bioRxiv (Cold Spring Harbor Laboratory), May 16, 2024
Kelp forests are one of the earth's most productive ecosystems and are at the greatest risk from ... more Kelp forests are one of the earth's most productive ecosystems and are at the greatest risk from climate change, yet little is known regarding their future threats and current conservation status. By combining a global remote sensing dataset of floating kelp forests with climate data and projections, we find that exposure to projected marine heatwaves will increase ~8 times compared to contemporary (2001-2020) exposure for intermediate climate scenarios. While exposure will intensify for all forests, climate refugia emerge for some southern hemisphere kelp forests, which have lower exposure to contemporary and projected marine heatwaves. Under these escalating threats, less than 3% of global kelp forests are currently within highly restrictive marine protected areas, the most effective conservation measure for providing climate resilience. Our findings emphasize the urgent need to increase the global protection of kelp forests and set bolder climate adaptation goals. Marine protected areas (MPAs) are a cornerstone of marine conservation 1 . Promoted by international agreements, such as the Convention on Biological Diversity (CBD) Aichi Target 11 2 , the area of marine ecosystems under some form of protection has increased since the turn of the century 3 . Because climate change is the main long-term threat to biodiversity 4-6 , the newly agreed Global Biodiversity Framework at COP15 7 calls for effectively protecting 30% of the oceans by 2030. A central component of the post-2020 targets is increasing the representation of different habitats under effective protection while adapting to climate change. Although many studies report the protection of critical habitat-forming species, such as corals, seagrass, and mangroves 3 , other essential marine habitats, such as kelp forests, remain largely neglected 8 (but see ). Information on kelp forest distribution, threats associated with climate change, and protection status is urgently needed to guide ongoing local and global protection efforts. Kelp forests dominate >30% of the world's rocky reefs and are among the most productive ecosystems on earth -comparable to terrestrial rainforests and coral reefs . However, marine heatwaves (MHWs) and anthropogenic activities threaten kelp forests and their capacity to provide ecosystem services worth billions of dollars . Kelp forests are among the marine ecosystems at greatest risk from MHWs 6 , which is concerning given that MHWs are projected to become more frequent and severe in the next decades . For example, Tasmania and northern California have lost >90% of their kelp forests following MHWs and other impacts of climate change . Climate adaptation strategies -including MPAs-are urgently needed to halt and reverse this loss . Well-managed and highly restrictive MPAs -no-take marine reserves where all fishing activities are prohibited-are the most effective type of MPA for supporting the stability of kelp forests 25 and their resilience to MHW impacts 26,27 by facilitating the recovery of highertrophic-level, which helps control kelp grazer populations and prevent overgrazing of kelp .
For 2 years, a baseline investigation was carried out to collect reference information of the pre... more For 2 years, a baseline investigation was carried out to collect reference information of the present environmental status in the Fehmarn Belt and adjacent area. The temporal and spatial variability of phytoplankton was monitored by a combination of monitoring buoys, pigment analysis and fast screening microscopy. The overall phytoplankton succession in the Fehmarn Belt area was found to be influenced primarily by the seasonal changes, where various diatoms dominated the spring and autumn blooms and flagellates like Chrysochromulina sp., Dictyocha speculum and various dinoflagellates were occasionally abundant in late spring and summer. The phytoplankton groups were remarkably uniform horizontally in the investigation area while large differences in both biomasses and composition of individual phytoplankton groups were seen vertically in the water column, especially in the summer periods, in which the two-layer exchange flow between the North Sea and the Baltic Sea is showing a particularly strong stratification in the Fehmarn Belt. The chlorophyll a concentrations ranged continuously from 1 to 3 μg/L at the three permanent buoy stations during the 2 years of monitoring, except for the spring and autumn blooms where chlorophyll a increased up to 18 μg/L in the spring of 2010 and up to 8 μg/L in the autumn of 2009. Recurrent blooms of filamentous cyanobacteria are common during the summer period in the Baltic Sea and adjacent areas, but excessive blooms of cyanobacteria did not occur in 2009 and 2010 in the Fehmarn Belt area. The combination of the HPLC pigment analysis method and monitoring buoys continuously measuring fluorescence at selected stations with fast screening of samples in the microscope proved advantageous for obtaining information on both the phytoplankton succession and dynamic and, at the same time, getting information on duration and intensity of the blooms as well as specific information on the dominant species present both temporally and spatially in the large Fehmarn Belt area.
