Shelby Kawana

Shelby Kawana

Bio161

Total= 4+20+30+

Lit Cited = 4

[4] The Effect of Swell Exposure on Species Community Structure in Two Central California Kelp Forests

Abstract: [20]

Species community composition was studied in two central California kelp forests with contrasting physical environments. Such spatial comparisons can provide insight into possible drivers of species distribution and abundances. The scientificOur approach was to quantitatively survey species composition of fishes, inverts and algae in the two kelp beds over a two-day period. The analyses conducted on the data[better to describe the analyses.. A PREMANOVA… identified the effects of site location, survey day, and the interaction of both location and day on species composition. The analyses indicated an overall difference in species composition at sites where algae and invertebrate species had the greatest site difference. Fish species significantly differed because of survey day and the interaction of site and day. From theseOur results we can assumesuggest that the main driver of species community structure in these two kelp forests is greatly due to ocean swell exposure.

Introduction: [2, 2, 2, 4, 3, 3, 4, 0, 4, 2, 4] 30

Comparisons of spatially different kelp forests provide valuable information of species composition and structure. A main goal of ecology is to understand patterns of species distribution, abundance, and what factors influence such communities (Watanabe, 1984). Many spatial comparison studies have been conducted on species distribution due to factors including El Niño events (Edwards, 2003), predation-causing trophic cascades (Estes et.al, 1998), and other ecosystem disturbances. One possible influence on species composition in kelp forestsis exposure to physical disturbances, such as swell. The intent objective of this research is to understand species community structure in protected versus exposed kelp forests. Quantitative scientific surveys identifying species of algae, fish, and invertebrates were conducted at two spatially different kelp forests. Surveys were conducted over two days to account for daily differences at the site. The specific questions that were addressed in this study were:

1) Is there an overall difference in species composition between sites and do these differences vary by species of algae, fish and invertebrates?

2) Is there a difference in species composition between days and do these differences vary by species of algae, fish and invertebrates?

3) Does both the interaction of site and sampling day affect species composition and does this vary by species of algae, fish, and invertebrates?

Answering these questions will provide insight on how exposure to ocean conditions and other possible factors impact community composition in kelp forests.

Methods: [2, 2, 4, 3, 0, 2, 2, 2, 3, 3, 1, 2, 0, 3, 2, 3, 2, 3] 38

Study Sites

The kelp forests studied were located at two sites in Monterey County, California: Hopkins Marine Reserve (Hopkins, 3637.15N, 12154.15W) and Whaler’s Cove, inside Point Lobos State Reserve (Lobos, 3631’10’’ N 12156.45W). Hopkins is positioned at the south end of Monterey approximately 18 miles North of Lobos, located along the south perimeter of Carmel Bay (Figure. 1).Both sites are marine reserves and therefore are not impacted by fishing pressure. Both locations endure prevailing swells and surge from the northwest for most of the year, however, Hopkins is protected by Point Pinos and experiences little disturbance (Breda and Foster,1985). Lobos is northwest facing and has little to no protection from the northwest swell. The kelp forest surface canopies at both sites are composed of Macrocystis pyrifera, however other primary species are known to differ at each site. Hopkins’ substratum is composed mainly of high-relief granite rock and medium sized boulders interspersed with sand (Gerard, 1976). Lobos has a similar substratum, however boulders tend to be large and vertically steep.

General Approach

Dive teams of 14 divers (7 pairs) conducted quantitative surveys at approximately 8:50 am to 10:50 am at both sites on October 11th and October 13th 2011. Dive pairs at Hopkins were assigned one meter mark along the permanent cable to perform two transects, the first being offshore and the second being onshore. Dive pairs at Point Lobos were assigned two meter marks along an implanted cable (deployed that day) to perform two transects, both in the same direction at relatively the same depth. All transects were 30x2 meters for surveying algae and invertebrates and 30x2x2 meter (volume) for surveying fish. Divers quantitatively counted species encountered along each transect, and recorded data on the predetermined data sheets. Species on the data sheets were selected based on previous observations and studies and divided into three different taxa: algae, fish, and invertebrates (Table 1). Species represented on the data sheets differed in mobility, size, and abundance in order to identify the effects of swell exposure on a variety of characteristics.

Is there an overall difference in species composition?

To identify differences of all species based on site and day, a Multi-Dimensional Scaling (MDS, 2-D stress:0.18) plot was constructed. The MDS plot maps each transect according to similarity or difference against day and site (the shorter the distance between two transects the more similar). MDS plots (2-D stress:<.2) characterize true multidimensional truth community structure and allow us to identify significant differences in species composition due to site, day, or both. And the PERMANOVA???

