Dr. Urzúa-Osorio, Ángel

The physical-chemical variability of coastal upwelling creates a mosaic of environmental conditions that affect different levels of biological organization. Understanding the mechanisms that organisms use to cope with this variability is critical for addressing the challenges that climate change imposes on coastal ecosystems. This study integrates information on transcriptomic traits, metabolic performance, and the quantity of organic biomolecules in the intertidal fish Girella laevifrons from four locations with varying upwelling intensities. The results show that fish from locations with stronger upwelling intensity have higher levels of glucose, lipids, and proteins in their muscle tissue, in addition to better physiological performance compared to fish from sites with weaker upwelling intensity. Transcriptomic analyses revealed that genes associated with multicellular development and oxygen metabolism are more highly expressed in sites with stronger upwelling intensity, whereas genes related to protein ubiquitination are more expressed in sites with weaker upwelling intensity. In response to the mosaic of upwelling intensities (SAM-SST), and in-situ temperature, nutrients and oxygen variation observed in field, fish showed differential responses, suggesting local adaptations process that maximize ecological success in these areas with different physical-chemical conditions. Future studies should consider the integration of molecular tools to better understand the responses of organisms to environmental variability as upwelling intensities. This will help elucidate the complex interactions between environmental factors and biological responses, providing insights into how marine organisms might adapt to changing conditions. Understanding these mechanisms is essential for predicting the impacts of climate change on coastal ecosystems and for developing effective conservation and management strategies. The integration of transcriptomic data with metabolic and physiological performance measures offers a comprehensive approach to studying the adaptive responses of marine organisms to their dynamic environments considering the future responses in face to predict global change.

Upwelling oceanographic phenomenon is associated with increased food availability, low seawater temperature and pH. These conditions could significantly affect food quality and, in consequence, the growth of marine species. One of the most important organismal traits is somatic growth, which is highly related to skeletal muscle. In fish, skeletal muscle growth is highly influenced by environmental factors (i.e. temperature and nutrient availability) that showed differences between upwelling and downwelling zones. Nevertheless, there are no available field studies regarding the impact of those conditions on fish muscle physiology. This work aimed to evaluate the muscle fibers size, protein content, gene expression of growth and atrophy-related genes in fish sampled from upwelling and downwelling zones. Seawater and fish food items (seaweeds) samples were collected from upwelling and downwelling zones to determine the habitat's physical-chemical variations and the abundance of biomolecules in seaweed tissue. In addition, white skeletal muscle samples were collected from an intertidal fish to analyze muscular histology, the growth pathways of protein kinase B and the extracellular signal-regulated kinase; and the gene expression of growth- (insulin-like growth factor 1 and myosin heavy-chain) and atrophy-related genes (F-box only protein 32 and muscle RING-finger protein-1). Upwelling zones revealed higher nutrients in seawater and higher protein content in seaweed than samples from downwelling zones. Moreover, fish from upwelling zones presented a greater size of muscle fibers and protein content compared to downwelling fish, associated with lower protein ubiquitination and gene expression of F-box only protein 32. Our data indicate an attenuated use of proteins as energy source in upwelling conditions favoring protein synthesis and muscle growth. This report shed lights of how oceanographic conditions may modulate food quality and fish muscle physiology in an integrated way, with high implications for marine conservation and sustainable fisheries management.

Upwelling systems deliver nutrient-rich water into coastal ecosystems, influencing primary productivity and potentially altering seaweed-herbivore interactions. Upwelling bottom-up effects on distinct trophic levels are wellknown. However, their influence on seaweed biomolecules and on algae-herbivore interactions and growth are less known. The aim of this study was threefold: i) to compare physical-chemical characteristics and nutrient levels in the water of upwelling (U) and downwelling (DU) zones, ii) to quantify their influence on the content of protein and carbohydrates in seaweed tissues of representative U and DU locations, and iii) to experimentally assess their effect on the feeding behavior and growth of a prominent intertidal herbivore, the sea urchin Loxechinus albus. Waters from U zones showed lower temperatures and pH, and higher phosphate concentrations than those from downwelling zones. Similarly, the tissue of seaweeds from a U location had significantly more proteins and carbohydrates than those from a DU location. The origin location of the sea urchins had a significant influence on consumption and growth rates: in general, those coming from a site with U conditions consumed and grew more than those coming from DU conditions. The quality of the algae was a significant factor on consumption rates, although in the case of preference trials, this factor interacted with sea urchin origin location. Our results show that the availability and quality of the food in upwelling zones has an influence on herbivore-seaweed direct interactions. However, these interactions and the growth of the sea urchins were also related to the coastal site and conditions from which the sea urchins came from. These results are relevant considering the expected impact of climate change on the world's oceans, and the importance of U zones as thermal (cold water) refuges for marine ectotherms.