Macrophytes vary in their ability to utilize carbon in the form of HCO3− and/or CO2 for photosynthesis. Some functional groups that solely use CO2 for photosynthesis could receive competitive advantages from the predicted increase in CO2 compared to groups with efficient carbon acquisition strategies of HCO3−. The aim of this study was to identify carbon use strategies in the common macrophytes (macroalgae, charophytes, seagrass, and other angiosperms) that represent a broad range of functional traits to CO2 concentrations in the northeastern Baltic Sea. Mechanistic assessment of the carbon physiology of macrophytes was used to predict productivity and competitive interactions between different functional groups under future climate. Carbon use strategies in macrophytes were determined by analysing the carbon isotopes (δ13C), pH drift experiments, and photosynthesis versus dissolved inorganic carbon. In addition, habitat mapping data was used to interpret the potential implications of the elevated CO2 to this coastal ecosystem. The results suggested that the primary productivity of macrophytes is often limited by carbon availability, and the increasing CO2 concentrations in the brackish Baltic Sea are expected to enhance photosynthetic production. While all species tested showed evidence of carbon concentrating mechanisms (CCMs), differential levels of CCM activity indicate varying levels of competitive fitness in a future high-CO2 environment. Overall, macrophytes which inhabit the shallowest and deepest parts of the vegetated zone are expected to experience physiological benefits under future CO2 conditions, while intermediate communities dominated by the perennial brown alga Fucus vesiculosus may experience loss of fitness. These fitness differences have implications for competitive interaction and species range under future climate.
Continue reading ‘Species-specific responses of macrophyte production to the increasing CO2 environment with potential ecosystem implications involved in the Baltic Sea’Posts Tagged 'primary production'
Species-specific responses of macrophyte production to the increasing CO2 environment with potential ecosystem implications involved in the Baltic Sea
Published 21 August 2023 Science ClosedTags: algae, Baltic, biological response, laboratory, photosynthesis, primary production
Seasonal production dynamics of high latitude seaweeds in a changing ocean: implications for bottom-up effects on temperate coastal food webs
Published 10 August 2023 Science ClosedTags: algae, biological response, BRcommunity, calcification, chemistry, dissolution, field, growth, laboratory, light, morphology, multiple factors, North Pacific, otherprocess, phanerogams, photosynthesis, physiology, primary production, temperature
As the oceans absorb excess heat and CO2 from the atmosphere, marine primary producers face significant changes to their abiotic environments and their biotic interactions with other species. Understanding the bottom-up consequences of these effects on marine food webs is essential to informing adaptive management plans that can sustain ecosystem and cultural services. In response to this need, this dissertation provides an in-depth consideration of the effects of global change on foundational macroalgal (seaweed) species in a poorly studied, yet highly productive region of our world’s oceans. To explore how seaweeds within seasonally dynamic giant kelp forest ecosystems will respond to ocean warming and acidification, I employ a variety of methods: year-round environmental monitoring using an in situ sensor array, monthly subtidal community surveys, and a series of manipulative experiments. I find that a complementary phenology of macroalgal production currently characterizes these communities, providing complex habitat and a nutritionally diverse energy supply to support higher trophic levels throughout the year. I also find that future ocean warming and acidification will lead to substantial shifts in the phenology, quantity and quality of macroalgal production in these systems. My results suggest that the giant kelp Macrocystis pyrifera may be relatively resilient to the effects of global change in future winter and summer seasons at high latitudes. In contrast, the calcifying coralline algae Bossiella orbigniana and Crusticorallina spp. and the understory kelps Hedophyllum nigripes and Neoagarum fimbriatum will experience a suite of negative impacts, especially in future winter conditions. The resulting indirect effects on macroalgal-supported coastal food webs will be profound, with projected reductions in habitat and seasonal food supply on rocky reefs. Coming at a time of heightened interest in seaweed production potential at high latitudes, this dissertation provides a comprehensive evaluation of the future of these foundational organisms in a changing environment.
