Canary Current Upwelling System Research Articles

Long-term trends of pH, alkalinity, and hydrogen ion concentration in an upwelling-dominated coastal ecosystem: Ría de Vigo, NW Spain

The present study focuses on the Ría de Vigo (NW Spain), a coastal embayment influenced by the Canary Current Upwelling System, which is among the world’s significant Eastern Boundary Upwelling Ecosystems. The research assesses historical changes in the marine carbonate system by generating 25-year weekly time series at six stations . Assessing ocean acidification in the region is complex due to diverse factors influencing coastal carbon dynamics, making predictions more challenging. To capture the specific dynamics in Ría de Vigo, ensembles of Neural Networks were applied. These networks were trained with a data set obtained in several oceanographic cruises, in order to retrieve pH, hydrogen ion concentration and alkalinity, achieving a root mean square error of 0.0272 pH units, 0.588 nmol kg-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {kg}^{-1}$$\\end{document}, and 10.6 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}mol kg-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {kg}^{-1}$$\\end{document}, respectively. Subsequently, time series of the selected variables were generated, applying data of predictors measured at the aforementioned stations . An increase in normalized alkalinity was observed for all stations, except in the surface layer at the innermost location. A decrease in pH and an increase in hydrogen ion concentration were observed for all points, with trends that exceed reported rates of ocean acidification in the open ocean.

Climate change in the Canary/Iberia upwelling region: the role of ocean stratification and wind

The Canary/Iberia region (CIR), part of the Canary Current Upwelling System, is well-known for its coastal productivity and crucial role in enriching the oligotrophic open ocean through the offshore transport of the upwelled coastal waters. Given its significant ecological and socio-economic importance, it is essential to assess the impact of climate change on this area. Therefore, the goal of this study is to analyze the climate change signal over the CIR using a high-resolution regional climate system model driven by the Earth system model MPI-ESM-LR under RCP8.5 scenario. This modelling system presents a regional atmosphere model coupled to a global ocean model with enough horizontal resolution at CIR to examine the role of the upwelling favourable winds and the ocean stratification as key factors in the future changes. CIR exhibits significant latitudinal and seasonal variability in response to climate change under RCP8.5 scenario, where ocean stratification and wind patterns will play both complementary and competitive roles. Ocean stratification will increase from the Strait of Gibraltar to Cape Juby by the end of the century, weakening the coastal upwelling all year long. This increase in stratification is associated with a freshening of the surface layers of the North Atlantic. However, modifications in the wind pattern will play a primary role in upwelling source water depth changes in the southernmost region of the CIR in winter and in the north of the Iberian Peninsula in summer. Wind pattern changes are related to the intensification of the Azores High in winter and to a deepening of the Iberian thermal low in summer months.

The zoogeographic regionalization for cephalopoda linked to the canary current upwelling system

Quantitative data on cephalopods collected in ten multidisciplinary surveys (20–2000 m) between 2004 and 2012, together with original oceanographic and satellite data, were analyzed using multivariate techniques. Statistical analyses were based on presence–absence matrices by species and hydrological variable indices. The results show that cephalopods are distributed in two main zoogeographical groups separated by latitude: “Temperate water” and “Tropical water” clusters. They extended by temperate and tropical regions, separated by a geographical boundary, Cape Blanc, particularly strong in the case of coastal species between these groups. For the total fauna, we have identified a third particular cephalopods’ cluster, the “Upwelling” cluster (22°–17°N), characterized by a higher diversity and dominance of oceanic cephalopods. This is proposed as a new zoogeographical region that would coincide with the area of greatest productivity, intensity and permanence throughout the year of the canary current upwelling, confined between the north of Cape Blanc and the south of Mauritania. The results confirm the strong relationship between the three zoogeographical regions (temperate, tropical, and upwelling) and certain water bodies that characterize the regional hydrology. This paper deepens into the zoogeography of the cephalopods from Northwest Africa (Central-Eastern Atlantic), providing a new, more detailed insight into the region and its boundaries in relation to the oceanography.

