Seagrasses account for approximately 10% of the ocean’s total carbon storage, although photosynthesis of seagrasses is carbon-limited at today’s oceanic pH. Therefore, increasing atmospheric CO2 concentration, which results in ocean acidification/carbonation, is predicted to have a positive impact on seagrass productivity. Previous studies have confirmed the positive influence of increasing CO2 on photosynthesis and survival of the temperate eelgrass Zostera marina, but the acclimation of photoprotective mechanisms in this context has not been characterized. This study aimed to quantify the long-term impacts of ocean acidification on photochemical control mechanisms that promote photosynthesis while simultaneously protecting eelgrass from photodamage. Eelgrass were grown in controlled outdoor aquaria at different aqueous CO2 concentrations ranging from ~50 to ~2100 μM from May 2013 to October 2014 and examined for differences in leaf optical properties. Even with daily and seasonal variations of temperature and light, CO2 enrichment consistently increased plant size, leaf thickness and chlorophyll use efficiency, and decreased pigment content and the package effect while maintaining similar light harvesting efficiency. These acclimation responses suggest a common photosynthetic sensory function, such as redox regulation, can be manipulated by CO2 availability, as well as light, and may serve to optimize photosynthetic carbon gain by seagrasses into the anthropocene.
Continue reading ‘Impact of ocean carbonation on long-term regulation of light harvesting in eelgrass Zostera marina’Archive Page 242
Impact of ocean carbonation on long-term regulation of light harvesting in eelgrass Zostera marina
Published 7 June 2021 Science ClosedTags: biological response, laboratory, morphology, otherprocess, phanerogams, photosynthesis
Analysis of global ocean carbonate chemistry and water mass age information confirms the substantial in situ dissolution of calcium carbonate particles in the upper water column.
Rising atmospheric carbon dioxide (CO2) concentrations from burning of fossil fuels and other anthropogenic sources over the past two and a half centuries have led to an oceanic uptake of about 623 PgCO2 (ref. 1) from the atmosphere, causing ocean acidification worldwide. Marine biogenic carbonate minerals produced in the euphotic zone, the layer closest to the ocean surface, ultimately neutralize the excess CO2, leading to the dissolution of carbonate minerals in the water column or within the sediments. As the influx of anthropogenic CO2 progressively acidifies the oceans, the extent of dissolution will increase within the ocean interior. In previous studies, it had overwhelmingly been thought that calcium carbonate in the open ocean primarily dissolves at the ocean bottom. Writing in Nature Geoscience, Sulpis et al.2, however, find that as much as 47% of the calcium carbonate exported from the ocean surface dissolves in the water column before reaching the seafloor. This in situ dissolution of calcium carbonate particles has a positive effect on absorbing atmospheric CO2.
Calcium carbonate minerals are produced from marine plankton (Fig. 1). Upon the death of these organisms, mineral particles fall rapidly through the water column and a portion is likely to be dissolved while sinking. A parcel of water in the ocean interior today was near the surface at sometime in the past. As the calcium carbonate particles fall through the water column and dissolve, the alkalinity of the seawater in the water column would begin to increase. Therefore, the dissolution rate of calcium carbonate minerals for a certain depth can be estimated using both the changes in alkalinity and the age of the water mass since it was last at the surface.
Continue reading ‘Dissolution resolution’Investigating the impacts of ocean acidification using natural analogues
Published 7 June 2021 Projects , Web sites and blogs ClosedResearchers in the Marine Climate Change Unit at the Okinawa Institute of Science and Technology Graduate University (OIST), alongside those from the University of Tsukuba, the University of Ryukyus, the University of Palermo in Italy, and the French Institute for Research and Development (IRD) in New Caledonia, have been awarded core-to-core funding by the Japan Society for the Promotion of Science to form the International CO2 & Natural Analogues Network (ICONA).
This network aims to create resources on using natural analogues to understand how ocean acidification will impact marine ecosystems. The funding goes from 2021 to 2026.
Prof. Timothy Ravasi, Principle Investigator in the Marine Climate Change Unit, explained how natural analogues mimic future environment. “These are volcanoes, tidal lagoons, or underwater vents that result in higher than average CO2 levels being present in the surrounding ocean. We can use these environments to investigate what the marine ecosystems might look like in the future given the projections for ocean acidification.”
