Increasing concentrations of carbon dioxide (CO2) in the atmosphere

I got to conclusion for 2nd question is as follows :

From the graph we can see that in 2500 the top upper 1000m will have the ph range from -0.4 to -0.8. At depth of 4000m we can see that the change is -0.2.

So going through the options:

1. The pH of the upper ocean will be less than 7.0.
This is interesting option, if the upper ocean range is <1000m we can see that the ph would definitely be less that 7.0 (if we take 7.7 as the
ph in 2100) but if it is 1000m the ph would be 7.3 (again taking 7.7). If we take the ph in 2100 as 7.8 we can see that at most the ph
would decrease to 7.0 in 2500. So, there is strong saying that it will be below 7.0, so, reject it.
2. The pH of the upper ocean will be greater than 7.5.
As explained above the ph will not be greater than 7.5, so, reject it.
3. The pH of the deep ocean will be 7.8 or less.
We can see that deep ocean is below 4000m so, by 2500 change will be -0.2. In 2010 it is expected to be 8.2. So, 8.2-0.2 = 8.0. Reject
this.
4. The pH of the deep ocean will be greater than 7.9.
As calculated above we can see that this is the possibility. Keep this option.
5. As compared to 2010, the amount of iron consumed by phytoplankton will have decreased by more than 30 percent.
Research suggests that a 0.3 decline in pH reduces phytoplankton iron consumption by about 15 percent - by 2500 it would decrease by
0.1 which would not decrease by 30%. Reject this

Considering all options we can say that option 4 is correct.

chetan2u and others, Please feel free to correct/add more points on top of this.­

Edit : Corrected the typo from 2010 to 2500 in point 5.

Q.1. Assuming that current trends will continue, for each of the following, select Projected if it is a long-term projection of the information provided, and otherwise select Not projected.

Let us check the relevant information.

(a) Decreased iron absorption by phytoplankton will contribute to increased extinctions of sea life.
The above info is directly available from lines - Research suggests that a 0.3 decline in pH reduces phytoplankton iron consumption by about 15 percent, slowing photosynthesis and impacting growth and reproduction. Comparable changes in the past correlated with massive extinctions of sea life.
So, 'Projected'.

(b) Increased iron absorption by phytoplankton will contribute to decreased oceanic CO2 concentrations.
'Increased iron absorption by phytoplankton' has not been linked to 'decreased oceanic CO2 concentrations' anywhere in the para.
So, 'Not Projected'.

(c) Increased atmospheric CO2 concentrations will contribute to decreased ocean water pH
The above info is again directly from the first few lines in the first para. - 'Increasing concentrations of carbon dioxide (CO2) in the atmosphere are making the oceans more acidic—in other words, lowering the pH of ocean water'.
So, 'Projected'.


Q.2. Assuming that current trends will continue, which one of the following projections about the year 2500 most accurately reflects the information in the passage and Long-Term Graph?
Since the para speaks about Upper and deep ocean, let us check the trend in these two regions

Upper Ocean: It is the top 1000 m. The pH in 2010 was 8.1 and, in 2500, is likely to be affected by an amount of -0.5 at 1000 m to -0.8 at top surface as per the long term graph. So, the pH should be anywhere between 8.1-0.8 and 8.1-0.5 or 7.3 and 7.6
(a) The pH of the upper ocean will be less than 7.0: The entire range is not a part. Hence, not true.
(b) The pH of the upper ocean will be greater than 7.5: The range 7.3 to 7.5 is not a part. Hence, not true.
(e) As compared to 2010, the amount of iron consumed by phytoplankton will have decreased by more than 30 percent: A decline of 0.3 results in decrease by 15%, so for a decrease of 30%, we are looking at a decline of more than 0.3*2 or 0.6 pH, but the range is 0.5 to 0.8.: Need not be true­

Deep Ocean: It is at depth of 4000 m and more. The pH in 2010 was 8.2 and, in 2500, is likely to be affected by an amount of -0.2 as per the long term graph. So, the pH should be about 8.2-0.2 or 8.0.
(c) The pH of the deep ocean will be 7.8 or less: Not true
(d) The pH of the deep ocean will be greater than 7.9: True

@akshay.sachdeva, nolounta, please look at the solution and get back if any query.
kirallight, there may be an issue in the last portion. We are not looking at 2010, but comparison of 2500 to 2010.

­Thank you for pointing out the correction. Corrected it. 

GMATNinja , KarishmaB

In Question-1, why is statement 1 "Decreased iron absorption by phytoplankton will contribute to increased extinctions of sea life." Projected?

The relevant portion from passage is "Research suggests that a 0.3 decline in pH reduces phytoplankton iron consumption by about 15 percent, slowing photosynthesis and impacting growth and reproduction. Comparable changes in the past correlated with massive extinctions of sea life."

The passage says that comparable changes in the past "CORRELATED" with massive extinctions of sea life. This does not mean that these extinctions were necessarily caused by reduced phytoplankton iron consumption. What's more, even if it happened in the past, is it really reasonable to project that this "correlation" will happen again in the future?­ Maybe all the species which could get extinct because of these changes, already became extinct.