Download Rocky Intertidal Transect Survey

Rocky Intertidal Transect Survey
Remember that intertidal conditions at low tide are stress conditions for many organisms. It may be harder for
you to observe movement, feeding, or other behavior patterns because of the lack of water during extremely low
tides. Keep in mind that your period of observation will be extremely short in comparison to the length of the total
cycle that influences the physical factors of the intertidal. Even so, interesting and meaningful intertidal
observations can be accomplished in a relatively short period. The class will be divided into small groups of
students, with each group studying a separate transect of the intertidal zone. Each transect should extend
perpendicularly from the upper part of the splash zone to the water's edge. Each student group should follow these
general guidelines for studying their transect.
The purpose of this study is to obtain accurate population density estimates for about a dozen key intertidal
species along a narrow transect line, extending through the intertidal zones from the splash zone to the low tide
line. The information should be used as the basis for further discussions dealing with factors that affect the
distribution of intertidal organisms. Proper identification of the plant and animal species is necessary. The area to
be surveyed is determined by placing a 0.5 m X 0.5 m quadrat in successive positions along a selected transect.
Organisms living in a continuous strip of the intertidal zone, 0.5 m wide and perpendicular to the coastline, can be
counted.
1. Select about twelve "key species'' of plants and animals to census. Base your selections on the range of
distribution of the 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
transect line.
2. Extend your tape
measure perpendicular
to shore, beginning at
splash zone and
extending outwards
towards the ocean for
100 m. You need to sample TEN quadrat areas along the transect line. Based upon the length of the section,
the interval to the center of the next quadrat should be 10 m.
3. 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+”
4. Continue down towards the ocean until you have 10 quadrats from one transect.
5. At selected points along your transect, determine environmental conditions such as water temperature,
salinity, pH, dissolved oxygen concentration, and duration of exposure to air. Record the data on your data
sheet.
6. Collect as much information as you can relating to such factors as 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.
Name ____________________________________________________ Group __________________
Date:
Location:
Predicted Low tide:
2:43pm -1.8ft below sea level
Predicted High tide
7:49am 6.9ft above sea level
General weather conditions (sun, rain, ocean conditions):
2. Record the temperature and salinity of a sample of seawater taken at the water's edge. The salinity will be
determined by using a salinimeter. Use the kit to determine the dissolved oxygen content and the shared pH
meters to determine the pH of the seawater.
Temperature: __________
o
C Salinity: _______ o/oo
DO2: ___________
pH: ___________
Table 2. Dominant intertidal species found in transect #____ at ______________________ on _________
# 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
1.
2.
3.
4.
5.
6.
7.
8.
9.
10
11.
12.
DISCUSSION QUESTIONS: (to be answered on a separate paper, pen or typed, in detail.)
1. Discuss the general trends of distribution of intertidal plants in your study area.
2. Discuss the general trends of distribution of intertidal animals in your study area.
3. What apparent physical and biological factors can you suggest for these distributional patterns?
4. How many different methods of feeding by animals did you observe? Give examples of each.
5. Do you think the relative abundance of a particular species of plant or animal is necessarily proportional to its
ecological importance in the intertidal community? Give examples to support your statement.
6. Looking at the ABUNDANCE of dominant species at each station, the PHYSICAL FACTORS at work at
each station, the FOOD REQUIREMENTS, PREDATION and COMPETITIVE INFLUENCES at work at
each station, ANALYZE the reasons behind the particular species abundance and diversity found at each tidal
zone.