Baseline Climatology of the Canary Current Upwelling System and Evolution of Sea Surface Temperature

Global climate change has induced a rise in sea surface temperature (SST), although this increase is not uniform across the world. Significant variations exist between coastal and offshore waters, particularly in regions affected by upwelling processes. This study focuses on the Canary Current Upwelling System (CCUS), stretching from Northwest Iberia to Northwest Africa. High-resolution remotely sensed SST data (0.05°) from the ODYSSEA Level 4 Sea Surface Temperature Reprocessed dataset were validated with in situ measurements and employed to establish a regional climatological baseline for 1982–2012. Subsequent years were compared to this baseline to construct SST anomaly maps, revealing SST changes since 2012. The study area was further divided into sub-regions for comparative analysis. Results indicate that SST consistently increased at a higher rate offshore compared to the adjacent nearshore regions. A reference dataset spanning 1951–1981 was used to gauge SST variability between the two baselines. SST exhibited a 0.59 °C increase from 1951–1981 to 1982–2012, with a slowing of SST trends beyond the 1982–2012 baseline. This research offers valuable insights into the climatological dynamics of the CCUS. These findings enhance our understanding of this critical coastal system’s climatology, laying the groundwork for future investigations into evolving climate patterns in coastal regions.

Red tides in the Galician rías: historical overview, ecological impact, and future monitoring strategies.

The Galician rías (NW Iberia, Spain) are coastal embayments at the northern boundary of the Canary Current upwelling system. Their favourable conditions for phytoplankton growth turn them into a suitable area for the development of aquaculture activities and a site of most of the national shellfish production. Phytoplankton blooms, a natural phenomenon inside the rías, under certain conditions eventually lead to seawater discolourations (colloquially known as "red tides"). Because of their transient nature, available records derive mainly from opportunistic samplings or casual observations, and are scattered in the literature. As a rule of thumb, red tides in the NW Iberian Peninsula are of non-toxic nature and are not systematically monitored. However, in recent years striking exceptions such as those of the toxic dinoflagellate Alexandrium minutum, a producer of paralytic shellfish toxins, have been registered. The present study goes through a historical overview of red tides in the Galician rías, describing their colouring, responsible organisms, seasonal and geographical occurrence, and their association with other features (harmful algal blooms, biotoxins and shellfish harvesting closures, bioluminescence, etc.), ending with social challenges and proposals for improving the monitoring of red tides in the future.

Seasonality of coastal upwelling trends in the Mauritania-Senegalese region under RCP8.5 climate change scenario

The Mauritania-Senegalese upwelling region (MSUR), the southernmost region of the Canary current upwelling system, is well-known for its coastal productivity and the key role it plays in enriching the oligotrophic open ocean through the offshore transport of the upwelled coastal waters. The great ecological and socio-economic importance makes it necessary to evaluate the impact of climate change on this region. Hence, our main objective is to examine the climate change signal over the MSUR with a high resolution regional climate system model (RCSM) forced by the Earth system model MPI-ESM-LR under RCP8.5 scenario. This RCSM has a regional atmosphere model (REMO) coupled to a global ocean model (MPIOM) with high-resolution in the MSUR, which allows us to evaluate the wind pattern, the ocean stratification, as well as the upwelling source water depth, while maintaining an ocean global domain. Under RCP8.5 scenario, our results show that the upwelling favourable winds of the northern MSUR are year-round intensified, while the southern MSUR presents a strengthening in winter and a weakening in March–April. Along with changes in the wind pattern, we found increased ocean stratification in the spring months. In those months southern MSUR presents a shallowing of the upwelling source water depth associated to changes in both mechanisms. However, in winter the whole MSUR shows a deepening of the upwelling source water depth due to the intensification of the upwelling favourable winds, with the increased ocean stratification playing a secondary role. Our results demonstrate the need to evaluate the future evolution of coastal upwelling systems taking into account their latitudinal and seasonal variability and the joint contribution of both mechanisms.

