A comparison of multiple biological metrics between the Point Caution research reserve and neighboring public access sites
Marine Conservation Biology (Biol 533) Friday Harbor Laboratories Summer Term B 2004
Students: Sofia Copello Nichole Dean Kirsten Evans Adriana Paulina Guarderas Lisa Haderlie Jamie Northern Ray Outlaw Mariela Pajuelo Sofia Ribeiro Chelsie Papiez Heidi Weiskel
Instructors: Terrie Klinger Marjorie Wonham Carrie Kappel
Key Words: Point Caution, marine reserve, intertidal, larval, human use
1 Abstract We investigated differences between a marine regulatory research reserve and five public access areas on San Juan Island in Washington State, USA. In the Point Caution research reserve, human visitation is largely restricted to the scientific research community. We hypothesized that the research reserve would have a different human use profile compared to public access areas, which would be reflected in the present and historical diversity and abundance of benthic intertidal species, incidence of three non-native species, and bird use. We measured each of these variables, and additionally sampled larval settlement to determine whether there were differences in larval supply between sites. Results indicate that human abundance was significantly lower at Point Caution, and the number of boats significantly higher. Point Caution had the highest species richness of all sites, and significantly higher abundances of two non-native species. We found no significant relationship between the abundance and frequency of focal intertidal taxa and human abundance, and overall there were strong similarities among all locations in intertidal community composition. We found no significant differences in bird abundance or activity among locations. Point Caution had the highest abundance but lowest taxonomic richness of newly- settled larvae. Beyond these immediate comparisons, this study establishes a baseline for determination of trends in the natural variation in abundance and distribution of species and assemblages in the six sites studied.
2 Introduction Marine protected areas (MPAs) are a management tool commonly used with the intent of increasing the diversity and abundance of marine organisms not only within the protected area but also the surrounding region. Reserves are thought to provide corollary benefits such as enhancing resilience and stability within ecosystems. Not only is it a good management practice to monitor and evaluate the impacts of a management tool such as MPAs over time, but the results of such monitoring often are critical in generating the political will to establish additional MPAs in other places. MPAs can lead to significant increases in the abundance and size of economically desirable fish and invertebrate species within the reserve, and under appropriate conditions can yield a spillover effect for mobile juvenile and adult animals. The degree to which MPAs might replenish populations at local and regional scales through larval dispersal is currently an active area of research. The impacts of protection on intertidal communities are less well studied Our study focuses on the effects of protection at Point Caution on San Juan Island in Washington State, USA. We used an observational approach to investigate the impacts of protection by comparing various ecological parameters at Point Caution and five public access areas along the San Juan Channel. We hypothesized that the research reserve would have a different human use profile than the public access sites, and that this different would be reflected in the diversity and abundance of intertidal marine organisms and birds. We also quantified larval delivery to these areas to test for differences in the supply of larvae between sites.
Materials and Methods Study locations and site selection Surveys were conducted in July and August 2004 in the San Juan Archipelago on San Juan, Lopez, and Shaw Islands. The San Juan Archipelago is located at the southern end of the Strait of Georgia, northeast of Juan de Fuca
3 Strait, and north of Puget Sound proper (Figure 1, after Thomson 1981; Klinger and Ebbesmeyer 2001). We compared features of the research reserve established by the Washington Department of Fish and Wildlife at Point Caution on San Juan Island with five nearby public access areas (Figure 1). The Point Caution reserve is a 484-acre terrestrial biological preserve with approximately 7.7 km of rocky shoreline habitat. The site has been owned by the University of Washington for about a century. The university’s Friday Harbor Marine Laboratories are located within the reserve. Although it is state property, access to the terrestrial portion of the reserve is restricted to laboratory personnel and authorized visitors. This policy and the heavily forested, rocky and often precipitous shoreline effectively restrict human access to much of the shoreline portion of the reserve. These protections were strengthened in 1990 by the designation the intertidal and nearshore waters as a marine research reserve, jointly managed by the University of Washington and the Washington Department of Fish and Wildlife. Biological resources within the research reserve are protected under WDFW’s regulatory authority. Although regulatory protections are rarely enforced, compliance with the regulatory protections appears to be fairly high. Prohibited activities include removal of non- commercial species, including bottomfish and shellfish. The reserve is inaccessible to the general public by land, but is used regularly by researchers and students. The public access areas all are accessible by car and foot. They receive variable amounts of visitation by residents, tourists, school groups, and researchers, and have few, if any, prohibited activities comparable to those of the research reserve. Three of the areas we studied are on San Juan Island: Reuben Tarte, the northernmost site, is a county park; Cattle Point, the southernmost site, is an interpretive area within a National Historical Park; and Third Lagoon, near Cattle Point, is a state recreation area (Table 1, Figures 1-2). We also sampled at Shaw Island County Park on the southern shore of Shaw Island, and at Shark Reef Recreation Area on the western shore of Lopez Island (Figures 1-2). For
4 consistency and comparability, all locations were located within San Juan Channel and all contained rocky intertidal reefs, but sites differed in shoreline length and proximity to harbors and marinas. We sampled diversity and abundance of benthic intertidal species, abundance of three non-native species, abundance and diversity of settled larvae, and abundance and activities of birds and humans at each location. Additionally, we made comparisons with historical intertidal data. In all cases, we refer to the research reserve and each public access area as a location, and to sampling areas within locations as sites. Three of the six locations (Pt. Caution, Reuben Tarte, and Cattle Point) contained areas of both high and low nearshore current flow (subjectively determined by observation of maximum tidal flow), so site selection in these locations was stratified by flow. In all cases, sites were randomly located within location and flow areas (Figures 1-2).
Human Use We estimated human use at each location on Saturday, August 14, 2004 (Figure 2). At 15-minute intervals from 11 am to 2 pm during an incoming tide (low of -0.3 m at 10:40 am), we noted the number of people and dogs and their apparent activities on the intertidal bedrock and adjacent beach. We also counted the number of motorized (including sailboats under power) and non-motorized vessels within 100 m of the shore. We did not include ourselves in our counts. We counted all individuals (other than ourselves) within the sampling area at each sampling interval, whether present in the previous count or not. The sampling design is shown in Figure 3. Each observer marked the area observed on a magnified aerial photo (Washington State Department of Ecology
5 shoreline distance surveyed using the ‘measure’ function in ArcGIS MapView v8.3 (ESRI, 2004 ArcGIS 9.0) at 1:2000 resolution (Table 2).
Intertidal diversity and abundance At each site, we positioned five transects perpendicular to shore at randomly determined positions along a 6-m long tape positioned parallel to shore at the top of the barnacle zone. Our transects extended to the bottom of the Fucus gardneri zone, ending where Ulva spp. and other mid- to lower-tidal algae began to dominate. Along each transect, we sampled five 25 x 25 cm square quadrats at randomly determined positions. At each site we sampled five quadrats along each of five transects for a total of 25 quadrats. The sampling design is shown in Figure 4. Within each quadrat, we estimated percent cover of Fucus and three common species of barnacle, Balanus glandula, Chthamalus dalli, and Semibalanus cariosus. Additionally, we counted five limpet species, Lottia digitalis, L. pelta, L. paradigitalis (= L. strigatella), Tectura scutum, and Onchidella borealis. We recorded the presence of all other observed macroscopic algae and invertebrates to the lowest taxonomic level possible in each quadrat. All sampling was performed in a single tide series, July 29-August 3, 2004 (Table 3). To calculate taxon richness for each site, we used the diversity software EstimateS (Colwell 1997). Because the rarefaction curves for the six locations did not reach asymptotes, we used a non-parametric second-order Jackknife estimator of taxon richness (Jack-2). To determine which Jackknife estimator to use, we calculated the true number of species by using reference species richness surveys (Barneah et al. 1999; Marine Phycology 1984, 1993). This extrapolation method is used in biodiversity studies to estimate species richness, and is commonly used when sampling is inadequate to fully characterize the richness of a community or area (Brose 2003). The estimator is
2m − 3 m − 2 2 ( ) Sest = Sobs + Q1 − Q2 , m m(m −1) 6 where Sest is the number of species estimated, Sobs is the total number species observed, m is the total number of samples, and Qj is the number of species that occur in exactly j samples (i.e., Q1 is the number of species that occur only once and Q2 the frequency of those that occur only twice)
Historical data We used data collected in two prior surveys to draw temporal comparisons of focal species abundance at our survey locations. Over a period of four years (1974-1978), a research team at Friday Harbor Laboratories conducted a baseline ecological survey at Cantilever Point, which is the same as our Point Caution site C (Nyblade 1977, 1978). We compared Fucus and barnacle abundances between these historical data and our survey. Second, permanent quadrats at Reuben Tarte County Park have been sampled annually by the Friday Harbor Labs ZooBot class since 1989. We compared Fucus, barnacle, and limpet abundances between these surveys and our own. Differences in sampling design and methods between our study and the historical studies necessitated the conversion of various metrics. We calculated a correction factor in the field to convert our percent cover of Fucus into biomass, and percent cover of barnacle species into number of individuals. To convert from percent cover to biomass, we estimated percent cover for 8 samples using a 25 x 25 cm quadrat, removed the F. gardneri, and obtained a fresh weight. A linear regression of these two variables was obtained; we used the slope of this line as our correction factor. Similarly, we converted barnacle percent cover to number of individuals by using the slope of the regression line as the correction factor.
