High Biological Productivity Research Articles

Early Cambrian highly metalliferous black shale in South China: Cu and Zn isotopes and a short review of other non-traditional stable isotopes

Early Cambrian black shales on the Yangtze Platform host a regionally distributed highly metalliferous sulfide-rich carbonaceous unit which has been the subject of extensive debate. This marker unit, with a few centimeters or tens of centimeters in thickness, displays extreme enrichment in Mo and Ni (wt% range), and in a broad spectrum of other metals such as As, Au, PGE, Re, Cu, Zn, Cd, Ag, Sb, Se, Tl, and Hg, and occurs discontinuously along the western passive margin of the Yangtze Platform. It grades laterally in stratigraphically equivalent meter-thick vanadium-rich shale and tens-of-meter-thick sapropelite (combustible shale). New Cu and Zn isotope data, combined with existing Cd, Cr, Ni, Mo, Hg, and Se isotope and other chemical data, allow to attempt an integrated view on the formation of this intriguing unit of hyper-enriched metalliferous black shale. The authigenic Cu enrichment in the 1000-ppm range has produced no or little Cu isotope fractionation (0.03 ± 0.26 ‰ δ65Cu) beyond the lithogenic background. Heavy zinc and cadmium isotope enrichment in the sulfidic samples (1.11 ± 0.18 ‰ δ66Zn, 0.31 ± 0.10 ‰ δ114Cd) is controlled by sulfide fractionation and contrasts with V-rich and barren shale (0.60 ± 0.18 ‰ δ66Zn, 0.00 ± 0.14 ‰ δ114Cd). The distinctly negative Ni isotope composition of the metalliferous unit (−0.84 ± 0.05 ‰ δ60Ni) with Ni in the percent range has been interpreted as due to hydrothermal activity related to the leaching of mafic rocks and their sulfides. Sorption processes (Fe-oxyhydroxides) and redox cycling in the water column and the bottom sediment with microbial activity could be an alternative interpretation. The extreme metal enrichment can be understood as due to a process chain, from high biological productivity in the oxic photic zone to sulfate reduction in the deeper sulfidic water column and upper sediment layer. Key to the metal enrichment seems to be extremely low clastic sedimentation and advanced carbon destruction by anaerobic oxidation. Hydrothermal input of basinal brines along the rifted margin of the Yangtze Platform was likely a part of this scenario.

Carbon, oxygen and strontium isotopic and elemental characteristics of the Cambrian Longwangmiao Formation in South China: Paleoenvironmental significance and implications for carbon isotope excursions

The biosphere experienced episodic perturbations during the Neoproterozoic–early Cambrian, accompanied by major fluctuations of the carbon cycle. However, compared to the Ediacaran–early Cambrian, geochemical records of the Cambrian Toyonian Stage (Longwangmiao), which contains the significant Redlichiid–Olenellid Extinction Carbon Isotope Excursion (ROECE), are scarce. To address this data gap, we conducted measurements of carbon, oxygen and strontium isotopes and element contents of a continuous series of carbonate samples from the Longwangmiao Formation of Well HS2, located in the central Sichuan Basin of South China. Our specific aims were to reconstruct the paleoenvironment and to determine the origin of the ROECE. Strict sample screening was used to ensure that the isotopes and elements were not affected by diagenesis. The 87Sr/86Sr values of Well HS2, and for sites elsewhere, show that sea level gradually decreased during the Cambrian Toyonian Stage. Additionally, the pronounced negative δ13C excursion in the late Toyonian is globally associated with the ROECE, which is widely thought to have resulted from extinctions caused by a transgression. However, a transgression is not shown in the 87Sr/86Sr profile of Well HS2, which we attribute to local karst formation and erosion caused by frequent regional regressions. The interrelationships among several paleoenvironmental proxies show that continental weathering was climatically controlled, which affected the supply of terrigenous detritus, and that the carbonate platform was semi–restricted. Furthermore, profiles of paleoenvironmental proxies indicate that the environment was warm and humid, favoring high biological productivity and diversity during Interval I (early Toyonian), and that it gradually became colder and drier during Interval II (middle Toyonian). We suggest that by the time of Interval III (late Toyonian), the adverse effects of a cold and arid environment were superimposed on the transgression, triggering the ROECE. Our results provide a reference and possible interpretation for other carbon isotope excursion events.

