Qualitative Survey ofn Abundance and Distribution of Marine Species at Hopkins Marine Station
Andrew Kim
Title: 4 pts
Introduction [0, 0, 2, 4, 4, 2, 0, 2, 2, 2, 2] 20 pts
Citations????
Describing the distribution and abundance of species is an important first step in understanding the general ecology of any given system. In the Monterey Bay, the kelp forests provide a unique habitat for a very diverse array of plantalgae, fish and invertebrate life. Hopkins Marine Station is a well known study site in the bay and does well to provide insight into the abundance and distribution of marine biota. Understanding the abundance and distribution of species at this site can lend us some insight into the current state of the ecosystem and the key species that may dictate determine the ecological patterns observed.
A qualitative survey of the area was conducted in order to describe the species composition at this site. The qualitative survey was chosen as a means of being cost and time effective, as opposed to a quantitative survey which would have taken more time but yielded more significant data. [really? Or was it so we could assess the value of this approach??)
By choosing to survey the site qualitatively, we needed wanted to address some issues in terms of the sampling that took place.We needed wanted to look at how buddy pairs differed in sampling and the reasons for these differences. [why?? relate these specific questions to you missing general question of how useful are qualitative surveys for describing a kelp forest community or species abundances?] Some differences observed [why are you telling us the results before you tell us the questions below?] may have been due to a non-standardization of diving and identification practice, or due to the subjective nature of gauging abundance. Some species exhibited considerable variance according to the data, while others were more standardized and similar across the surveyors. There were species that seemed to be relatively good candidates for sampling using these qualitative methods, such as the giant kelps, Macrocystis pyriferaand Cystoceira osmundacea,(??) and the invertebrate sea star, Patiriaminiata, while others were poor candidates. The validity of this survey depended on two important questions:
- Do buddy pairs differ in their sampling (between individuals)? What might be some reasons for the differences?
- Which species seem relatively good or poor candidates for sampling using qualitative methods? Are there characteristics of these species that may lead to their being poor or good?
Methods [2, 0, 0, 0, 0, 2, 2, 0, 0, 0, 0,0, 2, 4, 2, 2, 2] 18 pts
First provide a description of general approach
Study site and sampling separate these!!
This survey took place at Hopkins Marine station in Pacific Grove, CA on September 27, 2011. Describe the environment and the species here.
Present your questions as subheadings and link design, methods and analyses directly to each question.
[write in first person whenever possible] 14 Buddy pairs were each given meter marks in 5 meter increments along the main transect line at the site. Each buddy pair ran an offshore and onshore transect collecting data on the abundance of different species of fish, invertebrates, and algae. Every individual collected their own data in order to account for variance later in the analysisof the data collected.The sampling involved 4 legs of a transect and divers were given a suite of plants, fish, and invertebrates to identify and qualify in terms of abundance. Two legs were offshore from the main line, and two were onshore. Data was collected on every leg and each individual diver ranked every species on the data set with a one to five, one being absent and five being abundant.
Data Analysis
After all the data was were amassed, we calculated the mean abundance of species.
To test for the source of greatest variance in the data collected, variance component analysis was done with respect to depth(i.e. offshore/onshore), buddy agreement, and meter mark.
In order to estimate the difference between buddy pairs, we graphed the percent relative difference between buddies based on rank data by taxa. We also graphed the percent disagreement on the presence or absence of a species between buddies by taxa.
Results
We found that the greatest variance in data was by meter mark 40% and buddy differences accounted for nearly 40% of variance(Fig. 1).
Fig. 1Fig. 2
When variance components were analyzed by taxa, we found that the meter mark contributed to the most variance for algae and fish, but invertebrates seemed to have a stable frequency in species abundance distribution. A confounding factor though for the variance in invertebrate data was that buddy discrepancy was accountable for half of the variance (Fig. 2).
The mean abundance of species based on ranked data showed that fish were rare and the most abundant species relative to algae were the giant kelps, M. pyriferaand C. osmundacea, and for the invertebrates, the bat star, P.miniata(Fig. 3).
Fig. 3
Looking at the relative percent difference between buddies based on rank shows us that there was a standard of about 50% difference between buddies. There were 8 out of 13 invertebrates though that were below this percent difference which shows that the buddies were in more agreement about their presence. (Fig. 4)
Fig. 4
We graphed the percent disagreement on the presence or absence of a species. The only two species found without disagreement between buddies in terms of their presence were M. pyrifera and P. miniata, which is consistent with fig. 3 (Fig. 5).
Fig 5
Graphing the relative difference between buddy pairs and mean abundance showed that buddies were generally in agreement about those that were most abundant and those that were absent. Most of the differences occurred in the area between rare and common occurences of species (Fig 6).
Fig. 6
Discussion
Buddy discrepancy in sampled data accounted for nearly 40% of variance in data (fig.1) which was second to the variance by meter mark. True variance by meter mark would indicate a very heterogeneous distribution and abundance, but the fact that variance by buddy accounted for such a high percentage of variance dissolves this initial thought, and requires further consideration. Variance analysis by taxa(fig. 2) shows that buddy teams were responsible for the most variance in data for algae and fish, but for invertebrates, there seemed to be a standard frequency in their distribution and abundance. This could be due to misidentification of invertebrates species between the individuals in buddy teams, or a disagreement in abundance. The mean abundance of species by taxa(fig. 3) show that all fish were uncommon, and that there were key species that were abundant at the site for the other taxa. The finding that fish were all fairly uncommon is reflective of the well known fact of a declining and low abundance of fish in the Monterey Bay. The percent relative difference between buddies showed that there was less of a relative difference in the species found with the greatest abundance, which supports the previous figure. Figure 5 also adds to this by showing the presence/absence data between buddies, which clearly indicates an agreement on the presence of species found with high mean abundance. This makes some of the data seem more reliable in that the variance was not accountable for some of the present species observed.
This qualitative study works well to a degree. It shows that some species are better used for qualitative studies than others, such as the presence and abundance of M. pyrifera, C. osmundacea, and P. miniata.These results showed that there was an abundance of giant kelps and bat stars which is very likely. It would not be good to rely on this sort of data for information on the density of less common species of algae, fish or invertebrates. A qualitative study like this would be more suited to studying sedentary or sessile invertebrates. The thing that makes for a good candidate in such a qualitative study is its high abundance,sessile lifestyle or easily identifiable nature, a combination of which would make it even better.Using a qualitative sampling method can be an appropriate method for determining the distribution and abundance of these species through time especially because of the natural standardizing effect that time would have on such a survey.
This study could be enhanced by defining a clearer ranking system where the relative abundance of a species can be more clearly stratified to a rank. Though the aptitude of every diver to identify a species may have been high, the data could have been skewed by the subjective nature of the ranking system, which becomes apparent in Figure 6. The presence or absence of a species is clear, but most of the difference in mean abundance occurred in the area between them.
This data could be useful over time to track a major disturbance effect that changes the community dynamic in this area, and could be significant in that respect. To further examine this ecosystem through a qualitative survey it would be important to conduct this study over a greater period of time and to further standardize the method of sampling. Qualitatively tracking the health of the giant canopy-forming kelp could definitely be useful, as it provides the habitat for the fish and invertebrates to thrive.
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