Abstract

The generation and propagation of waves towards the coastal regions during storm events can substantially increase coastal hazards associated with extreme sea levels. While the Mediterranean Sea is characterized by a fetch-limited environment, the progression of extra-tropical cyclones over its surface often engenders powerful waves. As climate numerical models consistently converge towards a global warming climate over the past few decades, the present wave climate is expected to undergo alterations. However, the reliability of the model projections differ among climate variables, exhibiting for instance higher confidence in the temperature than in precipitation variables. This study investigates future changes in the wave climate across the Mediterranean region using an extensive ensemble of wave numerical simulations.

These simulations were forced with wind fields from thirty-one GCM-RCMs (general circulation - regional climate models) of the European Coordinated Regional Climate Downscaling Experiment (EURO-CORDEX), integrating WaveWatch III and SCHISM numerical models. Future changes in the mean and intense (quantile 0.95) wave climate of significant wave height (Hs), peak wave period (Tp), peak wave direction (Dp) are assessed. Furthermore, we evaluate changes in 100-year return levels of Hs toward the end of the century. Extreme events from each GCM-RCM are aggregated into a single coherent distribution, following a bias correction procedure assuming the Cumulative Distribution Function (CDF) of extreme events to adhere to either a parametric Gumbel or Generalized Extreme Value (GEV) CDF, individually for each model. Return levels are then computed by fitting a GEV distribution to the unified distribution for both historical and future periods.

Our findings reveal an intensification of extreme waves towards the end of the century in several areas of the Mediterranean basin. Despite limitations inherent to bias-correction methods and return level computation, our study underscores the contrasting outcomes between analyzing the entire statistical distribution versus focusing solely on the tail, emphasizing the importance of considering both aspects in wave climate projections.

Abstract

The ability of marine bacteria to direct their movement in response to chemical gradients influences inter-species interactions, nutrient turnover, and ecosystem productivity. While natural chemical hotspots produce gradients comprised of hundreds to thousands of different chemical compounds, we do not know how this chemical diversity affects the chemotactic responses of bacteria. I will present results from two studies that reveal some unexpected responses when bacteria are exposed to complex chemical mixtures. Using in situ and laboratory-based assays, we show that marine bacteria are strongly attracted to the abundant algal polysaccharide laminarin, but chemotaxis towards this large molecule is enhanced by dimethylsulfoniopropionate (DMSP), another ubiquitous algal-derived metabolite. Our results indicate that DMSP acts as a methyl donor for marine bacteria, increasing their gradient detection capacity and facilitating their access to polysaccharide patches. Using a novel chemotaxis choice assay, we then directly expose a model marine bacterium to four potent chemoattractants simultaneously (i.e., one monosaccharide and three amino acids). Although the bacterium is strongly chemotactic to each of these molecules in isolation, when these four molecules are provided simultaneously, the cells exhibit a striking response by swimming towards only one of them. These results start shedding light on the synergistic effects (e.g., laminarin and DMSP) and sharp chemical preferences modulating the behaviours of bacteria.

Abstract

Establishing root systems in rhizome fragments of Posidonia oceanica presents a significant challenge for its restoration. Rhizome fragments of this slow-growing seagrass require robust rooting for successful anchorage and nutrient absorption from the environment. Controlled experiments have demonstrated that the use of plant growth regulators, such as the auxins α-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA), stimulates rooting in P. oceanica cuttings. However, this effect has not been tested in a marine environment. In this study, rhizome fragments were exposed to varying concentrations of NAA and IBA for 24 hours before transplanting into a dead matte area in the Bay of Pollensa (Mallorca, Spain). After one year, all fragments survived; however, contrary to expectations, no significant differences emerged in the growth and biomass of roots, rhizomes (orthotropic and plagiotropic), and leaves between treated and untreated fragments. This implies that applying auxins to P. oceanica rhizome fragments may not offer an advantage when rooting transplants in the marine environment. Future studies should explore how other environmental conditions can influence rooting and interactions with auxin effects over time.

