The Effectiveness of a Qualitative Study on Species Abundance in a Kelp Forest

Leslie Hart

The effectiveness of a qualitative study on species abundance in a kelp forest

Title: 4 pts

Abstract [0, 0, 2, 2, 2, 2] 8 pts

The distribution and abundance of species can be sampled either qualitatively or quantitatively. A qualitative field survey was performed using SCUBA in a kelp forest habitat at Hopkins Marine Station in Pacific Grove, California. [why??? questions??] Buddy pairs collected species abundance data on fish, algae, and invertebrates along a 30-meter transect. This These data was WERE analyzed to determine the presence of differences in buddy pairs’ sampling [why?] and which species functioned as good or poor candidates for sampling using qualitative methods. The results revealed a high relative percentage difference between buddy pairs indicating that qualitative sampling is not the most efficient a very precise (i.e. repeatable) way to sample species abundance.

Introduction [2, 4, 4, 0, 2, 2, 2, 0, 4, 2, 2] 24 pts Determining the distribution and abundances of species is important because factors including recruitment, competition, extinction, invasive species, El Niño events, and variation of sea levels may significantly alter species population and this these data allows researchers to understand how these factors affect species coexistence in a given environment (Watanabe 1984). For example, a study conducted in Santa Barbara showed the regime shift after two storms changed the abundances in kelp and urchins (Ebeling et.al. 1985). By studying species distribution and abundances, scientists gain understanding and are able to recognize changes in biodiversity whether these changes are derived from natural or anthropogenic events. Other than understanding that distribution patterns can change seasonally or in response to resource availability, we can understand how greater ecological processes affect species diversity or abundance. In this study, the abundance of selected species at a kelp forest was qualitatively sampled. There are two methods of sampling species abundances: qualitative or quantitative. Qualitative sampling is subjective and consists of non-numeric estimates while quantitative sampling is objective using numeric estimates. The main advantage for qualitative sampling is that it requires less time than quantitative sampling. A researcher’s background controls how he or she decides to investigate and the angle of investigation. This background is developed from preconceptions, which are previous experiences, prestudy beliefs about an environment and what is to be investigated or perspectives relating to education or interests (Malterud 2001). Qualitative sampling depends heavily on the researcher’s background. Background is the backbone of how the qualitative researcher interprets the survey or study. This qualitative field study was conducted to understand the abundance of the target species in the kelp forest habitat. [no… to assess the precision applicability of quantitative sampling] The difference in buddy pair sampling was addressed. [why?] Certain species were either determined to be relatively good or poor candidates for sampling using qualitative methods through analyzing the results of the buddy pairs’ percentage difference of species abundance. A qualitative sampling may not be appropriate for describing trends of species abundances through time.

Methods [2, 0, 0, 4, 2, 2, 2, 0, 0, 2, 0, 2, 2, 2, 2, 2] 24 pts

First describe the general approach of the study

The Study System This qualitative study was performed in September 2011 at Hopkins Marine Station in Pacific Grove, California on the Monterey Peninsula (Figure 1). The environment was a rich kelp forest, inhabited by numerous species of algae, fishes, and invertebrates. The ocean conditions were calm with a slight surge. Species of interest in regards to this study were considered target species. There were five different species of algae observed: the chain bladder kelp (Cystoseira osmundacea), Turkish towel (Chondracanthus corymbiferus), Dictyoneurum californicum, giant kelp (Macrocystis pyrifera), and Dictyoneuropsis reticulata. The single seagrass species was Phyllospadix ssp. The various fish species that were accounted for include: the painted greenling (Oxylebius pictus), kelp greenling (Hexagrammos 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 pile perch (Damalichthys vacca). The species of invertebrates consisted of: bat star, (Patiria miniata), sun star (Pycnopodia helianthoides), short spined star (Pisaster brevispinus), great spined star (Pisaster giganteus), fish eating anemone (Urticina picivora), white-spotted rose anemone (Urticina lofotensis), sand anemone (Pachycerianthus fimbriatus), orange cup coral (Balanophyllia elegans), orange puffball sponge (Tethya aurantia), ring topped snail (Calliostoma ligatum), sheep crab (Loxorhynchus grandis), red abalone (Haliotis rufescens), and red urchin (Strongylocentrotus fransiscanus).