Hydrocarbon accumulation characteristics in the inter-salt shale oil reservoir in the Eocene Qianjiang Depression, Hubei Province, China

Research on the migration and accumulation of hydrocarbons in shale oil reservoirs composed solely of organic-rich mudstones has not received adequate attention. The Qianjiang Formation provides an opportunity for research on the hydrocarbon accumulation mechanism due to the presence of hydrocarbon migration characteristics in its inter-salt organic-rich fine-grained rocks. In this study, the inter-salt stratum of the tenth rhythmite can be classified into three sections: lower, middle, and upper. The middle section is mostly composed of laminated marlstones and laminated calcite-bearing argillaceous dolomicrites, whereas, the lower and upper sections mostly contain bedded muddy dolomicrites and glauberite. Geochemical analysis was conducted to study the organic matter enrichment mechanism and shale oil accumulation characteristics. The results indicate that the middle section has the highest organic matter abundance, with poor organic matter abundance displayed by the other sections. The C27/C29 sterane and extended tricyclic terpane ratios suggest that the organic matter types in different sections of the inter-salt stratum differ, and the middle section has more aquatic organic matter than other sections. The sedimentary structures and salinity-related parameters indicate that the middle section was developed in a deep stratified saline lake and that the other sections were formed in a shallow hypersaline lake. This study shows that high biological productivity and stratified lake water facilitated the enrichment of organic matter, resulting in high organic matter content in the middle section. The oil saturation index and hydrocarbon composition suggest that hydrocarbons were differentially accumulated in the inter-salt stratum of the tenth rhythmite. The maturity-related biomarkers further revealed the possible migration paths of hydrocarbons in the inter-salt stratum. Based on the aforementioned analyses, this study established an inter-salt shale oil accumulation model. This study suggests that hydrocarbons were released from the mature source rocks in the deep depression with differential migration laterally and vertically within the inter-salt stratum. The study of the Qianjiang Depression shows that organic-rich fine-grained rocks cannot only form in situ sweet spots but may also possess migrated hydrocarbons inside them, which are characterized by high organic matter abundance and oil saturation. This research provides a new case for further understanding hydrocarbon accumulation inside source rocks.

Evaluating the potential of aquaculture in the Hoa Binh reservoir with carrying capacity and water quality indices

Not only does the Hoa Binh reservoir play essential roles in water storage for electricity generation and flood regulation, but also it has great potential to aid aquaculture production. Presently, aquaculture production sits at around 9,200 tons/year; however, a recent MARD circular (#16 in 2015) estimated that maximum production would approach 10,000 tons/year in the productive photic zone. This paper supports increased capacity towards a sustainable commodity production model by optimizing production levels and farming practices. To reach this goal, it is necessary to determine water quality parameters using the Relative Water Quality Index (ReWQI) and carrying capacity (CC) analysis. Data was obtained from 30 sites at upstream, midstream, and downstream sections of the reservoir during the 2019 dry and wet seasons. The results from the ReWQI reflected good water quality potential (rated between 92-100) for aquaculture. The total nitrogen (TN) and total phosphorus (TP) levels of 10,794.9 kg/day and 1,965.4 kg/day, respectively, indicate high biological productivity resulting in strong fish growth potential. CC analysis and overall water quality reflect the potential for sustainable and increased productivity to 22,730.4 tons/year, which is an increase in production of over 13,200 tons/year compared to the current period. To reach a higher yield of 40 kg/year/m3 within each cage (5,040 kg/cage/year), the corresponding increase in number needs to be 4,510 cages based on a common cage size of 126 m3 (6x6x3.5 m). In order to reach these future production goals, this work concludes that the local government should begin spatial planning decisions based on appropriate cage allocation and distribution with respect for regular monitoring of water quality and nutrient load capacity of the environment to reach sustainable aquaculture development.

