Melbourne’s best kept secret

“… up to 82% of the marine life [in Port Phillip Bay] is found nowhere else in the world, so it’s completely unique. You compare that to the Great Barrier Reef, where only 10% of the marine life is unique to the area.”

— Sheree Marris, author of Melbourne Down Under

Port Phillip Bay is one of the most unique areas in the world.  Let that sink in for a moment. On our doorstep lies one of the most impressive, species-rich and colourful marine habitats in the entire world – yet how many people are even aware of its magnificence?

If it’s so impressive and we live right next door, then surely Melburnians would know about it, right? After all, we know when the latest café or restaurant opens – yet we are unaware of the beauties that live in our own oceans. This may come down to the misconception that colourful fish and corals are only found in warm tropical waters like the Great Barrier Reef. Contrary to that idea, temperate and even polar waters are home to a wealth of colourful fish, sponges and corals. Another reason might be that our knowledge concerning oceans is relatively limited. More than 90% of our oceans remain completely unexplored and considering 12 people have been sent to the moon since 1969, less than a handful of people have reached the deepest part of our ocean, the Mariana Trench.

 Wandering sea anemone.  Image: Cathy Cavallo
Wandering sea anemone.  Image: Cathy Cavallo

For a seemingly small area, Port Phillip Bay is home to an abundance of marine life.  Over 12,000 different marine species call Victoria home, whilst up to 1,300 different plant and animal species are completely unique to Port Phillip Bay. In fact, the Bay is even home to approximately 100 individuals of our very own species of bottlenose dolphin known as the Burrunan, which some studies suggest may be a distinct species.

The Bay itself covers nearly 2,000 square kilometres and averages just 13 metres in depth, making it a particularly shallow bay given the extensive commercial use that occurs here. It consists of a variety of habitats including sandy seafloors, tall kelp forests, thriving seagrass beds and colourful rocky reefs and sponge gardens. However, most of the seafloor is sand and silt where diverse groups of invertebrates play a crucial role in filtering nutrients and pollutants.

Due to the large expanses of sandy floor and relative shallowness, dense seagrass meadows have made their home here, covering much of the western coast from Queenscliff to Werribee as well as some pockets on the east coast from Sorrento to Mordialloc. While some may not appreciate the beauty of seagrass meadows, I am certainly one who can testify to it. When I conducted my Master’s research project, I looked at the impact that burial and erosion had on these majestic and often under-appreciated habitats. Many times while snorkelling, I found myself completely transfixed by the peaceful swaying of seagrass blades and how fish used the meadows like a garden, darting in and out playfully.

In fact, seagrass meadows aren’t anywhere near as boring as they may look. They are integral to the functionality of the Bay and provide a home for a plethora of animal life including King George whiting (Sillaginodes punctatus), spotted pipe fish (Stigmatopora argus), the eleven-armed sea star (Coscinasterias calamaria), Maori octopus (Macroctopus maorum), banjo sharks (Trygonorrhina sp.), a threatened snapping shrimp and many more. Seagrass meadows also play a critical role in reducing sand erosion from beaches, are a food source for marine life, provide a home for many commercially important fish species, and help cycle nutrients throughout the Bay.

 Shaw's Cowfish.  Image: Cathy Cavallo
Shaw’s Cowfish.  Image: Cathy Cavallo
 A vividly coloured sea urchin.  Image: Cathy Cavallo
A vividly coloured sea urchin.  Image: Cathy Cavallo
 Verco's nudibranch.  Image: Cathy Cavallo
Verco’s nudibranch.  Image: Cathy Cavallo

The rocky reefs, tall kelp forests and vibrant sponge gardens are also teeming with marine life. Predominantly found on the margins of the Bay, they are dominated by hundreds of different seaweeds, fish, crustaceans and sponge gardens. For anyone that has dived or snorkelled in Port Phillip Bay, vibrant colours become strikingly obvious – something that is not initially expected. For example, take one look at the southern blue devil (Paraplesiops meleagris), Shaw’s cowfish (Aracana aurita), sea tulips, wandering anemones (Phlyctenactis tuberculosa), six-spined leatherjacket (Meuschenia freycineti), sea stars and the blue and yellow tambja (Verconis macro) and you can see that life in Port Phillip Bay is far from boring – even rivalling the colours seen on the Great Barrier Reef. The Bay is also home to giant kelp forests.

While their current stands do not compare to their previous abundance, Victoria’s majestic marine state emblem, the weedy seadragon (Phyllopteryx taeniolatus), can be seen here in all its glory. I can distinctly remember seeing this species for the first time or, more accurately, not seeing it until a colleague pointed it out to me. Floating gracefully and peacefully through the water, I wondered how such a delicate creature was able to survive in the often turbulent waters of Port Phillip Bay – a truly majestic animal indeed.

Luckily, we at Wild Melbourne aren’t the only ones who think Port Phillip Bay is amazing! There are several other groups, including Reef WatchExplore Underwater Victoria and Melbourne Down Under, that aim to promote the diversity found in Port Phillip Bay so that everyday Victorians can discover these underwater secrets for themselves. Port Phillip Bay is still Melbourne’s best kept secret; however, it’s time we told everyone else about it so that they too can appreciate and experience the joy and beauty it can provide.

 Victoria's marine state emblem, the weedy seadragon.  Image: Cathy Cavallo
Victoria’s marine state emblem, the weedy seadragon.  Image: Cathy Cavallo


The Bay supports:

•         approximately 300 species of fish;
•         several hundred species of molluscs;
•         several hundred species of crustaceans;
•         at least 200 species of seaweeds;
•         several hundred species of polychaetes (bristle worms);
•         two species of seagrass;
•         several hundred species of cnidarians (jellyfish, corals, etc.);
•         and several hundred species of sponges.

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