Kelp forests provide key habitat on the Pacific Coast of Canada; however, the long-term changes i... more Kelp forests provide key habitat on the Pacific Coast of Canada; however, the long-term changes in their distribution and abundance remain poorly understood. With advances in satellite technology, floating kelp forests can now be monitored across large-scale areas. We present a methodological framework using an object-based image analysis approach that enables the combination of imagery from multiple satellites at different spatial resolutions and temporal coverage, to map kelp forests with floating canopy through time. The framework comprises four steps: (1) compilation and quality assessment; (2) preprocessing; (3) an object-oriented classification; and (4) an accuracy assessment. Additionally, the impact of spatial resolution on the detectability of floating kelp forests is described. Overall, this workflow was successful in producing accurate maps of floating kelp forests, with global accuracy scores of between 88% and 94%. When comparing the impact of resolution on detectabilit...
Classifying the ocean into regions with distinct biogeochemical or physical properties may enhanc... more Classifying the ocean into regions with distinct biogeochemical or physical properties may enhance our interpretation of ocean processes. Highresolution satellite-derived products provide valuable data to address this task. Notwithstanding, no regionalization at a regional scale has been attempted for the coastal and open oceans of British Columbia (BC) and Southeast Alaska (SEA), which host essential habitats for several ecologically, culturally, and commercially important species. Across this heterogeneous marine domain, phytoplankton are subject to dynamic ocean circulation patterns and atmosphere-ocean-land interactions, and their variability, in turn, influences marine food web structure and function. Regionalization based on phytoplankton biomass patterns along BC and SEA's coastal and open oceans can be valuable in identifying pelagic habitats and representing a baseline for assessing future changes. We developed a two-step classification procedure, i.e., a Self-Organizing Maps (SOM) analysis followed by the affinity propagation clustering method, to define ten bioregions based on the seasonal climatology of high-resolution (300 m) Sentinel-3 surface chlorophyll-a data (a proxy for phytoplankton biomass), for the period 2016-2020. The classification procedure allowed high precision delineation of the ten bioregions, revealing separation between off-shelf bioregions and those in neritic waters. Consistent with the high-nutrient, low-chlorophyll regime, relatively low values of phytoplankton biomass (< 1 mg/m 3) distinguished off-shelf bioregions, which also displayed, on average, more prominent autumn biomass peaks. In sharp contrast, neritic bioregions were highly productive (>> 1 mg/m 3) and characterized by different phytoplankton dynamics. The spring phytoplankton bloom onset varied spatially and inter-annually, with substantial differences among bioregions. The proposed high-spatial-resolution regionalization constitutes a reference point for practical Frontiers in Marine Science frontiersin.org 01
In the Salish Sea, eelgrass meadows provide structurally complex habitat for a myriad of fish and... more In the Salish Sea, eelgrass meadows provide structurally complex habitat for a myriad of fish and invertebrate species, supporting marine ecosystems and stabilizing coastal sediments. Seagrasses of all species however, are in worldwide decline as increasing coastal development threatens the function and diversity of nearshore marine ecosystems. Long-term studies of the spatio-temporal dynamics of eelgrass in the Salish Sea are an important step in identifying contributing factors to eelgrass decline, and developing effective conservation and restoration strategies. One such dynamic to quantify are the impacts of coastal development on the distribution and trends of eelgrass ecosystems. Utilizing a historic aerial photography dataset covering the Southern Gulf Islands, BC over the years of 1932 to 2014, eelgrass beds were mapped using digital image classification methods for selected sites within the region. Through the application of a GIS change analysis, trends in eelgrass distribution were characterized and compared to changes in shoreline development and land use change in adjacent catchment areas. The results of this analysis can be applied to education, conservation, and restoration practices to prevent further eelgrass decline in the Salish Sea and beyond
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
International Journal of Remote Sensing, Oct 20, 2005
Synthetic aperture radar images, combined with field measurements, were used to estimate net prim... more Synthetic aperture radar images, combined with field measurements, were used to estimate net primary productivity (NPP) of aquatic vegetation in the lower Amazon. Input data for a NPP model are (i) the total biomass of aquatic vegetation, determined by radar imagery and field measurements and (ii) the area occupied by aquatic vegetation, determined from radar imagery. After correction for monthly biomass losses, the NPP of one growth cycle of aquatic vegetation was calculated in the image domain. The total net primary productivity of Hymenachne amplexicaules, the dominant aquatic vegetation in the area, was on average 19×10 g C yr for the entire area. Spatially, lower values of produced organic carbon (<900 g C m yr) are confined to regions where the plants developed only in the beginning of the rising phase of the hydrological cycle. In general, values are higher (>5000 g C m yr) in areas closer to the Amazon River where the availability and influence of nutrient‐rich water is greater.