Core–shell clustering approach for detection and analysis of coastal upwelling

A comprehensive approach is presented to analyze season’s coastal upwelling represented by weekly sea surface temperature (SST) image grids. The proposed model, core–shell clustering, assumes that the season’s upwelling can be divided into shorter periods of stability, time ranges, consisting of constant core and variable shell parts. A one-by-one core–shell clustering algorithm is provided. The algorithm parameters are automatically derived from the least-squares clustering criterion.The approach applies to SST gridded data for sixteen successive years (2004–2019) of coastal upwelling in the western Iberian coast, the northernmost branch of the Canary Current Upwelling System. Our results show that at each season, there are 3 to 5 time intervals, the ranges, at which the upwelling presents stable core patterns of relatively cold water surrounded by somewhat larger shell areas of warmer waters. Based on other experimental computations performed by our team, we conclude that this pattern is not just a purely local phenomenon but has a more global meaning. Inter-annual time series analysis are consistent among themselves and with existing expert domain knowledge.

Temperature and salinity trends in the northern limit of the Canary Current Upwelling System

Thermohaline time series are crucial for detecting and quantifying abiotic changes in the marine environment, and even more so in the present global change scenario. This is particularly relevant for the Ría the Vigo and its adjacent shelf, a highly productive ecosystem at the northern limit of the Canary Current Upwelling System (CanCUS). This study analyses a 34-year time series (1987–2020) of Conductivity-Temperature-Depth (CTD) casts, the longest series available to date in the region. Long-term trends, shifts, and seasonal variability of temperature and salinity were assessed and investigated in relation to regional meteorological variability and basin-scale atmospheric teleconnection indices. Generalized Additive Models (GAM) allowed us to determine that monthly thermohaline variability can be largely explained by regional meteo-climatic variability, mainly upwelling index and river discharge. Trends and shifts in some teleconnection patterns, especially the East Atlantic (EA) pattern, may also be related to both the shift in salinity in 2013 and its long-term decrease below 50 m depth. Despite the current global warming context, no statistically significant trend was observed for either the upwelling index or temperature. The spatial analysis of sea surface temperature trends suggests that our study area has been responding to climate change differently from other surrounding near-shore areas, as the Finisterre Cape or the southern Bay of Biscay. Overall, this study highlights the importance of long-term observations to elucidate the impact of climate change in the northern limit of the CanCUS and encourages caution when extrapolating conclusions from ecosystem studies on a regional scale.

The signature of NAO and EA climate patterns on the vertical structure of the Canary Current upwelling system

Abstract. The current study aims to analyse the vertical structure of the ocean during upwelling events using in situ and modelled data. Additionally, the influence of climate patterns, namely the North Atlantic Oscillation (NAO) and the East Atlantic (EA) pattern, on the vertical structure and their impact on the upwelling activity are assessed for a period of 25 years (1993–2017). The study focuses on the central part of the Canary Current (25–35∘ N) with persistent upwelling throughout the year, with an annual cycle and the strongest events from June to September. Upwelling is determined using two different approaches: one index is calculated based on temperature differences between the coastal and the offshore area, and the other is calculated based on wind data and the resulting Ekman transport. Different datasets were chosen according to the indices. Stable coastal upwelling can be observed in the study area for the analysed time span, with differences throughout the latitudes. A deepening of the isothermal layer depth and a cooling of temperatures are observed in the vertical structure of coastal waters, representing a deeper mixing of the ocean and the rise of cooler, denser water towards the surface. During years of a positive NAO, corresponding to a strengthening of the Azores High and the Icelandic Low, stronger winds lead to an intensification of the upwelling activity, an enhanced mixing of the upper ocean, and a deeper (shallower) isothermal layer along the coast (offshore). The opposite is observed in years of negative NAO. Both effects are enhanced in years with a coupled, opposite phase of the EA pattern and are mainly visible during winter months, where the effect of both indices is the greatest. The study therefore suggests that upwelling activities are stronger in winters of positive North Atlantic Oscillation coupled with a negative East Atlantic pattern and emphasizes the importance of interactions between the climate patterns and upwelling.

