Long-Term Eelgrass Habitat Change and Associated Human Impacts on the West Coast of Canada

Nahirnick, Natasha K.; Costa, Maycira; Schroeder, Sarah; Sharma, Tara

doi:10.2112/jcoastres-d-18-00112.1

Cited by 17 publications

(9 citation statements)

References 53 publications

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“…While federal legislation relevant to seagrass protection may consider CE (Modernized Fisheries Act Bill C-68 section 34.1(1)(d)), there has been little focus on quantifying the magnitude of CE specific for seagrass habitats. Previous assessments have quantified the magnitude of a suite of human activities occurring in or near seagrass beds in Canada, yet none of these have combined the extent of human activities using a CE approach (Robb 2014;Iacarella et al 2018;Murphy et al 2019;van den Heuvel et al 2019;Nahirnick et al 2020;Nagel et al 2021). Assessing human activities within seagrass beds and seagrass inhabited bays from a CE perspective would provide an overall representation of human impacts that accounts for differences in seagrass vulnerability to different activities and stressors.…”

Section: Introductionmentioning

confidence: 99%

Incorporating anthropogenic thresholds to improve understanding of cumulative effects on seagrass beds

Murphy

Kelly

Lotze

et al. 2022

FACETS

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Cumulative human impact analysis is a promising management tool to estimate the impacts of stressors on ecosystems caused by multiple human activities. However, connecting cumulative impact scores to actual ecosystem change at appropriate spatial scales remains challenging. Here, we calculated cumulative effects (CE) scores for 187 seagrass beds in Atlantic Canada that accounts for both bay-scale and local-scale anthropogenic activities. We then developed a CE threshold to evaluate where degradation of seagrass beds from multiple human activities is more likely. Overall, the CE score was the best predictor of human impacts for seagrass beds. Locations with high watershed land alteration and nitrogen loading had the highest CE scores; however, we also identified seagrass beds with high CE scores in regions characterized by generally low levels of human activities. Forty-nine seagrass beds exceeded the CE threshold and, of these, 86% had CE scores that were influenced by three or more stressors that cumulatively amounted to a large score. This CE threshold approach can provide a simplified metric to identify areas where management of cumulative effects should be prioritized and further highlights the need to consider multiple human activities when assessing anthropogenic impacts to coastal habitats.

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Section: Introductionmentioning

confidence: 99%

Incorporating anthropogenic thresholds to improve understanding of cumulative effects on seagrass beds

Murphy

Kelly

Lotze

et al. 2022

FACETS

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“…Indeed, numerous studies indicate that eelgrass meadow extent varies across time, often driven by natural and human-influenced environmental changes (e.g. Lyons et al 2013, Dumbauld & McCoy 2015, Patrick & Weller 2015, Shelton et al 2017, Nahirnick et al 2020. What has yet to be determined and regionally synthesized, however, is the near-term (one to several years) potential for eelgrass meadows to expand away from occupied areas into unoccupied areas.…”

Section: Introductionmentioning

confidence: 99%

Northeast Pacific eelgrass dynamics: interannual expansion distances and meadow area variation over time

Munsch

Beaty

Beheshti

et al. 2023

Mar. Ecol. Prog. Ser.

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Ecosystems constantly change, yet managers often lack information to move beyond static habitat assumptions. As human impacts and geographic information systems advance, it is important and feasible to quantify past habitat boundary shifts to inform management decisions (e.g. protective perimeters) robust to near-term habitat changes. This is the case in eelgrass (Zostera spp.), an ecosystem engineer that forms dynamic, often protected meadows. Practitioners protect areas to avoid human stress to eelgrass, but they can lack quantitative descriptions of the near-term potential for eelgrass meadows to shift into unprotected areas. Here, we quantified interannual eelgrass meadow boundary shifts within 23 sites spanning 9 decades and 19° latitude. Eelgrass meadow boundaries typically shifted into areas tens of meters away from previous meadow edges, but sometimes much farther. Also, eelgrass meadows often vacated and later recolonized the same areas. By implication, eelgrass protection efforts may be enhanced by considering that presently vacant areas may be inhabited in the future, especially near currently existing meadows. Additionally, eelgrass meadows changed less over time at sites less modified by people within temperate landscapes compared to sites located within human-dominated, warmer, and drought-prone landscapes with limited water turnover. We thus hypothesize that eelgrass meadows change more over time within landscapes exposed to greater stressor regimes because they more frequently or intensely cycle through disturbance and recovery phases. These results inform tactical decisions seeking to mitigate impacts of human activities to eelgrass and underscore the potential synergy of monitoring, research, and adaptive management approaches to protect dynamic habitats.

