Natural eutrophic lakes have higher nutrient levels than oligotrophic, dystrophic and mesotrophic lakes, giving rise to a higher productivity than these more acidic lakes. The largest natural eutrophic lake in Wales is Llangorse Lake in Breconshire, which overlies Old Red Sandstone. The aquatic flora tends to be dominated by water lilies (Nuphar spp.) and pondweeds (Potamogeton spp.) with a large population the shining pondweed (Potamogeton lucens) present. Further eutrophication and pollution events are key issues for eutrophic lakes, as are increasing levels of recreational activities.