Archive for coral reefs

Sensitivity of future ocean acidification to carbon-climate feedbacks

Posted by mmaheigan 
· Thursday, May 10th, 2018 

There are vast unknowns about the future oceans, from what species or habitats may be most under threat to the continuity of earth system processes that maintain global climate. Modeling can be used to predict future states and explore the impacts of climate change, but several key uncertainties such as carbon-climate feedbacks hamper our predictive power.

Authors of a recent study in Biogeosciences (Matear and Lenton 2018) used a global earth system model to explore the effects of carbon-climate feedbacks on future ocean acidification. Ocean acidification can have wide-ranging impacts on keystone species from reef-building corals to pteropods, a major food web species in the Southern Ocean. The study included four representative scenarios (from IPCC) comparing concentration pathway simulations to emission pathway simulations (RCP2.6, RCP 4.5, RCP6, RCP8.5) to determine carbon-climate feedbacks. The high emission scenarios (RCP8.5 and RCP6) showed surface water undersaturation a decade or more earlier than expected. Surprisingly, the medium (RCP4.5) scenario carbon-climate feedbacks showed the greatest acidification response, doubling the extent of undersaturation and subsequently halving the area that could sustain coral reefs by 2100. The low emissions scenario also showed significant declines in saturation state.

Surface ocean aragonite saturation state for the 2090s for RCP2.6 and RCP 8.5 concentration and emission pathways. The contour line delineates a saturation state of 3 (coral reef threshold), the white line a saturation state of 1, when aragonite becomes unstable and corals dissolve.

The extra atmospheric CO2 from the carbon-climate feedback resulted in accelerated ocean acidification in all emission scenarios. These feedbacks may also affect global warming and deoxygenation. This is particularly important, given that many policymakers are aiming for low emission commitments, but may still be severely underestimating the extent and timing of ocean acidification. There is a great need to improve our ability to predict carbon-climate feedbacks so we do not underestimate projected ocean acidification and its impacts on both sensitive ecosystems and the human communities that rely on them for food, coastal protection and other ecosystem services.

Authors:
Richard Matear (CSIRO Oceans and Atmosphere, Australia)
Andrew Lenton (Antarctic Climate and Ecosystems CRC, Australia)

An autonomous approach to monitoring coral reef health

Posted by mmaheigan 
· Thursday, July 20th, 2017 

Coral reefs are diverse, productive ecosystems that are highly vulnerable to changing ocean conditions such as acidification and warming. Coral reef metabolism—in particular the fundamental ecosystem properties of net community production (NCP; the balance of photosynthesis and respiration) and net community calcification (NCC; the balance of calcification and dissolution)—has been proposed as a proxy for reef health. NCC is of particular interest, since ocean acidification is expected to have detrimental effects on reef calcification.

Traditionally, these metabolic rates are quantified through laborious methods that involve discrete sampling, which, due to a limited number of observations, often fails to characterize natural variability on time scales of minutes to days. In a recent paper in JGR, Takeshita et al. (2016) presented the Benthic Ecosystem and Acidification Measurement System (BEAMS), a fully autonomous system that simultaneously measures NCP and NCC at 15-minute intervals over a period of weeks. BEAMS utilizes the gradient flux method to quantify benthic metabolic rates by measuring chemical (pH and O2) and velocity gradients in the turbulent benthic boundary layer.

Two BEAMS were simultaneously deployed on Palmyra Atoll located approximately one km apart over vastly different benthic communities. One site was a healthy reef with approximately 70% coral cover, and the other was a degraded reef site with only 5% coral cover that was dominated by a non-calcifying invasive corallimorph Rhodactis howesii. Over the course of two weeks, BEAMS collected over 1,000 measurements of NCP and NCC from each site, yielding significantly different ratios of NCP to NCC between the two sites. These initial results suggest that BEAMS is capable of detecting different metabolic states, as well as patterns consistent with degrading reef health.

BEAMS is an exciting new autonomous tool to monitor reef health and study drivers of reef metabolism on timescales ranging from minutes to months (and potentially years). Additionally, autonomous measurement tools increase the potential for widespread and comparable observations across reefs and reef systems. Such knowledge will greatly improve our ability to predict the fate of coral reefs in a changing ocean.

