites are summarized 

below. More detailed information is available in Engle and Davis (1996a,b,c). 

Physical Characteristics at the Point Loma Sites

The Navy North (NN) site encompasses approximately 300 m of rocky shore along the 

base of sheer 25-30 m high sedimentary cliffs in the central portion of the Fort Rosecrans 

Military Reservation on Point Loma (32.693 N Lat, 117.253 W Lon). A prominent landmark 
Rocky Intertidal Resource Dynamics at Point Loma, San Diego County 

6 

for this site is the centrally-located pinnacle rock (10 m high; 30 m in diameter). This chimney 

rock is about 20 m offshore from the main promontory such that it is surrounded by water at 

high tide. The NN site extends from roughly 200 m upcoast of the chimney rock to 100 m 

downcoast. The rocky intertidal zone at this site consists primarily of broad, gently-sloping 

wave-cut benches composed of many horizontal layers of poorly-consolidated sandstone. 

There are numerous crevices, channels, and pools on the mostly low-medium relief features. 

There is little sand on this headland shore. The gradual beach slope at NN creates extensive 

intertidal reef area, extending 30-100 m offshore. The site is fully exposed to ocean swells, but 

the outer reef margin dissipates some of the wave energy, especially at low tide. Access to this 

site requires hiking about 1 km upcoast from the shore trail at Navy South. 

The Navy South (NS) site encompasses approximately 250 m of rocky shore along the 

base of 25 m high cliffs at the southern end of the Fort Rosecrans Military Reservation 

(32.683 N Lat, 117.250 W Lon), 0.25 km north of the northern boundary of the Point Loma 

Wastewater Treatment Facility. A prominent landmark for this site is the narrow promontory 

separating the broad cove to the south from the narrow access inlet to the north. The NS site 

extends from about 100 m upcoast of the promontory tip to about 150 m downcoast. Like NN, 

NS intertidal shore consists primarily of wave-cut benches composed of many horizontal 

layers of poorly-consolidated sandstone. However, NS has a more irregular shoreline, 

resulting in greater diversity of physical habitats, and narrower intertidal reefs (5-20 m wide, 

except for the southern cove where rockweed plots are located), resulting in greater wave 

shock for benches not protected by headlands. 

The 3 Cabrillo National Monument monitoring sites have generally similar features, 

with poorly-consolidated, sedimentary reefs projecting out from eroding sandstone cliffs. The 

relatively flat, gently-sloping reefs are topped with scattered rocks and boulders. Reef width 

varies from 20-40 m in Cabrillo I to >50 m in Cabrillo II to >70 m in Cabrillo III, resulting in 

a moderate gradient in wave exposure conditions from highest wave shock in Cabrillo I to 

calmest conditions in Cabrillo III. Cabrillo I (32.669 N Lat, 117.245 W Lon) extends from 

~220 m north to ~110 m south of the access point. The northern portion is backed by fractured 

low cliffs with small caves and pockets of cobble and boulders. The offshore region is 

composed of pools, surge channels, and numerous boulders. The southern part of the site is in 

a cove backed by higher cliffs and a small sand beach. Cabrillo II (32.668 N Lat, 117.245 W 

Lon) extends downcoast approximately 330 m from the boundary of Cabrillo I, with the 

central portion located offshore from the old Navy dolphin training compound. The northern 

section of Cabrillo II has sloping rock slabs and low-relief reefs, mixed with various-sized 

boulder/bedrock outcrops. The central and southern parts of the site are backed by an irregular 

low sandstone cliff with caves and pockets of boulders and cobbles. The lower intertidal zone 

encompasses extensive pools and flat reefs topped with occasional boulders. Cabrillo III 

(32.665 N Lat, 117.243 W Lon) extends another 330 m from Cabrillo II (at the Radio Tower) 

south to the tip of Point Loma, including a prominent line of boulders that extend offshore 

southwest of the lighthouse. The site is backed by large riprap boulders and a low cliff. Except 

for the south end boulders, the offshore portion of Cabrillo III has extensive, broad, flat reefs 

with shallow pools and small rocks. 
Final Study Report – Engle 

7 

Biological Characteristics at the Point Loma Sites

Overall, the biological communities at the Navy and Cabrillo sites are quite 

comparable. All sites contain extensive reefs, with a range of wave exposures and a variety of 

microhabitats, that support diverse plant and animal species. The same key species 

assemblages are found at the 5 sites. Upper intertidal zones typically occur as relatively 

narrow bands on steeply-sloping walls at cliff bases or on projecting rocks or uplifted benches 

farther out on the shore. Slippery algal films and hard crusts predominate, along with sessile 

invertebrates (especially barnacles) and numerous motile grazers (i.e., periwinkles, limpets, 

chitons) that nestle in damp pits and crevices. Opportunistic algae are locally abundant where 

fresh-water seeps occur and where layers of rock break out, creating fresh bare surfaces. The 

Navy sites have greater numbers of periwinkles and chitons compared to the Cabrillo sites, 

probably because higher wave exposures at NN and NS provide more moisture to the upper 

intertidal zone. White acorn barnacles are present but not dense at Navy and Cabrillo 

locations. The larger, longer-lived pink thatched barnacles are more common at the Cabrillo 

sites, where high densities can occur on harder rocks that are less subject to erosion. Owl 

limpets are common at all the Point Loma sites, with highest densities in the most exposed 

subareas, but the Monument limpets tend to be larger than those at the Navy sites. 

Other ecologically important species occurring slightly lower in the high intertidal 

zone at Point Loma include rockweed, California mussels, and goose barnacles. Overall 

rockweed is not common at the Navy and Cabrillo sites; it is present in patches on the sides of 

harder projecting rocks, or in partially protected habitats, such as the downcoast lees of 

headlands. Mussels now are rare throughout the peninsula, including at the Navy and Cabrillo 

sites where the few present were targeted for fixed plot monitoring. Only scattered small 

patches occur in narrow bands along cliff bases or on the sides of higher rock outcrops in 

areas with direct wave exposure. Goose barnacles also are less common than expected at Point 

Loma. Overall, they are rare at the Navy sites where they mingle with the few mussels. They 

are present in slightly greater numbers at the Cabrillo locations. Here they were not only found 

with mussels, but also as a spotty narrow band higher up along the cliff base or on riprap. 

