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Connor Gervais

October 29, 2011

Kelp Forest Ecology

[3] Comparison of the difference in the species composition of fishes, algae and invertebrates in two spatially close ecosystems

Abstract [12]

We wanted to find differences [[wanted to find, or wanted to see if they differed??]] in species composition between Point Lobos Ecological Reserve and Hopkins Marine Life Refuge using a quantitative sampling of fishes, algae and invertebrates found in the Monterey Peninsula. [why??] We found that there is a significant difference in the species composition of algae and invertebrates between the two sites; however fish composition is masked by the effect of the day and by an interaction affectbetween site and days. The overall difference in species composition is driven by a site effect [what does that mean??]. More fish samplings and invertebrate samplings will need to be done to get more powerful results. [but you detected differences between sites… why would you have to sample more?]

Introduction [2,2, 2, 2, 3, 2, 1, 2, 2, 3, 2] = 23

Understanding the differences in spatially close ecosystems helps create effective Marine Protected Areas (MPA’s). [how does that work??] The ecology in study sites can be unique to that area because of differences in topography, biology, or chemistry in the water. If we want a kelp forest to be protected and enable the progeny of itself and other species to inhabit another area, it would be best to find another area of similar structure. , Rrather than pick an arbitrary plot of coastline that may or may not encourage organism growth and recruitment. [that wasn’t a sentence] While our two study sites are MPA’s, this study will verify that there are variations in species composition between the sites that are close to one another and should be similar??. [I don’t understand what that sentence means]

Our study, conducted at Point Lobos Ecological Reserve and Hopkins Marine Life Refuge, used a quantitative sampling of fish, algae and invertebrates found in the Monterey Peninsula to estimate the species composition. It has been shown that kelp forest communities do show differences in areas that are not very far from each other (citation?). These kinds of studies have been done on kelp forest systems worldwide, and they find species composition varying between their study sites as a result of spatial and temporal differences in what? (Wernberg et. al. 2003). A quantitative sampling is better used for a study estimating the density of organisms. [yup, because density is a quantitative value]Of the species chosen, several species of algae are known to be more prevalent in one site or the other. This distribution of algae can affect the distribution of other species that recruit to specific algae or cues in the environment that are affected by algae. The fish and invertebrate species we chose to sample are well known species that are often seenfamiliar and common. We want to know to what extent does the site have on species that are seen at these locations or if there are any other factors contributing to the variance seen. [that sentence also does not make sense.]

Variance in our study will arise from differences in the data. [yes, that’s the definition of variance.] If there is a difference in the species composition by between sites, then the variance should only reflect a difference by site; . howeverHowever, there are potentially confounding factors such as the differences between sampling days that the sampling took place, the time of day, as well as not having enough samples. This is why we sampled on two days, with around 15 replicates per site per day, and at the same time of day. The conditions of the ocean were very different on both the two days. On the first day the sites were calmer and there was very little water movement, but our second sampling day was much rougher; there was more swell, the water clarity diminished and there was an increased surge. [did this happen at both sites or only at Pt Lobos??] This may increase the variance of our data. In addition for to testing if the site sampled yields different species composition, we also tested whether or not the day sampled would impact the results of the sampling to account for the different oceanic condition. We also tested whether there was any interaction affect on the data [???]using both site and day data.

Methods [2, 2, 0,8,2,3, 3,0,3,2,2,2, 3 ]= 34

Approach????

Study System [4,0, 2, 2]

Our study sites, Hopkins Marine Life Refuge in Pacific Grove, CA (36˚36’N, 121˚54’W) and Point Lobos Ecological Reserve in Carmel, CA (36˚31’N, 121˚57’W), are roughly 10 miles away from each other yet have different ecological structures [wait… if we knew that, why we would conduct a study to test that hypothesis?] which is a reason our study was conducted at these two places (Figure 1). As both sites are close to each other, the main substrate is the same, granitic rock, allowing for longer lived Macrocystis pyrifera forests and plants as the substrate isn’t erosive like the sandstone found off of Santa Cruz; however the water movement and vulnerability exposure of the two sites are very different which can affect the organisms found residing in the two spots. [maybe that’s why we selected the two sites and that’s why we see differences?] Hopkins Marine Life Refuge is a very sheltered site on the inside of the Monterey peninsula and is resistant to [no… is rarely exposed to] large perturbations that happen elsewhere. The site is a kelp forest with low to medium relief and is surrounded by sand flats and diopatra beds of the tubeworm, Diopatra. The forest we sampled at Point Lobos is very exposed to water movements as most swells come from the westward direction directly into Lobosthe cove were we sampled. We were diving at the entrance to a cove which can condense concentrate water movement into the cove that will increase the intensity of movement and impact what can live there. Lobos also has more relief than Hopkins exposing more habitat for organisms that desire crevices.

