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Vulnerable trait-combinations in corals and fishes and their management

Periodic Reporting for period 1 - TRIM (Vulnerable trait-combinations in corals and fishes and their management)

Reporting period: 2017-09-01 to 2019-08-31

Coral reefs are sentinels for ecosystems’ responses to the climate crisis, with ongoing major global degradation of reef condition, and the expansion of coral reef biota into higher latitudes. This is a problem because it is disrupting the reef resource use of the almost 1 billion people depending on reefs. The management of reefs, and marine systems generally, depends on robust understanding and predictions of how climate stressors affect their functioning. This understanding, in particular the functional perspective, is in its infancy, meaning that we lack knowledge and tools to manage changing coral reefs to both maintain functional integrity and a reasonable level of resource use.

TRIM aimed to quantify how multiple coral reef taxa (e.g. corals and fishes) interact to support ecosystem functioning. This necessitated a trait-based assessment of functional groups of these taxa. The main questions addressed were:

A. What functional groups exist in taxa and do they respond differentially to human pressures? This question required the building of trait databases for species recorded in existing surveys and use them to identify functional groups of species from various taxa. The abundances of these functional groups recorded in surveys can then serve to assess their responses.

B. Are the responses to environmental stress of functional groups and their vulnerability linked? This question aimed to explore responses of taxa together, focussing on the interactions of their functional groups, as well as commonalities and differences among responses of different taxa.

C. How should functional groups be managed to mitigate the effects of change (e.g. human use change or climate warming)? This question aimed to develop new and integrate existing methods to conceptualise a new resource management framework of trait-based management.
Work performed:

Building trait databases for 695 fishes, 97 echinoderm species, 59 algae species, and 81 mollusc species from the literature, and downloading traits for 83 coral genera from an existing source.

Developing trait groups for all taxa, with particular focus on method development. The classification of groups highly depends on the traits used and the method of classification, necessitating a sensitivity analysis of trait groups.

Data collection included surveys of the abundance and biomass of fishes, corals, echinoderms, and benthic patterns in Australia and Japan, complementing and extending earlier collections.

Running analysis quantifying trait-based processes that underpin the tropicalisation of subtropical and temperate shallow marine systems.

Working towards a framework of considering ecological responses to climate change for coral reef taxa in their management.


Results:

TRIM has produced results for all its three objectives, with activities in publication and dissemination still ongoing. The project focussed mostly on the species in the tropical to temperate transition zones in Japan and Australia for the first two objectives. The conservation objective has worked more broadly, focussing on global or general scales. The project found that between 6 to 15 functional groups exist for all taxa examined, with the most useful and statistically robust partitions being around 7 groups. The abundance of these groups responds differently to environmental conditions along the tropical to temperate gradient, with some groups decreasing with latitude (e.g. tropical groups) and others maintaining their abundance, but not their composition, across the gradient. Looking at how these groups’ abundance will change in the future, TRIM finds that the groups of non-habitat builders (fishes, molluscs, echinoderms) lag in their movement behind that of structural taxa (corals, algae).

Under the conservation objective, TRIM has experimented with a triage-type approach to conservation, where we focus on protecting areas with least climate exposure regardless of their biodiversity. This approach addresses climate change challenges, but still ignores the importance of considering ecological responses in climate change management. TRIM’s outputs also include a framework for including ecological responses and multiple climate stressors (not only temperature) in coral reef management, and is quantifying trait-based management options for a coral reef fishery in the Pacific.
TRIM has innovated in marine functional ecology in several regards. The research and results have pioneered the use of functional groups derived from species traits. It is the first to elucidate that both the choice of traits and species strongly influence the stability of marine functional groups, and species-group assignment. The distribution of functional groups shows strongly that tropical species dominate reef fish functional niches on tropical-temperate environmental gradients. Furthermore, TRIM has forecasted functional group range shifts across a tropical to temperate gradient and found common responses of groups from multiple taxa. In the conservation arena is where these results, and findings from TRIM’s conservation objectives, will have wider societal implications. In this field, TRIM outputs include work recommending novel approaches to designing marine protected areas under climate change, and the development of trait-based management of marine resources.
Reef wall in the shallows supporting corallivorous fishes
Diverse coral reef wall with high functional integrity, Photo: Dani Ceccarelli