The GOA-ON South Asia Regional Hub on Ocean Acidification (SAROA) will hold its fourth in a dedicated series webinar later this week. The invited guest speaker, Dr Patrick Martin, Associate Professor at the Asian School of the Environment, Nanyang Technological University, Singapore, will address the broader topic of changes in the coastal carbonate system in the region. The main focus of Dr Martin’s research is carbon cycling and understanding how it is processed biogeochemically at sea and what effects it may exert on marine communities and ecosystems.
Anthropogenic disturbances, including non-indigenous species (NIS) and climate change, have considerably affected ecosystems and socio-economies globally. Despite the widely acknowledged individual roles of NIS and global warming in biodiversity change, predicting the connection between the two still remains a fundamental challenge and requires urgent attention due to a timely importance for proper conservation management. To improve our understanding of the interaction between climate change and NIS on biological communities, we conducted laboratory experiments to test the temperature and pCO2 tolerance of four gammarid species: two native Baltic Sea species (Gammarus locusta and G. salinus), one Ponto‐Caspian NIS (Pontogammarus maeoticus) and one North American NIS (Gammarus tigrinus). Our results demonstrated that an increase in pCO2 level was not a significant driver of mortality, neither by itself nor in combination with increased temperature, for any of the tested species. However, temperature was significant, and differentially affected the tested species. The most sensitive was the native G. locusta which experienced 100% mortality at 24 °C. The second native species, G. salinus, performed better than G. locusta, but was still significantly more sensitive to temperature increase than either of the NIS. In contrast, NIS performed better than native species with warming, whereby particularly the Ponto-Caspian P. maeoticus did not demonstrate any difference in its performance between the temperature treatments. With the predicted environmental changes in the Baltic Sea, we may expect shifts in distributions of native taxa towards colder areas, while their niches might be filled by NIS, particularly those from the Ponto-Caspian region. Although, northern colder areas may be constrained by lower salinity. Additional studies are needed to confirm our findings across other NIS, habitats and regions to make more general inferences.
Total alkalinity (TA) is a variable that reflects the acid buffering capacity of seawater, and is key to studies of the global carbon cycle. Daily and seasonal TA variations are poorly constrained due to limitations in observational techniques, and this hampers our understanding of the carbonate system. High quality and high temporal resolution TA observations are required to constrain the controlling factors on TA. Estuarine and coastal waters usually have low TA values and may experience enhanced remineralization of organic matter in response to processes such as eutrophication and terrestrial organic matter input. Therefore, these waters are considered vulnerable to acidification as a consequence of ongoing atmospheric anthropogenic carbon dioxide uptake. An In Situ Analyzer for seawater Total Alkalinity (ISA-TA) was deployed for the first time in low salinity, dynamic estuarine waters (Kiel Fjord, southwestern Baltic Sea). The ISA-TA and a range of additional sensors (for pH, pCO2, nitrate and temperature, salinity, dissolved oxygen) used to obtain ancillary data to interpret the TA variability, were deployed on a pontoon in the inner Kiel Fjord for approximately four months. Discrete samples (for TA, nutrients including NO3−, soluble reactive phosphorus (SRP) and H4SiO4, chlorophyll a) were collected regularly to validate the ISA-TA and to interpret the TA data. The effects on TA in the study area of nitrate uptake and of other processes such as precipitation, run-off and mixing of different waters were observed. The difference between the TA values measured with the ISA-TA and TA of discretely collected samples measured with the Gran titration method was −2.6 ± 0.9 μmol kg−1 (n = 106), demonstrating that the ISA-TA provides stable and accurate TA measurements in dynamic, low salinity (13.2–20.8), estuarine waters. The TA and ancillary data recorded by the sensor suite revealed that physical mixing was the main factor determining the variability in TA in Kiel Fjord during the study period.