Is there a difference in algae assemblages? [if you divide this up by taxa, good to describe the sampling methods for each taxon here.]

To examine the algae assemblage difference at sites, day, or both site and day, an MDS plot (2-D stress:0.11) was constructed, clearly illustrating similarities in transect data. To identify which species of algae drove the assemblage a Univariate univariate species-specific analysis was conducted [what was that?]. In addition, Permutational MANOVA (PERMANOVA) analysis was performed on the data to identify the statistical significance of site, survey day, or the interaction of both on algae assemblage. [yu need to explain what piece of the PERMANOVA was used to test site effects, day effects and the interaction.]

Is there a difference in fish composition?

To identify true differences in fish collaborations between Hopkins and Lobos, survey day, or both, the same statistical analyses were used as for algae assemblages. MDS plot (2-D stress: 0.14), Univariate species-specific analysis, and PERMANOVA statistics.

Is there a difference in invertebrate associations?

Invertebrate associations were also analyzed using the same methods: MDS plot (2-D stress 0.18), Univariate species-specific analysis, and PERMANOVA statistics.

Overall Study Power and Logistics

A species power index (PI) allowed our team to test the overall power of the study design, where x is the mean, N is the number of transects, and sd is the standard deviation:

PI = ¯x√N/sd.

PI values that are larger (>2) have greatest power, least variation, and need the least amount of replicates when sampling. The PI for each taxa were plotted against the others to find out which taxa were the “best fit” for the amount of transects performed in this study. To identify any trends in species power, a PI for each species within algae, fish, and invertebrate assemblages was performed.

Lastly, to account for different depths of main cable and transects at each site, a box plot was assembled to analyze this effect on study error.

Results:

Is there an overall difference in species composition?

We found a significant effect of site on overall species composition (Fig.2, PERMANOVA: site effect, P=0.001).

Is there a difference in algae assemblage?

We observed a strong effect of site on species composition of the algae assemblage (Fig. 3, PERMANOVA: site effect, P=0.001). The species that drove this assemblage were Chondracanthus corymbifera and Cystoseira osmundacea, highly encountered at Hopkins but rarely found at Lobos, as well as Pterygophora californica and Eisenia arborea which were the main algae encountered at Lobos but infrequently found at Hopkins (Fig. 4).

Is there a difference in fish composition?

We observed a significant difference in fish species composition between survey days (Fig.5, PERMANOVA: day effect, P=0.043). The main fish species that drove this divergence was the kelp rockfish (Sebastes atrovirens) (Fig.6), which was more highly encountered on day 1 than day 2. The strongest difference in fish species composition was found at the interaction of both site and day (Fig.5, PERMANOVA: interaction effect, P=0.015). The striped surfperch (Embiotoca lateralis) and the black surfperch (Embiotoca jacksoni) abundance differed the most due to interaction of site and day (Fig.6).

Is there a difference in invertebrate associations?

We found a strong difference in invertebrate associations at Hopkins and Lobos (Fig.7, PERMANOVA: site effect, P=0.001). The invertebrate that largely drove this variation was the orange cup coral (Balanophillia elegans), which was encountered more frequently at Hopkins compared to Lobos (Fig.8).

Overall Study Power and Logistics

We found that the number of transects completed was sufficient for algae (see asymptote, Fig.9). Algae species that were most powerful and “best fit” for this study were Macrocystis pyrifera, Cystoseira osmundacea, and Pterygophora californica, respectively (Fig.10).

We found that more transects are needed to obtain sufficient study power for fish assemblage difference. Fish species that appeared to be the “best fit” for this study method were Sebastes atrovirens, Embiotoca lateralis, and the kelp greenling (Hexagrammos decagrammus)(Fig.11).

We also found that more transects on invertebrate composition are needed to achieve sufficient study power. However, invertebrates that were the best fit for this study so far were the bat star (Patiria miniata), the white spotted rose anemone (Tethya aurantia), and the fish-eating anemone (Urticina piscovora) (Fig.12).

Lastly, we found that the depth difference in transects at Hopkins and Lobos was not great enough to produce significant error (Fig.13).

Discussion:

Swell exposuremay be a major factor in the difference of species composition between Hopkins and Lobos. Compared to Hopkins, Lobos experiences more swell exposure throughout the year, which may explain why sturdy and thick stiped subcanopy algae such as Pterygophora californica and Eisenia arborea were primarily found at Point Lobos.