Assessment of Wetland Ecosystem Services in Tien Yen Estuary, Quang Ninh Province

Wetland ecosystems have provided high biological productivity, played an important role in the stability and development of coastal people. The wetland ecosystem service (WES) assessment is an effective tool for calculating direct and indirect benefits that humans obtained from these ecosystems based on monetary valuation. The value of WES in the Tien Yen estuary area has been assessed and calculated using a combination of different methods, including cost-benefit analysis, questionnaire survey, and remote sensing and GIS. The results showed the particular monetary values of 11 WES obtained from 10 wetland ecosystems and total WES value in the study area. The outcome can become the scientific basis to choose the suitable solutions for sustainable use of natural resources in the relationship between preservation and exploitation of wetlands in the future.
 

Coupled changes in western South Atlantic carbon sequestration and particle reactive element cycling during millennial-scale Holocene climate variability

AbstractContinental shelves have the potential to remove atmospheric carbon dioxide via the biological pump, burying it in seafloor sediments. The efficiency of marine carbon sequestration changes rapidly due to variations in biological productivity, organic carbon oxidation, and burial rate. Here we present a high temporal resolution record of marine carbon sequestration changes from a western South Atlantic shelf site sensitive to Brazil Current-driven upwelling. The comparison of biological records to rare earth element (REE) patterns from authigenic oxides shows a strong relationship between higher biological productivity and stronger particle reactive element cycling (i.e. REE cycling) during rapid climate change events. This is the first evidence that authigenic oxides archive past changes in upper ocean REE cycling by the exported organic carbon. In addition, our data suggest that Brazil Current-driven upwelling varies on millennial-scales and in time with continental precipitation anomalies as registered in Brazilian speleothems during the Holocene. This indicates an ocean–atmosphere control on the biological pump, most probably related to South American monsoon system variability.

EFFECT OF POULTRY LITTER BIOCHAR ON THE NUTRITIONAL STATUS OF CORN1

ABSTRACT Corn, one of the main grain crops in Brazil, needs to have its nutritional requirements fully satisfied to achieve high biological productivity. Thus, the objective of this work was to evaluate the influence of increasing doses of poultry litter biochar on nutrient concentrations in the leaves of hybrid corn BRS 2022 and in the soil after harvest. The experiment was carried out in a completely randomized design, with four replicates, evaluating six doses of biochar (0; 2.02; 4.05; 6.07; 8.10 and 10.12 t ha-1) and the plots composed of one plant per pot with a volume of 20 dm3. The collection of leaves for leaf diagnosis was carried out at the time of flowering, removing the opposite leaf from the ear base in the middle third region. These leaves were dried in a forced air circulation oven, 65 °C, for a period of 48 hours, ground, sieved through 20 mesh and analyzed for the concentrations of macronutrients in the leaf tissue. At the end of the experiment, 83 days after corn sowing, soil samples were collected as a function of the treatments and then analyzed chemically. Biochar application promoted an increase in the leaf contents of N, P and K, resulting in improvements in the nutritional status of plants for these nutrients. The chemical characteristics of the soil, analyzed after the corn harvest, revealed that there was an influence of the doses of biochar on the levels of calcium, organic carbon, potassium and phosphorus.

