Hannah Nolan

5/17/12

Total score: 76/100

Title [[3/4 - this is a bit long, and you’re not actually looking at any species INTERACTIONS, just ASSOCIATIONS, but you’re getting the right idea]]

Macrocystis pyrifera, Cystoseira osmundacea, and Mobile Macro-invertebrate Niche Partitioning and Interspecific Species Interactions in the Kelp Forest off of Hopkins Marine Station, Pacific Grove, California

Clarity [[10/14 – choppy sentences, work on drawing connections between related ideas; you tend to have all the right ideas in there, but you stop short of explaining how they are linked]]

Introduction [[14/20 – you need to more fully describe the specific questions that motivated the study, and describe how it is novel. Also work on connecting the dots between ideas and just writing a little bit more, you tend to leave things hanging]]

The niche diversification hypothesis assumes that diversity in an ecosystem is maintained by its number of niches, and that organisms compete with one another for control of each niche (Connell 1978; Hallacher 1985) [[and why is niche diversification interesting to ecologists?]]. If the system is disturbed, organisms will return back to the ecosystem’s original stable state (Connell 1978) [[but there are competing theories here, that you should mention]]. We first characterized the substrate type, relief, and substrate cover of Hopkins Reef using uniform point contact and then used an invertebrate swath to identify the abundance of several mobile macro-invertebrate species, and two algae species commonly found at Hopkins [good level of detail on what you did for the intro]. These species include Patiria miniata (bat star), Pisaster giganteus (giant-spined star), Steyla montereyensis (stalked tunicate), Balanus nubilis (giant acorn barnacle), Cystoseira osmundacea, and Macrocystis pyrifera (giant kelp) [[listing the species is too much detail for the intro]]. After compiling the data we looked for patterns of association that these six species might have with habitat type and primary placeholders.

By comparing similar species and their habitat associations we can determine the different niches species occupy. Habitat association can also be attributed to interpsecific interactions between primary placeholders and mobile invertebrates. We address the question whether or not there is niche partitioning among our study species in the Kelp Forest, or if interactions like grazing and predation result in species habitat association.[This is good, but I want you to describe your questions and hypotheses a little bit more completely in the intro]]

The kelp forest is an excellent place to study niche partitioning and diversification in algae and invertebrates because of the wide variety and number of species that are adapted to it as habitat. The kelp forest is an incredibly productive, multidimensional system that, like a forest, has a canopy and an understory. The bottom of the kelp forest is habitat to a number of sessile and mobile invertebrates, as well as an understory of other large brown algae.[and why is this important for this study? You’re almost there, but finish making the connection]] There are a number of interspecific interactions that occur that may drive diversity in the kelp forest (Foster, 1975). We question how these species interact with one another, and what leads to such a great diversity of species in this ecosystem. By examining the patterns of habitat association in both sessile and mobile species, our study finds niche partitioning and possible interspecific interactions of the afore-mentioned species of algae and invertebrates.

Methods [[14/18 – you could use a clearer description of the data analysis and more clear linkages between the sampling methods and the questions, but overall you’ve got the right idea]]

General Approach

In order to identify the substrate, relief, and primary placeholders, we conducted an observational study by using a uniform point contact (UPC) survey on April 10th, 2012. Primary placeholders include algae’s such as erect coralline and various types of red algae, as well as encrusting sessile invertebrates like sponges and tunicates. Uniform point contact is a good way to characterize the bottom of a system, and to look at what sessile species are utilizing the different types of relief and substrate. [[nice amount of detail here]]

On April 17th, 2012 we conducted another observational study, and performed an invertebrate swath. Invertebrate swaths are good for counting the number of benthic, mobile invertebrates in a system. When paired with the data from our UPC we can look for patterns of association that the mobile invertebrates might have and compare between species. UPC combined with swath surveys can show if mobile species have preferential substrate, relief, or primary placeholder that they live on. These patterns could be attributed to niche partitioning and diversification, or boundaries set by interspecific interactions. [[also good level of detail]]

Hopkins Reef as a System

The study occurred at Hopkins Marine Station (36°37’13.23”N, 121°54’07.95”W) in Pacific Grove, California. Hopkins reef is a kelp forest growing on a granitic substrate. The reef is unusual because it lacks a Pterygophera californica understory, and instead has an understory of Cystoseira osmundacea, as well as other brown and red algae species. The canopy is entirely Macrocystis pyrifera. Hopkins is a no-take marine reserve, which makes it an excellent study site for examining a reef without the presence of fishermen. A large number of invertebrate and fish species use this kelp forest, which makes it an exceptional site for looking at species interactions. [[don’t forget the diversity of habitats and species!]]

