MORTALITY RATE
OF HERMIT CRABS (Coenobita
clypeatus)
AT DIFFERENT BLEACH
CONCENTRATIONS
STATEMENT OF THE PROBLEM
The aim of this study is to determine the effect of
bleach as a marine pollutant on Hermit Crabs in a
simulated beach environment. It seeks to answer the
following questions:
1) What are the mortality rates of the Hermit Crabs when
exposed to the following different bleach concentrations:
10 ppm;
100 ppm;
1000 ppm;
10,000 ppm?
2) Is there a significant difference among the mortality
rates of the Hermit Crabs exposed to different bleach
concentrations?
OBJECTIVES OF THE STUDY
1) To determine the mortality rates of the Hermit
Crabs exposed at different bleach concentrations.
2) To determine if there is a significant difference
among the mortality rates of the Hermit Crabs
exposed at different bleach concentrations.
HYPOTHESES OF THE STUDY
Ho: There is no significant difference among
the mortality rates of the Hermit Crabs exposed
at different bleach concentrations.
SIGNIFICANCE OF THE STUDY
There is a long history of the use of marine invertebrates as
indicators of the presence and intensity of pollution. Increased
abundance of the polychaete, capitella capitata, for example, has
been shown to indicate the presence of the antifouling agent.
(Dunbar, 2010)
This study would be beneficial to the researchers and the
citizens for they would acquire knowledge of the Hermit Crabs’
mortality rate at different bleach concentrations. This would be a
possible starter for the study of Hermit Crabs as marine pollutant
indicators, particularly of bleach. The population of Hermit Crabs
may be a basis of the concentrations of bleach in that particular
area. This may benefit the society, for they would know that their
disposal of marine pollutants like bleach might soon cause the
extinction of Hermit Crabs which are of great importance
ecologically, as they are scavengers, and at the same time, serve
as food sources for other animals. Hermit Crabs are also used by
researchers to study the effects of pollution and coastal changes
in wildlife.
SCOPE AND LIMITATIONS
The study of the mortality of Hermit Crabs at different bleach
concentrations focused on 5 set-ups which are the control, 10 ppm,
100 ppm, 1,000 ppm and 10,000 ppm, respectively. This study was
conducted in a simulated beach environment consist of an 8-inch
diameter basin. These basins were designed to simulate the beach
environment. With the simulated set-ups, the researchers were able
to check it everyday. This was more convenient and practical than
conducting the research in the seashore where they might not possibly
be able to observe it properly. The Hermit Crabs were fed by the
researchers twice a day, once in the morning and once in the evening,
as prescribed by most Hermit Crab pet owners. To verify if there is a
significant difference among the mortality rates of the Hermit Crabs
at different bleach concentrations, Analysis of Variance (ANOVA) was
conducted. The Hermit crabs’ species, weight, color, and age, as well
as the brand of commercial bleach were considered as extraneous
variables for this research. The entire conduct of this research is
within SY 2010-2011 at Initao, Misamis Oriental.
METHODOLOGY
A. Research Design
The research design used for the study of the
mortality of Hermit Crabs at different bleach
concentrations was Completely Randomized Design (CRD).
Five basins were designed to simulate the beach
environment with bleach concentrations, 0, 10 ppm, 100
ppm, 1,000 ppm and 10,000 ppm, respectively. The
researchers monitored the Hermit Crabs’ mortality rates
until LC50 in at least one set-up had been reached. A test
for the significant difference among the mortality rates of
the Hermit Crabs at different bleach concentrations was
the conducted.
B. Materials
• Bleach
• Beaker
• Hermit Crabs
• Feeds for the Hermit Crabs
• Seawater
• White Sand
• Stones
• 5 Basins (8-inch diameter each)
C. General Procedure
Gathering of Materials
Fifty Hermit Crabs from the seashore of Hapitanan, Initao,
Misamis Oriental, regardless of their specie, weight, color and age
were gathered. Commercial bleach and five basins with diameter
of 8 inches each were also purchased.
Preparing of Bleached Water Samples
Bleach concentrations for Set-up A, B, C, D, and E which are
0, 10 ppm, 100 ppm, 1,000 ppm and 10,000 ppm, respectively,
were prepared. This is thoroughly explained in the Table of
Concentrations in the Experimental Set-up. To get the ppm
concentration for each set-up, the amount of bleach was divided
by the amount of seawater, and then multiplied by 106, or
amount of solute
ppm concentration =
x
amount of solvent
106
Preparing the Improvised Hermit Crab Habitat
The set-up for each concentration included a basin to simulate the beach
environment. The set-up is represented by Figure 3.1.
Figure 3.1 Set-up for the Hermit Crabs to Simulate the Beach Environment
Figure 3.1 shows the set-up for the Hermit Crabs. The blue part of the figure
represents the seawater and bleach solution while the brown part represents the sand and
stones, and the red part represents the feeds of the Hermit Crabs which were available for
them twice a day. The basin is elevated a little on the sandy part so as to prevent it from
getting totally submerged and from being washed away. This serves as the land area where
Hermit Crabs usually stay.