Linking Phytoplankton Variability to Atmospheric Blocking in an Eastern Boundary Upwelling System

AbstractThe oceanic ecosystems in the eastern boundary upwelling systems (EBUS) are expected to be influenced by climate change, but specific mechanisms describing their connections are not well understood. Using a 20‐year time‐series record of satellite and climate data, we identified a strong linkage between phytoplankton variability in a EBUS and a high latitude, large‐scale atmospheric process. The winter–spring phytoplankton variability in the Canary Current Upwelling System was associated to the atmospheric blocking events over Greenland. These Greenland blocking events were primarily caused by the persistence of quasi‐stationary, large‐scale high atmosphere pressure fields. These fields forced the eddy‐driven jet stream to shift south, which caused a weakening of the equatorward alongshore winds over the upwelling system. As a result, the wind‐driven upwelling was suppressed, and phytoplankton growth was inhibited. These results identified a previously unknown source driving interannual phytoplankton variability in the EBUS, underscoring the importance of contributions of atmospheric connections on the coastal upwelling ecosystems.

Nutrient limitation can explain a rapid transition to synchrony in an upwelling‐driven diatom community

AbstractIdentifying the mechanisms controlling the temporal dynamics of ecological communities is key to understand their vulnerability to natural and anthropogenic impacts and to identify early warnings of critical transitions. At community level, inter‐specific synchrony is an important indicator of ecosystem stability and variation in function. Using wavelet analysis on time‐series of abundance of 12 dominant diatom species, sampled monthly (1994‐2009) in a coastal upwelling embayment at the northern limit of the Canary Current Upwelling System, we find a sudden onset of synchrony between 1998 and 2002, concomitant with an increase in the amplitude of the upwelling index at different temporal scales. To better understand the underlying mechanism that could generate this sudden onset of synchrony among competitors, we analyzed a general model of competition between two species for two essential nutrients (e.g., nitrogen and silicate). We incorporate environmental variation by varying the concentration of one of the essential nutrients entering the system. Increase in the amplitude of environmental variation always leads to greater synchrony among competitors. This occurs because the system shifts from a state in which species are limited by different nutrients to one where species are often limited by the same nutrient. We show that the transition from asynchronous to synchronous dynamics can occur suddenly as the amplitude of environmental variation increases. While it is not possible to rule out alternative mechanisms, our model demonstrates that sudden changes in the extent of synchronization should be a common feature when species compete for essential nutrients in variable environments.

The Canary Intermediate Poleward Undercurrent: Not Another Poleward Undercurrent in an Eastern Boundary Upwelling System

AbstractPoleward undercurrents are well-known features in eastern boundary upwelling systems. In the California Current upwelling system, the California poleward undercurrent has been widely studied, and it has been demonstrated that it transports nutrients from the equatorial waters to the northern limit of the subtropical gyre. However, in the Canary Current upwelling system, the Canary intermediate poleward undercurrent (CiPU) has not been properly characterized, despite recent studies arguing that the dynamics of the eastern Atlantic Ocean play an important role in the Atlantic meridional overturning circulation, specifically on its seasonal cycle. Here, we use trajectories of Argo floats and model simulations to characterize the CiPU, including its seasonal variability and its driving mechanism. The Argo observations show that the CiPU flows from 26°N, near Cape Bojador, to approximately 45°N, near Cape Finisterre and flows deeper than any poleward undercurrent in other eastern boundaries, with a core at a mean depth of around 1000 dbar. Model simulations manifest that the CiPU is driven by the meridional alongshore pressure gradient due to general ocean circulation and, contrary to what is observed in the other eastern boundaries, is still present at 1000 dbar as a result of the pressure gradient between the Antarctic Intermediate Waters in the south and Mediterranean Outflow waters in the north. The high seasonal variability of the CiPU, with its maximum strength in autumn and minimum in spring, is due to the poleward extension of AAIW, forced by Ekman pumping in the tropics.

