Areas Of High Productivity Research Articles

Peasant perception of beekeeping constraints and practices in large honey production areas in Burkina Faso

BackgroundIn recent decades, agricultural landscapes have been profoundly modified due to the intensification of agriculture, therefore leading to significant disturbances in all components of biodiversity. A survey on the knowledge of beekeeping realities and the use of phytosanitary products in areas of high honey production in Burkina Faso was carried out. Beekeeping realities design the state of beekeeping activities in the study localities.MethodsThe objective of this survey was to characterize Beekeeping operations and to assess the level of knowledge of beekeepers on the effects of the use of phytosanitary products through different beekeeping and agricultural practices. In this sense, 113 farmer beekeepers from the Boucle du Mouhoun, Hauts-Bassins and Nord regions in Burkina Faso were surveyed about their different beekeeping practices.ResultsThe results obtained indicated that beekeeping is a secondary activity (96.47%) and is mainly practiced by men (90.27%). The respondents have mostly an average of 22 traditional hives. The majority of beekeepers have not received training (84.07%) on the hazards of plant protection products on their beekeeping farms. However, a large amount of beekeepers (70.73%) acknowledged that the use of plant protection products could be harmful to their activity. Hives are usually installed in or near the fields. The plant protection products used for crop protection are herbicides (27%), insecticides (23%), fungicides (8%), but especially mixed (42%).ConclusionThe results show that beekeeping in Burkina Faso remains traditional and is practiced for sociocultural reasons. The use of pesticides close to beekeeping could play a role in bee colony collapse taking place in these regions. Training beekeepers on the dangers of the chemicals they use in fields near hives is therefore essential.

Impact of Spatial Variability in Zooplankton Grazing Rates on Carbon Export Flux

AbstractThe biological carbon pump is a key controller of how much carbon is stored within the global ocean. This pathway is influenced by food web interactions between zooplankton and their prey. In global biogeochemical models, Holling Type functional responses are frequently used to represent grazing interactions. How these responses are parameterized greatly influences biomass and subsequent carbon export estimates. The half‐saturation constant, or k value, is central to the Holling functional response. Empirical studies show k can vary over three orders of magnitude, however, this variation is poorly represented in global models. This study derives zooplankton grazing dynamics from remote sensing products of phytoplankton biomass, resulting in global distribution maps of the grazing parameter k. The impact of these spatially varying k values on model skill and carbon export flux estimates is then considered. This study finds large spatial variation in k values across the global ocean, with distinct distributions for micro‐ and mesozooplankton. High half‐saturation constants, which drive slower grazing, are generally associated with areas of high productivity. Grazing rate parameterization is found to be critical in reproducing satellite‐derived distributions of small phytoplankton biomass, highlighting the importance of top‐down drivers for this size class. Spatially varying grazing dynamics decrease mean total carbon export by >17% compared to globally homogeneous dynamics, with increases in fecal pellet export and decreases in export from algal aggregates. This study highlights the importance of grazing dynamics to both community structure and carbon export, with implications for modeling marine carbon sequestration under future climate scenarios.

Do rotations and intercrops matter? Opportunities for intensification and diversification of maize-based cropping systems in Zambia

ContextRealizing the double-edged goals of food security and crop diversification require knowledge of crop yield response to different agricultural practices and the extent to which such response is context dependent. This is particularly important in Southern Africa where cropping systems are dominated by maize and smallholders use few external inputs. ObjectiveThe objectives of this study were (1) to evaluate the performance of cropping systems with different levels of legume diversification and intensification on maize productivity across the main agroecological zones and farming systems of Zambia, and (2) to establish the minimum land required to reach maize self-sufficiency at household level with the different cropping systems tested. MethodsSix maize-based cropping systems, comprising maize monocropping, maize-legume rotations and intercrops under ‘conventional’ tillage and conservation agriculture, were evaluated across 40 farms in contrasting agro-ecological zones and farming systems of Zambia. A household survey was conducted in the same communities hosting the on-farm trials to quantify the share of households with enough maize cultivated area to benefit from the tested cropping systems. ResultsMaize yield measured in the on-farm trials ranged, on average, between 3.6 and 5.4 t ha−1, which was greater than mean maize yields reported by farmers not hosting on-farm trials during the same growing seasons and in the same sites. Our results showed a clear positive effect of legume rotation on maize yield in Eastern province only, where cropping systems including groundnut as rotation crop yielded between 1.0 and 2.0 t ha−1 more maize than other cropping systems. Pigeon pea intercrops and Gliricidia hedgerows, crop residue management, and tillage practice had no significant effect on maize yield in any of the provinces. Finally, nearly 35, 50, and 70% of surveyed farms in Northern, Eastern, and Southern province would have enough land to achieve the same level of maize production obtained on their farm with the yields, and associated area requirements, of the maize-legume rotations tested in the on-farm trials. ConclusionLegume rotations can increase maize productivity on land abundant farms in high potential maize production areas of Southern Africa, whereas legume intercrops have benefits at cropping systems level and should be targeted to land constrained farms. SignificanceThe study contributes to better understand the niche for diversified maize-based cropping systems with legume rotations and intercrops in Southern Africa, along with their impacts on maize productivity at the field level and their land requirements at the farm level.

