Monica Chu

10/31/11

BioE 161/L

Total= 2+14+20+24+

Lit Cited= 6

[2] Species composition comparison between Hopkins Reef and Point Lobos

Make you title reflect the question being asked by this comparison

Abstract [14]

Communities that are “just around the corner” can vary by taxa based on site, sampling day, or a combination of both, also known as the interaction effect. Point Lobos State Reserve and Hopkins are areas that vary on small scales. Kelp forest algae, fish, and invertebrates vary at both sites due to the different effects and we attempt to determine what disturbances or mechanisms cause these variations. By sampling the two areas on two days, we can determine that algae is affected by site only, fish are affected by sampling day and the interaction effect, and invertebrates are affected by site only. This study, however, is not enough to determine the effects on taxa and more studies need to be conducted to perform more swaths on fish and invertebrates. Overall, this study provides more information for ecologists to determine what mechanisms structure a community and how communities respond to physical and biological disturbances.

Introduction [20]

The study of how a natural community is structured and how it responds to physical and biological disturbances is of great interest for to ecologists (Holbrook 1997). Communities differ on a large scale depending on their latitude, and on a small scale depending on local oceanographic features, species, and many other reasons (Edwards 2003). Oceanographic features, such as wave motion, and substrate type, can create variation in communities that are close in proximity. Other causes of variation can be derived from the diversity of local species found in communities, which may lead to intraspecific and interspecific interactions within a community that also have important structuring mechanisms (Reed and Foster 1984). Overall, it is necessary to understand what mechanisms create variation in different areas. In this study, the communities of Hopkins Reef and Whaler’s Cove at Point Lobos were compared to determine differences in species abundance. Due to oceanographic features, species composition may differ at Point Lobos or Hopkins depending on site, sample day, and a combination of both, also referred to as the interaction effect.

These three sources of variation, site, sample day, and the interaction effect, will have different effects on both sites that are of interest. Daily climate conditions and ocean conditions change day to day and will also affect each area differently. The effects of oceanic features are understood relatively well compared to those of climate (Holbrook 1997). Although there is no prior credible work done to compare the two sites, we know that Point Lobos and Hopkins are affected by mechanisms that create variation in certain taxa. We sampled algae, invertebrates, and fish along transects for both sites on two days.

Methods [24]

[put this list of species in a table, rather use so much space in the text]At each site, we had data sheets with specific species of kelp forest algae, fish, and invertebrates to search for on each of our transects. The algae and plants observed were chain bladder kelp (Cystoseira osmundacea), turkish towel (Chondracanthus corymbifera), Dictryneurum californicum, giant kelp (Macrocystis pyrifera), Dictyoneurum reticulata, and sea grass (Phyllospadixspp.). The fishes observed were the painted greenling (Oxylebius pictus), kelp greenling (Hexagammos decagrammus), blue rockfish (Sebastes mystinus), gopher rockfish (Sebastes carnatus), black and yellow rockfish (Sebastes chrysomelas), kelp rockfish (Sebastes atrovirens), black surfperch (Embiotoca jacksoni), striped surfperch (Embiotoca lateralis), and the pile perch (Damalichthys vacca). The invertebrates we accounted for were the bat star (Asterina miniata), short-spined star or pink star (Pisaster brevispinus), great-spined star (Pisaster giganteus), fish-eating anemone (Urticina piscivora), white-spotted anemone (Urticina lofotensis), sand anemone (Pachycerianthus fimbriatus), orange cup coral (Balanophyllia elegans), orange puffball sponge (Tethya aurantia), blue ring top snail (Caliostoma ligatum), sheep crab (Laxorhynchus grandis), red abalone (Haliotis rufescens), and the red sea urchin (Strongylocentrotus fransiscanus).

Study system

The Hopkins Marine Station is a research facility owned by Stanford University. The marine station is located in Pacific Grove in central California. [lat. lon.???] Hopkins Reef, where we dove for sampling, is just off a small beach with a dense giant kelp forest canopy and has a permanently installed cable that runs roughly North and South. The cable has a surface buoy attached at a one-hundred meter marker. Transects were done off this permanent cable at every ten and five meter marks. Subtidal communities in this area consisted of kelp forests, hard rocks, and sand. This area is open to all types of disturbances, except those by humans; and has no unusual stresses – only biological stresses, such as otter predation; however, this does not negatively affect the ecosystem.

Point Lobos is a state reserve just North of Carmel in central California. [lat. lon.???] The specific site we were at is Whaler’s Cove and the site we dove at is at the opening of the cove to the outer bay. The subtidal communities found in this area include hard rock, kelp forest, and sand sediment communities. This site has no permanent cable like the one at Hopkins Reef. At this site, we had to create our own main meter line to perform transects off of and surveyed every five and ten meter marks. Point Lobos is a protected area; so Whaler’s Cove has very little human activity, which is limited to a certain number of people per day. There are no unusual stresses, and biological stresses include otter predation, similarly to Hopkins.

