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Qualitative assessment of the presence and distribution of species common to Monterey Bay
Hannah Perlkin
Abstract
A qualitative survey of 28 species common to the Monterey Bay kelp forest was done to assess the presence and distribution of the species while also assessing any limitations of the qualitative surveying method. The survey was conducted in order to ascertain which species are present and easily qualified. Data was collected based on observations with Cystoseira osmundacea, Macrocystis pyrifera, Pisaster giganteus and Patiria miniata recorded as the most abundant species present. The relative difference between buddies was a greater source of variance than depth and nearly as high a source of variance as the location of data collecting, suggesting that qualitative surveying is highly subjective.
Introduction
A qualitative survey of Hopkins Marine Laboratory was conducted in order to determine the presence and distributions of species common to Monterey Bay, California and to assess the accuracy of the survey method. This was done in order to ascertain information regarding unusual abundances of species present, species absent and the difficulty qualitatively assessing each species. Specifically, we sought to determine if qualitative surveying is an appropriate method of data collection given the distribution of species at Hopkins Marine Laboratory.
The accuracy of data collected was assessed since buddies differ in familiarity with the area and species, categorical definitions, presence/absence of a torch, additional work done (i.e. compass reading versus meter tape running). To determine the accuracy of the sampling method itself a comparative analysis of data between buddy pairs of the class as a whole was done.
Of the three categories sampled (fishes, algae, invertebrates) the latter two are assumed to be better candidates for qualitative sampling because of their (relatively) immobile nature. Unlike with fish, a researcher may approach an algae or invertebrate to determine its species, regardless of visibility.
Because variables other than definitive differences were present, an analysis of variance components was run in addition to an analysis of the relative difference between buddy pairs as a function of mean abundance of species.
Methods
Abundance
The qualitative study was preformed along the permanent cable at Hokpins Marine Laboratory. Each buddy pair was assigned a meter mark at which to run a meter tape out thirty meters both offshore (90 degrees) and onshore (270 degrees) while observationally assessing the presence abundance of species. Of the 28 species sampled were: 6 algae, 9 fishes and 13 invertebrates.
Of the 28 species sampled those with abundances categorized on average as 3 (present) to 4 (common) were the two algae, Cystoseria osmundacea and Macrocystis pyrifera, and one invertebrate, Pisaster giganteus. The single species categorized as common to abundant was Patiria miniata, the bat star. Of those four most abundant species each has a difference between buddy pairs of 20 to 25, which is relatively low, the exception being P.giganteus with a relative difference of 50 (Fig 1).
Figure 1
Qualitative Surveying
In order to express the relative abundance of each species the categories 1 (absent), 2 (rare), 3 (present), 4 (common) and 5 (abundant) were used to qualify each of the 28 species. In order to estimate the difference between buddy pairs, the survey was conducted without establishing guidelines for the categories, exaggerating the subjectivity of qualitative surveying.
Results
Abundance
Fish as a whole were consistently designated abundances between 1 (absent) and 2 (rare). Invertebrates had the widest range of quality designation, ranging from 1 (absent) to over 4 (common) (Fig 2). Of the 28 species sampled the four found to be most abundant were C. osmundacea, M. pyrifera, P. giganteus, and P. miniata. Each of these species had a relatively low relative difference between buddies (Fig 1).
Figure 2
Qualitative Surveying
The categories recorded least consistently amongst buddy pairs were 2 (rare) and 3 (present) (Fig 23) with 17 of the 28 species given ranks between 1.5 and 3 (Fig 32). Also, three of the species categorized as commonest C. osmundacea, M. pyrifera, P. and P. miniata had the lowest percent disagreement between buddies of all species (Fig 4).
Figure 3
Figure 4
Discussion
Of the 28 species sampled the four found to be most abundant (C. osmundacea, M. pyrifera, P. giganteus, and P. miniata) each species had a relatively low relative difference between buddies. This was likely due to these species’ characteristics as common, easily identifiable and familiar to the class. Within these species that were both common and recorded consistently, fish were not represented. Fish are harder than invertebrates or algae to identify due to a high level of mobility, limited visibility and possibly students’ lack of familiarity. Alternately, algae lends itself to qualitative sampling since it is often difficult to count but easy to assess abundance in general terms, easily identifiable and stationary.
The inconsistency within the categorical ranks 2 and 3 were not surprising given the high proportion of species recorded as rare or present. The designation of these labels was relative to any given diver’s experience in the area and knowledge of typical abundance at the sight, as well as in Monterey Bay at large. The term ‘present’ itself was misleading, since any numerical designation other than ‘1’ would imply the species was present.
By preforming an initial qualitative study, later quantitative studies could be planned in reference to a general understanding of species distribution gained from the initial survey. Hallacher and Roberts’ study on rockfish zonation likely was catalyzed by a casual qualitative observation of specie stratification (Hallacher & Roberts 1985). Appropriate sampling methods could be employed as well as additional tools used to aid in the specific circumstances of data collection. Any inconsistencies among researchers could be corrected before numerical data is collected. Consequently, doing an initial qualitatively survey could be costly in time and money. If all researchers are already familiar with the area, a qualitative survey might be redundant.
Over a long period of time, qualitative sampling has its merits. One, the general categories to describe species can be generally and specified appropriate to the species. For example, within 10 meters 0-5 C.costata is 2 (rare), 5-10 is a 3 (present), etc. This way a broad area could be sampled much more efficiently than by doing an accurate count while still allowing comparison for a temporal study. For Sala and Graham’s experiment on community-wide predator-prey interaction strength, a follow up observational study could be conducted using a qualitative model to describe adult distributions of herbivores and M.pyrifera (Sala & Graham 2002). This would allow for a less detailed, broader scale study, which is consistant with the study’s question: what are the maximum interaction strengths of eight common herbivores on the kelp M. pyrifera?
Whether data collection where categories stand in for general numerical ranges crosses the line into quantitative sampling is up to the scientists and reviewers. Given the vague, imprecise nature of the quantifying, it is possible this would still be a qualitative sampling method.
Works Cited
Hallacher, Leon E and Dale A. Roberts. 1985. Differential utilization of space and food by the onshore rockfishes (Scorpaenidae: Sebastes) of Carmel Bay, California.
Sala, Enric and Michael H. Graham. 2002. Community wide distribution of predator-
prey interaction strength in kelp forests.
Results (25)
__0__/4 Figure legends Accurate
__0__/4 Figure Legends well composed (complete and concise)
_5__/5 Results organized according to questions
__3__/4 Graphs presented in a logical order, case made for the order
__3__/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) __2__/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) __2__/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
__4__/5 Organization of discussion
__2__/3 Context and Bigger Picture
General Notes:
Figures always need legends to give the reader the details needed to interpret them. Good job on making subheadings for sections.