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[spa] Debido a las condiciones ambientales y características biológicas únicas de los ambientes marinos antárticos, los efectos del cambio climático pueden ser devastadores y pueden reflejar el posible futuro a gran escala de los ecosistemas marinos. La Antártida es, además, un sumidero de algunos contaminantes como los elementos traza y la península Antártica se considera una de las zonas más afectadas por el calentamiento global de todo el planeta. El objetivo principal de esta tesis ha sido profundizar en el conocimiento de los ecosistemas bentónicos marinos antárticos estudiando las interacciones biológicas y el efecto del cambio global. En el bentos somero antártico, las esponjas dominan la comunidad siendo fuente de C para una serie de depredadores como el nudibranquio Doris kerguelenensis, un espongívoro generalista. En isla Decepción se observó la presencia de este sobre diversas especies de esponjas. El análisis de isótopos estables de C y N y de ácidos grasos de este molusco y las esponjas más abundantes de la zona, y de algunos productores primarios demostraron que el molusco se alimenta, aunque no exclusivamente, de las esponjas Dendrilla antarctica, Mycale acerata, Haliclona sp. y Axinella crinita. En un estudio previo en la Antártida se detectó un gradiente norte-sur en la concentración de elementos traza, siendo mayor al norte (con mayor presencia humana). En nuestro trabajo se detectaron elementos traza (Cr, Pb, Hg) en una comunidad bentónica a lo largo de la Península Antártica, demostrando que la concentración de estos estaba más influenciada por las condiciones locales que por el gradiente norte-sur de la actividad humana. Las esponjas mantienen una relación muy estrecha con su microbiota, la cual realiza funciones vitales para el animal. Se evaluó el efecto de un estrés térmico en la composición y estructura de la microbiota de las esponjas, siendo las esponjas antárticas más resistentes al estrés térmico que la de esponjas templadas y tropicales, aunque el efecto en la fisiología de la esponja es desconocido. Las esponjas utilizan metabolitos secundarios como compuestos de defensa. El perfil químico de la esponja Dendrilla antarctica mostró una alta variabilidad intraespecífica, y variabilidad en esponjas de diferentes islas. Se caracterizó un nuevo diterpeno, la decepcionina. En conclusión, el estudio de las comunidades bentónicas desde diferentes perspectivas nos ha permitido construir una imagen más amplia del funcionamiento y condiciones de estos poco conocidos habitantes de las aguas polares., [eng] Due to the unique environmental conditions and biological characteristics of Antarctic marine environments, the effects of climate change can be devastating and may reflect future scenarios for other regions. Antarctica is also a sink for some pollutants such as trace elements and the Antarctic Peninsula is considered among the most affected areas by global change on the planet. The main objective of this thesis is to deepen the knowledge of the Antarctic marine benthic ecosystems studying biological interactions and the potential effect of environmental change. In shallow Antarctic benthos, sponges often dominate the communities being a source of carbon for predators like the nudibranch Doris kerguelenensis, a generalist spongivore. In Deception Island it was found upon various species of sponges. Analyses of C and N stable isotopes and fatty acids of this mollusc, the most abundant sponges in the area, and some primary producers were performed. The mollusc feeds upon the sponges Dendrilla antarctica, Mycale acerata, Haliclona sp., and Axinella crinita, but not exclusively. In Antarctica, a previous study detected a gradient in trace elements, larger to the north (higher human presence) and decreasing towards the south. The presence of Cr, Pb, and Hg was analyzed here in a benthic community along the Antarctic Peninsula, demonstrating that the concentration of these elements was influenced by local conditions rather than by the north-south human activity gradient. Sponges maintain a very close relationship with their microbiota, which performs vital functions for the animal. To evaluate the effect of heat stress on their microbiota, experiments were carried out exposing sponges from different habitats to heat stress. The microbiota of the Antarctic sponges seems to be more resistant to heat stress than that of temperate and tropical sponges, although the effects on the physiology of the sponge remain to be investigated. Sponges use secondary metabolites as defensive compounds. The chemical profile of Dendrilla antarctica showed a high intraspecific variability, but also a differentiation in the predominant metabolites in sponges from different islands. A new diterpene, deceptionin, was characterized. In conclusion, the study of benthic communities from different perspectives has allowed us to build a broader picture of the functioning and conditions of these little-known inhabitants of polar waters.

