Carbonate chemistry and coral reefs in a seasonal upwelling system: insights into ocean acidification scenarios

Chair: Ulf Riebesell

Celeste Sánchez-Noguera1,2,3, Ines Stuhldreier3,4, Carlos Jiménez1,5, Jorge Cortés1, Álvaro Morales1, Christian Wild3,4, Tim Rixen2,3

 

1 Centro de Investigación en Ciencias del Mar y Limnología (CIMAR), San Pedro,

11501-2060, San José, Costa Rica

2 Institute of Geology, University Hamburg, Hamburg, 20146, Germany

3 Leibniz Center for Tropical Marine Ecology (ZMT), Bremen, 28359, Germany

4 Faculty of Biology and Chemistry (FB2), University of Bremen, Bremen, 28359, Germany

5 Energy, Environment and Water Research Center (EEWRC) of The Cyprus

Institute (Cyl), Nicosia, CY-1645, Cyprus

 

Background:

Ocean acidification (OA) threatens coral growth and the future of coral reefs is still difficult to predict. Since reefs in the Eastern Tropical Pacific (ETP) are naturally exposed to acidic conditions during upwelling events and thus adapted to low pH, they are excellent locations to investigate thresholds of reef accretion under OA scenarios

Methods:

Culebra Bay, northern Pacific coast of Costa Rica, is a seasonal upwelling area. We characterised the carbonate chemistry in the bay during non-upwelling and upwelling season by deploying SAMI-sensors (pH and pCO2) and an underway pCO2 system (SUNDANS).

Findings:

As in other coral reefs, photosynthesis/respiration and calcification/dissolution produced a pronounced pCO2 diurnal cycle. During non-upwelling season, inputs of corrosive offshore waters superimposed this diurnal cycle and raised the pCO2 (658

µatm) to similar levels  as  those  occurring  during  upwelling  season  (645  µatm).

Associated changes in diurnal cycle of pH and pCO2 indicated that dissolution might exceed calcification during daytime, if corrosive waters enter the bay. Linear extension  rates  of  main  reef  building  corals  at  upwelling  locations  in  the  ETP correlate to Ωa, and growth in Culebra Bay is near zero when Ωa falls below 2.5.

Conclusions:

Mean  Ωa    occurring  during  upwelling  (2.68)  and  non-upwelling  season  (3.41) suggests that coral growth is mainly favoured during non-upwelling. The overall low reef accretion in the region reveals a sensitive balance between carbonate accumulation and dissolution. Inputs of corrosive waters during cold upwelling but

also during the comparable warm non-upwelling season could shift the system towards net dissolution. This supports studies linking reef gaps in the geological record of the ETP to periods of enhanced upwelling. Our results furthermore suggest that in addition to seasonal upwelling, advection of corrosive offshore waters during non-upwelling season may play an important role by hampering coral growth during the main growing season.

Living Coccolithophores in China Sea Waters: the Diversity and Distribution

Chair: Victoria Cole

Jun Sun (1)

1 College of Marine and Environmental Science, Tianjin University of Science and Technology, Tianjin, 300457, China

Background
Living coccolithophores are very important marine phytoplankton functional group, playing crucial role in the marine carbon cycle. Recently studies suggested that their calcification process is susceptible to global climate change, especially ocean acidification.

Methods
We investigated the morphology, taxonomy, diversity and distribution of living coccolithophores in the China Sea Waters the first time. Samples were collected from a series of comprehensive invesigations including hydrology, geology, chemistry and biology in the Bohai Sea, Yellow Sea, East China Sea and South China Sea over years.

