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Este artículo contiene 13 páginas, 5 figuras, 2 tablas. ; Marine ecosystems are threatened by cumulative human-related impacts that cause structural and functional alterations. In the Mediterranean Sea, the zooxanthellate coral Oculina patagonica (Scleractinia, Oculinidae) can turn algal forests into coral-dominated ecosystems and provides a case study for examining how zooxanthellate corals can affect the structure of algal-dominated shallow-water rocky ecosystems in temperate areas. Our goal was to provide a quantitative baseline assessment of O. patagonica demographics along ~1300 km of the Mediterranean Iberian coast and relate them to environmental parameters. The highest coral success was in the South Balearic Sea zone, where the populations exhibited N6-fold higher mean living coral cover, lower partial colonymortality and colony size distributions indicating that the populations in this zone were growing faster than those in the peripheral south-west (North Alborán Sea) and north-east (Mid and North Balearic Sea, and West Gulf of Lyons) zones. The coral demographics (i.e., density, cover, and skewness and kurtosis coefficients of colony size distributions) were positively correlated with each other and the annual mean seawater temperature (ST), 10th-ST percentile (P10th-ST), 90th-ST percentile (P90th-ST) and photosynthetically active radiation at 3-m depth (PAR-3m), but they were negatively correlated with chlorophyll-a. Based on these results, we identified the following thresholds that may constrain the growth of O. patagonica colonies and populations: annual mean ST b19–20 °C, P10th-ST b14 °C, P90th-ST b25 °C and N27 °C, and PAR-3m b30 mol photons m−2 day−1. The species abundance along the Iberian coast conforms to the abundant-center pattern of distribution. However, the coral demographics indicated that this pattern was not only related to the time of establishment but also to differences in coral population growth, which were correlated with key environmental parameters. Our results contribute understanding of the forces driving population growth of O. patagonica and support the hypothesis of an ongoing coral-mediated tropicalization of macroalgae-dominated temperate ecosystems. ; Financial support was provided by project CSI-CORAL (CGL2013-43106- R) of the Spanish Government. The authors are part of the Research Group onMarine Biogeochemistry and Global Change of the Generalitat de Catalunya (2017SGR1011). ; Peer reviewed

1. Sponges play an important ecological function in many benthic habitats. They filter large volumes of water, retain suspended particles with high efficiency and process dissolved compounds. Nevertheless, the factors that regulate sponge pumping rate and its relation to environmental factors have been rarely studied. 2. We examined, in situ, the variation of pumping rates for five Mediterranean sponge species and its relationship to temperature, particulate food abundance and sponge size over two annual cycles. 3. Surprisingly, temperature and food concentration had only a small effect on pumping rates and the seasonal variation of pumping rates was small (1.9-2.5 folds). 4. Sponge size was the main determinant of the specific pumping rate (pumping normalized to a sponge volume or mass). Within the natural size distribution of each species the volume-specific pumping rate (PRV, mL min-1 (cm sponge)-3) decreased (up to 33 folds) with the increase in sponge volume (V, cm3), conforming to an allometric power function (PRV=aVb) with negative exponents. 5. The strong dependence of the size-specific pumping rate on the sponge size suggests that the simplistic use of this value to categorize sponge species and predict their activity may be misleading. For example, for small specimens, size38 specific pumping rates of the two low-microbial-abundance (LMA) species (allometric exponents b of -0.2 and -0.3) were similar to those of two of the high-microbial-abundance (HMA) species (b of -0.5 and -0.7). However, for larger specimens, size-specific pumping rates were markedly different. 6. Our results suggest that the pumping rate of the sponges we studied can be approximated using the measured allometric constants alone in conjunction with surveys of sponge abundance and size distribution. This information is essential for the quantification of in situ feeding and respiration rates, and for estimates of the magnitude of sponge-mediated energy and nutrient fluxes at the community level. 7. Further work is required to establish if and to what extent the low seasonal effect and the strong size dependency of pumping rate can be generalized to other sponges and habitats. ; Financial support was provided by the Spanish Government Grant (RTI2018 -094187-B-100 to RC and MR), EU Project AMARE (Interreg Med Programe 1MED15_3.2_M12_279) and by a FPU fellowship from "Ministerio de Educación, Cultura y Deporte (MECD)" and Max Planck Society to TM. This is a contribution from the Marine Biogeochemistry and Global Change research group from the Generalitat de Catalunya (2017SGR1011) and ISF grant 1280/13 and BSF grants 2012089 and 2017622 to GY. ; Peer reviewed

