Dataset Information

Altered nutrient cycling functionality in seagrass meadows under a simulated future marine heatwave event.

ABSTRACT: Seagrasses are important contributors to environmental nutrient cycling in marine ecosystems and can improve water quality by absorbing excess nitrogen (N). However, these ecosystems are vulnerable to human-mediated pressures, including marine heatwaves (MHWs), particularly those of longer duration. We performed an experiment simulating a 30-d, +5°C intensity MHW to examine the effects on maximum potential N cycling and transformation rates in different system compartments associated with the tropical seagrass Halophila ovalis. Under the MHW, the seagrass exhibited higher ammonium assimilation rates in the leaves, increased respiration rates, and highly variable survival and growth than those at ambient temperature. Contrary to expectations, sediment denitrification rates were lowered under the MHW, reflecting the loss of microbial functions and therefore signifying reduced N removal benefits. Moreover, the lowered seawater total alkalinity under the MHW suggests that the habitat would provide less ocean acidification buffer under future climate change. However, cycling rates in vegetated and unvegetated sediments were not significantly different, showing that the seagrass does not strongly influence the sediment N cycling capacities at this time scale. Our study demonstrates that future MHWs may alter nutrient cycling rates across ecosystem compartments in seagrass meadows, potentially leading to reductions in ecosystem function and services.

SUBMITTER: Bass AV

PROVIDER: S-EPMC12371151 | biostudies-literature | 2025 Sep

REPOSITORIES: biostudies-literature

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Altered nutrient cycling functionality in seagrass meadows under a simulated future marine heatwave event.

Bass Alissa V AV Wang Ziyan Z Chung Nga Man NM So Mandy Wing Kwan MWK Falkenberg Laura J LJ Thibodeau Benoit B

The New phytologist 20250715 6

Seagrasses are important contributors to environmental nutrient cycling in marine ecosystems and can improve water quality by absorbing excess nitrogen (N). However, these ecosystems are vulnerable to human-mediated pressures, including marine heatwaves (MHWs), particularly those of longer duration. We performed an experiment simulating a 30-d, +5°C intensity MHW to examine the effects on maximum potential N cycling and transformation rates in different system compartments associated with the tr ...[more]

PMID: 40665617

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Project description:Seagrass ecosystems, vital as primary producer habitats for maintaining high biodiversity and delivering numerous ecosystem services, face increasing threats from climate change, particularly marine heatwaves. This study introduces a pioneering methodology that integrates Dynamic Bayesian Networks of ecosystem resilience with climate projections, aiming to enhance our understanding of seagrass responses to extreme climate events. We developed cutting-edge metrics for measuring shoot density and biomass in terms of population and site extinction, presented as annual ratios relative to their respective baselines. These metrics include associated uncertainties and projected recovery times. This innovative approach was applied in a case study focusing on Zostera muelleri in Gladstone Harbour, Australia. Utilising five downscaled climate models with a 10 km resolution, our study encompasses a range of Shared Socioeconomic Pathways and emissions trajectories, offering a comprehensive perspective on potential future scenarios. Our findings reveal significant variations in seagrass resilience and recovery times across different climate scenarios, accompanied by varying degrees of uncertainty. For instance, under the optimistic SSP1-1.9 scenario, seagrass demonstrated a capacity for recovery heat stress, with shoot density ratios improving from 0.2 (90% Prediction Interval 0.219, 0.221) in 2041 to 0.5 (90% PI 0.198, 1.076) by 2044. However, this scenario also highlighted potential site extinction risks, with recovery gaps spanning 12 to 18 years. In contrast, the more pessimistic SSP5-8.5 scenario revealed a significant decline in seagrass health, with shoot density ratios decreasing from 0.42 (90% PI 0.226, 0.455) in 2041 to just 0.2 (90% PI 0.211, 0.221) in 2048, and no recovery observed after 2038. This study, through its novel integration of climate models, Dynamic Bayesian Networks, and Monte Carlo methods, offers a groundbreaking approach to ecological forecasting, significantly enhancing seagrass resilience assessment and supporting climate adaptation strategies under changing climatic conditions. This methodology holds great potential for application across various sites and future climate scenarios, offering a versatile tool for integrating Dynamic Bayesian Networks ecosystem models.

Project description:Seagrass meadows are degraded globally and continue to decline in areal extent due to human pressures and climate change. This study used the bio-optical model GrassLight to explore the impact of climate change and anthropogenic stressors on seagrass extent, leaf area index (LAI) and belowground organic carbon (BGC) in St. Joseph Bay, Florida, using water quality data and remotely-sensed sea surface temperature (SST) from 2002 to 2020. Model predictions were compared with satellite-derived measurements of seagrass extent and shoot density from the Landsat images for the same period. The GrassLight-derived area of potential seagrass habitat ranged from 36.2 km2 to 39.2 km2, averaging 38.0 ± 0.8 km2 compared to an observed seagrass extent of 23.0 ± 3.0 km2 derived from Landsat (range = 17.9-27.4 km2). GrassLight predicted a mean seagrass LAI of 2.7 m2 leaf m-2 seabed, compared to a mean LAI of 1.9 m2 m-2 estimated from Landsat, indicating that seagrass density in St. Joseph Bay may have been below its light-limited ecological potential. Climate and anthropogenic change simulations using GrassLight predicted the impact of changes in temperature, pH, chlorophyll a, chromophoric dissolved organic matter and turbidity on seagrass meadows. Simulations predicted a 2-8% decline in seagrass extent with rising temperatures that was offset by a 3-11% expansion in seagrass extent in response to ocean acidification when compared to present conditions. Simulations of water quality impacts showed that a doubling of turbidity would reduce seagrass extent by 18% and total leaf area by 21%. Combining climate and water quality scenarios showed that ocean acidification may increase seagrass productivity to offset the negative effects of both thermal stress and declining water quality on the seagrasses growing in St. Joseph Bay. This research highlights the importance of considering multiple limiting factors in understanding the effects of environmental change on seagrass ecosystems.

Dataset Information

Altered nutrient cycling functionality in seagrass meadows under a simulated future marine heatwave event.

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Altered nutrient cycling functionality in seagrass meadows under a simulated future marine heatwave event.

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