Findings
97 species were recorded, belonging to 4 orders, 11 families, and 44 genera. Genus Syracosphaera (20 species observed) presented the highest species-richness in the CSW. The overall coccoliphore abundance in the research areas ranged from 3 to 20 cells/ml. The dominant coccoliphore species were Gephyrocapsa oceanica, Emiliania huxleyi, Helicosphaera carteri, and Algirosphaera robusta, in the order of species abundance. The total coccoliphore abundance was highest in the East China Sea, followed by the South China Sea, Yellow Sea, Northern Yellow Sea and Bohai Sea. Seasonally, the coccoliphore were most abundant in autumn, followed by spring, winter and summer. Temperature and nitrate concentration may be the major environmental factors controlling the distribution and species composition of coccoliphores in the studying areas based on canonical correspondence analysis.

Conclusions
These findings provide information on the contribution of coccolithophores to the biological carbon pump in the China Seas and the controlling environmental factors on their distribution, and thus help to understand how the natural coccolithophore community will respond to the global climate change in the China Sea Waters.

Phytoplankton community composition and succession at increasing levels of atmospheric carbon dioxide: insights from mesocosm studies

Chair: Jean-Pierre Gattuso

K. G. Schulz(1,2), R. G. J. Bellerby(3,4), R. Bermúdez(2,5), J. Büdenbender(2), T. Boxhammer(2), J. Czerny(2), A. Engel(2), S. Febiri(2), A. Ludwig(2), M. Meyerhöfer(2), A. Larsen(6), A. Paul(2), M. Sswat(2), and U. Riebesell(2)

1 Centre for Coastal Biogeochemistry, School of Environment, Science and Engineering, Southern Cross University, P.O. Box 157, Lismore, NSW 2480, Australia
2 GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
3 SKLEC-NIVA Centre for Marine and Coastal Research, East China Normal University, Zhongshan N. Road, 3663, Shanghai 200062,China
4 Norwegian Institute for Water Research, Regional Office Bergen, Thormøhlensgate 53 D, N-5006 Bergen, Norway
5 Facultad de Ingeniería Marítima, Ciencias Biológicas, Oceánicas y Recursos Naturales. Escuela Superior Politécnica del Litoral, ESPOL, Guayaquil – Ecuador
6 Uni Research Environment, Bergen, Norway

Background
At the base of the marine food-web phytoplankton is a key player in the global carbon cycle with feedbacks to the climate system. Rising levels of atmospheric carbon dioxide (CO2), driven by a variety of human activities are changing climate and seawater carbonate chemistry by increasing CO2 levels and decreasing pH, termed ocean acidification. How this might affect marine phytoplankton in terms of abundance and species composition is a pressing question as such changes can influence marine productivity, transfer to higher trophic levels and modify marine export production.

Methods
To study the effects of ocean acidification on marine phytoplankton and potential impacts on ecosystem functioning and biogeochemical element cycling, experiments are required that enclose natural plankton communities as a whole. Several such larger-scale studies have been realised in the last years by mooring mesocosms containing up to 75 m3 of seawater each in sheltered areas. Here we will focus on the 2011 KOSMOS (Kiel Off-Shore Mesocosms for Ocean Simulations) campaign in the Raunefjord, Norway, where plankton community composition, particulate and dissolved organic matter production and loss was followed for five weeks in a gradient of CO2 levels ranging initially from 300 to 3000 μatm. Additionally, we will put the phytoplankton community composition resposnes into a perspective by comparing them with a number of other published experiments.

Findings
Direct and indirect effects of elevated CO2 and associated carbonate chemistry speciation were found on several phytoplankton groups, with picoeukaryotes (chlorophytes, cryptophytes) and Synechococcus being positively affected and the coccolithophore Emiliania huxleyi and diatoms in certain phases of the experiment being negatively impacted. These CO2 induced responses in phytoplankton community composition were reflected in net oxygen production and loss of particulate organic material into the sediment traps at 25m depth.

Conclusions
Ocean acidification can influence phytoplankton size and community structure with direct consequences for marine productivity and carbon export potential.