Coastal warming, acidification, and deoxygenation are progressing primarily due to the increase in anthropogenic CO2. Coastal acidification has been reported to have effects that are anticipated to become more severe as acidification progresses, including inhibiting the formation of shells of calcifying organisms such as shellfish, which include Pacific oysters (Crassostrea gigas), one of the most important aquaculture resources in Japan. Moreover, there is concern regarding the combined impacts of coastal warming, acidification, and deoxygenation on Pacific oysters. However, spatiotemporal variations in acidification and deoxygenation indicators such as pH, the aragonite saturation state (Ωarag), and dissolved oxygen have not been observed and projected in oceanic Pacific oyster farms in Japan. To assess the present impacts and project future impacts of coastal warming, acidification, and deoxygenation on Pacific oysters, we performed continuous in situ monitoring, numerical modeling, and microscopic examination of Pacific oyster larvae in the Hinase area of Okayama Prefecture and Shizugawa Bay in Miyagi Prefecture, Japan, both of which are famous for their Pacific oyster farms. Our monitoring results first found Ωarag values lower than the critical level of acidification for Pacific oyster larvae in Hinase, although no impact of acidification on larvae was identified by microscopic examination. Our modeling results suggest that Pacific oyster larvae are anticipated to be affected more seriously by the combined impacts of coastal warming and acidification, with lower pH and Ωarag values and a prolonged spawning period, which may shorten the oyster shipping period and lower the quality of oysters.
Marine organisms are expected to be increasingly stressed by ocean acidification and ocean warming caused by the progressive anthropogenic increase in atmospheric CO2 levels and the absorption of approximately two-thirds of excess CO2 by the ocean. The responses of diverse ecological processes in economically and ecologically important holothuroids to the changing ocean have been of growing concern. Here we address some of them, including various aspects of gamete production, early life stages, biological function, and community interactions. In addition, future research needs and experimental considerations are highlighted.
Shallow and deep plants were exposed to ocean acidification and thermal stress;
Plants were unaffected by ocean acidification when not exposed to thermal stress;
Ocean acidification reduced plant performance under thermal stress;
Deep plants showed higher levels of heat stress at genetic and physiological levels;
Warming may play a key role in structuring future seagrass meadows.
Abstract
Despite the effects of ocean acidification (OA) on seagrasses have been widely investigated, predictions of seagrass performance under future climates need to consider multiple environmental factors. Here, we performed a mesocosm study to assess the effects of OA on shallow and deep Posidonia oceanica plants. The experiment was run in 2021 and repeated in 2022, a year characterized by a prolonged warm water event, to test how the effects of OA on plants are modulated by thermal stress. The response of P. oceanica to experimental conditions was investigated at different levels of biological organization. Under average seawater temperature, there were no effects of OA in both shallow and deep plants, indicating that P. oceanica is not limited by current inorganic carbon concentration, regardless of light availability. In contrast, under thermal stress, exposure of plants to OA increased lipid peroxidation and decreased photosynthetic performance, with deep plants displaying higher levels of heat stress, as indicated by the over-expression of stress-related genes and the activation of antioxidant systems. In addition, warming reduced plant growth, regardless of seawater CO2 and light levels, suggesting that thermal stress may play a fundamental role in the future development of seagrass meadows. Our results suggest that OA may exacerbate the negative effects of future warming on seagrasses.
Objective: To investigate the responses of Zostera marina seedlings to the individual and combined stresses of seasonal temperature increase and ocean acidification (OA) caused by global climate change and anthropogenic factors. This data will help in efforts to protect and restore seagrass beds in temperate coastal zones of China.
Methods: A mesoscale experimental system was utilized to analyze stress response mechanisms at multiple levels – phenotype, transcriptome, and metabolome – during the seedling stage of Z. marina, a dominant temperate seagrass species in China. The study monitored the seedlings under varying conditions: increased seasonal temperature, OA, and a combination of both.
Results: Findings revealed that under high-temperature conditions, carotenoid biosynthesis was stimulated through the upregulation of specific metabolites and enzymes. Similarly, the biosynthesis of certain alkaloids was promoted alongside modifications in starch, sucrose, and nitrogen metabolism, which improved the plant’s adaptation to OA. Unique metabolic pathways were activated under OA, including the degradation of certain amino acids and modifications in the citric acid cycle and pyruvate metabolism. When subjected to both temperature and OA stresses, seedlings actively mobilized various biosynthetic pathways to enhance adaptability and resilience, with distinct metabolic pathways enhancing the plant’s response under diversified stress conditions. In terms of growth, all treatment groups exhibited significant leaf length increase (p < 0.05), but the weakest growth index was observed under combined stress, followed by the thermal treatment group. Conversely, growth under OA treatment was better, showing a significant increase in wet weight, leaf length, and leaf width (p < 0.05).