The middle intertidal zones at Point Loma are relatively flat benches covered by lowgrowing red algal turf. Previous work (Stewart 1982) has shown that a few low-growing 

plants, primarily the coralline algae Corallina vancouveriensis and C. pinnatifolia, dominate, 

but many other algae (>67 species) occur as epiphytes on the anchor taxa, and numerous small 

invertebrates (>45 species) inhabit the carpet-like thicket. Red turf assemblages are abundant 

at all Navy and Cabrillo areas, but are more extensive in Cabrillo II and III where the broadest 

mid-tidal reef flats occur. Two key species, aggregating anemones and sargassum weed occur 

in low depressions within the algal turf zone and in tidepools and surge channels at Point 

Loma. Anemones are more common at the Cabrillo sites where the larger flats drain more 

slowly. In addition to the larger solitary anemones inhabiting wet microhabitats, smaller 

clonal forms are present just above the turf zone, usually on the inshore sides of outcrops near 

sand pockets. These shelly-sand covered aggregations also are more common at Cabrillo, 

where sand influence is slightly higher. The non-native sargassum weed is present at all Point 

Loma sites. Some dense patches occur in sheltered pools and on wet surfaces where breakout 

of rock slabs or overturned rocks expose bare substrate. 
Rocky Intertidal Resource Dynamics at Point Loma, San Diego County 

8 

Extensive meadows of surfgrass drape much of the low intertidal zones at the Navy 

and Cabrillo sites. Surfgrass is particularly dense on the flat offshore benches at the Navy 

sites, where waves splash over the grass habitat even at low tide. At the Cabrillo sites, the 

grass beds are generally less dense, more broken up by cobble and boulders overlying the 

outer reefs, and contain greater amounts of sand than those at NN and NS. The inshoremost 

grass patches at all areas are confined to tidepools, where the plants are shorter and often 

partially bleached. Boa kelp previously was common at the reef fringes at Point Loma, but is 

mostly subtidal now. Intertidal boa kelp is rare at the Navy sites, where only the occasional 

weathered adult or fresh juvenile can be seen. It is found more often at the Cabrillo sites, but 

far below the abundances recorded in the early 1990’s. 

Target species assemblages 

Ideally one would like to monitor the abundances of all species in an area; however, 

limited resources require that a subset of the resident species be targeted. Intertidal zonation is 

frequently characterized by distributions of dominant attached plants and sessile animals 

(Ricketts et al. 1985). Therefore, a representative group of important taxa (species or species 

groups), also referred to as “target” or “key” species assemblages, can provide an accurate 

index of ecological conditions (see Ambrose et al. 1995 for discussion). Thirteen index taxa 

have been monitored at the 3 Cabrillo National Monument sites since 1990 (Davis & Engle 

1991; Engle & Davis 1996a,b) and at the 2 Navy sites since 1995 (Engle & Davis 1996c). 

Criteria used for selecting these target species assemblages include the following: 

• Species ecologically important in structuring intertidal communities 

• Species characteristic of discrete intertidal heights 

• Species that have been well-studied 

• Species that are especially vulnerable to human impacts 

• Species practical for long-term monitoring 

The index taxa surveyed at the NN, NS, and Cabrillo intertidal sites are listed in Table 

1. In addition to the key species, broad categories (other plants, other animals, other biota) 

were scored, as well as the amount of tar and bare substrate (rock or sand). The natural history 

and ecology for each of the key species are summarized in Engle and Davis (1996b). 

Survey procedures 

The sampling techniques used to survey NN, NS, and the 3 Cabrillo sites were similar 

to those employed elsewhere in the Multiagency Rocky Intertidal Monitoring Network to 

ensure optimum compatibility among studies (Richards & Davis 1988; Ambrose et al. 1995; 

Engle et al. 1994a,b; Dunaway et al. 1997; Engle et al. 1997). These include qualitative 

species inventories combined with quantitative cover (for sessile species) or count (for mobile 

species) data for the index taxa within fixed plots or along fixed transects. Fixed sampling 

units reduce the variability that would result from random sampling, and thus give more 

statistical power to detect changes in cover or density over time (see Ambrose et al. 1995 for 

discussion of advantages and limitations of fixed plot sampling). Each site was sampled in 
Final Study Report – Engle 

9 

Spring and Fall, to evaluate seasonal population changes during the periods when maximum 

differences were expected. 

Table 1 summarizes the sampling techniques and number of replicate fixed plots for 

each key species at the 5 monitoring sites. Rectangular (50 x 75 cm; 0.375 m2) photoquadrats 

were used to monitor the population dynamics of 5 relatively small, densely-spaced target 

species, rockweed (Pelvetia fastigiata), acorn barnacles (Chthamalus spp.), pink-thatched 

barnacles (Tetraclita rubescens), mussels (Mytilus californianus), and goose barnacles 

(Pollicipes polymerus). Bolts or epoxy mark 3-4 corners of each plot. The upper left bolts or 

epoxy were marked for plot identification. Still photos were taken during each seasonal survey 

using a quadripod apparatus, which holds a camera and strobe in a fixed orientation over each 

quadrat. Five replicate photoquadrats were surveyed for each target species (except for goose 

barnacles; these have 6 replicates because the Cabrillo sites had 3 band transects that were 

converted to photoplots in 1995, with 2 plots per transect). Species abundance was scored 

from the slides in the laboratory as percentage cover by the point contact method. The slide 

was projected onto a grid of 100 uniformly-distributed points. The number of points occupied 

by key species, higher taxa, tar, and bare substrate were recorded to determine percentage 

cover of each taxon. 

The number and size distribution of owl limpets (Lottia gigantea) were monitored 

within permanent circular plots at all 5 intertidal sites. There were 6 replicate plots because 

each Cabrillo site was established with 3 plots on boulder and 3 on cliff face habitats). Plots 

were marked with a center bolt, marked to indicate the plot number. All limpets ≥15 mm 

found within a 1 m radius circle (3.14 m2 area) around each bolt were counted and measured 

(maximum length in millimeters). 

