Salt marshes contain a large amount of organic matter because waterlogged conditions prevent dead plant material from fully decomposing.
Explain what is meant by the term decomposer.
In a salt marsh ecosystem, decaying cordgrass (detritus) provides nutrients for saltmarsh amphipods. These amphipods are then preyed upon by sandpipers. Use this information to draw a food chain for these organisms.
Scientists can measure the organic matter content in soil using the Loss on Ignition (LOI) method. This involves drying a sample of soil and then heating it at high temperatures in a furnace to burn off the organic matter. The remaining ash is then weighed. The formula used to calculate the Loss on Ignition percentage is:
Loss on Ignition (LOI) %=dry mass of soil−mass of ashdry mass of soil×100\text{Loss on Ignition (LOI) \%} = \frac{\text{dry mass of soil} - \text{mass of ash}}{\text{dry mass of soil}} \times 100Loss on Ignition (LOI) %=dry mass of soildry mass of soil−mass of ash×100
An investigator suspected that an off-road vehicle had been driven illegally through a protected nesting site in a salt marsh. Soil samples were collected from the nesting site and from the tyres of three suspect vehicles (A, B, and C).
| Soil sample source | Dry mass of soil in g\text{g}g | Mass of ash in g\text{g}g | LOI percentage |
|---|---|---|---|
| Protected nesting site | 15 | 12 | 20 |
| Vehicle A tyre | 10 | 8.4 | 16 |
| Vehicle B tyre | 10 | 8.0 | 20 |
| Vehicle C tyre | 10 | 8.8 |
Use the formula to calculate the Loss on Ignition (LOI) percentage for the soil from the tyre of Vehicle C. Show your working.
State which vehicle is most likely to have been driven through the protected nesting site. Give a reason for your answer.
The owner of the suspected vehicle claimed that the soil analysis was not reliable evidence. Suggest one scientific reason why this soil analysis may not be reliable.