Non-native species We counted living and dead Crassostrea gigas and empty Nuttallia obscurata shells at each location. Surveys were conducted at low tide, and consisted of a 5-minute timed beach-walk between the water and the high-tide mark for each species independently (Figure 5). We visually estimated the area
7 we surveyed (Table 4). This approach greatly underestimated the number of Nutallia present, because it did not capture living individuals within the sediment. However, for the purposes of this study, we assumed the number of empty shells observed were proportional to the number of living individuals at the site and could be used to make comparisons between sites. We counted Sargassum muticum thalli from the shoreward side of a small boat traveling at a constant speed 3-10 m from shore in water approximately 1-5 m deep. Two observers counted thalli in sequential 60-second blocks, and we averaged these counts to obtain a more accurate estimate. This estimate includes only the reproductive fronds reaching the surface, and is therefore an underestimate of total abundance. However, this method provides a measure of relative abundance by which to compare sites. With a hand-held GPS unit we marked waypoints for calculation of distance traveled and Sargassum frequency (number of individuals observed per meter) (Figure 6).
Larval settlement and distribution To measure larval delivery, we placed one larval collector at the approximate mid-point of each study location. Each collector consisted six replicate Tuffys™ (plastic kitchen scrubbers to which certain larvae settle) tied to a 1.5 m PVC pipe. The pipe was suspended horizontally at approximately 1 m below the surface. Each collector was anchored at approximately 5 m depth, buoyed at the surface. All collectors were deployed on the same day and tidal cycle. After four days we retrieved the collectors, placed each Tuffy™ in a plastic bag, refrigerated them at 4 C, and enumerated the contents within 2-36 hours. Sampling design is shown in Figure 7. To extract the settled larvae, we soaked each Tuffy™ in a 3.5% solution of
MgCl2 for five minutes before transferring it to a second beaker of MgCl2. We filtered the solution from the first beaker though a 130-153 µm mesh and gently washed the resulting material back into a finger bowl. We used a stereomicroscope to count and identify all larvae observed. We then removed the Tuffy™ from the second beaker, cut it lengthwise, and gently sprayed the
8 remaining organic matter from its surface. The second wash was treated like the first.
Birds We surveyed intertidal and shoreline birds at all locations on August 12, 2004 (Figure 8). Low tide this day was -0.18 m at 9:20 a.m. At 15-minute intervals between 6:30 and 9:30 a.m., we used binoculars to count all birds up to 15 m off shore and note their activities. The birds were categorized as gulls/terns, cormorants, shorebirds, herons, ducks, ravens/crows, raptors, or kingfishers. Using aerial photos, observers identified the shoreline they surveyed (http://apps.ecy.wa.gov/shorephotos/scrpits/mapsearch.asp?id=960). Our survey areas were located in the Department of Ecology’s aerial photo database, and the length of the shoreline we surveyed was measured directly from the computer screen (http://apps.ecy.wa.gov/website/coastal_atlas/viewer.htm) and multiplied by 50 m (offshore) to calculate the total area observed. Sampling design is shown in Figure 8.
Statistical analysis For datasets with one replicate per location or location/flow combination (humans, oysters, Sargassum, larvae, birds), we compared the Point Caution value to the mean and 95% confidence interval of the five public access sites. We also used Chi2 contingency-table analysis to compare the distribution of human and bird activities. For datasets with multiple taxa (intertidal and larval surveys) we used ANOVA and posthoc pairwise t-test comparisons with alpha=0.05 to compare individual taxon abundances across locations (using the software package JMP 5.1). We also used nonparametric multidimensional scaling (nMDS) ordination, ANOSIM (a permutation test to test for similarities among treatments), and SIMPER (to assess the contributions of individual species to similarities among groups) to compare locations using the software package PRIMER-E v.5. Finally, we used correlation and regression analyses to compare variables across locations
9 (using JMP v. 5.1). For all parametric analyses, percent cover data were arcsin- square root transformed and count data were ln(x+1) transformed to improve normality. For multidimensional analyses, the data were not transformed. Raw data are reported in the Appendix.
Results Human use At Point Caution, total human abundance was significantly lower than at public access locations, and the number of boats counted was significantly higher (Table 5). We observed very few dogs (three at Point Caution that were rowed ashore in boats, and 14 total across all public access sites). The human use profile (comparing the number of resting vs. active humans) did not differ significantly between Point Caution and the five public access locations combined (Fisher’s Exact test, p = 0.103). However, at Reuben Tarte and Point Caution together, humans were significantly more active than at the other four sites combined (Fisher’s Exact test, p = 0.023). We tested the hypothesis that human abundance is negatively correlated with barnacle abundance (for example, via trampling, Erickson 2002) (Table 6). We found that the abundance of Chthamalus dalli was significantly negatively correlated with human abundance (thereby decreasing with increasing human use; R2 = 0.16, p = 0.02). Interestingly, the frequency of Semibalanus cariosus showed a significant positive correlation with human use (R2 = 0.20, p=0.01). We found no significant correlation between human abundance and the percent cover or frequency of Fucus or the number of limpets at any site.
Intertidal diversity and abundance Taxon richness We used data from the intertidal quadrat sampling to construct rarefaction curves for all locations and for high and low flow locations independently (Figures 9, 10, and 11, respectively). None of the curves for Lopez, Shaw, and Cattle Point (combined low and high flow) reached asymptotes (Figure 9), nor did
10 any of the high flow sites (Figure 10). However, rarefaction curves constructed from data from low flow sites at Cattle Point, Third Lagoon, and Reuben Tarte did appear to reach asymptotes (Figure 11). Overall, Point Caution had the highest total observed and estimated taxon richness (Sobs=77, Sest = 92), and Third Lagoon had the lowest (Sobs = 51, Sest = 63)
(Figure 12). Point Caution had higher estimated taxon richness in low flow (Sest =
93) than high flow sites (Sest = 84), whereas both Cattle Point and Reuben Tarte had higher richness in high flow (Sest = 78, 88 respectively) than low flow sites
(Sest = 68, 57 respectively; Figures 13- 14). We found no significant correlation between estimated species richness and the number of humans using the intertidal (total, bedrock, or beach).
Abundance of focal species Figures 15-18 show the abundance of Fucus, limpets, and barnacles by location and flow. The mean abundance of Fucus was significantly higher at low flow sites (Table 7, Figures 15-16). The significant flow by location interaction appears to be driven by higher percent cover at low flow than high flow sites at Cattle Point. The abundance of Chthamalus dalli differed significantly among locations (Table 7, Figures 15-16). With respect to limpets, Lottia paradigitalis was the most abundant in all locations, followed by L. pelta, with Onchidella borealis least abundant (Figures 17-18). The abundance of L. paradigitalis was significantly influenced by the interaction of location and flow (Table 7), which results from opposite patterns in abundance at Cattle Point (higher abundance at high flow sites) and Point Caution (higher abundance at low flow sites). The correlation coefficients obtained for some pairs of focal taxa are shown in Table 8; none of the relationships were strong.
Community composition We found strong similarities in community composition among locations (Figure 19). Because cluster analyses ordinated five sites outside the main group,
11 we used functional groups rather than taxa for further analyses. Cattle Point site B, which had a number of small tide pools, differed from the other sites in all functional groups (Figures 20-22). Point Caution site E had more predators than the other sites (Figure 21). Cluster analyses of the nMDS and additional ordinations identified three groups, A, B, and C, which contained a mixture of sites from different locations that share similarities in community composition between 62 and 85% (Figure 23) and are significantly different from each other (ANOSIM R = 0.55, p = 0.01). According to SIMPER analysis, inter-group likeness was driven primarily by the frequency and abundance of Balanus glandula, the petrocelis phase of Mastocarpus papillatus, and Fucus gardneri. Groups A and B were unalike due to the effects of Cladophora spp. (C. columbiana plus C. sericea), Hildenbrandia rubra, Cryptosiphonia woodii, and Polysiphonia spp. Dissimilarities between groups A and C were mainly due to Chthamalus dalli, while differences between groups B and C were driven by the presence of Cladophora spp.