Red algal turf (Corallina spp. and other tufted algae), surfgrass (Phyllospadix spp.),

boa kelp (Egregia menziezii), sargassum weed (Sargassum muticum), and aggregating 

anemones (Anthopleura elegantissima) were sampled by line-intercepts along 10 m long 

permanent transects. Six replicate transects were used at each site. Two transects each were 

employed for red algal turf and surfgrass. At Cabrillo, 2 additional transects originally 

targeted boa kelp, but by 1995 this lowest zone became dominated by surfgrass. At NN and 

NS, with boa kelp rare in 1995, the 2 “boa kelp zone” transects were placed in the lowest 

surfgrass level. Each transect was marked at both ends and the center with stainless steel bolts. 

Bolts at the start (north end) of each transect were notched for identification. The abundance 

and distribution of the key species, other biota, tar, and bare substrate were recorded as 

distances (to the nearest centimeter) along the edge of a meter tape laid out between the bolts. 

Historically, ochre sea stars (Pisaster ochraceus) and black abalone (Haliotis 

cracherodii) were important components of Point Loma intertidal shores (Zedler 1976, 1978). 

However, these key species have been rare or absent here in recent years. Timed searches (30 

person minutes) of likely habitats throughout each survey site were conducted during each 

sampling period in order to document possible occurrences of any species of abalone or sea 

stars. 
Rocky Intertidal Resource Dynamics at Point Loma, San Diego County 

10

Reconnaissance observations were made during the surveys whenever possible after 

key species monitoring was completed. Physical conditions were characterized at each site, 

including weather conditions, sea state, substrate changes, presence of tar, and other unusual 

occurrences such as debris or pollutants. Biological features were noted, including habitat 

types and zonation, distribution and abundance of species, condition of individuals and 

populations (e.g., size-structure, color pattern, epiphyte load), and animal behavior. The 

presence and activities of birds, marine mammals, and humans were recorded. Representative 

habitats and microhabitats (e.g., crevices, tidepools, under-rock, under-plant) were explored 

and species composition noted. Overview photos and/or videos were taken as necessary to 

document site-wide physical and biological conditions. Navy personnel C. Berdzar and E. 

Steenblock used a Trimble Global Positioning System (GPS) during Spring 1998 to acquire 

latitude and longitude coordinate values for plots, transects, and reference bolts. 

RESULTS 

Field Activities and Observations 

Table 2 lists the schedule of field activities for the rocky intertidal baseline surveys at 

the 5 Point Loma sites. For efficiency, we concentrated the work during periods in when good 

low tides occurred during midday hours. Project biologists, cooperating scientists from the 

National Park Service and California Department of Fish and Game, U.S. Navy personnel, 

and numerous volunteers participated in the field surveys (Table 3). Results from Spring and 

Fall reconnaissance and key species surveys at the 2 Navy and 3 Cabrillo National Monument 

sites are reported below. For ease of presentation, the sampling seasons are abbreviated, for 

example, as F97 for Fall 1997 and S98 for Spring 1998. The Navy sites are abbreviated as NN 

(Navy North) and NS (Navy South). The Cabrillo National Monument sites from north to 

south are abbreviated as Cabrillo I, Cabrillo II, and Cabrillo III. 

During each visit to the Point Loma sites, qualitative physical and biological 

observations were recorded on Field Log data sheets, videotape, and/or photographs. The F96 

and S97 surveys were relatively uneventful in terms of observed conditions at the 5 sites. 

There was evidence of typical storm activity, including some bent or missing bolt markers, a 

few breakouts of sedimentary rock, occasional overturned rocks, and several smashed lobster 

traps high on the beach. 

The F97 and S98 samples occurred during a major El Niño event that included above 

normal water temperatures, heavy rainfall, and large storm swells. F97 surveys took place 

shortly after a period of heavy surf. Large amounts of kelp wrack and drift debris were 

observed at all Point Loma sites, with some piles 1.5 m high. The wrack included giant kelp, 

sea palms, various algae, and surfgrass. A moderate number of overturned rocks were seen 

and some scour marks noted on outer reef margins in the surfgrass zone. S98 surveys occurred 

after a winter characterized by record rainfall, major erosion of seacliffs, and numerous storms 

generating large swells. S98 conditions at the Point Loma sites after winter storms included 

additional damaged markers in mussel and goose barnacle plots and surfgrass transects, a 

greater number of overturned rocks and cobble scoured surfaces, and various breakouts on the 
Final Study Report – Engle 

11

sedimentary cliff faces. Some landslides were evident. There was less drift debris and kelp 

wrack than in F97. Sand levels were low on nearby beaches. Freshwater seeps from bluffs 

were prevalent, with blooms of ephemeral algae evident in the vicinity of the seeps. 

Visitors were most common at Cabrillo I and II during the monitoring surveys. 

Cabrillo III has been closed to the public since 1996. No people were seen at NN or NS during 

F96-S98 sampling, not surprising due to the difficult access and military restrictions. At 

Cabrillo I and II, visitor activities involved walking over the reef, turning over rocks, and 

picking up shells or animals. Collecting was prohibited. A few spots of weathered tar were 

seen at the San Diego sites, but no major concentrations or fresh material. 

Key Species Survey Data 

The results of monitoring rocky intertidal species assemblages in fixed plots/transects 

at the 5 Point Loma, San Diego County sites from Fall 1996 through Spring 1998 are 

presented below for each key species. Summary data from prior monitoring (starting Spring 

1995 for the Navy sites and Spring 1990 for the Cabrillo sites) are provided for longer-term 

perspective. The earlier data were reported in Engle and Davis (1996b,c). This section will 

focus on mean abundances for replicate plots or transects at each site. Changes in percentage 

cover are presented as differences between sampling seasons, not as percent of change from 

previous values. 

Rockweed (Pelvetia fastigiata) 

Plots emphasizing rockweed were monitored at each of the 5 Point Loma sites (Tables 

4-15; Fig. 2). Rockweed cover declined substantially from F96 to S98 at all sites, with most of 

the losses occurring after S97. Declines ranged from 11% at NS to 38% at NN, with Cabrillo 

sites intermediate (23%, 33%, 34%). Other plant cover typically increased where Pelvetia

declined. Rockweed declines at the 5 sites generally were consistent among plots, except a 

few plots, especially at NS, changed little from F96 to S98. Rockweed did not occur in other 

key species plots at Point Loma, except for mostly minor amounts in a few barnacle plots. Of 

the 2 barnacle zone plots with F96 rockweed cover >10%, plot 3 in Cabrillo II was unchanged 

by S98, while plot 3 in Cabrillo III declined 10%. 