Este artículo contiene 5 páginas, 2 figuras. ; Knowledge of reproductive biology is essential for ecological studies on coral population dynamics. The azooxanthellate colonial coral Astroides calycularis is endemic to the western Mediterranean Sea and adjacent Atlantic coasts. Specimens of this species in artificial conditions, an aquarium with enclosed seawater and low food availability, appeared to show an asexual dispersal mechanism. This mechanism consisted of the detachment and release of single, skeletonless polyps from the underlying colony skeleton (i.e., polyp bail-out). While the released free-living polyps regularly showed extended tentacles and most of them survived, they did not show re-attachment to the substrate or any skeleton formation until the end of the experiment, ∼2–3 months after bail-out. Formation of new reproductive colonies, thereby the eventual completion of asexual reproduction through polyp bail-out in A. calycularis, still needs to be confirmed. In addition to sexual reproduction, polyp bail-out may constitute an alternative propagation mechanism during periods of environmental stress, thereby potentially increasing the survival rate of the parental genotype and the dispersal by drifting soft polyps. ; Financial support was provided by the CSI-Coral project (CGL2013-43106-R) from the Spanish Government. OS was supported by an ARC DECRA (DE170101524). ES and RC are part of the Marine Biogeochemistry and Global Change research group from the Generalitat de Catalunya (2014SGR1029). ; Peer reviewed

Benthic suspension feeders play essential roles in the functioning of marine ecosystems. By filtering large volumes of water, removing plankton and detritus, and excreting particulate and dissolved compounds, they serve as important agents for benthic-pelagic coupling. Accurately measuring the compounds removed and excreted by suspension feeders (such as sponges, ascidians, polychaetes, bivalves) is crucial for the study of their physiology, metabolism, and feeding ecology, and is fundamental to determine the ecological relevance of the nutrient fluxes mediated by these organisms. However, the assessment of the rate by which suspension feeders process particulate and dissolved compounds in nature is restricted by the limitations of the currently available methodologies. Our goal was to develop a simple, reliable, and non-intrusive method that would allow clean and controlled water sampling from a specific point, such as the excurrent aperture of benthic suspension feeders, in situ. Our method allows simultaneous sampling of inhaled and exhaled water of the studied organism by using minute tubes installed on a custom-built manipulator device and carefully positioned inside the exhalant orifice of the sampled organism. Piercing a septum on the collecting vessel with a syringe needle attached to the distal end of each tube allows the external pressure to slowly force the sampled water into the vessel through the sampling tube. The slow and controlled sampling rate allows integrating the inherent patchiness in the water while ensuring contamination free sampling. We provide recommendations for the most suitable filtering devices, collection vessel, and storing procedures for the analyses of different particulate and dissolved compounds. The VacuSIP system offers a reliable method for the quantification of undisturbed suspension feeder metabolism in natural conditions that is cheap and easy to learn and apply to assess the physiology and functional role of filter feeders in different ecosystems. ; This work was supported by the Spanish Government project CSI-Coral [grant number CGL2013-43106-R to RC and MR] and by a F.P.U fellowship from "Ministerio de Educaciòn, Cultura y Deporte (MECD)" to TM. This is a contribution from the Marine Biogeochemistry and Global Change research group funded by the Catalan Government [grant number 2014SGR1029] and ISF grant 1280/13 and BSF grant 2012089 to G. Yahel. ; Peer reviewed

14 páginas, 5 tablas, 6 figuras. ; Remote sensing of sea surface temperature (SST) is widely used in climate science because it provides a quasi-synoptic coverage of the ocean. However, the use of these data for near-shore habitats is hindered by the proximity of the coast, therefore further investigation is needed. We compared remote-sensing SST from the MODIS sensor (aboard the Aqua satellite) to near-shore seawater temperature (ST) recorded in situ with data loggers at 5 locations in the western Mediterranean Sea. In situ ST data were collected at 5 m depth over a ~6 yr period and at depths below 5 m at 3 of the locations. We evaluated the suitability of MODIS to represent the temperature at shallow subtidal depths relative to different modes of variability. MODIS reproduced seasonal variability with high correlations (r > 0.98) and biases (0.59 ± 0.03°C) only slightly higher than the accuracy of the loggers (0.50°C). MODIS also captured interannual variability with no systematic biases. When evaluated for intra-seasonal temperature variability, MODIS showed limited biases (up to 0.79°C) with a tendency to overestimate the variability (between 4 and 64%) in both cold and warm seasons. Finally, MODIS over-/underestimated only the most extreme unseasonably cold/warm events (by 1.51 and −0.79°C, respectively). The observed limited differences between the 2 methods can be explained by the particular hydro dynamics of the area and by methodological constraints. Overall, MODIS SST data proved to be a reliable proxy for near-shore ST in the western Mediterranean Sea, and are thus considered suitable for studies requiring temperature reconstruction in shallow near-shore environments. ; The study was funded in part by the Spanish Government through CSI-Coral Project (CGL2013- 43106-R). This is a contribution from the Marine Biogeochemistry and Global Change research group funded by the Catalan Government (2014SGR1029). ; Peer reviewed

