502
É. L. Simms
The vertical structure of underwater kelp species such as Laminaria and
Fucus is not visible on a vertical image. Remote sensing methods usually derive the
weight biomass of submerged macrophytes from the multispectral reflectance or
radiance values (Grenier, 1987; Lavoie et al., 1991; Armstrong, 1993). The canopy
coverage (horizontal variation) determines the spectral reflectance of submerged kelp
beds, not the vertical structure and the biomass it contains.
The approach presented in this chapter uses remote sensing and field data as a
complement. The kelp biomass, in terms of canopy coverage, was derived from a
remote sensing image and the field data relate the canopy coverage to the wet weight
biomass. rather than using remote sensing as a replacement of field data collection.
The biomass of submerged kelp beds was assessed for an area of Fortune Bay,
Newfoundland. An airborne image was analyzed to extract the area occupied by the
population of macrophytes, and the field data collected characterized the biomass
found in dense kelp beds.
Data
A CASI (Compact Airborne Spectrographic Imager) image was acquired on August
14, 1992 between Fortune and Grand Bank, Newfoundland. The image centered at
47°05’ N latitude and 55°48’ W longitude covers approximately 4 km of coastline.
Light wind and smooth sea state occurred during the flight. Stratus clouds at 1850 m
prescribed that the flight altitude be set to approximately 1500 m. As a result, the data
were acquired at a resolution of 2x2 m, over a ground swath of 1024 m. The selection
of six, 20 nm wide, spectral bands as specified in Table 1 accounted for low light level
due to the overcast weather. Proper coverage of the curved coastline required two flight
lines. The first image covered 3.1 km and the second image 1.4 km. These were
georeferenced in a mosaic image that provided a continuous coverage of the study area.
A private contractor in marine services carried out the field work on
September 15, 1992. The survey included fourteen samples located within the area
classified as kelp beds on the image. The bottom comprised large boulders to small
rocks from 10 m depth to the intertidal zone. There was no measurable quantity of
seaweed in the 6 to 10 m depth zone.
The survey was conducted in water depth varying from 3 to 6 m in
populations anchored on large rocks and boulders. All sites surveyed displayed a
canopy coverage of 95 to 100 %. Gravel and small stones composed the substrate in the
shallower water, from the intertidal zone to 3 m depth, between the boulders having
little algal growth.
É. L. Simms
The vertical structure of underwater kelp species such as Laminaria and
Fucus is not visible on a vertical image. Remote sensing methods usually derive the
weight biomass of submerged macrophytes from the multispectral reflectance or
radiance values (Grenier, 1987; Lavoie et al., 1991; Armstrong, 1993). The canopy
coverage (horizontal variation) determines the spectral reflectance of submerged kelp
beds, not the vertical structure and the biomass it contains.
The approach presented in this chapter uses remote sensing and field data as a
complement. The kelp biomass, in terms of canopy coverage, was derived from a
remote sensing image and the field data relate the canopy coverage to the wet weight
biomass. rather than using remote sensing as a replacement of field data collection.
The biomass of submerged kelp beds was assessed for an area of Fortune Bay,
Newfoundland. An airborne image was analyzed to extract the area occupied by the
population of macrophytes, and the field data collected characterized the biomass
found in dense kelp beds.
Data
A CASI (Compact Airborne Spectrographic Imager) image was acquired on August
14, 1992 between Fortune and Grand Bank, Newfoundland. The image centered at
47°05’ N latitude and 55°48’ W longitude covers approximately 4 km of coastline.
Light wind and smooth sea state occurred during the flight. Stratus clouds at 1850 m
prescribed that the flight altitude be set to approximately 1500 m. As a result, the data
were acquired at a resolution of 2x2 m, over a ground swath of 1024 m. The selection
of six, 20 nm wide, spectral bands as specified in Table 1 accounted for low light level
due to the overcast weather. Proper coverage of the curved coastline required two flight
lines. The first image covered 3.1 km and the second image 1.4 km. These were
georeferenced in a mosaic image that provided a continuous coverage of the study area.
A private contractor in marine services carried out the field work on
September 15, 1992. The survey included fourteen samples located within the area
classified as kelp beds on the image. The bottom comprised large boulders to small
rocks from 10 m depth to the intertidal zone. There was no measurable quantity of
seaweed in the 6 to 10 m depth zone.
The survey was conducted in water depth varying from 3 to 6 m in
populations anchored on large rocks and boulders. All sites surveyed displayed a
canopy coverage of 95 to 100 %. Gravel and small stones composed the substrate in the
shallower water, from the intertidal zone to 3 m depth, between the boulders having
little algal growth.