Continue reading ‘Investigating the impacts of ocean acidification using natural analogues’The CO2 system dynamics in the vicinity of the vistula river mouth (the southern Baltic Sea): a baseline investigation
Published 4 June 2021 Science ClosedTags: Baltic, chemistry, field
Highlights
- The CO2 system in the Vistula River plume was investigated for the first time.
- Vistula River as an important TA source to the Baltic Sea.
- OM production and remineralization affect the CO2 system in the Vistula River plume.
- The variability of pH and Ω in the Vistula River plume were significant.
- Vistula River is a source of PIC to the Gdańsk Bay.
Abstract
The CO2 system dynamics in coastal areas strongly controlled by river outflow is largely understudied. In this study, the influence of a large, continental, carbonate-rich river on the carbonate system was seasonally examined in the vicinity of the Vistula River Mouth. Three parameters describing the CO2 system were investigated: the partial pressure of carbon dioxide (pCO2), total alkalinity (TA), and pH, together with salinity, temperature, oxygen concentration, calcium cation (Ca2+), particulate inorganic carbon (PIC), and inorganic carbon (IC) in sediments. TA varied from 1700 μmol kg−1 in the brackish water of the Gdańsk Bay to 3475 μmol kg−1 in the Vistula River plume, highlighting the difference between the two end-members. Highest pCO2 was observed in October (855 μatm) and lowest in May (148 μatm). Oxygen concentration was negatively correlated to pCO2 in all seasons, suggesting that both were inversely controlled by the net ecosystem production (NEP). The pH seasonal variation was significant with a range of 0.72 unit. The calcium carbonate saturation (Ω) varied from 0.8 to 8.5 for calcite and from 0.5 to 8.5 for aragonite, both displaying Ω < 1 in February 2018.
This study shows the importance of ecosystem metabolism and TA end-member variability (3138–3631 μmol kg−1), for controlling pH in the vicinity of the Vistula River Mouth. In addition, we present data on PIC, supporting possible deposition of inorganic forms of carbon to the sediments near the Vistula River Mouth.
Continue reading ‘The CO2 system dynamics in the vicinity of the vistula river mouth (the southern Baltic Sea): a baseline investigation’Online-coupling of widely-ranged timescales to model coral reef development
Published 4 June 2021 Science ClosedTags: biological response, calcification, corals, individualmodeling, light, methods, modeling, morphology, mortality, multiple factors, photosynthesis, physiology, policy, temperature
Highlights
- A biophysical model framework for coral reef evolution is developed.
- The model can be used to predict the coral response to the environment via process-based relations.
- The model bridges the gap in timescales of processes from seconds to millennia.
- Model predictions are within the accuracy of climate projections.
- The model is an efficient tool for forecasting coral reef development to inform policy makers.
Abstract
The increasing pressure on Earth’s ecosystems due to climate change is becoming more and more evident and the impacts of climate change are especially visible on coral reefs. Understanding how climate change interacts with the physical environment of reefs to impact coral growth and reef development is critically important to predicting the persistence of reefs into the future. In this study, a biophysical model was developed including four environmental factors in a feedback loop with the coral’s biology: (1) light; (2) hydrodynamics; (3) temperature; and (4) pH. The submodels are online coupled, i.e. regularly exchanging information and feedbacks while the model runs. This ensures computational efficiency despite the widely-ranged timescales. The composed biophysical model provides a significant step forward in understanding the processes that modulate the evolution of coral reefs, as it is the first construction of a model in which the hydrodynamics are included in the feedback loop.
Continue reading ‘Online-coupling of widely-ranged timescales to model coral reef development’Meet 5 NOAA buoys that help scientists understand our weather, climate and ocean health
Published 4 June 2021 Web sites and blogs ClosedKeeping track of ocean health is critical for understanding climate change, weather patterns, and the health of important fisheries. But how do NOAA and partner scientists gather data on such a vast environment?
One big way is with buoys, ocean observing platforms that help scientists monitor the global ocean — including in remote, hard-to-reach areas. Some of these buoys float along the ocean surface, gathering data as they drift with currents (sometimes even into the paths of hurricanes!). Some, meanwhile, are moored to the ocean floor, collecting data in the same region and helping scientists observe changes over several years or decades. In honor of Ocean Month, we’re highlighting five buoys that help NOAA scientists monitor and understand the ocean (and the Great Lakes, too!).