Corrigendum: In situ Pumping Rate of 20 Marine Demosponges Is a Function of Osculum Area by Morganti, T. M., Ribes, M., Moskovich, R., Weisz, J. B., Yahel, G., and Coma, R. (2021). Frontiers in Marine Science 8: 712856. doi:10.3389/fmars.2021.712856 ; Sponges play a key role in the transfer of energy and nutrients into many benthic ecosystems, and the volume of water they process is an important regulator of these fluxes. Theoretical scaling relationships between sponge volume, osculum cross-sectional area, and pumping rates were recently proposed and confirmed for small sponge specimens in the lab. To examine how these relationships apply to field populations we measured, in situ, the pumping rate (PR) of 20 species representative of different morphologies and host types (high-and low-microbial abundance, HMA and LMA) from temperate and tropical regions. The total oscula area (∑OSA) increased allometrically with sponge volume (V) exhibiting similar exponents (∑OSA=aVb, b ranging 0.6-0.7) for all species, except for tropical HMAs (b= 0.99). Osculum flow rate (OFR) also increased allometrically with OSA and oscula of the same size pumped at the same rate irrespective of sponge volume. As a result, and in contrast to former reports, the PR of most of the sponges increased allometrically (PR=a∑OSAb) with scaling exponent b≈0.75, whereas PR of tropical HMAs increased isometrically. Osculum jet speed declined with the increase in the OSA for most species. The number of oscula and their OSA were the best predictors of the PR in sponges, explaining 75-94% of the in situ variation in PR throughout the natural range of sponge size. The pumping rate of a sponge population can be estimated by measuring the osculum density and cross-sectional area distribution once the relationships between the OSA and OFR are established for each species. ; Financial support was provided by the Spanish Government through the Grant (RTI2018-094187-B-100) and the 'Severo Ochoa Centre of Excellence' accreditation (CEX2019-000928-S), and by the Pure Oceans Foundation Grant 2019-Spoplastics to RC and MR; and by a FPU fellowship from Ministerio de Educación, Cultura y Deporte (MECD) and Max Planck Society to TM. Additional financial support was provided by ISF grant 1280/13 and BSF grants 2012089 and 2017622 to GY. This is a contribution from the Marine Biogeochemistry and Global Change research group from the Generalitat de Catalunya (2017SGR1011). ; Peer reviewed

5 figuras, 3 tablas ; Marine sponges host bacterial communities with important ecological and economic roles in nature and society, yet these benefits depend largely on the stability of host-symbiont interactions and their susceptibility to changing environmental conditions. Here, we investigated the temporal stability of complex host-microbe symbioses in a temperate, seasonal environment over 3 years, targeting sponges across a range of symbiont density (high and low microbial abundance, HMA and LMA) and host taxonomy (6 orders). Symbiont profiling by terminal restriction fragment length polymorphism analysis of 16S rRNA gene sequences revealed that bacterial communities in all sponges exhibited a high degree of host-specificity, low seasonal dynamics and low inter-annual variability: results that represent an emerging trend in the field of sponge microbiology and contrast sharply with the seasonal dynamics of free-living bacterioplankton. Further, HMA sponges hosted more diverse, even and similar symbiont communities than LMA sponges and these differences in community structure extended to core members of the microbiome. Together, these findings show clear distinctions in symbiont structure between HMA and LMA sponges while resolving notable similarities in their stability over seasonal and inter-annual scales, thus providing insight into the ecological consequences of the HMA-LMA dichotomy and the temporal stability of complex host-microbe symbioses. ; This work was supported by the Spanish Government projects MARSYMBIOMICS [grant number CTM2013-43287-P] and CSI-Coral [grant number CGL2013-43106-R to RC and Downloaded from http://femsec.oxfordjournals.org/ by guest on October 1, 2015 18 MR]. This is a contribution from the Marine Biogeochemistry and Global Change research group funded by the Catalan Government [grant number 2014SGR1029]. ; Peer reviewed

