RADIALES time series: 25 years monitoring the NW Iberian shelf.

Presentación del proyecto RADIALES a investigadores y gestores del centro multidisciplinar OCEANUS y de OCEAn Networks CanadaIEO (RADIALES) Campus do Ma

Untangling the role of diversity in complex marine food webs: Recent developments using stable isotopes

Invited lecture. Online live Session 2Summary: trophic levels: a measure of functional diversity stable isotope tools: bulk vs. compound-specific analyses the basis: differential isotopic fractionation trophic indicators: trophic position, baselines, and much more application examples progress: multitrophic models, fingerprintingMCIN/AEI/10.13039/50110001103

Enhancing visibility of and access to long-term data.

Invited contribution to promote the use of marine data, particularly time serie

Plankton in the new millennium: synchronic multidecadal trends and regime shifts.

Invited lectureRecent changes in oceanic plankton are being reported at unprecedented rates. Most changes are related to environmental factors and many were identified as driven by climate, either through natural cycles or by anthropogenic effects. However, the separation of both effects is difficult because of the small size of most observational series. Moreover, some changes are related to trends and cycles while others were perceived as system shifts, often synchronized over large spatial scales. Here, studies on observational series of plankton, with the focus in the N Atlantic, are reviewed. Two main quasi-synchronic shifts in species assemblages were identified: one in late 1980’s and a most recent one in the first decade of the new millennium. While the origin and extent of most shifts vary locally, their synchronization seems to confirm the lagged response of plankton to changes in warming and in large-scale climatic factors. Changes in species abundance patterns are generally related to the strength of currents, but also to non-linear effects of warming, the latter particularly affecting species in regions near the limits of their thermal niche. Indeed, most of the changes are attributed to trade-offs between different biological strategies. Taken together, the reviewed case studies indicate a lagged biological response to variations in the local environment driven by large-scale climate forcing. The challenges for the interpretation of future changes include the consideration of local changes in a wider regional context, variations in species life-traits and possible top-down effects of plankton predatorsPID2020-115620RB-100 funded by MCIN/AEI/10.13039/50110001103

Manuel Varela Rodríguez (Malpica, 1954 – Caión, 2019)

2 pages.-- This work is licensed under a Creative Commons Attribution 4.0 International LicensePeer reviewe

Trophic flow within the microbial and mesozooplankton foodweb in the North Atlantic: processes indicated by analyses of stable isotopes and biovolume spectra.

The trophic flow from primary producers through the microbial and mesozooplankton food web makes sun energy available in particulate form for higher trophic levels. Pathways through the lower trophic levels are highly variable and determine productivity of the marine pelagic food webs. We analysed spatial variability in food web structure across the North Atlantic by means of stable isotope analyses (SIA) and biovolume spectrum theories (BST). At 7 stations in the Iceland Basin, Reykjanes Ridge, Irminger Basin and Labrador Sea, respectively, chlorophyll a, zooplankton net samples (55 μm and 150 μm) and laser optical plankton counter data were collected in the upper 200 to 500 m during a EURO-BASIN cruise with R/V M.S.Merian in spring (March/April) 2013. Trophic indices were determined by both methods (SIA and BST) for different size groups of the pelagic community. For the smallest fraction, both methods yielded trophic indices around 2 to 3 and agreed reasonable well. Large differences between both methods were observed in the mediumsized fraction, which was dominated by more omnivorous species, with much higher trophic indices estimated by BST. The largest fraction showed slightly higher value by BST, especially in the Labrador Sea. Comparing differences between SIA and BST might allow to trace energy flow through the microbial food web. A conceptual model is developed for the trophic flow through the lower trophic levels and discussed with respect to phytoplankton bloom stage, water mass, and stratification.EUROBASIN (FP7-ENV-2010 Project no. 264933

Trophic indices for micronektonic fishes reveal their dependence on the microbial system in the North Atlantic.

