OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What impact does deep trawling have on marine ecosystems?

1. It restores habitats for fish populations

2. It damages the seabed and disrupts ecosystems

3. It decreases fish reproduction rates

4. It increases biodiversity in deep sea areas

The correct answer is: It damages the seabed and disrupts ecosystems

Deep trawling significantly damages the seabed and disrupts ecosystems. This fishing method involves dragging heavy nets along the ocean floor, which can lead to the destruction of habitats such as coral reefs and seagrass beds. These habitats provide essential shelter and breeding grounds for various marine organisms. When the seabed is disturbed, it not only removes physical structures that many species rely on but also resuspends sediment into the water column. This can reduce light penetration and affect the photosynthetic organisms like phytoplankton, which are the foundation of marine food webs. Furthermore, the impact of deep trawling extends beyond immediate physical damage. It can lead to changes in species composition, with some species being overfished while others may proliferate in the absence of their natural predators, thereby altering the balance of the ecosystem. As a result, the overall health of marine ecosystems diminishes, affecting biodiversity and the sustainability of fish populations over time.