Galápagos Coral Reef Persistence after ENSO Warming across an Acidification Gradient

Chair: Ulf Riebesell

Derek Manzello (1)*, Ian Enochs (1,2), Andrew Bruckner (3), Philip Renaud (3), Graham Kolodziej (2), David Budd (4), Renee Carlton (2), Peter Glynn (5)

1 Atlantic Oceanographic and Meteorological Laboratory, NOAA, Miami, FL, 33149, USA
2 Cooperative Institute of Marine and Atmospheric Science, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, 33149, USA
3 Khaled bin Sultan Living Oceans Foundation, Annapolis, MD, 21403, USA
4 University of Colorado Boulder, Boulder, CO, 80309, USA
5 Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, 33149, USA

Background
Coral reefs are being severely impacted by warming and ocean acidification, yet we still have a relatively undeveloped understanding of how the combination of the two will impact coral reefs over this century. The coincidence of naturally high CO2 conditions, periodic warming events caused by ENSO, and long-term (~40 yrs) monitoring make Galápagos coral reefs ideal for understanding the effects of combined warming and acidification that is not possible at other high CO2 sites.

Methods
Seawater carbonate chemistry was measured with discrete samples and in situ instrumentation. Coral extension, density, calcification and skeletal P/Ca (a proxy for phosphate exposure) were determined from coral cores of massive Porites collected in June 2012.

Findings
Since the 1982-83 ENSO warming event, the persistence of reefs around the Galápagos Islands has differed across an acidification gradient. Reefs disappeared where pH < 8.0 and Ωarag ≤ 3 and have not recovered, whereas one reef has persisted where pH > 8.0 and Ωarag > 3. Where upwelling is greatest, calcification by massive Porites is greater than predicted by a published relationship with temperature despite high CO2, possibly due to elevated nutrients. However, skeletal P/Ca, a proxy for phosphate exposure, negatively correlates with density (R = -0.822, p < 0.0001).

Conclusions
Coral calcification and reef structural persistence correlate with the regional trend in seawater pH in the Galápagos. Increased nutrients may stimulate coral growth with high CO2, but the response of Galápagos reefs to warming suggests that elevated nutrients ultimately increase reef sensitivity to acidification by reducing skeletal density and further stimulating bioerosion already accelerated by low pH. The recent history of Galápagos coral reefs provides field evidence that reefs exposed to elevated nutrients may be the most affected and least resilient to changes in climate and ocean chemistry.

Global patterns of cleaning interactions in the ocean of tomorrow

Chair: Victoria Cole

José Ricardo Paula (1)*, Joana Boavida-Portugal (1,2), Alexandra S. Grutter (3), Miguel B. Araújo (3,4), Rui Rosa (1)

1 MARE – Marine and Environmental Sciences Centre, Laboratório Marítimo da Guia, Faculdade de Ciências da Universidade de Lisboa, Av. Nossa Senhora do Cabo, 939, 2750-374 Cascais, Portugal
2 CIBIO/InBio, Universidade de Évora, Largo dos Colegiais, 7000 Évora, Portugal
3 School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia
4 Imperial College London, Silwood Park, Buckhurst Road, Ascot SL5 7PY, Berkshire, United Kingdom

Background
Cleaning mutualisms are key ecological components in marine ecosystems and drivers of biodiversity and abundance. Nonetheless, until now, there is no knowledge on future climate change-driven changes in the global patterns of these cleaning interactions. Cleaner organisms remove ectoparasites from their so-called “clients” (usually larger reef fish) in complex interactions between multiple species. Climate change scenarios have predicted a significant sea surface temperature rise and a decrease in sea water pH by 2100 and marine species are expected to respond to this warming and acidification by shifting their latitudinal range and depth.

Methods
We used species distribution modelling to explore the potential impact of climate change, namely temperature, salinity, pH, O2 and primary productivity, on the habitat suitability of cleaner fishes. Using an ensemble forecast approach, we applied 6 different statistical models to project the potential distribution of 91 species cleaner fishes by 2100, under the Intergovernmental Panel for Climate Change (IPCC) AR5 RCP2.6 and RCP8.5 scenarios, implemented with an ensemble of 19 different Earth System Models.

