Environmental and anthropogenic driven transitions in the demersal ecosystem of Cantabrian Sea

In the framework of global human-induced change, marine communities’ often respond to changing conditions abruptly reorganizing into new equilibria. These shifts are difficult to predict and often imply irreversible adjustments due to hysteresis. Unraveling the role of the forces leading regime shifts is a major challenge. We explored the temporal evolution of 63 fish species representing the Cantabrian bentho-demersal community in response to environmental changes and fishing pressure in the period 1983–2018, using survey data. Via multivariate analysis and non-additive modeling of a community index and the system's main stressors, two decadal-scale regimes were revealed, suggesting a non-linear response of the community to its environment. The Integrated Resilience Assessment framework elucidated the response mechanism to the candidate stressors and allowed quantifying resilience dynamics. The decline in fishing pressure in the 1990s was associated with a gradual transition of the system, while further decline during the 2000s eroded the resilience of the system towards changes in its stressors, leading to a discontinuous response expressed as an abrupt, possibly irreversible shift in the 2010s. Given the teleconnected character of marine ecosystems, this regional study endorses the scientific effort for actions facing the dynamic impacts of climate change on exploited marine ecosystems.En prensa2,27

Recent freshening and cooling of Biscay subsurface waters

The monitoring program Radiales (https://www.seriestemporales-ieo.net/) by the Spanish Institute of Oceanography, has been providing hydrographical and biogeochemical series in marine waters around Spain on a monthly basis from early 90's. The proximity of the shelf-break in front of the city of Santander (SE Bay of Biscay) allowed tracking intermediate and deep waters along the standard section perpendicular to this city for three decades (sampling was limited to 1000 meter until late 2007, then extended to 1500 m, and full-depth 2400 m since 2014). From the start of the sampling in nearly 90`s, subsurface waters showed unabated warming and salt-increase. Warming was linked to isopycnal sinking (heave) during the 90`s and early 00`s until the occurrence of very strong winter mixing in 2005 that shifted quickly the salinity down to lower East North Atlantic Central Waters (ENACW) levels (ca. 400 m). Overall, warming and salt-increase at the core of ENACW added up to 0.3ºC and 0.08 in salinity within only two and a bit decades. In 2014, the upper central waters showed freshening and cooling for the first time in the series, a process that enhanced in the following years especially in salinity that currently (2021) presents the lowest value of the overall timeseries. This shift in regional hydrography follows the large salinity drop observed in the subpolar gyre around 2012 and its subsequent expansion downstream into the subtropical gyre and subarctic seas. This regime shift implies that subsurface environmental conditions in the region have returned back to 90`s state, contrasting to the uppermost waters which continue to show large positive anomalies. The effects of this cold and freshwater inflow in the regional circulation of southern Biscay are discussed

Biscay AGL. An observatory for state of the art operational oceanography at IEO. Derived products, sensor networks and future developments.

Since 1991, shelf and slope waters of the Southern Bay of Biscay are regularly sampled in a monthly hydrographical section north of Santander. From 2003, a deep hydrological standard section was included and on June 2007, an ocean-meteorological buoy was moored at the end of Santander Section (www.boya_agl.st.ieo.es). All of three are part of IEOOS (IEO Observing System). Biscay AGL is one observatory for the EU FixO3 project. The combination of these resources leads to a powerful tool, Biscay AGL, which is more than the combination of the AGL Buoy and the hydrographical samplings. This tool produces not only time series of several parameters at different time resolutions but also derived products, both real and delayed time. Derived products from this buoy include, annual cycles as well as anomalous values. In particular ones such as air-sea heat fluxes, salinity and water temperatures anomalies, sub inertial currents series, chlorophyll surface series, estimate of the mixed layer depth and wind and currents roses. Many sensor networks have been deployed to monitor marine environment, and more will follow in the future. Due to the large number of sensor manufacturers, integrating diverse sensors into observation systems is not straightforward. By defining standardized service interfaces it is possible to enable access to sensor networks and archived sensor data that can be discovered and accessed using standard protocols and application programming interfaces. Future developments include the deployment of a full sensor network as well as adding new devices to the Biscay AGL tool in order to achieve deeper knowledge of the ocean

Data archeology: in the pursuit of the longest sea temperature time-series on the North Spanish Coast.