Study Design

Hypothesis One- The invertebrate species compared are found on certain relief and substrata because they are adapted to occupy different niches

The algae and invertebrate species that this study focuses on are Patiria miniata which we compare to Pisaster giganteus, Steyla montereyensis which we compare to Balanus giganteus, and Macrocystis pyifera which we compare to Cystoseira osmundacea. The species being compared are either similar because of morphology, because of their diet, or both. For testing whether or not these species are adapted to different niches, we look at the amount of organisms associated with relief and substrate type by using UPC and Swath data and then compare between similar species. This comparison can help characterize what habitat these species commonly associate with and if the habitat is different from the species that they are being compared to. If the species being compared are significantly different when it comes to the substrate, relief, and cover type they associate with, then it can be hypothesized that the species are adapted to occupy different niches in the kelp forest. Statistically significant positive correlations are greater than 0.1, statistically significant negative correlations are less than -0.1.

Hypothesis Two-The invertebrate species compared are found on certain relief and S\substrata because of interspecific species interactions

The species that we compare in this study are very similar. Patiria miniata and Pisaster giganteus are morphologically similar and part of the same taxonomic class, Asteroidea [[but they eat very different things, so may not be competing]]. Steyla monteryensis and Balanus nubilis are not morphologically similar, but both are suspension feeders. Cystoseira osmundacea and Macrocystis pyrifera are similar because they are both large, brown algae. These six species may have interspecific interactions with one another and with the UPC species. To test for this interaction we look at the data from the UPC and Swath and compared what relief and substrate type these species associate with and whether or not their habitat associations are very different. Positive or negative associations with UPC primary-placeholder species might be the result of interspecific interactions. [[this is pretty good, but I’d like to see you describe more clearly how the data collection methods allow you to answer your questions and THEN talk about how you will interpret results]]

Collection

Uniform Point Contact (UPC) Data was collected by a group of undergraduate students on SCUBA on April 10th, 2012 between 8-11 in the morning. In pairs, we were located at ten points along a permanent transect line in five meter increments between the 90 and 135 meter marks. We swam along a 30-meter tape, placed our finger down every fifty centimeters, and then recorded the substrate, relief, the presence of drift kelp or juvenile laminarias, and the sessile organism. The meter tapes were laid out at 90° offshore, and 270° onshore.

Invertebrate swath data was collected by the same group of undergraduate students on SCUBA on April 17th, 2012 between 8-11 in the morning. The same buddy pairs went to their assigned meter mark between 80 and 135. The meter tapes were laid out again at 90° offshore, and 270° onshore. A buddy pair would swim on either side of the tape and record the number of large invertebrate species that they saw in one by five meter subsections (Fig 1). [[you might want some more detail here, and you definitely want to explain how many data points you got per transect and the spatial resolution at which you can compare the UPC and swath (10 square meters)]]

Results [[12/16 – you get a little into a laundry list which is not idea. Also, you can make a single figure with multiple lettered parts (i.e. Figure 1a, 1b, etc.) which would be simpler and save redundant figure captions. You should also make sure there’s a table to translate the species codes into the actual species names. In general, try to focus on how the results relate to your questions, and you’ll do better]]

System Results

Characterization of the substrate type and relief (habitat association) is very statistically significant (P-value <0.000001). Primary placeholder (UPC association) is also statistically significant (P-value 0.000011), but not as significant as habitat. The percent of variance explained in swath species abundances in terms of UPC species abundances is 24%, and for habitat attributes it is 76%. [[Describe what this MEANS]]

Niche Partitioning and Competition Results

Balanus nubilis has a strong [positive or negative?] association with high relief (>2 meters) and boulder substrate (Fig 5). Balanus has a strong association with hydroids, branching red algae and cup corals as primary placeholders (Fig 13). Balanus has a weak association with shell substrate and solitary tunicates as primary placeholders (Fig 13). In contrast Steyla montereyensis had a strong association with shallow (10cm-1m) relief and bedrock substrate (Fig 6). Steyla has a strong association with articulated coralline algae, encrusting coralline algae, barnacles, phragmatopoma worms, sponges, and bushy red algae (Fig 14). Steyla has a weak asocation with shell substrate, bare rock, bare sand, and sessile bryzoans (Fig 14).

