ZAC7 Abstracts – Posters

In nature, a multitude of factors influence the fitness of an organism at a given time and their interaction may present synergistic or antagonistic effects on the organism. This study focused on the effects of warming and predation risk stress on the metabolism of an intertidal rock pool fish, the rock goby (Gobius paganellus). In two laboratory-based experiments, the following hypotheses were addressed: (i) the energy metabolism of G. paganellus under predation stress is reduced; (ii) G. paganellus shows thermal compensation under heat stress; and (iii) thermal stress is the dominant stressor that may override predation stress responses. First, oxygen consumption rates of single fish were measured at 20 °C to address the direct response towards simulated predation risk. Individuals were further exposed to simulated predation stress at ambient 20 °C or elevated 29 °C, and biochemical biomarkers related to energy metabolism, oxidative stress, and biotransformation were investigated to identify physiological effects of combined stressors.
The exposure to predation stress induced a significant reduction in oxygen consumption rates compared to routine metabolic rate, indicative for the stereotypic freezing behaviour as antipredator response of gobiid fish. Heat-stressed gobies further revealed thermal compensation mechanisms to resist against unfavourable temperatures, as reflected in decreased aerobic mitochondrial metabolism. Hyperthermia was proven as the dominant stressor overriding the physiological responses to predation stress. Both stressors combined might further have synergistically activated detoxification pathways, even though not strong enough to counteract macromolecular oxidative damage. The synergistic effect of combined thermal and predation stress thus may not only increase the risk of being preyed upon, but also may indicate extra energy trade-off for the basal metabolism, which in turn may have ecologically relevant consequences for general body functions such as somatic growth and reproduction. The present findings underline the ecological importance of multi-stressor assessments to provide a better and holistic picture of physiological responses towards more realistic evaluations of climate change consequences for intertidal populations.

Subterranean estuaries (STEs) are dynamic mixing zones at the land–sea interface, yet their role in the marine lithium (Li) cycle remains poorly quantified. Here we show that a tropical sandy STE at Qiaogang Beach (Beihai, China) functions as an active geochemical reactor that substantially modifies both Li fluxes and isotopic compositions prior to ocean delivery. Dissolved Li in groundwater exhibits clear non-conservative behavior, with ~11% net removal and a resolvable enrichment in δ⁷Li from +29.1‰ to +34.4‰. Sequential extraction reveals that Li is dominantly retained in reactive solid phases, particularly carbonates and Fe oxyhydroxides, which host isotopically light Li. Redox-driven cycling of Fe oxyhydroxides controls Li isotope fractionation within the STE, while carbonate dissolution supplies secondary light Li in freshwater-dominated zones. After correcting for solid-phase retention, freshwater submarine groundwater discharge (FSGD) contributes 1.84 × 10⁶ g Li yr⁻¹ (δ⁷Li = 29.1‰), equivalent to ~17% of the local riverine flux. In contrast, total submarine groundwater discharge delivers 7.56 × 10⁸ g Li yr⁻¹ (δ⁷Li = 30.17‰), exceeding riverine inputs by two orders of magnitude. First-order upscaling indicates that tropical sandy coasts may supply 25–50% of the global FSGD-derived Li flux, exporting isotopically heavy Li to the ocean. These results identify subterranean estuaries as previously unrecognized, quantitatively major, and isotopically distinct sources in the global marine Li cycle.

The ESTiCS project develops an integrated index for monitoring tropical coastal socioecological systems. During the 13th WIOMSA Symposium (Mombasa, Kenya, October 2025), we conducted participatory workshops, key informant interviews (n=15; NGOs, universities, government), and community surveys (n=33). This assessed stakeholder perceptions of coastal zone dynamics, change indicators, interlinkages, existing monitoring frameworks and challenges. Preliminary results reveal divergent stakeholder perceptions of the coastal zone in the Western Indian Ocean (WIO). Communities (mainly fishers/business owners) define it practically as ocean shores, fishing grounds, mangrove forests, beaches, ocean shores, and livelihood hubs (tourism, aquaculture), emphasizing daily-use spaces. However, experts (NGOs, universities, government) describe broader land-sea interfaces (~100 km inland/offshore), integrating ecological connectivity, governance, and ecosystem services. Similarities encompass ocean adjacency and socio-ecological interdependence; differences center on spatial scale and integrity (local vs. systemic). Communities prioritize tourism decline, fish stock reduction, and fishing declines, linked to the loss of mangrove cover, pollution, and climate change. The workshop outcomes will contribute to the development of a preliminary regional indicator set and facilitate the refinement of indicator prioritization and stakeholder engagement strategies. These insights will ultimately strengthen the index’s capacity to inform evidence-based management and policy formulation across the region.