Este artículo contiene 11 páginas, 7 figuras, 2 tablas. ; Stochastic perturbations can trigger major ecosystem shifts. Marine systems have been severely affected in recent years by mass mortality events related to positive thermal anomalies. Although the immediate effects in the species demography affected by mortality events are well known, information on the mid- to long-term effects at the community level is much less documented. Here, we show how an extreme warming event replaces a structurally complex habitat, dominated by long-lived species, by a simplified habitat (lower species diversity and richness) dominated by turf-forming species. On the basis of a study involving the experimental manipulation of the presence of the gorgonian Paramuricea clavata, we observed that its presence mitigated the effects of warming by maintaining the original assemblage dominated by macroinvertebrates and delaying the proliferation and spread of the invasive alga Caulerpa cylindracea. However, due to the increase of sediment and turf-forming species after the mortality event we hypothesize a further degradation of the whole assemblage as both factors decrease the recruitment of P.clavata, decrease the survival of encrusting coralligenous-dwelling macroinvertebrates and facilitate the spreading of C. cylindracea. ; Financial support has been provided by a Spanish Ministry Project ANIMA (CGL2016-76341-R), OAPN project (CORCLIM 759S/2012 and 766S/2012) and European Union's Horizon 2020 (grant agreement No. 689518) MERCES Project. This output reflects only the authors' view and the European Union cannot be held responsible for any use that may be made of the information contained therein. J.V. has been funded by a IFUdG2016 grant. Managers of ACNP are acknowledged for sampling permissions. We also thank to David Díaz, Eneko Aspillaga, Pol Capdevila, Bernat Hereu and Fiona Tomas for their collaboration in fieldwork. J.V., C.L. and E.C. are members of the Marine Conservation Research Group (www.medrecover.org; 2017 SGR 1521) and R.C. is part of the Marine Biogeochemistry and Global Change Research Group (2017SGR1011) from the Generalitat de Catalunya. ; Peer reviewed

10 páginas, 7 figuras, 2 tablas. ; In recent years, some of the ramifications of the ocean acidification problematic derived from the anthropogenic rising of atmospheric CO2 have been widely studied. In particular, the potential effects of a lowering pH on tropical coral reefs have received special attention. However, only a few studies have focused on testing the effects of ocean acidification in corals from the Mediterranean Sea, despite the fact that this basin is especially sensitive to increasing atmospheric CO2. In this context, we investigated the response to ocean acidification of the two zooxanthellate coral species capable of constituting the main framework of the community, the endemic Cladocora caespitosa and the non-native Oculina patagonica. To this end, we examined the response of both species to pCO2 concentrations expected by the end of the century, 800 ppm, vs the present levels. Calcification rate measurements after 92 days of exposure to low pH conditions showed the same negative response in both species, a decrease of 32–35% compared to corals reared under control conditions. In addition, we detected in both species a correlation between the calcification rate of colonies in control conditions and the degree of impairment of the same colonies at low pH. Independent of species, faster growing colonies were more affected by decreased pH. After this period of decreased pH, we conducted a recovery experiment, in which corals reared in the acidic treatment were brought back to control conditions. In this case, normal calcification rates were reached in both species. Overall, our results suggest that O. patagonica and C. caespitosa will both be affected detrimentally by progressive ocean acidification in the near future. They do not display differences in response between native and non-native species but do manifest differential responses depending on calcification rate, pointing to a role of the coral genetics in determining the response of corals to ocean acidification. ; Financial support for this study was provided by the Spanish Ministry of Economy and Competitiveness through projects CTM2006-01957/MAR, CTM2009-08849/MAR, CGL2010-18466 and a FPI studentship (BES-2007-16537) to J.M. This work is a contribution from the Marine Biogeochemistry and Global Change research group, funded by Generalitat de Catalunya (Catalan Government) through grant 2009SGR142. [RH] ; Peer reviewed