Japanese Earth Resources Satellite 1 (JERS-1) imagery acquired over the Amazon basin during low- ... more Japanese Earth Resources Satellite 1 (JERS-1) imagery acquired over the Amazon basin during low- and high-water periods makes it possible to map seasonal inundation and vegetation of wetlands for most of the basin. Dual-season mapping has now been completed for a central Amazon quadrat extending from 72\deg W,0\deg S to 54\deg W,8\deg S. Imagery was acquired by the JERS-1 L-band, HH-polarized SAR during Sept.-Oct. 1995 and May-June 1996, and mosaicked at the Jet Propulsion Laboratory into low- and high-water mosaics with pixel dimensions of approx. 100 m. Image segmentation software developed at INPE was used to carry out a polygon-based classification of the co-registered mosaics into wetland and non-wetland classes. Wetland areas were classified by inundation state (flooded vs. non-flooded) and vegetation type (non-vegetated, woody, or herbaceous), and classification accuracy was assessed using geo-coded digital videography acquired during aerial surveys of the Brazilian Amazon. Seventeen percent of the study quadrat is occupied by wetlands, which are 96% inundated at high water and 26% inundated at low water (including river and stream channels). Flooded forest constitutes nearly 70% of the wetland area at high water. This mapping methodology is being applied to the entire lowland portion of the basin. In order to map inundation extent at intermediate water stages, and to increase classification accuracy in savanna regions, we are using time series of high-resolution JERS-1 and Radarsat data, and will make extensive use of planned acquisitions from the ENVISAT ASAR and ALOS PALSAR sensors.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Field measurements were combined with Synthetic Aperture Radar (SAR) images to evaluate the use o... more Field measurements were combined with Synthetic Aperture Radar (SAR) images to evaluate the use of radar for estimating biomass changes and mapping of aquatic vegetation in the lower Amazon. Field campaigns were conducted concomitant to the acquisition of Radarsat and JERS-1 images at five different stages of the hydrological cycle. The temporal variability of the SAR data for aquatic vegetation shows a dynamic range of 5 dB, however this is due dominantly to the significant differences ( p <0.05) between the low water season when vegetation is small and just emerging and other seasons when vegetation is fully developed. The spatial variability of the above-water biomass is detectable with radar data. Significant correlation ( p <0.05) exist between backscattering coefficients and both above-water dry biomass and height of the plants. The logarithmic relationship between backscattering coefficients and biomass suggests that (1) at low biomass, high transmissivity of the microwave radiation through the vegetation canopy occurs and the backscattering is a result of quasi-specular reflection of both C and L bands and a minor contribution of canopy volume scattering from C band; (2) at intermediate levels of biomass, moderate changes in backscattering values occur and the saturation point of backscattering is reached; and (3) at high biomass, the transmissivity of C and L band radiation is equally attenuated and backscattering approaches similar values for both. A combination of Radarsat and JERS-1 images from high and low water periods were classified using a segmentation algorithm and had an accuracy higher than 97% for vegetated areas of the floodplain. Although further research is needed to better understand the saturation points for Radarsat and JERS-1 data, these findings clearly show that C and L bands can accurately map aquatic vegetation of the Amazon floodplain.
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Dec 1, 2010
Page 1. 560 IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING, VOL... more Page 1. 560 IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING, VOL. 3, NO. 4, DECEMBER 2010 Using ALOS/PALSAR and RADARSAT-2 to Map Land Cover and Seasonal Inundation in the Brazilian Pantanal ...
The original version of this Article contained an error in the order of the Figures. Figures 1 an... more The original version of this Article contained an error in the order of the Figures. Figures 1 and 2 were published as Figure 4 and 1. As a result, Figures 2 and 3 were renumbered to Figures 3 and 4.
