Pete Raimondi, Mark Carr

Sertic 1

Maya Sertic

Kelp Forest Ecology

October 18, 2011

The Effects of Site Exposure on Algal, Invertebrate, and Fish Communities at Point Lobos and Hopkins

Marine Sanctuaries

Abstract

Many of the current theories shaping our understanding of marine ecology were born out of spatial comparisons between different sites within a given ecosystem. We were interested in evaluating the effects of turbulence on kelp forest communities within Macrocystis-dominated kelp forests found in central California. We compared 2 sites, Hopkins and Point Lobos, which are similar in most abiotic traits except for their relative exposure to the ocean. While Hopkins is known to be a site unusually well protected from disturbances in the open ocean, Point Lobos is more exposed to turbulent winter storms.

To compare the effects that differences in exposure to the ocean have on kelp forest communities, we compared the species compositions of Hopkins and Point Lobos with respect to site and day by quantitatively collecting abundance data for 29 species along transects. We found that the species compositions for algae and invertebrates varied by site, while the species composition for fish showed greater variance between different sampling days due to their greater mobility. Fish abundance was also the only category which showed an interaction between site and day. We conclude that exposure to the open ocean does influence the species assemblage at a given site, but that different taxa react to turbulence on different time scales.

Introduction

In trying to detect patterns in nature, ecologists have identified and defined different ecosystems based on the specific biotic and abiotic factors that characterize them. While differences between ecosystems are generally well-defined because their unique traits are used to describe them, differences Sertic 2 within ecosystems are variable and not well defined. It is these differences within ecosystems that researchers study in order to test their hypotheses about different ecological patterns.

Many of the current theories shaping our understanding of marine ecology were born out of spatial comparisons between different sites within a given ecosystem. Kelp forests in particular have been used in many studies using spatial comparisons. A comparison of coves inhabited by sea otters and uninhabited by sea otters in the Aleutian Islands helped develop the theory of keystone predators and top- down trophic interactions (Duggins 1980). A comparison of coves exposed to and protected from killer whales in the Aleutian islands led to the understanding that transient species can play a key role in community structure (Estes et al. 1998). A comparison of 90 sites from Baja California to Central

California revealed that large disturbances, such as El Nino, cause a shift in the factors controlling kelp abundance from within-site local factors to large-scale regional factors (Edwards 2004). A comparison of

MPAs and fishing grounds around Tasmania suggested that large individuals in a population fulfill roles in community structure that smaller individuals cannot (Ling et al. 2009). These studies along with many others have helped marine scientists identify patterns in kelp forest ecosystems, which has led to a better understanding of community structure and function within kelp forests.

We were interested in the effects that exposure to the open ocean has on community composition in central California kelp forests. Water turbidity is known to shape kelp forests in different regions along the California coast. In relatively calm waters in Central and Southern California, Macrocystis is the prominent canopy-forming alga. This kelp is fast-growing and forms a thick canopy that shades out and can inhibit the growth of other algal species (Reed and Foster 1984). However, it is sensitive to turbulence, and dislodges during more severe winter storms. In northern California, the severity of winter storms limits the distribution of Macrocystis. (Dayton et al. 1984). We were interested in evaluating the effects of turbulence on kelp forest communities within Macrocystis-dominated kelp forests found in central California.

We compared 2 sites, Hopkins and Point Lobos, which are similar in most abiotic traits except that, while Hopkins is known to be a site unusually well protected from disturbances in the open ocean, Sertic 3

Point Lobos is more exposed (although this has not been directly tested). To compare the effects that differences in exposure to the ocean have on kelp forest communities, we compared the species compositions of Hopkins and Point Lobos with respect to the following questions: 1) Is there a difference in species composition between Hopkins and Point Lobos? 2) Is there a difference in species composition from day to day for either site? 3) Is there an interaction effect between site and day? To answer these questions, we quantitatively collected abundance data for 29 species at both sites on 2 days.

Methods

To study the differences in species composition at Hopkins and Point Lobos, we did a quantitative observational study, in which we counted the number of individuals for 9 fish species, 7 algal species, and 13 invertebrate species along transects (fig. 1).

