Qualitative Sampling of Species Distribution in the Kelp Forest of Hopkins Marine Station

Qualitative Sampling of Species Distribution in the Kelp Forest of Hopkins Marine Station in Monterey, Ca

Talley Sagot

October 6, 2011

Abstract

Ecologists aim to classify the structural and functional relationships of particular organisms with each other and with their environment (Foster and Schiel, 1985). We chose the kelp forest system at Hopkins Marine Station to assess a qualitative method of inquiry in one of the worlds' most productive and diverse species rich ecosystems (Mann, 1973). The dense canopies at Hopkins Marine Station are mainly formed from the species of giant kelp, Macrocystis pyrifora, which provide food and shelter to a plethora of organisms. We used qualitative sampling methods to observe the distribution and abundance of 12 species of invertebrates, 9 species of fish, 5 species of kelp and one genus of surf grass. We assessed how precise samples collected using the qualitative method can be in quickly determining the presence, distribution, and abundance of species. Qualitative sampling method estimates varied with depth, individuals of a buddy pair, and specific meter mark along the transect line. The latter two having the highest variability associated with the estimates. Our results are not repeatable with any accuracy which leads us to conclude this method of inquiry is best used when repeatability is unnecessary. The qualitative sampling method suggests the most clear-cut estimates between buddies of species are the ones categorized as “absent” or “present”.

Introduction

The goal of ecology is the classification of the structural and functional relationships of particular organisms with each other and with their environment (Foster and Schiel, 1985). The study of species distribution and abundance is of interest to ecologists for a number of reasons. It can help us describe ecological processes that structure populations and communities. It is critical when assessing impacts of abiotic, biotic and anthropogenic factors (Raimondi, written communication). Species distribution and abundance can be a baseline for conservation and management of things like biodiversity, endangered species, migrations and biogeographic regions of dynamic systems (Cowen, 1982). Species distribution and abundance in kelp forest ecosystems is important because it can address the effects of these species with each other and with their surroundings.

To assess distribution and abundance we need to employ a method of unbiased inquiry, because bias affects accuracy, which can be faithfully repeated for precision. It must also follow clear guidelines which can be understood and used in the area of question. Guidelines help to attain repeatability and prevent bias (Raimondi, written communication). Two different methods of inquiry used to study species distribution and abundance are qualitative and quantitative.

Qualitative analysis is cheaper, faster and more flexible than quantitative analysis. However, statistical validity is difficult and findings are often an inadequate basis for scientific conclusion in the absence of numeric estimations like size, density, or mass (Moore, 2003). Alternatively, qualitative sampling methods estimate categories for measurements, such as 'rare' or 'abundant'. Qualitative analysis is a useful sampling technique when beginning to look for patterns, mechanisms and consequences (Raimondi, verbal communications) of a given ecosystem in a very short amount of time and with little resources (Moore, 2003). Quantitative analysis, on the other hand, provides a reliable, repeatable set of data for a more confident statistical presentation of findings (Moore, 2003). Quantitative findings may also be more accurately generalized to the broader population; whereas, qualitative data is not repeatable and therefore less reliable.

We explored the functionality of a qualitative method of inquiry in the kelp forest system at Hopkins Marine Station. The dense canopies at Hopkins Marine Station are mainly formed from the species of giant kelp Macrocystis pyrifora which provide food and shelter to a plethora of organisms. We used qualitative sampling methods to observe the distribution and abundance of 12 species of invertebrates, 9 species of fish, 5 species of kelp and one genus of surf grass. We assessed how precise samples collected using the qualitative method can be in determining distribution and abundance of species. We observed which species occurred in this area and the error associated with differences in estimates of distribution and abundance with depth and location along the 100 meter cable transect line at Hopkins Marine Reserve. We compared variation in estimates among buddy pairs at each meter site and depth to quantify the precision of qualitative sampling methods.