Herbaceous aquatic macrophytes cover extensive areas on the floodplains of the Amazon basin and a... more Herbaceous aquatic macrophytes cover extensive areas on the floodplains of the Amazon basin and are an important habitat and input of organic carbon. These communities have large intra- and inter-annual variability, and characterization of this variability is necessary to quantify the role of macrophytes in the ecology and biogeochemistry of the floodplain. A novel approach for mapping the temporal evolution
ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Jun 17, 2021
The eastern coastline of James Bay (Eeyou Istchee) is known to be home to beds of subarctic eelgr... more The eastern coastline of James Bay (Eeyou Istchee) is known to be home to beds of subarctic eelgrass (Zostera marina L.). These eelgrass beds provide valuable habitat and food source for coastal and marine animals and contribute valuable ecosystem services such as stabilization of the shoreline all along the coast. Despite reports from Cree communities that eelgrass bed health has declined, limited research has been performed to assess and map the spatial distribution of eelgrass within the bay. This study aims to address that issue by evaluating the capability of Landsat-8 Operational Land Imager (OLI) imagery to establish a baseline map of eelgrass distribution in 2019 in the relatively turbid waters of Eeyou Istchee. Three images acquired in September 2019 were merged and classified using Random Forests into the following classes: Eelgrass, Turbid Water, Highly Turbid Water, and Optically Deep Water. The resulting classified image was validated against 108 ground truth data that were obtained from both the eelgrass health and Hydro-Quebec research team. The resulting overall accuracy was 78.7%, indicating the potential of the Random Forests classifier to estimate baseline eelgrass coverage in James Bay using Landsat-8 imagery. This project is part of a Cree driven project, the Coastal Habitat Comprehensive Research Program (CHCRP). The CHCRP aims to combine Cree's traditional knowledge with Western science to better understand environmental changes in the coastal ecosystems and ecosystem services of eastern James Bay. The study is funded by a MITACS grant sponsored by Niskamoon Corporation, an indigenous non-profit organization.
Aquatic herbaceous macrophytes contribute significantly to the input carbon for the Amazon floodp... more Aquatic herbaceous macrophytes contribute significantly to the input carbon for the Amazon floodplain. These plants have large seasonal variations in areal coverage and high productivity. The present study estimates annual net primary production (NPP) of aquatic herbaceous macrophytes in a large lake on the eastern Amazon floodplain, assesses the sources and amount of uncertainty associated with these measures, and offers a comparison among the estimates of herbaceous macrophyte productivity in the Amazon region. Plant biomass accumulated during the rising water stage of the annual flood cycle, peaking at 2300 to 6100 g m 22 and decreasing later in the year. Annual net primary production was estimated to range from 2400 to 3500 g m 22 yr 21 , with above water production between 650 and 1100 g m 22 yr 21 , and below water production between 1700 and 2600 g m 22 yr 21. Echinochloa polystachya and Paspalum fasciculatum were the most productive species, followed by Paspalum repens, Hymenachne amplexicaulis, and Oryza perennis. The four main sources of uncertainty in the estimates were macrophyte taxa, location, sampling design, and lack of measurements of dead material loss.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
RADARSAT S1 and S7, and JERS imagery are integrated with field measurements of geochemistry and c... more RADARSAT S1 and S7, and JERS imagery are integrated with field measurements of geochemistry and characteristics of emergent aquatic vegetation to investigate the potential of SAR data to map fresh and brackish lakes of the Brazilian Pantanal. SAR images can determine emergent aquatic plant assemblages which are controlled by the total dissolved solids and pH of lakes. SAR images can therefore potentially be used to indirectly map the geochemistry of the hundreds of thousands of lakes in the Pantanal. This may be the most feasible way to map lake type in the Pantanal because the area is remote and the lakes are so numerous. The quantities and types of lakes and their spatial distribution is important information for understanding how the Pantanal ecosystem formed, how it works, and what is required to preserve it.
ABSTRACT Nahirnick, N.K.; Costa, M.; Schroeder, S., and Sharma, T., 2020. Long-term eelgrass habi... more ABSTRACT Nahirnick, N.K.; Costa, M.; Schroeder, S., and Sharma, T., 2020. Long-term eelgrass habitat change and associated human impacts on the west coast of Canada. Journal of Coastal Research, 36(1), 30–40. Coconut Creek (Florida), ISSN 0749-0208. Eelgrass (Zostera marina) forms a critical nearshore marine habitat in temperate coastal ecosystems. 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 historical aerial photographs and unoccupied aerial system (UAS) 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 decreased by 45.1%, while meadow complexity as indicated by the shape index increased by 66.3%. Shoreline activities (boats, docks, log booms, and armoring) and residential housing density increased markedly at all sites over the study period and were strongly correlated to eelgrass area coverage and shape index. Changes in these landscape-level indicators over this period corroborate the observed decline in eelgrass habitat condition, because 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.