Differences in species composition between Hopkins and Point Lobos based on taxa.

To determine if there was taxa variation between sites, we surveyed both sites on the same day, on two different days. In pairs, we swam out to the buoy, descended down the buoy line, and swam out to each of our respected given meter marks along the cable. Once at our meter marks, we clipped in our thirty-meter meter tape, took a compass bearing offshore (90 degrees) and swam out thirty meters. One the way out, both of us performed a fish survey one meter wide, two meters up, and in ten meter length sections. This divided the thirty meters into three ten-meter sections. We also made sure to not count the same fish twice if the fish was on the meter tape, between our respected sides. At the end of the first leg (thirty meters), we recorded any last minute data, turned around and performed the invertebrate swatch using one meter wide and ten meter long sections. After that second leg, we were back at the main cable, turned around, and swam back offshore performing the algae swath on the third leg. With algae, we also used the same one by ten meter sections. We counted each individual plant. With M. pyrifera, we counted number of stipes at breast-height for each plant and separated multiple plants with commas. The purpose of this is to obtain an estimate of the biomass and canopy of the transect section. After this third leg, we swam back towards the cable while reeling-in the meter tape. With our meter tape still clipped in, we went in the opposite direction, inshore (270 degrees) on the same meter mark. If necessary, we surfaced to switch tanks before surveying the next transect. We performed the same procedure on this site.

At Point Lobos, the same procedure was also executed. The only difference is that both transects were both onshore and only one dive was allowed. So it is possible that not all sections of the survey were completed.

To determine if there was a difference in species composition between Lobos and Hopkins by taxa, we compiled the data to create multi-dimensional scaling plots of all species and each taxa, algae, fish, and invertebrates. We also created a statistical table showing probability values (PERMANOVAs) for site and compared each species’ p-values. We also constructed bar graphs that show species distribution for both Lobos and Hopkins on both sampling days. These graphs are separated by taxa. The purpose of these graphs is to decipher which species in each taxa contributed to the variance discovered.

Differences in species composition between days based on taxa.

We gathered data using the same procedure. We used the same statistic table, which also gave us a p-value for sampling day, and also used the same bar graphs of species distribution for each taxa.

Differences in species composition caused by the interaction effect based on taxa.

The same data collected was used to analyze the affect sampling day combined with site had on species composition. Thus, the same procedure was used. For this section we only used the statistic table, which also gave us a probability value for the interaction effect. This was the only way to determine if the interaction effect had an effect.

Results

Differences in species composition between Hopkins and Point Lobos based on taxa.

We conclude that Point Lobos and Hopkins have different species composition (Fig. 1). When we separate all the species into their respected taxa, we find a significant difference in algal species composition between sites (Fig. 2, and Table 1, Permanova: site effect, P=0.001). There was significantly more C. corymbifera and C. osmundacea at Hopkins than at Lobos; whereas there was more P. californica at Lobos compared to Hopkins (Fig. 5).

There is no great effect of site on the species composition of the fish assemblage (Fig. 3, and Table 1, Permanova: site effect, P=0.319). It was observed that Hopkins has D. vacca, E. jacksoni, while Lobos has zero to few of them (Fig. 6).

Similar to the algal assemblage, there is also a strong effect of site on the species composition of the invertebrate assemblage (Fig. 4, and Table 1, Permanova: site effect, P=0.001). Every species that was sighted at Hopkins was also sighted in Lobos (Fig. 7).

Differences in species composition between days based on taxa.

There is no effect of sampling day on the species composition of the algal assemblage between sites (Table 1, Permanova: sampling day effect, P=0.724). There were no significant changes in abundance in either species of algae.

There is an effect of sampling day on the species composition of the fish assemblage (Table 1, Permanova: sampling day effect, P=0.043). Certain species are present one day and present the second sampling day in a different number. On day one, we observed many S. atrovirens, and E. lateralis at Hopkins, but fewer on the second day – we observed many S. atrovirens at Lobos the first sampling day and fewer the second day too. At Hopkins, we observed that there were more black rockfish seen on the second sampling day compared to on the first (Fig. 6).

Sampling day does not have an effect on the species composition of the invertebrate assemblage (Table 1, Permanova: sampling day effect, P=0.505). There were no changes in abundance of any recorded species on any day (Fig. 7).

Differences in species composition caused by the interaction effect based on taxa.

The interaction effect does not have any effect on the algal species composition (Table 1, Permanova: interaction effect, P=0.926).

There is a definitely effect of site and sampling day on the species composition of the fish assemblage (Table 1, Permanova: interaction effect, P=0.015).