Mahi-mahi (Coryphaena hippurus) is a fast-growing, highly migratory pelagic species widely distributed across tropical and subtropical oceans, including the Eastern Tropical Pacific (ETP). In this region, the species supports predominantly artisanal and small- to mediumscale fisheries that rely mainly on longlines, providing critical livelihoods and export revenues for coastal communities. Mahi-mahi also represents a key international commodity, with the United States as the principal destination for fresh and frozen products. A literature review was conducted to synthesizes peer-reviewed studies and national fisheries statistics reports to provide a comparative assessment of mahi-mahi fisheries in leading producer countries (Peru and Ecuador) and an emerging fishery in Central America (Guatemala). The review integrates ecological and oceanographic drivers of seasonal availability, fleet structure and fishing practices, size selectivity, market orientation (fresh versus frozen exports), and governance and regulatory frameworks. Despite exploiting a shared and highly connected stock, national fisheries exhibit contrasting development pathways. Peru dominates global production, characterized by high volumes and a strong focus on frozen exports, but faces weak regulatory performance and quality constraints. Ecuador emphasizes fresh, high-quality exports supported by more advanced management initiatives, including a National Action Plan and a mature FIP. In contrast, Guatemala operates at smaller scales but holds niche relevance in fresh markets, while facing structural challenges related to juvenile-dominated catches, high levels of informality, and limited regulatory capacity. By consolidating dispersed information into a regional comparative framework, this review establishes a baseline for understanding how structural, market, and governance differences shape uneven performance and vulnerability across ETP mahi-mahi fisheries. The synthesis provides a foundation for future research and comparative assessments of socioecological vulnerability in the regional mahi-mahi fishery.

Mangrove ecosystems are subject to multiple environmental stressors and anthropogenic pressures worldwide. Among the variety of organisms that inhabit these ecosystems, burrowing crabs, also known as ecosystem engineers, dig well-defined burrows and process large quantities of mangrove leaves, which can aerate sediments, provide habitats for microorganisms and accelerate organic matter decomposition. However, increasing pressures related to climate change and human activities could affect their traits and the ecosystem processes they mediate. Here, we gathered data from literature and open-access databases on mangrove burrowing crabs and their traits (e.g., feeding, body size, burrow characteristics, life cycle, movement), then investigated factors which influence their distribution as it is driven by climatic/environmental conditions, and determined the trait expression of species communities along latitudinal gradients in the Atlantic East Pacific (AEP) and Indo-West Pacific (IWP) regions.

With increasing impacts of climate change and declining fishery yields, interest in seaweed aquaculture is growing in Fiji. Species of the genus Caulerpa are particularly promising due to their high market value. In Fiji, these edible seaweeds, locally known as nama, are traditionally harvested from shallow lagoons and reef flats. Rising demand has increased pressure on natural stocks, highlighting the need for sustainable cultivation alternatives. This study evaluated two cultivation approaches for nama: a lagoon-based system using submerged trays deployed at four depths, and a land-based tank system with nutrient enriched trays (TN) and a control treatment (TC) using natural seawater. Because nama growth and morphology are highly sensitive to environmental conditions, the aim was to identify cultivation settings that maximize growth while maintaining desirable quality traits. In Fiji, key quality parameters are frond thickness, ramuli density, and frond coloration. Over four weeks, relative growth rate (RGR), frond thickness, ramuli density, and frond coloration were monitored. In the lagoon experiment, RGR was highest in shallow treatments, reaching 2.16±0.58% day⁻¹, but declined to negative values after week two across all depths, accompanied by biomass disintegration and bleaching. In the land-based experiment, RGR was similar between TN and TC during the first week. In week two, RGR in TC became negative and biomass disintegrated, while TN reached a maximum RGR of 2.03± 0.01% day⁻¹. Despite improved coloration, nutrient enrichment resulted in very thin fronds with low ramuli density and reduced frond production. These findings indicate that nutrient limitation is a major constraint for tray cultivation in lagoon waters and unenriched land-based systems, likely due to the lack of sediment-derived nutrients. Although nutrient enrichment enhanced growth, it also caused unfavorable morphological changes, reducing overall biomass quality. Future research should focus on species identification and optimisation of fertiliser requirements and composition.

