The family Chaetocerotaceae includes the genera Chaetoceros and Bacteriastrum, with Chaetoceros being one of the most cosmopolitan, abundant, and diverse diatom genera in the oceans. This study investigated the diversity and seasonal dynamics of the Chaetocerotaceae in surface waters of two coastal sites along the Catalan coast (Barcelona and Blanes Bay), from 2004 to 2019. A combination of field sample observations, morphological (light and scanning electron microscopy), and molecular (SSU and LSU rDNA gene sequences) analyses of monoclonal cultures, and V4 18S rDNA metabarcoding time-series data from Blanes was used for species identification. The seasonal dynamics of both genera were investigated during two annual cycles at both sites through monthly light microscopy observations and, at Blanes Bay, also through the metabarcoding dataset. A total of 60 species of Chaetoceros and 10 of Bacteriastrum were detected. Based on cell ultramorphology and SSU and LSU rDNA gene phylogenies, two species within the genus Chaetoceros are putatively new to science, although they are not formally described here. The most abundant and frequent taxa were C. tenuissimus, C. socialis, C. vixvisibilis, and the C. curvisetus complex. These species presented similar seasonal trends at both sites, with C. tenuissimus and C. vixvisibilis peaking in late spring and summer, whereas C. socialis was more prevalent in winter. The C. curvisetus complex did not show a clear seasonality although its components were less abundant in summer. These results highlight the value of integrating morphological and molecular approaches to assess the diversity and ecological dynamics of the dominant Chaetoceros species.

Parasitoid communities associated with summer dinoflagellate blooms in the north-western Mediterranean showed temporal partitioning, taxon-specific dynamics and contrasting associations with the water column and sediments. Several zoosporic parasitoid lineages co-occurred, including perkinsids, chytrids and Syndiniales such as Amoebophrya and Euduboscquella-like taxa. Members of the Amoebophrya complex (Dino-Group-II clades 2 and 4) had the highest relative sequence abundances in the water column, and their increases coincided with peaks or declines in dominant host populations, a pattern consistent with density-responsive infection dynamics. Perkinsids also exhibited patterns consistent with density-responsive dynamics, with peaks near declines in host abundance; they were detected in both the water column and sediments. Chytrids occurred sporadically, with low infection prevalence in the water column and only occasional detection in sediments. These contrasting patterns were consistent with temporal differentiation among host–parasitoid interactions associated with differences in host tracking, infection timing and habitat use. Overall, infection prevalence remained low and parasitoid peaks were not consistently associated with bloom termination, although persistent, low-intensity infections may have influenced competitive interactions among hosts and species coexistence. Differences in temporal occurrence and compartment associations may facilitate coexistence among parasitoid lineages. Sediments may act as reservoirs, particularly for perkinsids, suggesting that benthic–pelagic coupling contributes to the structure of marine parasitoid communities.

The majority of species of the highly diverse genus Chaetoceros are described as chain-forming, although several species are described as strictly solitary (such as C. tenuissimus) or having an alternate solitary and a chain-forming phase during their life history (such as C. salsugineus). In this study, the diversity of small forms of Chaetoceros from the NW Mediterranean coastal waters was explored through the morphological and molecular characterization of four different strains belonging to two distinct species. Based on their morphology, three of the strains were identified as C. salsugineus (Takano, 1983). The SSU and LSU rDNA sequences represented the first available for well-characterized C. salsugineus strains and were 96.6-100% similar to publicly available C. tenuissimus (Meunier, 1913) sequences. Both species share the same morphological features, such as setae and ultrastructure of the valves, as well as the rimoportula characteristics. In addition, the morphology of the solitary form of C. salsugineus matched with that of C. tenuissimus. Here, we propose the two species as synonyms (the name C. tenuissimus prevailing as it has priority for this taxon), emend the original description and designate an epitype. The fourth strain was identified as C. olympicus sp. nov., a new species, which alternates solitary and chain-forming forms within its life history. The main differential characteristics of this species are the absence of rimoportula both in terminal and intercalary valves, the setae ultrastructure, which is thin and circular in cross-section with a few, slightly twisted, rows of small rectangular poroids and some spirally arranged spines, and the morphology of the resting spores, with primary valve vaulted and covered with short to medium-sized spines, and secondary valve smaller, rounded and smooth. A comparison of C. tenuissimus and C. olympicus with other species as well as information on their life cycle and ecology is also provided. HIGHLIGHTS center dot Description of a new Chaetoceros species: C. olympicus. center dot Proposal that C. tenuissimus and C. salsugineus are synonyms. center dot Importance of morphological variability in life cycles for species identification.