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“…4.5 Future Perspectives on Land-Ocean Connectivity in the NPCTR Across the NPCTR, climate change is predicted to fundamentally alter the connection between land and the coastal ocean by amplifying seasonal contrasts through increased winter but reduced summer rainfall (Radić;Bidlack et al, 2021), increased landslide occurrence (Jakob and Lambert, 2009;Sobie, 2020), enhanced glacial melt in the near term but reduced glacial inputs in the longer term (Bliss et al, 2014;Huss and Hock, 2018), and greater incidence and severity of extreme marine and terrestrial heatwaves Frölicher and Laufkötter, 2018;Perkins-Kirkpatrick and Lewis, 2020). On top of these changes, we must also consider the effects that logging and other land use practices have on the connection between land and the coastal ocean (e.g., via impacts on slope stability and the accumulation of woody debris under estuarine log storage areas; Sedell et al, 1991;Nahirnick et al, 2019). The ecological consequences of these changes and activities for the base of coastal food webs are poorly understood, but may include changing phytoplankton (Jackson et al, 2015) and macrophyte community composition and productivity (Murphy et al, 2021) and changes in the composition and amount of watershed-derived POM being exported to the coast (Hood et al, 2020).…”

Section: Fate Of Pom In Surface Waters Of the Npctrmentioning

confidence: 99%

Seasonally and Spatially Variable Organic Matter Contributions From Watershed, Marine Macrophyte, and Pelagic Sources to the Northeast Pacific Coastal Ocean Margin

et al. 2022

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Globally, coastal waters are considered biogeochemical hotspots because they receive, transform, and integrate materials and waters from both land and the open ocean. Extending from northern California to southeast Alaska, the Northeast Pacific Coastal Temperate Rainforest (NPCTR) region is no exception to this, and hosts a diversity of watershed types (old-growth rainforest, bog forest, glaciers), and tidal (sheltered, exposed) and pelagic marine (deep fjord, shallow estuary, well-mixed channel) environments. With large freshwater fluxes to the coastal ocean, cross-ecosystem connectivity in the NPCTR is expected to be high, but seasonally variable, with pulses in runoff from rainfall, snowmelt and glacial melt, and primary production associated with changes in ocean upwelling and incident light. However, the relative contribution of each ecosystem to surface ocean organic matter pools over time and space remains poorly constrained, despite their importance for the structure and function of coastal marine ecosystems. Here, we use a four-year dataset of particulate organic matter (POM) chemical composition (δ13C, δ15N, C:N ratio) to quantify the relative contributions of watershed materials via riverine inputs, marine phytoplankton, and macrophytes (macroalgae and seagrass) to surface waters (0-10 m) at 11 stations representing fjord, shallow non-fjord estuary, sheltered channel and well-mixed coastal environments at the heart of the NPCTR in British Columbia, Canada. Watershed, marine phytoplankton, and macrophyte contributions to surficial POM ranged between 5-78%, 22-88%, and 0.1-18%, respectively, and varied by season and station. Watershed inputs were the primary source of POM across all stations in winter and were important throughout the year within the fjord. Marine phytoplankton were the principal source of POM in spring and at all stations outside of the fjord through summer and autumn, while macrophyte contributions were greatest in summer. These results demonstrated high, but seasonally and spatially variable, connectivity between ecosystems that are often considered in isolation of one another and highlight the need to consider coastal waters as integrated land-ocean meta-ecosystems. Future work should investigate how heterogeneity in POM sources determines its fate in coastal ecosystems,and the relative importance of different basal organic matter sources for the marine food web.

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Long-Term Eelgrass Habitat Change and Associated Human Impacts on the West Coast of Canada

Cited by 17 publications

References 53 publications

Incorporating anthropogenic thresholds to improve understanding of cumulative effects on seagrass beds

Incorporating anthropogenic thresholds to improve understanding of cumulative effects on seagrass beds

Northeast Pacific eelgrass dynamics: interannual expansion distances and meadow area variation over time

Seasonally and Spatially Variable Organic Matter Contributions From Watershed, Marine Macrophyte, and Pelagic Sources to the Northeast Pacific Coastal Ocean Margin

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