A finding question tests whether new evidence supports a researcher’s exact claim. Read the conclusion and put the claim in a few words, keeping words that say how large the effect is. If the passage gives several reasons measurements could be wrong, trace how each would change the reported result. Then predict what would support the claim: evidence must show the effect the researcher names, including how large that effect is. Sharing the topic isn’t enough to support the claim.
Hints
- Hint 1
Reread Santos’s final sentence and check how large he says the undercount is.
- Hint 2
Trace both possible losses: what can happen at the mesh, and what can happen during digestion?
- Hint 3
How could you tell whether a low final count means there was little plastic in the sediment or plastic was lost while the sample was processed?
Step-by-step
Test how much the methods miss
Step 1Identify the size of the undercount
Santos says published tallies likely represent only a small fraction of the plastic in trench sediments, so this question asks for evidence of undercounting. How large is the claimed gap? Most of the plastic would have to go uncounted, not a few particles, so a supporting finding must show a large loss.
- Step 2
Predict a test of the losses
The passage gives two ways material could disappear: polymer fibers thinner than 50 µm escape the mesh, and digestion can partially dissolve certain biodegradable plastics. How could we tell whether these steps cause a large undercount? A count of recovered plastic alone leaves the missing amount unknown, because escaped or dissolved material won’t appear in it. Compare the amount before processing with the amount counted afterward, using the usual procedure to test its losses.
- Step 3
Set aside findings that miss the claim
Which findings test the claim that counts capture only a small fraction? The continental slope finding is about shallower sediments and large particles that meshes capture, not material missed in trenches. The only slightly higher counts with finer filters show a small rise, not a severe undercount. A small percentage of biodegradable plastics detected tells us about what remained, not how much digestion removed.
- Step 4
Measure the missing share
The 35 percent recovery finding puts known amounts of thin fibers and plastic fragments through the standard sampling and digestion procedure. Recovering about 35 percent means about 65 percent goes uncounted, so the method misses most of the tested material. That result supports a large gap between published tallies and the microplastics actually present on the seafloor. Choice A.