Historical data Our review of historical data for Reuben Tarte indicates that for many of the years surveyed, the community has been dominated by Fucus gardneri (Figure 24). Abundance of Fucus declined through time; this trend is more pronounced in the high intertidal than in mid-to-high zones. Since 1998, there has been a dramatic decline in Fucus percent cover and a marked increase in limpet and barnacle abundance (Figures 24-26). We summarized the distribution of focal species through time for Point Caution (Figures 27-29). The abundance of our focal species was highly variable over short temporal periods (months) during the 1970s. The cover of Fucus and barnacles at Point Caution was generally low except for September 1974 and August 2004. Limpets dominate this community, although their abundance varies considerably between years (Figure 29). Across years, the abundances of limpets and barnacles were negatively correlated with Fucus percent cover at Reuben
12 Tarte, and positively correlated with Fucus percent cover at Cantilever Point (Table 9).
Non-native species The abundance of Crassostrea gigas was significantly higher at Point Caution than at public access sites in high-flow areas only (Table 10). Overall, we found that C. gigas tended to be more abundant in low flow than high flow sites. The mean number of oysters per m2 ± 1 S.D. at low flow sites was 0.121 ± 0.110, and at high flow sites was 0.0115 ± 0.0139 (t = 2.19, df = 4, p < 0.1). Our sampling method does not account for the patchy distribution of oysters on these reefs. Therefore, these estimates include large areas of rocky reef from which C. gigas is absent; where it occurs within these sites, the density of C. gigas typically is much higher than our estimates suggest. Consequently, while our estimates of oyster density are useful for purposes of comparison between sites, they do not capture the distribution of higher-density patches within these sites. There was a significant inverse correlation between human and C. gigas abundance (r = -0.80). Trends in densities of living and dead C. gigas considered separately were indistinguishable from those of total abundance. The abundance of Sargassum muticum was significantly greater at Point Caution than at public access locations (Table 10). The abundance of Nuttallia obscurata did not differ significantly among locations; this result could be due to low encounter rates resulting from our sampling design. We used correlation analyses to identify relationships among taxon diversity, C. gigas abundance, S. muticum abundance, and larval abundance. There was a strong positive relationship between S. muticum and larval abundance (r = 0.62). Additionally, we tested three hypotheses using linear regression, specifically that: 1) oyster abundance is driven by larval abundance, 2) S. muticum reduces larval delivery and therefore intertidal taxon richness, and 3) taxonomic richness confers resistance to oyster invasion and leads to reduced oyster abundance (Table 11). There was a marginally significant negative relationship
13 between C. gigas and diversity (Table 11), suggesting that the data support only the third of these hypotheses.
Larval settlement and distribution We identified seven numerically dominant taxonomic groups among the larvae in our collectors (Figure 30). To test whether locations differed in larval delivery, we used nMDS to compare larval richness among locations using flow regime, location, and protection status as factors. The six sites differed based on location (R = 0.451, p < 0.01) and flow (R = 0.172, p < 0.01), but not on status (protected vs. public access) (R = -1.000, p = 1.00) (Figure 31). Pair-wise comparisons indicated that Point Caution and Reuben Tarte were more similar to each other than to the remaining locations. Larval abundance at Point Caution exceeded the upper 95% confidence limit of the public access locations in abundance of Nereid-like setigers, gastropod veligers, and total abundance. However, it fell below the lower 95% confidence limit for taxonomic richness (Table 12). We tested whether the frequency and abundance of organisms on the shore were associated with the abundance of settling larvae. Specifically, we tested the abundance of C. gigas versus larval bivalve abundance, barnacle frequency and abundance versus larval barnacle abundance, and intertidal taxon diversity versus total larval abundance (Table 13, Figure 31). We found a significant positive relationship between the number of oysters on the shore and the number of larval bivalves in our traps; we found no significant association between the abundance of adult and larval barnacles, nor between intertidal taxon diversity and total larval abundance.
Birds We found no significant differences in relative abundances of birds between Point Caution and the public access locations (Table 14). Total abundance of birds, abundance of crows and ravens as a group, and abundance of gulls and terns as a group did not differ among locations.
14 There were no significant differences in observed activities of the birds among locations (Chi2 = 0.001, df = 5, p > 0.05) or between high and low flow sites (Chi2 = 0.38, df = 1, p > 0.05). In addition, we tested possible effects of two disturbance factors – humans and boats – on the total number of birds, but found no statistically significant relationship for either (Table 15).
Discussion In aggregate, our findings suggest that differences exist between the intertidal communities within the Pt. Caution reserve and those in the public access areas we studied. However, the sign and magnitude of these differences vary in ways that are not entirely predictable. Our results are discussed in more detail below.
Human use profile Our quantitative assessment of human activities that impact intertidal communities suggest that the Point Caution research reserve does experience lower abundances of humans in rocky intertidal habitats than the public access sites, and that humans tend to be more active at Point Caution and Reuben Tarte than at other sites. Because our time constraints prevented sampling on more than one day, the data are sparse. Nonetheless, it seems reasonable that unauthorized individuals entering an actively protected restricted-access research reserve would likely spend little time resting in the intertidal, and that authorized laboratory personnel in the intertidal are likely to be moving about collecting data. Further efforts to characterize human abundances and use patterns of these sites are warranted to document the degree to which each site is directly impacted by human presence and activities such as trampling and collecting. It would be particularly helpful to document the extent to which the research projects and classes held at the marine laboratory use and impact the Point Caution shoreline.
15 Intertidal community composition Fucus gardneri was most abundant at Third Lagoon. Although this is a public access location, it exhibited the lowest human abundance of all locations studied, including the Point Caution Reserve, with no humans, dogs or boats present during our sampling period, despite the fact that we surveyed for three hours at midday on a summer Saturday. However, regression analyses showed no apparent relationship between Fucus abundance and human abundance. Furthermore, our results showed that flow significantly affects Fucus abundance (which is higher in low flow sites). Therefore, the differences observed between sites could be due to factors other than human visitation. We observed a negative correlation between Fucus and barnacle abundance. This could be due to physical factors (e.g., the differential effects of flow-induced particle flux and flow-induced drag forces on barnacles versus Fucus). Alternatively, the observed relationship could be an artifact of sampling (where Fucus is dense, barnacles are more difficult to enumerate). We observed a positive correlation between Balanus glandula and Chthamalus dalli that is the opposite of what one would expect based on Connell’s (1961) research. Our results suggest that competition may not be the primary driver of B. glandula and C. dalli abundances at the sites we studied. Other physical and ecological factors, such as site aspect, substrate temperature, and differences in the abundance of barnacle predators, may act in concert with human visitation to reduce the importance of competition in determining barnacle abundance at the sites we studied. Alternatively, experimental design issues may be a factor: our samples were not stratified by tidal height, so the abundance of mid-intertidal B. glandula is compared with the abundance of C. dalli higher in the intertidal. Our analyses offer incomplete spatial resolution at this scale. Our results indicate that human abundance negatively impacts the abundance but not the frequency of occurrence of Chthamalus dalli. This result is consistent with the effects of trampling in the high intertidal, where most visitors walk, but we did not test the impacts of trampling directly.
16 Taxon richness was highest at Point Caution, but many of the rarefaction curves did not reach asymptotes, which indicates that our sampling intensity was insufficient to capture total richness. Even so, our results suggest 1) Point Caution has the highest taxon richness, but 2) that differences in species richness and community composition between locations were not statistically significant. Point Caution exhibited a wide diversity of local taxa within the site level, which suggests that the intertidal communities there are representative of local intertidal diversity, thereby adding to the location’s value as a marine reserve. Whether the higher taxon richness found at Point Caution is related to the degree of actual protection from human impacts afforded by the research reserve requires analysis of historical information on species richness and abundance, as well as intensity and types of human use at each of our sites. Similarly, evaluating whether limiting human access acts to maintain local diversity would require ongoing monitoring of both species richness and human use at Point Caution and our five public access sites. A number of studies have focused on the direct and indirect impacts of one specific human activity in the intertidal: the trampling of intertidal organisms by humans walking and otherwise moving about on rocky shores (e.g. Keough and Quinn, 1998). In controlled trampling experiments in Australia and the western United States, intermediate and high levels of trampling resulted in substantial reductions in brown algal cover that persisted up to several years (Keough and Quinn, 1998). Additional effects include loss of other algal species via dislodgement, and of barnacle, mussels and limpet species via crushing, as well as indirect effects mediated by physical (e.g., wave action) and ecological (e.g., grazer) interactions. Fewer studies have used observational approaches to determine the effects of trampling. However, a recent study by Erickson (2002) suggested that actual levels of human trampling in a National Park can significantly affect intertidal communities. At Starfish Point, Olympic National Park, Fucus gardneri, Lottia strigatella (=L. paradigitalis), and L. digitalis were negatively affected by trampling (Erickson 2002). In Erickson’s study, areas characterized by high rates of visitation and trampling exhibited higher abundance
17 of these three species and C. dalli, while the least-visited area was dominated by S. cariosus and B. glandula. These results, particularly those for C. dalli and S. cariosus, are inconsistent with the results obtained in this study, but all seem to demonstrate the potential for human disturbance via trampling to influence the abundance of benthic organisms in rocky intertidal areas.