Monitoring the Hermit Crabs’ Mortality Rate
The researchers determined the Hermit Crabs’ mortality rate through
observing it everyday until one set-up had five dead Hermit Crabs. This is also
known as LC50 or Lethal Concentration 50% common to toxicity tests. Dead
Hermit Crabs were determined when they did not move any longer and their
bodies lied limp out of their shell. When LC50 had been reached, the
experiment stopped.
Experimental Set-Up
Table 3.2 Components of Different Set-ups
Set-up
Amount of Sand
Amount of Feeds
Bleach (mL)
Seawater (mL)
A
160 mL
4 tbsp.
0 mL
200 mL
B
160 mL
4 tbsp.
0.002 mL
200 mL
C
160 mL
4 tbsp.
0.02 mL
200 mL
D
160 mL
4 tbsp.
0.2 mL
200 mL
E
160 mL
4 tbsp.
2 mL
200 mL
Table 3.2 shows the Components of Different Set-ups. For each set-up,
the amount of solute which is the bleach was divided by the amount of solvent
which is the seawater multiplied by 106 that then yield to their respective
concentration in terms of ppm. The amount of sand and feeds were also shown in
this table.
Instrument Used in Data Gathering
The researchers used the mortality rate, given by,
# of dead Hermit Crabs
% mortality =
x 100
total # of Hermit Crabs
as their instrument for data gathering.
Statistical Tools
To verify if there is a significant difference among the mortality rates of
the Hermit Crabs at different bleach concentrations, the Analysis of
Variance (ANOVA) was conducted by the researchers. Also, The Megastat
add-in from Microsoft Excel was used to calculate the ANOVA.
RESULTS AND DISCUSSION
The main problem of the study of
Hermit Crabs at different bleach
concentrations is to determine the
Hermit Crabs’ mortality rates at
different bleach concentrations and
verify if there is a significant difference
among the mortality rates of the Hermit
Crabs.
The
whole
course
of
experimentation for this study was
conducted on January 5, 2011 until
January 9, 2011 at Initao, Misamis
Oriental. The observation of the
mortality rate of the Hermit Crabs
stopped on the fourth day as LC50 had
been reached or 50% of the Hermit
Crabs of set-up E with 10,000 ppm, died.
The observation for the mortality rate of
Hermit Crabs stopped on the fourth day when 5
Hermit Crabs of set-up E, 10,000 ppm, died.
This is also known as LC50. At LC50, it was
observed that no Hermit Crab died on 0 ppm, 1
Hermit Crab on both 10 and 100 ppm and 3
Hermit Crabs on 1,000 ppm. With these data,
the researchers calculated for the Hermit Crabs’
mortality rate. Set-up A with 0%, B and C with
10%, D with 30% and E with 50% mortality.
To verify if there is a significant difference among
the mortality rates of Hermit Crabs at different bleach
concentrations, Analysis of Variance (ANOVA) in the
Megastat add-in from Microsoft Excel was conducted.
Since the F-statistics computed in the ANOVA table
is less than the F-table statistics or the P-value is lesser
than the alpha level of significance which is 0.05, then
the null hypothesis is rejected. That is, there is a
significant difference among the mortality rates of
Hermit Crabs at different bleach concentrations.
Furthermore, since there is a significant difference
among the mortality rates of the Hermit Crabs at
different bleach concentrations, Hermit Crabs too
could possibly serve as marine pollutant indicators,
particularly of bleach. Furthermore, the population of
Hermit Crabs may be a basis of the concentrations of
bleach in a particular area.
CONCLUSION
After the experiment had been done and data on the Hermit Crabs’
mortality rate at different bleach concentrations were statistically
analyzed, the researchers concluded that the presence of bleach affects
the mortality rates of Hermit Crabs. Also, higher concentrations of bleach
result to higher percentage of mortality rates of the Hermit Crabs.
According to the results of the ANOVA conducted, there is a significant
difference among the mortality rates of Hermit Crabs at different bleach
concentrations.
Since there is a significant difference
among the mortality rates of the Hermit
Crabs at different bleach concentrations,
Hermit Crabs too could possibly serve as
marine pollutant indicators, particularly
of bleach. Furthermore, the population of
Hermit Crabs may be a basis of the
concentrations of bleach in that particular
area.
RECOMMENDATION
The study of the mortality
of Hermit Crabs at different
bleach concentrations was
pursued by the researchers to
become a possible starter of
the study of Hermit Crabs as
marine pollutant indicators.
With this, the population of the
Hermit Crabs may be a basis of
the concentrations of bleach in
that particular area. Further
research could be done on the
Hermit Crabs’ mortality to
other
types
of
marine
pollutants.
FIN.
To God Be The Glory!