Sea wrack delivery and accumulation on islands: factors that mediate marine nutrient permeability

Sea wrack provides an important vector of marine-derived nutrients to many terrestrial environments. However, little is known about the processes that facilitate wrack transport, deposition, and accumulation on islands. Three broad factors can affect the stock of wrack along shorelines: the amount of potential donor habitat nearby, climatic events that dislodge seaweeds and transfer them ashore, and physical characteristics of shorelines that retain wrack at a site. To determine when, where, and how wrack accumulates on island shorelines, we surveyed 455 sites across 101 islands in coastal British Columbia, Canada. At each site, we recorded wrack biomass, species composition, and shoreline biogeographical characteristics. Additionally, over a period of 9 mo, we visited a smaller selection of sites (n = 3) every 2 mo to document temporal changes in wrack biomass and species composition. Dominant wrack species were Zostera marina, Fucus distichus, Macrocystis pyrifera, Nereocystis luetkeana, Pterygophora californica, and Phyllospadix spp. The amount of donor habitat positively affected the presence of accumulated biomass of sea wrack, whereas rocky substrates and shoreline slope negatively affected the presence of sea wrack biomass. Biomass was higher during winter months, and species diversity was higher during summer months. These results suggest that shorelines with specific characteristics have the capacity to accumulate wrack, thereby facilitating the transfer of marine-derived nutrients to the terrestrial environment

Equivalent roles of marine subsidies and island characteristics in shaping island bird communities

AimSpecies distributions across islands are shaped by dispersal limitations, environmental filters and biotic interactions but the relative influence of each of these processes has rarely been assessed. Here, we examine the relative contributions of island characteristics, marine subsidies, species traits, and species interactions on avian community composition.LocationCentral Coast region of British Columbia, Canada.TaxonTerrestrial breeding birds.MethodsWe observed 3610 individuals of 32 bird species on 89 islands that spanned multiple orders of magnitude in area (0.0002–3 km$^{2}$). We fit a spatially explicit joint species distribution model to estimate the relative contributions of island physical characteristics, island‐specific inputs of marine subsidies, species' traits, and biotic interactions on species distributions. Biogeographic characteristics included island area, isolation, and habitat heterogeneity, while marine influence was represented by forest‐edge soil δ$^{15}$N, wrack biomass, shoreline substrate, and distance to shore. This approach also allowed us to estimate how much variation in distributions resulted from species' biological traits (i.e. body mass, feeding guild, feeding height, and nesting height).ResultsBird species distributions were determined almost equivalently by island biogeographic characteristics (23.5% of variation explained) and marine influence (24.8%). We detected variation in species‐specific responses to both island biogeographic characteristics and marine influence, but no significant effect of any biological trait examined. Additionally, we found evidence that habitat preferences were a more important driver than competitive interactions.Main ConclusionsAlthough most island biogeographic studies focus only on islands' physical characteristics, we found evidence for an equivalent role of marine subsidy in structuring island bird communities. Our study suggests that for small islands, disentangling the effects of island biogeographic characteristics, marine inputs, and biotic interactions is a useful next step in understanding species distributions

Low-Altitude UAV Imaging Accurately Quantifies Eelgrass Wasting Disease From Alaska to California

Declines in eelgrass, an important and widespread coastal habitat, are associated with wasting disease in recent outbreaks on the Pacific coast of North America. This study presents a novel method for mapping and predicting wasting disease using Unoccupied Aerial Vehicle (UAV) with low-altitude autonomous imaging of visible bands. We conducted UAV mapping and sampling in intertidal eelgrass beds across multiple sites in Alaska, British Columbia, and California. We designed and implemented a UAV low-altitude mapping protocol to detect disease prevalence and validated against in situ results. Our analysis revealed that green leaf area index derived from UAV imagery was a strong and significant (inverse) predictor of spatial distribution and severity of wasting disease measured on the ground, especially for regions with extensive disease infection. This study highlights a novel, efficient, and portable method to investigate seagrass disease at landscape scales across geographic regions and conditions