Continue reading ‘Seasonal production dynamics of high latitude seaweeds in a changing ocean: implications for bottom-up effects on temperate coastal food webs’Effects of climate change and eutrophication on photosynthesis and carbon-concentrating mechanisms: surprising diversity among reef algae
Published 19 July 2023 Science ClosedTags: algae, biological response, chemistry, growth, laboratory, multiple factors, North Pacific, nutrients, photosynthesis, physiology, primary production
Increased anthropogenic CO2 emission since the start of the Industrial Revolution has brought a changing climate and various threats to coastal ecosystems including ocean warming, ocean acidification (OA), and sea level rise. Coral reef ecosystems are especially vulnerable to the climate change, because ocean warming and acidification decrease calcification and increase bleaching in coral. In addition to these impacts of climate change, coastal ecosystems are already experiencing local anthropogenic impacts such as chronic eutrophication and continuing arrival of new invasive species. In Hawai‘i, large-scale blooms of both native and invasive macroalgae are often observed in the region with coastal eutrophication by land-based anthropogenic nutrient input. Predicting the effects of OA (increased CO2 concentration in the ocean) on algae is not straightforward because many algae are already equipped with carbon-concentrating mechanisms (CCMs) with which algae can increase their internal CO2 concentration for photosynthesis. Further, nutrient availability especially that of the macronutrient, nitrogen (N) could alter the operation of algal CCMs because CCMs involve specific, large proteins such as ribulose-1,5-biphosphate carboxylase-oxygenase (RUBISCO) and carbonic anhydrases (CA). This study experimentally investigated how OA and eutrophication, independently and synergistically, affect photosynthesis and CCMs in common Hawaiian reef algae. Algae can quickly change their maximum photosynthetic rates and CCMs when grown under elevated CO2 and N. Further, we found a surprising diversity among reef algae in how they react to elevated CO2 and N with their CCMs. The results of this study suggest that many Hawaiian algae will thrive under future climate change conditions, and OA and eutrophication will likely work in their favor, accelerating the phase shift from coral-dominated to macroalgal-dominated reefs in unpredictably faster paces and with players that are not easily predicted.
Continue reading ‘Effects of climate change and eutrophication on photosynthesis and carbon-concentrating mechanisms: surprising diversity among reef algae’Physiological response of an Antarctic cryptophyte to increasing temperature, CO2, and irradiance
Published 12 July 2023 Science ClosedTags: abundance, Antarctic, biogeochemistry, biological response, growth, laboratory, light, multiple factors, otherprocess, photosynthesis, phytoplankton, primary production, temperature
The Southern Ocean, a globally important CO2 sink, is one of the most susceptible regions in the world to climate change. Phytoplankton of the coastal shelf waters around the Western Antarctic Peninsula have been experiencing rapid warming over the past decades and current ongoing climatic changes will expose them to ocean acidification and high light intensities due to increasing stratification. We conducted a multiple-stressor experiment to evaluate the response of the still poorly studied key Antarctic cryptophyte species Geminigera cryophila to warming in combination with ocean acidification and high irradiance. Based on the thermal growth response of G. cryophila, we grew the cryptophyte at suboptimal (2°C) and optimal (4°C) temperatures in combination with two light intensities (medium light: 100 μmol photons m−2 s−1 and high light [HL]: 500 μmol photons m−2 s−1) under ambient (400 μatm pCO2) and high pCO2 (1000 μatm pCO2) conditions. Our results reveal that G. cryophila was not susceptible to high pCO2, but was strongly affected by HL at 2°C, as both growth and carbon fixation were significantly reduced. In comparison, warming up to 4°C stimulated the growth of the cryptophyte and even alleviated the previously observed negative effects of HL at 2°C. When grown, however, at temperatures above 4°C, the cryptophyte already reached its maximal thermal limit at 8°C, pointing out its vulnerability toward even higher temperatures. Hence, our results clearly indicate that warming and high light and not pCO2 control the growth of G. cryophila.
Continue reading ‘Physiological response of an Antarctic cryptophyte to increasing temperature, CO2, and irradiance’Coccolithophores and diatoms resilient to ocean alkalinity enhancement: a glimpse of hope?
Published 20 June 2023 Science ClosedTags: biogeochemistry, biological response, growth, laboratory, mitigation, North Pacific, physiology, phytoplankton, primary production
It is increasingly apparent that adequately mitigating anthropogenic climate interference will require ocean carbon dioxide removal (CDR) strategies. Ocean alkalinity enhancement (OAE) is an abiotic ocean CDR approach that aims to increase the ocean’s CO2 uptake capacity through the dispersal of pulverized mineral or dissolved alkali into the surface ocean. However, OAE’s effect on marine biota is largely unexplored. Here, we investigate the impacts of moderate (~700 μmol kg−1) and high (~2700 μmol kg−1) limestone-inspired alkalinity additions on two biogeochemically and ecologically important phytoplankton functional group representatives: Emiliania huxleyi (calcium carbonate producer) and Chaetoceros sp. (silica producer). The growth rate and elemental ratios of both taxa showed a neutral response to limestone-inspired alkalinization. While our results are encouraging, we also observed abiotic mineral precipitation, which removed nutrients and alkalinity from solution. Our findings offer an evaluation of biogeochemical and physiological responses to OAE and provide evidence supporting the need for continued research into how OAE strategies affect marine ecosystems.