This research was funded by projects BATHYPELAGIC (CTM2016-78853-R) from the Plan Estatal de I+D+I (Spain), SUMMER (Grant Agreement 817806) and TRIATLAS (Grant Agreement 817578), from the European Union (Horizon 2020 Research and Innovation Programme), and Grant Number IN607A2018/2 from the Axencia Galega de Innovación (GAIN, Xunta de Galicia, Spain).The importance of microbes for the functioning of oceanic food webs is well established, but their relevance for top consumers is still poorly appreciated. Large differences in individual size, and consequently in growth rates and the relevant spatial and temporal scales involved, make the integration of microorganisms and large metazoans in a common food web framework difficult. Using stable isotopes, this study estimated the trophic position of 13 species of micronektonic fishes to examine the microbial and metazoan contribution to mid trophic level consumers. Vertically migrant species displayed higher trophic positions than non-migrant species in all depth layers. The estimated trophic positions agreed well with those from the literature, but all species displayed mean increases between 0.5 and 0.8 trophic positions when taking into account microbial trophic steps. Trophic position, but not the relative importance of the microbial food web, increased with individual size, suggesting that current estimates of the trophic position of top consumers and of the length of oceanic food webs are too low because they are based only on metazoan trophic steps. This finding calls for a review of trophic position estimates and of the efficiency of trophic transfers along oceanic food webs.This research was funded by projects BATHYPELAGIC (CTM2016-78853-R) from the Plan Estatal de I+D+I (Spain), SUMMER (Grant Agreement 817806) and TRIATLAS (Grant Agreement 817578), from the European Union (Horizon 2020 Research and Innovation Programme), and Grant Number IN607A2018/2 from the Axencia Galega de Innovación (GAIN, Xunta de Galicia, Spain).En prensa2,92

Seasonal succession of phytoplankton species on the coast of A Coruña (Galicia, northwest Spain)

Phytoplankton species composition was monitored monthly at two stations on the continental shelf off A Coruña (Galicia, northwest Spain). The deeper station (80 m) was sampled between May 1989 and December 1992. The coastal station (20 m) was studied during 1992. In each sampling, water samples were taken from selected depths throughout the water column. Microflagellates formed the bulk of phytoplankton, being dominant all year long, followed by diatoms, which dominated during phytoplankton blooms. The samples studied were arranged into five groups, according to environmental conditions defined for the main oceanographic periods in the area. Each group showed a characteristic phytoplankton species composition. The most important phytoplankton blooms occurred during spring and autumn. However, major phytoplankton abundances were also detected during upwelling events in the summer. Several species of the genus Chaetoceros, especially C. socialis (Lauder, 1864) were dominant during blooms, and accompanying species, e.g. Lauderia borealis (Gran, 1900), were important during spring and autumn. Leptocylindrus danicus (Cleve, 1889) made a major contribution to phytoplankton abundance during summer upwelling events. In contrast with studies conducted in neighbouring areas, dinoflagellates never dominated during summer stratification periods, probably because of the very frequent upwelling events, which caused destabilisation of the water column. During winter mixing and in deeper waters, we found a mixed community comprising species that are present throughout the year, but in very low densities, as well as resuspended diatoms from sediment. In 1992, at the coastal station, red-tide events occurred, and some species of dinoflagellates (e.g. Gymnodinium catenatum Graham, 1943) reached densities of well over 100 cells ml⁻¹. Considering the entire series of observations, the most noteworthy features are a decrease in the magnitude of diatom blooms during the study period and, on the contrary, an increase in the abundance of microflagellates.Se estudia la composición de especies y grupos taxonómicos de fitoplancton con una frecuencia aproximadamente mensual en dos estaciones de la plataforma continental frente a A Coruña (Galicia, noroeste de España). La estación más profunda (80 m) fue muestreada entre mayo de 1989 y diciembre de 1992. La estación costera (20 m) fue estudiada durante 1992. En cada muestreo se recogieron muestras repartidas por toda la columna de agua. El grupo de fitoplancton más numeroso fue el de los microflagelados, siempre dominantes en todas las épocas del año, seguido de las diatomeas, responsables de las principales proliferaciones de fitoplancton registradas. Las observaciones se clasificaron en cinco grupos según las características ambientales definidas para los principales periodos oceanográficos de esta zona. Cada uno de estos grupos presentó una composición de especies de fitoplancton característica. Las mayores proliferaciones de fitoplancton se produjeron en primavera y otoño, pero también se registraron elevadas abundancias durante episodios de afloramiento en verano. Varias especies del género Chaetoceros, especialmente C. socialis (Lauder, 1864), fueron las principales responsables de estas proliferaciones, acompañadas de otras especies de diatomeas como Lauderia borealis (Gran, 1900) en primavera y otoño, y Leptocylindrus danicus (Cleve, 1889) en el afloramiento de verano. A diferencia de lo encontrado en otras zonas próximas, los dinoflagelados no llegan a hacerse dominantes en el periodo de estratificación térmica de verano, probablemente debido a la frecuencia de los episodios de afloramiento. Durante el periodo de mezcla invernal y en las capas profundas de la columna de agua se encuentra una mezcla de especies presentes todo el año, aunque con bajas abundancias, y también diatomeas del sedimento resuspendidas. En 1992, especialmente en la estación costera, se produjeron episodios de marea roja durante el verano, superando algunas especies de dinoflagelados (como Gymnodinium catenatum Graham, 1943) 100 células ml⁻¹. Considerando toda la serie de observaciones, se aprecia una disminución en la magnitud de las proliferaciones de diatomeas y un incremento en la abundancia de microflagelados en los últimos años.Instituto Español de Oceanografí