Historical data Our review of historical data indicates that focal species at Cantilever Point and Reuben Tarte have fluctuated through time. The abundance of Fucus gardneri has generally declined over time, although a slight increase was observed in 2004 at Cantilever Point. Nyblade (1977) found that the algal community undergoes pronounced seasonal changes in additional to interannual variation. Although historical data from Cantilever Point and Reuben Tarte are not strictly comparable because the surveys were conducted in different years, the trends between sites indicate that Fucus is more abundant at Reuben Tarte than at Cantilever Point, but that Fucus abundance is generally declining at both sites (with an exception at Cantilever Point in August 2004). However, we cannot attribute this difference to differences in the status of the sites (research reserve vs. county park), because the Nyblade studies (1974-1979) predate the establishment of the research reserve by more than a decade (with no intervening data), and because we have not tested differences in physical or biological factors between the two sites that could account for this difference. Therefore, although the studies of Nyblade (1977) and the Friday Harbor Laboratories Zoology/Botany classes are helpful in making coarse comparisons, these data are not sufficient to detect many trends that might exist, nor are they sufficient to make robust comparisons over time. In particular, sampling intensity was likely insufficient in all 3 studies, and the design of the Nyblade study causes repeatability to be very low. It is important to establish permanent transects or fixed plots from which to draw comparisons (this was done in the ZooBot study at Reuben Tarte, but not
18 in the Nyblade study). Replication is critical when designing such experiments. In this context, the relevance and valuable contribution of the present study lies in the establishment of a baseline to document the natural variation in abundance and distribution of species and assemblages in different locations and a comprehensive number of replicates, which can be compared in the future.
Non-native species One of the arguments advanced for maintaining or increasing native biodiversity is that greater biodiversity may provide greater ecosystem resilience in response to non-native invasive species. Our results from high flow sites showed significantly greater abundance of Crassostreas gigas at Point Caution than at public access locations. Similar analyses of low flow locations did not show significant differences between sits. We found a negative relationship between the abundance of C. gigas and taxon diveristy. Prior research suggests that declines in diversity can result from competitive interactions between sessile organisms for space, while other research suggests that increased diversity decreases the potential for invasion success (Masten 2003, Stachowicz et al. 2002). Our results do not differentiate between these two hypotheses, and further research will be needed to explore this relationship. Although our results appear to contradict the hypothesis that greater species richness provides protection against invasion of non-native species, the significantly greater abundances of C. gigas we found at high flow sites at Point Caution may be attributable to one or more confounding variables. For example, current patterns in the San Juan Archipelago suggest the existence of a strong ebb current along all Point Caution high flow sites that may influence larval distribution. Water exiting the San Juan Channel on ebb tides flows along the Pt. Caution shoreline. Some of this water originates in bays such as Deer Harbor and West Sound on Orcas Island, areas with particularly high densities of oysters. Our analysis of larval delivery confirms that larger numbers of larvae settled onto collectors at Pt. Caution compared with our other sites.
19 Human use profiles of our sites indicate another possible explanation for our findings. Abundances of C. gigas were inversely correlated with the abundance of humans, suggesting that human harvest may play a role in oyster density. However, only one instance of collecting (by a small child) was recorded, and the number of empty valves attached to rocks (left behind when oysters are harvested from rocky shores) was generally low, indicating that harvest rates are similarly low. Abundances of C. gigas overall were marginally different between high and low flow sites. This result, combined with field observations, suggests that replication limited our statistical power. C. gigas is believed to perform better in areas with warmer water temperatures. Some research suggests that larval retention and settlement increase with increasing temperature. Thus, higher temperatures and flow rates combined could lead to higher densities of C. gigas at some locations. Densities of Sargassum muticum were much greater at Point Caution than at public access locations, and a strong positive correlation was found between the abundance of S. muticum and larval abundance. S. muticum is a subtidal alga, and its propagules may be distributed by currents in a manner that reflects larval dispersal. Additionally, densities of S. muticum may be directly affected by sea urchin abundance. Research suggests that native subtidal kelp species, which are a preferred food item for sea urchins, may provide resistance to S. muticum invasion due to light reduction effects (Britton-Simmons 2003). Thus, high urchin abundances may facilitate S. muticum invasion by reducing kelp densities. Our sampling location at Pt. Caution is within a zone that has been closed to urchin fishing for more than a decade. Urchin fishing is allowed within our other study locations. Interestingly, Reuben Tarte lies on the northern boundary of the urchin fishery closure; Sargassum abundance there falls outside of the 95% confidence interval of the four remaining locations (exclusive of Point Caution). Our findings suggest that sea urchins may have a strong positive effect on S. muticum invasions and that urchin fishery closures may facilitate invasion by this species.
20 Larval settlement and distribution Our results indicate no significant difference in taxon diversity among settling larvae between Pt. Caution and Reuben Tarte; this result is contrary to our expectation. Both sites are located in the northern half of San Juan Channel, but they differ in flow regime. Reuben Tarte is likely more exposed to water coming from the Strait of Georgia than is Pt. Caution, which is likely more exposed to water entering San Juan Channel from the south. These differences in circulation are not reflected in the diversity of settling larvae. In contrast, the similarity in larval settlement between Third Lagoon and Cattle Point could be explained by the sites’ geographic proximity at the extreme southern end of the San Juan Channel. We found no significant differences overall in taxon richness of settled larvae among locations. However, we found higher abundances of larvae on our collectors at Point Caution than at other sites. This pattern was driven largely by the abundance of nereid-like setigers, which are common in the waters around San Juan Island in August (Strathmann 1987). If the abundance of setigers is a reasonable proxy for overall larval supply to the Point Caution reserve, then the results of this study suggest that the Pt. Caution reserve is sited in a favorable location with respect to larval delivery. Larvae exhibit a high degree of variability in the timing and duration of their planktonic phase. In this study, our constrained sampling period necessarily limited the diversity of taxa sampled to those that are present in the plankton in the mid- to late-summer. The nereid polychaete larvae are most abundant in the plankton during July and August (Strathmann 1987). Flatworm larvae are abundant in the plankton throughout the summer months. Barnacle nauplii and cyprids from several species are likely to be in the water column in August. The gastropod larvae we observed could have been, based on breeding season, Littorina scutulata, Lacuna spp., Lottia digitalis, or Fusitriton oregonensis (Strathmann 1987). The bivalve larvae we observed could have been a variety of
21 native and non-native species of muscles, oysters, and clams that are all most abundant in the plankton in the late summer (Strathmann 1987).
Birds Disturbance caused by recreational use of beaches and shores may have important effects on the population dynamics of birds (Robertson & Flood 1980, Burger 1995). In this study, we did not find significant differences in any of the variables we considered between locations or flow regimes. This study may, however, be biased because not all observers were trained in bird identification and because replication was very low. Furthermore, historical abundances of birds at these sites are unknown, but it is possible that bird abundance across all sites is converging towards similar levels due to long-term changes in the environment, including changes induced by human use of the shoreline. Many studies report that birds can tolerate people, and do in fact become accustomed to human disturbance (Yorio 2001, Fitzpatrick and Bouchez 1998). Moreover, noise level is known to impact bird behavior and the magnitude of their responses (Burger 1998). We found no significant differences in the abundance of birds feeding or resting between locations. This finding suggests that birds may seek more isolated locations in response to human activities (McCrary & Pierson 2000). Efforts to characterize the impacts of disturbance on bird species should be increased in order to improve conservation guidelines in the San Juan Archipelago. The adequate management of protected areas and sustainable human use of shoreline areas require conservation and management tools if long-term viability and integrity of bird populations is to be achieved.