bioRxiv (Cold Spring Harbor Laboratory), May 16, 2024
Kelp forests are one of the earth's most productive ecosystems and are at the greatest risk from ... more Kelp forests are one of the earth's most productive ecosystems and are at the greatest risk from climate change, yet little is known regarding their future threats and current conservation status. By combining a global remote sensing dataset of floating kelp forests with climate data and projections, we find that exposure to projected marine heatwaves will increase ~8 times compared to contemporary (2001-2020) exposure for intermediate climate scenarios. While exposure will intensify for all forests, climate refugia emerge for some southern hemisphere kelp forests, which have lower exposure to contemporary and projected marine heatwaves. Under these escalating threats, less than 3% of global kelp forests are currently within highly restrictive marine protected areas, the most effective conservation measure for providing climate resilience. Our findings emphasize the urgent need to increase the global protection of kelp forests and set bolder climate adaptation goals. Marine protected areas (MPAs) are a cornerstone of marine conservation 1 . Promoted by international agreements, such as the Convention on Biological Diversity (CBD) Aichi Target 11 2 , the area of marine ecosystems under some form of protection has increased since the turn of the century 3 . Because climate change is the main long-term threat to biodiversity 4-6 , the newly agreed Global Biodiversity Framework at COP15 7 calls for effectively protecting 30% of the oceans by 2030. A central component of the post-2020 targets is increasing the representation of different habitats under effective protection while adapting to climate change. Although many studies report the protection of critical habitat-forming species, such as corals, seagrass, and mangroves 3 , other essential marine habitats, such as kelp forests, remain largely neglected 8 (but see ). Information on kelp forest distribution, threats associated with climate change, and protection status is urgently needed to guide ongoing local and global protection efforts. Kelp forests dominate >30% of the world's rocky reefs and are among the most productive ecosystems on earth -comparable to terrestrial rainforests and coral reefs . However, marine heatwaves (MHWs) and anthropogenic activities threaten kelp forests and their capacity to provide ecosystem services worth billions of dollars . Kelp forests are among the marine ecosystems at greatest risk from MHWs 6 , which is concerning given that MHWs are projected to become more frequent and severe in the next decades . For example, Tasmania and northern California have lost >90% of their kelp forests following MHWs and other impacts of climate change . Climate adaptation strategies -including MPAs-are urgently needed to halt and reverse this loss . Well-managed and highly restrictive MPAs -no-take marine reserves where all fishing activities are prohibited-are the most effective type of MPA for supporting the stability of kelp forests 25 and their resilience to MHW impacts 26,27 by facilitating the recovery of highertrophic-level, which helps control kelp grazer populations and prevent overgrazing of kelp .
For 2 years, a baseline investigation was carried out to collect reference information of the pre... more For 2 years, a baseline investigation was carried out to collect reference information of the present environmental status in the Fehmarn Belt and adjacent area. The temporal and spatial variability of phytoplankton was monitored by a combination of monitoring buoys, pigment analysis and fast screening microscopy. The overall phytoplankton succession in the Fehmarn Belt area was found to be influenced primarily by the seasonal changes, where various diatoms dominated the spring and autumn blooms and flagellates like Chrysochromulina sp., Dictyocha speculum and various dinoflagellates were occasionally abundant in late spring and summer. The phytoplankton groups were remarkably uniform horizontally in the investigation area while large differences in both biomasses and composition of individual phytoplankton groups were seen vertically in the water column, especially in the summer periods, in which the two-layer exchange flow between the North Sea and the Baltic Sea is showing a particularly strong stratification in the Fehmarn Belt. The chlorophyll a concentrations ranged continuously from 1 to 3 μg/L at the three permanent buoy stations during the 2 years of monitoring, except for the spring and autumn blooms where chlorophyll a increased up to 18 μg/L in the spring of 2010 and up to 8 μg/L in the autumn of 2009. Recurrent blooms of filamentous cyanobacteria are common during the summer period in the Baltic Sea and adjacent areas, but excessive blooms of cyanobacteria did not occur in 2009 and 2010 in the Fehmarn Belt area. The combination of the HPLC pigment analysis method and monitoring buoys continuously measuring fluorescence at selected stations with fast screening of samples in the microscope proved advantageous for obtaining information on both the phytoplankton succession and dynamic and, at the same time, getting information on duration and intensity of the blooms as well as specific information on the dominant species present both temporally and spatially in the large Fehmarn Belt area.