Trends in the size of mesozooplankton during the last 25 years at A Coruña (N Spain)

Temporal changes in the mean individual size and in the abundance of taxonomical groups of different size of mesozooplankton (200-2000 µm) were investigated in samples collected in the shelf waters of A Coruña (N Spain) since 1988. An overall decreasing trend in the average size of individuals, indicated by the biomass (dry weight) to abundance ratio was observed. Most of this decrease can be attributed to the increase in the dominance of copepods of small size ( 1 mm) were found. Indeed, some species of large size showed increasing trends in abundance during the study period. Nevertheless these trends were small at linear scales and most species did not show significant linear trends during the study period. The observed trends in zooplankton were related to weak changes in sea surface temperature and upwelling intensity during the studied period. This suggests that the effects of the general warming of the surface ocean on plankton are weakened in regions of coastal upwelling.IEO (RADIALES

Ecology of Fucus vesiculosus (Phaeophyceae) at its southern limit of distribution: Growth and production of the early stages of development.

Growth and survival of two populations of Fucus vesiculosus were studied at its southern limit of distribution on the eastern Atlantic coast. Experimentally denuded areas at an estuarine and a semi-exposed site in an upwelling area (NW Spain) were followed for 17 months. Three different cohorts were detected during the sampling period. Differences among the three cohorts in terms of growth, reproduction and survival were detected. These differences may be due to the different time of appearance of the different cohorts or the presence of the previously established individuals when the second and third cohorts were recruited. Although the growth of the cohorts recruiting in autumn was higher than for the cohorts recruiting in spring and summer, the individual growth was represented in all cases by a logistic function, as the fastest rates of increase in length occurred during the first 6 months of life, and maximum length was attained after the thallus reached 1 year in age. In the same way, production was maximum for the first cohort, recruiting in autumn, even when it had the lowest survival rate, because of the rapid growth of survivors during spring and summer. For both populations, reproduction was continuous through the year but it was maximal during spring and summer. Protection from waves might have been thought to favour higher production and standing stock biomass values at the estuarine site compared with the semi-exposed site, while turnover rates of biomass were higher at the latter. Contrary to expectations, most of the nutrients available for the studied populations were not related to upwelling. Despite the fast initial growth of new recruits, both populations appeared to be very sensitive to denudation.Projects ANILE (CTM2009-08396, CTM2010-09904-E) Plan Nacional I+D+i and RADIALES (IEO)En prensa1,828