…
Continue reading ‘Meet 5 NOAA buoys that help scientists understand our weather, climate and ocean health’Fish adapt to ocean acidification by modifying gene expression
Published 4 June 2021 Web sites and blogs Closed
(Photo credit: Sean D. Connell)
Human-driven global change is challenging the scientific community to understand how marine species might adapt to predicted environmental conditions in the near-future (e.g. hypoxia, ocean warming, and ocean acidification). The effects of the uptake of anthropogenic atmospheric CO2 by oceans affects (i.e. ocean acidification) propagate across the biological hierarchy, from changes in the building blocks of life at nano-scales to organism, physiology and behaviour through ecosystem processes and their properties.
To survive in a reduced pH environment, marine organisms have to adjust their physiology which, at the molecular level, is achieved by modifying the expression of genes. The study of such changes in gene expression can aid in revealing the adaptive mechanisms of life under predicted future ocean acidification conditions.
Making use of natural laboratories
There are a few places on this planet where volcanic activity has CO2 bubbling from the seafloor creating conditions that are similar to those predicted to occur across the oceans in the near-future. Such natural laboratories can then help us to understand what will happen to marine organisms in the future under an ocean acidification scenario. Therefore, researchers from Research Division for Ecology & Biodiversity of the University of Hong Kong (HKU) and Swire Institute of Marine Science, jointly with researchers from the University of Adelaide, travelled to a remote volcanic island of New Zealand called White Island. They collected samples from CO2 seeps and nearby locations, and analysed molecular data from a fish species (the Common triplefin) with ecological evidence of being successfully adapted to acidified environments at CO2 volcanic vents. The findings were published in a peer-reviewed open access journal Evolutionary Applications.
Continue reading ‘Fish adapt to ocean acidification by modifying gene expression’ROCHESTER FORUM
Presented by the
University of Rochester Lifelong Learning Advisory Council
Join us online for an afternoon of enlightening presentations and intellectual enrichment. You can choose to attend either presentation or both.
Participants are not required to join all presentations.
Date: Thursday, June 10 2021
Time: 1:10 – 2 p.m. (ET)
Location: Virtual Programs
Title: Ocean Acidification: The Good, the Bad, and the Ugly
featuring John Kessler, PhD
moderated by Katherine Gregory
The oceans are a significant absorber of greenhouse gases released due to human activities as well as the heat retained in the Earth system from their increased concentrations. From one point of view, this is good since it helps to mitigate the direct impacts of our modern global climate change. However, this absorption is not without its consequences, some of which include ocean acidification, the ocean’s ability to further remove atmospheric greenhouse gases, and additional ocean acidification feedback mechanisms. This talk will explore these topics presenting and discussing modern data on ocean acidification and greenhouse gas dynamics, and the impact on our society.
Gaining a clearer understanding of ocean acidification in the Northeast
Published 3 June 2021 Press releases ClosedChallenging conditions for familiar species like lobsters and scallops loom by mid-century
Familiar organisms like lobsters could be affected by changing ocean conditions in the Northeast in the coming decades (Adobe Stock).
By mid-century, the Northeast is expected to experience significant changes in climate, on land and in the region’s waters. Leaders from across New England and the Canadian Maritime Provinces teamed up with experts to compile a report containing the most complete and up-to-date information on the Gulf of Maine, that is also filled with actionable solutions to increase resiliency in the coming decades – all with hopes of inspiring quick action. Details can be found in he Gulf of Maine 2050 Climate Outlook and Action report.
UConn Assistant Professor in the Department of Marine Sciences Samantha Siedlecki is a co-author on the report, which presents a synthesis of research relevant to the region, including sea level rise, temperature change, and Siedlecki’s focus — ocean acidification. The paper detailing Ocean Acidification projections featured in the report was published on May 12th in Elementa.
