Qualitative Sampling
Kelp Forest Ecology 2011
First Field Study
Brittany Arvizu
#W1179141
University of California, Santa Cruz
Oct.2011
Abstract
A qualitative sampling survey is used to identify the abundance and distributions of
twenty common species in the kelp forest community. I ask whether this is the best sampling
method used for data collecting on species’ abundance. Our results shows that variance among
buddies is least for the collection on fish data. Qualitative sampling gives a precise
representation of fish in a kelp forest, and data varies most between buddies sampling algae and
invertebrates. I suggest that qualitative sampling is the best method used when looking for rare
species and quantitative sampling is best used for more abundant species.
Introduction
The behavior of marine fishes, invertebrates and algae provides valuable insight into the
distribution of prey species and strategies used for habitat partitioning. The ability of kelp forest
species to coexist is key to their success. This study was done in Monterey Bay, CA, where
seasonal upwelling leads to nutrient rich surface waters which provide the criteria for
phytoplankton blooms, leading to food for marine organisms ranging from invertebrates to
higher order predators. Knowing where a species lives can lead to knowledge of habitat and
prey utilization. This then leads to conservation efforts and fishery regulations to protect the
marine environment and keystone species. Data on species’ abundance and distribution can be
used in the future to see the changes in the behavior of species with changing climate.
This study took place at Hopkins Marine Reserve in Monterey, CA. Data collecting was
done by qualitative sampling. Different from quantitative sampling, there was no numeric value
recorded in regards to numbers of present species. Instead an observational scale from 1-5 (1
being absent and 5 being abundant) was employed by UCSC scientific divers sampling areas in
the kelp forest. This type of data collecting (done using SCUBA) is faster than quantifying each
of the 20 species we were looking for. However, recording the exact number for a given species
gives a more accurate representation of a system. We ask whether this is the best method to get a
true representation of species’ distributions. To analyze this, data from buddy pairs was
compared for similarity. The results suggest that the data, while not precise, can be accurate
enough to get a good starting point into more specific studies.
Our analysis suggests that qualitative sampling is best used for identifying the presence
or absence of a species. Both buddies are likely to similarly report that they did not see the
presence of a particular species, then to similarly report on the abundance of a present species.
The data recorded for fish species is more precise than that given for invertebrate and algae
species, meaning it varied least between and among buddies. In this study, the data on fish does
not give an accurate description of their habitat, due to mobility. Qualitative sampling is not the
best method for determining the abundance of invertebrate species, which were usually spotted,
but buddy pairs differed significantly in their perception of a species being rare, present,
common or abundant. Therefore, rarity may imply more accurate data in this study.
Methods
To determine the abundance and distribution of twenty common species of the kelp forest
community, fourteen buddy pairs collected data using SCUBA off the permanent, meter-marked
cable attached to a buoy in at Hopkins. We collected data on species abundance at fourteen
different zones. For each of the twenty species we recorded a number 1-5 which represent the
following, 1=absent, 2=rare, 3=present, 4=common and 5=abundant. To understand the
differences in distribution from the shallow to deeper water, we collected data 30 meters out
(deep) from the cable and 30 meters in (shallow). The compass headings are 90 degrees (east)
from the cable and 270 (west) from the cable. At the designated meter-mark, my buddy reeled
out a meter tape 30 meters while we both qualitatively assessed the environment. On the return,
I reeled in the tape while we both, again, evaluated species and their frequency of occurrence.
Twenty eight students did the same procedure at fourteen meter marks on the cable ranging from
80-145m. To understand the depth differences at which species are found and the speed at which
data was collected, we also recorded start/end time and start/end depth for each leg of the
procedure. Buddies were told to not share data or to pre-determine their perception of the scale
used.
In order to estimate the differences in buddy pairs, all data was uploaded onto a Microsoft
Excel spreadsheet. The percent variance among the fourteen zones for depth, buddy and meter
mark were calculated and represented on a graph in Microsoft PowerPoint. The percentage of
variance between algae, fishes and invertebrates were also analyzed between buddy pairs, depths
and meter marks.