Characterization of hydrological features and plankton during neap tides in a subtropical lagoon south of the California Current

ABSTRACT This study aimed to characterize their Spatio-temporal distribution of hydrological variables and plankton during neap tides in Bahía Magdalena, a subtropical lagoon south of the California Current. We compare data from surface and bottom waters of stations located inside the lagoon with those near the bay's mouth and between surface and bottom. The availability of nutrients and the chlorophyll-a are associated primarily with the intense upwelling activity in spring. Due to direct marine influence, this relationship was more significant at the inlet than inside the lagoon, especially at the bottom. During the intense upwellings marine influence is maintained even during neap tides. The wind probably causes the homogeneous distribution in most variables within the bay's surface; this may also contribute to the re-suspension of nutrients due to vertical water column mixing. Abiotic variables were not linearly related with zooplankton biovolume and the density of diatoms and dinoflagellates. Phytoplankton was composed mainly by the micro fraction and diatoms during spring and nanoplankton in the warmest season of the year; however, the strong upwellings at the spring's end caused a HAB composed for diatoms. Chlorophyll-a concentration and diatoms were more abundant inside the lagoon and could explain the lower nutrient concentration of that zone. Zooplankton biovolume seasonality differed from other years, with higher values during winter and a significant decreasing trend throughout the year, resulting from the phytoplankton variability. Upwelling and wind variability explains the high biological productivity observed over most of the year.

Morphological, Histochemical and Biochemical Features of Cultivated Rhodiola rosea (Altai Mountains Ecotype).

The study analyzed the content and localization of phenolic compounds, in particular phenylpropanoids, of Rodiola rosea plants of Altai Mountains ecotype during the introduction period of 2–4 years in the conditions of the forest-steppe zone of Western Siberia. The plant material for the introduction experiment was obtained by in vitro method. HPLC was used to identify 11 phenolic compounds, including gallic acid, rosarin, rosavin, rosin, cinnamyl alcohol, rhodiosin, rhodionin, and kaempferol. The highest content of phenylpropenoids was found in rhizomes of the 4-year-old R. rosea plants: 1.02% rosarin, 2.64% rosavin, 1.05% rosin, 3.39% cinnamyl alcohol. Analysis of the phenylpropanoid profile showed that the predominant component in all the studied samples was cinnamyl alcohol (up to 58%). Histochemical studies identified phenolic substances in the rhizomes and roots of R. rosea, which are localized in parenchymal and vascular tissues. It was revealed that the total rhizome biomass exceeded that of the root, and by the 4th year of introduction, it was approximately 2-fold greater in dry weight. The study showed high biosynthetic potential and biological productivity of the studied R. rosea ecotype upon introduction.

Effect of barite-bound Sr on detrital Sr isotope systematics in marine sediments

In marine sediments, the Sr content and isotope composition (87Sr/86Sr) of the terrigenous detrital component are widely used to track changes in provenance and related transport and weathering processes. Accurately separating detrital-Sr from other sedimentary Sr-phases is a prerequisite for such studies. Conventionally, it is assumed that Sr in the carbonate-free residue corresponds to detrital Sr alone. However, the decarbonated residue may contain barite with significant Sr content and a non-detrital 87Sr/86Sr composition; this may substantially affect the measured Sr signal. To examine this chronically overlooked phenomenon, the Mediterranean Sea is an ideal area because 1) detailed provenance studies have been done using Sr and 87Sr/86Sr of the residual fraction, and 2) enhanced levels of barite repeatedly occurred in association with distinct, organic-rich sapropel sediments.Here, we use the most-recent sapropel S1 interval to evaluate the effect of barite-bound Sr in the residual fraction after decarbonation. A total of 130 samples were taken from 10 cores in the eastern Mediterranean Sea (EMS) and 1 core in the western Mediterranean Sea. This selection represents a geographic and bathymetric coverage of the EMS and permits the basin-wide comparison between organic-rich and -lean sediments. After decarbonation using 1 M HCl solution, the residual sediments were subject to NH4Cl extraction (2 M, pH 7), known to selectively dissolve barite. Our results demonstrate the presence of Sr-bearing barite after traditional carbonate removal and its effect on the derived “detrital” Sr signature. This barite-Sr effect is considerable for samples with barite-Ba >400 μg/g in bulk sediment. The impact of barite is prominent if accompanied by a detrital provenance background of high 87Sr/86Sr (>0.713) or low Sr/Al (<1.0 mg/g). In such cases, removal of remaining barite is required to obtain an unbiased detrital Sr signal. We recommend an improved procedure for detrital Sr separation in marine sediments, with an additional NH4Cl leaching step to eliminate any remaining barite after decarbonation. This approach is particularly important for areas/times of high biological productivity, where sediments are often characterized by abundant barite content.

