Environmental stressors associated with a warming climate and land-based runoff have led to changes in microbial processes across the Region. Although knowledge has advanced considerably since 2019, microbial processes remain poorly understood.

A range of pressures affect particle feeders, and condition varies between different species and species groups. No consistent trend has been identified since 2019. Since 2019, cover of some fast-growing species of corals has increased, but condition of corals in some areas remains poor. Long-term declines have occurred in the commercially harvested saucer scallop population, and the stock is currently classified as depleted.

Overall, primary production as a process is considered to be functioning well. Some shifts in the type of primary production (less in the water column, more in benthic producers) may have occurred in inshore areas as a result of improved water quality since 2019. Primary producers in some areas continue to be affected by high nutrient levels, sediment and temperature.
 

Despite its central importance to ecosystem functioning, an in-depth understanding of the process of herbivory across the Region and the mechanisms that affect it remains elusive. This process is undertaken by a wide range of species at varying scales and with diverse effects on ecosystem function across different habitats. Overall, herbivory has likely remained stable since 2019. Declines in some populations of dugongs, green turtles and potentially in herbivorous fishes may lead to reduced levels of herbivory in certain areas.

Predation affects a wide range of taxa that are subject to varying pressures. Although natural rates of predation are likely relatively stable, the Region’s ecosystems remain impacted by a long history of exploitation of apex predators and populations of some targeted species remain in poor condition. A large group of predators, the sharks and rays, are assessed as being in poor condition.

Despite some recovery of hard coral cover in offshore reefs over the past 5 years, rates of bleaching and increasing sea temperatures continue to be a major concern. Some evidence exists of shifts in symbiont diversity following the 2016 mass coral bleaching, but responses appear to be species-specific.

The level of knowledge of the condition of, and pressures on, recruitment processes within the Region varies substantially between species and species groups. There are very few data on recruitment for most organisms. Trends in recruitment, where known, are also highly variable between different groups; some are stable (seagrass) and some show declines (dugongs, marine turtles). Improvements in coral recruitment occurred on many reefs; however, trends were highly variable and the impacts on recruitment of widespread severe bleaching during the 2023–24 summer have not yet been determined.

A general decline in calcification rates is likely to have occurred, due to expected ongoing impacts from ocean warming and acidification. However, in the past 5 years, documented recovery of some key reef-building corals may have moderated this projected long-term trend. Changes in some other reef-building processes, such as dissolution and bioerosion, may also have occurred, but they are only likely to become evident over longer time frames. Increasing coral rubble may be becoming an important driver of reef-building processes on some reefs.

Increasing sea temperatures, nutrient inputs and changes in species composition and habitat availability alter the balance of competitive outcomes in the Region. For example, macroalgae continue to outcompete corals in some inshore areas. Cumulative stressors and increasing disturbance frequency may be increasingly favouring fast-growing and opportunistic species.

The Reef continues to be a system with high internal and external connectivity across its diverse ecosystems. Legacy impacts (such as hydrological barriers in the Catchment) have reduced this connectivity, and the emerging impacts of climate change are leading to further declines in some areas and for some key species groups such as corals.