Conclusion: Seasonal temperature increase was found to inhibit the growth of Z. marina seedlings to some extent, while OA facilitated their growth. However, the positive effects of OA did not mitigate the damage caused by increased seasonal temperature under combined stress due to seedlings’ sensitivity at this stage. Our findings elucidate differing plant coping strategies under varied stress conditions, contingent on the initial environment. This research anticipates providing significant data support for the adaptation of Z. marina seedlings to seasonal temperature fluctuations and global oceanic events like OA, propelling the effective conservation of seagrass beds.
Location:Old City Hall, 121 Prospect Street, Bellingham, 98225 United States
Join Dr. Brooke Love, oceanographer, and WWU associate professor, for a discussion about how ocean acidification and climate change are unfolding in our local Washington waters. Ocean acidification is driven by the carbon dioxide being added to the atmosphere, which then changes the chemistry of the oceans. These changes can influence how hard it is to make a shell or how easy it is for plants and algae to grow. Ocean acidification can affect anything from the survival of tiny oysters to the sense of smell in fish, affecting marine food webs in varied and unpredictable ways. Brooke will teach us about some of the more common responses among different kinds of organisms in the Salish Sea, and she will also tell us how people and policymakers are addressing these oceanic changes.
Published by Back to Blue, a new report Ocean Acidification: Time for Action calls on international government action to step up in a bid to prevent the worst case scenario from unfolding. It also criticises the majority of countries for ‘ocean blindness’, and failing to factor this issue into climate change adaptation and mitigation plans.
Currently, just 12 countries have in the world have ocean acidification action plans, yet if the problem is allowed to persist and become worse, some $400billion could be wiped off the global economy.
As oceans are allowed to become more acidic, a direct result of absorbing increasing amounts of carbon dioxide, the effect on marine life is unforgiving, including the creation of so-called ‘dead zones’, and the destruction of finely balanced ecosystems. In turn, this is a major threat to the survival of coastal communities, many of which have developed due to the abundant riches found under water, not least fisheries, meaning the livelihoods of vast swathes of people now hangs in the balance.
According to data, policy advice and research institution the OECD, globally some three billion people rely on oceans for their income. In the U.S., for example, almost half the national GDP is tied to counties that are coastal adjacent, and more than three-million jobs, or one-in-45, are directly dependent on resources within the sea or Great Lakes.
In Australia, our love of the ocean is truly profound – most of us live near the coast, we surf it, camp by it, we marvel at its incredible beauty from its many pristine sandy shores and we are proud of the unique and wondrous sea life that inhabits it.
Our oceans are in trouble. As our climate changes, driven by the unchecked burning of fossil fuels, our seas are transforming before our eyes. Marine heatwaves are surging, coral reefs are on the brink, ice sheets are melting at an alarming rate, currents are slowing and seas are rising. Put simply: the climate crisis is an ocean crisis.
The ocean is the beating heart of planet Earth, and the lifeblood for all humanity. It produces over half the oxygen we breathe. Its currents regulate our climate and weather. The marine life within it provides sustenance for billions. Our cultures, economies and very identity are tied to the sea.
We have pushed this wondrous, life-giving system to the brink by burning coal, oil and gas. More than 90 percent of the heat trapped by greenhouse gas emissions has been absorbed by the ocean. Parts of the ocean could reach a near-permanent heatwave state within decades.
Our iconic Great Barrier Reef may soon face annual mass coral bleaching. Entire island nations like Tuvalu and Kiribati could become uninhabitable this century as seas rise.
The ocean is a vital carbon sink, absorbing more than 30 percent of the carbon dioxide that humans emit by burning fossil fuels and clearing land. This has changed the chemical make-up of the entire ocean, making it more acidic.
By absorbing excess heat, and carbon, the ocean has shielded us from the worst of climate change so far. But we are now seeing the consequences of its sacrifice. The climate crisis is no longer a far-off threat. The ocean is screaming a warning that cannot be ignored.
Climate change has altered the physiochemical conditions of the coastal ocean but effects on infaunal communities have not been well assessed. Here, we used multivariate ordination to examine temporal patterns in benthic community composition from 4 southern California continental shelf monitoring programs that range in duration from 30 to 50 yr. Temporal changes were compared to variations in temperature, oxygen, and acidification using single-taxon random forest models. Species richness increased over time, coupled with a decline in overall abundance. Continental shelf macrobenthic communities from the 2010s comprised a broader array of feeding guilds and life history strategies than in the 1970s. Changing water temperature was associated with northward shifts in geographic distribution and increases in species abundance, while acidification was associated with southward shifts and declines in abundance of other species. Acidification was also associated with changes in depth distribution of benthic fauna, with shelled molluscs declining in abundance at depths most associated with increasing exposure to acidification. This broad-scale community-level analysis establishes causal hypotheses that set the stage for more targeted studies investigating shifts in abundance or distribution for taxa that appear to be responding to climate change-related disturbances.
