In contrast to other seagrass meadows where seawater carbonate chemistry generally shows strong diel variations with higher pH but lower partial pressure of CO2 (pCO2) during the daytime and lower pH but higher pCO2 during nighttime due to the alternation in photosynthesis and respiration, the seagrass meadows of the inner lagoon (IL) on Dongsha Island had a unique diel pattern with extremely high pH and low pCO2 across a diel cycle. We suggest that this distinct diel pattern in pH and pCO2 could be associated with the enhancement of total alkalinity (TA) production coupled to carbonate sediment dissolution in a semienclosed lagoon. The confinement of the IL may hamper water exchange and seagrass detritus export to the adjacent open ocean, which may result in higher organic matter loading to the sediments, and longer residence time of the water in the IL, accompanied by microbial respiration (both aerobic and anaerobic) that may reduce carbonate saturation level to drive carbonate dissolution and thus TA elevation, thereby forming such a unique diel pattern in carbonate chemistry. This finding further highlights the importance of considering TA production through metabolic carbonate dissolution when evaluating the potential of coastal blue carbon ecosystems to buffer ocean acidification and to absorb atmospheric CO2, in particular in a semienclosed setting.
Continue reading ‘A unique diel pattern in carbonate chemistry in the seagrass meadows of Dongsha island: the enhancement of metabolic carbonate dissolution in a semienclosed lagoon’Posts Tagged 'tracheophyta'
A unique diel pattern in carbonate chemistry in the seagrass meadows of Dongsha island: the enhancement of metabolic carbonate dissolution in a semienclosed lagoon
Published 15 November 2021 Science ClosedTags: biogeochemistry, chemistry, field, North Pacific, phanerogams, sediment, tracheophyta
A unique diel pattern in carbonate chemistry in the seagrass meadows of Dongsha island: implications for ocean acidification buffering
Published 13 November 2020 Science ClosedTags: biogeochemistry, chemistry, field, North Pacific, phanerogams, tracheophyta
In contrast to most seagrass meadows where seawater carbonate chemistry generally shows strong diel variations with a higher pH during the daytime and a lower pH during nighttime due to the alternation in photosynthesis and respiration, the seagrass meadows of the inner lagoon on Dongsha Island had a unique diel pattern with an extremely high pH across a diel cycle. We suggest that this distinct diel pattern in pH was a result of a combination of total alkalinity (TA) production through the coupling of aerobic/anaerobic respiration and carbonate dissolution in the sediments and dissolved inorganic carbon consumption through the high productivity of seagrasses in overlying seawaters. The confinement of the semienclosed inner lagoon may hamper water exchange and seagrass detritus export to the adjacent open ocean, which may provide an ideal scenario for sedimentary TA production and accumulation, thereby forming a strong capacity for seagrass meadows to buffer ocean acidification.
Continue reading ‘A unique diel pattern in carbonate chemistry in the seagrass meadows of Dongsha island: implications for ocean acidification buffering’A future 1.2 °C increase in ocean temperature alters the quality of mangrove habitats for marine plants and animals
Published 15 July 2019 Science ClosedTags: abundance, algae, biological response, BRcommunity, field, fish, mesocosms, morphology, multiple factors, otherprocess, performance, South Pacific, tracheophyta
Highlights
• Mangrove habitats are more resilient to climate change than other habitats.
• Climate change might have positive effects on mangrove-root species communities.
• Using mesocosms we show that an increase of 1.2 °C leads to community homogenisation.
• Warming also led to diversity loss and flattening of mangrove root epibiont communities.
• Juvenile fish altered their use of mangrove habitats under warming and acidification.
Abstract
Global climate stressors, like ocean warming and acidification, contribute to the erosion of structural complexity in marine foundation habitats by promoting the growth of low-relief turf, increasing grazing pressure on structurally complex marine vegetation, and by directly affecting the growth and survival of foundation species. Because mangrove roots are woody and their epibionts are used to ever-changing conditions in highly variable environments, mangrove habitats may be more resilient to global change stressors than other marine foundation species. Using a large-scale mesocosm experiment, we examined how ocean warming and acidification, under a reduced carbon emission scenario, affect the composition and structural complexity of mangrove epibiont communities and the use of mangrove habitat by juvenile fishes. We demonstrate that even a modest increase in seawater temperature of 1.2 °C leads to the homogenisation and flattening of mangrove root epibiont communities. Warming led to a 24% increase in the overall cover of algal epibionts on roots but the diversity of the epibiont species decreased by 33%. Epibiont structural complexity decreased owing to the shorter stature of weedy algal turfs which prospered under elevated temperature. Juvenile fishes showed alterations in mangrove habitat use with ocean warming and acidification, but these were independent of changes to the root epibiont community. We reveal that the quality of apparently resilient mangrove habitats and their perceived value as habitat for associated fauna are still vulnerable under a globally reduced carbon emission scenario.