Biogeographic features mediate marine subsidies to island food webs

Although marine subsidies often enrich terrestrial ecosystems, their influence is known to be context-dependent. Additionally, the multitrophic impact of marine subsidies has not been traced through food webs across physically diverse islands. Here, we test predictions about how island characteristics can affect marine enrichment of food web constituents and how nutrients flow through island food webs. To evaluate enrichment and trace marine nutrients across food webs, we used stable isotopes of soil, flora, and fauna (n = 4752 samples) collected from 97 islands in British Columbia, Canada. Island area was the strongest predictor of enrichment across taxa; we found that samples were more 15N-rich on smaller islands. Enrichment declined with distance from shore but less so on small islands, implying a higher per-unit-area subsidy effect. These area and distance-to-shore effects were taxon-specific, and nearly twice as strong in basal food web groups. We also found that increases in δ15N correlated with increases in %N in basal trophic groups, as well as in songbirds, implying biologically relevant uptake of a potentially limiting nutrient. Path analysis demonstrated that subsidies in soil flow through plants and detritivores, and into upper-level consumers. Our results reveal an interplay between island biogeography and marine subsidies in shaping island food webs through bottom-up processes

A review of the opportunities and challenges for using remote sensing for management of surface-canopy forming kelps

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Cavanaugh, K. C., Bell, T., Costa, M., Eddy, N. E., Gendall, L., Gleason, M. G., Hessing-Lewis, M., Martone, R., McPherson, M., Pontier, O., Reshitnyk, L., Beas-Luna, R., Carr, M., Caselle, J. E., Cavanaugh, K. C., Miller, R. F., Hamilton, S., Heady, W. N., Hirsh, H. K., Hohman R., Lee L. C., Lorda J., Ray J., Reed D. C., Saccomanno V. R., Schroeder, S. B. A review of the opportunities and challenges for using remote sensing for management of surface-canopy forming kelps. Frontiers in Marine Science, 8, (2021): 753531, https://doi.org/10.3389/fmars.2021.753531.Surface-canopy forming kelps provide the foundation for ecosystems that are ecologically, culturally, and economically important. However, these kelp forests are naturally dynamic systems that are also threatened by a range of global and local pressures. As a result, there is a need for tools that enable managers to reliably track changes in their distribution, abundance, and health in a timely manner. Remote sensing data availability has increased dramatically in recent years and this data represents a valuable tool for monitoring surface-canopy forming kelps. However, the choice of remote sensing data and analytic approach must be properly matched to management objectives and tailored to the physical and biological characteristics of the region of interest. This review identifies remote sensing datasets and analyses best suited to address different management needs and environmental settings using case studies from the west coast of North America. We highlight the importance of integrating different datasets and approaches to facilitate comparisons across regions and promote coordination of management strategies.Funding was provided by the Nature Conservancy (Grant No. 02042019-5719), the U.S. National Science Foundation (Grant No. OCE 1831937), and the U.S. Department of Energy ARPA-E (Grant No. DE-AR0000922)

Kelp-O-Matic

What's Changed <ul> <li>Reformat code for kelp species segmentation by @tayden in <a href="https://github.com/HakaiInstitute/kelp-o-matic/pull/37">https://github.com/HakaiInstitute/kelp-o-matic/pull/37</a></li> <li>Change to Google-style code documentation by @tayden in <a href="https://github.com/HakaiInstitute/kelp-o-matic/pull/36">https://github.com/HakaiInstitute/kelp-o-matic/pull/36</a></li> <li>Update GHA step versions by @tayden in <a href="https://github.com/HakaiInstitute/kelp-o-matic/pull/42">https://github.com/HakaiInstitute/kelp-o-matic/pull/42</a></li> <li>Add macos-latest to test matrix by @tayden in <a href="https://github.com/HakaiInstitute/kelp-o-matic/pull/43">https://github.com/HakaiInstitute/kelp-o-matic/pull/43</a></li> <li>Add post-processing document by @tayden in <a href="https://github.com/HakaiInstitute/kelp-o-matic/pull/38">https://github.com/HakaiInstitute/kelp-o-matic/pull/38</a></li> <li>Add CITATION.cff</li> </ul> <p><strong>Full Changelog</strong>: <a href="https://github.com/HakaiInstitute/kelp-o-matic/compare/0.5.1...0.5.2rc1">https://github.com/HakaiInstitute/kelp-o-matic/compare/0.5.1...0.5.2rc1</a></p>If you use this software, please cite it as below