Kelp forests provide key habitat on the Pacific Coast of Canada; however, the long-term changes i... more Kelp forests provide key habitat on the Pacific Coast of Canada; however, the long-term changes in their distribution and abundance remain poorly understood. With advances in satellite technology, floating kelp forests can now be monitored across large-scale areas. We present a methodological framework using an object-based image analysis approach that enables the combination of imagery from multiple satellites at different spatial resolutions and temporal coverage, to map kelp forests with floating canopy through time. The framework comprises four steps: (1) compilation and quality assessment; (2) preprocessing; (3) an object-oriented classification; and (4) an accuracy assessment. Additionally, the impact of spatial resolution on the detectability of floating kelp forests is described. Overall, this workflow was successful in producing accurate maps of floating kelp forests, with global accuracy scores of between 88% and 94%. When comparing the impact of resolution on detectabilit...
Classifying the ocean into regions with distinct biogeochemical or physical properties may enhanc... more Classifying the ocean into regions with distinct biogeochemical or physical properties may enhance our interpretation of ocean processes. Highresolution satellite-derived products provide valuable data to address this task. Notwithstanding, no regionalization at a regional scale has been attempted for the coastal and open oceans of British Columbia (BC) and Southeast Alaska (SEA), which host essential habitats for several ecologically, culturally, and commercially important species. Across this heterogeneous marine domain, phytoplankton are subject to dynamic ocean circulation patterns and atmosphere-ocean-land interactions, and their variability, in turn, influences marine food web structure and function. Regionalization based on phytoplankton biomass patterns along BC and SEA's coastal and open oceans can be valuable in identifying pelagic habitats and representing a baseline for assessing future changes. We developed a two-step classification procedure, i.e., a Self-Organizing Maps (SOM) analysis followed by the affinity propagation clustering method, to define ten bioregions based on the seasonal climatology of high-resolution (300 m) Sentinel-3 surface chlorophyll-a data (a proxy for phytoplankton biomass), for the period 2016-2020. The classification procedure allowed high precision delineation of the ten bioregions, revealing separation between off-shelf bioregions and those in neritic waters. Consistent with the high-nutrient, low-chlorophyll regime, relatively low values of phytoplankton biomass (< 1 mg/m 3) distinguished off-shelf bioregions, which also displayed, on average, more prominent autumn biomass peaks. In sharp contrast, neritic bioregions were highly productive (>> 1 mg/m 3) and characterized by different phytoplankton dynamics. The spring phytoplankton bloom onset varied spatially and inter-annually, with substantial differences among bioregions. The proposed high-spatial-resolution regionalization constitutes a reference point for practical Frontiers in Marine Science frontiersin.org 01
In the Salish Sea, eelgrass meadows provide structurally complex habitat for a myriad of fish and... more In the Salish Sea, eelgrass meadows provide structurally complex habitat for a myriad of fish and invertebrate species, supporting marine ecosystems and stabilizing coastal sediments. Seagrasses of all species however, are in worldwide decline as increasing coastal development threatens the function and diversity of nearshore marine ecosystems. Long-term studies of the spatio-temporal dynamics of eelgrass in the Salish Sea are an important step in identifying contributing factors to eelgrass decline, and developing effective conservation and restoration strategies. One such dynamic to quantify are the impacts of coastal development on the distribution and trends of eelgrass ecosystems. Utilizing a historic aerial photography dataset covering the Southern Gulf Islands, BC over the years of 1932 to 2014, eelgrass beds were mapped using digital image classification methods for selected sites within the region. Through the application of a GIS change analysis, trends in eelgrass distribution were characterized and compared to changes in shoreline development and land use change in adjacent catchment areas. The results of this analysis can be applied to education, conservation, and restoration practices to prevent further eelgrass decline in the Salish Sea and beyond
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
International Journal of Remote Sensing, Oct 20, 2005
Synthetic aperture radar images, combined with field measurements, were used to estimate net prim... more Synthetic aperture radar images, combined with field measurements, were used to estimate net primary productivity (NPP) of aquatic vegetation in the lower Amazon. Input data for a NPP model are (i) the total biomass of aquatic vegetation, determined by radar imagery and field measurements and (ii) the area occupied by aquatic vegetation, determined from radar imagery. After correction for monthly biomass losses, the NPP of one growth cycle of aquatic vegetation was calculated in the image domain. The total net primary productivity of Hymenachne amplexicaules, the dominant aquatic vegetation in the area, was on average 19×10 g C yr for the entire area. Spatially, lower values of produced organic carbon (<900 g C m yr) are confined to regions where the plants developed only in the beginning of the rising phase of the hydrological cycle. In general, values are higher (>5000 g C m yr) in areas closer to the Amazon River where the availability and influence of nutrient‐rich water is greater.