Differences in species composition on survey day were observed in fish assemblages. This may be due to the difference in ocean conditions between survey days. Data from the Monterey buoy (station 46042) on October 11th from 8:50-10:50 am recorded average wave height of approximately 5.36 feet at a period of 11 seconds out of the northwest. Buoy data on October 13th from 8-50-10:50 am averaged at 9.84 feet at a period of 14 seconds out of the northwest (NOAA). The occurrence of increased swell size on day 2 may be a reason for decreased fish sightings. For instance, rockfish are less active during severe weather (Quast, 1968), and were rarely observed in the water column on day 2. Algae and invertebrate species are usually sessile or have limited mobility and therefore showed no difference in composition between days. The increased swell size on day 2 also affected divers performing surveys, especially at Lobos. Divers experienced powerful surge, limited visibility, and unfavorable survey conditions, which may have affected survey accuracy.

From these study findings we are able to gain insight on how to adjust and modify our final survey design. More transects are needed to observe adequate differences in fish and invertebrate species composition. Fish surveys will be of greatest benefit when conducted on days where ocean conditions are calm. Further studies on the impact of ocean conditions on fish behavior should be considered for the purpose of optimizing survey methods. Species that were the “best fit” include Macrocystis pyrifera, Sebastes atrovirens, and Patiria miniata, all of which were very abundant and the least variable at both sites. Species that are very abundant but highly variable may skew data and should not be considered in the final study, such as Balanophillia elegans. Balanophillia elegans is also very difficult to quantitatively count because of its tendency to exist at high concentrations.

Literature Cited:

Breda, V.A. and M.S. Foster.,M.S. 1985. Composition, abundance, and phenology of foliose red

algae associated with two central California kelp forests. Biol. Ecol., [??????] 94: pp. 115- 130.

Edwards, M.S. 2004. Estimating scale-dependency in disturbance impacts: El Niños

and giant kelp forests in the northeast Pacific. Oecologia. 138: pp. 436–447.

Estes, J.A., M.T. Tinker, T.M. Williams, and D.F. Doak. 1998. Killer Whale Predation on SeaOtters Linking Oceanic andNearshore Ecosystems. Science. 282: pp. 483-486

Gerard, V. 1976. Some aspects of material dynamics and energy flow in a kelp forest in Monterey Bay, California. Ph.D. dissertation, Stanford University, 173 pp.

Positive Interactions Along an Exposure Gradient: a look at the effects of spatial and temporal variability of the kelp canopy on community structur

Positive Interactions Along an Exposure Gradient: a look at the effects of spatial and temporal variability of the kelp canopy on community structure

Positive Interactions Along an Exposure Gradient: a look at the effects of spatial and temporal variability of the kelp canopy on communit strNDBC - Station 46042. National Data Buoy Center. NOAA. Web. 21 Oct. 2011. <

Quast, J.C. 1968. Fish fauna of the rocky inshore. pp35-79. In : W.J. North and C.L. Hubbs (ed.) Utilization of kelp-bed resources in southern California, California department of Fish and Game, Fish Bulletin. pp. 1-164.

Watanabe, J.M. 1984. The Influence of Recruitment, Competition, and Benthic Predation on SpatialDistributions of Three Species of Kelp Forest Gastropods (Trochidae: Tegula). Ecology, Vol. 65, No. 3. (Jun., 1984), pp. 920-936.

Figures and Tables:

Table 1: All species separated by taxa that were included on the data sheet.

Figure 1: Map of Monterey County coastline including both study sites (in red).

Figure 2: MDS plot showing relatedness for all species, where each point represents a transect, numbers above each point indicate survey day, and different colors code for each location (see legend).

Figure 3: MDS plot for all algae species. The close clumping of transects indicates similarity, which is easily observable at site.

Figure 4: Algae species differences by site and day; easily observable differences by site.

Figure 5: MDS plot for fish species is more spread out with substantial number overlap, displaying an interaction effect of day and site.

Figure 6: Univariate analysis fish species composition plotted against site and sample day.

Figure 7: MDS plot of invertebrate species illustrating a strong effect of site on the assemblage.

Figure 8: Invertebrate species plotted against site and survey day. Displays strong differences at site.

Figure 9: The power index of each taxa displays an informational line graph. Algae is the only line which asymptotes indicating that the number of transects completed were sufficient for this study.

Figure 10: Power Index for individual algae species.

Figure 11: Power Index of fish species.

Figure 12: Power Index of invertebrate species.

Figure 13: The normal depth distributions are about the same for both sites.