Seasonal dynamics of phytoplankton phosphorus stress in temperate Jiaozhou Bay, North China

Alkaline phosphatase activity (APA) is always used to evaluate the phosphorus (P) status of phytoplankton community and considered as a proxy for phosphate (DIP) stress or deficiency. In this study, we presented seasonal distributions of APA [including free APA (F-APA) and particulate APA (P-APA)] and enzyme kinetics and compared to the distribution of phosphorus concentrations, planktonic biomass and other environmental variables reflecting community P status in moderate DIP-deficient Jiaozhou Bay, North China. Low potential APA (Vmax) were detected in winter (mean 51.3 nM h-1), which was probably due to low water temperature, while higher APA corresponded well to high phosphate requirement and high biological productivity in other three seasons. Normalized total APA (specified by chlorophyll a and bacteria biomass) showed an inverse hyperbolic relationship with DIP and the threshold phosphate concentration for the transition from high to low APA was around 0.2 μM in Jiaozhou Bay. Combined with results of APA, P concentrations (including DIP and DOP) and half saturation constant (Km), our findings suggested that phytoplankton and bacteria in Jiaozhou Bay may be experiencing a relief from P-limitation in winter; while in other three seasons, these organisms were mainly under persistent P stress. Moreover, in order to compensate for phosphate deficiency, we hypothesize that plankton not only by means of promoting enzyme production as indicated by increase of Vmax, but also by an improved enzyme affinity as represented by a decrease of the Michaelis constant (Km). Consequently, higher APA and lower DOP stocks in summer were probably a result of greater utilization of the DOP pool to maintain high primary production.

Role of mesoscale eddies in the sustenance of high biological productivity in North Eastern Arabian Sea during the winter-spring transition period

Convective mixing, mesoscale eddies and regenerated production sustain an above-average biological productivity in the North East Arabian Sea (NEAS) during the winter-spring transition period. Satellite-derived long-term data sets on Chlorophyll-a (Chl-a), Sea Surface Height Anomaly (SSHA), Sea Surface Temperature (SST) and Okubo-Weiss parameterization show existence of number of mesoscale eddies, propagating and non-propagating, that contribute to the regional production. The dominance of Eddy Kinetic Energy (EKE) over the Available Potential Energy (APE) in the core depth and the diameter (120km) of the observed eddy being wider than the Rossby Radius of Deformation (RRD, 55 km), it is suggested that the baroclinic instability is a possible mechanism for the eddy formation. Spatial variation in APE and its influences on the regional dynamics, including chemical and biological response are explained. In the non-eddy areas, where convective mixing is active, diatoms (96.74%) dominated than dinoflagellates (3.14%), and the Chl-a in the Cold Core Eddy (CCE) were two to three folds higher to non-eddy regions. The abundance increased from core (58,152 cells L−1) to periphery (5.95 × 105 cells L−1) where the water column is less dynamic. Extensive blooms of the dinoflagellate green Noctiluca (N. scintillans) contribute to the very high cell density in the periphery of the CCE, where the currents were comparatively weak, and water column was more stable. Active mixing is associated with diatom dominance, followed by Noctiluca when the mixing slackens, making use of the available nutrients and supported by regenerated production. The bloom dynamics is explained for pre-bloom, bloom and post-bloom conditions with measurements on nutrients and plankton assemblages. The Noctiluca bloom (mid-March) is succeeded by Trichodesmium (April–May), in the stratified nutrient depleted, abundant light environment and propagated southwards. Observed increasing trends in the SSHA over the period indicate strengthening of stratification and hence altered production patterns in the NEAS.