Assessment of the Canary current upwelling system in a regionally coupled climate model

The Canary current upwelling is one of the major eastern boundary coastal upwelling systems in the world, bearing a high productive ecosystem and commercially important fisheries. The Canary current upwelling system (CCUS) has a large latitudinal extension, usually divided into upwelling zones with different characteristics. Eddies, filaments and other mesoscale processes are known to have an impact in the upwelling productivity, thus for a proper representation of the CCUS and high horizontal resolution are required. Here we assess the CCUS present climate in the atmosphere–ocean regionally coupled model. The regional coupled model presents a global oceanic component with increased horizontal resolution along the northwestern African coast, and its performance over the CCUS is assessed against relevant reanalysis data sets and compared with an ensemble of global climate models (GCMs) and an ensemble of atmosphere-only regional climate models (RCMs) in order to assess the role of the horizontal resolution. The coupled system reproduces the larger scale pattern of the CCUS and its latitudinal and seasonal variability over the coastal band, improving the GCMs outputs. Moreover, it shows a performance comparable to the ensemble of RCMs in representing the coastal wind stress and near-surface air temperature fields, showing the impact of the higher resolution and coupling for CCUS climate modelling. The model is able of properly reproducing mesoscale structures, being able to simulate the upwelling filaments events off Cape Ghir, which are not well represented in most of GCMs. Our results stress the ability of the regionally coupled model to reproduce the larger scale as well as mesoscale processes over the CCUS, opening the possibility to evaluate the climate change signal there with increased confidence.

A Shift in the Wind Regime of the Southern End of the Canary Upwelling System at the Turn of the 20th Century

AbstractIn this study, we make use of historical wind direction observations to assemble an instrumental upwelling index (DUI) at the southern end of the Canary Current Upwelling System. The DUI covers the period between 1825 and 2014 and, unlike other upwelling indices, it does not rely neither in wind speed nor in reanalyzed data. In this sense, the DUI can be regarded as an instrumental index. Additionally, it avoids the suspected bias toward increasing wind speed of historical wind observations documented in previous research. Our results indicate that the frequency of the alongshore winds at the west coast of Africa between 10°N and 20°N measured by the DUI is significantly related with the wind stress and therefore the upwelling intensity in this region. The DUI presents a significant variability both at interannual and decadal timescales. We have not found any significant trend for the 20th century. However, when the entire length of the series is considered, a large shift toward more frequent alongshore winds is evidenced as a result of several decade‐long fluctuations which took place between the late 19th century and the beginning of the 20th century. This fact would imply that a significant change in the upwelling intensity at the southern end of the Canary Current Upwelling System should have occurred at the turn of the 20th century.

El Niño as a predictor of round sardinella distribution along the northwest African coast

The El Niño Southern Oscillation (ENSO) produces global marine environment conditions that can cause changes in abundance and distribution of distant fish populations worldwide. Understanding mechanisms acting locally on fish population dynamics is crucial to develop forecast skill useful for fisheries management. The present work addresses the role played by ENSO on the round sardinella population biomass and distribution in the central-southern portion of the Canary Current Upwelling System (CCUS). A combined physical-biogeochemical framework is used to understand the climate influence on the hydrodynamical conditions in the study area. Then, an evolutionary individual-based model is used to simulate the round sardinella spatio-temporal biomass variability. According to model experiments, anomalous oceanographic conditions forced by El Niño along the African coast cause anomalies in the latitudinal migration pattern of the species. A robust anomalous increase and decrease of the simulated round sardinella biomass is identified in winter off the Cape Blanc and the Saharan coast region, respectively, in response to El Niño variations. The resultant anomalous pattern is an alteration of the normal migration between the Saharan and the Mauritanian waters. It is primarily explained by the modulating role that El Niño exerts on the currents off Cape Blanc, modifying therefore the normal migration of round sardinella in the search of acceptable temperature conditions. This climate signature can be potentially predicted up to six months in advance based on El Niño conditions in the Pacific.

