# A coastal wetland ecosystem supports many different species of plants, invertebrates, fish and birds. A sewage works nearby begins discharging excess nutrients into the wetland. Over several years, fast-growing algae cover the water surface and most other plant species disappear. Explain why the loss of plant species in the wetland is likely to reduce the biodiversity of the whole ecosystem.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 2.5 Biodiversity · Explain · 5 marks

> A coastal wetland ecosystem supports many different species of plants, invertebrates, fish and birds. A sewage works discharges excess nutrients into the wetland. Over several years, fast-growing algae cover the water surface and most other plant species disappear.

## Mark scheme (5 marks)

1. Plants are producers / the source of food / energy for other organisms in the ecosystem
2. Fewer plant species means fewer food sources / habitats available for animals / invertebrates
3. Animals / species that depend on specific plant species for food or habitat will decline / become locally extinct
4. This reduction in species causes a further knock-on / cascade effect through food webs, reducing other species further
5. Overall biodiversity is reduced because there are fewer different species / the variety of species in the ecosystem decreases

## Key terms

- [biodiversity](https://www.gradenine.co.uk/glossary/biodiversity)
- [ecosystem](https://www.gradenine.co.uk/glossary/ecosystem)

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-coastal-wetland-ecosystem-supports-many-bc9cca2a) · Published by Druglandscape Ltd.