Continue reading ‘Coccolithophores and diatoms resilient to ocean alkalinity enhancement: a glimpse of hope?’The impacts of ocean acidification, warming and their interactive effects on coral prokaryotic symbionts
Published 14 June 2023 Science ClosedTags: biological response, BRcommunity, community composition, corals, laboratory, molecular biology, multiple factors, North Pacific, otherprocess, physiology, primary production, prokaryotes, temperature
Reef-building corals, the foundation of tropical coral reefs, are vulnerable to climate change e.g. ocean acidification and elevated seawater temperature. Coral microbiome plays a key role in host acclimatization and maintenance of the coral holobiont’s homeostasis under different environmental conditions, however, the response patterns of coral prokaryotic symbionts to ocean acidification and/or warming are rarely known at the metatranscriptional level, particularly the knowledge of interactive and persistent effects is limited. Using branching Acropora valida and massive Galaxea fascicularis as models in a lab system simulating extreme ocean acidification (pH 7.7) and/or warming (32 °C) in the future, we investigated the changes of in situ active prokaryotic symbionts community and gene expression of corals under/after (6/9 d) acidification (A), warming (H) and acidification–warming (AH) by metatranscriptome analysis with pH8.1, 26 °C as the control.
Continue reading ‘The impacts of ocean acidification, warming and their interactive effects on coral prokaryotic symbionts’Marine macroinvertebrate ecosystem services under changing conditions of seagrasses and mangroves
Published 5 June 2023 Science ClosedTags: abundance, annelids, biological response, BRcommunity, chemistry, cnidaria, community composition, crustaceans, echinoderms, Indian, mollusks, otherprocess, phanerogams, phytoplankton, primary production, review, socio-economy
Highlights
- Overfishing and climate change show potential effects on MMI ES.
- MMI regulating ES can be quantified using species richness and functional traits.
- Digital platforms are valuable tools to retrieve data but have limitations.
- Baseline data and information on environmental changes and MMI ES is provided.
Abstract
This study aimed to investigate the impact of changing environmental conditions on MMI ES in seagrasses and mangroves. We used data from satellite and biodiversity platforms combined with field data to explore the links between ecosystem pressures (habitat conversion, overexploitation, climate change), conditions (environmental quality, ecosystem attributes), and MMI ES (provisioning, regulation, cultural). Both seagrass and mangrove extents increased significantly since 2016. While sea surface temperature showed no significant annual variation, sea surface partial pressure CO2, height above sea level and pH presented significant changes. Among the environmental quality variables only silicate, PO4 and phytoplankton showed significant annual varying trends. The MMI food provisioning increased significantly, indicating overexploitation that needs urgent attention. MMI regulation and cultural ES did not show significant trends overtime. Our results show that MMI ES are affected by multiple factors and their interactions can be complex and non-linear. We identified key research gaps and suggested future directions for research. We also provided relevant data that can support future ES assessments.
Continue reading ‘Marine macroinvertebrate ecosystem services under changing conditions of seagrasses and mangroves’Ocean acidification enhances primary productivity and nocturnal carbonate dissolution in intertidal rock pools
Published 18 May 2023 Science ClosedTags: algae, biological response, BRcommunity, calcification, chemistry, dissolution, field, North Atlantic, primary production, respiration
Human CO2 emissions are modifying ocean carbonate chemistry, causing ocean acidification, and likely already impacting marine ecosystems. In particular, there is concern that coastal, benthic calcifying organisms will be negatively affected by ocean acidification, a hypothesis largely supported by laboratory studies. The inter-relationships between carbonate chemistry and marine calcifying communities in situ are complex and natural mesocosms such as tidal pools can provide useful community-level insights. In this study, we manipulated the carbonate chemistry of intertidal pools to investigate the influence of future ocean acidification on net community production (NCP) and calcification (NCC) at emersion. Adding CO2 at the start of the tidal emersion to simulate future acidification (+1500 μatm pCO2, target pH: 7.5) modified net production and calcification rates in the pools. By day, pools were fertilized by the increased CO2 (+20 % increase in NCP, from 10 to 12 mmol O2 m−2 hr−1), while there was no measurable impact on NCC. During the night, pools experienced net community dissolution (NCC < 0), even in present-day conditions, when waters were supersaturated with regards to aragonite. Adding CO2 in the pools increased nocturnal dissolution rates by 40 % (from −0.7 to −1.0 mmol CaCO3 m−2 hr−1) with no consistent impact on night community respiration. Our results suggest that ocean acidification is likely to alter temperate intertidal community metabolism on sub-daily timescales, enhancing both diurnal community production and nocturnal calcium carbonate dissolution.