Japanese Earth Resources Satellite 1 (JERS-1) imagery acquired over the Amazon basin during low- ... more Japanese Earth Resources Satellite 1 (JERS-1) imagery acquired over the Amazon basin during low- and high-water periods makes it possible to map seasonal inundation and vegetation of wetlands for most of the basin. Dual-season mapping has now been completed for a central Amazon quadrat extending from 72\deg W,0\deg S to 54\deg W,8\deg S. Imagery was acquired by the JERS-1 L-band, HH-polarized SAR during Sept.-Oct. 1995 and May-June 1996, and mosaicked at the Jet Propulsion Laboratory into low- and high-water mosaics with pixel dimensions of approx. 100 m. Image segmentation software developed at INPE was used to carry out a polygon-based classification of the co-registered mosaics into wetland and non-wetland classes. Wetland areas were classified by inundation state (flooded vs. non-flooded) and vegetation type (non-vegetated, woody, or herbaceous), and classification accuracy was assessed using geo-coded digital videography acquired during aerial surveys of the Brazilian Amazon. Seventeen percent of the study quadrat is occupied by wetlands, which are 96% inundated at high water and 26% inundated at low water (including river and stream channels). Flooded forest constitutes nearly 70% of the wetland area at high water. This mapping methodology is being applied to the entire lowland portion of the basin. In order to map inundation extent at intermediate water stages, and to increase classification accuracy in savanna regions, we are using time series of high-resolution JERS-1 and Radarsat data, and will make extensive use of planned acquisitions from the ENVISAT ASAR and ALOS PALSAR sensors.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Field measurements were combined with Synthetic Aperture Radar (SAR) images to evaluate the use o... more Field measurements were combined with Synthetic Aperture Radar (SAR) images to evaluate the use of radar for estimating biomass changes and mapping of aquatic vegetation in the lower Amazon. Field campaigns were conducted concomitant to the acquisition of Radarsat and JERS-1 images at five different stages of the hydrological cycle. The temporal variability of the SAR data for aquatic vegetation shows a dynamic range of 5 dB, however this is due dominantly to the significant differences ( p <0.05) between the low water season when vegetation is small and just emerging and other seasons when vegetation is fully developed. The spatial variability of the above-water biomass is detectable with radar data. Significant correlation ( p <0.05) exist between backscattering coefficients and both above-water dry biomass and height of the plants. The logarithmic relationship between backscattering coefficients and biomass suggests that (1) at low biomass, high transmissivity of the microwave radiation through the vegetation canopy occurs and the backscattering is a result of quasi-specular reflection of both C and L bands and a minor contribution of canopy volume scattering from C band; (2) at intermediate levels of biomass, moderate changes in backscattering values occur and the saturation point of backscattering is reached; and (3) at high biomass, the transmissivity of C and L band radiation is equally attenuated and backscattering approaches similar values for both. A combination of Radarsat and JERS-1 images from high and low water periods were classified using a segmentation algorithm and had an accuracy higher than 97% for vegetated areas of the floodplain. Although further research is needed to better understand the saturation points for Radarsat and JERS-1 data, these findings clearly show that C and L bands can accurately map aquatic vegetation of the Amazon floodplain.
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Dec 1, 2010
Page 1. 560 IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING, VOL... more Page 1. 560 IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING, VOL. 3, NO. 4, DECEMBER 2010 Using ALOS/PALSAR and RADARSAT-2 to Map Land Cover and Seasonal Inundation in the Brazilian Pantanal ...
The original version of this Article contained an error in the order of the Figures. Figures 1 an... more The original version of this Article contained an error in the order of the Figures. Figures 1 and 2 were published as Figure 4 and 1. As a result, Figures 2 and 3 were renumbered to Figures 3 and 4.
