Ensuring that global warming remains <2 °C requires rapid CO
emissions reduction. Additionally, 100-900 gigatons CO
must be removed from the atmosphere by 2100 using a portfolio of CO
removal (CDR) ...methods. Ocean afforestation, CDR through basin-scale seaweed farming in the open ocean, is seen as a key component of the marine portfolio. Here, we analyse the CDR potential of recent re-occurring trans-basin belts of the floating seaweed Sargassum in the (sub)tropical North Atlantic as a natural analogue for ocean afforestation. We show that two biogeochemical feedbacks, nutrient reallocation and calcification by encrusting marine life, reduce the CDR efficacy of Sargassum by 20-100%. Atmospheric CO
influx into the surface seawater, after CO
-fixation by Sargassum, takes 2.5-18 times longer than the CO
-deficient seawater remains in contact with the atmosphere, potentially hindering CDR verification. Furthermore, we estimate that increased ocean albedo, due to floating Sargassum, could influence climate radiative forcing more than Sargassum-CDR. Our analysis shows that multifaceted Earth-system feedbacks determine the efficacy of ocean afforestation.
Seawater: Its Composition, Properties and Behaviour provides a comprehensive introduction to marine science. This book is divided into seven chapters. Chapter 1 summarizes the special properties of ...water and the role of the oceans in the hydrological cycle. The distribution of temperature and salinity in the oceans and their combined influence on density, stability, and vertical water movements are discussed in Chapters 2 to 4. The fifth chapter describes the behavior of light and sound in seawater and provides examples of the application of acoustics to oceanography. Chapter 6 examines the composition and behavior of the dissolved constituents of seawater, covering minor and trace constituents and major ions, as well as dissolved gases and biologically important nutrients. Residence times, speciation, and carbonate equilibria are also deliberated. The last chapter provides a short review of ideas about the history of seawater, involvement of the oceans in global cycles, and their relationship to climatic change. This publication is beneficial to oceanographers and marine biologists, including students that are interested in marine science.
Residual macronutrients in the surface Southern Ocean result from restricted biological utilization, caused by low wintertime irradiance, cold temperatures, and insufficient micronutrients. ...Variability in utilization alters oceanic CO
sequestration at glacial-interglacial timescales. The role for insufficient iron has been examined in detail, but manganese also has an essential function in photosynthesis and dissolved concentrations in the Southern Ocean can be strongly depleted. However, clear evidence for or against manganese limitation in this system is lacking. Here we present results from ten experiments distributed across Drake Passage. We found manganese (co-)limited phytoplankton growth and macronutrient consumption in central Drake Passage, whilst iron limitation was widespread nearer the South American and Antarctic continental shelves. Spatial patterns were reconciled with the different rates and timescales for removal of each element from seawater. Our results suggest an important role for manganese in modelling Southern Ocean productivity and understanding major nutrient drawdown in glacial periods.
The biodegradation of polycyclic aromatic hydrocarbons (PAHs) by marine-derived fungi was reported in this work. Marine-derived fungi (Trichoderma harzianum CBMAI 1677, Cladosporium sp. CBMAI 1237, ...Aspergillus sydowii CBMAI 935, Penicillium citrinum CBMAI 1186 and Mucor racemosus CBMAI 847) biodegraded anthracene (14days, 130rpm, 50mgmL−1 initial concentration in malt 2% medium). Cladosporium sp. CBMAI 1237 was the most efficient strain and biodegraded more anthracene in the presence (42% biodegradation) than in the absence (26%) of artificial seawater, suggesting that the biodegradation of PAHs may be faster in seawater than in non-saline environment. After 21days, Cladosporium sp. CBMAI 1237 biodegraded anthracene (71% biodegradation), anthrone (100%), anthraquinone (32%), acenaphthene (78%), fluorene (70%), phenanthrene (47%), fluoranthene (52%), pyrene (62%) and nitropyrene (64%). Previous undocumented metabolites were identified and, anthraquinone was a common product of different PAHs biodegradation. The marine-derived fungus Cladosporium sp. CBMAI 1237 showed potential for bioremediation of PAHs.
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•The biodegradation of different PAHs by marine-derived fungi was described.•Biodegradation in seawater medium was more efficient than in non-saline experiment.•Cladosporium sp. CBMAI 1237 biodegraded PAHs in previous undocumented metabolites.•Anthraquinone was a common biodegradation metabolite for different PAHs.•Cladosporium sp. CBMAI 1237 biodegraded all PAHs showing bioremediation potential.