29 pagex, 9 figures, 2 tables ; The Catalan Sea, located between the eastern Iberian coast and the Balearic Islands, is a representative portion of the western Mediterranean basin and provides a valuable case study for climate change effects on Mediterranean ecosystems. Global warming is reflected regionally by a rise in sea level over the last century, an increase in surface temperature of around 1.1°C in the last 35 yr, a progressive salinisation of intermediate and deep waters and a strengthening of the stratification. A likely scenario of what we can expect in the Mediterranean Sea is a considerable decrease in rainfall and wind, warmer surface waters and a prolonged stratification period. The effects on Mediterranean ecosystems are evident in: (1) a meridionalisation of the algal, invertebrate and vertebrate species, which favours the more thermophilic species over the temperate species; (2) mass mortality events of sessile invertebrates of the coralligenous communities owing to anomalous warm waters during the period when food is scarce; (3) increases in the smallest phytoplankton due to the prolongation of the water stratification period; (4) proliferation of gelatinous carnivores, including jellyfish, due to the temperature rise and the lack of rainfall; (5) a faster acidification of seawater, compared with the global oceans, accompanied by a decrease in the capacity to absorb atmospheric CO2. In order to anticipate and mitigate these predicted changes, we recommend investing in research and observation, conserving areas that serve as indicators of climate change and reducing other anthropogenic pressures such as habitat destruction, overfishing or pollution, which may act synergistically to accelerate these changes. ; E.C., C.P., M.R. and R.C. acknowledge funding from the Spanish Ministerio de Ciencia e Innovación through grants CTM2009-08849/MAR, CTM2006-01463 and CGL2007-66757-C02-01/BOS and a Ramón y Cajal contract to E.C. This paper is a contribution from the Marine Biogeochemistry and Global Change research group, funded by Generalitat de Catalunya (Catalan Government) through grant 2009SGR142. ; Peer reviewed

Estee artículo contiene 14 páginas, 6 figuras. ; Sponges are the oldest known extant animal-microbe symbiosis. These ubiquitous benthic animals play an important role in marine ecosystems in the cycling of dissolved organic matter (DOM), the largest source of organic matter on Earth. The conventional view on DOM cycling through microbial processing has been challenged by the interaction between this efficient filter-feeding host and its diverse and abundant microbiome. Here we quantify, for the first time, the role of host cells and microbial symbionts in sponge heterotrophy. We combined stable isotope probing and nanoscale secondary ion mass spectrometry to compare the processing of different sources of DOM (glucose, amino acids, algal-produced) and particulate organic matter (POM) by a high-microbial abundance (HMA) and low-microbial abundance (LMA) sponge with single-cell resolution. Contrary to common notion, we found that both microbial symbionts and host choanocyte (i.e. filter) cells and were active in DOM uptake. Although all DOM sources were assimilated by both sponges, higher microbial biomass in the HMA sponge corresponded to an increased capacity to process a greater variety of dissolved compounds. Nevertheless, in situ feeding data demonstrated that DOM was the primary carbon source for both the LMA and HMA sponge, accounting for ~90% of their heterotrophic diets. Microbes accounted for the majority (65–87%) of DOM assimilated by the HMA sponge (and ~60% of its total heterotrophic diet) but <5% in the LMA sponge. We propose that the evolutionary success of sponges is due to their different strategies to exploit the vast reservoir of DOM in the ocean. ; This work was funded by the DFG CRC1182-TP B1 "Origin and Function of Metaorganisms" to UH, the Spanish Government grant (RTI2018–094187-B100) and "Generalitat de Catalunya" research group grant (2017SGR1011) to MR and RC, the Netherlands Organization for Scientific Research (NWO-VIDI 864.13.007) to DvO, the European Research Council under the European Union's Horizon 2020 research and innovation programme (Starting Grant 715513) to JMG, and the Swiss Science Foundation Grant (200021_179092) to AM. ; Peer reviewed

Este artículo contiene 5 páginas, 2 tablas, 1 figura. ; Zooxanthellate corals are threatened by climate change but may be able to escape increasing temperatures by colonizing higher latitudes. To determine the effect of host range expansion on symbiont genetic diversity, we examined genetic variation among populations of Symbiodinium psygmophilum associated with Oculina patagonica, a range-expanding coral that acquires its symbionts through horizontal transmission. We optimized five microsatellite primer pairs for S. psygmophilum and tested them on Oculina spp. samples from the western North Atlantic and the Mediterranean. We then used them to compare symbiont genotype diversity between an Iberian core and an expansion front population of O. patagonica. Only one multilocus S. psygmophilum genotype was identified at the expansion front, and it was shared with the core population, which harbored seven multilocus genotypes. This pattern suggests that O. patagonica range expansion is accompanied by reduced symbiont genetic diversity, possibly due to limited dispersal of symbionts or local selection. ; Financial support was provided by the Spanish Government Project CGL2013-43106-R, the Marine Biogeochemistry and Global Change Research Group from ''Generalitat de Catalunya'' (2014SGR1029) (RC and MR) and NSF-OCE–09-26822 (MAC). ; Peer reviewed