Often, the very thing that makes something desirable or attractive is its elusiveness or sense of mystery. In that case, seagrass should be one of the sexiest aquatic topics around.
But as users of the Gippsland Lakes, we are more likely to view seagrass as the annoying, clingy, slightly slimy stuff that wraps around our legs and diminishes the appeal of the lake bed. Or which creates tangles when we are fishing and drags the bait off our hooks as we retrieve our lines.
But those long tendrils, swaying seductively just below the surface of the water play a major part in keeping the waters of the Gippsland Lakes clear, and the local fish and marine animal population very happy.
If the seagrass disappeared tomorrow, the Gippsland Lakes would be “muddier and greener, with less fish,” Perran Cook, Associate Professor in the Water Studies Centre at Monash University, says. Not a good outcome for the environment, or the people who flock to the Lakes for recreation.
“Seagrasses stabilise the sediment, preventing resuspension or muddy water. They take up nutrients, which make the water clearer, and they provide important food and habitat for juvenile fish.”
Associate Professor Cook has been leading a study on seagrass in the Lakes, run collaboratively by Monash and Melbourne universities and the Arthur Rylah Institute. The data collected is being compared to the last major study, finalised in 1997.
And while some areas had seemingly come back to life, especially those around Metung and Raymond Island, the seagrass population in other areas had decreased. Associate Professor Cook says there is a need to continue monitoring seagrass in the Lakes, to confirm current observations, learn more and ensure the ongoing success of what is undoubtedly an important relationship.
He says a vital fact about seagrass is that they support bacteria in their root systems that fix nitrogen in the same way that bacteria associated with legumes do.
“I think they might be an important supply of nitrogen to coastal ecosystems, in a form that does not cause algal blooms.”
This is highly significant, as algal blooms can be toxic to the ecosystems they thrive in. In fact, it was most likely a blue/green algae bloom in 2007 that caused a reduction of seagrass in the Gippsland Lakes that was so significant, it didn’t properly recover until 2013.
Associate Professor Cook said it was difficult to pinpoint why the seagrass recovery was so slow, because the factors controlling seagrass distribution in the Gippsland Lakes are not fully understood.
“My best guess is that after a large decline, it can take some years for the seagrass root systems – rhizomes – to recover.”
“Seagrasses require nutrients for growth, and it is possible the high river flows from 2010 to 2012 provided this nutrient boost, that then allowed increased seagrass growth in the following years.”
“This confirms what we know about the Lakes – it is a dynamic and changing system.”
So how can we, as lovers of the Gippsland Lakes, help protect an asset that contributes significantly to the clear, alluring waters that beckon us back again and again, and support a rich and healthy ecosystem of flora and fauna?
“Avoid anchoring in seagrass beds, as the recovery of the anchor damages the bed and roots. On an individual level this does not do much damage, but if many people do this in popular areas, it can add up to larger damage that takes longer to recover from.”
For more information see our some simple suggestions to help protect seagrass
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