Predators and Prey:
  Bird eats Crab, Limpets, Mussels, Prawn and Whelk
  Crab eats Limpets and Mussels
  Fish eats Prawn
  Limpets eats Seaweed
  Lobster eats Crab, Limpets, Mussels and Whelk
  Mussels eats Phytoplankton and Zooplankton
  Prawn eats Zooplankton
  Whelk eats Limpets and Mussels
  Zooplankton eats Phytoplankton

Apex Predators: Bird, Fish and Lobster
Producers: Phytoplankton and Seaweed
Most Flexible Eaters: Bird
Tastiest: Limpets and Mussels

Heights:
  Bird: 4
  Crab: 3
  Fish: 3
  Limpets: 1
  Lobster: 4
  Mussels: 2
  Phytoplankton: 0
  Prawn: 2
  Seaweed: 0
  Whelk: 3
  Zooplankton: 1

For an A+:
  Herbivores: Limpets and Zooplankton
  Omnivores: Mussels
  Carnivores: Bird, Crab, Fish, Lobster, Prawn and Whelk