Osmotic power, also known as 'blue energy', is produced by mixing solutions of different salt concentrations, and represents a vast, sustainable and clean energy source. The efficiency of harvesting ...osmotic power is primarily determined by the transmembrane performance, which is in turn dependent on ion conductivity and selectivity towards positive or negative ions. Atomically or molecularly thin membranes with a uniform pore environment and high pore density are expected to possess an outstanding ion permeability and selectivity, but remain unexplored. Here we demonstrate that covalent organic framework monolayer membranes that feature a well-ordered pore arrangement can achieve an extremely low membrane resistivity and ultrahigh ion conductivity. When used as osmotic power generators, these membranes produce an unprecedented output power density over 200 W m
on mixing the artificial seawater and river water. This work opens up the application of porous monolayer membranes with an atomically precise structure in osmotic power generation.
Neodymium isotopic compositions (143Nd/144Nd or εNd) have been used as a tracer of water masses and lithogenic inputs to the ocean. To further evaluate the faithfulness of this tracer, we have ...updated a global seawater εNd database and combined it with hydrography parameters (temperature, salinity, nutrients and oxygen concentrations), carbon isotopic ratio and radiocarbon of dissolved inorganic carbon. Archive εNd data are also compiled for leachates, foraminiferal tests, deep-sea corals and fish teeth/debris from the Holocene period (<10,000years).
At water depths ≥1500m, property-property plots show clear correlations between seawater εNd and the other variables, suggesting that large-scale water mass mixing is a primary control of deepwater εNd distribution. At ≥200m, basin-scale seawater T-S-εNd diagrams demonstrate the isotopic evolution of different water masses. Seawater and archive εNd values are compared using property-property plots and T-S-εNd diagrams. Archive values generally agree with corresponding seawater values although they tend to be at the upper limit in the Pacific. Both positive and negative offsets exist in the northern North Atlantic. Applying multiple regression analysis to deep (≥1500m) seawater data, we established empirical equations that predict the main, large-scale, deepwater εNd trends from hydrography parameters. Large offsets from the predicted values are interpreted as a sign of significant local/regional influence. Dominant continental influence on seawater and archive εNd is observed mainly within 1000km from the continents. Generally, seawater and archive εNd values form gradual latitudinal trend in the Atlantic and Pacific at depths ≥600m, consistent with the idea that Nd isotopes help distinguish between northern/southern sourced water contributions at intermediate and deep water depths.
The inclusion of organic compounds in freshly emitted sea spray aerosol (SSA) has been shown to be size-dependent, with an increasing organic fraction in smaller particles. Here we have used ...electrospray ionization-high resolution mass spectrometry in negative ion mode to identify organic compounds in nascent sea spray collected throughout a 25 day mesocosm experiment. Over 280 organic compounds from ten major homologous series were tentatively identified, including saturated (C8–C24) and unsaturated (C12–C22) fatty acids, fatty acid derivatives (including saturated oxo-fatty acids (C5–C18) and saturated hydroxy-fatty acids (C5–C18), organosulfates (C2–C7, C12–C17) and sulfonates (C16–C22). During the mesocosm, the distributions of molecules within some homologous series responded to variations among the levels of phytoplankton and bacteria in the seawater. The average molecular weight and carbon preference index of saturated fatty acids significantly decreased within fine SSA during the progression of the mesocosm, which was not observed in coarse SSA, sea-surface microlayer or in fresh seawater. This study helps to define the molecular composition of nascent SSA and biological processes in the ocean relate to SSA composition.
•An interfacial solar evaporation and planting system was designed.•The evaporator delivered high freshwater production (10.95 kg m−2 day−1).•Solar energy and seawater were harnessed for agricultural ...sustainability.•Highly saline soils were practically restored to productive agricultural soils.•Saline soil washing continuously generated clean water to support plant growth.
Interfacial solar steam generation is an efficient way to produce freshwater from saline water. This technology was further harnessed here for simultaneous saline soil remediation and enhanced agricultural sustainability. An interfacial solar evaporation and planting system was designed that uses treated seawater for saline soil washing and agricultural irrigation. In outdoor experiments the evaporator realized high freshwater production (10.95 kg m−2 day−1) with a soil washing efficiency 3 times greater than traditional distillation. Post treatment plant assays showed that initially highly saline soils could be restored to functional agricultural soils with germination rates of 65% after soil washing, where solar evaporation could continuously provide irrigation water for plant growth. This system is fully automated and uses only solar energy and seawater for saline soil remediation and irrigation. The development of this system provides a potentially useful solution to alleviate global problems associated with water scarcity, soil salinization, and desertification.