We sampled abundances for the same 29 fish, algae, and invertebrate species at both Hopkins and

Point Lobos. Different species were chosen for different reasons. Most of the species we chose to sample are considered characteristic of central Californian kelp forests. We chose some species because they are known to occur at Point Lobos but are not characteristic of the central coast (such as Eisenia). More importantly, we wanted to have a diverse group of sessile and motile species, large and small species, as well as species whose life histories represent open and closed populations. A diverse group of species can help us expand our analysis to include organisms that were not studied but function in a similar way to those that were studied.

Study Sites

Hopkins Marine Station is located at the east end of Lovers Point Marine Reserve and faces east into the Monterey Bay. We did our sampling at the far east end of the marine station, just beyond the offshore rocky outcrop. This area is well protected from the wave action of the open ocean. The water temperature was 54°F on both days.

We collected our composition data for Point Lobos at the mouth of Whaler’s Cove, a north-facing cove at the southern edge of Carmel Bay, 10 miles south of Hopkins (fig. 2, SIMoN). The cove itself is highly protected from the ocean (Lovejoy 1996), while the mouth of the cove (often referred to as middle Sertic 4 reef) is more exposed to the ocean. The water temperature was 51°F on both days; it is typical for the water temperature at Point Lobos to be cooler than at Hopkins (Raimondi, pers. comm.).

Otherwise, these two sites are similar to one another. At both sites, the substrate is composed of granite outcrops and boulders interspersed with sandy patches (Paddock and Estes 2000). Both sites are no-take zones in marine protected areas, which means that the species compositions at the sites are not affected by fisheries.

Are there differences in species composition and abundance by site?

We expected that differences in site exposure would lead to variation in species composition between sites. To test this hypothesis, we collected species abundance data along 30m transects. At each site, the transects were laid out parallel to one another and perpendicular to a main transect running roughly from north to south. At Hopkins, we laid out seven 30m transects off the main cable at 90° and seven at 270°. The transects were 10m apart from one another. At Point Lobos, we sampled along 14 transects set 5m apart from each other, all pointing 90°. We ensured that the variation in transect placement at the two sites did not affect our data by comparing the depth profiles of our dives. Although our transects spanned a greater total distance from east to west at Hopkins (60m) than at Point Lobos

(30m), the depth gradients at both sites were not steep, creating a similar depth profile for the 2 sites (fig.

At both sites, we surveyed the most motile organisms, fish, while reeling out the meter tape to avoid disturbing them and potentially affecting our data collection. Each diver counted fish in a 1m wide by 2m high by 2m long volume of water. Each fish was counted only once, regardless of whether it travelled between buddies’ volume parameters. We counted invertebrates and algae in a 1m swath as we returned to the main cable. We counted the number of stipes for each Macrocystis pyrifera plant in our swaths.

We used permanovas to test whether there was a real difference in species composition between sites. The permanovas were then 4th root transformed to obtain information about percent dissimilarity between sites and the contributions of each species to the dissimilarity. We used permanovas to analyze Sertic 5 the differences between sites due to all species combined as well as for each taxon individually (algae, invertebrates, and fish).

Are there differences within each site from day to day?

We expected not to find significant differences in species composition at each site on the 2 days sampled because of the short time period in between the 2 sampling days. We hypothesized that any variation in species composition with respect to time would be due to differences in fish composition because fish are far more mobile than any of the other species we sampled.

To control for variation in species composition from day to day, we sampled on 2 days, October

11 and October 13, 2011, using the sampling methods described above. We chose to sample in October, when the kelp forests have had a full summer to regrow from the previous winter’s storms, but before the onset of this year’s storms. Thus, the two sites should be the most similar at this time of year. While the first sampling day was calm and overcast, the second day was sunny with large swell. We used permanovas and their transformations (described above) for all species combined and for each taxon to analyze the differences within sites between days. We also used Variance Components Analysis to assess the relative contributions of 2 potential sources of variance, site and day, to our estimates of fish, algae, and invertebrate abundance.

Is there an interaction between site and day?