Herbaceous aquatic macrophytes cover extensive areas on the floodplains of the Amazon basin and a... more Herbaceous aquatic macrophytes cover extensive areas on the floodplains of the Amazon basin and are an important habitat and input of organic carbon. These communities have large intra- and inter-annual variability, and characterization of this variability is necessary to quantify the role of macrophytes in the ecology and biogeochemistry of the floodplain. A novel approach for mapping the temporal evolution
ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Jun 17, 2021
The eastern coastline of James Bay (Eeyou Istchee) is known to be home to beds of subarctic eelgr... more The eastern coastline of James Bay (Eeyou Istchee) is known to be home to beds of subarctic eelgrass (Zostera marina L.). These eelgrass beds provide valuable habitat and food source for coastal and marine animals and contribute valuable ecosystem services such as stabilization of the shoreline all along the coast. Despite reports from Cree communities that eelgrass bed health has declined, limited research has been performed to assess and map the spatial distribution of eelgrass within the bay. This study aims to address that issue by evaluating the capability of Landsat-8 Operational Land Imager (OLI) imagery to establish a baseline map of eelgrass distribution in 2019 in the relatively turbid waters of Eeyou Istchee. Three images acquired in September 2019 were merged and classified using Random Forests into the following classes: Eelgrass, Turbid Water, Highly Turbid Water, and Optically Deep Water. The resulting classified image was validated against 108 ground truth data that were obtained from both the eelgrass health and Hydro-Quebec research team. The resulting overall accuracy was 78.7%, indicating the potential of the Random Forests classifier to estimate baseline eelgrass coverage in James Bay using Landsat-8 imagery. This project is part of a Cree driven project, the Coastal Habitat Comprehensive Research Program (CHCRP). The CHCRP aims to combine Cree's traditional knowledge with Western science to better understand environmental changes in the coastal ecosystems and ecosystem services of eastern James Bay. The study is funded by a MITACS grant sponsored by Niskamoon Corporation, an indigenous non-profit organization.
Aquatic herbaceous macrophytes contribute significantly to the input carbon for the Amazon floodp... more Aquatic herbaceous macrophytes contribute significantly to the input carbon for the Amazon floodplain. These plants have large seasonal variations in areal coverage and high productivity. The present study estimates annual net primary production (NPP) of aquatic herbaceous macrophytes in a large lake on the eastern Amazon floodplain, assesses the sources and amount of uncertainty associated with these measures, and offers a comparison among the estimates of herbaceous macrophyte productivity in the Amazon region. Plant biomass accumulated during the rising water stage of the annual flood cycle, peaking at 2300 to 6100 g m 22 and decreasing later in the year. Annual net primary production was estimated to range from 2400 to 3500 g m 22 yr 21 , with above water production between 650 and 1100 g m 22 yr 21 , and below water production between 1700 and 2600 g m 22 yr 21. Echinochloa polystachya and Paspalum fasciculatum were the most productive species, followed by Paspalum repens, Hymenachne amplexicaulis, and Oryza perennis. The four main sources of uncertainty in the estimates were macrophyte taxa, location, sampling design, and lack of measurements of dead material loss.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
RADARSAT S1 and S7, and JERS imagery are integrated with field measurements of geochemistry and c... more RADARSAT S1 and S7, and JERS imagery are integrated with field measurements of geochemistry and characteristics of emergent aquatic vegetation to investigate the potential of SAR data to map fresh and brackish lakes of the Brazilian Pantanal. SAR images can determine emergent aquatic plant assemblages which are controlled by the total dissolved solids and pH of lakes. SAR images can therefore potentially be used to indirectly map the geochemistry of the hundreds of thousands of lakes in the Pantanal. This may be the most feasible way to map lake type in the Pantanal because the area is remote and the lakes are so numerous. The quantities and types of lakes and their spatial distribution is important information for understanding how the Pantanal ecosystem formed, how it works, and what is required to preserve it.
ABSTRACT Nahirnick, N.K.; Costa, M.; Schroeder, S., and Sharma, T., 2020. Long-term eelgrass habi... more ABSTRACT Nahirnick, N.K.; Costa, M.; Schroeder, S., and Sharma, T., 2020. Long-term eelgrass habitat change and associated human impacts on the west coast of Canada. Journal of Coastal Research, 36(1), 30–40. Coconut Creek (Florida), ISSN 0749-0208. Eelgrass (Zostera marina) forms a critical nearshore marine habitat in temperate coastal ecosystems. 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 historical aerial photographs and unoccupied aerial system (UAS) 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 decreased by 45.1%, while meadow complexity as indicated by the shape index increased by 66.3%. Shoreline activities (boats, docks, log booms, and armoring) and residential housing density increased markedly at all sites over the study period and were strongly correlated to eelgrass area coverage and shape index. Changes in these landscape-level indicators over this period corroborate the observed decline in eelgrass habitat condition, because 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.
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