A group of students sampled the macroinvertebrate populations at two different sites, Site A and Site B, along a river to assess water quality. Their results are shown in the table below.
| Indicator species | Number at Site A | Number at Site B |
|---|---|---|
| Stonefly nymph | 52 | 2 |
| Mayfly nymph | 38 | 0 |
| Freshwater shrimp | 45 | 12 |
| Bloodworm | 5 | 62 |
| Sludge worm | 1 | 120 |
Use the data in the table to explain which site is more polluted.