Global atmospheric CO2 concentrations have increased from 320 ppm in the 1960s to the present-day value of 420 ppm, primarily due to anthropogenic activities. This increase influences the seawater carbonate system, impacting the marine ecosystem. There are still gaps that need to be resolved for predicting how these marine systems respond to current and future CO2 levels. Any actions to mitigate the change in pH will require adaptive management of multiple stressors across several spatial scales. Combined, these perspectives yield a more comprehensive picture of events during ocean acidification (OA).
This Research Topic brings together articles from different regions, including coastal, estuarine, and shelf areas and marginal seas, all susceptible to changing atmospheric conditions, riverine inputs, air-sea CO2 exchanges, and multiple acid-base reactions that can alter carbonate chemistry. Articles on the long-term trends of CO2 system descriptors and the interactions with calcifying organisms were also sought. The present Research Topic is primarily based on original articles devoted to carbonate systems in the marginal seas, but it is a pity that some interesting papers dealing with freshwater inflows, estuaries, and related coastal areas were not accepted.
Fransson et al. examined the effects of glacial and sea-ice meltwater on ocean acidification in the waters near the 79 North Glacier (79 NG) and the northeast Greenland shelf. The researchers investigated various ocean acidification factors and the influence of freshening, primary production, and air-sea CO2 exchange. One of the key findings was that the biological removal of CO2 through primary production played a crucial role in offsetting the negative impact of freshwater dilution on the aragonite saturation state (ΩAr), which is a measure of ocean acidification. This compensation effect was most pronounced in 2012, especially in the vicinity of the 79 NG front, where there was a significant presence of glacial meltwater and surface stratification. In 2016, a different scenario was observed, with a more homogenized water column due to sea-ice meltwater. In this case, the compensation effect of biological CO2 removal on ΩAr was weaker compared to 2012. The study also suggests that in the future, with ongoing climate and ocean chemistry changes, the increasing influence of meltwater may surpass the mitigating effects of biological CO2 removal. This could lead to unfavorable conditions for organisms that rely on calcium carbonate for their shells and skeletons. Thus, all the proposed factors need to be closely monitored as they could have significant implications for marine ecosystems and calcifying organisms in the face of ongoing environmental changes.
Courtesy Of Tacho According to a NOAA study, the most likely cause for the mass disappearance was starvation caused by a marine heatwave between 2018 and 2019.
When scientists estimated that more than 10 billion snow crab had disappeared from the Eastern Bering Sea between 2018 and 2021, industry stakeholders and fisheries scientists had several ideas about where they’d gone.
Some thought bycatch, disease, cannibalism, or crab fishing, while others believed it could be predation from other sea animals like Pacific cod.
But now, scientists say they’ve distinguished the most likely cause for the disappearance. The culprit is a marine heatwave between 2018 and 2019, according to a new study authored by a group of scientists with the National Oceanic and Atmospheric Administration.
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More carbon dioxide in the atmosphere means warmer temperatures, Litzow said, which is bad news for the cold-loving snow crab. And more greenhouse gasses also mean more acidic oceans, which can also be dangerous for some crab.
“Carbon dioxide that we release through fossil fuels is also taken up by the oceans and has the effect of reducing the pH of the ocean — it makes it more acidic,” Litzow explained. “Because crab use calcium carbonate in their exoskeleton, they’re vulnerable to that acidification because calcium carbonate dissolves more and more easily as pH goes down.”
The good news — at least for snow crab — is they’re not as sensitive to ocean acidification as other species.
Isaac Olson wonders why there is not a single visitor in sight at an aquarium’s ocean acidification exhibit. (Image credit: Shruthika Kandukuri)
Ocean acidification (OA) is one of the most imposing, yet still misunderstood, threats to our coasts. Even within aquariums, it can be hard to find detailed information about OA. This is a huge missed opportunity, especially as aquariums serve as one of the best places to not only educate people on marine issues, but also center issues in the affected communities. Indeed, the clock is ticking: OA is already becoming increasingly devastating ecologically, economically, and culturally. Yet, there is still an opportunity to mitigate much of the worst effects … if we act now. Thus, to enable equitable and sustainable change, it is vital to connect with people through OA communication that engages and empowers people to take action, especially in the most at-risk regions.