The Medieval Climate Anomaly in the Mediterranean Region

AbstractThe Medieval Climate Anomaly (MCA) is a preindustrial phase of pronounced natural climate variability with a core period from 1000 to 1200 CE. The paper presents a synthesis that integrates palaeotemperature records from the Greater Mediterranean Region encompassing the past 1,500 years based on multiproxy data from 79 published land and marine sites. MCA warming dominated the Western Mediterranean (Iberia, NW Africa) as well as the northern land areas of the Central and Eastern Mediterranean region. MCA cooling prevailed in the Canary Current Upwelling System, southern Levant, and some sea areas of the Central and Eastern Mediterranean. Previous palaeoreconstructions suggest persistent positive Atlantic Multidecadal Oscillation (AMO+) and North Atlantic Oscillation (NAO+) conditions during the MCA, while the Little Ice Age was dominated by an AMO− and NAO− regime. During the past 150 years, AMO+ conditions are typically associated with warming episodes in the Mediterranean area. A similar relationship appears to have also been established during the MCA as the majority of all Mediterranean land sites experienced warm climate conditions. In contrast, the NAO typically leads to a characteristic west‐east temperature dipole pattern in the basin, as documented for the last decades. During NAO+ conditions the Western Mediterranean is generally warm (and dry), while large parts of the Central and Eastern Mediterranean are cold. Similar trends seem to have been developed during the MCA when the NAO+ regime led to consistent warming in the Western Mediterranean, while a significant number of sites with MCA cooling existed in the Central and Eastern Mediterranean.

Regional climate, primary productivity and fish biomass drive growth variation and population resilience in a small pelagic fish

Abstract Environmental change often combined with selective harvesting has profound and diverse impacts on marine fish populations. Unlocking the biological consequences of these effects on wild fish is notoriously challenging, especially in highly productive but naturally variable systems with uncertain futures such as Eastern Boundary current systems. Here, we developed otolith increment-based growth chronologies covering half a century (53 years) for a small pelagic fish (Atlantic horse mackerel, Trachurus trachurus) in the northern limb of the Canary current upwelling system. We used increasingly complex mixed-effects models to partition individually resolved growth variation among intrinsic (Age and Age-at-capture) and extrinsic (biotic and abiotic factors) sources in four complementary data sets: a general population chronology, and three chronologies derived from age groups that reflect ontogenetic habitat shifts. First, we investigated the timing and scale of growth phase shifts and assessed the effects of extrinsic factors on inter-annual growth variation. Second, we quantified among and within cohort growth variability over time. Our results provided strong evidence for inter-annual SST and primary productivity variation impacting on Atlantic horse mackerel growth. We also identified phase shifts in growth that point to larger ecosystem-wide changes (regime shifts), potentially driven by large-scale climatic indices, such as North Atlantic Oscillation and East Atlantic pattern. Cohort-dependent growth effects likely reflect persistent environmental influences and density dependence. Further, we found evidence for carryover effects in growth whereby a poor start in life tended to persist despite compensatory growth being observed in some individuals. We show how population productivity can be impacted by multiple, interacting environmental and biotic factors leading to potential ecosystem regime shifts. Such information is key to understand recruitment dynamics and population persistence, and will have important implications for fisheries management and to those seeking to understand the effects of large-scale climate change on marine productivity.

