AUTHOR=Mishra Amrit K. , Silva João , Santos Rui TITLE=Short Term CO2 Enrichment Increases Carbon Sequestration of Air-Exposed Intertidal Communities of a Coastal Lagoon JOURNAL=Frontiers in Marine Science VOLUME=4 YEAR=2018 URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2017.00439 DOI=10.3389/fmars.2017.00439 ISSN=2296-7745 ABSTRACT=

In situ production responses of air-exposed intertidal communities under CO₂ enrichment are reported here for the first time. We assessed the short-term effects of CO₂ on the light responses of the net community production (NCP) and community respiration (CR) of intertidal Z. noltei and unvegetated sediment communities of Ria Formosa lagoon, when exposed to air. NCP and CR were measured in situ in summer and winter, under present and CO₂ enriched conditions using benthic chambers. Within chamber CO₂ evolution measurements were carried out by a series of short-term incubations (30 min) using an infra-red gas analyser. Liner regression models fitted to the NCP-irradiance responses were used to estimate the seasonal budgets of air-exposed, intertidal production as determined by the daily and seasonal variation of incident photosynthetic active radiation. High CO₂ resulted in higher CO₂ sequestration by both communities in both summer and winter seasons. Lower respiration rates of both communities under high CO₂ further contributed to a potential negative climate feedback, except in winter when the CR of sediment community was higher. The light compensation points (LCP) (light intensity where production equals respiration) of Z. noltei and sediment communities also decreased under CO₂ enriched conditions in both seasons. The seasonal community production of Z. noltei was 115.54 ± 7.58 g C m⁻² season⁻¹ in summer and 29.45 ± 4.04 g C m⁻² season⁻¹ in winter and of unvegetated sediment was 91.28 ± 6.32 g C m⁻² season⁻¹ in summer and 25.83 ± 4.01 g C m⁻² season⁻¹ in winter under CO₂ enriched conditions. Future CO₂ conditions may increase air-exposed seagrass production by about 1.5-fold and unvegetated sediments by about 1.2-fold.