Abstract

Seed predation and dispersal play key roles in the regeneration of tropical trees. Seeds may escape pre-dispersal predation when ingested with the fruit pulp and moved away from the parent trees by frugivores. Frugivore species may influence dispersal quality differently even when feeding on the same fruit species. In southern Mexico, we investigated if seed traits (i.e., length, width, and mass) and germination success differed among seeds ingested by howler monkeys (Alouatta pigra), spider monkeys (Ateles geoffroyi), and non-ingested seeds. For this, we recorded the germination rate and percentage of seeds from five tropical tree species, including the following: Ampelocera hottlei , Brosimum lactescens , Dialium guianense, Spondias mombin and Spondias radlkoferi. Furthermore, only for D. guianense we determined if there was a primate selection towards seeds with no insect damaged. Results showed that traits of seeds ingested by howler monkeys differed from those ingested by spider monkeys and non-ingested seeds; while seeds ingested by spider monkeys were similar to non-ingested seeds. Howlers consumed on average the larger seeds. For all five tree species, germination rate was greatest for seeds ingested by howler monkeys. The proportion of damaged seeds declined significantly from non-ingested seeds (48 %), to seeds in spider monkey feces (29 %), and finally to seeds in howler monkey feces (7 %). Fruit selection by primate species influences dispersal quality differently, even when feeding on the same plant species. Howler monkeys may increase the reproductive success of the studied tree species by selecting larger and predation-free seeds/fruits.

Abstract

The Southwestern Atlantic Ocean (SWA), is considered one of the most productive areas of the world, with a high abundance of ecologically and economically important fish species. Yet, the biological responses of this complex region to climate variability are still uncertain. Using 24 years of satellite-derived Chl-a data, the SWA was classified into 9 spatially coherent regions based on the temporal variability of Chl-a concentration, as revealed by SOM (Self-Organizing Maps) analysis. These biogeographical regions were the basis of a regional trend analysis in phytoplankton biomass, phenological indices, and environmental forcing variations. A general positive trend in phytoplankton concentration was observed, especially in the highly productive areas of the northern shelf-break, where phytoplankton biomass has increased at a rate of up to 0.42 ± 0.04 mg m −3 per decade. Significant positive trends in sea surface temperature were observed in 4 of the 9 regions (0.08–0.26 °C decade −1) and shoaling of the mixing layer depth in 5 of the 9 regions (−1.50 to −3.36 m decade −1). In addition to the generally positive trend in Chl-a, the most conspicuous change in the phytoplankton temporal patterns in the SWA is a delay in the autumn bloom (between 15 ± 3 and 24 ± 6 days decade −1, depending on the region). The observed variations in phytoplankton phenology could be attributed to climate-induced ocean warming and extended stratification period. The provided results further evidence of the impact of climate change on these highly productive waters.

Abstract

CyberTracker is a non-profit organization which develops free field data collection software. While Cybertracker software is free of charge, easy to use by a broad range of users due to its simplicity and provides multiple advantages for field data collection in comparison to a manual approach, it is still widely unknown and rarely used. During this talk, I will introduce the software, explain its advantages and applications, the types of hardware available, provide some personal examples of the application during my research and introduce its functioning. Hopefully, the talk will serve for the attendees to understand its potential and consider using this powerful tool that has made my field data collection much easier and efficient and has also improved the quality of the data recorded.

Abstract

Saccharomyces cerevisiae is one of the best studied eukaryotic model organisms. It can alternate between haploid and diploid phases, with lack of nutrients favoring a switch to the haploid phase through a mechanism called sporulation. During sporulation, a single diploid cell generates four haploid daughter cells -a tetrad- which are tightly enclosed within a structure called the ascus. Confinement within the ascus is thought to enforce mating between products of the same meiotic division, minimizing outcrossing in this stage of the life cycle. Therefore, outbreeding has been commonly considered extremely rare in nature. Recent studies, however, have begun to challenge this view by uncovering a surprising ecological niche for the outbreeding of wild yeast: the guts of wasps. Yeast outbreeding in this environment likely involves an interaction between the physicochemical environment of the gut and the biological response of the cells. Preliminary results indicate that ascus breakage results from the combination of physical stresses and enzymatic digestion factors. Mixing due to movement at the gut-level can then promote the formation of multi-strain aggregates and outbreeding. Understanding the natural mechanisms leading to yeast outbreeding in nature will lead us to a better understanding of the S. cerevisiae evolution and adaptation capability. This project is a part of a HFSP grant entitled “The aphrodisiac gut”, in collaboration with research groups specialized in Chemistry from University of Sydney, in Biology from University of Turin and Mathematics from Boston University.