Seasonality of stranded tetrapod fauna in the Paraty Bay, Rio de Janeiro, Brazil

The high biological productivity presented along the Brazilian coast guarantees availability of resources and also protects a diverse community of marine tetrapods. Physical and biological factors can influence in these animal mortality rates and the analysis of stranding patterns helps to comprehend the external threats, as anthropic. We analysed the effects of seasonality in richness and abundance of marine tetrapods stranded between 2016 and 2020 in the Paraty Bay, Rio de Janeiro, Brazil. In total, 588 strandings were recorded, Chelonia mydas as being the species with more abundance, followed by Sula leucogaster and Sotalia guianensis. Among the 28 species, birds richness were the highest, followed by marine mammals and reptiles. There was no significant difference in the numbers of stranding records throughout the different seasons. There was more similarity in the assemblies between spring and summer. Birds and reptiles had stranding records distributed mostly in winter and spring, with the majority of marine mammals stranding being concentrated during the spring season. The strandings patterns of marine tetrapods throughout a temporal sequence in the Paraty Bay generated data that can provide animal behavior understandings and population distributions of marine tetrapods and supplement data for management plans and conservation.

Self-organization of salt marsh patches on mudflats: Field evidence using the UAV technique

The salt marsh system on the tidal flat is one of the most productively ecological wetlands with high biological productivity and blue carbon sequestration levels. The evolution of salt marshes-bare flats boundaries and the shapes of salt marsh margins are of scientific and engineering prospects due to the capability on indicating the morphodynamic patterns of tidal flats. Previous studies are almost qualitative, so far, quantitative analysis on this issue is scarce. To improve our understandings on the spatio-temporal characteristics of salt marsh margins and the mechanism underpinning, we extracted datasets on Spartina alterniflora using orthoimages derived from the quarterly-surveyed UAV photographs and satellite imagery. Results show that the patch-size distribution corresponded to the power law, indicating the marsh patches are in the state of self-organized criticality and the system is scale-independent. It was observed that the external dynamic conditions (i.e., the sediment erosion and accretion on the tidal flat) imposed negative impacts on the self-organization process. In particular, when the short-term morphological changes were negligible, R2 of the power-law relationship notably increased to nearly 1, indicating the salt marsh patches tended to adhere to a high-order self-organization structure in this process.

Causes of uncertainties in the representation of the Arabian Sea oxygen minimum zone in CMIP5 models

Abstract. Open-ocean oxygen minimum zones (OMZs) occur in regions with high biological productivity and weak ventilation. They restrict marine habitats and alter biogeochemical cycles. Global models generally show a large model–data misfit with regard to oxygen. Reliable statements about the future development of OMZs and the quantification of their interaction with climate change are currently not possible. One of the most intense OMZs worldwide is located in the Arabian Sea (AS). We give an overview of the main model deficiencies with a detailed comparison of the historical state of 10 climate models from the 5th Coupled Model Intercomparison Project (CMIP5) that present our present-day understanding of physical and biogeochemical processes. Most of the models show a general underestimation of the OMZ volume in the AS compared to observations that is caused by an overly shallow layer of oxygen-poor water in the models. The deviation of oxygen values in the deep AS is the result of oxygen levels that are too high simulated in the Southern Ocean formation regions of Indian Ocean Deep Water in the models compared to observations and uncertainties in the deepwater mass transport from the Southern Ocean northward into the AS. Differences in simulated water mass properties and ventilation rates of Red Sea Water and Persian Gulf Water cause different mixing in the AS and thus influence the intensity of the OMZ. These differences in ventilation rates also point towards variations in the parameterizations of the overflow from the marginal seas among the models. The results of this study are intended to foster future model improvements regarding the OMZ in the AS.