Satellite remote sensing of canopy-forming kelp on a complex coastline: A novel procedure using the Landsat image archive

Kelp forests are highly productive and diverse coastal marine ecosystems which have high variability in extent and biomass spatially and through time. Mapping and monitoring their distribution is integral to understanding the ecology of kelp forests and to inform marine protected area planning. Canada's Pacific coast presents specific challenges to mapping canopy forming kelp with thousands of kilometers of coastline, complex topography, and a large tidal range. While in situ methods and manual interpretation of aerial photography are commonly used to map canopy-forming kelp at local or regional scales, these methods are prohibitively expensive for continued large-area application. Historical and current available inventories of kelp extent are therefore incomplete for Canada's Pacific Coast. The advent of Google Earth Engine, a cloud-computing platform with a repository of Landsat imagery, provides an opportunity to apply Landsat image archive analyses and integrate temporal compositing and filtering to obtain unprecedented data on historical and current kelp extents. However, the effects of the spatial resolution and temporal coverage for mapping canopy-forming kelp in regions with complex coastlines and large tidal ranges are unknown. The objectives of this study were twofold: (1) develop a tool within Google Earth Engine to automate the detection of kelp using the Landsat satellite image archive, and (2) quantify the associated limitations for mapping the surface extent of canopy-forming kelp by comparing Landsat derived kelp extent with extents derived from WorldView-2 satellite imagery. The results indicate that the overall accuracy of the developed method is high at 80% and very close in accuracy to WorldView-2 data, but no detection is feasible within approximately one 30 m pixel from the shoreline. The interaction between the spatial resolution, kelp bed size, and bed configuration affected the detected kelp extent, as did the tide level during image acquisition. For both sensors, a 2 m increase in tide resulted in a 40% decrease in kelp extent detected. The Google Earth Engine kelp mapping tool presented provides an efficient and transferable method for mapping canopy kelp extent, and the only currently available method to reconstruct coast wide kelp development for the past three decades. The presented tool has applications in conservation and management planning, for example in creating a baseline of past kelp extent and examining trends in kelp forest variability

Satellite remote sensing of canopy-forming kelp on a complex coastline: A novel procedure using the Landsat image archive

Kelp forests are highly productive and diverse coastal marine ecosystems which have high variability in extent and biomass spatially and through time. Mapping and monitoring their distribution is integral to understanding the ecology of kelp forests and to inform marine protected area planning. Canada's Pacific coast presents specific challenges to mapping canopy forming kelp with thousands of kilometers of coastline, complex topography, and a large tidal range. While in situ methods and manual interpretation of aerial photography are commonly used to map canopy-forming kelp at local or regional scales, these methods are prohibitively expensive for continued large-area application. Historical and current available inventories of kelp extent are therefore incomplete for Canada's Pacific Coast. The advent of Google Earth Engine, a cloud-computing platform with a repository of Landsat imagery, provides an opportunity to apply Landsat image archive analyses and integrate temporal compositing and filtering to obtain unprecedented data on historical and current kelp extents. However, the effects of the spatial resolution and temporal coverage for mapping canopy-forming kelp in regions with complex coastlines and large tidal ranges are unknown. The objectives of this study were twofold: (1) develop a tool within Google Earth Engine to automate the detection of kelp using the Landsat satellite image archive, and (2) quantify the associated limitations for mapping the surface extent of canopy-forming kelp by comparing Landsat derived kelp extent with extents derived from WorldView-2 satellite imagery. The results indicate that the overall accuracy of the developed method is high at 80% and very close in accuracy to WorldView-2 data, but no detection is feasible within approximately one 30 m pixel from the shoreline. The interaction between the spatial resolution, kelp bed size, and bed configuration affected the detected kelp extent, as did the tide level during image acquisition. For both sensors, a 2 m increase in tide resulted in a 40% decrease in kelp extent detected. The Google Earth Engine kelp mapping tool presented provides an efficient and transferable method for mapping canopy kelp extent, and the only currently available method to reconstruct coast wide kelp development for the past three decades. The presented tool has applications in conservation and management planning, for example in creating a baseline of past kelp extent and examining trends in kelp forest variability