Biogenic habitat shifts under long-term ocean acidification show nonlinear community responses and unbalanced functions of associated invertebrates

Experiments have shown that increasing dissolved CO2 concentrations (i.e. Ocean Acidification, OA) in marine ecosystems may act as nutrient for primary producers (e.g. fleshy algae) or a stressor for calcifying species (e.g., coralline algae, corals, molluscs). For the first time, rapid habitat domi...

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Bibliographic Details
Published in:The Science of the total environment 2019-06, Vol.667, p.41-48
Main Authors: Milazzo, M., Alessi, C., Quattrocchi, F., Chemello, R., D'Agostaro, R., Gil, J., Vaccaro, A.M., Mirto, S., Gristina, M., Badalamenti, F.
Format: Article
Language:English
Subjects:
Animals
Biodiversity
Carbon dioxide
Carbon Dioxide - analysis
CO2 vents
Ecosystem
Invertebrates - physiology
Italy
Mediterranean Sea
Models, Biological
Nonlinear Dynamics
Ocean acidification
Oceans and Seas
Phase shift
Seawater - analysis
Snails - physiology
Transplant
Vermetid reef
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Summary:Experiments have shown that increasing dissolved CO2 concentrations (i.e. Ocean Acidification, OA) in marine ecosystems may act as nutrient for primary producers (e.g. fleshy algae) or a stressor for calcifying species (e.g., coralline algae, corals, molluscs). For the first time, rapid habitat dominance shifts and altered competitive replacement from a reef-forming to a non-reef-forming biogenic habitat were documented over one-year exposure to low pH/high CO2 through a transplant experiment off Vulcano Island CO2 seeps (NE Sicily, Italy). Ocean acidification decreased vermetid reefs complexity via a reduction in the reef-building species density, boosted canopy macroalgae and led to changes in composition, structure and functional diversity of the associated benthic assemblages. OA effects on invertebrate richness and abundance were nonlinear, being maximal at intermediate complexity levels of vermetid reefs and canopy forming algae. Abundance of higher order consumers (e.g. carnivores, suspension feeders) decreased under elevated CO2 levels. Herbivores were non-linearly related to OA conditions, with increasing competitive release only of minor intertidal grazers (e.g. amphipods) under elevated CO2 levels. Our results support the dual role of CO2 (as a stressor and as a resource) in disrupting the state of rocky shore communities, and raise specific concerns about the future of intertidal reef ecosystem under increasing CO2 emissions. We contribute to inform predictions of the complex and nonlinear community effects of OA on biogenic habitats, but at the same time encourage the use of multiple natural CO2 gradients in providing quantitative data on changing community responses to long-term CO2 exposure. [Display omitted] •Carbon dioxide (CO2) may act as a stressor or a resource for marine ecosystems.•Vermetid reef communities were transplanted along CO2 gradients for 1 year.•Rapid dominance shifts from a reef- to a non-reef-forming habitat were documented.•Community-level changes were nonlinear and the food web simplified under increasing CO2.•CO2 disrupts the state of intertidal communities.
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2019.02.391