Zooplankton of the low-oxygen waters of Bahia Callao (Central Peru) - with special reference to the reproductive activity of the copepod Acartia tonsa

Zooplankton distribution in the Bahia Callao, a low oxygen bay in Central Peru, was studied during surveys in March (austral summer) and September (austral spring) 2006. In March temperature was higher, but oxygen concentrations were much lower, especially near the sea floor. Zooplankton abundance at 14 repeated stations (March/September = 457/2356 ind. m−3), taxa number (35/97), and community composition changed drastically, but Acartia tonsa was dominant during both surveys. In contrast, abundance of meroplanktonic larvae did not change.The reproductive activity of A. tonsa was studied bi-weekly from November 2005 to August 2007 at a fixed station close to shore (9 m water depth). Population egg production rate ranged from 0.9 to 12.6 eggs female−1d−1 and was significantly related to Chlorophyll a, temperature, and dissolved oxygen. Individual clutch size ranged from 1 to 43 eggs. Egg hatching rate varied from 3.4 to 100%; the lowest values were associated with very low concentrations of dissolved oxygen in the surface layer and red tides. In feeding experiments at saturated oxygen concentrations >30 eggs female−1d−1 were produced, indicating continuous inhibition of egg production in the field. Oceanographic data demonstrate that the bay, and probably also the adjacent shelves, are exposed to frequent environmental changes, which challenge the survival and production of zooplankton and fish. The relationship between seemingly adverse environmental conditions and high biological productivity still needs to be understood.

Features of growth and development of Scutellaria baicalensis Georgi under conditions of introduction in the Middle Urals

Abstract. An experiment on the topic “Features of the growth and development of Scutellaria baicalensis Georgi under conditions of introduction in the Middle Urals” was carried out at the educational farm “Uralets”. Purpose of the study: to study the influence of the feeding area on the growth and development of Scutellaria baicalensis Georgi. The objectives of the study were to study the influence of the feeding area on: the dynamics of height and average daily growth, dates of the onset and timing of phenological phases, biometric indicators of leaves and inflorescences, structural composition of aboveground biomass, productivity of aboveground and underground biomass. Research methods. The experiment scheme includes 3 options: 1 variant – 33 × 30 cm (990 cm2) – control; 2 variant – 33 × 45 cm (1485 cm2); 3 variant – 33 × 60 cm (1980 cm2). Results. It was found that an increase in the feeding area enhances the differentiation of plants in terms of the rate of passage of phenological phases. The earliest transition to the generative stage of development was noted in variants II and III (24.06). The maximum average daily gain was observed in the II and III decades of July, according to the variants it varied from 0.78 (1st stage) to 1.22 cm/day (III stage). The highest biological productivity was obtained in variant 3 with a feeding area of 33 × 60 cm; on average, it reached 251.5 g per plant, which is 162.2 g (181.6 %) higher than in the control. Scientific novelty. For the first time, there was studied, the influence of the feeding area on the most important aspects of the growth and development of Scutellaria baicalensis Georgi in the conditions of the Middle Urals. The optimal feeding area (1980 cm2) has been established, at which the Scutellaria baicalensis Georgi is able to form a fairly high productivity.

Spring phytoplankton blooms in the Northern Satsunan region, Japan, stimulated by the intrusion of Kuroshio Branch water

The Kuroshio current greatly affects biological processes in coastal areas. The Kagoshima Bay has good spawning ground for major migratory fish, serves as an important feeding area for fish larvae, and is affected by the Kuroshio current; however, there is little information concerning the biological response to the Kuroshio intrusion in this location. During the mixing period, the Kuroshio current approaches the Kagoshima Bay and a density flow, consisting of surface inflow and bottom outflow, is generated. We hypothesize that the bottom water in the bay, having a high nutrient concentration, mixes with the surface layer when the water flows out of the bay and that this contributes to the high biological production at the bay mouth. In this study, we conducted a field survey of the water quality in March 2016 and, using a three-end member mixing model, examined whether the bottom water of the bay could be a nutrient source supporting the phytoplankton bloom in the bay mouth. We discuss the fate of the organic matter derived from the primary production promoted by a nutrient supply event. The results indicate that the N-based phytoplankton biomass represented less than 80% of the N uptake by the phytoplankton, as estimated by subtracting the measured nitrate concentration from the supplied nitrate concentration based on the mixing model, indicating that the phytoplankton bloom at the bay mouth was supported by the supply of bottom water from the bay. Based on the C/N molar ratio (6.4) calculated by C/chlorophyll a (Chl-a) and N/Chl-a in this study, the highest value of nitrogen uptake was 12 mg C m−3 d−1 in terms of the carbon assimilation. The feeding rate of the mesozooplankton was estimated to be 13.6 mg C m−3 d−1 using a physiological model. An analysis of the food web structure is required to assess the effects of feeding by mesozooplankton; however, most of the phytoplankton bloom caused by mixing could be efficiently transferred to mesozooplankton in this study area.