That’s why, as a class of 2022 Hollings Scholar, I worked with NOAA’s Ocean Acidification Program, the Aquarium Conservation Partnership, and the International Alliance to Combat Ocean Acidification on a project to address that knowledge gap. We created a suite of six StoryMaps intended for use in aquariums to educate, empower, and engage guests. Each StoryMap focuses on a different region in the NOAA Coastal Acidification Network (Alaska, the California Current, the Gulf of Mexico, the Southeast, the Mid-Atlantic, and the Northeast). Users can explore OA trends, impacts, and responses in their region, and learn how they can take action at both an individual and community level. The StoryMaps themselves are also highly adaptable for use by educators, community organizations, marine learning centers, and other groups: sections can be turned into interactive displays, sent out as virtual learning resources, and even uniquely individualized to increase community relevance.
Gelatinous zooplankton are increasingly recognized to play a key role in the ocean’s biological carbon pump. Appendicularians, a class of pelagic tunicates, are among the most abundant gelatinous plankton in the ocean, but it is an open question how their contribution to carbon export might change in the future. Here, we conducted an experiment with large volume in situ mesocosms (~55–60 m3 and 21 m depth) to investigate how ocean acidification (OA) extreme events affect food web structure and carbon export in a natural plankton community, particularly focusing on the keystone species Oikopleura dioica, a globally abundant appendicularian. We found a profound influence of O. dioica on vertical carbon fluxes, particularly during a short but intense bloom period in the high CO2 treatment, during which carbon export was 42%–64% higher than under ambient conditions. This elevated flux was mostly driven by an almost twofold increase in O. dioica biomass under high CO2. This rapid population increase was linked to enhanced fecundity (+20%) that likely resulted from physiological benefits of low pH conditions. The resulting competitive advantage of O. dioica resulted in enhanced grazing on phytoplankton and transfer of this consumed biomass into sinking particles. Using a simple carbon flux model for O. dioica, we estimate that high CO2 doubled the carbon flux of discarded mucous houses and fecal pellets, accounting for up to 39% of total carbon export from the ecosystem during the bloom. Considering the wide geographic distribution of O. dioica, our findings suggest that appendicularians may become an increasingly important vector of carbon export with ongoing OA.
Since the beginning of the industrial revolution, atmospheric carbon dioxide (CO2) concentrations have risen steadily and have induced a decrease of the averaged surface ocean pH by 0.1 units, corresponding to an increase in ocean acidity of about 30 %. In addition to ocean warming, ocean acidification poses a tremendous challenge to some marine organisms, especially calcifiers. The need for long-term oceanic observations of pH and temperature is a key element to assess the vulnerability of marine communities and ecosystems to these pressures. Nearshore productive environments, where a large majority of shellfish farming activities are conducted, are known to present pH levels as well as amplitudes of daily and seasonal variations that are much larger than those observed in the open ocean. Yet, to date, there are very few coastal observation sites where these parameters are measured simultaneously and at high frequency.
To bridge this gap, an observation network was initiated in 2021 in the framework of the CocoriCO2 project. Six sites were selected along the French Atlantic and Mediterranean coastlines based on their importance in terms of shellfish production and the presence of high- and low-frequency monitoring activities. At each site, autonomous pH sensors were deployed both inside and outside shellfish production areas, next to high-frequency CTD (conductivity- temperature-depth) probes operated through two operating monitoring networks. pH sensors were set to an acquisition rate of 15 min and discrete seawater samples were collected biweekly in order to control the quality of pH data (laboratory spectrophotometric measurements) as well as to measure total alkalinity and dissolved inorganic carbon concentrations for full characterization of the carbonate system. While this network has been up and running for more than two years, the acquired dataset has already revealed important differences in terms of pH variations between monitored sites related to the influence of diverse processes (freshwater inputs, tides, temperature, biological processes). Data are available at https://doi.org/10.17882/96982 (Petton et al., 2023a).