Physical-biological interactions in the ocean: case studies from the northern Canary Current Upwelling Ecosystem

Physical-biological interactions in the ocean: case studies from the northern Canary Current Upwelling Ecosystem

Microbial communities in the nepheloid layers and hypoxic zones of the Canary Current upwelling system.

Eastern boundary upwelling systems (EBUSs) are among the most productive marine environments in the world. The Canary Current upwelling system off the coast of Mauritania and Morocco is the second most productive of the four EBUS, where nutrient‐rich waters fuel perennial phytoplankton blooms, evident by high chlorophyll a concentrations off Cape Blanc, Mauritania. High primary production leads to eutrophic waters in the surface layers, whereas sinking phytoplankton debris and horizontally dispersed particles form nepheloid layers (NLs) and hypoxic waters at depth. We used Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD‐FISH) in combination with fatty acid (measured as methyl ester; FAME) profiles to investigate the bacterial and archaeal community composition along transects from neritic to pelagic waters within the “giant Cape Blanc filament” in two consecutive years (2010 and 2011), and to evaluate the usage of FAME data for microbial community studies. We also report the first fatty acid profile of Pelagibacterales strain HTCC7211 which was used as a reference profile for the SAR11 clade. Unexpectedly, the reference profile contained low concentrations of long chain fatty acids 18:1 cis11, 18:1 cis11 11methyl, and 19:0 cyclo11–12 fatty acids, the main compounds in other Alphaproteobacteria. Members of the free‐living SAR11 clade were found at increased relative abundance in the hypoxic waters in both years. In contrast, the depth profiles of Gammaproteobacteria (including Alteromonas and Pseudoalteromonas), Bacteroidetes, Roseobacter, and Synechococcus showed high abundances of these groups in layers where particle abundance was high, suggesting that particle attachment or association is an important mechanisms of dispersal for these groups. Collectively, our results highlight the influence of NLs, horizontal particle transport, and low oxygen on the structure and dispersal of microbial communities in upwelling systems.

Trends in Primary Production in the Canary Current Upwelling System—A Regional Perspective Comparing Remote Sensing Models

After Andrew (Bakun, 1990) formulated his hypothesis of upwelling intensification caused by increasing global warming, contradictory results have been published on whether primary productivity is increasing or decreasing in Eastern Boundary Upwelling Ecosystems (EBUE). The present work is focused in comparing three net primary production (NPP) models -the VGPM (Vertically Generalized Production Model), the Eppley-VGPM and the CbPM (Carbon-based Production Model)- in the Canary Current (CanC) EBUE during the 1998-2015 period, making use of both SeaWiFS (Sea-viewing Wide Field-of-view Sensor) and MODIS (MODerate-resolution Imaging Spectroradiometer) derived data. We looked for the first time for seasonal to interannual trends of NPP under a regional perspective, with the aim of searching for temporal patterns that could support or reject the intensification hypothesis. According to previous studies based on the seasonality of the upwelling regime, the CanC EBUE was divided into three subregions: a seasonal upwelling zone (SUZ; 13-20oN), a permanent upwelling zone (PUZ; 20-26oN) and a weak permanent upwelling zone (WPUZ; 26-33oN). Our analyses do not show significant increasing trends in NPP with any of the productivity models used, challenging Bakun’s hypothesis. Nevertheless, differences in the output of the models are important, both at regional and subregional scales, questioning the accuracy of the models. The comparison made in this work clearly shows the disagreements between some of the best-known NPP models and calls for a validation effort in this region. Contrary to the open-ocean, temperature trends show significant decreases in certain areas over the shelf waters, which might indicate an increase of cool, upwelled waters in those regions. Seasonal to decadal anomalies of NPP and sea-surface temperature (SST) are estimated and analyzed in relation to selected climate indices, yielding only significant correlations between SST and the North Atlantic Oscillation (NAO) indices.