Question

driving question: how do abiotic factors affect the marine ecosystems?
ocean acidification lab
ocean acidification has been occurring rapidly. the quickly acidifying ocean causes many different
problems for the marine life that dwell within it, from plankton and kelp all the way up through the food chain to
large predators like sharks and killer whales. changes to just a single species can throw the entire chain off
balance. as with humans, marine species can only handle certain ph levels. the optimal ph level of the ocean
is 8.2; with ph levels dropping to as low as 4.6, the oceans are really in trouble.
water samples taken from 6 different areas along the northwest coast of the united states are
available for you to test. each area contains a variety of marine life that will soon be affected if the ph level is
not optimal for the life residing there. the first step will be to test the ph levels of each water sample and
record it in the table. to do this:

1. submerge the ph probe in a sample and wait for the meter to finish equilibrating
2. rinse the probe with distilled water before moving on to the next sample
3. test each sample twice and calculate the mean of the 2 values

now you will test the levels of carbon dioxide in the water samples. to do this: put 10 drops of bromothymol
blue (btb) into each sample and mix thoroughly. btb is an indicator that will change color depending on the amount
of co₂ present in the sample. a yellow color indicates high levels of co₂ while a blue color indicates no co₂. a green
color indicates a level of co₂ that is more moderate.

location	ph 1	ph 2	mean ph	color	co₂ levels
south slough	6.5	6.55		green
sitka tribe	8.18	8.28		blue
ketchikan, alaska	8.27	8.29		blue
point conception	8.3	8.34		blue
la push, oregon	8.4	8.46		blue

1. draw a bar graph using the data you collected. make sure the graph has labels and titles for both axes!

color each bar yellow, blue, or green to reflect the level of co₂ detected using btb. the grid is 20 x 20.

1. identify the area/s that have the lowest ph levels.
2. based on what you have learned about ocean ph, identify the area/s you tested that have ph values within

the ideal range for urchins.

1. identify the area/s that have the highest co₂ levels.

otter storyline 2025

Explanation:

Sub - question 2:

Step1: Calculate mean pH for each location

• For Willapa Bay: $\text{Mean pH}=\frac{4.94 + 4.84}{2}=\frac{9.78}{2}=4.89$
• For South Slough: $\text{Mean pH}=\frac{6.5+6.55}{2}=\frac{13.05}{2}=6.525$
• For Sitka Tribe: $\text{Mean pH}=\frac{8.18 + 8.28}{2}=\frac{16.46}{2}=8.23$
• For Ketchikan, Alaska: $\text{Mean pH}=\frac{8.27+8.29}{2}=\frac{16.56}{2}=8.28$
• For Point Conception: $\text{Mean pH}=\frac{8.3 + 8.34}{2}=\frac{16.64}{2}=8.32$
• For La Push, Oregon: $\text{Mean pH}=\frac{8.4+8.46}{2}=\frac{16.86}{2}=8.43$

Step2: Compare mean pH values

Compare the mean pH values: $4.89$ (Willapa Bay), $6.525$ (South Slough), $8.23$ (Sitka Tribe), $8.28$ (Ketchikan, Alaska), $8.32$ (Point Conception), $8.43$ (La Push, Oregon). The smallest value is $4.89$ which corresponds to Willapa Bay.

Step1: Recall BTB color - $CO_2$ level relationship

BTB (bromothymol blue) color indicates $CO_2$ levels: yellow indicates high $CO_2$, green moderate, blue no (low) $CO_2$.

Step2: Identify location with yellow color

From the table, Willapa Bay has a yellow color, which indicates high $CO_2$ levels. Other locations have green or blue (South Slough - green, others - blue). So Willapa Bay has the highest $CO_2$ levels.

Answer:

Willapa Bay

Sub - question 4: