Limnology and Oceanography最新文献

Bi, S., and M. Hieronymi. 2024. “Holistic Optical Water Type Classification for Ocean, Coastal, and Inland Waters.” Limnology and Oceanography 69: 1547–1561. https://doi.org.10.1002/lno.12606.

In the original publication, there was an error in Equation (4) on page 1551. The equation for calculating the trapezoidal area at RGB bands was incorrectly written with a minus sign between the reflectance.

This was a typo that only appeared in the text document. All calculations, analyses, results, and conclusions presented in the paper were based on the correct formula. The scientific findings of the study are therefore unaffected by this error. The authors apologize for this error.

Microbial communities in Arctic coastal lagoons mediate nitrogen and carbon cycling at the terrestrial–marine interface of these rapidly changing ecosystems. To investigate these microbial processes, we measured gene expression, nitrification, and inorganic carbon assimilation in waters of Elson Lagoon on the Beaufort Sea coast under ice cover (April), during spring break-up (July), and in open water (August). Quantitative metatranscriptomics with internal controls quantified per-liter transcript abundances alongside in situ light and dark ¹⁵N-ammonium, ¹⁵N-urea, and ¹³C-bicarbonate stable isotope tracer incubations. Nitrification was only detectable during ice cover, showing high rates for Arctic coastal systems and evidence of light inhibition. Although carbon assimilation was relatively low during ice cover, dark carbon assimilation accounted for nearly half of total uptake, matching estimates of chemoautotrophic potential based on nitrification. Microbial gene expression also shifted seasonally in abundance and function. Transcripts for nitrification peaked during ice cover when genes for ammonia oxidation and 3-HP/4-HB carbon fixation were primarily expressed by archaeal genus Nitrosopumilus, while those for nitrite oxidation and reverse TCA carbon fixation were expressed by bacterial phylum Nitrospinota. During break-up and open water, expression shifted toward urea metabolism, nitrogen assimilation, Calvin Cycle carbon fixation, and anaplerotic pathways. These shifts highlight the seasonality of microbial metabolic strategies and reveal distinct functional shifts across the Arctic lagoon seasonal cycle. The findings suggest that ongoing warming and declining ice cover may reduce chemoautotrophic activity and alter nitrogen and carbon cycling under future conditions, with implications for nutrient dynamics and primary production in Arctic coastal ecosystems.

Horizontal/Vertical nutrient supply in the upper ocean of the North Pacific Subtropical Gyre (NPSG) plays a pivotal role in biogeochemical cycling and CO₂ uptake. However, research quantifying water/nutrient transport based on direct chemical observations and measurements is limited. Based on observations made during three GEOTRACES cruises in spring, summer, and winter, we identified horizontal and vertical water sources and quantified the water and nutrient supply, applying modified Optimum Multiparameter (OMP) analysis based on iterative calculation, in which rare earth elements (REEs) were used as quasi-conservative chemical tracers. The mean quantification results with a depth of ≤ 200 m show that Equator-derived water (Nutrient fraction: 51% ± 37%) and vertical supply (31% ± 33%) are the dominant nutrient sources; northern NPSG-derived water (0% ± 1%) has little influence; North Equatorial Current-derived water shows a higher contribution at 200–300 m (38% ± 26%) than the shallow layers (10% ± 19%); coast-derived water (7% ± 15%) contributes to NPSG in an inconsistent way. In addition, the enhanced vertical nutrient supply during the sampling period, which is more significant in spring, is likely to be attributed to the influence of what are considered different types of eddies based on the sea surface height. The vertical fluxes of dissolved inorganic nitrogen in the bottom euphotic layer at stations near warm, cold, and no eddies were estimated to be 0.10–0.76, 0.21–2.13, and 0.066–0.53 mmol m⁻² d⁻¹, respectively, which are 1–100 times the supply from nitrogen fixation. These nutrient fluxes could explain 5–169 mg C m⁻² d⁻¹ of the carbon fixation in the euphotic zone.

Silicic acid controls the production of diatoms, a predominant phytoplankton in the Southern Ocean. Diatoms are major contributors to the biological carbon pump, which is particularly active in the Southern Ocean as well as in areas naturally enriched in iron, such as around the Kerguelen Plateau. This study evaluates the factors controlling the biogeochemical cycle of Si and its dynamics in this area and how it is impacted by the island mass effect using the Si isotopic signatures of both dissolved and biogenic Si. While subsurface winter waters have similar δ³⁰Si signatures and dissolved Si concentrations, surface δ³⁰Si and dissolved Si values are different between stations. We show that this results from both (i) a different degree of dissolved Si utilization by silicifiers from winter water as the main Si source and (ii) an additional significant Si source to dissolved Si in the mixed layer from lithogenic Si dissolution for areas under the influence of the shelf. Indeed, the δ³⁰Si_DSi signatures near the islands are homogeneous and lighter by −0.33‰ ± 0.07‰ in the mixed layer compared to the outside plateau station. We estimate such lithogenic Si contribution to dissolved Si at 2.9 ± 1.8 μmol L⁻¹ for a corresponding specific flux of 3.7 ± 2.3 × 10⁶ mol km⁻² yr⁻¹ in shallow areas around Heard and McDonald Islands (< 100 m). This Si dissolution flux per surface area is among the highest in the ocean and has a traceable biogeochemical impact over the Northern Kerguelen Plateau. It is likely due to the active volcanic nature of these islands combined with subglacial erosion on Heard.

Sargassum species play a critical role in tropical and temperate coastal ecosystems by contributing to primary production and providing habitat to different species, while causing ecological disruptions and social challenges in some localities. As global warming intensifies, understanding how Sargassum species respond to rising seawater temperatures becomes increasingly important, and synthesizing evidence across diverse research approaches is critical to this goal. This study combines a comprehensive review and meta-analysis to evaluate the effects of warming on native and invasive Sargassum species in tropical and temperate regions. A total of 1471 studies were screened, of which 175 met the inclusion criteria and addressed Sargassum responses across tropical, warm-temperate, and cold-temperate regions. Our findings revealed that benthic native species are particularly vulnerable, with reduced growth rates and photosynthetic efficiency under projected warming scenarios in tropical and warm-temperate regions. In contrast, invasive species showed positive or neutral outcomes. Long-term monitoring and species distribution modeling studies supported these results, predicting significant habitat contractions and population declines for native species, while the invasive Sargassum muticum exhibited expanded ranges under future warming scenarios. These shifts could exacerbate ecological and social challenges, with cascading effects that compromise the functioning of ecosystems. Our study underscores the urgent need for monitoring programs and management strategies targeting Sargassum populations.

The littoral zone of lakes is recognized as hotspots of biogeochemical cycles. While the coupling of Fe(III) reduction and ammonium oxidation is acknowledged as an important nitrogen loss pathway, the role of anaerobic ammonium oxidation mediated by Mn oxides (Mnammox) remains uncertain. In this study, we conducted a ¹⁵NH₄⁺ isotopic incubation experiment and applied Mn oxides amended treatment to investigate the role of Mnammox in the lake littoral zone with respect to the N biogeochemical cycle. Our findings confirmed the widespread presence of Mnammox in the littoral zone of Baiyangdian Lake, the largest freshwater lake in the North China Plain. The sediment exhibited an average ³⁰N₂ production rate of 19.91 μg kg⁻¹ d⁻¹, accounting for approximately 2.0% of total nitrogen loss in situ. Significant nitrate production was also observed with a rate of 0.26 mg N kg⁻¹ d⁻¹, highlighting the role of Mnammox as a potential source of nitrate under anaerobic conditions. Furthermore, we identified a key threshold of 3.15 g kg⁻¹ dry weight sediment MnO₂ amendment, roughly 20 times the in situ MnO₂ content, which most significantly enhanced the Mnammox process. Sediment Mn oxides content, moisture content, and pH were the main stimulators for the Mnammox process, with unique microbial groups. This work underscores the importance of Mnammox in the lake littoral zone, illuminating the Mn–N coupling that drives multi-element cycles in this critical environment.

The Yellow Sea has experienced the world's largest green tide of Ulva prolifera in each of the last 18 yr. Limited understanding of the mechanisms controlling U. prolifera growth and death complicates mitigation efforts. Focusing on the crucial factors and processes affecting U. prolifera blooms, we constructed a nutrient–microalgae–U. prolifera–detritus (NmiAUD) model based on the results of field microcosm experiments. The NmiAUD model characterized the growth and death processes of U. prolifera and the nitrogen and phosphorus biogeochemical processes in the Yellow Sea with good reliability. Parameter sensitivity, process correlation analysis, and numerical experiments were used to identify the most critical factors and processes. Nutrient concentrations were the most important factors controlling the growth and death of U. prolifera, followed by seawater temperature, initial biomass, and photosynthetically active radiation, with contribution rates of 55.1%, 23.9%, 16.0%, and 5.0%, respectively. Nitrogen was more important than phosphorus, with nitrate-nitrogen accounting for 29.9%, followed by ammonium-nitrogen (26.3%), dissolved organic nitrogen (19.9%), phosphate-phosphorus (17.1%), and dissolved organic phosphorus (6.8%). The key processes comprised nutrient absorption, nutrient assimilation, degradation, detritus generation, dissolved organic matter mineralization, and detritus decomposition. Microalgae, which show high rates of growth, mortality, and nutrient uptake, are indicated to have a competitive advantage in the higher nutrient conditions in the South Yellow Sea, whereas U. prolifera is better adapted to the lower nutrient conditions in the North Yellow Sea. This study provides a scientific basis for the prevention and control of green tides.

