Nonfiction

drawn to science – Opening the trapdoor: Frogs and artificial wetland traps with kate cranney

2 March 2015

Meet Michael Sievers, PhD candidate with the School of Biosciences, who researches artificial urban wetlands and the frogs that call them home. Michael asks: are these wetlands actually ecological traps for native frogs?

As a boy, Michael Sievers would spend hours in wetlands, rock pools and rivers. He says he’s kept “almost every aquatic pet you can think of,” including countless fish species, axolotls, starfish and a crayfish called Pinchy. As a teenager, he had six fish tanks in his bedroom. Years on, he still spends hours in wetlands … as a profession.

What trapped Michael’s interest?

Michael’s affinity for aquatic animals has taken him to some incredible places.

After studying a Bachelor of Science (majoring in Marine Biology), he completed a Master of Science at the University of Melbourne. His Masters project helped the cultured mussel industry in Port Phillip Bay understand the interactions between mussels and biofouling (when unwanted organisms grow on mussels). Following this, Michael spent two years up and down Australia’s east coast as a research assistant, sampling the intertidal zone, collecting data, and designing and carrying out experiments.

In 2013, Michael travelled to Norway where he worked in a tiny little town called Matre, at an international marine research station called (take a breath) Havforskningsinstituttet researching Atlantic salmon. After two months there, he returned to Australia to work with Tasmania’s Huon Aquaculture, tutor at the University of Melbourne and start his PhD.

With this impressive background, it is little surprise that Michael recently won The Nature Conservancy Applied Conservation Award for his PhD.

Suspicious ponds: caught in an ecological trap

Have you seen artificial wetlands in your suburb or town? Maybe you can picture a shallow, densely planted wetland in a low-lying area? If not, the next time you’re in Royal Park, stop by the Trin Warren Tam-boore artificial wetland – a five-hectare haven for water birds.

The primary function of artificial wetlands is to treat stormwater naturally. They are like urban kidneys. They filter stormwater, removing pollutants before the water enters our rivers and oceans.

But wetlands serve another, sometimes unintended, function – they become home to countless animal species that colonise them. Artificial wetlands certainly do seem inviting – they provide abundant food and shelter, and in highly urbanised areas, they may be the only suitable wetland habitat around.

On the surface, this situation sounds rather rosy. But Michael’s PhD dives a little deeper.

Michael’s PhD research: frogs in planted ponds

Michael tells me, “The ecological consequences of [animals] choosing these habitats are unknown.” So his research asks: what are the ecological costs and benefits of artificial wetlands in Melbourne’s urban landscapes? Are artificial wetlands an ecological trap for native frogs?

First, Michael will figure out the pros and cons of artificial wetlands for frogs. He says the likely pros are permanent habitat, food and plenty of vegetation. And the likely cons are predation, low genetic diversity and pollutants.

Pollutants like heavy metals, pesticides, and high levels of salinity and nitrogen can reduce fitness and cause deformities in frogs. Pollutants may also reduce a frog’s ability to reproduce and detect predators. This is a serious issue given that 41 per cent of all amphibian species face the threat of extinction.

Michael will also create management guidelines to assess the conditions of wetlands and improve wetland design. Finally, he will develop new ways to test how pollutants affect frogs’ behaviour and their sensory development.
Therefore, the ultimate question of Michael’s PhD is: are artificial wetlands ecological traps?

What is an ecological trap?

An ecological trap is a habitat that an animal perceives as high quality and is preferentially selected, because of cues like a high cover of plants. However, undetected factors (like pollutants) actually mean the habitat is an undesirable place to live and can reduce the animal’s fitness (survival, growth, reproduction etc.).

This spring and summer, you can find Michael surveying urban wetlands around the Greater Melbourne Region, mostly in the Yarra and Dandenong catchment areas.

And when Michael’s not chasing frogs, you can find him diving and snorkeling. He says, “During my last dive off Rye pier, four dolphins came out of nowhere and hung around playfully chasing a huge school of salmon for ten minutes.” However, his favourite dive is The Cottage by the Sea in Queenscliff, where he has dived with giant cuttlefish and the iconic blue devil.

I ask Michael what he’d like to do after his PhD. He talks about the merits of academia, before settling on an appropriately aquatic turn of phrase. “In many cases, you have to take whatever opportunities come your way … you just have to go with the flow.”


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