The species composition of the invertebrate assemblage was unaffected by the interaction effect (Table 1, Permanova: interaction effect, P=0.569).

Figure 1: Multi-dimensional scaling plot of all species comparing sites Point Lobos and Hopkins. Each plot represents one transect done at a either site on either day one or two. The stress value, 0.18, shows that rank order correlation between similarity scores and distances between pairs of points is good – the lower the value, the better.

Figure 2: Multi-dimensional scaling plot of kelp forest algae species compared at sites, Point Lobos and Hopkins. Each plot represents one transect that was surveyed on either day one or two. The stress value, 0.11, is less than 0.2; therefore correlation between points is adequate.

Figure 3: Multi-dimensional scaling plot of kelp forest fish species recorded at sites Point Lobos and Hopkins. Each plot represents one transect surveyed at either site on day one or two. The stress value, 0.14, is less than 0.2.

Figure 4: Multi-dimensional scaling plot of kelp forest invertebrate species recorded at sites Point Lobos and Hopkins. Each plot represents one transect surveyed at either site on day one or two. The stress value, 0.18, is less than 0.2; but very close.

Figure 5: Bar graph shows distribution and abundance of kelp forest algal species in two sites, Hopkins and Point Lobos. The two graphs on top represent the first day of sampling and the two graphs on the bottom represent the second day.

Figure 6:Bar graph shows distribution and abundance of kelp forest fish species in two sites, Hopkins and Point Lobos. The two graphs on top represent the first day of sampling and the two graphs on the bottom represent the second day.

Figure 7: Bar graph shows distribution and abundance of kelp forest invertebrate species in two sites, Hopkins and Point Lobos. The two graphs on top represent the first day of sampling and the two graphs on the bottom represent the second day.

Table 1: PERMANOVA table of results at Hopkins and Point Lobos for all species, algae, fish, and invertebrates. For each taxa and all species, relationship of the taxa with site, sampling day, and interaction effect were calculated. P-values used for analysis of variation adequacy.

Figure 8: Graph comparing the number of transects as a function of power to indicate adequacy of the number of transects used for each taxa. This is done for each taxa. Algae is represented by the green line. Fish are represented by the light blue line, and invertebrates are represented by the red line.

Discussion

Algae

It is clear that species composition at both sites is different based on taxa (Fig. 1). Most results supported this and showed differences between sites in certain taxa. The most variation can be seen in algal species composition. The reason Turkish towel and chain bladder kelp were significantly more sighted at Hopkins may be due to the stronger holdfasts – Pterygophora may not be seen in Hopkins because the area is more open to water motion and Pterygophora cannot settle on any substrate due to the stronger wave motion. Turkish towel however is red algae that can easily be torn off substrate; so strength of holdfasts is an unlikely reason for the difference in species composition is unsure. A different reason for the variance may be due to predation and higher predators. Previous studies have shown that herbivores and their predators can affect distribution of algae (Reed and Foster 1984).

It makes sense that sampling day will not have an effect on algae because an alga is permanently attached to substrate once it settles. Unless a giant storm that tore out all the kelp were to occur, we would probably not see a change in number of stipes on M. pyrifera, or the number of individual plants. This allows ecologists to conduct algae surveys on a time frame that is more spread out to account for climate changes and how they would affect algae distribution and abundance (Holbrook 1997).

Fish

The indifference in fish species between sites is not very surprising because both sites have communities suitable for each species. Pile perch and black surfperch were seen at Hopkins, but not Lobos and this may be due to a necessary amount of water motion that Hopkins obtains, but Lobos does not. This difference may also be determined by competition and the two species are out-competed by other at Lobos. Nonetheless, the reason for variation in species composition by site based on taxa is unclear and requires further study.

The number of individuals for each fish species did not shift very much between sampling day one and two; however, certain species were abundantly present one day and not as abundant the other day. Water motion at both Point Lobos and Hopkins was more intense the second sampling day and this may account for the reduction in individuals seen. The stronger surge and higher wave heights may have been a sign for the fish to retreat to their refuges where they would not be endangered or hurt by the wave action. The relative abundance, presence, and safety of the fish species are important in kelp forests because they positively influence the general overall health of the kelp forests (Davenport and Anderson 2007).

Invertebrates

There is an effect of site on species composition of invertebrates and there is no effect of sampling day on species composition of invertebrates; however, all species seen at one site were also seen at the other (Fig. 7). Based on personal observations, no transect is exactly the same as the other and invertebrates tend to be sedentary or have a small range in which they move. This may be because invertebrates need to live on certain substrates. For example, sand anemonies are only found in the sand. Some transects at either Lobos or Hopkins may or may not have had a sand community, which creates variation depending on site.