 

Authors: 
Yui Takeshita (Monterey Bay Aquarium Research Institute)

Filter by Keyword

abundance acidification africa air-sea interactions algae alkalinity allometry ammonium AMOC anoxic Antarctic anthro impacts anthropogenic carbon aquaculture aquatic continuum aragonite saturation arctic Argo argon arsenic artificial seawater Atlantic atmospheric CO2 atmospheric nitrogen deposition authigenic carbonates autonomous platforms bacteria bathypelagic BATS BCG Argo benthic bgc argo bio-go-ship bio-optical bioavailability biogeochemical cycles biogeochemical models biogeochemistry Biological Essential Ocean Variables biological pump biophysics bloom blue carbon bottom water boundary layer buffer capacity C14 CaCO3 calcification calcite carbon carbon-climate feedback carbon-sulfur coupling carbon budget carbon cycle carbon dioxide carbon export carbon sequestration carbon storage Caribbean CCA CCS changing marine ecosystems changing marine environments changing ocean chemistry chemical oceanographic data chemical speciation chemoautotroph chesapeake bay chl a chlorophyll circulation climate change climate variability CO2 coastal darkening coastal ocean cobalt Coccolithophores community composition conservation cooling effect copepod coral reefs CTD currents cyclone daily cycles data data access data assimilation data management data product Data standards DCM dead zone decadal trends decomposers decomposition deep convection deep ocean deep sea coral deoxygenation depth diatoms DIC diel migration diffusion dimethylsulfide dinoflagellate discrete measurements DOC DOM domoic acid dust DVM ecology ecosystems eddy Education Ekman transport emissions ENSO enzyme equatorial regions ESM estuarine and coastal carbon fluxes estuary euphotic zone eutrophication evolution export export fluxes export production EXPORTS extreme events faecal pellets filter feeders filtration rates fire fish Fish carbon fisheries floats fluid dynamics fluorescence food webs forage fish forams freshening freshwater frontal zone functional role future oceans geochemistry geoengineering geologic time GEOTRACES glaciers gliders global carbon budget global ocean global warming go-ship grazing greenhouse gas Greenland ground truthing groundwater Gulf of Maine Gulf of Mexico Gulf Stream gyre harmful algal bloom high latitude human food human impact hurricane hydrogen hydrothermal hypoxia ice age ice cores ice cover industrial onset inland waters inverse circulation ions iron iron fertilization isotopes jellies katabatic winds kelvin waves krill kuroshio lab vs field land-ocean continuum larvaceans lateral transport LGM lidar ligands light light attenuation lipids machine learning mangroves marine carbon cycle marine heatwave marine particles marine snowfall marshes Mediterranean meltwater mesopelagic mesoscale metagenome metals methane methods microbes microlayer microorganisms microscale microzooplankton midwater mixed layer mixed layers mixing mixotrophy model modeling model validation mode water molecular diffusion MPT multi-decade n2o NAAMES NASA NCP net community production net primary productivity new ocean state new technology Niskin bottle nitrate nitrogen nitrogen cycle nitrogen fixation nitrous oxide north atlantic north pacific nuclear war nutricline nutrient budget nutrient cycling nutrient limitation nutrients OA ocean-atmosphere ocean acidification ocean acidification data ocean carbon uptake and storage ocean color ocean modeling ocean observatories ocean warming ODZ oligotrophic omics OMZ open ocean optics organic particles oscillation overturning circulation oxygen pacific paleoceanography parameter optimization particle flux pCO2 PDO peat pelagic PETM pH phenology phosphorus photosynthesis physical processes physiology phytoplankton PIC piezophilic piezotolerant plankton POC polar regions policy pollutants precipitation predation prediction pressure primary productivity Prochlorococcus prokaryotes proteins pteropods pycnocline radioisotopes remineralization remote sensing repeat hydrography residence time resource management respiration resuspension rivers rocky shore Rossby waves Ross Sea ROV salinity salt marsh satellite scale seafloor seagrass sea ice sea level rise seasonal patterns seasonal trends sea spray seawater collection seaweed sediments sensors shelf system shells ship-based observations shorelines silicate silicon cycle sinking particles size SOCCOM soil carbon southern ocean south pacific spatial covariations speciation SST state estimation stoichiometry subduction submesoscale subpolar subtropical sulfate surf surface surface ocean Synechococcus teleconnections temperate temperature temporal covariations thermocline thermodynamics thermohaline thorium tidal time-series time of emergence titration top predators total alkalinity trace elements trace metals trait-based transfer efficiency transient features Tris trophic transfer tropical turbulence twilight zone upper ocean upper water column upwelling US CLIVAR validation velocity gradient ventilation vertical flux vertical migration vertical transport volcano warming water clarity water mass water quality waves western boundary currents wetlands winter mixing zooplankton

Copyright © 2023 - OCB Project Office, Woods Hole Oceanographic Institution, 266 Woods Hole Rd, MS #25, Woods Hole, MA 02543 USA Phone: 508-289-2838  •  Fax: 508-457-2193  •  Email: ocb_news@us-ocb.org

link to nsflink to noaalink to WHOI

Funding for the Ocean Carbon & Biogeochemistry Project Office is provided by the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA). The OCB Project Office is housed at the Woods Hole Oceanographic Institution.