Due the ability of plastics to act as a substrate to develop biofilms and their persistence in the environment, plastics have been claimed as vectors of bacterial dispersal. We evaluated the presence of faecal and marine bacteria adhering to the biofilm developed on marine plastics and the abundance of antibiotic resistance genes (ARGs). Thus, we sampled coastal waters around the mouths of the Besòs and Llobregat rivers. Both areas are strongly impacted by human faecal pollution (either from rivers and submarine sewage outfalls). Samples of water, sediments and plastics from surface waters and sediments were collected during two campaigns in summer and autumn 2021. The presence of the faecal indicators E. coli, enterococci and crAssphage, 3 ARGs, potential pathogens lik Pseudomonas spp. and Vibrio spp. and other marine bacteria was analysed by culture and/or molecular methods. Results indicate that plastics are covered by a bacterial biofilm mainly of marine bacteria (4.9·10⁴ to 8.7·10⁶ gc mm-2) including Vibrio species. Low concentration of viable E. coli and Enterococci (42% and 67% of the samples) was detected on floating plastics. The ARGs sulI, blaTEM and tetW were detected in 67 - 88% of the surface plastic samples and 29 - 57% of the sediment plastics with a concentration of up to 6.7·102 gc·mm-2. These results suggest that the plastic debris may have come from wastewater or been colonised in environments with faecal contamination. The presence of faecal indicators in sediment plastics was null or low. Therefore, although in low concentrations, faecal bacteria and species of Pseudomonas and Vibrio were identified in marine plastics, suggesting that plastic pollution may be a potential reservoir of human pathogens and ARGs. Considering the abundance of plastic in aquatic environments (expected to increase in the future), its potential risk to public health must be assessed. Also see: https://micro2022.sciencesconf.org/425977/document, In MICRO 2022, Online Atlas Edition: Plastic Pollution from MACRO to nano

Association of Polar Early Career Scientists (APECS) Conference 2020, Opening Doors: Collaboration across knowledge systems, 20 May 2020, Doris kerguelenensis is an Antarctic heterobranch mollusc feeding on several demosponges and hexactinellid sponges. To assess the contribution of several sponge species to its diet at Deception Island we used stable isotopes of C and N, as well as fatty acids. We examined the demosponges Axinella crinita, Dendrilla antarctica, Hemigellius pilosus, Kirkpatrickia variolosa, Mycale acerata, Sphaerotylus antarcticus, and Haliclona sp. We also analyzed the macroalgae Desmarestia anceps and Himantothallus grandifolius, and phytoplankton. D. anceps was the most 13C depleted one and phytoplankton the most enriched. The δ13C values of sponges and D. kerguelenensis laid in between. The δ15N values of A. crinita, D. antarctica, M. acerata and Haliclona sp. suggested a trophic position between 2-3, and for H. pilosus and S. antarcticus between 3-4. Kirkpatrickia variolosa was in between the two groups. The δ15N values of D. kerguelenensis revealed a trophic position from 3-4. All sponges and D. kerguelenensis had high levels of 15:0 and EPA and low levels of arachidonic acid, largely differing from macroalgae. Fatty acid profiles of A. crinita, D. antarctica, K. variolosa, M. acerata, S. antarcticus, and Haliclona sp. were similar to phytoplankton, but D. kerguelenensis and H. pilosus were enriched in 17:0, 20:1n9 and 20:2. D. kerguelenensis, A. crinita, D. antarctica, K. variolosa, Haliclona sp. and S. antarcticus shared a long chain fatty acid absent in phytoplankton and macroalgae. The overall evidence suggests that A. crinita, D. antarctica, K. variolosa and Haliclona sp. are the most likely prey of D. kerguelenensis at Deception Island