Since establishment of the Navy sites in S95, Pelvetia has declined by 50% cover at 

NN, but only decreased 7% at NS. Initial survey cover values for rockweed at the Cabrillo 

sites in S90 were less than or similar to the values in F96, thus most of the declines were 

recent. S98 abundances at Cabrillo I, II, and III were the lowest in the 8 y of monitoring. Over 

the years, there was a tendency for rockweed cover to be less in Spring than in Fall, but this 

pattern was not always evident. 

Acorn Barnacle (Chthamalus spp.) 

None of the Point Loma sites had plots specifically targeting acorn barnacles; 

however, these barnacles occurred in varying abundances within thatched barnacle plots, and 

in some goose barnacle, mussel, and rockweed plots (Tables 4-15; Figs. 2-3). Chthamalus
Rocky Intertidal Resource Dynamics at Point Loma, San Diego County 

12

cover varied considerably between samplings, but there was a trend of declining abundance 

from F96 to S98, with most losses occurring after S97. NN and NS thatched barnacle plots 

had low cover of acorn barnacles initially in F96, which declined slightly by S98. The 3 

Cabrillo sites had 10-22% cover of Chthamalus in F96, which decreased by 10-18% cover, 

thus few acorn barnacles remained by S98. At Cabrillo III, Chthamalus in mussel plots 

plummeted from 48% cover in F96 to 9% in S98, but those in goose barnacle plots remained 

essentially unchanged. Other plants and/or bare rock increased wherever barnacles decreased. 

The cover of acorn barnacles in thatched barnacle plots at the Cabrillo sites during the 6 y of 

sampling prior to F96 often was unstable, with no obvious seasonal or annual pattern, 

although some changes were comparable between areas (e.g., declines between S92 and F92). 

Pink Thatched Barnacle (Tetraclita rubescens) 

Plots targeting the relatively large thatched barnacles were surveyed at all the Point 

Loma sites (Tables 4-15; Fig. 3). A few Tetraclita occurred on rock or atop mussels in several 

mussel and goose barnacle plots. Even in the targeted barnacle plots, Tetraclita abundance 

typically was <10% during F96-S98, except at NN where cover ranged from 21-32%. Bare 

rock, other plants, and acorn barnacles dominated most of these plots. Thatched barnacle 

cover remained fairly stable at all sites during the past 2 y of sampling, although a few plots 

varied considerably between surveys. Since S95, Tetraclita cover has remained fairly stable at 

NN, and declined from 15% to 7% cover at NS. Greater losses were evident at the Cabrillo 

sites since S90 (-16%, -23%, -12%). Cover values prior to F91 were the highest recorded 

during the 8 y of monitoring at all 3 sites. There has been a tendency toward higher cover in 

Spring than in Fall. 

Goose Barnacle (Pollicipes polymerus) 

Goose barnacles were monitored at all 5 sites in their targeted plots and in mussel 

plots (Tables 4-15; Figs. 4-5). Six replicate plots were surveyed instead of 5 in order to 

maintain consistency after 3 band transects were converted into 2 photoplots each at the 

Cabrillo National Monument in S95. Pollicipes cover has typically been <15% at the Point 

Loma sites, with bare rock, other plants, and mussels comprising most of the plot cover. From 

F96-S98, goose barnacle cover remained essentially unchanged among the sites, with the 

greatest differences reflecting a 7% loss within the mussel zone plots at NS and a 6% gain 

within the goose barnacle zone plots at Cabrillo I. Pollicipes did not occur in the mussel zone 

plots at Cabrillo II or III. Goose barnacle cover at NS, Cabrillo II, and Cabrillo III have been 

stable since S95, but NN cover declined 5% in goose barnacle zone plots and 7% in mussel 

zone plots, and Cabrillo I cover increased 8%. The only plots with sufficient Pollicipes cover 

for analysis since S90 were in the mussel zone in Cabrillo I. Individual plots there varied; 

however, collectively they exhibited remarkable stability over the 8 y period. 

Mussel (Mytilus californianus) 

Mussel assemblages were surveyed at all Point Loma sites in mussel zone plots and in 

some goose barnacle plots, notably at NS (Tables 4-15; Figs. 4-5). From F96 to S98, Mytilus

cover increased by 12% at NN and Cabrillo I, but showed relatively little change elsewhere 
Final Study Report – Engle 

13

(±0-5%). Individual plots changed in a highly variable manner, with some increasing and 

others decreasing even at the same site. The NN and NS patterns were similar back to S95 as 

well, but cover at the Cabrillo sites changed markedly since S90. Mussels at Cabrillo I varied 

from 6-16% cover during S90-F95, then increased to a high of 34% cover in S98. Cabrillo II 

and III Mytilus cover declined from highs of 55% and 47% to <5% levels from S90 to S94, 

after which they exhibited near zero cover. Mussels in these plots were replaced by other 

plants, bare rock, and acorn barnacles. 

Owl Limpet (Lottia gigantea) 

Owl limpets ≥15 mm length were counted and measured in 6 plots each at the Point 

Loma sites (Tables 16-27; Figs. 6-12). Total numbers of limpets increased slightly (by 4-14) at 

NS, Cabrillo I, and Cabrillo III, increased more at NN (by 72), and decreased at Cabrillo II (by 

55), between F96 and S98. All plots contributed to the increases at NN, but interplot dynamics 

were mixed at the other sites. Most of the decline at Cabrillo II was due to losses in 2 plots 

where the counts were highly variable. Small limpets (<30 mm) contributed more to the gains 

at NN and losses at Cabrillo II than larger limpets. Overall, mean sizes decreased by 1-2 mm 

at 2 sites (NN and Cabrillo III) and increased by 2-5 mm at 3 sites (NS, Cabrillo I, and 

Cabrillo II). Mean sizes during the F96-S98 period were larger at the Cabrillo sites (39-49 

mm) than at the Navy sites (31-38 mm). All sites had limpets as small as 15 mm, with the 

largest limpets found at Cabrillo I (75-84 mm), followed by Cabrillo II (77-79 mm), Cabrillo 

III (66-70 mm), NS (64-69 mm), and NN (58-69 mm). 