Occurrence of developmental malformations is of interest since they potentially influence organismal performance and fitness. We report an increased incidence (⁓ 46 fold) of physical malformations in the larvae of the American lobster Homarus Gammarus (Linnaeus, 1758) in response to seawater acidification (–0.58 pH units relative to nominal pH 8.0). We observed three malformations under the influence of seawater acidification previously undescribed in lobster larvae: a flared carapace, twisted tail, and cross claw. Larvae reared under seawater acidification exhibit significantly lower survivorship (by ⁓14%) and the occurrence of a malformation decreases survivorship (12.7%). Larvae with four types of malformations did not progress through development to reach post-larval stages. Namely, these malformations were a flared carapace, curled carapace, twisted tail, and cross claw. Results from this study provide photographic documentation of various lobster larval malformations that ultimately affect individual success and can be applied for quality-control in hatcheries.
This poem is inspired by recent research, which has found that ocean acidification in the Mediterranean is already affecting the calcification of marine plankton. The increasing levels of carbon dioxide emissions from human activities, such as the burning of fossil fuels, are not only warming our planet but are also causing a significant change in our oceans, known as ocean acidification. This process begins when the excess carbon dioxide in the atmosphere dissolves into seawater, forming carbonic acid. This acid then lowers the ocean’s pH, making the water more acidic. This shift in pH can have harmful effects on marine life, particularly on species that rely on calcium carbonate to build their shells and skeletons. The long-term consequences of ocean acidification, especially over decades to centuries, are complex and not fully understood, making it a critical area of environmental research. To better understand these impacts, the researchers studied three sediment cores from the Mediterranean Sea, which contain records spanning several centuries. They specifically looked at the weight, chemical composition, and other aspects of the shells of planktic foraminifera. The findings were concerning – as the levels of human-made carbon dioxide increased, these creatures’ shells became lighter, indicating weaker calcification. This is likely due to the increasing acidity of the ocean and the presence of carbon from fossil fuels. The study suggests that if carbon dioxide levels continue to rise, these tiny but vital sea creatures in the Mediterranean Sea will face increasing difficulties in building their shells, which could have broader implications for the marine ecosystem.Continue reading ‘Poetry of science: “dissolving depths” (text & video)’
We are excited to share the launch of the COP28 Virtual Ocean Pavilion, a free to access online platform dedicated to raising the visibility of the ocean and showcasing why the ocean matters in climate negotiations and to all life on our planet. You can access live and on–demand ocean and climate events, including high level speakers, explore exhibition booths, watch on-location COP28 reporting and interviews with delegates, take educational quizzes, earn certifications of attendance, access valuable networking opportunities and discover the treasure trove to learn more about the ocean and climate connection. The pavilion aims to democratize the ocean at COPs and promote unity and inclusivity, whilst increasing knowledge, commitment, and action for the ocean-climate nexus at key events during the UN Climate Conference (COP28) in Dubai, UAE, 30 November-12 December 2023. It is also a key tool in increasing transparency and equitable access to climate discussions and information. To aid this process you can find an overview of the ocean events taking place at the COP28 itself with livestreaming links where available.
The COP28 Virtual Ocean Pavilion is in its third year running and co-organized by the Global Ocean Forum and Plymouth Marine Laboratory with further collaborating partners from across the globe. The diversity of organizers and collaborating partners ensures a wide range of perspectives on ocean and climate issues and provides opportunities for forging cross-sectoral cooperation and collaboration on ocean-climate action at the national, regional, and global levels.
Seagrasses are important primary producers in oceans worldwide. They live in shallow coastal waters that are experiencing carbon dioxide enrichment and ocean acidification. Posidonia oceanica, an endemic seagrass species that dominates the Mediterranean Sea, achieves high abundances in seawater with relatively low concentrations of dissolved inorganic nitrogen. Here we tested whether microbial metabolisms associated with P. oceanica and surrounding seawater enhance seagrass access to nitrogen. Using stable isotope enrichments of intact seagrass with amino acids, we showed that ammonification by free-living and seagrass-associated microbes produce ammonium that is likely used by seagrass and surrounding particulate organic matter. Metagenomic analysis of the epiphytic biofilm on the blades and rhizomes support the ubiquity of microbial ammonification genes in this system. Further, we leveraged the presence of natural carbon dioxide vents and show that the presence of P. oceanica enhanced the uptake of nitrogen by water column particulate organic matter, increasing carbon fixation by a factor of 8.6–17.4 with the greatest effect at CO2 vent sites. However, microbial ammonification was reduced at lower pH, suggesting that future ocean climate change will compromise this microbial process. Thus, the seagrass holobiont enhances water column productivity, even in the context of ocean acidification.
