Kojima 1
Caylin Kojima
The Effect of Temperature and Salinity on Abundance and
Biodiversity at Tidepools of Puako, Hawaii
Background:
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The gravitational pull of the moon, sun, and Earth interact. The oceans, being fluid, can
actually be pulled toward the moon. This creates the tide. The Earth itself is also pulled
toward the moon. The ocean is stretched thin by this pull. High tides are in line with the
moon while low tides are perpendicular to it. When the sun and moon are in alignment, the
sun enhances the moon’s gravitational pull, creating higher than normal tides (spring tides).
When at a right angle to the moon, the sun diminishes the moon’s pull, creating lower than
normal tides (neap tides). Because of the movement of both the moon and Earth, there is a
constant movement from high tide to low tide.
Tidepools are puddles of area left when the tide recedes, typically found on rocky coastlines.
They vary in shape and size. The environment in tidepools constantly changes due to being
cut off from ocean water.
Salinity is the saltiness or dissolved content of a body of water. It is an important parameter
for living systems due to its effect on the chemistry of natural waters and the biological
processes within it. This both limits and defines the ecosystem in which specific organisms
can live.
Temperature is also an important parameter for living systems as it, like salinity, limits and
defines which organisms can and cannot survive in the affected ecosystem. Additionally,
temperature impacts the availability of dissolved materials for living systems.
Methods:
Materials
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Hach multimeter
Hawai`i's Sea Creatures: A Guide to Hawai`i's Marine Invertebrates by John P. Hoover
Rope (1 m length)
Cameras
Sample bottles
Distilled water
Procedure
1)
2)
3)
4)
Select 3 tidepools of varying distance from the shore
Estimate & record number of strides from tidepool to shore
Use sample bottle to collect water from tidepool
Using multimeter to measure & record temperature and salinity (rinse with
distilled water between samples)
5) Tie rope into hoop
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6) Place gently onto surface of water
7) Count and identify (with guide) organisms within sample size/parameters of
rope
8) Repeat with number of trials allowed by tidepool size
Results:
Table 1. Tidepool Data
Tidepool
Location (strides
from shore)
Salinity (ppt)
Temperature (F)
A
15
34.8
85.4
B
C
37
68
21.5
5.5
85.8
87.0
Table 2. Number of critters per unit area (abundance)
Tidepool
Sample One
Sample Two
A
B
C
138
97
64
107
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Table 3. Number of types of critters per unit area (biodiversity)
Tidepool
Sample One
Sample Two
A
6
6
B
C
4
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Tripeneustes gratilla
Echinometra lucunter
Ophiocoma erinaceus
Calcinus laevimanus
Calcinus seurati
Mohoua novaeseelandiae
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Gobiidae
Calcinus laevimanus
Mohoua novaeseelandiae
Brachidontes crebristriatus
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Nerita polita
Grapsus tenuicrustatus
Mohoua novaeseelandiae
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Calcinus laevimanus
Mohoua novaeseelandiae
Tripeneustes gratilla
Echinometra lucunter
Purse scallop (?)
Haumea juddi
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3
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Kojima 3
40
35
30
25
20
Salinity (ppt)
15
10
5
0
Tidepool A
Tidepool B
Tidepool C
Figure 1. Average salinity for all tidepools
87.5
87
86.5
86
Temperature (F)
85.5
85
84.5
Tidepool A
(34.8 ppt)
Tidepool B
(21.5 ppt)
Tidepool C
(5.5 ppt)
Figure 2. Average temperature for all tidepools
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140
120
100
80
Number of organisms
per unit area
60
40
20
0
Tidepool A
(34.8 ppt)
Tidepool B
(21.5 ppt)
Tidepool C (5.5
ppt)
Figure 3. Average abundance in all tidepools
7
6
5
4
Number of types of
organisms per unit area
3
2
1
0
Tidepool A
(34.8 ppt)
Tidepool B
(21.5 ppt)
Tidepool C
(5.5 ppt)
Figure 4. Average biodiversity in all tidepools
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Discussion
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The further from shore the tidepool was, the smaller it was in dimension and volume.
Tidepool A was closest to the ocean and by far the largest (15x15 strides), Tidepool B was
smaller in size (10x10 strides), and Tidepool C, furthest from the shore, was the smallest
(4x4 strides).
Tidepool A was closest to shore and therefore higher in salinity (34.8 ppt). Because of its
proximity to the ocean, the ecosystem was relatively similar to that of the ocean, much more
than those of B (21.5 ppt) and C (5.5 ppt), which were greater distances away.
Further from the ocean, tidepools receive water from a freshwater source. With greater
exposure to the sun and no source of cold seawater at low-tide, tidepool temperature
increases as you get further from shore.
Tidepool A, while having the highest salinity (34.8 ppt), had an average abundance of 122.5
critters and 6 types of critters per unit area. Tidepool B with a lower salinity (21.5 ppt)
hosted 4 types of organisms with an abundance of 97. Lastly, Tidepool C had an extremely
low level of salinity (5.5 ppt) with an abundance of 64 and a biodiversity count of 3 types of
organisms.
As distance from shore increases, salinity decreases and temperature increases. Higher
salinity and lower temperatures allows for higher abundance and biodiversity in the
tidepool.