Specific Questions [give separate subheadings for each of your questions!!] In order to estimate the differences between buddy pairs, we conducted [first person when you can] a qualitative survey occurred on the deep and shallow sides of the black cable at Hopkins Reef and percentages of the relative differences and percentage of disagreement between buddies were determined. The black cable ran from east to west with eyebolts at every 10 meters. Each buddy pair, 14 total, was assigned a meter number that were each 5 meters apart. Using SCUBA, the deep side (offshore) was examined first. One person reeled out the meter tape with a 90 degree heading from the cable and both researchers collected the target species abundances for 30 meters. The buddies stayed within two meters of each other. At the end of the transect, the pair turned around and recorded data on the way back to the cable while reeling in the meter tape. This procedure was then repeated on the shallow side (onshore), with a 270 degree heading. The relative abundance of target species was evaluated using the following categories: 1=absent, 2=rare, 3=present, 4=common, and 5=abundant. The depth at the deep and shallow sides of the cable was recorded at the start and end of each transect. To confirm if there were differences between buddy pairs or which species were good or poor candidates for sampling using qualitative methods, several percentages were obtained. Based on the rank data from 1-5 for each species, we calculated the percentage of the relative difference between buddy pairs was calculated. In order to determine… we also calculated Also, the percentage of disagreement between buddy pairs was calculated. In other words, the percentage of disagreement between buddies marking species as present (ranks 2 through 5) or absent (rank 1) was determined. The percentage of the relative differences between buddy pairs as a function of mean abundance of species was calculated. A variance components analysis was done in order to show the percent variance associated with depth, buddies, and the meter mark.

Results The relative difference in abundance for fishes, algae, and invertebrates between buddies based on the qualitative rank from 1-5 showed that the fish with the highest percent difference was the black surfperch (E. jacksoni), while the black and yellow rockfish (S. chrysomelas), had the lowest percentage. Both D. californicum and D. reticulata had the highest percentages of disagreement within the algae data and giant kelp, M. pyrifera, obtained the lowest. For the invertebrates, orange cup coral (B. elegans), and the sand anemone (P. fimbriatus), had the highest percentages while the red abalone (H. rufescens), the red urchin (S. fransiscanus), and the white-spotted anemone (U. lofotensis), had the lowest percentages (Figure 2). In regards to the presence or absence of species, the highest percentage of disagreement between buddies for fish was for the striped surfperch, E. lateralis, and the lowest percentage was for the black and yellow rockfish with 10%. Overall, all the fish species excluding the black and yellow rockfish are at least 25% or higher in their percent disagreement. Through analyzing the algae, we found that the highest disagreement percentages were found with D. californicum and D. reticulata. The lowest percentage was giant kelp, M. pyrifera. For the invertebrates, the sand anemone has the highest percentage and the bat star, P. miniata, has the lowest (Figure 3). The relative difference in percentage between buddy pairs as a function of mean abundance of species indicates that the highest difference in the ranking numbers used was between 1 and 3. The numbers 1 and 5 have 0% difference (Figure 4). The variance components analysis depicts that the meter mark obtained the highest percentage of variation while depth had the lowest. The percentage of the buddy pairs followed closely behind the meter mark percentage (Figure 5).