Since S95, the total number of Lottia at NN increased by 72 and those at NS by 94. 

Most of the change came from higher numbers of small limpets (<30 mm) at NN, but both 

large and small limpets became more common at NS. Since S90, owl limpets at Cabrillo I 

increased by 64, while those at Cabrillo II and III declined by 19 and 39. The gains in Cabrillo 

I were primarily due to additional small limpets, while the losses in Cabrillo II and III were 

due to losses of larger individuals. Neither numbers nor sizes of Lottia appeared to show 

seasonal patterns. 

Red Algal Turf (Corallina spp., et al.) 

Red turf is a mixed species assemblage of low-growing algae that carpet the middle 

intertidal zones of low-relief reefs. In San Diego County, this turf can contain as many as 67 

types of plants, but often 2 species of erect coralline algae (Corallina vancouveriensis and C. 

pinnatifolia) dominate (Stewart & Myers 1980; Stewart 1982; Stewart 1989b). Turf cover was 

measured in line-intercept transects at all Point Loma sites (Tables 28-39; Figs. 13-15). It also 

was common in the surfgrass and boa kelp transects at the Cabrillo sites, but was overlain 

with grass to such an extent at NN and NS that it received low primary cover scores there. 

During F96-S98, red turf covered 90-100% of the turf zone transects at NN and NS and 66-

90% of the transects at Cabrillo I, II, and III. The turf assemblage was remarkably stable at all 

Point Loma sites, not only during the past 2 y, but also back to S95 for the Navy sites and 

back to S90 for the Cabrillo sites. Inter-transect dynamics were generally minimal and 

consistent as well at the sites, except at Cabrillo III where 1 transect gained 18% in turf cover 

and the other transect lost 13% cover during the F96-S98 period. 
Rocky Intertidal Resource Dynamics at Point Loma, San Diego County 

14

Red turf cover in the surfgrass zone increased at all sites where surfgrass declined 

during F96-S98, except in Cabrillo III where turf remained stable. The reduction in surfgrass 

allowed the already existing understory turf to be exposed as the primary cover. Red turf cover 

increases were 15% and 4% for NN and NS offshore surfgrass transects, and 22% and 8% for 

Cabrillo I and II surfgrass transects. Similar increases in turf cover occurred where surfgrass 

declined in the boa kelp zone at Cabrillo I and II (11% and 20% gains). Since S90, red turf 

cover in the surfgrass and boa kelp transects generally varied inversely with the surfgrass and 

boa kelp cover due to the fact that only the top biotic layer was scored. 

Surfgrass (Phyllospadix spp.) 

Surfgrass was targeted at all 5 sites, with 2 line-intercept transects each at the Cabrillo 

sites, and 2 inshore and 2 offshore transects each at NN and NS (Tables 28-39; Figs. 13-15). It 

also occurred in variable amounts in the turf transects everywhere, and was prominent in the 

boa kelp transects at Cabrillo I, II, and III. Phyllospadix covered 79-100% of the surfgrass 

zone transects at NN and NS, and 39-90% of those transects at the Cabrillo sites during the 

past 2 y. Surfgrass cover remained stable from F96 to F97, then declined markedly at all sites 

by S98. These decreases ranged from minor losses (3-4%) at NN and NS inshore transects to 

moderate decreases (13-17%) at NN and NS offshore transects as well as those at Cabrillo I, 

to major declines (37-50%) at Cabrillo II and III. Grass declines were matched by increases in 

bare rock and/or red turf. Trends were fairly consistent among all transects. At NN and NS, 

inshore Phyllospadix cover remained essentially unchanged since S95, while offshore grass 

cover declined by 10-11%, mostly since F97. Surfgrass cover in S98 was 5% higher than the 

S90 condition at Cabrillo I, but Cabrillo II and III sites were 18% and 12% lower. Overall, 

there was a pattern, especially evident at Cabrillo III, of lower surfgrass cover in Spring 

compared to Fall. 

Surfgrass in red turf and boa kelp zones at the Cabrillo sites followed similar trends as 

that in the targeted surfgrass zone. Grass losses between F96 and S98 in red turf transects 

were minor (3% at Cabrillo I, 10% at Cabrillo II, 0% at Cabrillo III). Phyllospadix declines in 

boa kelp transects were considerable (16% at Cabrillo I, 22% at Cabrillo II, 32% at Cabrillo 

III). In S90, when boa kelp was common in the boa kelp zone, surfgrass cover there ranged 

only from 4-11%. In later years, grass cover increased as boa kelp declined, with peak 

Phyllospadix abundance ranging from 41-81% cover in F96. 

Other Transect Species 

Boa Kelp (Egregia menziezii), initially common in low intertidal transects at the 

Cabrillo National Monument, did not occur in any transects at NN, or NS (Tables 28-39; Fig. 

15). Major declines occurred at all 3 Cabrillo sites prior to F96, after which boa kelp was 

minimally present or absent from the transects. Surfgrass was the principal replacement cover 

on the Egregia transects, except at Cabrillo III in S98 when bare rock accounted for 43% of 

the coverage. 

Sargassum weed (Sargassum muticum) was absent in NN and NS transects. At the 

Cabrillo National Monument since S90, it occurred occasionally in the turf transects (1-3%), 
Final Study Report – Engle 

15

grass transects (1-26%), and kelp transects (1-18%) (Tables 28-39; Fig. 14). Clearly this 

weedy species was quite variable in its occurrence; however, whenever found, Sargassum was 

consistently more common in Spring compared to Fall seasons. 

Aggregating anemones (Anthopleura elegantissima) were absent in transects at the 

Navy sites; they occurred in small amounts in the Cabrillo transects, primarily in the turf zone 

(Tables 28-39). Anemone cover ranged from 0-2% throughout the 8 y of monitoring at 

Cabrillo I, II, and III. Though low, anemone cover appeared stable, with no seasonal or annual 

trends. 

Black Abalone (Haliotis cracherodii) and Ochre Seastar (Pisaster ochraceus) 

Black abalone and ochre seastars once were common in San Diego County, but now 

are absent or rare, to the extent that it was not possible to survey for them in fixed plots. 

Instead, haphazard timed searches at each site were carried out to document their 

absence/rarity or possible recovery. No black abalone or ochre seastars were found at any site 

in the 8 y of surveys since S90, except for 1 ochre seastar observed at Cabrillo I in S94. 