Summary Our analysis explored ecological, physical and human factors affecting the abundance of native and non-native intertidal species in the Point Caution research reserve compared with five nearby public access locations. For a few metrics, we found significant differences between the reserve and public access areas that are consistent with the effects of regulatory protection. However, our
22 study did not test causation, and therefore we cannot confidently attribute the differences we observed to the effects of protection. Our results highlight the need for reserve monitoring programs to establish baselines inside and outside the protected areas, as well as the need to collect fine-scale data on a regular and repeatable basis. Our results also suggest that the use of proxies or indicator species may be insufficient to detect trends in biological variables. These findings have implications for the design of monitoring programs, especially regarding the levels of effort and funding that will be required for successful monitoring and evaluative programs.
Acknowledgements We thank the Director and staff of the Friday Harbor Laboratories for their contributions to this project, and Megan Dethier for providing unpublished data collected by scores of ZooBot students at Reuben Tarte.
23 References
Britton-Simmons, K. 2003. Establishment, spread, and impact of the non-native Japanese seaweed, Sargassum muticum, in the San Juan Islands, Washington Dissertation, University of Chicago. Brose, U., N.D., Martinez, R.J., and Williams. 2003. Estimating species richness: sensitivity to sample coverage and insensitivity to spatial patterns. Ecology 84:2364-2377. Burger, J. 1995. Beach recreation and nesting birds. Page 281-296 in R. L., Knight and K. J., Gutzwiller, editors. Wildlife and recreationists: coexistence through management and research. Island Press Washington D. C. Clarke, K.R., R.N., Gorley. 2001. PRIMER v5: User Manual/Tutorial. PRIMER- E: Plymouth. Class Project. 1996 Reuben Tarte Survey. University of Washington. Friday Harbor Laboratories. Zoology/Botany. Colwell, R. K. 1997. EstimateS: Statistical estimation of species richness and shared species from samples. Version 5. User's Guide and application published at: http://viceroy.eeb.uconn.edu/estimates. Connell, J. H. 1961. The influence of interspecific competition and other factors on the distribution of the barnacle Chthamalus stellatus. Ecology 42:710:723 Erickson, A. 2002. Effects of human trampling on intertidal communities at Starfish Point, Olympic National Park, Washington. University of Washington FHL class. unpublished data. Keough, M.J. and G.P, Quinn. 1998. Effects of periodic disturbances from trampling on rocky intertidal algal beds. Ecological Applications 8:141-161. Klinger, T., and C., Ebbesmeyer. 2001. Using Oceanographic Linkages to Guide Marine Protected Area Network Design. Puget Sound Research. Masten, M. 2003. The effects of Crassostrea gigas on intertidal communities in the San Juan Islands. University of Washington Friday Harbor Laboratories – Marine Zoology 430/Marine Botany 445.
24 McCrary, M. D., and M. O., Pierson. 2000. Influence of human activity on shorebird use in Ventura County, California. in Brown, D. R., K. L., Mitchell, H. W., Chang editors, Proceeding of the Fifth California Islands Symposium. Pages 424-427 (OCS Study, MMS 99-0038. US Minerals Management Service, Camarillo, CA. Nyblade, C. 1977. North Puget Sound Intertidal Study (U.W.). Department of Ecology. Baseline Study. Final Report. University of Washington. Friday Harbor Laboratories, 451 pp. Nyblade, C. 1978. Five Year Intertidal Community Change, San Juan Islands, 1974-1978 and The Intertidal Benthos of North Puget Sound, Summer 1978. University of Washington. Friday Harbor Laboratories, 137 pp. Stachowicz, J. J., H., Fried, R. W., Osman and R. B., Whitlatch. 2002. Biodiversity, invasion resistance, and marine ecosystem function: reconciling pattern and process. Ecology 83:2575-2590. Strathmann, M. F. 1987. Reproduction and Development of Marine Invertebrates of the Northern Pacific Coast. The University of Washington Press. Thomson, R. E. 1981. Oceanography of the British Columbia Coast. Canadian Special Publishing Fisheries and Aquatic Science p. 139-199. Yorio, P. 2001. Tourism and recreation at seabird breeding sites in Patagonia, Argentina: current concerns and future prospects. Bird Conservation International 11:231-245.
25 Table 1. Location, status, current flow level, approximate shoreline and distribution of intertidal sampling sites. Shoreline length is total including bedrock and beach habitats for all locations except Cattle Point, where only the shoreline along San Juan Channel, i.e., from parking lot access to southern tip of island, is listed. Shaw Island total includes both western and eastern sides of the park.
Location Designation Island Flow Shoreline No. Site (m) sites names Point Research San Low 4000 6 D-I Caution Reserve Juan High 5 A-C, J-K
Reuben County Park San Low 300 3 A-C Tarte Juan High 3 D-F
Shaw County Park Shaw Low 1600 3 A-C
Shark County Park Lopez High 500 3 A-C Reef
Third IAC San Low 600 3 A-C Lagoon designated Juan recreation area
Cattle National San Low 600 3 A-C Point Historical Park Juan High 3 D-F
Table 2. Sampling effort and shoreline length surveyed for human use.
Location No. observers Shoreline (m) Point Caution 3 1604 Reuben Tarte 1 348 Shaw 2 1299 Shark Reef 1 397 Third Lagoon 2 604 Cattle Point 1 597
26 Table 3. Sampling dates for intertidal diversity and abundance surveys.
Location Sampling dates Point Caution 7/27, 7/29, 7/31 Reuben Tarte 7/28 Third Lagoon 7/29 Cattle Point 7/30 Shark Reef 8/02 Shaw 8/03
Table 4. Shoreline areas surveyed for empty Nuttallia shells at each location.
Location Flow Point Caution Low High Reuben Tarte High Shaw Low Shark Reef High Third Lagoon Low Low Cattle Point High
27 Table 5. Human, dog, and boat abundance (number per linear meter of shoreline) at Point Caution vs. the mean and LCL, lower 95% confidence limit, UCL, upper 95% confidence limit, of the five public access sites. * indicates Point Caution abundance falls outside public access confidence interval for ln(x+1)-transformed data.
Public Access (n=5) Mean LCL UCL Point Caution Humans bedrock 0.100 -0.030 0.231 0.007 beach 0.105 0.028 0.183 0.002* total 0.206 0.002 0.409 0.009*
Dogs bedrock 0.003 -0.002 0.008 0.000 beach 0.002 -0.002 0.005 0.004 water 0.002 -0.002 0.005 0.000 total 0.006 -0.002 0.014 0.004
Boats motorized 0.154 -0.050 0.357 0.492* non-motorized 0.044 -0.002 0.091 0.004 total 0.198 -0.050 0.446 0.496*
28 Table 6. Linear regression analyses for barnacle species abundance (average percent cover and frequency of occurrence in proportion of quadrats) versus human abundance (total per m of bedrock shoreline) at all six locations. Regression slope, intercept, S.E., standard error, F, F-statistic, p, probability value, and R2 all based on ln(x+1)-transformed data, df = 31. p-values < 0.05 in bold.
Barnacles Slope S.E. Int S.E. F p R2 % cover All barnacles -0.053 0.237 0.445 0.032 0.051 0.823 0.002 Balanus glandula -0.246 0.167 0.268 0.023 2.167 0.151 0.067 Chthamalus dalli -0.395 0.167 0.182 0.023 5.567 0.025 0.157 Semibalanus cariosus 0.441 0.258 0.229 0.035 2.926 0.098 0.089
Frequency All barnacles 0.165 0.288 1.431 0.039 0.329 0.571 0.011 Balanus glandula -0.827 0.488 0.994 0.067 0.766 0.389 0.025 Chthamalus dalli -0.827 0.488 0.994 0.067 2.877 0.100 0.088 Semibalanus cariosus 1.059 0.382 0.894 0.052 7.671 0.010 0.204
29 Table 7. ANOVA results for the effects of location, flow, and location by flow interaction on the abundance of focal intertidal taxa. Analysis based on arcsin- squareroot transformed percent cover data (Fucus and barnacles) and ln (x+1) transformed number per quadrat (limpets). DF, degrees of freedom; SS, sum of squares; F, F ratio; p, probability. p-values <0.05 in bold.
