Abstract

Sunlight drives virtually all life on the Earth’s surface, with about 50% of primary productivity occurring in marine systems. Yet, this traditional view of phototrophy changed radically with the discovery of marine bacterial rhodopsins (i.e., proteorhodopsins; PR), over twenty years ago. PRs are simple light-driven proton pumps present in over 80% of surface bacterioplankton, which allow them to transform light into biochemical energy.

Combining culture-based physiology studies with (meta)-genomics, (meta)-transcriptomics, and environmental quantifications we are just starting to understand the role that PR-based photoheterotrophy plays in the ocean. In this presentation, I will discuss the knowns and unknowns of PR-phototrophy and what we are starting to learn from looking at its natural distributions in different oceanographic basins, ranging from extreme ultraoligotrophic regions to high productivity environments

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.

INTERNATIONAL VISITING SCHOLAR PROGRAMME (IVSP)

Abstract

Seagrass meadows and the services they provide are declining worldwide as a result of human perturbations. Along the Swedish W coast, almost 60% of the seagrass has been lost since the 1980's, representing a loss of approximately 190 km2 of seagrass. The seagrass Zostera marina, L. (eelgrass) is the dominant macrophyte on soft bottoms along the Swedish coast. The decrease in seagrass worldwide has lead to many restoration programs but their success rate is very low due to the regime shift and feedback mechanisms that also prevent natural recovery.

This presentation aims to provide a review on the restoration successes and challenges on eelgrass in Sweden. For example, positive feedbacks generated by water turbidity due to sediment resuspension, drifting macroalga covering eelgrass transplants and the presence of eelgrass predators such as shore crabs have been identified as causes affecting restoration success. To overcome these issues, restoration techniques using sand-capping have shown to be successful to reintroduce eelgrass in areas where it was lost. An interdisciplinary approach using field and laboratory experiments linked with hydrodynamical modeling showed to be key to understand the complex coastal ecological dynamics.

In addition, new methods to monitor coastal habitats such as seagrass meadows and marine mammals (dugongs and seals) using aerial drones and machine learning will be presented. These new technologies can contribute to faster data collection and data analysis for ecological studies and to provide relevant information to coastal managers and decision makers working on ecological conservation.

Bio

Eduardo Infantes is a researcher at the University of Gothenburg in Sweden, where he leads the Seagrass Ecology Lab research group  based at Kristineberg marine station. With a focus on seagrass ecology over the last 18 years, his main interests are in 1) studying interactions between fluid dynamics and marine vegetation through field data, mesocosm experiments and flume studies, 2) restoration of coastal habitat using seagrass within the interdisciplinary ZORRO group, and 3) monitoring of seagrass beds and marine mammals (e.g. harbor seals, manatees, and dugongs) using drones and AI. With an interdisciplinary profile, he collaborates in research and management, contributing to environmental policies in coastal restoration and monitoring.

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.