Continue reading ‘Gaining a clearer understanding of ocean acidification in the Northeast’Projecting ocean acidification impacts for the Gulf of Maine to 2050: new tools and expectations
Published 3 June 2021 Science ClosedTags: biogeochemistry, biological response, chemistry, crustaceans, fish, fisheries, mollusks, North Atlantic, review, socio-economy
Ocean acidification (OA) is increasing predictably in the global ocean as rising levels of atmospheric carbon dioxide lead to higher oceanic concentrations of inorganic carbon. The Gulf of Maine (GOM) is a seasonally varying region of confluence for many processes that further affect the carbonate system including freshwater influences and high productivity, particularly near the coast where local processes impart a strong influence. Two main regions within the GOM currently experience carbonate conditions that are suboptimal for many organisms—the nearshore and subsurface deep shelf. OA trends over the past 15 years have been masked in the GOM by recent warming and changes to the regional circulation that locally supply more Gulf Stream waters. The region is home to many commercially important shellfish that are vulnerable to OA conditions, as well as to the human populations whose dependence on shellfish species in the fishery has continued to increase over the past decade. Through a review of the sensitivity of the regional marine ecosystem inhabitants, we identified a critical threshold of 1.5 for the aragonite saturation state (Ωa). A combination of regional high-resolution simulations that include coastal processes were used to project OA conditions for the GOM into 2050. By 2050, the Ωa declines everywhere in the GOM with most pronounced impacts near the coast, in subsurface waters, and associated with freshening. Under the RCP 8.5 projected climate scenario, the entire GOM will experience conditions below the critical Ωa threshold of 1.5 for most of the year by 2050. Despite these declines, the projected warming in the GOM imparts a partial compensatory effect to Ωa by elevating saturation states considerably above what would result from acidification alone and preserving some important fisheries locations, including much of Georges Bank, above the critical threshold.
Continue reading ‘Projecting ocean acidification impacts for the Gulf of Maine to 2050: new tools and expectations’Patterns of element incorporation in calcium carbonate biominerals recapitulate phylogeny for a diverse range of marine calcifiers
Published 3 June 2021 Science ClosedTags: algae, annelids, biogeochemistry, biological response, calcification, cnidaria, crustaceans, echinoderms, growth, individualmodeling, laboratory, mollusks, paleo, performance, photosynthesis, physiology, reproduction
Elemental ratios in biogenic marine calcium carbonates are widely used in geobiology, environmental science, and paleoenvironmental reconstructions. It is generally accepted that the elemental abundance of biogenic marine carbonates reflects a combination of the abundance of that ion in seawater, the physical properties of seawater, the mineralogy of the biomineral, and the pathways and mechanisms of biomineralization. Here we report measurements of a suite of nine elemental ratios (Li/Ca, B/Ca, Na/Ca, Mg/Ca, Zn/Ca, Sr/Ca, Cd/Ca, Ba/Ca, and U/Ca) in 18 species of benthic marine invertebrates spanning a range of biogenic carbonate polymorph mineralogies (low-Mg calcite, high-Mg calcite, aragonite, mixed mineralogy) and of phyla (including Mollusca, Echinodermata, Arthropoda, Annelida, Cnidaria, Chlorophyta, and Rhodophyta) cultured at a single temperature (25°C) and a range of pCO2 treatments (ca. 409, 606, 903, and 2856 ppm). This dataset was used to explore various controls over elemental partitioning in biogenic marine carbonates, including species-level and biomineralization-pathway-level controls, the influence of internal pH regulation compared to external pH changes, and biocalcification responses to changes in seawater carbonate chemistry. The dataset also enables exploration of broad scale phylogenetic patterns of elemental partitioning across calcifying species, exhibiting high phylogenetic signals estimated from both uni- and multivariate analyses of the elemental ratio data (univariate: λ = 0–0.889; multivariate: λ = 0.895–0.99). Comparing partial R2 values returned from non-phylogenetic and phylogenetic regression analyses echo the importance of and show that phylogeny explains the elemental ratio data 1.4–59 times better than mineralogy in five out of nine of the elements analyzed. Therefore, the strong associations between biomineral elemental chemistry and species relatedness suggests mechanistic controls over element incorporation rooted in the evolution of biomineralization mechanisms.
Continue reading ‘Patterns of element incorporation in calcium carbonate biominerals recapitulate phylogeny for a diverse range of marine calcifiers’Ocean Acidification Community of Practice: quarterly newsletter – June 2021
Published 3 June 2021 Newsletters and reports ClosedOur newest Quarterly Newsletter (June, 2021) has arrived and is full of exciting updates, including a call for collaborators on our Letter of Intent for the Climate Action and Awareness Fund grant proposals, snapshots from our blog, and our new resources (including a new Webinars page with our past webinar recordings)!
