Imagine you’re walking along the beaches of Western Port. You look towards the Bay, basking in all its glory as the sunlight dances on the water. Suddenly, a sleek dorsal fin breaks the surface. A pod of bottlenose dolphins surge forward, their playful splashes sparkling in the sun.
But beneath the waves, an intricate web of life is at work – one that keeps those dolphins thriving. Beyond the splash, a hidden network connects flowing seagrass meadows to the powerful dolphins that call these waters home. Welcome to the unseen world of Western Port’s food web!
Picture a field of tall grass swaying in the wind. Seagrass meadows are just like this but underwater. These vibrant ecosystems lie in Western Port’s shallow coastal waters, where sunlight filters through the surface to reach the plants below.
This sunlight is key – because seagrass meadows are primary producers. This means seagrass plants capture energy from the sun to make their own food through a process called photosynthesis. When animals eat plants like seagrass, they gain the energy captured by the plants.That energy then passes from one animal to another as they feed on each other. Thanks to photosynthesis, the energy from the sun creates amazing ecosystems like Western Port.
One fish that relies on seagrass is the southern sea garfish, the only fish family known to consume fresh seagrass in Western Port. Like a silver needle threading through the water, the southern sea garfish has a long, slender mouth, built for snatching up plankton and seagrass fragments.
As a primary consumer, the garfish bridges the gap between plants and animals – transferring energy from photosynthetic seagrass to the rest of the food chain.
This energy then moves up the chain into the Australian salmon. These sleek predators surge upwards from seagrass beds, hunting schools of southern sea garfish near the surface. The garfish scatter frantically, trying to flee their predator that dominates them in size and speed. Just like in any ecosystem on earth, the cycle of life means that some garfish won’t escape, fuelling and sustaining the Australian salmon.
Australian salmon, with their dark bluish-green shimmer and forked tails like a mermaid’s, are skilled secondary consumers in the food web of Western Port. However, they must stay alert, as their own predators may be nearby.
As the salmon typically swim in schools, predators like the bottlenose dolphin may be closing in from both sides! Sensing a threat, the salmon pack tightly together, forming what is known as “bait balls”. Dolphins dart from either side of the school of fish, catching the ones closest to them.
As dolphins are at the top of the Western Port food chain, they play a vital role in the overall balance of the marine environment. As they feed on fish, they help regulate population numbers which in turn ensures the growth of smaller fish and aquatic plants such as seagrass. This ecosystems’ food chains are thus complex and tightly integrated; if one animal were to be removed from the environment, the precious balance between species may be disrupted.
So, next time you’re out on the water or walking along the beaches of Western Port and happen to spot dolphins, take a moment to think beyond the splash of the water as they play and hunt. Think about the big fish, small fish, and aquatic plants that sustain life, creating the hidden web of ocean life within Western Port.
Written by Maiya Mclean
If you would like to learn more about the huge diversity of life that can be found along our coasts and shorelines, please contact our Education Director at education@dolphinresearch.org.au for a public event, school holiday program or school incursion/excursion.