Occasional individuals of the typically subtidal green abalone (Haliotis fulgens), blue knobby 

stars (Pisaster giganteus), and bat stars (Asterina miniata) were noted at the Cabrillo and 

Navy sites. 

DISCUSSION 

This section synthesizes information acquired during the Point Loma, San Diego rocky 

intertidal monitoring surveys with respect to the temporal variability of index species 

populations. The natural history and ecology of the index species are summarized in Engle 

and Davis (1996b). It is important to note that determination of the causes for any abundance 

changes is a difficult process. Much can be inferred from the data and observations during the 

monitoring, combined with knowledge gained from previous intertidal ecology and impact 

studies; nevertheless, carefully designed experiments would be necessary to attribute specific 

causality with confidence. At Navy North and Navy South, monitoring now includes 3 

samples for each season from S95 to S98 (no S96 sample). Navy data for 1995 are discussed 

in Engle and Davis (1996c). Navy North and South results for 1997-1998 are compared with 2 

recently added monitoring sites in San Diego County (Cardiff Reef and Scripps Reef) in Engle 

et al. (1998b). At Cabrillo I, II, and III, monitoring now includes 8 samples for each season 

from S90 to S98 (no S96 sample). Cabrillo data from 1990 through 1995, including possible 

effects of human activities, are discussed in Engle and Davis (1996b). 

Despite variability in key species cover dynamics among plots/transects and sites (not 

unexpected in complex intertidal systems) during F96-S98, overall patterns of change were 

fairly consistent at the 5 Point Loma stations. This can be attributed to their proximity along 

3.5 km of the peninsula, comparable exposure to west-facing sea conditions, and generally 

similar habitat structure composed of gently-sloping wave-cut benches and scattered boulders 

backed by sedimentary cliffs. Of the 13 key species monitored at the 3 contiguous Cabrillo 

National Monument rocky intertidal sites from F96 to S98, 2 species (black abalone, ochre 
Rocky Intertidal Resource Dynamics at Point Loma, San Diego County 

16

seastar) were not found and 2 species (sargassum weed, aggregating anemone) occurred only 

in minor amounts. Of the 9 other target species, 5 (pink thatched barnacle, goose barnacle, 

mussel, red turf, boa kelp) remained essentially unchanged, 2 (acorn barnacle, owl limpet) 

declined slightly, and 2 (rockweed, surfgrass) declined moderately. Trends mostly were the 

same for species monitored at the 2 Navy sites farther north on Point Loma except that acorn 

barnacle and surfgrass declines here were less, and owl limpet numbers increased 

substantially. 

Historically black abalone and ochre sea stars were present at Point Loma (Zedler 

1976, 1978). No black abalone and only 1 ochre seastar have been found during the biannual 

timed searches at the Cabrillo sites (since 1990) and none were found at the Navy sites (since 

1995). Abalone losses prior to initiation of Cabrillo monitoring may have been associated 

with a “withering” syndrome that has caused widespread declines at the Channel Islands 

(Lafferty & Kuris 1993; Richards & Davis 1993) and along other mainland shores in southern 

California (Miller & Lawrenze-Miller 1993; Altstatt et al. 1996). Similarly, sea star 

populations in this region have been decimated by a “wasting” disease, apparently caused by a 

warm-water bacterium of the genus Vibrio (Schroeter & Dixon pers. comm.). 

Sargassum weed and aggregating anemones occurred at the monitoring stations, but 

were not primarily targeted in fixed plots or transects, hence their recorded absence at the 

Navy sites and low abundances at the Cabrillo sites. With scant data, little can be revealed 

about population trends. However, limited records and observations since 1990 at the Cabrillo 

sites indicated that sargassum weed cover was variable, yet consistently more common in 

spring compared to fall seasons. This is because sargassum weed undergoes post-reproductive 

declines each summer (Gunnill 1980a,b, 1983; Deysher & Norton 1982). On the other hand, 

aggregating anemone cover, though low in the transects, appeared stable throughout the 8 y of 

surveys at the Cabrillo sites. 

Pink thatched barnacle, goose barnacle, mussel, red turf, and boa kelp abundances at 

the Point Loma sites changed relatively little overall from S96-F98, though moderate variation 

occurred among plots and sites. Pink thatched barnacles exhibited substantial losses at the 3 

Cabrillo sites from 1990-1995, with no recovery evident by 1998. Goose barnacle cover in the 

photoplots was remarkably stable, (not only over the past 2 y, but also over 8 y at Cabrillo I), 

despite observed recruitment events and occasional losses from rock break-outs. More 

extensive band transect monitoring of goose barnacles at the Cabrillo sites revealed moderate 

declines from 1990 through 1994. 

Mussels had declined drastically at the Cabrillo sites from 1990 through 1995. They 

remained at low levels since 1995, except at Cabrillo I. There, mussel cover increased 

substantially in 3 of the 5 plots to the highest levels since monitoring began. Cabrillo II and III 

plots remained nearly devoid of mussels. The few remaining mussels throughout Cabrillo II 

and III areas are older individuals, with practically no sign of recruitment. Obviously, mussels 

settled and grew successfully in the 3 plots at Cabrillo I during recent years, yet mussels still 

are rare throughout this site. Perhaps the greater wave exposure at Cabrillo I provided 

marginally better conditions for mussel settlement and survival than at the slightly calmer 
Final Study Report – Engle 

17

downcoast sites. Since mussel plots were established in the few Navy locations with adequate 

cover in S95, abundances increased slightly at NN and remained unchanged at NS. 

Red turf was remarkably stable in its targeted transects at all Point Loma stations 

during the present study and all past monitoring. This mixed species assemblage dominated 

the middle intertidal flats and occurred as an understory layer lower down the shore in 

surfgrass and boa kelp zones. Red turf is highly resistant to disturbance, including abrasion 

and sand burial (Stewart 1983, 1989a). Unlike red turf, boa kelp underwent catastrophic 

declines during 1990-1995 at the Cabrillo sites. No recovery from near total losses occurred 

by 1998. Boa kelp still occurs commonly in the shallow subtidal zone and is capable of 

recovery within a few years if intertidal conditions become favorable for its re-establishment 

(Vesco & Gillard 1980). 