OA CoP June 2021 Newsletter.pdf
Our oceans are becoming acidic at an unprecedented rate, and research into the effects of global warming on oceans indicate that this process is happening faster today than at any time in the past 300 million years.
In This Article:
- What Is Ocean Acidification?
- What Is The Cause of Ocean Acidification?
- How Acidic Is The Ocean Today?
- The Chemistry Behind Ocean Acidity
- The Ocean’s Ability to Absorb CO2 is Likely to Diminish
- The Effect of Ocean Acidification on Marine Life
- How Does Ocean Acidification Impact Humans?
- How Can We Stop Ocean Acidification?
- References
…
Continue reading ‘Ocean acidification from CO2 overdose’New edition of the “OA-ICC Highlights”, January-April 2021
Published 2 June 2021 Newsletters and reports Closed
The new edition of the “OA-ICC Highlights”, our newsletter, summarizes the project’s main activities and achievements over the period January-April 2021. This newsletter highlights a virtual OA conference with OA-Africa Network to celebrate the Day of Ocean Acidification Action, OA-ICC assesses global capacity building efforts and joined GOA-ON for the planning for the UN Decade of Ocean Science for Sustainable Development program (2021-2030), a dedicate session on Monaco Ocean Week and the welcoming of a new staff. Previous editions can be viewed here.
Coral bleaching response is unaltered following acclimatization to reefs with distinct environmental conditions
Published 2 June 2021 Science ClosedTags: biological response, chemistry, corals, field, morphology, mortality, North Pacific, physiology
Significance
Ocean warming has caused catastrophic losses of corals on reefs worldwide and is intensifying faster than the adaptive rate of most coral populations that remain. Human interventions, such as propagation of heat-resistant corals, may help maintain reef function and delay further devastation of these valuable ecosystems as society confronts the climate crisis. However, exposing adult corals to a complex suite of new environmental conditions could lead to tradeoffs that alter their heat stress responses, and empirical data are needed to test the utility of this approach. Here, we show that corals transplanted to novel reef conditions did not exhibit changes in their heat stress response or negative fitness tradeoffs, supporting the inclusion of this approach in our management arsenal.
Abstract
Urgent action is needed to prevent the demise of coral reefs as the climate crisis leads to an increasingly warmer and more acidic ocean. Propagating climate change–resistant corals to restore degraded reefs is one promising strategy; however, empirical evidence is needed to determine whether stress resistance is affected by transplantation beyond a coral’s native reef. Here, we assessed the performance of bleaching-resistant individuals of two coral species following reciprocal transplantation between reefs with distinct pH, salinity, dissolved oxygen, sedimentation, and flow dynamics to determine whether heat stress response is altered following coral exposure to novel physicochemical conditions in situ. Critically, transplantation had no influence on coral heat stress responses, indicating that this trait was relatively fixed. In contrast, growth was highly plastic, and native performance was not predictive of performance in the novel environment. Coral metabolic rates and overall fitness were higher at the reef with higher flow, salinity, sedimentation, and diel fluctuations of pH and dissolved oxygen, and did not differ between native and cross-transplanted corals, indicating acclimatization via plasticity within just 3 mo. Conversely, cross-transplants at the second reef had higher fitness than native corals, thus increasing the fitness potential of the recipient population. This experiment was conducted during a nonbleaching year, so the potential benefits to recipient population fitness are likely enhanced during bleaching years. In summary, this study demonstrates that outplanting bleaching-resistant corals is a promising tool for elevating the resistance of coral populations to ocean warming.
