New approach to seagrass resilience

The Department of Water and Environmental Regulation’s resident seagrass expert Dr Kieryn Kilminster, is building worldwide understanding of what it means for seagrass to be resilient.

Seagrass meadows are an important part of estuarine ecosystems, providing habitat and food for birds and marine life, and contributing to good water and sediment quality.

The department’s seagrass team has spent years investigating with experts from around the world to analyse the way seagrass meadows react to natural or man-made environmental changes.

The estuaries of the Regional Estuaries Initiative are a major focus and source of data for the team’s work.

Last June, Kieryn co-led a workshop in Singapore with Dr Catherine Collier from James Cook University and Dr Kathryn McMahon from Edith Cowan University, along with approximately 40 international researchers and managers, looking at ways to embed seagrass resilience in monitoring and management.

“We are looking at cutting-edge, global research to hopefully develop a benchmark of best practice for seagrass monitoring programs around the world,” Kieryn said.

Over the years, the DWER seagrass team has collaborated with research students at three WA universities, helping to grow the knowledge-base required to better understand seagrass resilience.

“It’s a new direction for seagrass monitoring”, Kieryn said.

“In the past, seagrass monitoring programs would measure species, location and density but very few would measure other factors like seed bank distribution, flowering and growth rates. This information helps figure out how well a meadow would be able to cope with a potentially damaging event – like a flood.

“A stressed seagrass meadow may die off due to a relatively minor disturbance compared to a healthy meadow that may be able to survive and quickly recover from large, damaging events. The type of seagrass species present also has a very large influence.”

With extreme events likely to increase in the face of climate change, and man-made and environmental changes accounting for a 30 percent global reduction in seagrass meadows, Kieryn stresses the importance of understanding seagrass resilience as the rate of loss accelerates.

“Once a meadow is lost, water quality can deteriorate and this can make it nearly impossible for seagrass to re-establish.

“Seagrasses alter conditions in the environment to maintain the conditions that keep them thriving. For example seagrass requires low sediment suspension (clear water) so that light can penetrate to the seagrass and fuel photosynthesis. However the seagrass itself helps to settle sediments being washed in by rivers and streams.

“Without a pre-established seagrass meadow it would be very difficult to achieve water conditions that would be suitable for seagrass growth,” she said.

Kieryn is hoping their work will be used to,

  • Help others develop comprehensive, best practice seagrass monitoring programs around the world
  • Inform management decisions to improve water quality to make seagrass meadows more resilient and prevent seagrass loss
  • Develop a method to quantify the probability of a seagrass meadow recovering after a damaging event

“Quantifying the likelihood of a particular meadow recovering from a particular event is really difficult and complicated. With help from experts around the world we are making progress but we are still many years away from having a large enough evidence base to be able to put a number on resilience.

“One day we hope to be able to say ‘based on the current conditions, if we dredge this site then the seagrass meadow one kilometre away has a 70 per cent chance of recovery’ – but there is a lot more work that needs to happen before that is possible.”

Around 40 per cent of global seagrass species are found in WA waters and play a central part of ecosystems in most WA estuaries including Oyster Harbour, Wilson Inlet, Vasse-Wonnerup Estuary, Leschenault Estuary and Peel-Harvey Estuary.

The department’s seagrass team currently includes Kieryn Kilminster, Marta Sanchez Alarcon, Katherine Bennett and formerly Vanessa Forbes.