How do soil and topographic drivers determine tree diameter spatial distribution in even aged cork oak stands installed in average to high productivity areas

Local terrain or microsite conditions influence the development of trees, particularly at early ages. These conditions might be described by edaphic or topographic variables. We mapped soil and topographic variables from four even-aged and even-spaced cork oak plantations located in two climatically distinct Portuguese regions. The major goal of this research was to understand the relation between soil and topographic fine-scale conditions and tree growth expressed by diameter without cork annual growth (idu). The methodology consisted in (1) analysing the spatial variability and autocorrelation of idu; (2) modelling idu with ordinary least squares (OLS) regressions; (3) comparing with spatial modelling of idu, incorporating spatial autocorrelation. The driest stands A and B, exhibited weaker spatial autocorrelation, distributed in smaller clusters (R2 < 0.03, OLS models), while stands C (R2 = 0.18, OLS models) and D (R2 = 0.11, OLS models) showed higher predictive capacity. Spatial models increased R2 scores, keeping most variables from OLS models and accounting for spatial autocorrelation. A + B + C + D OLS model obtained an R2 = 0.34 and respective spatial model R2 = 0.58. Apparent electrical conductivity at 0.5 (ECa0.5) and 1 m of soil depth, slope, elevation and topography position index were included as predictors (OLS), but only ECa0.5, slope and elevation were selected in the spatial model. Models were fitted using average to high productivity stands and should be used cautiously outside this range. Local terrain conditions determine the growth of young cork oak trees. Mapping soil and topographic variables before establishing new plantations may identify limiting microsite conditions where using cork oak species is not suitable due to low growth rates expectations.

Characterization of subsurface geology and hydrogeology in Kribi -Cameroon using electrical resistivity soundings and 3D-Implicit modelling: Baseline for groundwater resource management

This scientific article aims to characterize the geology and hydrogeology of Kribi, Cameroon for the purposes of water resources management, infrastructure development, and environmental protection. The specific objectives include mapping the subsurface electrical resistivity structure, identifying groundwater potential zones, and constructing a hydrogeological model for groundwater modelling. The study employed the Schlumberger method to map the electrical resistivity structure of the 3D subsurface and utilized 3D implicit modelling techniques to delineate groundwater potential zones. The study revealed that Kribi exhibits a highly complex geology, characterized by three-layered electrical resistivity models, typical of sedimentary and metamorphic formations. The major lithologies identified include laterite, clay, sand, quartz, and granite. The region encompasses areas with low water potential and brackish zones alongside high groundwater production areas. The study established the presence of aquifers within Kribi, with the unconfined aquifer found at depths ranging from 2 m to 13 m, and the confined aquifer extending from 14 m to 40 m. The aquifers are notably thick and productive, indicating substantial groundwater resources. Static groundwater volumes were estimated at 50,179,381 m3 and 317,118,946 m3 for the unconfined and confined aquifers respectively. Despite this potential, water resources management in the area is non-existent. The study recommends the implementation of Integrated Water Resources Management (IWRM) to improve water resource management, with a primary focus on groundwater modelling. The northern and southern regions of Kribi exhibit high permeability, which is advantageous for groundwater recharge and storage projects but also poses challenges for environmental remediation efforts. Consequently, safeguarding the delineated area for groundwater provision is of utmost importance.