Continue reading ‘Coral bleaching response is unaltered following acclimatization to reefs with distinct environmental conditions’Energetic context determines the effects of multiple upwelling-associated stressors on sea urchin performance
Published 2 June 2021 Science ClosedTags: adaptation, algae, biological response, BRcommunity, community composition, echinoderms, laboratory, mesocosms, morphology, mortality, multiple factors, otherprocess, oxygen, performance, temperature
Globally, kelp forests are threatened by multiple stressors, including increasing grazing by sea urchins. With coastal upwelling predicted to increase in intensity and duration in the future, understanding whether kelp forest and urchin barren urchins are differentially affected by upwelling-related stressors will give insight into how future conditions may affect the transition between kelp forests and barrens. We assessed how current and future-predicted changes in the duration and magnitude of upwelling-associated stressors (low pH, dissolved oxygen, and temperature) affected the performance of purple sea urchins (Strongylocentrotus purpuratus) sourced from rapidly-declining bull kelp (Nereocystis leutkeana) forests and nearby barrens and maintained on habitat-specific diets. Kelp forest urchins were of superior condition to barrens urchins, with ~ 6–9 times more gonad per body mass. Grazing and condition in kelp forest urchins were more negatively affected by distant-future and extreme upwelling conditions, whereas grazing and survival in urchins from barrens were sensitive to both current-day and all future-predicted upwelling, and to increases in acidity, hypoxia, and temperature regardless of upwelling. We conclude that urchin barren urchins are more susceptible to increases in the magnitude and duration of upwelling-related stressors than kelp forest urchins. These findings have important implications for urchin population dynamics and their interaction with kelp.
Continue reading ‘Energetic context determines the effects of multiple upwelling-associated stressors on sea urchin performance’
Microscopic shells have been used by geologists at the University of St Andrews to chart the earth’s climate over millions of years.
They have concluded that it is three million years since current carbon dioxide (CO2) levels were last experienced on earth.
The shells were extracted from mud samples taken from the deep ocean bed.
Experts then related the make-up of the shells with the acidity of the sea water and then atmospheric CO2 levels.
…
Continue reading ‘Ancient shells from seabed show rising CO2 levels’Acid–base balance in the hæmolymph of European abalone (Haliotis tuberculata) exposed to CO2-induced ocean acidification
Published 1 June 2021 Science ClosedTags: biological response, laboratory, mollusks, performance, physiology, socio-economy
Highlights
- The effects of ocean acidification (OA) on extra-cellular acid–base parameters are reported in the European abalone H. tuberculata, a commercially and ecologically important gastropod.
- Adult abalone were exposed for 15 days to three different pH levels (7.9, 7.7, 7.4) representing current and predicted near-future conditions.
- Abalones are able to buffer a moderate acidification of seawater (−0.2 pH units).
- Haemolymph pH was significantly decreased after 5 days of exposure to pH 7.4 (−0.5 pH units) indicating that abalone do not compensate for higher decreases of in seawater pH.
- OA would impact both the ecology and aquaculture of H. tuberculata in the near future.
Abstract
Ocean acidification (OA) and the associated changes in seawater carbonate chemistry pose a threat to calcifying organisms. This is particularly serious for shelled molluscs, in which shell growth and microstructure has been shown to be highly sensitive to OA. To improve our understanding of the responses of abalone to OA, this study investigated the effects of CO2-induced ocean acidification on extra-cellular acid–base parameters in the European abalone Haliotis tuberculata. Three-year-old adult abalone were exposed for 15 days to three different pH levels (7.9, 7.7, 7.4) representing current and predicted near-future conditions. Hæmolymph pH and total alkalinity were measured at different time points during exposure and used to calculate the carbonate parameters of the extracellular fluid. Total protein content was also measured to determine whether seawater acidification influences the composition and buffer capacity of hæmolymph. Extracellular pH was maintained at seawater pH 7.7 indicating that abalones are able to buffer moderate acidification (−0.2 pH units). This was not due to an accumulation of HCO3− ions but rather to a high hæmolymph protein concentration. By contrast, hæmolymph pH was significantly decreased after 5 days of exposure to pH 7.4, indicating that abalone do not compensate for higher decreases in seawater pH. Total alkalinity and dissolved inorganic carbon were also significantly decreased after 15 days of low pH exposure. It is concluded that changes in the acid–base balance of the hæmolymph might be involved in deleterious effects recorded in adult H. tuberculata facing severe OA stress. This would impact both the ecology and aquaculture of this commercially important species.