Recent attempts to recover historical data show that, in general, measurements that are not incorporated into standardized databases are irretrievably lost within 10 years. However, some historical records are kept in the institutions, either due to the personal interest of some researchers, or because of good archiving practices maintained over time. The damages of paper records makes their retrieval more and more difficult, and the digitization and validation work is time and effort consuming. Nevertheless, the old data taken time ago are invaluable for climate studies that require the longest time series available in order to establish long-term cycles and trends, as well as to incorporate them into numerical models that allow predict the ocean behavior in relation to climate change. In the 1920s, the Santander Oceanographic Centre, (North coast of Spain), began a series of coastal measures that, with different time lapses, have been maintained over time to the present day. First repeated records of temperature at different depth levels, were made with inversion thermometers and have been kept in log books. A digitization and validation process has recently begun, which will allow the reconstruction of the longest sea temperature series in the area and their climatic characterization. At this time, the monthly measurements carried out from 1928-1964 in the area outside the Bay of Santander have been recovered. After their validation, it is expected that they will be incorporated into the NODC's institutional database for permanent storage and reusing in future studies

Habitat use by Gadiculus argenteus (Pisces, Gadidae) in the Galician and Cantabrian Sea waters (NE Atlantic)

Forage fish species play a crucial role in most ecosystems, transferring energy from plankton to larger fishes. Therefore, understanding the factors driving the dynamics of forage fish populations is essential in marine ecosystems. Gadiculus argenteus is an important forage fish species in the Galicia and Cantabrian Sea ecosystem. In this study, the influence of several biotic and abiotic factors on the distribution of this species was examined using generalized additive models in a 2-step approach. G. argenteus habitat preference was not affected by changes in annual abundance during the study period (1998-2019). From the variables selected in the final models, depth and geographic location (latitude and longitude) were the most important factors to describe the presence of G. argenteus. Peak abundance was found on the upper slope and although the species was found throughout the study area, its higher abundance values were located in Galician waters. The species seemed to avoid coarse sand bottoms, with mean chlorophyll a concentration showing a positive effect on the presence and abundance of G. argenteus. Interestingly, the observed aggregations of G. argenteus showed a remarkable similarity to the commercial trawling footprint in the area, suggesting a strong link between the distribution of this forage species and the distribution of its predators, most of which are important commercial species. Further work should focus on a better understanding of this relationship to provide important information on the study of the structure and functioning of the marine ecosystem of the northern Spanish continental shelf.Versión del editor2,48

Sensor Networks and derived products at Biscay AGL observatory. State of the art operational oceanography at IEO

Since 1991, shelf and slope waters of the Southern Bay of Biscay are regularly sampled in a monthly hydrographical section north of Santander, and on June 2007, an ocean meteorological buoy was moored at the end of Santander Section (www. boya_agl.st.ieo.es). Both are part of IEOOS (IEO Observing System). Biscay AGL is one observatory for the EU FixO3 project. Many sensor networks have been deployed to monitor marine environment, and more will follow in the future. Due to the large number of sensor technologies, integrating diverse sensors into observation systems is not straightforward. By defining standardized service interfaces (like those based on OGC standards) it is possible to enable access to sensor networks and archived sensor data that can be discovered and accessed using standard protocols and application programming interfaces, therefore complying with the requirements of the INSPIRE directive. Future developments include the deployment of a full sensor network as well as adding new devices to the Biscay AGL tool in order to achieve a deeper knowledge of the ocean. Biscay AGL is more than the combination of the AGL Buoy and the hydrographical samplings. This observatory produces not only time series of several parameters at different time resolutions but also derived products, both in real and in delayed time. Derived products from this buoy include annual cycles as well as anomalies of physical and biogeochemical magnitudes like air-sea heat fluxes, salinity and water temperatures, sub inertial currents, surface chlorophyll. Different products are derived from in-situ measurements at the AGL buoy like estimates of the mixed layer depth, wind and currents roses and wave intensity diagrams

New developments on Biscay-AGL Observatory. From derived products to sensor networks.