Methods

On September 27, 2011 we went to Hopkins Marine Station in Monterey, Ca. We did our qualitative survey on SCUBA along the permanent 100 meter cable transect line. Fourteen buddy pairs took four qualitative swaths of a separate meter site along the black cable to look at how precise qualitative sampling methods could be when used to assess some of the kelp forest species distribution. We collected individual qualitative estimations of twenty seven species of alga, invertebrates and fish at a designated meter mark along the black cable at Hopkins Reef. The first thirty meter transect, leg one (out) and two (in), was done at a 90degree heading off the deep side of the black cable at Hopkins Reef. The second thirty meter transect, leg three(out) and four(in) was done at a 270degree heading on the shallow side of the black cable at Hopkins Reef.

On each leg of the procedure, the following data were taken; time start, time finish, depth start, depth finish, and relative abundance of target species. The qualitative estimations were made using categories (absent, rare, present, common, abundant) to assess the abundance of target species. We then compared the precision of our estimates based on qualitative methods with those generated by using quantitative methods (Raimondi, written communication). Using variance component analysis in Excel we were able to combine class data and graph the variance in estimates of kelp forest species between depths, individuals of a buddy pair, and specific meter sites along the black cable transect line at Hopkins Reef.

We interpreted the variation in species abundance estimates between all buddy pairs by graphing the percent variance of differences at each meter site and depth to quantify the precision of qualitative sampling methods. This gave us the percent difference we could interpret as error in data collection relative to known spatial distributions and evaluate problems with qualitative sampling methods.

Results

We found that species estimates varied with depth, individuals of a buddy pair, and specific meter mark along the black cable transect line. The different depths produced the least amount of variance in estimates at around 23% variability. The individuals in a buddy pair had varied species estimations of distribution and abundances at about 37%variability. The specific meter site along the black cable transect line had the highest variance in estimates of 41%variability. The latter two having the highest variability associated with the estimates, as seen in Figure 1 (reference figures according to guidelines) statement (fig 1).

Figure 1. This figure shows the percentage of variation seen between estimates of species abundance in differing depths, individuals in a buddy pair, and locations along the black cable transect line.

The largest qualitative sampling variation in estimations of kelp forest species would be location along the black cable transect line and then between individuals in a buddy pair would come in at a close second.

Variability in estimations between depth, buddy or meter site depends highly on the taxa being assessed (Figure 2). Buddy variability in estimations is the lowest when assessing fish and highest when assessing invertebrates. There is no variability what so ever in the species distribution using qualitative methods according to the meter location along the black cable transect line.

Figure 2. The top graph on this figure shows the variance components by Algae. It shows that location along the black cable transect is the highest source of variability when assessing species distribution of algae, a little above 50. Depth is the smallest amount of variability at around 10 and buddy is a little below 40. The middle graph on this figure shows the variance components by Fish. Here location along the black cable transect is the highest source of variability when assessing species distribution of fish at around 60. Depth and buddy have much smaller variance at a little above and a little below 20. The bottom graph on this figure shows the variance components by Invertebrates. Buddy and depth sources are equal in variability but the location along the black cable transect has zero variability when assessing species distribution of invertebrates.

Variation in algae species estimates as a function of depth are relatively low which make it a good candidate for qualitative sampling. Species of fish vary the least between buddy pair estimations. This shows that fish are a good species candidate for qualitatively sampling methods. We are unable to assess invertebrate species estimate variation as a function of meter location because the buddy source and depth source have such high variance it is unclear as to what is really going on.

Figure 3. This figure shows that the lowest relative differences between buddies are made at the category 1-absent or the category 5-abundant. The categories 2-rare and 3-present have the highest relative difference in estimations between individuals in a buddy pair.

Discussion

Individuals of a buddy pair do differ in qualitative data collection scoring. This could be due to individual investigation or observational methods coupled with experience, disturbances along the transect line and the difference in estimations of what one individual might categorize a species compared to another individual.