Taxon Source DF SS F p Fucus gardneri Location 2 0.040 1.02 0.383 Flow 1 0.176 9.04 0.008 Location*Flow 2 0.140 3.59 0.050 All barnacles Location 2 0.118 2.74 0.093 Flow 1 0.047 2.17 0.159 Location*Flow 2 0.005 0.11 0.896 All limpets Location 2 6.014 2.81 0.088 Flow 1 0.001 0.00 0.977 Location*Flow 2 9.953 4.65 0.024 Semibalanus cariosus Location 2 0.068 1.22 0.320 Flow 1 0.062 2.21 0.156 Location*Flow 2 0.002 0.03 0.970 Balanus glandula Location 2 0.034 1.32 0.293 Flow 1 0.014 1.06 0.318 Location*Flow 2 0.019 0.75 0.486 Chthamalus dalli Location 2 0.120 7.08 0.006 Flow 1 0.006 0.67 0.424 Location*Flow 2 0.030 1.79 0.197 Lottia pelta Location 2 3.897 1.37 0.281 Flow 1 0.107 0.08 0.787 Location*Flow 2 1.741 0.61 0.554 Lottia digitalis Location 2 3.431 2.47 0.114 Flow 1 0.552 0.80 0.385 Location*Flow 2 3.616 2.61 0.103 Lottia paradigitalis Location 2 2.410 0.87 0.438 Flow 1 0.001 0.00 0.975 Location*Flow 2 11.521 4.15 0.034 Tectura scutum Location 2 0.480 0.76 0.483 Flow 1 0.239 0.76 0.396 Location*Flow 2 1.798 2.85 0.086 Onchidella borealis Location 2 0.002 0.59 0.564 Flow 1 0.000 0.22 0.643 Location*Flow 2 0.007 2.07 0.156
30 Table 8. Correlation coefficients for selected pairs of focal taxa, based arcsin- squareroot transformed percent cover data (Fucus and barnacles) and ln (x+1) transformed number of individuals per quadrat (limpets).
Fucus Semibalanus Balanus All limpets gardneri cariosus glandula All barnacles - 0.43 . . 0.03 Semibalanus cariosus - 0.29 . . . Balanus glandula - 0.04 - 0.28 . . Chthamalus dalli - 0.28 - 0.10 0.34 .
All limpets + 0.11 . . . Lottia pelta + 0.17 . . . L. digitalis + 0.07 . . . L. paradigitalis + 0.03 . . .
Table 9. Correlation coefficients for total limpet and total barnacle abundance vs. Fucus gardneri percent cover (mean ± 1 S.D.) across n = 13 years.
Correlation coefficients Location Intertidal N Fucus Limpets Barnacles zone % cover Reuben Tarte High 13 46.37 ± -0.46 -0.27 33.75 Med-High 13 41.14 ± -0.58 -0.63 16.47 Cantilever Point Med 13 31.55 ± 0.45 0.99 (Point Caution) 37.68
31 Table 10. Presence and mean abundance of three non-indigenous species, the Pacific oyster (Crassostrea gigas, no./m2), purple varnish clam (Nuttallia obscurata, no./m2), and Japanese brown macroalga (Sargassum muticum, no./m) at Point Caution vs. the mean, LCL, lower 95% confidence limit, and UCL, upper 95% confidence limit of the five public access locations. For public access, No. sites is number of sites at which species present; mean abundance based on n=5 sites (i.e. including zero values). * indicates Point Caution abundance falls outside public access confidence intervals for both untransformed data (shown here) and ln(x+1)-transformed data (not shown).
Public Access Species Flow No. sites present Mean LCL UCL Point Caution C. gigas high 3 0.01 -0.005 0.02 0.03* C. gigas low 4 0.11 -0.01 0.24 0.16 N. obscurata 2 0.05 -0.03 0.12 0.01 S. muticum 5 0.03 -0.01 0.06 0.36*
Table 11. Linear regression analyses for abundance of the Pacific oyster Crassostrea gigas (no. per m2) vs. larval abundance (no. per location) and taxon diversity (Jackknife 2 estimate), and taxon diversity vs. Sargassum muticum abundance across all six locations. Regression slope, intercept, and standard error, S.E., based on untransformed data; F, F-ratio, p, probability value, and R2 based on ln(x+1)-transformed data, df = 5.
Y x Slope S.E. Int S.E. F p R2 C. gigas Larvae -0.001 0.002 0.27 0.19 0.90 0.40 0.18 C. gigas Diversity -0.02 0.004 1.70 0.37 6.07 0.07 0.60 Diversity S. muticum 31.92 30.15 80.14 4.94 0.94 0.39 0.19
32 Table 12. Abundance of dominant larvae and total number of larval taxa collected at Point Caution vs. the mean and 95% lower (LCL) and upper (UCL) confidence limits five public access locations. * indicates Point Caution abundance falls outside the 95% confidence interval of the other five locations.
Public Access Reuben Third Shark Cattle Point Group Tarte Shaw Lagoon Reef Point Mean LCL UCL Caution Annelida Nereid-like 698 457 212 53 87 202 62 540 888* setigers Other (includes 12 13 17 2 17 12 7 18 17 trochophores) Mollusca Gastropod 40 8 28 5 13 14 6 32 71* veligers Bivalve veligers 18 210 35 11 33 72 -12 135 22 Arthropoda Barnacles 31 51 91 18 26 47 18 69 34 Platyhelminthes Juvenile 21 68 87 28 126 77 28 104 100 Bryozoa Cyphonautes 0 23 10 3 2 10 -1 16 0 Other 2 1 2 9 10 6 1 9 0
Total Abundance 821 831 482 129 314 439 244 787 1132* Total Taxa 8 8 11 10 12 10 8 11 7*
33 Table 13. Linear regression analyses for abundance of the Pacific oyster Crassostrea gigas (no. per m2) vs. bivalve larval abundance (no. per location), total barnacle percent cover and barnacle frequency (proportion of quadrats in which present) vs. barnacle larval abundance, and intertidal taxon diversity (Jackknife 2 estimate), vs. total larval abundance. Regression slope, intercept, and standard error, S.E., based on untransformed data; F, F-ratio, p, probability value, and R2 based on ln(x+1)-transformed data, df = 5. p<0.05 in bold. y x Intercept S.E. F p R2 Oysters Bivalve 0.01 0.02 15.35 <0.01 0.69 larvae Barnacle Barnacle 49.54 18.65 2.57 0.15 0.27 % cover larvae Barnacle Barnacle 0.94 0.11 0.03 0.88 <0.01 frequency larvae Diversity Total 70.77 8.92 0.05 0.82 0.01 larvae
Table 14. Number of bird groups and presence and abundance (no. per 100 m2) of total birds, crows and ravens, and gulls and terns at Point Caution vs. the mean and lower (LCL) and upper (UCL) 95% confidence limits of the five public access locations. No. locations, number of locations at which birds present; public access means based on n = 5 locations (i.e. including zero values). All Point Caution bird abundances fall inside public access confidence intervals for both untransformed data (shown here) and ln(x+1) transformed data (not shown).
Public access No. Category locations Mean LCL UCL Point Caution No. groups 3 2 0.87 3.13 2.00 Total birds 3 0.24 -0.08 0.57 0.08 Total crows and ravens 3 0.03 -0.02 0.08 0.04 Total gulls and terns 3 0.09 -0.05 0.23 0.00
Table 15. Linear regression analyses for total bird abundance (no./m2) vs. total human and total boat abundance (no./m shoreline), df = 5.
Disturbance factor Slope S.E. Int S.E. F p R2 Humans -1.98 6.01 1.92 1.62 0.11 0.76 0.03 Boats -3.55 4.43 2.45 1.58 0.64 0.47 0.14 34 Appendix
Raw data for human, bird, invader, and larval surveys. Intertidal quadrat raw data are available from Terrie Klinger and Marjorie Wonham
Appendix Table 1. Raw data from human use survey. Total is sum of 13 observations made at 15 minute intervals from 11:00am to 2:00pm.
Shoreline Resting Walking Other Grand Location Habitat (m) total total total total Point Caution Beach & cobble 524 0 0 1 1 Point Caution Bedrock 880 0 6 0 6
Rueben Tarte Beach & cobble 88 2 7 0 9 Shaw 1024 32 68 2 102 Shark Reef 74 3 7 0 10 Third Lagoon 132 0 0 0 0 Cattle Point 229 4 36 14 54
Rueben Tarte Bedrock 260 0 10 0 10 Shaw 275 0 0 0 0 Shark Reef 323 7 26 2 35 Third Lagoon 472 0 0 0 0 Cattle Point 368 64 60 7 131
35 Appendix Table 2. Raw data from bird survey by location and bird group. Totals include listed groups plus any additional birds that were observed.
