Like many coastal residents, I have often cursed the existence of salt marshes and samphire flats. Smelly, salty, bug infested places that I couldn’t visit without long pants, sleeves and a can of heavy duty, tropical-strength mozzie repellant. But I recently attended a workshop on Coastal Wetlands, hosted by the Arno Bay Progress Association, and I came away with a new appreciation of these amazing habitats.

What I didn’t know before is that these seemingly boring, insect-infested, smelly places are actually the lifeblood of the coast – habitats of such high nutritional value that contain intricate food chains for both land and marine animals. In our region, these habitats are spread all along the coast from south of Whyalla, and up to Tourville Bay west of Ceduna and beyond. They are even found offshore on Flinders Island and inland near salt lakes.

Coastal wetlands are the home of food chains that grow into multi-level interactions that include insects, fish, crustaceans like crabs, shrimp and their larvae, birds ranging from shorebirds right up to birds of prey, bats and even mammals like the native water rat .

These food chains can even be broken up into three main cycles – the aerial cycle (birds, bats and insects), the aquatic cycle (crustaceans, fish, water-birds and insects) and the surface cycle (algae, invertebrates, fungi and bacteria).

But an appreciation of the salt marsh starts lower, so lets get down to the surface of a salt marsh.

Have you ever wandered across a samphire or salt marsh bed and wondered why the ground crunched a little under-foot? This crunchy crust that forms on the ground is actually alive – when it’s wet. Inundation of salt marshes can occur daily, monthly or annually, depending on the location, the tidal movements and the topography. When inundation does occur, this salty crust comes alive, teaming with diatoms and blue-green algae. Diatoms are a form of algae with cell walls that contain silica, and they are often used as an indicator of environmental health. Blue-green algae is a nitrogen fixing organism, which means that they do not need to rely on other organisms for food. However, this diatom/algal film is an important food source for crabs and their larvae, amongst others. The crab larvae in turn are part of what is called zooplankton – microscopic marine organisms that float about in the water column, which are mainly the larvae of crustaceans, sea jellies and fish.

As we move further up the food chain, we find that zooplankton is an incredibly valuable source of food for the sprats of young fish and other marine creatures, many of which are economically important for fishing and aquaculture on Eyre Peninsula. In fact, research over the last five years has shown that it is the salt marshes,  and not the adjacent mangroves,  that are the more productive environments; contrary to what was previously thought.

Other functions of the salt marsh/coastal wetland environment relate directly to off shore habitats – a sort of “water-conditioning” role. This process salinises water run-off from the land and removes excess sediment. Without either of these processes, habitats such as seagrass meadows and temperate reefs, and many of the organisms that live there, would choke on the excessively turbid water or die from changes in water acidity and salinity.

On Eyre Peninsula, many of our coastal wetland areas contain a rare and endangered species of samphire known as the bead samphire. It is a poorly understood species, with complex pollination and seed dispersal interactions. It has been found that some species of small fly parasitise the plant, laying their eggs in the flowers so that emerging young can feast on the seeds. Bead samphire is listed as Nationally Vulnerable because of its sparse distribution and isolated populations. It is also listed as one of the priority species in the Draft Recovery Plan for threatened flora on Eyre Peninsula, recently released by the Department of Environment and Heritage.

Salt marshes can be put in jeopardy by coastal development and unregulated vehicle and pedestrian access and we could lose this species if the value of coastal wetlands is not recognized by the general public and land managers.

Other threatened species commonly found in salt marshes include rare and endangered butterflies, like the bitter-bush blue butterfly, the yellowish sedge-skipper and the cynone skipper. Many of these species require specific host plants on which to lay their larvae, so destruction of their habitats would mean these beautiful butterflies would be gone forever.

So coastal wetland habitats aren’t the boring, unproductive and annoying habitats we might have thought. It is important that we recognize this and strive to conserve as many of these areas as we can. This can start at the local level with landholders making an effort to exclude stock from salt marshes on their properties.

If you have a salt marsh area that you would like to protect, or if you would like to know more about these fascinating habitats, please call Eyre Peninsula Natural Resources Management on Management Officer, Eyre Peninsula Natural Resource Management Board

AUTHOR:  Louise Mortimer, Coast and Marine Management Officer, Eyre Peninsula Natural Resource Management Board.
CONTACT: Louise Mortimer, Telephone (08) 8682 7555