When it comes to individuals of a buddy pair species estimate categories such as "present", "common" or "rare" may be more difficult to qualitatively survey due the inexact articulation between individuals. Difficulty defining the categories “present” in comparison to “common” will lead to varying qualitative estimation results. If a species is not seen at all there will be a similar assessment of that species distribution in both individuals of a buddy pair. If their definitions of “rare”, “present” or “common” differ there will be more variability in the similarity of estimations which make these species relatively poor for sampling species distribution using qualitative methods. Observations made with low buddy differences, as with fish, coupled with presence of the species in the system can characterize the level of poor or good species candidates for sampling with qualitative methods. Species that are either absent or abundant are better sampling candidates for qualitative methods because there will be less variability in estimates between individuals in a buddy pair. The qualitative sampling method data collected suggests the most precise estimates of species are the ones categorized as “absent” or “present”.

The data show that depth had the least amount of variance in estimations. There are obvious patterns of species distribution and abundance that vary with the depth due to the various influences by abiotic factors such as physical or chemical disturbances as well as biotic factors such as predation, competition and resource availability (Dayton, 1985). Qualitative sampling methods could work well to describe a general understanding of the distribution of species as a function of depth. It could not accurately describe an environment on the basis of strict repeatability because the data would be confounded by an individual’s experience of assessment.

Qualitative sampling methods, for general ecological purposes can be used to quickly determine the distribution and abundance of species as a function of location along the meter tape because there would be rocky substrate and then a patch of sand at which point many of the species were benthic creatures.

Quantitative data often takes a considerable amount of time and money. Qualitative methods of sampling would be appropriate when accuracy or repeatability isn’t needed and there are time and resource limitations. It is good for an efficient ecological survey and for surveillance programs (Moore, 2003) as long as it’s understood to be bias due to individual diving experience and inaccurate. Qualitative sampling methods are not precise but results are useful when precision is not necessary. I would suggest further examining this system through quantitative methods to find precise results of species distribution and abundance.

Good conclusion

References

Cowen, R. K., C. R. Agegian, and M. S. Foster. 1982. The maintenance of community structure in a central California giant kelp forest. J.Exp.Mar.Biol.Ecol. 64:189-201.

Dayton, P. K. 1985. Ecology of kelp communities. Ann.Rev. Ecol.Syst. 16:215-245.

Foster, M. S., and D. R. Schiel. 1985. The ecology of giant kelp forests in California: A community profile. U. S. Fish and Wildlife Service Biological Report 85 (7.2):1-152.

Mann, K.H. 1973. Seaweeds: their productivity and strategy for growth. Science 182: 975-981.

Moore, P.G. 2003. The kelp fauna of northeast Britain. III. Qualitative and quantitative ordinations, and the utility of a multivariate approach. Journal of Experimental Marine Biology and Ecology Volume 16, Issue 3, December 1974, Pages 257-300.

Results (25)

__0__/4 Figure legends Accurate

__0__/4 Figure Legends well composed (complete and concise)

__5__/5 Results organized according to questions

__4__/4 Graphs presented in a logical order, case made for the order

__4__/4 Grammar, sentence structure and spelling

__2__/4 Clarity and conciseness of writing

Discussion (25)

____/9 How well did they answer the questions they present in the Intro?

1)  __2__/3 Discuss the results from the specific to the general.

2)  __3__/3 Do these results surprise you? In other words, is the qualitative method more or less reliable than you thought it would be, and do you think that degree of reliability (which can be assessed based on relative difference between buddies) implies anything about accuracy?

3)  __3__/3 Do you think the qualitative sampling approach is appropriate for describing trends of species abundances through time? Explain your answer

__2__/3 Grammar and Spelling

__2__/2 General Thoughtfulness

__2__/3 Clarity and conciseness

__3__/5 Organization of discussion

__2__/3 Context and Bigger Picture

General Notes: Results cover the main points. Organization is good, but refer to guidelines on how to reference figures. Focus on being more concise and avoid the use of superfluous verbage, read it over and take out words that don’t add to the sentence.

Figures require legends. Refer to guidelines.