Atlantic populations of a declining oceanic seabird have complex migrations and weak migratory connectivity to staging areas

Anthropogenic change is impacting ecosystems globally, causing declines in biodiversity. Long-distance migrants are particularly susceptible, as they depend on conditions over large geographical scales and are likely to experience a greater range of pressures. One long-distance migrant that has experienced substantial declines across the North-East Atlantic is the Arctic skua Stercorarius parasiticus. However, little is known about their migratory routes or strategies. We tracked 131 Arctic skuas from Scotland, the Faroe Islands, Norway and Svalbard between 2009 and 2019 using geolocators. To investigate migration strategies, we applied a hidden Markov model, using saltwater immersion data to infer stopovers and transit flights. Skuas used several discrete staging areas during migration, with an area of high marine productivity in the mid-North Atlantic being of high importance. Individuals from the different breeding populations overlapped extensively in staging areas, resulting in weak spatial connectivity between breeding and staging areas during southbound (rM = 0.25, 95% CI = 0.09-0.42; 0 = weak connectivity, 1 = strong connectivity) and northbound (rM = 0.16, 95% CI = -0.02 to 0.33) migration. Variation in migration strategies was driven by individuals from Svalbard, which belong to a population that is declining less than the other populations tracked. The relative location of wintering areas also influenced migration strategies. Individuals migrating further spent a smaller proportion of their migration at stopovers than those wintering closer. Identifying the non-breeding distribution, migration strategies and weak migratory connectivity of Arctic skuas provides a vital step towards linking conditions during migration to population dynamics and prioritising future research and conservation actions.

Heavy Metals Bioaccumulation in Mytilus galloprovincialis and Tapes decussatus from Faro Lake (Messina), Italy.

The aim of this study was to evaluate the potential bioaccumulation of arsenic (As), copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb) and mercury (Hg) in the haemolymph and corpus of Mytilus galloprovincialis and Tapes decussatus from Lake Faro. The lake is particularly prone to the accumulation of substances that are potentially toxic to aquatic organisms, due to the input of pollutants from urban and agricultural sources and the low rate of water exchange. The combination of saltwater from the Tyrrhenian Sea, the Strait of Messina and freshwater from hilly aquifers has created brackish conditions in the lake, resulting in an area of high commercial shellfish productivity. As, Cd, Cu, Pb and Zn were determined using a single quadrupole inductively coupled plasma mass spectrometer; Hg was determined using a direct mercury analyser (DMA-80). Physicochemical parameters of the water from Lake Faro were also performed. Statistical analysis was carried out using GraphPad Prism 9.0 (GraphPad Software, Inc., Boston, MA, USA) and Shapiro-Wilk normality was applied. Concentrations of Cd, Hg and Pb below the permitted MRLs in Mytilus galloprovincialis and Tapes decussatus used as ''biological indicators'' show that Lake Faro is not at risk of contamination by these pollutants and, moreover, is free of health problems for the consumer based on regulatory limits.

STATUS HARA N, P DAN K PADA TANAH SAWAH IRIGASI DI KAPANEWON PRAMBANAN, KABUPATEN SLEMAN, DAERAH ISTIMEWA YOGYAKARTA

The difference in the productivity level of paddy is caused by nutrient availability and land management. This study aims to determine the chemical properties of soil, especially elements of N, P, and K, in soils that have different levels of rice productivity. The methods used in this study are survey methods and laboratory analysis. Purposive sampling was conducted based on the productivity of medium and high-status rice fields. Based on the level of productivity of rice fields, there are 18 sample points, which are composite into 7 samples and analyzed in the laboratory. The results showed that several chemical properties in areas with high productivity levels had an average availability of total N nutrient status of 0.17% (low), potential P 56.5 mg 100 g-1 (high), potential K 17 mg 100 g-1 (low), organic C by 2.75% (medium), cation exchange capacity (CEC) 11.52 cmol(+)kg-1 (low) while in areas with medium productivity had an average total N nutrient of 0.23% (medium), potential P 38.33 mg 100 g-1 (medium), potential K 72 mg 100 g-1 (very high), organic C 3.23% (high), CEC 33.06 cmol(+)kg-1 (high) and has a soil pH of 6.1 (slightly acid) respectively. High-productivity areas have low to medium soil fertility, while medium-productivity areas have medium to high soil fertility. Rice field management factors are suspected to cause differences in rice productivity levels.

