Key environmental pressures

Pressures affecting inshore Reef seagrass habitats were low in 2022–23, but variable among regions and habitats. There was no significant cyclone activity affecting the inshore Reef. Overall, rainfall was around the long-term average but river discharge was variable among regions but above the long-term median for the Reef.

Benthic light availability as daily averages was slightly below the long-term average for inshore Reef seagrass meadows on average.
 
Within-canopy water temperatures are one of the most significant environmental pressures impacting inshore Reef seagrass meadows. Although slightly lower than the previous reporting period, temperatures in 2022–23 were the third highest since the MMP was established, and nearly half a degree above the long-term average.

Read the latest Marine Monitoring Program Annual Inshore Seagrass Report 2022–23.

How did inshore seagrass respond?

Reef-wide seagrass condition for inshore seagrass meadows remained in an overall ‘moderate’ condition in 2023.
 

• In the Cape York region:
• Inshore seagrass communities remain in a ‘moderate’ condition.
• Seagrass abundance increased from the previous period overall. The improvement in seagrass abundance was driven primarily by increases at coastal intertidal and subtidal sites.
• The resilience indicator score deteriorated from ‘moderate’ to ‘poor’. Coastal sites experienced a significant decline, particularly after a substantial increase in the previous year.
   

• In the Wet Tropics region:
• Seagrass Index score remained ‘moderate’. However, there were differences observed between the northern and southern meadows.
• In the northern sites, seagrass abundance deteriorated across the sub-region relative to the previous period largely because of declines some reef intertidal and subtidal sites, and slightly less favourable climatic conditions across the sub-region. Resilience increased in the north due to improvements in both coastal and reef intertidal habitats.
• The southern meadows showed a lower overall abundance and has been on a declining trend for the second consecutive year, after reaching its peak in 2020–21. Resilience also declined in the south but was the second highest level recorded.

• In the Burdekin region:
• Seagrass Index score deteriorated but remained ‘moderate’.
• Seagrass abundance marginally decreased relative to the previous period and remains lower than historical records. Abundance remained ‘moderate’.
• Seagrass resilience slightly decreased, with reproductive structures absent from some site, but remained ‘moderate’.

• In the Mackay-Whitsunday region: 
• Inshore seagrass meadows improved in overall condition but the condition grade remained ‘moderate’.
• The seagrass abundance score increased and was ‘moderate’, driven by increases in estuarine intertidal and coastal and reef subtidal habitats.
• The overall resilience score was ‘moderate’, increasing to its highest level in six years. Trends were highly variable between habitats.

• In the Fitzroy region:
• The overall seagrass condition score slightly deteriorated and remained ‘poor’.
• Seagrass abundance score marginally improved from the previous period and was ‘poor’, but this was driven by only one site (estuarine intertidal).
• The latest findings on resilience showed a decrease to the second lowest level recorded, but remained ‘poor’.
• For the third year in a row, inshore seagrass meadows in the region have experienced a decline, despite gradual improvement from 2012–13 to 2019–20 after years of climate-related impacts.

• In the Burnett-Mary region:
• Seagrass condition declined in overall condition to ‘very poor’ for the first time in 16 years.
• The seagrass abundance score remained ‘very poor’ for the second consecutive year. The decline is a continuing trend that has been occurring for the region since 2015–16.
• Resilience declined and remained ‘poor’ overall in the region. It is the fourth time this decade that the score has declined below moderate.
   

Temporal trend in regional Seagrass Index scores from 2005–06 to 2022–23. Values are indexed scores scaled from 0–100 and graded: ■ = very good (81–100), ■ = good (61–80), ■ = moderate (41–60), ■ = poor (21–40), ■ = very poor (0–20). Note scores are unitless.

What is monitored?

Inshore seagrass meadows are monitored at sites in four types of habitats: estuarine, coastal intertidal and subtidal, and reef intertidal.

• At these sites, seagrass monitoring is conducted by assessing the following indicators:
• Abundance as per cent cover 
• Resilience metric incorporating species composition and reproductive status (full details of the resilience metric can be found in the Resilience in practice report)

In addition to these indicators, seagrass species, the size and patchiness of the seagrass meadows, and the density of seeds in the seed bank are also assessed.

Factors that can affect seagrass conditions are recorded, which include within-canopy seawater temperature, the amount of light reaching the plants, the sediment characteristics, and the abundance of macroalgae and epiphytes.

• Where is seagrass condition monitored?
• Cape York
• Wet Tropics
• Burdekin
• Mackay-Whitsunday
• Fitzroy
• Burnett-Mary

Additional site-level information can be found in the Seagrass Watch website.