Discussion

Buddy pairs were found to have significant differences in their sampling. Reasons for this difference when sampling fish could be that it is difficult for buddy pairs to identify species considering they move quickly and can swim in three dimensions. These factors may have resulted in one buddy seeing a fish before it swam away, leaving the other buddy to miss it. Because the black and yellow rockfish obtained the lowest percentage of relative difference in abundance, it may have been easier for buddy pairs to identify this species since it carries such a distinct color and pattern. It can potentially demonstrate a good candidate for sampling qualitative methods because it is easily identified. The striped surfperch on the other hand had the highest percentage of relative difference in abundance, meaning that it there might have been a greater challenge in identifying the species. Overall, since fish have the ability to swim making them harder to count, they had higher percent disagreement between buddies in comparison with algae and invertebrates. The highest percentages of relative difference between buddies for algae proved to be the very similar species of D. californicum and D. reticulata. Both of these species could have been very difficult for buddy pairs to differentiate between; the only difference between them is that D. reticulata has a midrib present while D. californicum does not. The two species similarities also contributed to a high disagreement percentage between buddy pairs, which shows a weakness in the buddies’ ability to identify these algal species. Both of these species demonstrate poor candidates for sampling qualitative methods since identifying them would require closer analyzing and more familiarity. M. pyrifera and C. osmundacea had low percentages of relative difference due to the buddies familiarity with both species, making them good candidates for qualitative sampling. The buddy pairs’ familiarity to these species is confirmed considering M. pyrifera and C. osmundacea both have a very low disagreement percentage between buddies. The percent difference in abundance for orange cup corals and sand anemones may be higher than the rest of the invertebrates because both species occur in high densities. Thus, deciphering between the rankings 4 (common) and 5 (abundant) may have been difficult for buddy pairs. The red urchin and red abalone may have had low percentages of relative differences between buddies since both species are often found hiding in cracks and crevices for protection, which makes them harder to detect. Their abundances may have depended on how thorough a search was made between buddies to find them; one buddy could have looked more intently in cracks and crevices than the other. The red urchin and red abalone seemed to be relatively poor candidates for qualitative sampling since searching for them requires a great effort. The bat star had the lowest disagreement percent between buddies because they were easily identifiable and obviously abundant. Most buddy pairs faced the greatest challenge in determining the qualitative rank for the mean abundance of species among categories 1 to 3 (absent, rare, and present). Divers within the buddy pairs most likely developed different definitions for each of these categories, making it no surprise that the differences were so extreme. The jump from absent to rare turns out to be significant; if only one buddy saw one black and yellow rockfish and the other did not, the black and yellow rockfish would be considered absent in the eyes of one buddy and rare in eyes of the other. Determining the differences between rare and present and present and common was based on personal inference, therefore, it was highly unlikely that buddy pairs would always agree. The categories of 4 and 5, with lower mean abundance differences between buddy pairs, were more manageable for buddies to agree on since the definitions for common and abundant may have not varied as much. The variance components analysis supported the fact that buddy pairs had significant differences in data collection with a percentage of variance just below 40%. This indicates that the researchers’ preconceptions were a considerable factor in determining the mean abundance in species. Students who are more familiar or experienced with species will have a different outlook on qualitative surveys than student who have less experience. Overall, the results indicate that the qualitative method is unreliable for a study on various species abundances. Qualitative surveys require set guidelines and planning before being performed. They must account for any questions that may come up before the study is in progress and have an answer to them in order to run smoothly and efficiently. The buddy pairs did not converse with each other before the dive about how they would give ranks for the species abundance. Therefore, the personal backgrounds of the individual researchers were the determining factor when the data was accounted for. Since the qualitative method proved to be unreliable, the level of accuracy in this study is low. The data was not very accurate considering the qualitative survey did not have quantifying guidelines. The qualitative sampling approach is not appropriate for describing trends of species abundances through time because it is subjective. Every person may not entirely understand the definitions given to describe the collected data; data illustrated through numbers and statistics can have a greater meaning and significance. It is easier to see differences in species abundances through numbers than interpreting the abundances through words. It is expected that depth or meter marks can be significantly different enough to cause discrepancies in data, but there should be no exception for having such a large discrepancy between buddy pairs. For measuring species abundances in a kelp forest, a quantitative study would have been more reliable and accurate than a qualitative study. Figures and Graphs

Figure 1. Hopkins Marine Station. Black cable is outlined with meter marks Figure 2. Shows the percentage of relative abundance difference for fishes, algae, and invertebrates between buddy pairs based on rank data (1-5).

Figure 3. Illustrates the percent disagreement of whether a species was marked absent or present between buddy pairs. Disagreement percentages were determined for fishes, algae, and invertebrates. Figure 4. Indicates the relative difference in percentages between buddy pairs as a function of mean abundance of species. The highest differences between buddies occurred between rankings 1 and 3 for the mean abundances.

Figure 5. The variance components analysis demonstrates the percent variance associated with depth, buddy pairs, and the meter marks. These are three factors that influenced the qualitative sampling for each buddy pair.

References [1, 2] = 3 pts

Ebeling, A.W., D.R. Laur and R.J. Rowley.: 1985. Severe storm disturbances and reversal of community structure in a southern California kelp forest. Marine Biology 84, 287-294 (1985)

Malterud, K.: 2001. Qualitative research: standards, challenges, and guidelines. The Lancet 358 (2001)pages???

Watanabe, J.M. : 1984. The influence of recruitment, competition, and benthic predation on spatial distributions of three species of kelp forest gastropods (Trochidae: Tegula). Ecology 63(3), :920-936. (1984)