Continue reading ‘Acid–base balance in the hæmolymph of European abalone (Haliotis tuberculata) exposed to CO2-induced ocean acidification’Reviews and syntheses: spatial and temporal patterns in metabolic fluxes inform potential for seagrass to locally mitigate ocean acidification
Published 1 June 2021 Science ClosedTags: biological response, chemistry, community composition, individualmodeling, mitigation, modeling, phanerogams, physiology, primary production, respiration, review
As global change continues to progress, there is a growing interest in assessing any local levers that could be used to manage the social and ecological impacts of rising CO2 concentrations. While habitat conservation and restoration have been widely recognized for their role in carbon storage and sequestration at a global scale, the potential for managers to use vegetated habitats to mitigate CO2 concentrations at local scales in marine ecosystems facing the accelerating threat of ocean acidification (OA) has only recently garnered attention. Early studies have shown that submerged aquatic vegetation, such as seagrass beds, can locally draw down CO2 and raise seawater pH in the water column through photosynthesis, but empirical studies of local OA mitigation are still quite limited. Here, we leverage the extensive body of literature on seagrass community metabolism to highlight key considerations for local OA management through seagrass conservation or restoration. In particular, we synthesize the results from 62 studies reporting in situ rates of seagrass gross primary productivity, respiration, and/or net community productivity to highlight spatial and temporal variability in carbon fluxes. We illustrate that daytime net community production is positive overall, and similar across seasons and geographies. Full-day net community production rates, which illustrate the potential cumulative effect of seagrass beds on seawater biogeochemistry integrated over day and night, were also positive overall, but were higher in summer months in both tropical and temperate ecosystems. Although our analyses suggest seagrass meadows are generally autotrophic, the modeled effects on seawater pH are relatively small in magnitude. In addition, we illustrate that periods when full-day net community production is highest could be associated with lower nighttime pH and increased diurnal variability in seawater pCO2/pH. Finally, we highlight important areas for future research to inform the next steps for assessing the utility of this approach for management.
Continue reading ‘Reviews and syntheses: spatial and temporal patterns in metabolic fluxes inform potential for seagrass to locally mitigate ocean acidification’Coral reefs in the Anthropocene ocean: novel insights from skeletal proxies of climate change, impacts, and resilience
Published 1 June 2021 Science ClosedTags: adaptation, biological response, corals, field, growth, morphology, North Pacific, South Pacific
Anthropogenic emissions of greenhouse gases are driving rapid changes in ocean conditions. Shallow-water coral reefs are experiencing the brunt of these changes, including intensifying marine heatwaves (MHWs) and rapid ocean acidification (OA). Consequently, coral reefs are in broad-scale decline, threatening the livelihoods of hundreds of millions of people. Ensuring survival of coral reefs in the 21st century will thus require a new management approach that incorporates robust understanding of reef-scale climate change, the mechanisms by which these changes impact corals, and their potential for adaptation. In this thesis, I extract information from within coral skeletons to 1) Quantify the climate changes occurring on coral reefs and the effects on coral growth, 2) Identify differences in the sensitivity of coral reefs to these changes, and 3) Evaluate the adaptation potential of the keystone reef-building coral, Porites. First, I develop a mechanistic Porites growth model and reveal the physicochemical link between OA and skeletal formation. Ishow that the thickening (densification) of coralskeletal framework is most vulnerable to OA and that, under 21st century climate model projections, OA will reduce Porites skeletal density globally, with greatest impact in the Coral Triangle. Second, I develop an improved metric of thermal stress, and use a skeletal bleaching proxy to quantify coral responses to intensifying heatwaves in the central equatorial Pacific (CEP) since 1982. My work reveals a long history of bleaching in the CEP, and reef-specific differences in thermal tolerance linked to past heatwave exposure implying that, over time, reef communities have adapted to tolerate their unique thermal regimes. Third, I refine the Sr-U paleo-thermometer to enable monthly-resolved sea surface temperatures (SST) generation using laser ablation ICPMS. I show that laser Sr-U accurately captures CEP SST, including the frequency and amplitude of MHWs. Finally, I apply laser Sr-U to reconstruct the past 100 years of SST at Jarvis Island in the CEP, and evaluate my proxy record of bleaching severity in this context. I determine that Porites coral populations on Jarvis Island have not yet adapted to the pace of anthropogenic climate change.
Continue reading ‘Coral reefs in the Anthropocene ocean: novel insights from skeletal proxies of climate change, impacts, and resilience’
