Key environmental pressures

Overall, environmental pressures affecting inshore Reef seagrass meadows were moderate in 2019–20. The amount of light available for seagrass growth was higher and sea temperatures within the meadows were similar to the long-term average.

No major cyclones made landfall and there was less rainfall in the catchments and less river discharge flowing into the Reef than average. This was a welcome reprieve after major flooding in and around Townsville and further north the year before.

How did inshore seagrass meadows respond?

  • Inshore seagrass meadow condition remained unchanged from the previous year and in a poor state for the eighth year in a row. However, trends were not uniform across the Reef, with some improvement in the Mackay-Whitsunday region.
  • Seagrass abundance declined in many NRM regions. Declines in the Burdekin region (a legacy of the floods and low light experienced in the preceding 2018-19 summer) were the main contributor to poor overall abundance score for this year.
  • The resilience of seagrass meadows is also declining. Specifically, the ability of plants to reproduce sexually was very poor, with few flowers, fruits, and spathes present in most meadows. In fact these reproductive structures were completely absent at half of the sites surveyed.
  • Germination from seeds is important for recovery after disturbances, but seed banks were absent from two-fifths of sites. This makes the meadows very vulnerable.
  • After considering all indicators together, seagrass in Cape York, Fitzroy and Burnett–Mary regions are in the poorest state across the inshore Reef.
Inshore seagrass 2019-20

Inshore seagrass seminar 2019-20

What is monitored and where?

Four inshore seagrass habitat types (estuarine, coastal intertidal, subtidal and reef intertidal) are surveyed for:

  • seagrass abundance (per cent cover)
  • reproductive effort - counting reproductive structures (spathes, fruits, female and male flowers)
  • leaf tissue nutrients.

Seagrass species, the size and patchiness of the meadow, and the density of seeds in the seed bank are also measured. Factors that can affect seagrass condition are recorded including within-canopy seawater temperature, the amount of light reaching the plants, the sediment characteristics, and the abundance of macroalgae and epiphytes.

View the Inshore Seagrass sampling locations 2019-20

How do we monitor?

Shallower intertidal sites are examined using quadrats placed along transects at regular intervals. Deeper subtidal sites are sampled underwater on SCUBA along transect tapes laid along the seafloor or by camera. Cameras are lowered to the seabed from boats and underwater images are taken for analysis back in the office. A small sample of seagrass is taken to confirm species, and to characterise the sediment type.

Monitoring occurs in the late dry season (September-November) and late wet season (March-April).

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