Abstract
BackgroundTropical coral reefs cover only ca. 0.1% of the Earth’s surface but host an outstanding biodiversity and provide important ecosystem services to millions of people living nearby. They are currently threatened by global (e.g., climate change) and local (e.g., chemical pollution) stressors that interact in different ways. While global stressors cannot be mitigated by local actions alone, local stressors can be reduced through ecosystem management. A systematic map on the impacts of chemicals arising from anthropogenic activities on tropical reef-building corals, which are the main engineer species of reef ecosystems, was published in 2021. This systematic map gathered an abundant literature (908 articles corresponding to 7937 studies), and identified four well-represented subtopics, amenable to relevant full syntheses. Here, we focused on one of the four subtopics: we aimed to systematically review the evidence on the ecotoxicological effects of chemicals on tropical reef-building corals.MethodsThe evidence will be identified from the recent systematic map on the impacts of chemicals arising from anthropogenic activities on tropical reef-building corals. Especially, all studies in the map database corresponding to the knowledge cluster “evidence on the ecotoxicological effects of chemicals on corals” will be selected. To identify the evidence produced since then, a search update will be performed using a subset of the search string used for the systematic map, and titles, abstracts and full-texts will be screened according to the criteria defining the selected cluster of the map. In addition, as the eligibility criteria for the systematic review are narrower than those used to define the cluster in the systematic map, additional screening will be carried out. The included studies will then be critically appraised and a low, medium, or high risk of bias will be assigned to each study. Data will be extracted from studies and synthesised according to a strategy depending on the type of exposure and outcome. Synthesis will be mainly quantitative but also narrative, aiming to identify toxicity thresholds of chemicals for corals.
Highlights
Tropical coral reefs cover only ca. 0.1% of the Earth’s surface but host an outstanding biodiversity and provide important ecosystem services to millions of people living nearby
While the most prominent global threats are represented by seawater warming and acidification [9], local threats are mainly represented by unsustainable or destructive development of coastal areas, excess sedimentation, overfishing, as well as nutrient and chemical pollution resulting from poor land management, urbanisation, agriculture and industry [10, 11]
The health of reef ecosystems is largely based on the health of their main engineer species, the reef-building corals, which are key organisms responsible for reef accretion and form the three-dimensional structures serving as habitat, food, and nursery for thousands of other reef organisms [12]
Summary
The systematic review will follow the Collaboration for Environmental Evidence Guidelines and Standards for Evidence Synthesis in Environmental Management [34] and this protocol conforms to ROSES reporting standards [35] (see Additional file 1). For all exposure categories and for outcomes related to coral mortality, growth, settlement, fertilisation, symbiont density (bleaching) and photosynthesis performance, quantitative data will be extracted from text, tables and figures. Because relatively few quantitative results are expected to be available for these categories, a narrative synthesis of the findings of individual primary studies will be produced to provide additional information for these exposure categories This narrative synthesis will be conducted for the outcome categories that will not undergo extraction of quantitative results, and will not concern the categories Hydrocarbon, Metal, and Pesticide, due to limited resources and time (Table 4). Narrative synthesis A narrative synthesis of the findings of individual primary studies will be produced for the exposure categories Detergent, Dispersant, Microplastic, Nanoparticle, Pharmaceutical, UV filter, and Other, and for the outcome categories that will not undergo extraction of quantitative results (Table 4). The list of all studies not included in the quantitative or the narrative synthesis of the findings will be provided with reason of why they could not be included
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