Methods of power consumption in conditions of high-productive areas of coal mines

The publication analyses the existing methods of estimated power consumption in relation to the conditions of high-productivity coal mine sites. In addition, a mathematical description of the model of predictive power consumption using the method of correlation and regression analysis is proposed and an algorithm for determining the parameters of specific power consumption in relation to the conditions of high-productivity coal mine sites is proposed. Key words: coal mine; high-performance section, technological equipment, specific power consumption; algorithm; mathematical forecast model of power consumption

Distribution characteristics and assessment of wind energy resources in the coastal areas of Guangdong

In order to improve the efficiency, availability and economy during construction and operation of wind farms, characteristic analysis and evaluation of the regional wind energies are key components. In this paper, wind energy resource evaluation was conducted for coastal areas of Guangdong, including spatial and seasonal characteristics and overall evaluation. Results indicate that: ① Effective wind speed frequency is the highest in the seaward area of the study area, followed by the excessive area and the lowest in the landward area. The seaward area is relatively suitable for wind energy development. ② Total theoretical exploitable area in the study area is 5.15×105 MW, and the high production area is mainly concentrated in the outer sea areas. Developable areas are in the nearshore areas, and the potential development areas are in the sea-land interface and estuary areas. Annual effective wind energy density values along the coast of eastern Guangdong are larger than that of western Guangdong. Its development potential is larger than that of western Guangdong. ③ Wind energy variation coefficient has significant seasonal differences. Wind energy density in winter and spring is more stable than that in summer and autumn. Additionally, overall seasonal variation index is smaller, which can provide stable wind energy.

Agronomic Performance and Grain Yield Stability of Elite Field Pea (Pisum Sativum L.) Genotypes Tested at Various Potential Growing Environments in Ethiopia

Field pea is a multipurpose crop. Despite its diverse benefits, its production and productivity in Ethiopia has remained low compared to its potential due to several biotic and abiotic constraints. Hence, this experiment was carried out with the objective to select best field pea genotypes in terms of yield potential, stability, pest resistance and other desirable agronomic traits for high potential production areas of the country. A total of 17 field pea genotypes including two standard checks, Burkitu and Bursa were arranged in a randomized complete block design with four replications over nine locations in 2019 and 2020 main cropping seasons. The computed analysis of variance showed highly significant differences (p &lt; 0.01) among the genotypes for all studied agronomic traits. One field pea genotype, GPHA-38 found better having 4 and 5%grain yield advantage over the two checks, Bursa and Burkitu, respectively. Additionally, GPHA-38 had comparable performance on the other agronomic traits with standard checks. Moreover, this genotype was found stable in grain yield among the test entries based on GGE biplot stability analysis. However, this genotype may not fulfill the criteria to present as candidate for variety verification trial due to low grain yield advantage and other agronomic traits compared with the checks. Therefore, considering its consistent performance and relatively better yielding capacity, the line GPHA-38 can alternatively be used as a trait donor parent in the pre-breeding programs.

Flow loss mechanism of a novel co-rotating scroll hydrogen recirculation pump for fuel cell systems

The hydrogen recirculation pump is a key component of fuel cell systems. The aerodynamic performance of a novel co-rotating scroll hydrogen recirculation pump with the array scroll structure was investigated in this study. The performance differences between the co-rotating and orbiting scroll pumps were obtained via computational fluid dynamics approach. The flow loss mechanism of the co-rotating scroll pump was revealed by the entropy production analysis and omega vortex identification. The results show that compared with the orbiting scroll pump, the co-rotating one has a better over-compression consistency between adjacent working chambers, and a higher isentropic efficiency with a lower direct dissipation entropy production. Main flow losses of co-rotating scroll pump originate from the turbulent and direct dissipations in scroll chambers, and mainly occur in the discharge process. The large-scale omega vortices flow is responsible for the pump flow losses. The strengthened large-scale omega vortex expands the area of high entropy production in central discharge region. The suction flow losses increase due to the strengthened suction flow separations. The total area of omega vortex in the surrounding and central regions contrarily change with the pump isentropic efficiency. The smallest area of omega vortex represents the minimum flow loss of the co-rotating scroll pump at 7500 r·min−1.