Continue reading ‘Ocean acidification enhances primary productivity and nocturnal carbonate dissolution in intertidal rock pools’Enhalus acoroides efficiently alleviate ocean acidification by shifting modes of inorganic carbon uptake and increasing photosynthesis when pH drops
Published 3 May 2023 Science ClosedTags: algae, biogeochemistry, biological response, laboratory, North Pacific, primary production
Ocean acidification (OA) is causing increasing ecological damage, so it is worthwhile to find efficient and environmentally friendly ways to mitigate OA. The mechanism of inorganic carbon (Ci) absorption and the ability to mitigate OA of the tropical seagrass Enhalus acoroides were investigated in this study. At 2.2 mM Ci concentration, its CO2 fixation efficiency increased to 81.89 t CO2/year/Ha under pH 6.5 from 27.59 t CO2/year/Ha at pH 8.2, and even reached 88.11 t CO2/year/Ha at pH 6.5 with unlimited Ci availability, made possible by three pathways for Ci utilization, which included absorbing CO2 directly, transforming HCO3− into CO2 through extracellular carbonic anhydrase, and absorbing HCO3− directly by anion-exchange protein then transforming it to CO2 through intracellular carbonic anhydrase, as verified by inhibitor addition experiments. The carbon fixation rate increased with decreasing pH, suggesting a greater CO2 absorbing capacity for E. acoroides under acidic conditions, which further demonstrates the possibility of mitigating OA and increasing carbon fixation through conserving and restoring E. acoroides meadows. Due to the strong carbon absorption capacity of E. acoroides, it is very important to strengthen the artificial restoration of E. acoroides seagrass meadows in the environmental management of the coastline.
Continue reading ‘Enhalus acoroides efficiently alleviate ocean acidification by shifting modes of inorganic carbon uptake and increasing photosynthesis when pH drops’Short-term responses of Corallina officinalis (rhodophyta) to global-change drivers in a stressful environment of Patagonia, Argentina
Published 28 April 2023 Science ClosedTags: biological response, corals, laboratory, light, multiple factors, nutrients, physiology, primary production, South Atlantic
Over the last two decades, an increasing interest has arisen in the responses of primary producers to global-change drivers and, more recently, in the need to consider how those various drivers may interact. To understand how Corallina officinalis (hereafter Corallina) can be affected by future changing conditions, we investigated the short-term direct effects of co-occurring increased nutrient loads, solar radiation, and lower pH, assessing how these clustered drivers affected Corallina‘s overall physiological performance in a harsh Patagonian coastal environment. To describe the seasonal trend of the physiological parameters in the field, we sampled subtidal Corallina to determine their net oxygen production (NOP), pigments, and carbonate content (CC). Furthermore, we conducted seasonal 10-days experiments, simulating the conditions predicted for the year 2100 by the IPCC (RCP 8.5) —manipulating pH, nutrients, and irradiance—along with the current conditions. The pigments and carotenoids/chlorophyll-a ratio were, in general, constant in the field over the seasons; but the NOP and CC dropped in spring, when the carotenoids peaked. After the experiment, the highest carotenoid/chlorophyll-a ratio was registered in summer under both the currentand the predictedconditions and in winter under the predictedcondition. This lower physiological status was also reflected in almost all other variables. Thus, Corallina may display an acclimatation strategy to cope with high ultraviolet-radiation levels by adjusting its pigment composition to avoid photoinhibition. An understanding of how Corallina, as a habitat-forming species, will respond to future global-change may provide clues about the extent of effects on the ecosystem functions and services.