Since the sites are very close we can assume that they both have the potential for the same species to recruit there and what we see is a direct affect of the site. There is a correlation between exposure and the species composition that has been studied before, some species cannot recruit to more exposed places, but will outcompete other species where it is calmer (Harrold et. al. 1988).

Both Hopkins and Lobos are MPA’s, and do not allow fishing of any kind, removing confounding factors when counting fish.[how???]

[Should add a description of the species sampled and whywe selected those species]

Is there a difference in species composition between Hopkins and Point Lobos?

In order to test the hypothesis that there is a difference in the assemblages of species between Hopkins and Lobos in terms of total species composition, [good]we conducted quantitative surveys on SCUBA at both Hopkins and Lobos over the course of two days, Tuesday October 11 and Thursday October 13. [this would have been good up in the general approach section!] At both sites and on both days, buddy groups were given meter mark numbers to sample. The group at Hopkins sampled on the permanent transect line off the deeper side of their transectthe cable (90˚heading), and then again on the shallower side of their transect cable (270˚ heading). At Lobos, there is no shallower side or permanent transect line, so each group was given two meter marks on a temporary transect line and sampled at a 90˚heading. One buddy samples the left side of their meter mark and the other buddy would sample the other side. We were sampling the quantity density of 9 nine species of fish, seven7 species of algae, and 13 species of invertebrates (Figure Table 12).

To get a fish sample not affected by human interference, it was agreed between all buddy pairs that as each pair rolled their meter tape out they would do their fish survey and stop every 10m to record their data until all 30m was rolled out. This was done so that the fish seen were there naturally, not because our presence kicked up sediment with food particles. The only fish counted were fish that were in a 1m wide by 2m tall by 30 m long area in front of the diver to have a standardized unit area for all buddy pairs.

Every group divided their dive differently when conducting their invertebrate and algae sampling. Some sampled them both at the same time, others sampled each individually. At each site, buddy pairs sampled the number of algae species seen in a 1 m² area on each side of the transect with one diver on the left the other on the right. We were to recorded the number of individuals per of each the species for all specieswe sampled with the exception of M. pyrifera. Every number recorded for M. pyrifera was the number of stipes per individual. The information was written down separately for every 10m in each 30m transect.

Invertebrates were counted in a 1m² area in front of the diver the same way at both sites. The data was recorded for every 10m section in the 30m transect.

All of the results gathered were used in a PERMANOVA to identify if the site sampled had any effect on thetest for a difference in species composition foundbetween the two sites on each of the two days sampled. A PERMANOVA P value of less than 0.05 is statistically significant. What about the MDS plot??

Does the difference in species composition between Hopkins and Pt Lobos vary by taxa?

We think that not only does the species composition vary between the two sites, but also that the species composition varies by taxa. The data collected from all the species (same data used in above) will bewere compiled and analyzed in a PERMANOVA to see if the site has any impact on fish, algae, and invertebrate communities. Variance for fish, algae and invertebrates was also found to determine what if the site affect was causing a difference in species composition. [this is a poor description of simply trying to say… we tested the hypothesis that species groups (fishes, invertebrates or algae) differed in the extent to which each group differed between the two sites.]

Is there a difference in species composition between days?

The data acquired by the sampling method stated above was used to test if the sampling day contributed to any differences in species composition. The class was split up so that around half of the buddy pairs dove Lobos on Tuesday while the other group dove at Hopkins. On Thursday the groups switched dive sites, but buddy pairs were not kept constant. All of the sampling dives were done in the morning to keep time of day constant. Using aWe used a PERMANOVA will to show test if there are differences in species composition that are caused bybetween the two sampling days a day affect.

Does the difference in species composition between days vary by taxa?

The data, found generated using the sampling method stated above, was separated by fish, algae, and invertebrates to distinguish if any of the taxa had variance caused by a day affect[???] . The PERMANOVA used for the above hypothesis was redone was also used to show test if there are any significant differences in among the three taxa.

Does both site and sampling day affect species composition (interaction effect)?