VII International Symposium on Marine Sciences (ISMS 2020), 1-3 July 2020 (Barcelona).-- 1 page, Doris kerguelenensisis an Antarctic heterobranch molluscf eeding on several demosponges and hexactinellid sponges. To assess the contribution of several sponge species to its diet at Deception Island we used stable isotopes of C and N, as well as fatty acids. We examined the demosponges Axinella crinita, Dendrilla antarctica, Hemigellius pilosus, Kirkpatrickia variolosa, Mycale acerata, Sphaerotylus antarcticus, and Haliclona sp. We also analyzed the macroalgae Desmarestia anceps and Himantothallus grandifolius, and phytoplankton. D. anceps was the most 13C depleted one and phytoplankton the most enriched. The δ13C values of sponges and D. kerguelenensis laid in between. The δ15N values of A. crinita, D. antarctica, M. acerata and Haliclona sp.suggested a trophic position between 2-3, and for H. pilosus and S. antarcticus between 3-4. Kirkpatrickia variolosa was in between the two groups. The δ15N values of D. kerguelenensis revealed a trophic position from 3-4. All sponges and D. kerguelenensis had high levels of 15:0 and EPA and low levels of arachidonic acid, largely differing from macroalgae. Fatty acid profiles of A. crinita, D. antarctica, K. variolosa, M. acerata, S. antarcticus, and Haliclona sp. were similar to phytoplankton, but D. kerguelenensis and H. pilosuswere enriched in 17:0, 20:1n9 and 20:2. D. kerguelenensis, A. crinita, D. antarctica, K. variolosa, Haliclona sp. and S. antarcticus shared a long chain fatty acid absent in phytoplankton and macroalgae.The overall evidence suggests that A. crinita, D. antarctica, K.v ariolosa and Haliclona sp. are the most likely prey of D. kerguelenensis at Deception Island

IX Simposio de Estudios Polares del Comité Español del Scientific Committee on Antarctic Research (SCAR), 5-7 September 2018, Madrid, España.-- 1 page, Understanding the structure of food webs is essential to determine ecosystems functioning. Primary production is highly seasonal in Antarctic ecosystems and organic matter reaches the benthos primarily as pulses during the summer months. The variability observed in food chain length and food web topology across natural ecosystems in shallow marine benthic Antarctic ecosystems could be explained by the latitudinal variation in day length throughout the year, and also by the latitudinal variation of the sea ice cover during winter period. This study aims to test the hypothesis that shorter and more redundant food webs prevail at higher latitudes as a result of a shorter summer season. Samples of phytoplankton and 14 other species from shallow rocky bottoms were collected at five locations along a latitudinal gradient including the South Shetland Islands and the Antarctic Peninsula. Stable isotopes of C and N and heavy metals were used as intrinsic markers in order to reconstruct the food web structure at each site and Layman metrics were used to describe and compare food web topology. Results revealed no latitudinal differences in food web topology along the South Shetland archipelago and the western Antarctic Peninsula. Nevertheless, local differences existed, because the C range was narrower in Esperanza and Rothera than in the other three sites. According to C and N stable isotope ratios, phytoplankton, encrusting red algae and detritus from macroalgae were the main sources of organic carbon for all the food webs considered. Everywhere, holothurians relied primarily on phytoplankton, sea urchins on a diversity of fleshy macroalgae and detritus, and limpets on encrusting red algae. On the other hand, sponges were the most depleted consumers in 13C and hence useda C source clearly different from that of herbivores, likely detritus from Desmarestia spp and/or bacterioplankton. In all sampled sites, the predator starfishes Odontaster validus and Diplasterias brucei were at approximately trophic level 3 and consumedvariable proportions of herbivores. Hg levels supported the above reported topology of the food web suggested by stable isotope ratios. In conclusion, the benthic food web of infralittoral rocky bottoms from the South Shetland Islands and western Antarctic Peninsula is short and redundant, but is supported by a diversity of carbon sources. There were no latitudinal differences in food web structure among sites, even though there were local differences. Hence, intrinsic markers suggest that shallow benthic communities are more influenced by local processes than by those operating at broader geographic scales