Findings
When analysed without cleaning dependency we found significant losses in species suitability area around 70% and species richness per area around 60%. Facultative cleaners loss 70% of suitable area and species richness per area around 60%. We also observed a significant loss in obligatory cleaners suitable area (63%) and species richness (21%).

Conclusions
This is the first study to model habitat suitability of a crucial interspecific interaction may be affected by future climate change scenarios. As cleaner fish absence has been described as a main driver of biodiversity and abundance loss, these findings unravel a higher problem to communities as predicted shifts of cleaners presence might affect essential ecosystem stability around the globe.

In-situ community respiration and photosynthetic responses of Antarctic microphytobenthos to ocean acidification

Chair: Sean Connell

James Black (1)*, Andrew McMinn (2), John Runcie (3), Jonathan S. Stark (4)

1 Institute for Marine and Antarctic Studies, Hobart, Tasmania, 7000, Australia
2 Institute for Marine and Antarctic Studies, Hobart, Tasmania, 7000, Australia
3 Aquation Ptd Ltd, Umina Beach, NSW 2257, Australia
4 Australian Antarctic Division, Hobart, Tasmania, 7050, Australia

Background
Community respiration and primary production are both essential ecosystem processes, which influence many other aspects of ecosystems. Little is known however about in-situ ecosystem community respiration and benthic diatom photosynthetic responses to ocean acidification (OA), especially from soft sediment communities in the Antarctic. Recent developments in Free Ocean Carbon Enrichment (FOCE) technology has enabled in-situ investigations of ecosystem responses achievable. The current study investigated in-situ acute (<144hrs) and chronic (after 8 weeks) microphytobenthos (MPB) responses to OA using respiration chambers and antFOCE infrastructure, deployed parallel to antFOCE experiments.

Methods
In-situ experimental respiration and photosynthesis chambers were deployed on soft sediment MPB communities in Antarctica. Carbonate chemistry conditions were monitored via antFOCE equipment. Experiments were repeated five times under 400 ppm and 950 ppm CO2 conditions. Community respiration and the steady state fluorescence yield (ɸPSII) of benthic diatoms was measured with a novel shutter Pulse Amplitude Modulation (PAM) fluorescence device. Two automatic PAM measurements were made per hour measuring the vertical migration of the biomass and Deil yield (ɸPSII). Two PAR sensors recorded light continuously, enabling in-situ determination of relETR. Sediment cores sliced at 2mm intervals recorded biomass, species abundance and diatom cell size changes at the end of each experiment.

Findings
The MPB displayed an initial difference in behavioural photo tactile response and vertical migration, which increased with increasing light levels. Deil yield (ɸPSII) patterns were also higher in the 950 ppm treatment, relETR was unaffected.

Conclusions
Initial yield (ɸPSII) increases are believed to be an alleviation of the carbon limitation that occurs within dense MPB communities. Relaxing this constraint could result in higher growth rates in MPB communities. Furthermore, changes in photo-tactile responses and vertical migration is likely to change the distribution of extra cellular polysaccharides in the sediment, which plays an important role in preventing sediment erosion.

Global monitoring of marine biology and ecosystems to support detection of ocean acidification

Chair: Ken Caldeira

P. Miloslavich (1,2)*, N. Bax (3), S. Simmons (4), W. Appeltans (5)

1 Australian Institute of Marine Science, Townsville, Queensland, Australia
2 Universidad Simon Bolivar, Caracas, Venezuela
3 Commonwealth Scientific and Industrial Research Organisation (CSIRO), Hobart, Tasmania, Australia
4 Marine Mammal Commission, Bethesda, Maryland, USA
5 Intergovernmental Oceanographic Commission (IOC) of UNESCO, IOC Project Office for IODE, Oostende, Belgium

Background
The Biology and Ecosystems Panel of GOOS aims to develop and coordinate a global monitoring program of Essential Ocean Variables (EOVs) that is globally relevant and driven by societal needs to facilitate scientifically based policy development and management on ocean and coastal resources. Monitoring EOVs will help predict how marine biodiversity and ecosystems will change in the future under increasing anthropogenic pressures.

