Discovering the Tiny Creatures that Live in Marine Plants

BY Angela Rossen

If you go for a snorkel near the shore you will find meadows of gently swaying seagrasses and rocky reefs with brightly colored algae that are often called seaweeds. Among these swaying leaves and algal fronds live myriads of tiny creatures. Marine plants act as nurseries, providing shelter and food for almost all our marine species at some time in their lives. 

Finding the tiny sea ‘insects’, which are known as macro invertebrates is always exciting. These little creatures feed on the soft algae, and seagrass leaves and on the harder chalky coralline algae that grow on seagrass. They also eat plankton and occasionally they eat each other. In turn, they are delicious morsels for tiny fish and crustaceans that are then food for larger fish and shore birds.

The next time you come to the beach bring a small white bucket (to let in the light) and a magnifying glass. Make sure your bucket is clean with no residue of paint or cleaning chemicals. Fill it with fresh seawater. Find a wire-weed seagrass stem with a fringe of red brown algae and place it gently in your bucket without shaking and add a couple of branches of some leafy seaweed. If you wait for a moment you will notice lots of tiny creatures zipping around.

Geraldton Grammar students discovering macro invertebrates (A.Rossen)

You are likely to find amphipods, tiny prawn like animals and bristle worms, flatworms, and transparent or green shrimp. You may be lucky enough to find an anemone larvae or a sediment (sand) worm with waving tentacles and external gills that look like soft antlers. Some tiny invertebrates also make tunnels in seagrass leaves and live within those very narrow spaces. Also attached to seagrass leaves are minute spiral tube worms with delicate transparent feeding arms that comb through the water to catch floating bits of food. Try to get some good photos with your phone camera before you carefully return these treasures to the ocean.

Amphipod on seagrass (A. Rossen)

All these plants and creatures are perfectly adapted to their environment and are very sensitive to poisonous pollutants that enter the ocean. For example, road water drains are designed to divert stormwater into rivers and to the seashore. Unfortunately they also bring rubbish, fertilizers from gardens and other pollutants from the roads.  Remember these tiny creatures when you fertilize your garden and always dispose of liquid waste and rubbish correctly.

Angela Rossen is Artist in Residence with The Oceans Institute at The University of Western Australia

Related links:

If you want to find out more about the tiny creatures that live in the marine plants call Angela Rossen to talk about a Coastal Biodiversity Art Workshop with your community or school group visit

Perth Science Festival

World Biotech Tour.