Aquatic ecosystems worldwide are facing unprecedented stress from anthropogenic activities and climate change. This session explores the question: How are aquatic ecosystems responding to these pressures, and have they experienced abrupt changes in their ecological states? Abrupt changes, defined as sudden and significant transitions between distinct ecological conditions, can manifest as smooth, threshold-like, or bistable changes, altering ecosystem structure and function. We invite contributions that use paleo records, contemporary research, or models to explore or assess these abrupt changes across diverse aquatic environments. The session will focus on deepening the understanding of climate influences, ontogenetic processes, and/or anthropogenic impacts on driving these abrupt changes. Additionally, we welcome research on ecosystem resilience, referring to the capacity of systems to withstand or adapt to stress, including the ability to maintain core functions despite undergoing abrupt changes. Given the current lack of knowledge on recovery following such changes, we are particularly interested in exploring whether ecosystems can rebound or stabilize after these significant transitions. We also invite contributions on remediation efforts and strategies aimed at managing or mitigating the impacts of abrupt changes to preserve ecosystem function.

Lead Organizer: Skylar Hooler, university at Albany (Shooler@albany.edu)

Co-organizers:

Aubrey Hillman, University at Albany (ahillman@albany.edu)

Presentations

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06:00 PM

EXPLORING THE INTERPLAY BETWEEN NUTRIENT AND LIGHT AVAILABILITY ON EELGRASS PHYSIOLOGY (8969)

Primary Presenter: Lauriane Belles-Isles, Université du Québec à Rimouski (laurianebellesisles@gmail.com)

Cumulative human activities are increasing nutrient inputs in coastal zones, driving eutrophication, and harming key ecosystems like eelgrass meadows. In excess, nitrogen promotes faster-growing primary producers that can outcompete eelgrass for nutrients and light. However, the combined effects of these two factors on eelgrass health—especially across a broad range of environmental conditions—are still overlooked. To address this gap, we conducted a laboratory experiment to assess the single and combined effects of nutrient and light availability on the widely distributed eelgrass (Zostera marina L.). In August 2024, eelgrass cores were collected from Rimouski Bay (QC, Canada) and placed in a nearby open-flow system. Following a one-week acclimation, the cores were randomly exposed to 2 nutrient levels (ambient and enriched) and 8 light intensities (ranging from 6 to 965 μmol photons m^-2 s^-1),  with 3 replicates per crossed condition. Eelgrass photosynthetic traits, including F_v/F_m and Rapid Light Curves, were monitored using non-invasive PAM fluorometry. After a two-week exposure, leaf chlorophyll a concentration was measured on 9 shoots per crossed condition. Preliminary results reveal that eelgrass shoots can be grouped based on their response to light availability. Moreover, nutrient enrichment seems to enhance their photosynthetic capacity. By combining gradient-based and multi-stressor approaches, this study will provide insights into potential thresholds in eelgrass responses to nutrient and light stress.

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06:00 PM

QUANTIFYING DYNAMIC HABITAT USE OF THE NORTH ATLANTIC RIGHT WHALE USING AN INDIVIDUAL MOVEMENT MODEL (9254)

Primary Presenter: Abigail Kreuser, University of South Carolina (akreuser@seoe.sc.edu)

Rapid warming in the Northwest Atlantic has caused declines of North Atlantic right whale prey, late-stage Calanus finmarchicus, in their historic and protected foraging areas. This led to a rapid redistribution of right whale foraging patterns, and their unexpected presence in new habitats increased mortality rates due to ship strikes and gear entanglement. Annual distribution and birth rates have been linked to fluctuations in the abundance of prey; however, patterns of individual foraging behavior and reproductive success in relation to changes in their environment have not been investigated. The population has been monitored since 1980, and individuals can be identified by unique callosities and markings. Tracks were created using consecutive sightings of known individuals from 1977-2022 that were no more than 30 days apart (sightings = 57,216; tracks = 12,032). A Brownian bridge movement model was applied to quantify potential habitat use for each track incorporating movement variance and time in between sightings. Daily distributions were produced for each modeled individual and summed to show population trends of peak abundance and seasonal patterns in habitat regions. The modeled habitat distributions provide insight into how individual health and behavior scale to population level response in a changing environment.  These methods improve spatial distribution predictions in intermittently observed animals beyond stationary sightings, and could be applied to other species confined to movement in bodies of water over various spatial and temporal scales. 

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