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
02:30 PM
Restoring Coastal Resilience: Adaptive Salt Marsh Restoration Amidst Multiple Stressors (9567)
Primary Presenter: Francesco Peri, University of Massachusetts Boston (francesco.peri@umb.edu)
Coastal systems are increasingly strained by rising sea levels, intensified storm activity, and human interventions, pushing many to the brink of ecological collapse. This study focuses on the salt marsh on the southwest side of Stone Island, part of the Boston Harbor Islands National Recreation Area, which has been severely impacted by the closure of its natural sea opening for road construction. The new opening on the west side has disrupted sediment circulation, threatening marsh productivity and resilience. Preliminary research, including hyperspectral drone surveys, has been conducted to remotely assess the marsh's health. We will present these findings at the conference, along with proposed restoration strategies. These include re-establishing the original opening to improve sediment flow, constructing ridges and runnels to guide sediment to starved areas, and applying thin-layer deposition to counteract sea-level rise. Our work involves continuous current and water level monitoring across multiple tidal cycles, sediment grain size analysis, and marsh grass productivity assessments. We will also design and estimate costs for re-opening the inlet, assess necessary permits, and engage the community in a charrette to co-design the restored salt marsh. These efforts aim to enhance the marsh's ability to adapt to environmental stressors while preserving its ecological and human benefits.
02:45 PM
UNDERSTANDING THE FUTURE OF REEFS WITH CLIMATE CHANGE NATURAL ANALOGUES (9522)
Primary Presenter: Holly Koch, Victoria University of Wellington (hollykoch99@gmail.com)
Anthropogenic climate change is one of the driving forces altering the marine environment. Ocean acidification (OA: low pH) and ocean warming (OW: elevated temperatures) are two major factors affecting calcifying marine organisms such as coralline algae. Coralline algae are an important foundation species and one of the most sensitive taxa to OA and OW. However, select species of coralline algae persist at some naturally low pH/high temperature ecosystems. We hypothesize that species-specific traits enable these coralline algae to survive at such sites. We test this using two reciprocal transplant experiments where multiple coralline algal species from the two natural analogues were collected and transplanted to their respective control and natural analogue sites. Bouraké, New Caledonia is a semi-enclosed lagoon that experiences low pH and high temperatures because of daily tidal shifts. Shikine, Japan is a shallow water carbon dioxide vent that has consistently lower pH while also experiencing tropicalization. Using this approach, we can test potential acclimatization and adaptive processes. We compare the physiological responses of the two reciprocal transplant experiments to assess which species of these important taxa have the potential to acclimatize to future climate conditions (OA and OW). Further analysis will determine the molecular mechanisms responsible.
03:00 PM
ADAPTION OF A LAND USE INTENSITY INDEX (LUIS) TO PREDICT RESPONSES OF ECOSYSTEM FUNCTIONING IN STREAMS (9133)
Primary Presenter: Alina Kindinger, Helmholtz Centre for Environmental Research - UFZ (alina.kindinger@ufz.de)
Intensive agriculture depends heavily on the application of fertilizers and pesticides to increase crop production. However, export of these substances from agricultural areas into surface waters impairs water bodies’ ecological status and ecosystem functions. Prediction of stream ecosystem functioning from land use information is challenging, as it requires knowledge on how spatially distributed agricultural impacts in the catchment are integrated along the stream network to affect in-stream ecosystem functioning. To address this gap, we introduce a novel Agricultural Land-Use Intensity index for Streams (LUIS), designed to quantify and differentiate the multiple stressors that agricultural land use exerts on stream ecosystems. LUIS integrates grid-level information on fertilizer and pesticide use with hydrological connectivity to assess agricultural stressors at the sub-catchment scale, accounting for long-range impacts. To connect LUIS with trophic transfer efficiency (TTE) as a proxy for ecosystem functioning, we conducted a large sampling campaign in the Harz mountains in Saxony-Anhalt (Germany), across 20 different streams spanning a LUIS gradient. By analyzing the shape of the stressor-response relationship, we aim to reveal potential thresholds in land use intensity where ecosystem functionality may experience abrupt changes, shifting outside sustainable safe operating spaces. This approach provides a quantitative assessment of LUIS-function relationships, highlighting critical points where agricultural pressures could induce significant shifts in ecosystem performance.
03:15 PM
Treatment with Nitrate and Oxygen Improves Water Quality of Contaminated Urban Lakes (9811)
Primary Presenter: Robin Burgold, TU Berlin (robin-burgold@web.de)
The ecological status of two eutrophic urban lakes has dramatically improved following a treatment with calcium nitrate and oxygen-enriched water. These lakes were affected by decades of nutrient and pollutant loading from stormwater runoff. The intervention suppressed the release of legacy phosphorus from sediments and reduced phosphate in the bottom water by over 80% in both lakes within one year. With the start of the treatment, nitrate (NO3) levels temporarily increased in the bottom water, but returned to drinking water standards within a month when no further NO3 was added. No leaching of NO3 to the aquifer below the lake was detected. DOC levels in the pore water declined during the treatment, indicating heterotrophic denitrification took place. Simultaneously, sulfate increased in the bottom water, hydrogen sulfide production was inhibited, and oxygen levels increased throughout the water column, alleviating the anoxic conditions prior to the treatment. Although Microcystis was detected in the sediment of one lake, no microcystin was detected in either lake. This contradicts the concept that reducing phosphorus without reducing nitrogen leads to an increase in microcystin concentrations. Although the sediments contained high concentrations of lead (Pb) and other metals, no increase above drinking water limits was observed during or after the treatment. This is in contrast to previous lab-scale studies, suggesting remediation based on NO3 and oxygen leads to Pb mobilization. Analysis of the sediment microbial communities reflected a reduction in the relative abundance of sulfate reducers and methanogens induced by the treatment. NO3 is often considered a pollutant. We show that its controlled addition to lakes resulted in a clear improvement in water quality. The treatment shows great promise as a practical, field-scale tool for remediating lakes impacted by urban pollution and constant inputs of excess nutrient.
SS42B - Abrupt Changes in Aquatic Ecosystems: Impacts of Anthropogenic Stressors
Description
Time: 2:30 PM
Date: 27/3/2025
Room: W205CD