To test whether the species composition is affected by the interactions of site and day sampled the data from site analysis and day analysis [???], we tested for a site by day interaction with thewas put into PERMANOVA to generate a value to see if there was an interaction affect. Interaction affects are when there are unlinked changes that are different in both sites. [yes… but say that more clearly… Day by site interactions indicate that the two sites differ in how they differ between days.

Does the interaction between site and sampling day vary by taxa?

To used the PERMANOVA to test the hypothesis that the day by site interaction differs between the three species groups (fishes, invertebrates, alga). We compared the strength of the interaction term calculated for each species, among the three species. We used the data used for testing the first hypotheses in a PERMANOVA test putting site against day to see if there was any significant interaction effects.

Results

There is a difference in species composition between Hopkins and Point Lobos

There was a significant difference in the species composition between the two locations (Figure3, PERMANOVA; all species, site effect, P=0.001). The site affected the overall species composition which validates our hypothesis.

Difference in species composition between Hopkins and Pt Lobos varies by tax

Between taxa, only algae and invertebrates showed any statistically significant differences by site (Figure 3, PERMANOVA; algae and invertebrates, site affect, P=0.001 for both). When looking at the variance in species, the only variance for both algae and invertebrates comes from the site affects (Figure 4).

The total fish composition between Lobos and Hopkins was not significant (Figure2, PERMANOVA; site effect, P=0.319). Very little of the variance in the fish counts was due to a difference in site (Figure 3).

There is a difference in species composition between days

There was no difference in the species composition between the days. There was no significant value to show that the general species composition is different depending on the day sampled (Figure3, PERMANOVA; day effect, P=.382).

Difference in species composition between days varies by taxa

Although there was no difference in species composition, there was a difference in species composition be day in fish (Figure 3, PERMANOVA; day effect, P=.043). Unlike the algae and inverts, variance in fish data was influenced by day more than by site (Figure 4). Day differenced overwhelmed the site differences and makes it hard to detect any differences in species composition by site if there are any (Figure 5).

Algae and invertebrates compositions were not influenced by day affects. At both sites, the abundance of algae and invertebrates found were proportionately similar to the abundances found on day 2 at the respective locations. (Figures 6 and 7).

Both site and sampling day affect species composition (interaction effect)

There was no interaction effect on the species composition yielding our hypothesis false (Figure3, PERMANOVA; SIxSA effect, all species, 0.375).

The interaction between site and sampling day varies by taxa

Only fish expressed any interaction affects (Figure3, PERMANOVA; SIxSA effect, fish, P=0.025). The other two taxa were only affected by the site samples.

Discussion

Fish

The fish that were seen on a particular sampling day were dependant on the day that was sampled more than which site was sampled. Fish are highly mobile and when the weather gets rough, the fish will all seek refuge.

There were significant differences in algal assemblages in our study sites. M.Pyrifera is the dominant canopy algae at Hopkins with an understory comprised of mainly Cystoseira osmundacea and Chondracanthus corymbifera. The average stipes per transect as well as the average number of stipes per M. pyrifera were higher at Hopkins than at Lobos (Figure 8-1 and 8-2). This shows that the M.pyrifera at Hopkins were older and more abundant and is due to the sheltered nature of Hopkins. Even though Lobos has a similar canopy density of M.pyrifera it has a much denser understory of Pterygophora californica and to a lesser extent Eisenia arborea (Paddack 2000). P. californica are one of the longer lived algae in California and tend to do well when turbulent conditions annually take some M.pyrifera out because P. californica have thicker stipes and are harder to rip off of the substrate. Also with a less dense canopy, there is more light available and P.californica can outcompete M.pyrifera for light (Reed and Foster 1984). The distribution of the canopy species as well as the understory species can be attributed mainly to difference in exposure at the two sites. Studies have been done at these sites and at similar sites and get the same results at sites with similar exposure (Harrold 1988).

At Lobos, even though we did not have the same transect both day, the similarity between both days suggest that the distribution in algal assemblages may be constant over the whole forest; compared with Hopkins which has more variation even though the same areas were sampled because of the permanent transect lines (Figure 6).

Algal assemblages will not necessarily change between days because the organisms are sessile and their locations remain constant, unless they are removed. They can’t hide when the weather and water movement gets turbulent like what happens to the fish, they have to ride it out in the open. It’s logical that we have the most powerful data set (out of fish algae and invertebrates) for algae.