GOHS-AP ENVIRONMENTAL SCIENCE
Rocky Shores Intertidal Biodiversity Transect Survey
By Anne Maben, AP Science Coach, Los Angeles County Office of Education
Abstract
This study is designed to define the biotic and abiotic characteristics found in a rocky intertidal ecosystem; to observe interactions between select living organisms and between themselves and their environment, and analyze which environmental and competitive factors may influence the particular pattern of density, diversity or zonation found at your study site. The transect method and statistical analysis used for sampling population abundance and diversity in this activity is applicable to many and terrestrial habitats.
Objectives
1. Recognize the effects common physical factors have on rocky intertidal ecosystem.
2. Recognize the effects common chemical factors have on rocky intertidal ecosystems.
3. Become familiar with the dominant inhabitants of rocky shores.
4. Recognize the most obvious adaptations of marine organisms to desiccation and wave action.
5. Recognize vertical zonation in rocky intertidal communities.
6. Quantify biodiversity
7. Quantify abundance
Hypothesis- Predict for vertical zonation, biodiversity of each zone with high, medium, and low predictions. Include Hypothesis for abundance of key species
Introduction Background
Ecologists have been aware of vertical zonation in intertidal habitats since the early 1800’s, and noticed that organisms found between the high and low tide marks seemed to vary in a consistent way. For example, periwinkles might be found in the upper splash zone, gooseneck barnacles and mussels in the middle intertidal, and sea hares and octopus in the lowest levels. Even then, scientists were beginning to realize the strong influence that climate, ocean conditions and coastal geology had on living organisms and on where life became distributed along our coasts.
We will attempt to document this effect by running a transect line from high to low levels in the local intertidal habitat, and comparing abundances of the various species along that transect. A transect will be used because it is impossible to count every living and non-living thing in an ecosystem. Transects that are in a defined area and permanently established can allow comparison between seasons or years over time. The transect has to be big enough to accurately characterize the biotic and abiotic factors of the ecosystem and is determined by the living members in the ecosystem.
We will collect population density estimates for about a dozen key intertidal species, extending from dry rocks in the splash zone to partially covered pools in the low tide zone. Proper identification of the plant and animal species is critical. The information obtained should be used as the basis for further discussions dealing with the abiotic and biotic factors (and human influences) that affect the distribution and species diversity of intertidal organisms.
Materials – For each team of 8-10 students
● Field guides
● 1/4 m Quadrats
● Electronic probes (pH, Temperature. dissolved O2)
● 100m tape measure or marked nylon line
● Sharp eyes and minds plus a positive attitude!
Transect Procedure
1. Spend some initial time surveying the study site, looking for obvious bands of zonation and selecting the general area for your first transect. As a team, decide on about twelve “key species” of plants and animals to census. Not all organisms will be present in every zone – some will be specialists found only in the Splash zone, but will be there in obvious abundance – some will be present in all zones, such as small scavengers. Make sure you include at least one marine plant in each of the zones – they represent food available for grazers.
2. Make your selections based on the range of distribution of each species within the intertidal, its abundance, and ease of identification. Remember that many of these animals are small, often camouflaged, and may be hiding. Get down on your hands and knees for a closer look. Be sure to examine the undersides of rocks (please replace them in their original position), ledges, and even blades of algae when choosing which species are most dominant along your WHOLE selected transect line.
3. Use your field guides and test each other to make sure that everyone on the team can identify these organisms with equal accuracy.
4. Extending your rope perpendicular to shore, begin at splash zone and extending outwards towards the ocean for 100 m. You will need to sample TEN quadrat areas along the transect line. Secure your tape at either end. Based upon the length of the section, the interval to the next quadrate can be randomly placed, by throwing a small rock over your shoulder to establish where along the line you will begin your next transect square. Wherever it lands, place the beginning of your next quadrat in the same relative place along the transect.
5. Identify and count the individuals of each key species within the quadrat. If the number of individuals of a species is too large for convenient counting (over 100), put “100+”). Mark data in data table #1.
6. Continue down towards the ocean until you have 10 quadrats from one transect.
7. Collect as much information as you can relating to such factors as substrate (silt, small rocks, algae-covered boulders, etc.), food preferences, feeding behavior, and associations with other plants and animals, which may be helpful in understanding the role of the plant or animal in the intertidal community.
Temperature Procedure
● Record water temperature from representative quadrats within each of the four tidal zones with a centigrade thermometer and record your results on the data sheet.
Dissolved Oxygen and pH Procedures
● Follow the directions on the chemical test kits to determine the dissolved oxygen content and pH of your water sample. If you are using electronic probes, make sure they are properly calibrated before using and take your dissolved oxygen and pH measurements in the deepest area of the quadrat.
Salinity- Salinity is a measure of how much salt is dissolved in water. The average salinity of seawater for all Earth’s oceans is about 35 grams of dissolved salts per kilogram of seawater. This is shown as 35 parts per thousand, or 35‰. The symbol ‰ is read “permill.” It is similar to percent, but it refers to parts per thousand instead of parts per hundred. We have one probe for the group, share data.
Data/Observations
Once all the data had been collected, the team should first decide which quadrats fell within each tidal zone (ex: Quadrats 1 Splash zone; quadrats 2 +3 = High Tide Zone; quadrats 4 +5 + 6+ 7 = Mid Tide Zone; quadrats 8+ 9 + 10 = Low Tide Zone.) Add all the data from similar quadrats together and average the data by the number of quadrats sampled (Mid Tide Zone = 45 mussels, 68 mussels, 54 mussels, 66 mussels/4 = a mean of 58 mussels/ 1/4m quadrat.)