We hypothesized that we may find an interaction between site and day for motile organisms such as fish (mostly affected by fish). To answer this question we analyzed the same permanova as above for an interaction between site and day effects. We also tested for an interaction between site and day for each individual taxon.

Results

The total dissimilarity between Hopkins and Point Lobos was 73%. Overall, we found a strong difference between sites, and no difference within sites between days, but when we separated out analyses by taxa, we found that fish actually varied by day rather than by site. Reference your results here.

Differences in species composition by site Sertic 6

For all species combined, there was a strong effect of site on species composition (Fig. 4, permanova: site effect, P=0.001). However, only algae and invertebrates strongly contributed to the difference between sites. Balanophyllia elegans c’s contributedion to the differences between sites was by far the strongest (31.54%), followed by Pterygophora californica (12.34%).

We found a strong effect of site on the species composition of the algal assemblage (Fig. 5, permanova: site effect, P=0.001). While Pterygophora was the most common algae found at Point Lobos, it was absent at Hopkins, which made its contribution to differences in algae assemblage the strongest

(29.43%). Similarly, Eisenia was only found at Point Lobos, although it did not contribute strongly to the difference between sites (8.22%), likely because it was not very common at Point Lobos. At Hopkins,

Chondracanthus corymbifera had the highest abundance, and both Dictyoneurum and Dictyoneuropsis were present, but these species were rare or absent at Point Lobos (reference). Macrocystis, which formed the kelp canopy at both sites, was the only algae with similar abundances at both sites (Fig. 6). However, individual Macrocystis plants at Hopkins had more stipes than plants at Point Lobos (Fig 7, Permanova: site effect, P=0.000022).

There was also a difference in invertebrate composition between the 2 sites (Permanova: site effect, P=0.001). Similar species assemblages were seen at both sites, but their abundances differed between sites. Balanophylli.a elegans and Asterina miniata were the most abundant species in both sites, but there were many more B. elegans Balanophyllia individuals at Hopkins than there were at Point

Lobos. Pachycerianthus fimbriatus was only seen at Hopkins, and Urticina lofotensis was only seen at

Point Lobos (Fig. 8).

Fish composition did not vary by site (Fig. 9, Permanova: site effect, P=0.319). On average, less than 0.5 individuals of any species were seen on each transect, suggesting very low fish densities. Kelp rockfish (Sebastes atrovirens) were the most common fish seen at each site, while gopher rockfish

(Sebastes carnatus) and black and yellow rockfish (Sebastes chrysolmelas) were rare at both sites (Fig.

Differences in species composition by day Sertic 7

For all species combined, there was no effect of day on species composition at either site (Fig. 4, permanova: day effect, P=0.382). An evaluation of each taxon individually shows that all of the variance in algae and invertebrate composition is explained by differences in site. However, a higher percent of the variance in fish composition is explained by day than by site (Fig. 11). While algae and invertebrates did not vary by sampling day (Algae: Permanova: P=0.724, Invertebrates: Permanova: P=0.505), fish composition did vary by sampling day ( Fish: permanova: P=0.043). More importantly there was an interaction with site…so you cannot conclude from that result that it differed by day There were a lot fewer fish seen at either site on the second day than on the first day, although this difference was especially apparent at Point Lobos (Fig. 10).

Was there a species interaction by site and day?

Overall, there was no interaction between site and day for all species combined. There was also no species interaction between site and day for algae (algae permanova: site by day, P=0.926) or invertebrates (invertebrate permanova: site by day, P=0.569). There was, however, an interaction between site and day for fish composition (fish permanova: site by day, P=0.015).

Discussion

Although we did not directly test the exposure of the two sites to the open ocean, our results and observations strongly suggest that Point Lobos is in fact more exposed than Hopkins. This is somewhat backwards….you selected the sites based on differences in exposure or some spatial difference. Now you want to know if communities vary between those sites. Whaler’s Cove is unprotected from the north, making it exposed to the swells that commonly come from the north-west. The cooler water temperature is likely due to greater water movement, and mixing of the cold bottom temperatures with the surface water. Our observation that Macrocystis plant at Point Lobos have fewer stipes on average suggests that the plants are ripped out more often, and therefore smaller in size. Finally, an observational comparison of swell at Point Lobos and at Hopkins on the second sampling day made it very clear that Point Lobos was less protected from ocean turbulence than Hopkins (although the storm that occurred on October 12 was not strong enough itself to rip out Macrocystis plants between the 2 sampling days). Sertic 8

There were other species that varied among sites that you discussed in the results, but never talk about in the discussion. Everything should be linked and have a point for being in the paper.

