Establishing microbial baselines to identify indicators of coral reef health

Abstract

Microorganisms make a significant contribution to reef ecosystem health and resilience via their critical role in mediating nutrient transformations, their interactions with macro-organisms and their provision of chemical cues that underpin the recruitment of diverse reef taxa. However, environmental changes often cause compositional and functional shifts in microbial communities that can have flow-on consequences for microbial-mediated processes. These microbial alterations may impact the health of specific host organisms and can have repercussions for the functioning of entire coral ecosystems. Assessing changes in reef microbial communities should therefore provide an early indicator of ecosystem impacts and would underpin the development of diagnostic tools that could help forecast shifts in coral reef health under different environmental states. Monitoring, management and active restoration efforts have recently intensified and diversified in response to global declines in coral reef health. Here we propose that regular monitoring of coral reef microorganisms could provide a rapid and sensitive platform for identifying declining ecosystem health that can complement existing management frameworks. By summarising the most common threats to coral reefs, with a particular focus on the Great Barrier Reef, and elaborating on the role of microbes in coral reef health and ecosystem stability, we highlight the diagnostic applicability of microbes in reef management programs. Fundamental to this objective is the establishment of microbial baselines for Australia's coral reefs.

On a Reef Far, Far Away: Anthropogenic Impacts Following Extreme Storms Affect Sponge Health and Bacterial Communities

“…Our findings clearly demonstrate the urgent need for: (1) continued mitigation of stormwater runoff and climate change impacts; and (2) establishment of surface and benthic microbial and water quality time series for near-and offshore reefs using standardized protocols. This latter program will ideally generate baseline data on the gene expression and microbiomes of key benthic reef taxa under normal conditions, providing critical context (Glasl et al, 2018a) in which to detect and mitigate floodwater-derived stress on reefs in order to understand their impact on benthic invertebrate physiology and reef ecosystem functions.…”

Microbial and nutrient dynamics in mangrove, reef, and seagrass waters over tidal and diurnal time scales

“…Thus, long-term sampling schemes aimed at characterizing the nutrient and microbial diversity of a location should consider the importance of short temporal variation and at least sample over a few diel cycles to account for this variability and evaluate its consistency (or lack thereof) over time. Sampling schemes designed to characterize microbial communities and biogeochemistry may be particularly important for monitoring the health and stability of the region within marine reserves, a concept that has had success in coral reef environments (Glasl et al 2017(Glasl et al , 2018. To alleviate misleading results that may stem from sampling design, we suggest that accounting for tidal or diurnal forces is important in these coastal areas.…”

“…The diverse assemblage of microorganisms is particularly important in reef seawater for recycling organic metabolites and nutrients in these apparent nutrient 'deserts' (Gast et al 1998, Bourne & Webster 2013, Haas et al 2013. The fundamental role that microbes play in coral reef biogeochemical cycling has made them bioindicators of changing reef environments in the face of climate change (Glasl et al 2018). While it is established that seawater microbial communities on reefs alter predictably with seasonal shifts in environmental parameters (Bulan et al 2018, Glasl et al 2019, much less is known on how short temporal scales, on the orders of hours and days, impact reef seawater communities.…”

Disentangling the complex microbial community of coral reefs using standardized Autonomous Reef Monitoring Structures (ARMS)

“…Currently, conservation measures are mainly based on the responses of macro‐organisms such as changes in coral coverage and fish abundance and/or biomass (Hill & Wilkinson, ), but these are likely to respond to the presence and absence of prokaryotic organisms, which are vital players to reef functioning (Glasl, Bourne, Frade, & Webster, ). Our study highlights that a standardized methodology, which can be applied on a global scale, can provide insight into coral reef microbial communities (free‐living, benthic and organism‐associated) and determine differences along environmental gradients.…”