How does sediment exposure affect corals? A systematic review protocol

Abstract

Background Local management action to address coral-reef stressors can improve reef health and mitigate the effects of global climate change. Coastal development and runoff lead to sedimentation, which directly impacts coral recruitment, growth, mortality, and the ecosystem services that coral reefs provide. Decision making for reef resilience in the face of global and local stressors requires information on thresholds for management action. In response to needs identified by reef managers, we plan to conduct a systematic review and meta-analysis that will explore the effects of both deposited and suspended sediment on corals to identify single and interacting stressor thresholds. We will identify levels of sediment exposure (i.e., concentration, duration, and frequency) that cause adverse physical, physiological, behavioral, developmental, and ecological responses in coral and describe geographic and taxonomic patterns in these responses. Our ultimate goal is to provide managers with sediment exposure thresholds that can be expected to cause these responses. Methods Our systematic review will synthesize available evidence on the effects of suspended and deposited sediment on corals. The research questions were formulated with an advisory team to support management decisions concerning local reef stressors in waters under U.S. federal jurisdiction. While the advisory team is most concerned with reefs adjacent to U.S. Pacific Islands, our review will include studies that examine reef-building coral species around the world. We will search online databases and grey literature to obtain a list of potential studies, assess their relevance, and critically appraise them for validity and risk of bias. Provided enough data can be extracted from relevant experimental studies, we will conduct meta-analyses that examine changes in coral health and survival in response to suspended and/or deposited sediment, with the goal to define sediment thresholds for reef managers. If enough data are available from within the U.S. Pacific Islands, we will construct region-, site-, and/or species-specific thresholds to improve local management.

Microbiomes of Healthy and Bleached Corals During a 2016 Thermal Bleaching Event in the Upper Gulf of Thailand

“…In this study, different prokaryotic and eukaryotic microbiomes were found across different coral genera in healthy vs. bleached conditions. The greatest alpha diversity of prokaryotic OTUs was observed in sediments beneath the corals, which previous research reported the sediment may affect coral rates of growth, photosynthesis, larval settlement and survival, coral bleaching, and mortality (Tuttle et al, 2020). Sediment bacteria could play a role providing and/or recycling nutrient resources for coral growth/reproduction.…”

Effects of sediment exposure on corals: a systematic review of experimental studies

“…Few deviations were made from the previously published, a priori systematic review protocol [ 30 ]. Given that we employed a small team, we provide more detail about how we ensured repeatable and consistent decisions during different stages of the review, especially article screening, data extraction, and study validity assessment.…”

“…These additional genera were important because of their importance in the Pacific region under U.S. jurisdiction, as indicated by our NOAA advisory team: Alveopora, Astreopora, Favia, Favites, Goniastrea, Goniopora, Leptastrea, Leptoria, Lobophyllia, Millepora, Platygyra, Pocillopora, and Turbinaria . The following search string in English uses Boolean operators and wildcards to improve the quality (i.e., true positive results) of search results and was tested for its comprehensiveness [ 30 ], shown in Additional file 2 along with slight modifications to the syntax of the search term, which were necessary for different databases:…”

“…In response to needs identified by the Pacific Islands Regional Office (PIRO) of the U.S. Department of Commerce’s National Oceanic and Atmospheric Administration (NOAA), we conducted a systematic review and meta-analysis that identified thresholds of coral response to both deposited and suspended sediment, bringing to bear the most current and comprehensive information for regulatory decision-making. Specific research questions and a protocol were developed by an advisory team at NOAA in conjunction with a research team from the University of Hawai‘i [ 30 ]. The UH research team then conducted the systematic review and meta-analysis, the results of which we report here, with minimal changes to the original protocol (see Methods ).…”

The coral conservation crisis: interacting local and global stressors reduce reef resiliency and create challenges for conservation solutions

“…Nonetheless, recovery and stabilization of coral cover was attributed to reduced sedimentation from watershed restoration [87]. While recovery is possible, certain taxonomic groups of corals have different thresholds of sediment exposure, including concentration, duration, and frequency; therefore, coral community composition may be determined by species-specific sediment tolerance thresholds [88]. Alongside coastal development, sediment exposure is amplified from dredging activity and has both synergistic and antagonistic effects with thermal stress from global climate change [89].…”