ZAC7 Abstracts – Session 1

Scientific knowledge increasingly informs decisions in complex sustainability contexts, yet it rarely operates alone. Wastewater management provides a clear example of how policy and practice depend on the integration of multiple knowledge systems. With a brief background of knowledge integration as a central challenge in contemporary sustainability science and policy, the talk introduces key concepts related to plural knowledge systems, including scientific knowledge, local ecological knowledge, Indigenous knowledge, practitioner expertise, and regulatory knowledge. Knowledge differs in multifaceted ways, including epistemology, scale, and validation practices. Knowledge compatibility, the conditions under which different knowledge systems can productively inform shared decisions without being reduced to a single dominant framework, is essential to the outcomes of knowledge integration. The talk will describe integration as a relational and political process that shapes whose knowledge is considered credible, actionable, or legitimate. This will be illustrated with empirical examples from project TransTourism, an interdisciplinary project supporting wastewater management in touristic island communities. Wastewater governance provides a compelling case of knowledge integration in practice. Technical models of engineering treatment performance and infrastructure planning interact with place-based understandings of water flows, cultural values attached to water, seasonal dynamics, and downstream ecological impacts. These technical perspectives further interact with experiential knowledge held by system operators, community members, as well as with historical experiences related to water and infrastructure development. These interactions raise questions of knowledge compatibility, including when integration enables more robust and context-sensitive solutions, and when it produces tensions, simplifications, or exclusions. Drawing on these examples, the presentation illustrates the pitfalls of ignoring knowledge integration. In wastewater management, failures of integration can lead to infrastructure that underperforms, generates conflict, or produces unintended ecological and social consequences. The talk concludes by reflecting on recommendations for recognizing knowledge pluralism, and fostering compatibility.

Phytoplankton size structure influences ecosystem function, biogeochemical cycling, and climate. Shifts from large to small cell dominance can occur during ecosystem regime changes, yet the relative importance of bottom-up versus top-down forcing in driving these transitions remains debated. The Cariaco Basin, a coastal upwelling system off the coast of Venezuela, experienced a documented regime shift after 2004, coinciding with the collapse of regional sardine fisheries. During this period, the phytoplankton community shifted from large-cell to small-cell dominance, presenting an opportunity to investigate the mechanisms underlying these changes. We use a size-spectral ecosystem model to disentangle the effects of three potential drivers: nutrient supply (bottom-up), fish grazing pressure on zooplankton (top-down), and zooplankton gross grazing efficiency (reflecting changes in zooplankton community composition). By systematically varying, individually and in combination, the parameters controlling these processes, we identify which mechanisms reproduce the observed size shift. Our factorial modelling approach reveals that the transition to small-cell dominance is primarily driven by the combination of reduced fish pressure on zooplankton and altered zooplankton grazing efficiency, rather than nutrient limitation alone. These findings demonstrate that top-down processes mediated through fisheries-induced trophic cascades can play a dominant role in restructuring plankton communities. Our results highlight the need to consider food web interactions when interpreting phytoplankton community responses to environmental change.

The mangrove ecosystem of the Monterrico Multiple-Use Natural Reserve (RNUMM) constitutes the second largest mangrove complex in Guatemala and plays a critical role in sustaining coastal biodiversity and local livelihoods. However, anthropogenic pressures such as deforestation, unregulated tourism, logging, and agricultural expansion have altered the hydrological functioning of the system, promoting sedimentation processes, modifying mangrove forest productivity, and reducing ecosystem resilience to climate change, ultimately compromising the provision of essential ecosystem services. Effective mangrove restoration requires a detailed understanding of key abiotic drivers. To characterize these processes, monthly monitoring was conducted from February 2024 to February 2025. Litterfall production was evaluated in relation to water physicochemical properties (pH, salinity, redox potential, and temperature). Water samples were collected at both surface and interstitial levels to assess physicochemical conditions, while sediment samples were collected to determine texture, organic matter content, and moisture. Sampling was carried out across three sites within the RNUMM, dominated by Rhizophora mangle (L.) and Laguncularia racemosa (L.) Gaertn. At each site, sampling units were established in areas affected by anthropogenic degradation as well as in relatively conserved mangrove stands. Preliminary results reveal a strong seasonal influence on inundation patterns and physicochemical conditions. Degraded areas exhibited higher environmental stress, particularly during the dry season, which may constrain the natural regeneration of key mangrove species. The pronounced variability of these parameters in degraded zones suggests an altered hydrological balance, with direct implications for both natural and assisted restoration processes. These findings highlight the importance of long-term hydrological monitoring as a foundation for evidence-based mangrove restoration planning and adaptive management, contributing to more effective conservation strategies in the Pacific coastal region of Guatemala.

The zebrafish (Danio rerio) is an established model organism that countless scientists have utilized. However, fame does not automatically translate into the best model. Especially within the field of marine ornamental fish research, there is a noticeable lack of established model organisms. In stark contrast to the highly long-lived False Clown Anemonefish (Amphiprion ocellaris), the goby at the heart of this study possesses an incredibly short generation time of only a few months and is straightforward to maintain. The Masked Goby (Coryphopterus personatus), a roughly 4 cm Caribbean fish, harbors immense potential as a new model species, but a reliable breeding protocol has been absent—until now. During this thesis, established breeding concepts were combined with practical experiences from culturing other goby species and implemented within a Larval Rearing System (LRS). This resulted in a specialized container featuring dark, rounded walls, minimal water supply, an aeration system, and temperature control, providing an optimal environment for growing larvae. Embedded in a custom-built recirculating aquaculture system comprising four of these LRS units, mechanical/biological filtration, and a UV-C clarifier, three egg clutches were successively transferred to the individual tubs for the experiments and raised over 14 days with thrice-daily feeding. Key data documented included the daily larval growth, which averaged an impressive 5.83% per day, and the amount of feed organisms supplied to the larvae. Achieving healthy growth requires a complex feeding chain of live organisms and supplements. The bottleneck here is the production of the microalgae Isochrysis galbana, which is essential for sustaining the copepod Parvocalanus crassirostris, whose nauplii served as the sole food source for the larvae during the first 14 days. Surprisingly, even the very first trial successfully raised a small group of larvae, which not only survived flexion and metamorphosis but also reached sexual maturity and are now ready to produce the F2 generation.