● Your teacher will pool the data from ALL teams, to decrease margins of error so to increase the accuracy of significant statements about abundance and diversity of species at the site.
● You will have to wait until everyone turns in their data and has a group discussion on the results before beginning final calculations and the creation of a lab report.
Organize the data you have collected from each zone into clearly understandable tables, graphs, or charts.
● Make sure all data tables and graphs are properly labeled, with date and location included.
● Decide whether you’re going to present your data by charting ALL DATA from station #1, ALL DATA
from station #2, etc. or show a comparison side by side – Distribution and Abundance of Species #1 at Stations #1, #2, #3, etc.
Calculations -Use the following equation to calculate the species diversity for combined transects within each zone
Simpson’s Diversity Indices
There is statistical testing for populations that do NOT follow a normal distribution (and this includes most populations in the wild.) These are called nonparametric statistics. Simpson’s Diversity Indices is a non-parametric statistical test commonly used by wildlife biologists to document differences between populations and show trends in communities over time. It is frequently used when describing differences between communities (or tidal zones.) The term ‘Simpson’s Diversity Index’ can actually refer to any one of 3 closely related indices.
Simpson’s Index (D) measures the probability that two individuals randomly selected from a sample will belong to the same species. It answers the question: if 2 individuals are taken at RANDOM from a community, what is the probability that they will be the SAME species?
The value of D ranges between 0 and 1
With this index, 0 represents infinite diversity and 1, no diversity. That is, the bigger the value of D, the lower the diversity. This is neither intuitive nor logical, so to get over this problem, D is often subtracted from 1 to give: WE WILL ALL USE 1-D
Simpson’s Index of Diversity 1 – D
The value of this index also ranges between 0 and 1, but now, the greater the value, the greater the sample diversity. This makes more sense. In this case, the index represents the probability that two individuals randomly selected from a sample will belong to DIFFERENT species.
Calculation ABUNDANCE- We will also calculate abundance of each species in each zone comparing between the 4 intertidal zones, looking at how homogeneous or heterogeneous the community structure within each zone seems to be. Divide the total number of each particular species by the total individuals of all species counted.
Analysis -You will be completing a formal report as a culminating task.
● Use the lab format and scoring guides we have given you.
● Everyone works on his or her own analysis and conclusion. This is the heart and soul of any report or survey.
● Once you’ve calculated the Diversity Index for each of the four intertidal zones, use your final answers to help substantiate your findings.
● Create 5 bar graphs; pH, DO, Temp, Salinity and Simpson Diversity 1-D. Use Splash, High, Mid and Low tidal zones. Paste your data into google sheets or Excel and make graphs to copy back into your lab report.
●
CONCLUSION- Develop arguments for and against your hypotheses and interpretations. Do not make generalized statements that are not based on your data, known facts, or reason. Be sure to relate your findings to other studies and cite those studies. Draw positive conclusions from your study whenever possible.
● First, summarize the data from tables and graphs in words to validate your arguments. This does not mean a parrot-like recitation of all the data when you’ve already given it in a table. It means: look at the data from the experiment for trends, refer to your actual data numbers to show a point. Don’t just use qualitative terms like: “Zone 1 had a larger amount.” Better said: Zone 1 had 33% less algae. You’ve taken the raw data, performed a calculation, and used it to underscore a trend.
● After you’ve summarized the data, decide which errors are relevant – which were so large as to invalidate the survey? How might have your observations affected your results? Analyze WHY you got the results you did … BE SCIENTIFIC ! THINK!!! This is your chance to show you understood the field study. If there are ways to improve on the procedure, mention them.
● Your data should be interpreted, critically evaluated, and compared to other group’s results as well as previous research. Whereas your data table and graphs present the “news,” the analysis section contains the “editorial.” In the analysis, examine the amount and possible sources of variability in your data, including experimental error.
● Examine your results for bias and evaluate its effect in data interpretation.
GOHS- APES- ROCKY INTERTIDAL SURVEY
DATA COLLECTION Data Collectors Names:
Transect # _____ Color
Location:
Dana Point Rocky Tide Pool
Date
March1, 2022
Predicted low tide (from tide chart):
2:45 pm -1.3ft
Tide level at beginning of survey:
-0.5 ft
Beginning Time
11:00
Ending Time
12:30
General weather conditions
Wave Height and Action:
Dominate Substrate at Temperature Salinity DO2: pH:
Splash Zone:
High Tide Zone:
Mid Tide Zone:
Low Tide Zone:
Sketch of Transect Area
Transect # _____COLOR________________
Team Member Names:______________________,______________________________,________________________,________________________________
Table 1. Dominant intertidal species found in transect
# of Organisms per Species
Name of Species QUAD
1 QUAD
2 QUAD
3 QUAD
4 QUAD
5 QUAD
6 QUAD
7 QUAD
8 QUAD
9 QUAD
10
Target Species XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX
Periwinkle snail
Hermit Crab
Mussels
Acorn Barnacle
Gooseneck Barnacle
Thatched Barnacle
Sea Anemone
Black Turban Snail
Sea Urchin
Brittle Star
Rough Limpet
Shore crab
Species of Concern XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX
Ochre Star
Black Abalone
Chiton
Plants by % XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX XXXXX
Sea lettuce
Surf grass
Red Coralline Algae
Rockweed