Predicting population size at large scale: The case of two large felids

Approaches that allow capitalizing on local population estimates to derive global population estimates with associated uncertainty are urgently needed, especially for naturally rare species of conservation concern. Here we used published population density estimates to predict large-scale density patterns and derive global population estimates for two species of large felids, the leopard and the tiger. We modelled population density for the leopard (n = 392) and the tiger (n = 547) as a function of environmental and anthropogenic variables, while controlling for differences in sampling method and sampling area, time of data collection, spatial autocorrelation, subspecies and political protection. We used Bayesian inference to generate a distribution of plausible population sizes. Both species showed higher densities in high productivity areas, the leopard being more abundant in high precipitation, high level of terrain roughness and agricultural areas, and the tiger in areas with low croplands and low roughness. Primary roads density showed a negative effect on both species. Secondary roads density was associated to higher densities for the leopard but lower densities for the tiger. Livestock biomass showed a humped relationship with tigers’ densities. Temporal trends in average density were negative for the tiger, experiencing an average decline of 34% (IQR: 11% − 53%). In contrast, the trend for leopards showed a marginal, yet uncertain, increase in recent years 21% (IQR: −5% − 57%). We predicted a global population estimate of 261,636 (IQR = 146,768 − 461,512) and 5201 tigers (IQR = 2596 − 10,460). Large-scale models of population density that rely on unstructured data can contribute to our understanding of species ecology, produce robust population size estimates for conservation assessment and inform large-scale conservation planning. At the same time, the uncertainty around these estimates highlights the limited knowledge available for these species which should be accounted for in conservation assessments.

A cabled ocean acoustic array to be installed in the Gulf of Maine

It is often noted that we know more about the planets than the processes of our oceans. A network of ocean observatories is improving our knowledge; however, measurements are still relatively scarce and do not provide enough data to validate and refine models of ocean currents, soundscapes, and biological activity. A cabled acoustic array is being developed for deployment in 2024 in the coastal waters of the Gulf of Maine to complement existing oceanographic monitoring infrastructure. The system will make measurements of the nearshore (6 km) environment and shed light on the connections between coastal measurements and the overall Gulf of Maine environment. The system is designed to synoptically collect acoustic, oceanographic, and biogeochemical data, while also remaining flexible enough in design to incorporate new sensors in the future. Measurements made with this ocean asset will serve as a baseline for pattern and trend analyses of changing environmental conditions in an area of high productivity, human use, and species diversity. The data management and visualization team are developing an infrastructure to provide public access to the data and its products. Public data access will permit researchers at all levels to advance our understanding of ocean acoustics and oceanographic processes.

Model-based scenarios for achieving net negative emissions in the food system

Most climate mitigation scenarios point to a combination of GHG emission reductions and CO2removal for avoiding the most dangerous climate change impacts this century. The global food system is responsible for ~1/3 of GHG emissions and thus plays an important role in reaching emission targets. Consumers, technology innovation, industry, and agricultural practices offer various degrees of opportunity to reduce emissions and remove CO2. However, a question remains as to whether food system transformation can achieve net negative emissions (i.e., where GHG sinks exceed sources sector wide) and what the capacity of the different levers may be. We use a global food system model to explore the influence of consumer choice, climate-smart agro-industrial technologies, and food waste reductions for achieving net negative emissions for the year 2050. We analyze an array of scenarios under the conditions of full yield gap closures and caloric demands in a world with 10 billion people. Our results reveal a high-end capacity of 33 gigatonnes of net negative emissions per annum via complete food system transformation, which assumes full global deployment of behavioral-, management- and technology-based interventions. The most promising technologies for achieving net negative emissions include hydrogen-powered fertilizer production, livestock feeds, organic and inorganic soil amendments, agroforestry, and sustainable seafood harvesting practices. On the consumer side, adopting flexitarian diets cannot achieve full decarbonization of the food system but has the potential to increase the magnitude of net negative emissions when combined with technology scale-up. GHG reductions ascribed to a mixture of technology deployment and dietary shifts emerge for many different countries, with areas of high ruminant production and non-intensive agricultural systems showing the greatest per capita benefits. This analysis highlights potential for future food systems to achieve net negative emissions using multifaceted “cradle-to-grave” and “land-to-sea” emission reduction strategies that embrace emerging climate-smart agro-industrial technologies.