Biscay-AGL Observatory. Since 1991, shelf and slope waters of the Southern Bay of Biscay are regularly sampled in a monthly hydrographical section north of Santander to a maximum depth of 2500m, as part of the IEO Radiales program. On June 2007, an ocean-meteorological buoy (AGL) was moored at the end of Santander standard section, 22nm north at 2850m depth, to complete the ocean information with the ocean-atmosphere interaction. All of them are part of IEO Observing System (1). The integrated system of AGL and its nearest hydrographic station (2600m depth) is named Biscay-AGL observatory. It is also one station for the EU FixO3 project. Joint resources and systematic analysis lead to a powerful tool, which is much more than the combination of the AGL buoy and the hydrographical samplings. Data Access. All AGL buoy collected data are added to the local database sited at IEO-Santander in real-time and, after rutinary automatised quality controls, they are immediately available through its dedicated webpage (www.boya_agl.st.ieo.es). Monthly CTDO2 data from the hydrographic section are lab-calibrated in order to obtain acurated values of salinity, dissolved oxygen and density, and added to the long-term time series. Biscay-AGL data are quality controlled, flagged and formatted according internationally agreed standards (2, 3) and routinely sent to the IEO Datacenter. This added-value controlled data are incorporated to the IEO permanent archive and made freely available through the SeaDataNet infrastructure for data access and discovery. Derived products. Data acquired by Biscay-AGL may be displayed as timeseries as usual, but end-users are benefited by derived products which provide direct information. A recently developed software tool produces not only timeseries of several parameters at different time resolutions but also derived products, both real and delayed time. Derived products from this buoy include, but not only, annual cycles as well as anomalous values, air-sea heat fluxes, salinity and water temperature anomalies, subinertial currents series, chlorophyll surface series, estimations of the mixed layer depth and wind and currents roses. Sensor Web Enablement (SWE). Sensor Web infrastructures are setup to access real-time data observed by sensors. This system has been implemented in AGL buoy sensors in order to simplify the retrieved events and alerts triggered through sensors. All those functionalities of the Sensor Web are provided in an interoperable way, following the standards stablished by the Open Geospatial Consortium (OGC). By defining standardized service interfaces, these services hides the heterogeneity of the sensor network, its communication details, enabling the access to archived sensor data that can be discovered and accessed using standard protocols and application programming interfaces

Three decades of continuous ocean observations in North Atlantic Spanish waters: The RADIALES time series project, context, achievements and challenges

Ship-based time-series observations provide crucial data for understanding marine ecosystems, improving decision making in ocean and coastal management. However, only a few time series survive for more than a decade. RADIALES is one of the longest multidisciplinary programs in operation in the northern and northwestern coast of Spain. In the last 30 years, this program collected monthly data on physical, chemical and plankton observations in an array of five sections of stations representative of upwelling and stratified dynamics. Here, the main achievements, including key contributions to ecosystem conservation policies, are summarized. The development of this program, in line with similar initiatives in other countries, included phases focused on the study of seasonality, on comparative analysis, and lately on the analysis of decadal variability and regime shifts. Furthermore, in recent years there was a substantial improvement in the identification of plankton species by genomics. Among the main findings of RADIALES are the quantification of ocean warming at subsurface layers, the determination of climatologies in thermohaline, biogeochemical and biological variables, the inventory of plankton species (from bacteria to zooplankton) and the identification of regionally coherent regime shifts. Baselines defined by RADIALES series were instrumental for the assessment of environmental impacts (e.g. oil spills) and for the support of environmental policies (e.g. Marine Strategy Framework Directive). By contributing to international databases, data from programs as RADIALES combined with new instrumental observations will help to develop a more coherent and comprehensive understanding of the ocean ecosystems, enhancing our ability to detect and forecast risks.IEO, GAIN (Xunta de Galicia)Versión del editor3,26

The Spanish Institute of Oceanography Observing System around N and NW Iberia

In the late 80's, the Spanish Institute of Oceanography (IEO) began some ambitious programs of monitoring around the Iberian Peninsula. The coastal observing system core structure was the Radiales program, a series of transects nearby most coastal IEO laboratories where a minimum set of hydrographical, chemical and biological parameters is sampled monthly. The sections are designed to be completed in one-day journeys so the system is supported by quite small vessels, mainly covering the continental shelf with the noteworthy exception of the Santander Section, where the proximity of the shelf-break allows sampling deep waters monthly. During the last 20 years the program has supported many specific scientific research projects and has created a detailed description of seasonal to interannual variability in the coastal ecosystem that serves as a baseline to explore long-term changes or trends...Versión de auto