Continue reading ‘Short-term responses of Corallina officinalis (rhodophyta) to global-change drivers in a stressful environment of Patagonia, Argentina’Coral adaptive capacity insufficient to halt global transition of coral reefs into net erosion under climate change
Published 18 April 2023 Science ClosedTags: adaptation, biogeochemistry, biological response, BRcommunity, communitymodeling, corals, Indian, modeling, multiple factors, North Atlantic, North Pacific, otherprocess, primary production, regionalmodeling, South Pacific, temperature
Projecting the effects of climate change on net reef calcium carbonate production is critical to understanding the future impacts on ecosystem function, but prior estimates have not included corals’ natural adaptive capacity to such change. Here we estimate how the ability of symbionts to evolve tolerance to heat stress, or for coral hosts to shuffle to favourable symbionts, and their combination, may influence responses to the combined impacts of ocean warming and acidification under three representative concentration pathway (RCP) emissions scenarios (RCP2.6, RCP4.5 and RCP8.5). We show that symbiont evolution and shuffling, both individually and when combined, favours persistent positive net reef calcium carbonate production. However, our projections of future net calcium carbonate production (NCCP) under climate change vary both spatially and by RCP. For example, 19%–35% of modelled coral reefs are still projected to have net positive NCCP by 2050 if symbionts can evolve increased thermal tolerance, depending on the RCP. Without symbiont adaptive capacity, the number of coral reefs with positive NCCP drops to 9%–13% by 2050. Accounting for both symbiont evolution and shuffling, we project median positive NCPP of coral reefs will still occur under low greenhouse emissions (RCP2.6) in the Indian Ocean, and even under moderate emissions (RCP4.5) in the Pacific Ocean. However, adaptive capacity will be insufficient to halt the transition of coral reefs globally into erosion by 2050 under severe emissions scenarios (RCP8.5).
Continue reading ‘Coral adaptive capacity insufficient to halt global transition of coral reefs into net erosion under climate change’Projected effects of climate change on marine ecosystems in Southeast Asian seas
Published 17 April 2023 Science ClosedTags: biological response, BRcommunity, chemistry, corals, modeling, North Pacific, phytoplankton, primary production, regionalmodeling, South Pacific, zooplankton
The seas of Southeast Asia are home to some of the world’s most diverse ecosystems and resources that support the livelihoods of millions of people. Climate change will bring temperature changes, acidification and other environmental change, with uncertain consequences for human and natural systems, but there has been little regional-scale climate modelling of the marine ecosystem. We present initial dynamically downscaled projections using a biogeochemical model suitable for coastal and shelf seas. A coupled physical-biogeochemical model with a resolution of 0.1° (approximately 11 km) was used to create projections of future environmental conditions under moderate (RCP4.5) and high (RCP8.5) greenhouse gas scenarios. Changes for different parts of the region are presented, including four sensitive coastal sites of key importance for biodiversity and sustainable development: UNESCO Biosphere Reserves at Cu Lao Cham-Hoi An in Vietnam, Palawan in the Philippines and Taka Bonerate-Kepulauan Selayar in Indonesia, and coastal waters of Sabah, Malaysia, which include several marine parks. The projections show a sea that is warming by 1.1 to 2.9°C through the 21st century, with dissolved oxygen decreasing by 5 to 13 mmol m-3 and changes in many other environmental variables. The changes reach all parts of the water column and many places are projected to experience conditions well outside the range seen at the start of the century. The resulting damage to coral reefs and altered species distribution would have consequences for biodiversity, the livelihoods of small-scale fishers and the food security of coastal communities. Further work using a range of global models and regional models with different biogeochemical components is needed to provide confidence levels, and we suggest some ways forward. Projections of this type serve as a key tool for communities and policymakers as they plan how they will adapt to the challenge of climate change.
Continue reading ‘Projected effects of climate change on marine ecosystems in Southeast Asian seas’Sponge organic matter recycling: reduced detritus production under extreme environmental conditions
Published 14 April 2023 Science ClosedTags: abundance, biogeochemistry, biological response, BRcommunity, chemistry, field, multiple factors, otherprocess, oxygen, photosynthesis, physiology, phytoplankton, porifera, primary production, prokaryotes, respiration, South Pacific, temperature
Highlights
- Sponge metabolism was measured at the natural laboratory of Bouraké where sponges are naturally exposed to extreme conditions associated with tidal phase.
- The photosymbiotic HMA sponge Rhabdastrella globostellata was able to cope with extreme acidification and deoxygenation seawater.
- Photosynthetic activity of sponge symbionts was negatively affected during extreme environmental conditions.