At-sea distribution patterns of the Peruvian diving petrel Pelecanoides garnotii during breeding and non-breeding seasons

At-sea distributions of seabird species are strongly associated with the distribution patterns of their prey, which are influenced by physical oceanic features. During breeding and non-breeding seasons, seabirds move extraordinary distances among different environments. However, foraging site fidelity by seabirds appears to be high in areas of known high productivity, such as frontal zones and upwellings. Here, we present a tracking study for the Peruvian diving-petrel Pelecanoides garnotii, an endemic seabird of the highly productive Humboldt Current System, to assess whether adults use the same foraging areas throughout the year, combining data from nest monitoring and global location sensors (GLS) deployed on 12 individuals between two breeding seasons (2013–2014 and 2014–2015), in Choros Island (29°15′S; 71°32′W), Chile. Two main foraging areas were registered. During the breeding season, adults moved in the northern direction, between 60 to 144 km away from their colony, foraging in areas with high primary productivity. During the non-breeding period, they moved to southern latitudes (~ 1200 km). Adults spent 37% and 63% of their time in flight/land and on/underwater activities, respectively. We determined that birds move northward from their colony during breeding, where prey availability seems more predictable throughout the year. However, during the non-breeding period, it is likely that other environmental factors influence the distribution pattern of the Peruvian diving-petrel.

Can seaweeds feed the world? Modelling world offshore seaweed production potential

Pressure on the terrestrial ecosystems is large and big concerns exist regarding whether a growing world population can be fed from the land. Little is known about if and how much these concerns could be alleviated by harvesting more from the oceans. We modelled the biophysical production potential of seaweeds, and their current and possible future contribution to world food supply. We estimate seaweeds currently provide up to 0.13% of global food energy supply. Seaweed production is increasing more rapidly than terrestrial production. At current rates of increase we estimate seaweed energy contribution of 0.25% in 2050. Production potential of seaweeds could contribute up to 2 to 14% of global food supply if farming 1% of the modelled suitable space within the Exclusive Economic Zone. We show this large potential contribution to world food supply will only be achieved with unprecedented increases in seaweed production, while offshore seaweed cultivation is still in its infancy. The study shows large uncertainties that warrant further research. Modelling shows vast areas of world oceans are unsuitable because of being too far out of shore, having too low nutrient concentrations or having too high waves. Only 2–9% of world oceans and 6–25% of the Exclusive Economic Zone (EEZ) was shown to be suitable for seaweed production. Identifying suitable sites for offshore seaweed cultivation is therefore important. Site suitability maps reported for the 3 model species can be useful for private companies and policy makers expanding seaweed in new high potential production areas around the world.

Microplastics in the Arctic: a transect through the Barents Sea

Globally, the abundance of microplastics in our oceans is increasing, including within the remote locations of the polar regions. The Barents Sea, which adjoins the Arctic Ocean, is an area of high primary productivity that, owing to the convergence of regional currents, has been mooted as a potential sixth ocean gyre that may coalesce high concentrations of plastic debris. This study aimed to explore data collected from large volume samples of sub-surface water collected from transects through the Barents Sea to quantify and characterise microplastics in this region, with a focus on potential impacts to zooplankton. Overall, the mean microplastic abundance in the Barents Sea was 0.011 microplastics m-3 (range: 0.007 – 0.015 m-3). Microplastics were found in higher abundances nearer land mass at the southern end of the transect and northwards towards the ice edge, recording 0.015 microplastics m-3 during both transect legs. Microplastics were predominantly fibrous (92.1%) and typically blue (79%) or red (17%) in colour. A range of polymers were identified including polyester (3.8%), copolymer blends (2.7%), elastomers (7.1%) and acrylics (10.6%), however semi-synthetic polymers dominated, comprising 74.4% of particles found. Higher microplastic concentrations in the northernmost transect may stem from melting sea-ice, while the higher concentrations in the southernmost transect likely derive from the long-range transport of microplastics via currents from Europe.