The Leibniz Centre for Tropical Marine Research (ZMT) supports compliance with Access and Benefit-Sharing (ABS) requirements under the Nagoya Protocol through a combination of internal advice and a self-developed SQL-based database. The database supports researchers throughout the ABS process and is used to document ABS-relevant information on biological samples, including the storage of related agreements such as Prior Informed Consent (PIC) and Mutually Agreed Terms (MAT), and to link this information to ongoing research activities. In parallel, the ZMT Nagoya advisor benefits from national networking activities, which support the provision of targeted guidance to researchers during project planning, ensuring that ABS obligations are considered early and consistently. Together, the database and advisory support aim to facilitate compliance through transparent documentation and to support the responsible use of genetic resources in line with national and international regulations.

In this study, we adopt a multi-parameter physiological framework to characterize the chronic responses of the Lusitanian toadfish (Halobatrachus didactylus) to simulated climate change conditions. We combine elevated temperature and hypoxia and look at the potential trade-offs between thermal stress, hypoxia tolerance and energetic availability in this fish. By analysing indicators related to metabolism, blood physiology, and systemic stress, our aim is to identify a reduced set of key variables that serve as reliable proxies for whole-organism homeostatic state, thus informing about future ecophysiological assessments and bioindicator development in a context of ongoing environmental change. A total of 48 individuals of H. didactylus were sourced from the coastal lagoon Ria Formosa, in the Algarve region of Portugal, during December 2019 and January 2020. To replicate the conditions of future climate change in Ria Formosa, we employed a combination of high temperature and hypoxia treatments, with their respective controls, producing 4 combinations: High summer temperature and Hypoxia, Low winter temperature and Hypoxia, High summer temperature and Normoxia and finally low winter temperature and Normoxia. The effects of the interaction of temperature and oxygen availability in H. didactylus, under a climate change scenario described in this study produced numerous alterations in its physiology and performance of this species. Warm waters with availability of oxygen were found to be the most deleterious combination of factors. The Lusitanian toadfish, however, was found to reduce the disproportionate energy expenditure arising from warming waters in hypoxic conditions. We found a smaller set of variables that can proxy the overall state of health in this species, namely maximum metabolic rate, standard metabolic rate, blood glucose levels, liver weight, red blood-cells count and hematocrit. The potential use of these variables to summarize the effects of climate change in other species needs to be assessed in future studies.

Coastal communities around the world depend on healthy marine ecosystems for their livelihoods and well-being, yet their perspectives are often missing from the models that inform environmental management and policy. Including local voices in modelling processes is essential for co-producing knowledge that is not only scientifically robust but also grounded in local realities and aligned with relevant decision contexts. Within TropEcS, integrated participatory modelling will be advanced across the core regions through three complementary approaches: (1) co-developing interdisciplinary qualitative network models with local actors to identify drivers, feedbacks, and leverage points in social-ecological systems (fisheries, aquaculture, tourism, and conservation); (2) facilitating futures thinking through community-based drawing and mapping workshops to elicit narratives of desired futures and explore possible pathways of change; and (3) applying Bayesian Belief Networks to integrate diverse knowledge systems and TropEcS model outputs into accessible decision-making tools for data-limited contexts. By embedding local perspectives throughout TropEcS, this work aims to ensure that its outcomes have a positive impact on both coastal communities and the ecosystems they rely on. Chaired by Lol Dahlet, Gustavo Castellanos Galindo and Marie Fujitani