- The sponge loop pathway was disrupted during low tide, which correlated with extreme acidification, deoxygenation and warming seawater.
Abstract
Sponges are a key component of coral reef ecosystems and play an important role in carbon and nutrient cycles. Many sponges are known to consume dissolved organic carbon and transform this into detritus, which moves through detrital food chains and eventually to higher trophic levels via what is known as the sponge loop. Despite the importance of this loop, little is known about how these cycles will be impacted by future environmental conditions. During two years (2018 and 2020), we measured the organic carbon, nutrient recycling, and photosynthetic activity of the massive HMA, photosymbiotic sponge Rhabdastrella globostellata at the natural laboratory of Bouraké in New Caledonia, where the physical and chemical composition of seawater regularly change according to the tide. We found that while sponges experienced acidification and low dissolved oxygen at low tide in both sampling years, a change in organic carbon recycling whereby sponges stopped producing detritus (i.e., the sponge loop) was only found when sponges also experienced higher temperature in 2020. Our findings provide new insights into how important trophic pathways may be affected by changing ocean conditions.
Continue reading ‘Sponge organic matter recycling: reduced detritus production under extreme environmental conditions’Photoinhibition of the picophytoplankter Synechococcus is exacerbated by ocean acidification
Published 11 April 2023 Science ClosedTags: adaptation, biological response, growth, laboratory, light, multiple factors, otherprocess, photosynthesis, physiology, phytoplankton, primary production
The marine picocyanobacterium Synechococcus accounts for a major fraction of the primary production across the global oceans. However, knowledge of the responses of Synechococcus to changing pCO2 and light levels has been scarcely documented. Hence, we grew Synechococcus sp. CB0101 at two CO2 concentrations (ambient CO2 AC:410 μatm; high CO2 HC:1000 μatm) under various light levels between 25 and 800 μmol photons m−2 s−1 for 10–20 generations and found that the growth of Synechococcus strain CB0101 is strongly influenced by light intensity, peaking at 250 μmol m−2 s−1 and thereafter declined at higher light levels. Synechococcus cells showed a range of acclimation in their photophysiological characteristics, including changes in pigment content, optical absorption cross section, and light harvesting efficiency. Elevated pCO2 inhibited the growth of cells at light intensities close to or greater than saturation, with inhibition being greater under high light. Elevated pCO2 also reduced photosynthetic carbon fixation rates under high light but had smaller effects on the decrease in quantum yield and maximum relative electron transport rates observed under increasing light intensity. At the same time, the elevated pCO2 significantly decreased particulate organic carbon (POC) and particulate organic nitrogen (PON), particularly under low light. Ocean acidification, by increasing the inhibitory effects of high light, may affect the growth and competitiveness of Synechococcus in surface waters in the future scenario.
Continue reading ‘Photoinhibition of the picophytoplankter Synechococcus is exacerbated by ocean acidification’Ocean acidification conditions and marine diatoms
Published 11 April 2023 Science ClosedTags: biological response, BRcommunity, field, morphology, photosynthesis, phytoplankton, primary production, review
Ocean acidification doesn’t just erode calcium carbonate shells. It can also slow the rate of diatoms to build their beautiful, intricate silica cell walls. Thinner walls mean lighter diatoms making the algae less able to transport carbon to the deep ocean. Diatoms are a key group of non-calcifying marine phytoplankton, responsible for ~40% of ocean productivity. Growth, cell size, and silica content are strong determinants of diatom resilience and sinking velocity; therefore, the effect of diatom species on ocean biogeochemistry is a function of its growth strategy, size, and frustule thickness. In natural environments, pH directly affects the diatom’s growth rate and therefore the timing and abundance of species. Consequently, understanding impacts of ocean acidification on diatom community structure is crucial for evaluating the sensitivity of biogeochemical cycles and ecosystem services in the world’s oceans.