Location Group Area (m2) Resting Feeding Total Point Caution crows & ravens 1 0 1 ducks 0 0 0 gulls & terns 0 0 0 herons 1 1 2 Total (including others) 2607 8 2 10
Reuben Tarte crows & ravens 14 6 20 ducks 0 0 0 gulls & terns 0 0 0 herons 0 0 0 Total (including others) 2414 14 6 20 Shaw crows & ravens 0 0 0 ducks 1 19 20 gulls & terns 4 2 6 herons 14 1 15 Total (including others) 2923 21 32 53 Shark Reef crows & ravens 0 1 1 ducks 0 0 0 gulls & terns 6 0 6 herons 0 0 0 Total (including others) 14119 9 1 10 Third Lagoon crows & ravens 10 3 13 ducks 19 7 26 gulls & terns 0 0 0 herons 0 3 3 Total (including others) 9413 29 15 44 Cattle Point crows & ravens 1 0 1 ducks 0 6 6 gulls & terns 6 0 6 herons 0 0 0 Total (including others) 6420 7 6 13
36 Appendix Table 3. Raw data from survey of non-native species, by location and flow. For Sargassum survey, total shoreline survey length also given.
Nuttallia obscurata Crassostrea gigas Sargassum muticum Location Flow Empty shells Total attached Total Survey thalli length (m) Point Caution High 0 188 Low 14 399 Total 14 587 697 1930
Rueben Tarte High 0 9 Low 0 3 Total 0 12 19 200 Shaw Low 13 1100 Total 13 1100 26 700 Shark Reef High 0 2 Total 0 2 0 367 Third Lagoon Low 238 568 Total 238 568 3 237 Cattle Point High 0 0 Low 0 30 Total 0 30 0 327
37 Appendix Table 4. Raw data from larval survey.
Platyhelminthe Phyla: s Bryozoa Annelida Crustacea Mollusca Total Other Nereid-like Other Crustacean Gastropod Bivalve Other All Location Tuffy Cyphonautes setigers Annelids Barnacles s veligers veligers Taxa Taxa Point Caution 1 18 0 194 0 6 0 10 2 0 230 2 43 0 214 5 9 0 12 11 0 294 3 14 0 248 0 2 0 17 2 0 283 4 13 0 89 8 1 0 8 3 0 122 5 0 0 39 0 8 0 7 1 0 55 6 12 0 104 4 8 0 17 3 0 148
Reuben Tarte 1 5 0 65 1 2 0 5 1 0 79 2 0 0 83 0 5 0 12 1 0 101 3 0 0 72 0 7 1 10 1 0 91 4 2 0 99 0 0 0 0 8 0 109 5 10 0 198 3 3 0 7 4 1 226 6 4 0 181 8 14 0 6 3 0 216 Shaw 1 1 0 94 4 13 0 0 46 0 158 2 1 10 90 1 7 0 1 53 0 163 3 14 2 76 0 3 1 1 18 0 115 4 42 11 104 0 14 0 3 48 0 222 5 2 0 54 5 9 0 0 9 0 79 6 8 0 39 3 5 0 3 36 0 94 Shark Reef 1 6 0 9 0 1 0 1 4 1 22 2 2 0 8 0 3 0 0 2 0 15 3 2 0 8 0 2 3 0 1 0 16 4 1 0 3 0 3 0 0 0 0 7 5 14 3 15 2 4 0 2 3 5 48 6 3 0 10 0 5 0 2 1 0 21 Third Lagoon 1 14 0 44 0 3 0 1 15 0 77 2 4 0 51 0 32 0 5 3 0 95 3 60 5 29 6 9 1 5 3 1 119 4 1 0 8 9 25 0 2 0 0 45 5 6 5 66 1 16 0 5 4 0 103 6 2 0 14 1 6 0 10 10 0 43 Cattle Point 1 18 0 11 6 3 0 0 1 0 39 2 2 0 6 5 4 1 1 0 0 19 3 12 0 12 0 2 0 1 1 0 28 4 12 0 12 0 7 0 2 7 0 40 5 31 2 33 6 4 0 4 12 9 101 6 51 0 13 0 6 0 5 12 0 87
38 Figure 1. San Juan Archipelago, showing locations sampled (boxes), and coarse patterns of surface circulation (blue arrows).
39 A) Point Caution
B) Shaw C) Reuben Tarte
D) Cattle Point E) Third Lagoon
F) Shark Reef (Lopez Island)
Figure 2. Aerial photos of locations sampled. Yellow lines and letters indicate intertidal sampling sites. Orange lines indicate locations of bird and human observations.
40 Figure 3. Schematic of human use survey design.
Figure 4. Schematic of intertidal diversity and abundance sampling design.
41 Figure 5. Schematic of Pacific oyster Crassostrea gigas survey design.
Figure 6. Schematic of Japanese alga Sargassum muticum survey design.
42 Figure 7. Schematic of larval collection sampling design. One larval collector was deployed at each location, which was given a general flow regime designation. Each collector consisted of three replicate units (TuffysTM) that were pooled for analysis.
Figure 8. Schematic of bird survey design.
43 100
90
80
70 3rd Lagoon 60 Lopez Reuben Tarte 50 Pt Caution 40 Cattle Point Shaw 30
Jack 2 spp richness estimate 20
10
0 0 50 100 150 200 250 300 samples
Figure 9. Intertidal taxon richness rarefaction curves for each location with high and low flow sites combined, using Jackknife-2 diversity estimates from EstimateS. Only Point Caution, Reuben Tarte, and Third Lagoon appear to reach an asymptote.
44 100 90 80 70 60 PtCautionHigh Cattle Point High 50 Lopez 40 Reuben Tarte High 30 20
Jack 2 spp richness estimate 10 0 0 50 100 150 200 samples
Figure 10. Intertidal taxon richness rarefaction curves for high flow locations only using Jackknife-2 diversity estimates from EstimateS. None of the curves appear to reach an asymptote.
45 100 90 80
70 3rd Lagoon 60 Shaw 50 Pt Caution Low 40 Reuben Tarte Low 30 Cattle Point Low 20 10 Jack 2 spp richness estimate 0 0 50 100 150 samples
Figure 11. Intertidal taxon richness rarefaction curves for low flow locations only using Jackknife-2 estimates from EstimateS. Cattle Point, Third Lagoon, and Reuben Tarte appear to reach an asymptote.
46 100 90 80 70 60 50 40 30 Species richness 20 10 0 Point Shaw Lopez Reuben Cattle Point Third Lagoon Caution Tarte Location
Figure 12. Observed (bars) and mean estimated (points ±1 S.D. from EstimateS) intertidal taxon richness.
47 100 90 80 70 60 50 40 Species richness 30 20 10 0 Lopez Point Caution Cattle Point Reuben Tarte Location
Figure 13. Observed (bars) and mean estimated (points ±1 S.D. from EstimateS) intertidal taxon richness for high flow locations only.
48 100 90 80 70 60 50 40 Species richness 30 20 10 0 Point Caution Cattle Point Reuben Tarte Shaw Third Lagoon Location
Figure 14. Observed (bars) and mean estimated (points ±1 S.D. from EstimateS) intertidal taxon richness for high flow locations only.
49 Average percent coverage of Fucus gardneri and barnacles per location
70
60
50
Fucus gardneri 40 Semibalanus cariosus Balanus glandula 30 Chthamalus dalli
20 Average percent coverage
10
0 Shaw Third Lagoon Lopez Reuben Tarte Pt Caution Cattle Pt Location
Figure 15. Mean total percent cover of Fucus gardneri and three barnacle species at all 6 locations.
50 Average percent coverage of Fucus gardneri and barnacles per location
70
60
50 Fucus gardneri Semibalanus cariosus 40 Balanus glandula Chthamalus dalli 30
20 Average percent coverage
10
0 Cattle Pt Lopez High Pt Caution Reuben Cattle Pt Pt Caution Reuben Shaw Low Third High High Tarte High Low Low Tarte Low Lagoon Low Location
Figure 16. Mean total percent cover of Fucus gardneri and three barnacle species at all 6 locations, separated by flow.
51 Average number of limpets per location
18
16
14
12 Lottia pelta 10 Lottia digitalis Lottia strigatella 8 Tectura scutum
per quadrat Onchidella borealis 6
Average number of individuals 4
2
0 Shaw Third Lagoon Lopez Reuben Tarte Pt Caution Cattle Pt Location
Figure 17. Mean number of limpets for all six locations.
52 Average number of limpets per location
16
14
12
10
Lottia pelta 8 Lottia digitalis Lottia strigatella per quadrat 6 Tectura scutum Ochidella borealis 4 Average number of individuals
2
0 Cattle Pt Lopez High Pt Caution Reuben Cattle Pt Pt Caution Reuben Shaw Low Third High High Tarte High Low Low Tarte Low Lagoon Low Location
Figure 18. Mean number of limpets for all six locations, separated by flow.