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Although halogen radicals are recognized to form as products of hydroxyl radical (•OH) scavenging by halides, their contribution to the phototransformation of marine organic compounds has received ...little attention. We demonstrate that, relative to freshwater conditions, seawater halides can increase photodegradation rates of domoic acid, a marine algal toxin, and dimethyl sulfide, a volatile precursor to cloud condensation nuclei, up to fivefold. Using synthetic seawater solutions, we show that the increased photodegradation is specific to dissolved organic matter (DOM) and halides, rather than other seawater salt constituents (e.g., carbonates) or photoactive species (e.g., iron and nitrate). Experiments in synthetic and natural coastal and estuarine water samples demonstrate that the halide-specific increase in photodegradation could be attributed to photochemically generated halogen radicals rather than other photoproduced reactive intermediates e.g., excited-state triplet DOM (3DOM*), reactive oxygen species. Computational kinetic modeling indicates that seawater halogen radical concentrations are two to three orders of magnitude greater than freshwater •OH concentrations and sufficient to account for the observed halide-specific increase in photodegradation. Dark •OH generation by gamma radiolysis demonstrates that halogen radical production via •OH scavenging by halides is insufficient to explain the observed effect. Using sensitizer models for DOM chromophores, we show that halogen radicals are formed predominantly by direct oxidation of Cl⁻ and Br⁻ by ³DOM*, an •OH-independent pathway. Our results indicate that halogen radicals significantly contribute to the phototransformation of algal products in coastal or estuarine surface waters.
Chemical analyses of 2,618 (1,640 new and 978 published) fluid inclusions in marine halite were used to define paleoseawater Ca2+ and SO2−4 over the past 550 million years (Myr). Three types of fluid ...inclusion brine chemistries were recognized based on measured Ca2+ and SO2−4: (1) SO4-rich with SO2−4 ≫ Ca2+; (2) Ca-rich with Ca2+ ≫ SO2−4; and (3) Ca-SO4 crossover points with Ca2+ ≈ SO2−4. The SO4-rich and Ca-rich fluid inclusion chemistries oscillated twice in the terminal Proterozoic and Phanerozoic. Transitions between SO4-rich and Ca-rich seas, here called “Ca2+−SO42−crossover points” occurred four times: terminal Proterozoic–Early Cambrian (544–515 Ma), Late Pennsylvanian (309–305 Ma), Triassic–Jurassic boundary (∼200 Ma), and Eocene–Oligocene (36–34 Ma). New fluid inclusion analyses using laser ablation-inductively coupled plasma-mass spectrometry better defined the Ca2+ and SO2−4 in seawater at the Late Pennsylvanian and Eocene–Oligocene crossover points and the timing of the Triassic–Jurassic crossover point. Crossover points coincide with shifts in seawater Mg2+/Ca2+ ratios, the mineralogies of marine non-skeletal carbonates and shell building organisms (aragonite vs. calcite) and potash evaporites (MgSO4 vs. KCl types). Phanerozoic and terminal Proterozoic trends in seawater Ca2+ and SO2−4 also coincide with supercontinent breakup, dispersal, and assembly cycles, greenhouse–icehouse climates, and modeled atmospheric pCO2. Paleoseawater Ca2+ and SO2−4 were calculated from the fluid inclusion data using the assumption that the Ca2+ × SO2−4 ranged from 150 to 450 mmolal2, which is 0.5–1.5 times the Ca2+ = 11 × SO2−4 = 29 product in modern seawater (319 mmolal2). Two additional end-member scenarios, independent of the Ca2+ × SO2−4 = 150–450 mmolal2 assumption, were tested using constraints from fluid inclusion Ca and SO4: (1) constant SO2−4 = 29 mmolal as in modern seawater, and variable Ca2+, and (2) constant Ca2+ = 11 mmolal as in modern seawater and variable SO2−4. Mg2+/Ca2+ ratios calculated from the three scenarios were compared to independent data on the Mg2+/Ca2+ ratios from skeletal carbonates (echinoderms and corals) and mid-ocean ridge flank calcite veins. Constant Ca2+ of 11 mmolal is unlikely because this relatively low concentration generated unreasonably low seawater SO2−4 during most of the past 550 Myr and high Mg2+/Ca2+ ratios compared to independent data. Constant SO2−4 of 29 mmolal produced unreasonably high seawater Ca2+ and lower Mg2+/Ca2+ ratios than those derived from fluid inclusions, echinoderms, corals, and calcite veins. Variable Ca2+ and SO2−4 showed the best agreement with the Mg2+/Ca2+ ratios derived from fluid inclusions, echinoderms, corals, and calcite veins.
•Seawater changed from SO4-rich to Ca-rich and vice versa at “crossover points”.•Crossover points occurred four times over the past 550 Myr.•Laser ablation analysis of fluid inclusions in halite documented Ca2+ and SO2−4.•The four crossover periods coincide with shifts in other marine records.
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