Continue reading ‘Ocean acidification conditions and marine diatoms’Microbial ecosystem responses to alkalinity enhancement in the North Atlantic subtropical gyre
Published 29 July 2022 Science ClosedTags: abundance, biological response, laboratory, mitigation, North Atlantic, otherprocess, phytoplankton, primary production
In addition to reducing carbon dioxide (CO2) emissions, actively removing CO2 from the atmosphere is widely considered necessary to keep global warming well below 2°C. Ocean Alkalinity Enhancement (OAE) describes a suite of such CO2 removal processes that all involve enhancing the buffering capacity of seawater. In theory, OAE both stores carbon and offsets ocean acidification. In practice, the response of the marine biogeochemical system to OAE must be demonstrably negligible, or at least manageable, before it can be deployed at scale. We tested the OAE response of two natural seawater mixed layer microbial communities in the North Atlantic Subtropical Gyre, one at the Western gyre boundary, and one in the middle of the gyre. We conducted 4-day microcosm incubation experiments at sea, spiked with three increasing amounts of alkaline sodium salts and a 13C-bicarbonate tracer at constant pCO2. We then measured a suite of dissolved and particulate parameters to constrain the chemical and biological response to these additions. Microbial communities demonstrated occasionally measurable, but mostly negligible, responses to alkalinity enhancement. Neither site showed a significant increase in biologically produced CaCO3, even at extreme alkalinity loadings of +2,000 μmol kg−1. At the gyre boundary, alkalinity enhancement did not significantly impact net primary production rates. In contrast, net primary production in the central gyre decreased by ~30% in response to alkalinity enhancement. The central gyre incubations demonstrated a shift toward smaller particle size classes, suggesting that OAE may impact community composition and/or aggregation/disaggregation processes. In terms of chemical effects, we identify equilibration of seawater pCO2, inorganic CaCO3 precipitation, and immediate effects during mixing of alkaline solutions with seawater, as important considerations for developing experimental OAE methodologies, and for practical OAE deployment. These initial results underscore the importance of performing more studies of OAE in diverse marine environments, and the need to investigate the coupling between OAE, inorganic processes, and microbial community composition.
Continue reading ‘Microbial ecosystem responses to alkalinity enhancement in the North Atlantic subtropical gyre’Transitioning global change experiments on Southern Ocean phytoplankton from lab to field settings: insights and challenges
Published 30 June 2022 Science ClosedTags: Antarctic, biological response, BRcommunity, laboratory, light, mesocosms, molecular biology, multiple factors, nutrients, photosynthesis, physiology, phytoplankton, primary production, temperature
The influence of global change on Southern Ocean productivity will have major ramifications for future management of polar life. A prior laboratory study investigated the response of a batch-cultured subantarctic diatom to projected change simulating conditions for 2100 (increased temperature/CO2/irradiance/iron; decreased macronutrients), showed a twofold higher chlorophyll-derived growth rate driven mainly by temperature and iron. We translated this design to the field to understand the phytoplankton community response, within a subantarctic foodweb, to 2100 conditions. A 7-d shipboard study utilizing 250-liter mesocosms was conducted in March 2016. The outcome mirrors lab-culture experiments, yielding twofold higher chlorophyll in the 2100 treatment relative to the control. This trend was also evident for intrinsic metrics including nutrient depletion. Unlike the lab-culture study, photosynthetic competence revealed a transient effect in the 2100 mesocosm, peaking on day 3 then declining. Metaproteomics revealed significant differences in protein profiles between treatments by day 7. The control proteome was enriched for photosynthetic processes (c.f. 2100) and exhibited iron-limitation signatures; the 2100 proteome exposed a shift in cellular energy production. Our findings of enhanced phytoplankton growth are comparable to model simulations, but underlying mechanisms (temperature, iron, and/or light) differ between experiments and models. Batch-culture approaches hinder cross-comparison of mesocosm findings to model simulations (the latter are akin to “continuous-culture chemostats”). However, chemostat techniques are problematic to use with mesocosms, as mesozooplankton will evade seawater flow-through, thereby accumulating. Thus, laboratory, field, and modeling approaches reveal challenges to be addressed to better understand how global change will alter Southern Ocean productivity.
Continue reading ‘Transitioning global change experiments on Southern Ocean phytoplankton from lab to field settings: insights and challenges’Impact of atmospheric dry deposition of nutrients on phytoplankton pigment composition and primary production in the coastal Bay of Bengal
Published 29 June 2022 Science ClosedTags: biological response, BRcommunity, community composition, field, Indian, mesocosms, morphology, multiple factors, nutrients, photosynthesis, phytoplankton, primary production, toxicants
Atmospheric deposition of pollutants decreases pH and increases the nutrient concentration in the surface water. To examine its impact on coastal phytoplankton composition and primary production, monthly atmospheric aerosol samples were mixed with coastal waters in the microcosm experiments. These experiments suggested that the biomass of Bacillariophyceae, Dinophyceae and Chlorophyceae were increased and primary production of the coastal waters increased by 3 to 19% due to the addition of aeolian nutrients. The increase in primary production displayed significant relation with a concentration of sulphate and nitrate in the atmospheric aerosols suggesting that both decreases in pH and fertilization enhanced primary production. The impact of acidification on primary production was found to be 22%, whereas 78% was contributed by the nutrient increase. The atmospheric pollution is increasing rapidly over the northern Indian Ocean since past two decades due to rapid industrialization. Hence, it is suggested that the impact of atmospheric pollution on the coastal ecosystem must be included in the numerical models to predict possible changes in the coastal ecosystem due to climate change.
