Autonomous Shipborne In Situ Reflectance Data in Optically Complex Coastal Waters: A Case Study of the Salish Sea, Canada

Present limitations on using satellite imagery to derive accurate chlorophyll concentrations and phytoplankton functional types arise from insufficient in situ measurements to validate the satellite reflectance, Rrs0+. We installed a set of hyperspectral radiometers with autonomous solar tracking capability, collectively named SAS Solar Tracker (Satlantic Inc./Sea-Bird), on top of a commercial ferry, to measure the in situ reflectance as the ferry crosses the Salish Sea, Canada. We describe the SAS Solar Tracker installation procedure, which enables a clear view of the sea surface and minimizes the interference caused by the ship superstructure. Corrections for residual ship superstructure perturbations and non-nadir-viewing geometry are applied during data processing to ensure optimal data quality. It is found that the ship superstructure perturbation correction decreased the overall Rrs0+ by 0.00055 sr−1, based on a black-pixel assumption for the infrared band of the lowest acquired turbid water. The BRDF correction using the inherent optical properties approach lowered the spectral signal by ∼5–10%, depending on the wavelength. Data quality was evaluated according to a quality assurance method considering spectral shape similarity, and ∼92% of the acquired reflectance data matched well against the global database, indicating high quality

Long-term spatial-temporal eelgrass (Zostera marina) habitat change in the Salish Sea (1932-2016)

Eelgrass (Zostera marina) is a critical nearshore marine habitat for juvenile Pacific salmon (Oncorhynchus spp.) as they depart from their natal streams. Given the poor marine survival of Coho (O. kisutch) and Chinook (O. tshawytscha) salmon juveniles in recent decades, it is hypothesized that deteriorating eelgrass habitats could contribute to their low survival. For three small estuaries in the Southern Gulf Islands of British Columbia, changes in eelgrass area coverage and shape index over the period of 1932-2016 were assessed using historic aerial photographs and Unmanned Aerial Vehicle (UAV) imagery. In addition, changes in eelgrass area and shape index were evaluated in relation to landscape level coastal environmental indicators, namely shoreline activities and alterations and residential housing density. All three eelgrass meadows showed a deteriorating trend in eelgrass condition; on average, eelgrass area coverage decreases by 41% while meadow complexity as indicated by the shape index increases by 76%. Shoreline activities (number of boats, docks, log booms, bulkhead) and residential housing density increase dramatically at all sites over the study period, which are moderately to very strongly correlated to eelgrass area coverage and shape index. Changes in these landscape level indicators over this time period corroborate the observed decline in eelgrass habitat condition as they suggest an overall deterioration of coastal environmental health in the Salish Sea due to increased use of the coastal zone as well as declines in water quality due to urbanization

Seasonal dynamics of oceanographic conditions, phytoplankton, and zooplankton in the Malaspina Strait, Strait of Georgia

Plankton dynamics in the Salish Sea may directly impact resident and migratory fish populations that are of major economic importance in the region. The Malaspina Strait in the northern Salish Sea is of particular interest as it is an important migration route for juvenile salmon. Here, we present data collected at three stations in the Malaspina Strait as part of the Citizen Science initiative of the Salish Sea Marine Survival Project. Sampling was conducted at bi-monthly (or higher) frequency from February to October, 2015 to 2017. Relationships between the regional hydrography, environmental parameters (temperature, salinity, dissolved oxygen, etc.), nutrient concentrations, and phytoplankton and zooplankton community composition are considered. Preliminary results indicate that 2015 was an anomalous year with an earlier-than-average (mid-February) spring phytoplankton bloom. Phytoplankton community composition was dominated by centric, chain-forming diatoms in spring of all years, cell densities were higher in spring 2015 compared to 2016 and 2017. In both 2015 and 2016, copepods dominated the abundances of zooplankton at the deep locations in Malaspina Strait. However, the biomass was dominated by taxa known to be the preferred prey of juvenile salmonids (euphausiids, amphipods, crab larvae). At the nearshore station in both years, zooplankton biomass was dominated by “other” taxa, in particular gelatinous plankton. Biomass of large calanoid copepods and euphausiids was significantly positively correlated to the relative abundance of diatoms. Biomass of small calanoid copepods and non-calanoid copepods, on the other hand, was positively correlated with the relative abundance of dinoflagellates. Further analyses will relate environmental variables to the observed seasonal variations in phytoplankton and zooplankton. Results from this study will ultimately be extended to include other Citizen Science stations in order to gain a better understanding of how bottom-up processes vary in different regions of the Salish Sea, and the potential implications for higher trophic levels