Seasonal and interannual variability of the pelagic ecosystem and of the organic carbon budget in the Rhodes Gyre (eastern Mediterranean): influence of winter mixing

Abstract. The Rhodes Gyre is a cyclonic persistent feature of the general circulation of the Levantine Basin in the eastern Mediterranean Sea. Although it is located in the most oligotrophic basin of the Mediterranean Sea, it is a relatively high primary production area due to strong winter nutrient supply associated with the formation of Levantine Intermediate Water. In this study, a 3D coupled hydrodynamic–biogeochemical model (SYMPHONIE/Eco3M-S) was used to characterize the seasonal and interannual variability of the Rhodes Gyre's ecosystem and to estimate an annual organic carbon budget over the 2013–2020 period. Comparisons of model outputs with satellite data and compiled in situ data from cruises and Biogeochemical-Argo floats revealed the ability of the model to reconstruct the main seasonal and spatial biogeochemical dynamics of the Levantine Basin. The model results indicated that during the winter mixing period, phytoplankton first progressively grow sustained by nutrient supply. Then, short episodes of convection driven by heat loss and wind events, favoring nutrient injections, organic carbon export, and inducing light limitation on primary production, alternate with short episodes of phytoplankton growth. The estimate of the annual organic carbon budget indicated that the Rhodes Gyre is an autotrophic area, with a positive net community production in the upper layer (0–150 m) amounting to 31.2 ± 6.9 gCm-2yr-1. Net community production in the upper layer is almost balanced over the 7-year period by physical transfers, (1) via downward export (16.8 ± 6.2 gCm-2yr-1) and (2) through lateral transport towards the surrounding regions (14.1 ± 2.1 gCm-2yr-1). The intermediate layer (150–400 m) also appears to be a source of organic carbon for the surrounding Levantine Sea (7.5 ± 2.8 gCm-2yr-1) mostly through the subduction of Levantine Intermediate Water following winter mixing. The Rhodes Gyre shows high interannual variability with enhanced primary production, net community production, and exports during years marked by intense heat losses and deep mixed layers. However, annual primary production appears to be only partially driven by winter vertical mixing. Based on our results, we can speculate that future increase of temperature and stratification could strongly impact the carbon fluxes in this region.

Modelling the effect of the tidal cycle on the high phytoplankton biomass area of Cape Trafalgar (SW Iberian Peninsula)

Physical–biological interactions in the ocean are known to be crucial for understanding ecosystem processes. This is particularly relevant in the highly dynamic coastal regions, where the biogeochemical processes associated with higher-frequency perturbations such as tidal waves play a key role in primary production. In this study, we examine the influence of the tide-topography interaction on the high productivity area of Cape Trafalgar (NW limit of the Strait of Gibraltar, Iberian Peninsula) using a high-resolution ocean circulation model coupled to an ecosystem model. The obtained results highlight the relevance of the tidal cycle explaining the high phytoplankton biomass that characterises this region through an active and periodic forcing, resulting in a pulsating upwelling system. Our model shows that the interaction of the westward zonal component of the tidal current (uvel) with the submarine ridge (i.e., Barbate High) that characterises this region, which is perpendicular to the coast, results in the pumping of deep, cold, salty, and nutrient-rich waters to the well-illuminated subsurface waters, fuelling phytoplankton growth. At the same time, the interaction of the westward tidal current with the ridge leads to the development of a cyclonic eddy, which enables the redistribution of the upwelled waters over and to the east of Barbate High. The fortnightly tidal period has been identified as the most influential because (an effective) tidal-pumping process only takes place when the westward uvel is ∼ 0.42 m s−1, a condition attained between ∼ 3 days before and after the moment of maximum tidal flow during spring tides. Simultaneously, the energy and the associated horizontal and vertical mixing of the cyclonic gyre also vary with the tidal cycle, being stronger during spring tides. Both tidally driven processes, i.e., the cyclical upslope advection of deep nutrient-rich water and the influence of the cyclonic gyre, are the main mechanisms that lead to the development of a persistent phytoplankton-rich tongue over Barbate High. Consequently, Cape Trafalgar acts as a source of nutrient- and phytoplankton-rich waters to the surrounding waters.