Results
The following graph (Fig. 1) shows the percentage of variance between depth, buddies
and meter marks. Just give me the result, followed by the reference to the figure. This is the
percent of difference in data regarding species abundance between; shallow and deep sides of the
cable, one buddy from their partner, and buddy pairs along the permanent cable this should be
described in the methods….give me the result here. The variance between the shallow and deep
side of the cable (25%) is less than that between each buddy (about 38%) and the meter mark
along the cable (about 43%).
Fig. 1. Variance (%) associated with three sources
The following graph (Fig. 2) shows the percentage of variance by taxonomic group. This
is the percent of difference between each buddy, depth and meter mark for algae, fish and
invertebrates. There is much less variance between buddies in regards to fish data (15%) than
that of algae (38%) or invertebrates (50%). Algae and fish data varies greatly between meter
marks, but invertebrates show little to no variance in abundance along the cable.
70
60
Algae
50
40
30
20
10
0
Buddy
Depth
Meter
Source
70
60
Fish
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40
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Buddy
Depth
Meter
Source
70
Invertebrates
60
50
40
30
20
10
0
Buddy
Depth
Meter
Source
Fig. 2 Variance by Taxonomic Group
The following graphs (Fig.3) show mean abundance recorded for all species; fish, algae
and invertebrates. Fish were overall less abundant than both algae and invertebrates.
Fishes
5
4
4
Mean Abundance
5
3
2
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Invert
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Fig. 3 Mean Abundance (±SE) for all Species
This last graph (Fig.4) shows the relative percent difference between buddy pairs as a
function of mean abundance of species. At the far left end, number 1 (not present), showed little
to no disagreement between buddies. The variance peaks in the center and is again low on the
far right end at number 5 (abundant).
Fig. 5 Difference between Buddy Pairs
Discussion
I expected the data collected along different parts of the permanent cable to be different,
which it was. This is because the ocean terrain at Hopkins varies from sandy and rocky bottom
to kelp forest and reef. This result is shown in Fig. 1. The variance among two buddies working
together is higher than I expected, as seen in Fig. 2. However, there is more agreement between
buddies regarding fish data than that of other taxonomic groups, due to the rareness of these
species compared to invertebrates and algae. This can be justified by Fig. 3 which shows that
there were less fish present than other species. Lastly, looking at Fig. 5, validates my conclusion
that the rarity of a species can lead to better (less varied) data in this study. Good points, but you
do not need to refer to the figures in the discussion.
I conclude that qualitatively sampling for abundance of species works best for collecting
data on rare marine species in Monterey, CA (only in Monterey? Why?). The more common a
species, the more difficult it can be to record data on abundance. For this study, quantitative
sampling would have given the best representation for algae and invertebrates, because they were
present at each meter mark and spotted in higher numbers than fish (do your results suggest that
QUANTITATIVE is better or worse? ). The results seem to be most precise for the fish data. If
the study was replicated, similar results can be expected regarding the absence or presence of
species. Although precise, the fish data cannot be said to be accurate. The data probably does
not represent the distributions of fish in the environment because they are mobile and can easily
move from one meter mark to the next. Algae and invertebrates are more sessile and can
therefore be easily quantified. Data on species’ abundance and distribution can be used in the
future to see the changes in the behavior of species with changing climate. But how does
qualitative work for this???
Results (25)
__3__/4 Figure legends Accurate
___2_/4 Figure Legends well composed (complete and concise)
__4__/5 Results organized according to questions
_2___/4 Graphs presented in a logical order, case made for the order
_3___/4 Grammar, sentence structure and spelling
__3__/4 Clarity and conciseness of writing
Discussion (25)
____/9 How well did they answer the questions they present in the Intro?
1) __1__/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) __0__/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
__1__/2 General Thoughtfulness
__3__/3 Clarity and conciseness
__4__/5 Organization of discussion
__1__/3 Context and Bigger Picture
General Notes: Use logical linkages in the results to indicate why you included each analysis. Review
guidelines on referenceing figures. Typically you do not refer to figures in the discussion, unless there is
a good reason for it.