Some examples of Marine Animal Forests in Danish waters: (A) Community of Porifera with scattered red algae in the area of the Great Belt bridge, (B) Common seastar (Crossaster papposus) with assemblages of sea urchins (Strongylus centrotus) and polychetae (Pomacoteros triqueter) at Schultz’s Grund in the Southeast Kattegat, (C) Reef structure made by bubbling methane of Frederikshavn in Kattegat dominated by the sea anemone Metridium senile, (D) Community of soft corals, hydrocoans and the red algae Phycodrys rubens (Kattegat, ‘Chinese Wall’, 18 m depth). Images were kindly provided by Karsten Dahl (Aarhus University; Copyright Karsten Dahl with permission to publish under the terms of the Creative Commons Attribution 4.0 License).