A SAR FINE AND MEDIUM SPATIAL RESOLUTION APPROACH FOR MAPPING THE BRAZILIAN PANTANAL

The objective of this research was to utilize a dual season set of L-band (ALOS/PALSAR) and C-band (RADARSAT-2 and ENVISAT/ASAR) imagery, a comprehensive set of ground reference data, and a hierarchical object-oriented approach to 1) define the diverse habitats of the Lower Nhecolândia subregion of the Pantanal at both a fine spatial resolution (12.5 m), and a relatively medium spatial resolution (50 m), thus evaluating the accuracy of the differing spatial resolutions for land cover classification of the highly spatially heterogeneous subregion, and, 2) to define on a regional scale, using the 50 m spatial resolution imagery, the wetland habitats of each of the hydrological subregions of the Pantanal, thereby producing a final product covering the entire Pantanal ecosystem. The final classification maps of the Lower Nhecolândia subregion were achieved at overall accuracies of 83% and 72% for the 12.5 m and 50 m spatial resolutions, respectively, defining seven land cover classes. In general, the highest degree of confusion for both fine and medium resolution Nhecolândia classifications were related to the following issues: 1) scale of habitats, for instance, capões, cordilheiras, and lakes, in relation to spatial resolution of the imagery, and 2) variable flooding patterns in the subregion. Similar reasons were attributed to the classification errors for the whole Pantanal. A 50 m spatial resolution classification of the entire Pantanal wetland was achieved with an overall accuracy of 80%, defining ten land cover classes. Given the analysis of the comparison of fine and relatively medium spatial resolution classifications of the Lower Nhecolândia subregion, the authors concluded that significant improvements in accuracy can be achieved with the finer spatial resolution dataset, particularly in subregions with high spatial heterogeneity in land cove

Feasibility Study for an Aquatic Ecosystem Earth Observing System Version 1.2.

International audienceMany Earth observing sensors have been designed, built and launched with primary objectives of either terrestrial or ocean remote sensing applications. Often the data from these sensors are also used for freshwater, estuarine and coastal water quality observations, bathymetry and benthic mapping. However, such land and ocean specific sensors are not designed for these complex aquatic environments and consequently are not likely to perform as well as a dedicated sensor would. As a CEOS action, CSIRO and DLR have taken the lead on a feasibility assessment to determine the benefits and technological difficulties of designing an Earth observing satellite mission focused on the biogeochemistry of inland, estuarine, deltaic and near coastal waters as well as mapping macrophytes, macro-algae, sea grasses and coral reefs. These environments need higher spatial resolution than current and planned ocean colour sensors offer and need higher spectral resolution than current and planned land Earth observing sensors offer (with the exception of several R&D type imaging spectrometry satellite missions). The results indicate that a dedicated sensor of (non-oceanic) aquatic ecosystems could be a multispectral sensor with ~26 bands in the 380-780 nm wavelength range for retrieving the aquatic ecosystem variables as well as another 15 spectral bands between 360-380 nm and 780-1400 nm for removing atmospheric and air-water interface effects. These requirements are very close to defining an imaging spectrometer with spectral bands between 360 and 1000 nm (suitable for Si based detectors), possibly augmented by a SWIR imaging spectrometer. In that case the spectral bands would ideally have 5 nm spacing and Full Width Half Maximum (FWHM), although it may be necessary to go to 8 nm wide spectral bands (between 380 to 780nm where the fine spectral features occur -mainly due to photosynthetic or accessory pigments) to obtain enough signal to noise. The spatial resolution of such a global mapping mission would be between ~17 and ~33 m enabling imaging of the vast majority of water bodies (lakes, reservoirs, lagoons, estuaries etc.) larger than 0.2 ha and ~25% of river reaches globally (at ~17 m resolution) whilst maintaining sufficient radiometric resolution