Variability of Deep Water in Jordan Basin of the Gulf of Maine: Influence of Gulf Stream Warm Core Rings and the Nova Scotia Current

AbstractAs the nutrient‐rich subsurface slope water intruding into the deep basin of the Gulf of Maine (GoM) supports the high biological productivity in the semi‐enclosed gulf, it is important to understand the process and time scale of such slope water intrusion. This study focuses on variations of the GoM deep water on seasonal to interannual time scales and the influences of open ocean processes on the temporal variation of the deep water properties. Based on long‐term monitoring data, it is found that the deep water at Jordan Basin (one of three major basins in the GoM) is persistently warmer in winter than in summer, which is distinctly different from the seasonality of surface water in the basin and the deep water on neighboring shelf seas. The unique seasonality in the deep GoM reflects a time‐lagged response to shoreward intrusion of the subsurface slope water off the GoM. Both observation‐based lag‐correlation analyses and numerical simulations confirm a timescale of approximately 3 months for the intruding subsurface slope water to flow from Northeast Channel to Jordan Basin. Properties of the intruding slope water at the Northeast Channel were significantly correlated with the Gulf Stream position and dramatically impacted by episodic warm‐core rings shed from Gulf Stream. Inside the deep GoM, the intruding slope water was also indirectly affected by the fresher water input from Nova Scotia Current. Spreading of the fresher water inside the gulf strengthens near‐surface stratification, suppresses deep convection, and preserves heat and salt in the deep GoM during the wintertime.

Ecosystem health status and trophic modeling of an anthropogenically impacted small tropical estuary along India's west coast.

The tropical estuaries are characterized with high biological production and also impacted by anthropogenic activities. Describing these estuaries in terms of ecological data and trophic dynamics to reveal the ecological impacts is gaining attention recently. In this study, the ecological structure is analyzed for a heavily impacted small macrotidal tropical estuary, Ulhas river estuary (URE), situated near Mumbai megacity in the western coast of India, to delineate the impact of anthropogenic stressors on the ecosystem functioning. The URE is being exploited for sand and fisheries resources, and also faces risks from anthropogenic activities. The ecological data of URE were compiled for 2017-18 together with the most relevant literature estimates to construct an ecosystem model. A trophic organization in 20 functional groups was identified for URE using Ecopath modeling approach. The functional groups identified in the food web ranged from detritus and primary producers (trophic level (TL) = 1) to large pelagics (TL = 4.14). Detritivory: herbivory ratio (1.35) indicated that the detritus chain is dominant over the primary producer's chain. The total system throughput (TST) was estimated as 16 736.2 t km-2year-1. The indices such as net system production (NSP = 1 398.781 t km-2 year-1), total primary production/total biomass (TPP/TB = 25.17), biomass/total system throughput (TB/TST = 0.01), recycling index (Finn's Cycling Index = 13.94%), system omnivory index (0.3), relative ascendency (25.6%), and system overhead (74.4%) classified URE as an immature system. The eco-exergy index (30748.54 gm detritus equivalent m-2) showed that the ecosystem is a moderately stable and relatively less organized network. The estuarine fish community index (EFCI) yielded a value of 38 indicating the poor health status of the fish community in URE. The study delivers a comprehensive understanding of the ecosystem setting in URE and characterizes the prevailing condition. The ecological indicators analyzed here point towards a medium to a high level of impact in URE due to anthropogenic activities.