Wave exposure does impact community structure in a kelp forest, but it doesn’t impact all taxa equally. There were differences in species compositions of sessile invertebrates and algae between the sites, but these differences in composition did not vary from day to day, suggesting that wave exposure impacts their abundances over a larger time scale. However, fish composition, and abundance especially, did vary from day to day, showing that fish are affected by environmental conditions on a much shorter time scale. We suggest that turbulent conditions cause fish to go into hiding, and thus, fewer fish are seen in the open along transects

The variation in fish also led us to wonder whether our sample size was large enough to accurately depict the fish communities at the 2 sites. A comparison of power indices showed that our statistical analyses for many of the fish species sampled were not powerful (Fig. 12), and that we had not yet reached the ideal sample size for accurately analyzing fish abundance (Fig. 13). The same number of transects was a large enough sample size for algae as well as for most invertebrates, because there was a greater abundance of individuals in these taxa and there was lower variation in their distributions. This is important because it suggests that algae and invertebrates are better candidates for preliminary site comparisons, because they require less sampling to obtain a good estimate of their compositions. By contrast, the mobility of fish makes it more probable that fish distributions will vary over a short period of time, requiring a greater number of samples.

Current methods for evaluating Marine Protection Areas (MPAs) include surveying species compositions for multiple taxa, much like we surveyed Hopkins and Point Lobos (Reef Check, REEF). It is important to understand the effects of wave exposure on the distributions of different species when evaluating these areas to avoid misinterpreting the data collected. While algal and invertebrate distributions do not vary much over short periods of time, fish distributions do vary, and therefore require larger samples and more frequent surveying. Low fish counts under turbulent conditions could be misinterpreted as low species abundances. Such misrepresentations of fish abundances could lead to Sertic 9

conclusions that MPAs are ineffective in conserving species diversity. Frequent sampling is necessary to

get a good picture of species distributions, especially for motile species and in sites that are exposed to the

turbulence of the open ocean.

Figures

Figure 2: map of Marine Protected Areas in the national marine sanctuary around Monterey Bay (SIMoN)

Figure 1. List of species surveyed at Hopkins and at Point Lobos.

Figure 3: comparison of depth profiles at Hopkins and Point Lobos. The mean depth for both sites was about 37ft. Sertic 10

Transform: Fourth root Resemblance: S17 Bray Curtis similarity

2 2D Stress: 0.18 Site Hopkins 1 Lobos

2 2 2 2 1 2 2 1 2 1 2 1 2 2 1 1 1 2 2 1

1 2 1 1

Figure 4: Differences among transects for Hopkins (green) and Point Lobos (blue) on day 1 and day 2 for all species combined. Indicate that it is an MDS plot

Transform: Fourth root Algae Resemblance: S17 Bray Curtis similarity 2 2D Stress: 0.11 Site Hopkins Lobos

2 1 2 1 2 2 1

211 1 1 2 2 2211 1 11 1 2 2 2 1 12 2

Figure 5: Difference in algal composition among transects at Hopkins (green) and Point Lobos (blue) on days 1 and 2. Sertic 11

Hopkins Lobos 12

8 N u 6 m 1 b e r 4

a 120 D

p Figure 7: Comparison of the 10 m number of stipes per Macrocystis a S plant on day 1 (red) and day 2 8

N (blue) between Hopkins and Point u

m Lobos. 6 b e r 4 2 2

0 Site

Hopkins Lobos 40

Figure 6: Mean sampled algalSpecies abundances at Hopkins and Point LobosSpecies on days 1 and 2 30 N u 20 m 1 b e r

10 y a 400 D

e l p m a

S 30 N u 20 m b e r 2 10

Species Species Figure 8: Invertebrate compositions of Hopkins (left) and Point Lobos (right) on days 1 (above) and 2 (below). Sertic 12