Continue reading ‘Impact of atmospheric dry deposition of nutrients on phytoplankton pigment composition and primary production in the coastal Bay of Bengal’Changing hydrographic, biogeochemical, and acidification properties in the Gulf of Maine as measured by the Gulf of Maine North Atlantic Time Series, GNATS, between 1998 and 2018
Published 8 June 2022 Science ClosedTags: abundance, biogeochemistry, calcification, chemistry, field, North Atlantic, otherprocess, photosynthesis, phytoplankton, primary production
The Gulf of Maine North Atlantic Time Series (GNATS) has been run since 1998, across the Gulf of Maine (GoM), between Maine and Nova Scotia. GNATS goals are to provide ocean color satellite validation and to examine change in this coastal ecosystem. We have sampled hydrographical, biological, chemical, biogeochemical, and bio-optical variables. After 2008, warm water intrusions (likely North Atlantic Slope Water [NASW]) were observed in the eastern GoM at 50–180 m depths. Shallow waters (<50 m) significantly warmed in winter, summer, and fall but cooled during spring. Surface salinity and density of the GoM also significantly increased over the 20 years. Phytoplankton standing stock and primary production showed highly-significant decreases during the period. Concentrations of phosphate increased, silicate decreased, residual nitrate [N*; nitrate-silicate] increased, and the ratio of dissolved inorganic nitrogen:phosphate decreased, suggesting increasing nitrogen limitation. Dissolved organic carbon (DOC) and its optical indices generally increased over two decades, suggesting changes to the DOC cycle. Surface seawater carbonate chemistry showed winter periods where the aragonite saturation (Ωar) dropped below 1.6 gulf-wide due to upward winter mixing of cool, corrosive water. However, associated with increased average GoM temperatures, Ωar has significantly increased. These results reinforce the hypothesis that the observed decrease in surface GoM primary production resulted from a switch from Labrador Sea Water to NASW entering the GoM. A multifactor analysis shows that decreasing GoM primary production is most significantly correlated to decreases in chlorophyll and particulate organic carbon plus increases in N* and temperature.
Continue reading ‘Changing hydrographic, biogeochemical, and acidification properties in the Gulf of Maine as measured by the Gulf of Maine North Atlantic Time Series, GNATS, between 1998 and 2018’Contrasting responses of phytoplankton productivity between coastal and offshore surface waters in the Taiwan Strait and the South China Sea to short-term seawater acidification
Published 8 June 2022 Science ClosedTags: biological response, BRcommunity, chemistry, field, North Pacific, photosynthesis, phytoplankton, primary production
Seawater acidification (SA) has been documented to either inhibit, enhance, or result in no effect on marine primary productivity (PP). In order to examine the effects of SA in changing environments, we investigated the influences of SA (a decrease of 0.4 pHtotal units with corresponding CO2 concentrations in the range of 22.0–39.7 µM) on PP through deck-incubation experiments at 101 stations in the Taiwan Strait and the South China Sea, including the continental shelf and slope, as well as the deep-water basin. The daily primary productivities in surface seawater under incident solar radiation ranged from 17–306 µg C (µg Chl a)−1 d−1, with the responses of PP to SA being region-dependent and the SA-induced changes varying from −88 % (inhibition) to 57 % (enhancement). The SA treatment stimulated PP in surface waters of coastal, estuarine, and shelf waters but suppressed it in the South China Sea basin. Such SA-induced changes in PP were significantly related to in situ pH and solar radiation in surface seawater but negatively related to salinity changes. Our results indicate that phytoplankton cells are more vulnerable to a pH drop in oligotrophic waters. Contrasting responses of phytoplankton productivity in different areas suggest that SA impacts on marine primary productivity are region-dependent and regulated by local environments.
Continue reading ‘Contrasting responses of phytoplankton productivity between coastal and offshore surface waters in the Taiwan Strait and the South China Sea to short-term seawater acidification’