Methods
To identify biological and ecosystem EOVs the Panel (1) identified societal drivers and pressures requiring sustained global ocean observations by analysing the goals and societal issues addressed by major international bodies/conventions, (2) assessed current state of ocean observation of biological and ecosystem variables through a survey to the major global and large-scale regional observing networks or programs, and (3) considered existing frameworks for ocean observation.

Findings
Main drivers were knowledge (science/data access), development (sustainable economic growth), conservation (biodiversity and ecosystems), sustainable use (biodiversity and resources), environmental quality (health), capacity building (technology transfer), food security, threat prevention and impact mitigation (to different pressures), management improvement (integrate ecosystem approach). The main pressures identified were climate change, ocean acidification, extreme weather events, overfishing/overexploitation, pollution/eutrophication, mining, solid wastes.
The EOVs proposed through this process are: phytoplankton biomass and productivity, incidence of Harmful Algal Blooms (HABs), zooplankton diversity, fish distribution and abundance, apex predator abundance and distribution, live coral cover, seagrass cover, mangrove cover, and macroalgal canopy cover. The variables identified with the highest level of readiness for implementation at a global scale where those related to zooplankton and coral reefs.

Conclusions
By facilitating the monitoring of EOVs globally, GOOS is providing a process that increases robustness for collecting biological information that is of direct application on acidification studies (e.g. coral reefs, calcareous plankton, coralline algae), and that may also be useful to help advance our understanding of these processes.

Ocean acidification Impacts Primary and Bacterial Production in Antarctic Coastal Waters during Austral Summer

Chair: Sean Connell

Karen J. Westwood(1), Paul G. Thomson(2), Rick L. van den Enden(1), Lynsey E. Maher(3), Simon W. Wright(1), Andrew T. Davidson(
1)

1 Australian Antarctic Division, Hobart, Tasmania, 7050, Australia
2 The University of Western Australia, Perth, Western Australia, 6009, Australia
3 City of Hobart, Hobart, Tasmania, 7000, Australia

Background
Polar waters are at increased risk of ocean acidification (OA) due to the higher solubility of CO2 in colder waters.

Methods
Three experiments examining the influence of OA on primary and bacterial production were conducted during summer at Davis Station, Antarctica (68°35′ S, 77°58′ E). For each experiment, six 650 L tanks were simultaneously filled with 200 µm filtered coastal seawater and incubated for 10 to 12 days, with CO2 concentrations ranging from pre-industrial to post-2100. Primary and bacterial production rates were determined using NaH14CO3 and 14C-Leucine, respectively. Net community production (NCP) was determined using dissolved oxygen.

Findings
For all experiments, maximum photosynthetic rates (mg C mg chl a-1 h-1) decreased with enhanced CO2, reducing rates of gross primary production (mg C L-1 h-1). Rates of bacterial production (µg C L-1 h-1) and growth were faster under enhanced CO2 from Days 0-4, but became more similar between treatments thereafter. Conversely, rates of cell-specific productivity (µg C cell-1 h-1) decreased with enhanced CO2 and initial increases in bacterial production and growth were associated with fewer heterotrophic nanoflagellates. Reductions in primary and bacterial productivity with enhanced CO2 occurred at concentrations greater than 2X present day (> 780 ppm). The effect of OA on NCP varied with nitrate+nitrite (NOx) availability. At NOx concentrations < 1 µM photosynthesis to respiration ratios declined, with primary production reduced and responses to CO2 consequently suppressed.

Conclusions
OA may reduce primary production in Antarctic coastal waters, thereby reducing food availability to higher trophic levels and reducing draw-down of atmospheric CO2. NOx limitation may override this OA effect but cause a similar response. Under a global warming scenario where CO2 is expected to increase and nutrient fluxes to surface waters are expected to decrease due to strengthened stratification, NCP is predicted to decline.

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