Transform: Fourth root Fish Resemblance: S17 Bray Curtis similarity 1 2D Stress: 0.14 Site 2 2 2 Hopkins 1 Lobos 1 1 2 2 1 1 2 1 1 1 2 1 2 2 1 1 1 2 1

Figure 9: Differences in fish composition among transects at Hopkins (green) and Point Lobos (blue) on sampling days 1 and 2. Site

Hopkins Lobos 0.5

0.3 N u m

y 0.0 a 0.5 D e l p 0.4 m a S

0.3 N u m b e

Species Species Figure 10: Mean sampled fish abundances at Hopkins and Point Lobos on days 1 and 2 Sertic 13

Figure 11: percent of variance explained by 2 potential sources of variance for the abundances of the 3 taxa sampled. F 4 x e

d 3 n I

r e w o 2 P

4 x Species e

d Figure 12: Power Index for each fish species sampled when n=30. n

w 2 o P

0 0 5 10 15 20 25 30 35 Number of Transects Figure 13: The power index for fish (blue), algae (green), and invertebrates (red) when n=30??. The ideal number of replicates is at the point where the curve levels out. While 30 replicates was a greater sample size than needed to get powerful statistical analysis for algal species (a sample size of about 20 would have been enough), the power index for fish is still growing at 30 replicates, showing that more data are needed. The asymptote in the invertebrate curve is an artifact due to site. 30 transects was enough data at Hopkins but not at Point Lobos. Sertic 14

Literature Cited

Dayton PK, V Currie, T Gerrodette, BD Keller, R Rosenthal, and DV Tresca (1984). Patch dynamics and

stability of some California kelp communities. Ecological Monographs 54: 253-289.

Duggins DO (1980). Kelp beds and sea otters: an experimental approach. Ecology: 61: 447-452.

Edwards MS (2004). Estimating scale-dependancy in disturbance impacts: El Ninos and the giant kelp

forests in the northeast Pacific. Oecologia 138: 436-447.

Estes JA, MT Tinker, TM Williams, and DF Doak (1998). Killer whale predation on sea otters linking

oceanic and nearshore ecosystems. Science: 282, 473-476.

Ling SD, CR Johnson, SD Frusher, and KR Ridgway (2009). Overfishing reduces resilience of kelp beds

to climate-driven catastrophic pahe-shift. PNAS 156: 22341-22345.

Lovejoy, P (1996). Granite Point Wall. Point Lobos Foundation. 29 October 2011.

Monterey Bay Sanctuary: Marine Protected Areas. SIMoN. 29 October 2011.

Paddack MJ and JA Estes (2000). Kelp forest fish populations in marine reserves and adjacent exploited

areas of Central California. Ecological Applications 10: 855-870.

Reed DC and MS Foster (1984). The effects of kelp canopy shadings on algal recruitment and growth in a

giant kelp forest. Ecology 65: 937-948

REEF. 2007. Reef Environmental Education Foundation. 10 October 2011.

Reef Check. 2007. The Reef Check Foundation. 10 October 2011. Sertic 15

Results (25) __3__/4 Figure legends Accurate __2__/4 Figure Legends well composed (complete and concise) __4__/5 Results organized according to questions __4__/4 Graphs presented in a logical order, case made for the order __4__/4 Grammar, sentence structure and spelling __3__/4 Clarity and conciseness of writing

Discussion (25) ____/11 How well did they answer the questions they present in the Intro? 1) __2__/2 Discuss the results from the specific to the general. 2) __2__/3 Answered question about how sites differ in community composition? 3) __2__/3 Assessed sources of variation and made a strong case for whether we are able to detect differences among sites. 4) __1__/3 Presented sound logic as to why certain taxa or species were sampled well.

__2__/2 Grammar and Spelling __3__/3 General Thoughtfulness __2__/2 Clarity and conciseness __4__/5 Organization of discussion __2__/2 Context and Bigger Picture

General Notes: Good. Be consistent between the results you include and the points you make in the discussion. Do not include results that you do not talk about later.