GALENE - Understanding coastal and inland ecosystem properties, processes and dynamics

Coastal and inland aquatic ecosystems are of fundamental interest for societal and economical purposes due to a significant part of the population living there. They both highly contribute to carbon cycling and biodiversity. Those ecosystems are continuously impacted by natural processes and human activities. Many of these impacts become more frequent and severe, particularly with increasing population and climate change. Hence, there is a need (i) to generate reliable, robust and timely evidence of how these environments are changing, (ii) to understand processes causing these changes and their societal, health, and economic consequences, and (iii) to identify steps towards conservation, restoration and sustainable use of water and dependent ecosystems, and resources. Systematic, high-quality and global observations, such as those provided by satellite remote sensing techniques, are key to understand complex aquatic systems. While multitudes of remote sensing missions have been specifically designed for studying ocean biology and biogeochemistry as well as for evaluating terrestrial environments, remote sensing missions dedicated to studying critical coastal and inland aquatic ecosystems at global scale are non-existent. Thus, these ecosystems remain among the most understudied habitats on the Earth’s surface. Specific reasons for such an observational gap lie in the dynamic and optical complexity of water ecosystems, in combination with technological challenges to optimize the relevant spatial, spectral, radiometric, and temporal characteristics. Current and forthcoming missions are either not suited to provide a global coverage (e.g., PRISMA, EnMAP) or to obtain reliable data over dark waters (e.g., carbon-rich lakes) due to inadequate radiometric sensitivity (e.g., Sentinel-2/MSI). They are also not adapted for characterizing the biodiversity patchiness of submerged habitats and water column compositions such as phytoplankton assemblages due to their inadequate spectral resolution (e.g., Sentinel-2/MSI, Sentinel-3/OLCI). Wetland ecosystems are insufficiently described as current sensors do not adequately capture their diversity, which compromises their management and protection. A future satellite mission, so-called Global Assessment of Limnological, Estuarine and Neritic Ecosystems (GALENE), has been proposed to the Earth Explorer 11 call (ESA) to respond to the future challenges linked to coastal and inland ecosystems. GALENE will provide optimized measurements of these aquatic ecosystems, and enable an adaptive sampling of dynamic properties and processes in water columns, benthic habitats and associated wetlands. GALENE will thus fill a major gap by comprehensively quantifying the state of Earth’s water bodies and aquatic ecosystems. It will substantially contribute addressing global water challenges, including water pollution and ensuring clean drinking water supply for all and protecting coastal environments and populations. GALENE mission concept consists of a synergy of three innovative instruments, namely a hyperspectral sensor, a panchromatic camera and a polarimeter. The GALENE science objectives and main technological features will be presented

The CEOS Feasibility Study for an aquatic ecosystem imaging spectrometer

The Committee on Earth Observation Satellites (CEOS) response to the Group on Earth Observations System of Systems (GEOSS) Water Strategy developed under the auspices of the Water Strategy Implementation Study Team was endorsed by CEOS at the 2015 Plenary. As one of the actions, CSIRO has taken the lead on recommendation C.10: A feasibility assessment to determine the benefits and technological difficulties of designing a hyperspectral satellite mission focused on water quality measurements. More specifically this report is a highlevel feasibility assessment of the benefits and technological difficulties of designing a hyperspectral satellite mission focused on biogeochemistry of inland, estuarine, deltaic and near coastal waters as well as mapping macrophytes, macroalgae , seagrasses and coral reefs at significantly higher spatial resolution than 250 m, which is the maximum spatial resolution of dedicated current aquatic sensors such as Sentinel3 and future planned aquatic sensors such as the Coastal Ocean Color Imager (COCI – 100 m res). Further, the GEO Community of Practice Aquawatch suggested that alternative approaches, involving augmenting designs of spaceborne sensors for terrestrial and ocean colour applications to allow improved inland, near coastal waters and benthic applications, could offer an alternative pathway to addressing the same underlying science questions. Accordingly, this study also analizes the benefits and technological difficulties of this option as part of the highlevel feasibility study

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)