Question

average nitrate and phosphate concentrations in seawater after volcanic eruption
nutrient seawater in lava - affected area, 5 - 45 meters below surface seawater in lava - affected area, 75 - 125 meters below surface seawater outside of lava - affected area, 5 - 45 meters below surface seawater outside of lava - affected area, 75 - 125 meters below surface
nitrate (micromoles per liter) 3.1 0.4 ≤ 0.03 ≤ 0.01
phosphate (micromoles per liter) 0.17 0.09 0.14 0.06
after a volcanic eruption spilled lava into north pacific ocean waters, a dramatic increase of diatoms (a kind of phytoplankton) near the surface occurred. scientists assumed the diatoms were thriving on nutrients such as phosphate from the lava, but analysis showed these nutrients werent present near the surface in forms diatoms can consume. however, there was an abundance of usable nitrate, a nutrient usually found in much deeper water and almost never found in lava. microbial oceanographer sonya dyhrman and colleagues believe that as the lava plunged nearly 300 meters below the surface it dislodged pockets of this nutrient, releasing it to float upward, given that ____
which choice most effectively uses data from the table to complete the statement?
choose 1 answer:
a at 5 - 45 meters below the surface, the average concentration of phosphate was about the same in the seawater in the lava - affected area as in the seawater outside of the lava - affected area.
b for both depth ranges measured, the average concentrations of nitrate were substantially higher in the seawater in the lava - affected area than in the seawater outside of the lava - affected area.
c for both depth ranges measured in the seawater in the lava - affected area, the average concentrations of nitrate were substantially higher than the average concentrations of phosphate.
d in the seawater outside of the lava - affected area, there was little change in the average concentration of nitrate from 75 - 125 meters below the surface to 5 - 45 meters below the surface.

Explanation:

We need to analyze the data in the table to see which option is supported. Option A: Phosphate concentrations at 5 - 45 meters in lava - affected and non - lava - affected areas are 0.17 and 0.14 respectively, which is not a strong enough connection to support the idea of nutrient release. Option B: In the lava - affected area, nitrate concentrations at 5 - 45 meters is 3.1 and at 75 - 125 meters is 0.4. In the non - lava - affected area, they are ≤ 0.03 and ≤ 0.01 respectively. This shows substantially higher nitrate concentrations in the lava - affected area for both depth ranges, which supports the idea that the lava dislodged nitrate pockets. Option C: Comparing nitrate and phosphate concentrations within the lava - affected area doesn't directly support the nutrient release mechanism. Option D: The change in nitrate concentration outside the lava - affected area is not relevant to the nutrient release from lava.

Answer:

B. for both depth ranges measured, the average concentrations of nitrate were substantially higher in the seawater in the lava - affected area than in the seawater outside of the lava - affected area.