The southern Alboran Sea is a highly dynamic region in the Mediterranean. However, there is few data on microphytoplankton which is, an important component of the marine ecosystem. We therefore collected microphytoplankton samples and related the biomass and diversity patterns to ambient variability, considering cross-shore and longitudinal gradients. There was a general eastward decrease in both species richness and biomass, with Cape Three Forks as a transitional point. Diversity increased in coastal areas and decreased with depth. High chlorophyll-a concentrations corresponded to low temperature and low-salinity waters, indicating the Atlantic origin. Microphytoplankton biomass was low in comparison with total chlorophyll, suggesting a dominance of nano- and picophytoplankton. Biomass values increased in the stretch between Cape Three Forks and Al Hoceima Bay, an area highly influenced by upwelled water originating from the northern Alboran Sea. We suggest that the Western Alboran Gyre enhances the development of dinoflagellates while local upwelling enhances the development of diatoms. A statistical relationship was found between microphytoplankton biomass and diversity, especially when diversity was estimated as species richness. These results are crucial for understanding microphytoplankton dynamics and trends in an area that is undergoing climate-derived changes and biodiversity losses.

Particulate organic matter (POM) lability is one of the key factors determining the residence time of organic carbon (OC) in the marine system. Phytoplankton community composition can influence the rate at which heterotrophic microorganisms decompose phytoplankton detrital particles and thus, it controls the fraction of OC that reaches the ocean depths, where it can be sequestered for climate-relevant spans of time. Here, we compared the degradation dynamics of POM from phytoplankton assemblages of contrasting diatom dominance in the presence of mesopelagic prokaryotic communities during a 19-day degradation experiment. We found that diatom-derived POM exhibited an exponential decay rate approximately three times lower than that derived from a community dominated by flagellated phytoplankton (mainly coccolithophores and nanoflagellates). Additionally, dissolved organic matter (DOM) released during the degradation of diatom particles accumulated over the experiment, whereas only residual increases in DOM were detected during the degradation of non-diatom materials. These results suggest that diatom-dominance enhances the efficiencies of the biological carbon pump and microbial carbon pump through the relatively reduced labilities of diatom particles and of the dissolved materials that arise from their microbial processing.

VII International Symposium on Marine Sciences (ISMS 2020), 1-3 July 2020 (Barcelona).-- 1 page, 1 video

1st Meeting of the Iberian Ecological Society (SIBECOL) & XIV Asociacion Espanola de Ecologia Terrestre (AEET) Meeting, Ecology: an integrative science in the Anthropocene, 4-7 February 2019, Barcelona, Spain.-- 1 page

XIII Reunion Iberica de Algas Toxicas y Biotoxinas Marinas (REDIBAL 2018) - XIII Reunion Iberica de Fitoplancton Toxico - XIII Iberian Toxic Algae and Marine Biotoxins Meeting, VI Simposio Internacional de Ciencias del Mar - VI International Symposium of Marine Sciences (ISMS 2018), 20- 22 June 2018, Vigo.-- 1 page

XXXIV Trobades Cientifiques de la Mediterrania : Fisica i ecologia: reptes de frontera, celebradas del 9 al 11 de octubre de 2018 en Mao, Menorca

In a global context of climate change affecting the marine environment, it is important to consider the effect of extreme events in driving ecological change and to gain a better understanding of conditions to be expected under future scenarios. In this study we focus on monthly oceanographic data collected off Barcelona city during the period 2002-2012, in which extreme air temperatures and exceptional oceanographic events were reported in the western Mediterranean basin. These included two extreme heat waves and major episodes of dense water formation that produced unusually large deep-water contributions, induced oceanographic changes in the coastal zone and caused significant alterations to the marine ecosystem. To determine whether routine monitoring of oceanographic variables in a coastal zone can provide information for recognizing such large-scale events, temperature, salinity, turbidity and fluorescence were analysed to identify their signatures. The results provide an additional tool for monitoring oceanographic events and improving forecasts and future projections.

The 18th International Conference on Harmful Algae (ICHA), From ecosystems to socio-ecosystems, 21-26 October 2018, Nantes, France.-- 1 page

ICES - IOC Working Group on Harmful Algal Bloom Dynamics (WGHABD), 24-28 April 2018, Tarragona, Spain.-- 2 pages

Plankton ecology has been the object of intense research and progress in the last few decades.This has been partly due to technological advances that have facilitated the multidisciplinary and high-resolution sampling of ecosystems and improved experimentation and analytical methodologies, and to sophisticated modelling.In addition, exceptional researchers have had the vision to integrate all these innovative tools to form a solid theoretical background in ecology.Here we provide an overview of the outstanding research work conducted by Professor Marta Estrada and her pioneering contribution to different areas of research in the last four decades.Her research in biological oceanography has mainly focussed on phytoplankton ecology, taxonomy and physiology, the functional structure of plankton communities, and physical and biological interactions in marine ecosystems.She has combined a variety of field and laboratory approaches and methodologies, from microscopy to satellite observations, including in-depth statistical data analysis and modelling.She has been a reference for scientists all over the world.Here, her contributions to plankton ecology are summarized by some of her students and closest collaborators, who had the privilege to share their science and everyday experiences with her.

Sampedro, Nagore ... et. al.-- 17th International Conference on Harmful Algae (ICHA), 9-14 October 2016, Florianopolis, Santa Catarina, Brazil.-- 1 page

International Symposium CLIMATE-ES 2015, Progress on climate change detection and projections over Spain since the findings of the IPCC AR5, 11-13 March 2015, Tortosa, Tarragona, Spain.-1 page