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Spatiotemporal chemical analysis of surface water and the effects of
precipitation in the pre-montane rainforest of Costa Rica
C.Culver1,3 , G.Moore2, K.Brumbelow3, G.Miller3, M.Zapata3, S.Chellam3
Bowling Green State University, Department of Life Sciences 1 ; Texas A&M University , Department of Ecosystems Science and Management2 , Texas A&M University , Department of Civil Engineering3
Hypothesis
The four sites should show some variation, in pH,
turbidity, dissolved oxygen, conductivity, and
temperature. The streams and rivers have different
structure and surroundings that contribute to its
chemistry. The precipitation should also decrease pH
and conductivity.
Figure 7: Stream beneath WeirFigure 8: Stream beneath waterfall
Figure 9: Chachagua River Figure 10: Penas Blancas RiverFigure 11: Deploying sonde
Results
Methods• Determined site location (to get variation in stream
type and appearance). Two streams and two rivers
were selected. Out of the two rivers one was large
and one was small. Out of the two streams one had
a waterfall, and the other had a weir construction
upstream.
• Programmed the YSI to collect unattended samples
every 30 minutes for 4 days
• Made note of qualitative data around sites
• Recorded latitude and longitude of site and took
pictures
• DO and Ph were calibrated in between each site
• Deployed the YSI instrument by securing to a
nearby rock or log with a rope in stream/river (made
certain it was fully submerged in the water).
Retrieved instrument, then moved to next site:
Dates of Data Collection
Site 1 6/16/19-6/19/19 Howler Monkey Stream/ Weir
Site 2 6/21/19-6/24/19 Stream beneath waterfall
Site 3 7/01/19-7/04/19 Chachagua River
Site 4 7/07/19-7/10/19 Penas Blancas River
Acknowledgements- Funding for this Research Experiences for Undergraduate
program is provided by the National Science Foundation’s
Division of Earth Sciences (EAR-1659848)-
Objective• Test dissolved oxygen (DO) ,pH, turbidity,
temperature, and conductivity at four different sites
for four days each
• Analyze precipitation patterns during the time period
the water was tested
Research Questions• Do streams that are in similar environments have
similar or different surface water chemistry?
• How does the precipitation in a rainforest climate
affect the surface water chemistry?
IntroductionWithin the pristine rainforest of San Isidro, Penas
Blancas region of Costa Rica many of the streams and
rivers have similar environmental surroundings. They all
have similar surrounding vegetation and air temperature
and are within the premontane area as well. This data
will give insight on surface water chemistry trends in the
rainforest.
Table 1- Relationship between DO and temperature at sunrise, and
sunset.
Conclusion
Contrary to the hypothesis, precipitation did not affect the pH and
conductivity. Despite the sites being in a rainforest; the amount of
rainfall was insufficient to cause any drastic changes. There were
some differences in DO, temperature, turbidity, and conductivity
between the sites which supports the hypothesis.
This data shows how different features and structural variations of
surface water can change their chemistry even if they are all in a
rainforest ecosystem.
This information can be useful with determining ideal areas to get
fresh water for human use (based on pH values). The varying
water chemistry can also support how much biodiversity the Costa
Rican premontane rainforest can sustain as well.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Discussion
• As temperature decreases, the maximum amount of dissolved
oxygen that water can be saturated with increases.(Table 1)
• Conductivity levels in the Penas Blancas river, are credited to
the volcanic rocks present in the river that increase ion
concentration.( Figure 1)
• Turbidity in the stream beneath the weir were significantly higher
than the other sites (Figure 2). So a log scale was needed to
combine the values on the same graph . Construction was going
on upstream which resulted in more debris flowing through the
water.
• The maximum amount of rainfall was only 34 mm (Figure 6)
so precipitation didn’t effect the water chemistry as expected.
Results Cont.
0.01
0.1
1
10
100
1000
Turb
idity
(NT
U)
Days
Daily Avg. Turbidity
Weir Waterfall Chachagua Penas Blancas
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
8
8.1
1 2 3 4
pH
Days
Daily Avg. pH
Weir Waterfall Chachagua Penas Blancas
7
7.5
8
8.5
9
9.5
10
10.5
11
11.5
12
1 2 3 4
DO
(m
g/L
)
Days
Daily Avg. Dissolved Oxygen
Weir Waterfall Chachagua Penas Blancas
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
0.11
0.12
0.13
0.14
0.15
1 2 3 4
Spcond (
mS
/cm
)
Days
Daily Avg. SpCond
Weir Waterfall Chachagua Penas Blancas
21
21.5
22
22.5
23
23.5
1 2 3 4
Tem
pera
ture
(°
C)
Days
Daily Avg. Temperature
Weir Waterfall Chachagua Penas Blancas