53 Location MDS Ordination
Stress: 0.18 PC E Reuben
CP F Pt Caution PC D LO BLO ALO CCP E PC I TL B CP C Shaw SH CCP D RT D PC C PC G CP B PC H CP A RT F SH A RTRT B C TL C PC K Third Lagoon TL A RT ERT A
PC J SH B PC A PC F Lopez
PC B Cattle Point
Figure 19. Multidimensional scaling (MDS) ordinations of intertidal sites based on community composition (similarity of species and frequency of occurrence). Lopez and Reuben Tarte sites are more tightly clustered than sites at other locations. Location abbreviations: PC, Point Caution, TL, Third Lagoon, SH, Shaw, CP, Cattle Point, LO, Shark Reef (Lopez Island), RT, Reuben Tarte.
54 MCB Class Project FHL 2004 - DIVERSITY
Stress: 0.17 PC B
PC F
PC A RT F RT C PC K PC C PC J RT E RT D PC H RT B RT A CP A TL A TL C SH B CP B SH A PC G LO B TL B SH C CP D LO C LO A CP F CP C PC I CP E PC D
PC E
Figure 20. MDS ordination of intertidal sites based on mean abundance of the articulated coralline algae functional group. Cattle Point site B shows the highest frequency of occurrence. Location abbreviations as in Figure 19.
55 MCB Class Project FHL 2004 - DIVERSITY
Stress: 0.17 PC B
PC F
PC A RT F RT C PC K PC C PC J RT E RT D PC H RT B RT A CP A TL A TL C SH B CP B SH A PC G LO B TL B SH C CP D LO C LO A CP F CP C PC I CP E PC D
PC E
Figure 21. MDS ordination of intertidal sites based on the abundance of the predator functional group. Location abbreviations as in Figure 19.
56 MCB Class Project FHL 2004 - DIVERSITY MCB Class Project FHL 2004 - DIVERSITY A B Stress: 0.17 Stress: 0.17 PC B PC B
PC F PC F
PC A RT F RT C PC A RT F RT C PC K PC C PC K PC C PC J RT E PC J RT E RT D PC H RT D PC H RT B RT B RT A CP A RT A CP A TL A SH B TL A TL C SH B CP B TL C CP B SH A SH A PC G LO B PC G LO B TL B TL B SH C SH C CP D LO C CP D LO C LO A CP F LO A CP F CP C CP C PC I CP E PC I CP E PC D PC D
PC E PC E MCB Class Project FHL 2004 - DIVERSITY C D Stress: 0.17 PC B
PC F
PC A RT F RT C PC K PC C PC J RT E RT D PC H RT B RT A CP A TL A TL C SH B CP B SH A PC G LO B TL B SH C CP D LO C LO A CP F CP C PC I CP E PC D MCB Class Project FHL 2004 - DIVERSITY PC E
Stress: 0.17 PC B
PC F
PC A RT F RT C PC K PC C PC J RT E RT D PC H RT B RT A CP A TL A TL C SH B CP B SH A PC G LO B TL B SH C CP D LO C LO A CP F CP C PC I CP E PC D
PC E
Figure 22. nMDS ordination of intertidal sites based on functional group (A) canopy algae, (B) turf algae, (C) grazers and (D) crustose algae. Sites are clustered based on the similarity of the species and their frequency of occurrence across functional groups. Location abbreviations as in Figure 19.
57 MCB Class Project FHL 2004 - DIVERSITY
PC I TL B PC G SH A TL C PC C PC K SH C PC A CP D PC H CP C CP F CP E LO C LO A LO B RT E RT B RT A RT F RT C RT D PC J CP A TL A SH B PC D PC F PC B CP B PC E 60 70 80 90 100
Figure 23. Cluster analysis of intertidal sites based on community composition. We obtain three main groups: A (from PC-ISimilarity to LO-B), B (from RT-E to SH-B) and C (from PC-D to PC-E); similarity among sites within groups is significant, ANOSIM test value R=0.553, p<0.01. Site abbreviations: PC, Point Caution, TL, Third Lagoon, SH, Shaw, CP, Cattle Point, LO, Shark Reef (Lopez Island), RT, Reuben Tarte.
58 A)
Fucus (high intertidal) low flow
120
100
80
60
% Cover 40
20
0
1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Years
B)
Fucus (med-high intertidal) low flow
120
100
80
60
% Cover 40
20
0
1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Year
Figure 24. Mean (± 1 S.D.) percent cover of Fucus gardneri at Reuben Tarte A) high and B) mid-high intertidal over time. Source: 1989-2003 Zoo/Bot Class Project, 2004 present study.
59 A) Barnacles (high intertidal) low flow
70 60 50 40 30 % Cover 20 10 0
1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Year
B)
Barnacles (med-high intertidal) low flow
70 60 50 40 30 % Cover 20 10 0
1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Year
Figure 25. Mean (± 1 S.D.) percent cover of barnacles at Reuben Tarte A) high and B) mid-high intertidal over time. Source: 1989-2003 Zoo/Bot Class Project, 2004 present study.
60 A) Limpets (high intertidal) low flow
180 160 140 2 120 100 80 60 N/0.25 m 40 20 0
19891990 19911992 199319941995 199619971998 19992000 200120022003 20042005 Year B) Limpets (med-high intertidal) low flow
180 160 140 2 120 100 80 60 N/0.25 m 40 20 0
1989 1990 19911992 1993 1994 1995 1996 19971998 1999 2000 2001 20022003 2004 2005 Year Figure 26. Mean (± 1 S.D.) abundance of limpets at Reuben Tarte A) high and B) mid-high intertidal over time. Source: 1989-2003 Zoo/Bot Class Project, 2004 present study.
61 Fucus low flow
140
120
100
80
60 % Cover 40
20
0 0 1 2 3 4 5 6 7 8 Sep 74 Jul 75 Sep 75 Jul 76 Sep 76 Aug 77 Aug 78 Aug 04 Sep 74 Jul 75 Sep 75 Jul 76 Sep 76 Aug 77 Aug 78 Aug 04 Time
Figure 27. Mean (± 1 S.D.) Fucus gardneri percent cover at Cantilever Point on Point Caution over time. Source: 1974-1978 Nyblade (1977, 1978), 2004 present study. Original biomass from Nyblade was converted into percent cover using a correction factor (Appendix I).
Balanus low flow
100 90 80 70 60 50 40 % Cover 30 20 10 0 0 1 2 3 4 5 6 7 8 Sep 74 Jul 75 Sep 75 Jul 76 Sep 76 Aug 77 Aug 78 Aug 04 Sep 74 Jul 75 Sep 75 Jul 76 Sep 76 Aug 77 Aug 78 Aug 04 Time
Figure 28. Mean (± 1 S.D.) Balanus glandula percent cover at Cantilever Point on Point Caution over time. Source: 1974-1978 Nyblade (1977, 1978), 2004 present study. Original counts from Nyblade were converted to percent cover using a correction factor (Appendix I).
62 Limpets low flow
1200
1000
800 2
600
N/ 0.25 m 400
200
0 0 1 2 3 4 5 6 7 8 Sep 74 Jul 75 Sep 75 Jul 76 Sep 76 Aug 77 Aug 78 Aug 04 Sep 74 Jul 75 Sep 75 Jul 76 Sep 76 Aug 77 Aug 78 Aug 04 Years
Figure 29. Mean (± 1 S.D.) limpet abundance at Cantilever Point on Point Caution over time. Source: 1974-1978 Nyblade (1977, 1978), 2004 present study.
63 100% 90% 80% Other 70% Bryozoans 60% Other Annelids 50% Gastropods 40% Bivalves 30% 20% Barnacles 10% Flatworms 0% Nereid-like setigers Reuben Shaw Third Lopez Cattle Point Point Tarte Lagoon Caution
Figure 30. Distribution of relative larval abundances at all six locations.
64 a)
b)
c)
Figure 31. Multidimensional scaling (MDS) ordinations of larval abundance by A) location, B) status, and C) flow. Location abbreviations as in Figure 19; numbers refer to TuffyTM numbers 1-6 at each location.
65 A B
100 0.30 0.20 50 0.10 Taxon 0 Oyster 0.00 Richness 0 500 1000 1500 Abundance 0 100 200 300 Total Larvae Bivalve Larvae
C D
40 1.05 1.00 20 0.95 0.90
Barnacle 0 0.85 Barnacle Frequency
Percent Cover 0 50 100 0 50 100 Barnacle Larvae Barnacle Larvae
Figure 32. Linear regression of A) intertidal taxon richness (Jack-2 estimator) vs. total larval abundance (total per location), B) oyster abundance (number per m2) vs. bivalve larval abundance, C) percent barnacle cover vs. barnacle larval abundance, and D) banacle frequency (proportion of quadrats in which present) vs. barnacle larval abundance. N = 6 locations for all.
66