Browsing by Subject "Fish kill"

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    Eutrophication-induced shifts in fish assemblages from a Mediterranean coastal lagoon
    (Elsevier, 2025-10-24) Zamora López, Antonio; Guerrero Gómez, Adrián; Torralva Forero, María del Mar; Zamora Marín, José Manuel; Oliva Paterna, Francisco José; Zoología y Antropología Física; Facultad de Biología
    Eutrophication remains a critical threat affecting estuarine and coastal lagoon ecosystems, largely driven by intensified anthropogenic pressures and exacerbated by climate change. Understanding the impacts of eutrophic processes on biological communities is essential to ensure effective conservation and management of these vulnerable environments. This study investigates the ecological consequences of eutrophication-induced algal blooms and hypoxia-mediated mass mortality events on fish communities in the Mar Menor coastal lagoon (Western Mediterranean Sea). We assessed temporal changes in fish assemblage structure and composition across three different periods: a baseline reference period (2002–2004), an algal bloom period (2018–2019), and a mass mortalities period (2020–2021). For that purpose, multiple community metrics were assessed, including species richness, abundance, biomass, β-diversity, functional guilds, and species dominance. Significant disturbances in fish abundance and biomass in response to critical eutrophic events were found, though species richness remained stable. Community similarity decreased during warmer seasons of eutrophic periods, but β-diversity values remained constant. Species-specific responses highlighted a marked decline of benthic taxa closely associated with bottom habitats, while zooplanktivores and planktivores became dominant, suggesting the emergence of top-down trophic control mechanisms. Additionally, during hypoxic events, large macrobenthivorous species appeared to seek refuge in shallow and more oxygenated areas, thus leading to evident shifts in fish assemblage composition. These findings provide robust evidence of structural and functional disruption in fish assemblages under eutrophic stress conditions. Our study underscores the relevance of long-term biological monitoring and adaptive management strategies in transitional systems, particularly under future climate and nutrient enrichment scenarios.
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    Fish functional responses to eutrophication and mass mortality events in a Mediterranean coastal lagoon
    (Elsevier, 2026-03-23) Zamora López, Antonio; Guerrero Gómez, Adrián; Torralva Forero, María del Mar; Zamora Marín, José Manuel; Herrero-Reyes, Antonio Andres; Guerreiro, Pedro Miguel; Oliva Paterna, Francisco José; Zoología y Antropología Física; Facultad de Biología
    Coastal lagoons are increasingly vulnerable to anthropogenic pressures, with eutrophication emerging as a key driver of ecological degradation. In systems with restricted marine connectivity, understanding how biological communities respond to critical eutrophic events is essential for preserving ecological functions and guiding effective management strategies. This study applies a fish trait-based approach to assess the functional consequences of mass mortality events caused by eutrophication in the Mar Menor coastal lagoon (Western Mediterranean Sea). Based on 588 surveys, we evaluated long-term functional shifts in fish assemblages across three critical eutrophic phases —Pre-Mortality (2018–2019), Mortality (2020−2021) and Post-Mortality (2022−2023)— compared with a reference period (2002–2004). Four functional diversity indices were assessed —functional richness (FRic), specialization (FSpe), originality (FOri), and divergence (FDiv)— and compared their sensitivity with taxonomic metrics and a multi-metric fish index. FSpe and FOri were the most sensitive indices to critical eutrophic events, indicating declines in the uniqueness of traits and ecological functions. Functional homogenization and the loss of specialist taxa were widespread across the lagoon, with minimal influence from site-specific anthropogenic pressure or spatial confinement. These findings suggest limited recovery of ecological functions under and after persistent critical eutrophic conditions. Our study demonstrates the usefulness of incorporating functional diversity metrics to detect and characterize the ecological responses of fish assemblages to eutrophication and mass mortality events in transitional coastal systems.
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    Shallow waters as critical habitats for fish assemblages under eutrophication-mediated events in a coastal lagoon
    (Elsevier, 2023-07-24) Zamora López, Antonio; Guerrero Gómez, Adrián; Torralva Forero, María del Mar; Zamora Marín, José Manuel; Guillén Beltrán, Antonio; Oliva Paterna, Francisco José; Zoología y Antropología Física
    Eutrophication is a major driver of the degradation of transitional waters worldwide, especially in environments with a restricted connection to the sea, such as coastal lagoons. In recent decades, intensive agriculture and urban water inputs around the Mar Menor coastal lagoon (Western Mediterranean) have disturbed this originally oligotrophic aquatic system. The nutrient input into the lagoon has triggered its eutrophication, leading to dystrophic crises and mass mortality events for aquatic biota, transforming it into one of the most eutrophication- impacted transitional waters in the Mediterranean basin. In this study, we applied a fish-based indicator to assess the ecological quality of shallow waters under different eutrophication-mediated environmental stress scenarios (from pre-eutrophic reference periods to critical eutrophic periods), as well as to explore the role of confinement (i.e., water renewal time) and shoreline anthropogenic pressure as factors modulating the indicator response. Despite the high magnitude of the eutrophication impact on the lagoon, the ecological quality of the shallow waters decreased only slightly after the mass mortality events. The level of confinement also had slight effects on the ecological quality of the most confined shallow areas in the summer during eutrophic periods. Hence, shallow waters could play a critical role as refuge habitats, both for fish assemblages and other aquatic taxa, by buffering euxinic conditions during eutrophication processes.”. In fact, shallow waters could act as critical habitats, allowing for the recolonisation of aquatic biota from more impacted areas in the lagoon. This attribute further reinforces the need to properly manage and protect the shoreline areas of transitional waters, particularly under eutrophication scenarios.