Patiria miniata moderately associated with sandy, flat relief (Fig 9). The primary placeholders that Patiria weakly associates with are Corynactis californica and articulated coralline algae (Fig 11). Patiria strongly associates with sponge, bryozoan, branching red algae, other laminarias, and barnacle primary placeholders (Fig 11). Pisaster giganteus somewhat associates with boulders of moderate relief (Fig 10). Pisaster had a strong association with red turf algae, and Dictyoneurum californicum as primary placeholders (Fig 12). Pisaster weakly associates with colonial tunicates, lacy red algae, tubeworms, and Corynactis californica (Fig 12).

Macrocystis pyrifera and Cystoseira osmundacea both have a close association with growing on shallow (10cm-1m) relief bedrock (Fig 3,4). Cystoseira has a strong association with branching red algae, crustose coralline, leafy red algae, Macrocystis holdfast, and other laminarias as primary placeholders (Fig 15). Cystoseira has a weak association with sponges, Phragmatopoma worms, and dead Macrocystis holdfasts as primary placeholders (Fig 15). Macrocystis pyrifera has a weak association with lacy red algae, and dead Macrocystis holdfasts (Fig 16). The plant has a very strong association with solitary tunicates (about 0.58 statistical significance; Fig 16). Macrocystis also has somewhat statistically positive relationships with colonial tunicates, Cystoseira, Diopatra ornata, and encrusting red algae (Fig 16). [[this has turned into a laundry list of associations which is not the intention. Try organizing byquestion/ hypothesis and describing how your results answer the question or support or refute the hypothesis]]

Discussion [[17/22 – you do a good job of suggesting mechanisms for your results and making sense of those results as well as future studies to answer some of the outstanding questions. Things you could do better: closer ties between results and your original questions and better use of the scientific literature for context and comparison with past studies.]]

Diversity is maintained because similar species are adapted to occupy different niches from one another

Four out of the six species that we examined in this study appear to be adapted to different niches from one another. Pisaster giganteus is adapted to live on boulders of moderate relief, whereas Patiria miniata is adapted to live on flat, sandy bottom. Steyla montereyensis shows a strong association with shallow bedrock, in comparison to Balanus nublilis which has a strong association with high relief boulders. Patiria miniata and Pisaster giganteus are both morphologically similar and members of the class Asteroidea. Patiria is an omnivore that has been seen preying on diatoms and seagrass, whereas Pisaster giganteus is a carnivore that preferentially feeds on barnacles (Farmanfarmaian, 1958). Patiria is also known to preferentially feed on Tubulipora species of bryozoan (Day, 1981). Steyla is a passive suspension feeder that relies on filtration feeding, whereas Balanus nubilis is an active suspension feeder that actively grabs food from the water. These four species are either similar because of their morphology or because of their feeding strategies, but are found to be associated with different habitats on the bottom. They potentially have partitioned the available niches in order to not compete with one another. [[nice]]

Cystoseira osmundacea and Macrocystis pyrifera are both large brown algae’s that show a moderate-strong association with shallow (10cm-1m) bedrock. The presence of a Macrocystis canopy is known to limit the availability of light to other large brown algae, and limit their presence in a kelp forest (Reed, 1984). However, in this study Macrocystis and Cystoseira are found to utilize the same habitat type, and are found to have moderate-strong associations with one another as primary placeholders (Fig 3,4,15,16). It should be noted that Cystoseira is more commonly found in areas of central California where Macrocystis grows (Schiel, 1985). Cystoseira also has a moderately strong association with other laminarias (large brown algae) as primary placeholders, even though it has been speculated that Cystoseira and Macrocystis together outcompete other species of large brown algae (Foster, 1975). Since Cystoseira and Macrocystis were counted in one by five meter subsections, it is possible that other laminarias use the same habitat as Cystoseira and Macrocystis, but do not grow near these large browns algae. The one by five meter subsections also explain why Macrocystis plants do not show strong correlation with Macrocystis holdfasts as primary placeholders. Primary placeholders were recorded as one data point every fifty centimeters along a thirty-meter tape, and swath data was the number of species counted in one by five meter subsections (Fig 2).