Owl limpet numbers were quite variable within and among plots over time, reflecting 

not only actual population changes, but also observer differences in locating cryptic 

individuals and distinguishing this species from close relatives (especially for small limpets). 

The overall slight declines at the Cabrillo sites from F96-S98 were due to losses only at 

Cabrillo II, where 2 of the cliff habitat plots showed substantial declines. Both plots incurred 

occasional rock breakouts and partial sand coverage in recent years. In addition, the high 

numbers for one of these plots (#242) in F96 and F97 samples apparently resulted from the 

inclusion of a second similar-appearing limpet species. Overall, owl limpet abundances at the 

Cabrillo sites declined slightly during 1990-1995, then increased about the same amount from 

1995-1998; the net result was relatively little change over the period from 1990-1998. Navy 

South owl limpet counts were generally similar during F96-S98, but reflected an increase in 

both small and large limpets since S95. Navy North counts were consistent from S95-F96, 

then increased substantially by S98. Most of this increase was due to additional small limpets. 

The plots at NN have numerous tiny crevices with cryptic limpets, thus it is unclear to what 

extent the changes in limpet counts here reflect actual population shifts. 

The declines in acorn barnacle, rockweed, and surfgrass cover at the Point Loma sites 

since 1995 were noteworthy because nearly all occurred after S97, during the strong El Niño 

event. Both F97 and S98 samplings took place after periods of heavy surf. Storms can tear out 

patches of plants, cause breakage of blades/leaves, dislodge organisms struck by moving rocks 

and debris, and flake off or break out sedimentary rock layers. Notably large accumulations of 

kelp wrack and drift debris were observed on the shore at all sites in F97. More than usual 

amounts of overturned rocks, cobble scoured surfaces, breakouts of sedimentary slabs, and 

damaged plot/transect markers were found during F97 and S98. Disturbance from El Niño 

storms likely “thinned out” acorn barnacles, rockweed, and surfgrass, as has been observed in 

previous studies (Gunnill 1983; Stewart 1989a; Ambrose et al. 1995; Engle & Davis 1996b). 

Both rockweed and surfgrass declined at all 5 Point Loma sites. Plants were observed to be 

not only less dense, but also shorter. Interestingly, the more exposed offshore surfgrass 

transects at NN and NS experienced greater declines than the more sheltered inshore transects. 

Both rockweed and surfgrass can recover quickly via regrowth if holdfasts or rhizomes remain 

intact. Other key species coverages appeared largely unaffected by these storms, except that 

rock breakouts in a few owl limpet, mussel, and goose barnacle plots were noted. Rocky 

intertidal monitoring sites established in F97 for the Navy at Cardiff and Scripps Reefs in 
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central San Diego County sustained greater storm damage than at Point Loma, including 

losses of rockweed, surfgrass, acorn barnacles, sand castle worms, goose barnacles, and 

mussels (Engle et al. 1998b). 

Other possible El Niño effects include increases in sea level, rainfall, and water 

temperature. The sea level rise was relatively small (perhaps 8-12 cm), and therefore unlikely 

to have a major effect. Heavy rains resulted in increased freshwater runoff, erosion, landslides, 

sedimentation, and floating debris, all of which likely caused at least localized disturbances to 

rocky shore life. Warmer water may particularly stress organisms adapted to cool conditions, 

yet intertidal biota are adapted to withstanding considerable variation in air and water 

temperatures. More significant is the fact that sea surface temperatures have been consistently 

warmer than the long-term mean since 1976, as documented by measurements taken at the 

Scripps pier from 1920-1997 (Figs. 16-17). Long-term warming has been associated with 

northward shifts in the ranges of southern species (Barry et al. 1995) and with dramatic 

declines in the abundance of zooplankton in southern California (Roemmich & McGowan 

1995). Thus, the species assemblages monitored at the Point Loma sites in 1996-1998 and 

earlier years likely reflect the cumulative effects of this 22-year warming pattern. Long-term 

declines in such species as black abalone, ochre seastars, mussels, and boa kelp may be related 

to this climate shift. 

In addition to El Niño related changes, the lengthening time series of key species 

monitoring, especially at the Cabrillo sites, has revealed various periodic, irregular, or multiyear abundance patterns. For example, minor seasonal cycles generally were evident for 5 key 

species. Rockweed and surfgrass tended to be less abundant in spring periods, while 

sargassum weed, red algal turf, and goose barnacles (in band transects) tended toward lower 

cover in fall surveys. The cover of acorn barnacles was quite variable (likely reflecting 

irregular recruitment events), while that for the multi-species red turf assemblage exhibited 

considerable stability from year to year. Surfgrass replaced boa kelp as the dominant species 

in the boa kelp transects. Owl limpets and goose barnacles on layered sedimentary rocks 

occasionally disappeared when sections of the soft rock broke out. Mussel recruitment 

eventually enhanced the mussel plots at the more exposed Cabrillo I site, while mussel losses 

in Cabrillo II and III have not been compensated for by new settlement. These examples of 

dynamic patterns and trends in Point Loma key species populations clearly demonstrate the 

importance of long-term monitoring in assessing the changing “baseline” condition of 

intertidal resources. 

Impacts from human activities on rocky intertidal ecosystems may be caused by 

various types of pollution from point sources (e.g., outfalls, vessel spills) and non-point 

sources (e.g., storm runoff, aerial fallout), and visitor activities (see Ghazanshahi et al. 1983; 

Foster et al. 1988; Anderson et al. 1993 for reviews). Impacts may range from single events 

affecting one location (e.g., a shipwreck on the beach) to chronic (but often low level), 

widespread conditions (e.g., trace metal contamination) that may show little short-term effect, 

but cause significant cumulative effects over many years or decades. Twenty-two years ago, 

Zedler (1976) compared areas varying in degree of human use at the Cabrillo National 

Monument tidepools and found lower abundances of certain coralline algae, sand castle 

worms, and limpets in more heavily-visited habitats. In experiments with turning over rocks, 
Final Study Report – Engle 

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species diversity of exposed invertebrates declined rapidly after 2 weeks, and opportunistic 

green algae invaded by 4 weeks (Zedler 1978). In trampled algal turf mats, the more brittle 

species of erect coralline algae were most impacted, with recovery estimated to take 1-2 yr 

(Zedler 1978). Human use issues for the Point Loma sites were emphasised in Engle and 

Davis (1996b,c), so only a brief update follows. 