Consumer-mediated nutrient dynamics (CND), through which animals' metabolic waste products fertilize primary producers, drive variability in nutrient availability in tropical waters. This variability influences primary productivity and community functioning. Yet, examinations of CND as a driver of nutrient variability in temperate marine ecosystems are limited. Therefore, we assessed the existence and drivers of variation in CND in temperate waters at meso, small, and fine spatial scales. We quantified the occurrence of 48 fish and 92 macroinvertebrate taxa and measured in situ ammonium at 27 northeast Pacific rocky reefs for 3 yr and 16 kelp forests of varying density for 1 yr. Ammonium concentrations ranged from 0.01 to 2.5 μM across rocky reefs separated by tens of kilometers. The relationship between animal abundance and ammonium among sites was mediated by water flow, where flood tides seemed to “wash away” the effect of nutrient regeneration by animals, although enrichment was possible on ebb tides. Ammonium concentration was significantly greater within than outside of kelp forests, a difference that increased with kelp biomass, tidal exchange, and, to a lesser degree, animal biomass. Caging experiments revealed that fine-scale (~ 2 m) ammonium variability and nutrient enrichment were only possible under low-flow conditions. Our results suggest that CND drives nutrient variability at scales ranging from two meters to over 20 km, acting on a finer scale than allochthonous nitrogen sources such as upwelling. Therefore, CND are implicated as a previously overlooked driver of spatial variation in primary productivity in temperate marine systems.

Trace elements are essential micronutrients for primary producers in the ocean, supporting vital metabolic functions. However, their behavior in the northwestern Pacific remains unknown. This study investigated the behavior and benthic fluxes of Mn, Fe, Co, Ni, Cu, Zn, and Cd in the East/Japan Sea and the Yellow Sea. Rare earth element fractionations ([Nd/Er]_PAAS and Ce/Ce* ratios) were used to trace scavenging and water mass inputs. In the East/Japan Sea, trace element distributions were categorized into three categories. Mn, Fe, and Co were influenced by atmospheric deposition in surface waters and benthic input, with fluxes of 742, 96, and 0.8 μmol m⁻² yr⁻¹, respectively. Ni and Cu were depleted from surface waters and had a limited influence from benthic inputs. Zn and Cd were regulated by biological activity. Zn concentrations ranged from 0.6 to 1.5 nmol kg⁻¹ at the surface, peaked at 6.8–11.8 nmol kg⁻¹ at a depth of 500 m, and decreased to 3.5–7.9 nmol kg⁻¹ at the bottom. Zn correlated positively with $��{\mathrm{SiO}}_4^{�4�-�}�$ in the upper 500 m but negatively at greater depths, likely owing to shelf inputs. In the Yellow Sea, all trace elements exhibited a vertically conserved distribution owing to rapid water mixing. These results contribute to the current biogeochemical understanding of the region by providing higher-resolution cross-transect investigations and report the decoupling of Zn–$��{\mathrm{SiO}}_4^{�4�-�}�$ in the East/Japan Sea for the first time.

Carbonate coral sands are an integral part of the carbon and nutrient cycles in subtropical and tropical coastal environments. Recent studies indicate that nearshore carbonate sands may be hotspots for organic matter production and respiration, but the processes and their controls are poorly understood due to a lack of noninvasive in situ measurements. We deployed a new triple-sensor aquatic eddy covariance instrument to quantify seasonal O₂-fluxes over a coral sand platform at ~ 10 m water depth in the Florida Keys. The noninvasive measurements revealed the strong influences of light and bottom currents on magnitude and dynamics of the benthic metabolism. Light penetration through the clear water column facilitated substantial microphytobenthos production, making the seafloor a source of oxygen during daylight hours. Daytime benthic O₂ release to the water column ranged between 0.6 mmol O₂ m⁻² h⁻¹ (winter) and 4.8 mmol O₂ m⁻² h⁻¹ (summer), while nighttime sediment O₂ respiration varied between −1.2 mmol O₂ m⁻² h⁻¹ (winter) and −3.3 mmol O₂ m⁻² h⁻¹ (summer). Bottom currents modulated the fluxes, emphasizing the role of advective pore water exchange for biogeochemical reactions in the highly permeable sediment. Similar magnitudes and dynamics of daytime sediment O₂ release and nighttime O₂ uptake revealed a tight coupling between production and degradation of highly labile photosynthetic products. We use the results to explain why O₂ respiration rates in permeable carbonate sands of oligotrophic subtropical/tropical environments can reach similar magnitudes as those reported from permeable silicate sand beds of nutrient-rich temperate inner shelves.