Heavy visitor use of Cabrillo I and II sites continued through the F96-S98 project 

period; however, unlike previous monitoring during 1990-1995, Cabrillo III has been off 

limits to the public since 1996. Visitor and bird count records for the Cabrillo sites have been 

collected by Cabrillo National Monument personnel. Continued evidence of human impacts at 

Cabrillo I and II during the 1996-1998 surveys included frightened marine birds, beach debris, 

trampled habitats, overturned rocks, displaced marine life, and disturbed organisms. No 

specimen collecting was observed because this activity is prohibited in the Monument. No 

visitors were seen at the remote Navy sites or in the closed Cabrillo III area. The only obvious 

sign of human influence at these locations was scattered beach debris. The occasional explorer 

could reach the Navy sites by hiking south along the shore at low tide and collect marine life 

legally with a license. 

Although specific effects of visitor activities at Cabrillo I and II were observed as 

noted above, people effects were not obvious from the results of the key species monitoring 

during F96-S98. In general, population changes occurred similarly in public and 

restricted/remote areas, or appeared to reflect physical differences among the sites (e.g., 

mussel increases in Cabrillo I possibly associated with greater surf exposure). This should not 

lead to the conclusion that impacts are not occurring. An important consideration is that 

decades of visitor use took place prior to this study (Zedler 1976, 1978), so initial (1990) 

survey conditions were not pristine. Thus rocky shore ecosystems may be in a continuously 

disturbed state. For example, throughout all surveys, the mean and maximum sizes of owl 

limpets have been larger in the protected Cabrillo sites than in the Navy sites where collecting 

might occur. Similarly smaller owl limpets have been sampled farther upcoast at the oftenvisited Scripps and Cardiff Reefs (Engle et al. 1998). Another major consideration is that 

other (non-visitor) impacts, such as water and air pollution, are widespread, affecting all 5 

survey areas. Possible contamination sources include shoreside runoff, the San Diego Harbor, 

the Tijuana River, offshore shipping, and the Point Loma municipal outfall. With regard to oil 

pollution, scattered tar blobs were observed at all sites, but were much less common than at 

monitoring stations in Santa Barbara County (Ambrose et al. 1995). 

In summary, trends in key species abundances at the Cabrillo National Monument sites 

during previous monitoring from 1990 to 1995 included major increases in surfgrass, minor 

declines in goose barnacles and owl limpets, and greatly reduced thatched barnacles, mussels, 

and boa kelp. Since 1995, goose barnacles, thatched barnacles, and boa kelp have not 

recovered to prior levels. Mussels have increased substantially in Cabrillo I, but have not 

recovered elsewhere. Owl limpet numbers generally have increased to former amounts. Also 

since 1995, acorn barnacle cover declined slightly, and rockweed and surfgrass showed 

moderate losses, apparently as a result of 1997/1998 El Niño storms. Trends at the more 

recently-established Navy sites farther north on Point Loma generally were the same except 

that acorn barnacle and surfgrass declines here were less, and owl limpet numbers increased 
Rocky Intertidal Resource Dynamics at Point Loma, San Diego County 

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substantially. Localized impacts from public visitation in Cabrillo I and II were observed 

during the project sampling, but changes in key species abundances associated with visitor use 

were not evident. Some human impacts may be widespread and chronic. The extent of 

possible impacts is difficult to separate from natural environmental variation without 

continued long-term monitoring coupled with detailed experimental studies. 

ACKNOWLEDGMENTS 

This study would not have been possible without the initiative and understanding of 

the Project Technical Officer, Mary Elaine Dunaway. Special thanks to Gary Davis (National 

Park Service), Samantha Weber (Cabrillo National Monument), Don Lydy (U.S. Navy), and 

Mitch Perdue (U.S. Navy), for assistance in carrying out this project. Valuable help in the 

field was provided by Nancy Aguilar, Jessica Altstatt, Alan Anzak, Cleave Berdzar, Anita 

Burkett, Andrea Compton, Robert Compton, Gary Davis, Robert Gladden, Pierce Harris, 

Robin Lewis, Todd Partridge, Jennifer Rogers, Erik Steenblock, Cynthia Taylor, Samatha 

Weber, Melissa Wilson, and a host of Cabrillo National Monument volunteers. We gratefully 

acknowledge Don Lydy for arranging access to Fort Rosecrans Military Reservation and 

providing the services of Navy photographer Alan Anzak during the field surveys. 

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Figure 1. Point Loma rocky intertidal monitoring sites. 
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The Department of the Interior Mission 

As the Nation's principal conservation agency, the Department of the Interior has responsibility for most 

of our nationally owned public lands and natural resources. This includes fostering sound use of our 

land and water resources; protecting our fish, wildlife, and biological diversity; preserving the 

environmental and cultural values of our national parks and historical places; and providing for the 

enjoyment of life through outdoor recreation. The Department assesses our energy and mineral 

resources and works to ensure that their development is in the best interests of all our people by 

encouraging stewardship and citizen participation in their care. The Department also has a major 

responsibility for American Indian reservation communities and for people who live in island territories 

under U.S. administration. 

The Minerals Management Service Mission 

As a bureau of the Department of the Interior, the Minerals Management Service's (MMS) primary 

responsibilities are to manage the mineral resources located on the Nation's Outer Continental Shelf 

(OCS), collect revenue from the Federal OCS and onshore Federal and Indian lands, and distribute 

those revenues. 

Moreover, in working to meet its responsibilities, the Offshore Minerals Management Program

administers the OCS competitive leasing program and oversees the safe and environmentally sound 

exploration and production of our Nation's offshore natural gas, oil and other mineral resources. The 

MMS Royalty Management Program meets its responsibilities by ensuring the efficient, timely and 

accurate collection and disbursement of revenue from mineral leasing and production due to Indian 

tribes and allottees, States and the U.S. Treasury. 

The MMS strives to fulfill its responsibilities through the general guiding principles of: (1) being 

responsive to the public's concerns and interests by maintaining a dialogue with all potentially affected 

parties and (2) carrying out its programs with an emphasis on working to enhance the quality of life for 

all Americans by lending MMS assistance and expertise to economic development and environmental 

protection.