Chapter 7: APPLICATIONS
oxygen in seawater form highly reactive chemical compounds including
hydrogen peroxide and hydroxyl radicals. Another type of secondary
reaction occurs between “excited” CDOM and other chemical compounds
such as trace metals and sulfur compounds. Since CDOM strongly absorbs
the solar radiation in the UV, it regulates the penetration depth of the
biologically harmful UV radiation into the ocean (Zepp et al., 1995).
A complex mixture of photochemical reaction products (reactive oxygen
species, inorganic nutrients, and trace gases) accumulates in the near-surface
layer of the ocean affecting the biological availability of dissolved organic
matter as well as the optical properties of surface water. Remotely sensed
spectral radiance can therefore provide estimates of CDOM absorption and
concentration (Bissett et al., 2001).
An interesting phenomenon, sometimes observed in the upper ocean, is
the formation of thin biologically active layers. The layers of phytoplankton,
zooplankton, and marine snow ranging from a few cm to a few m thick,
extending up to many km horizontally, and lasting for days have been
reported in estuaries, fjords, and coastal shelves (Donaghay et al., 1992;
Rines et al., 2002). These thin layers may have elevated levels of nutrient
uptake, increased intensity of competition and predation, higher
accumulation of chemical waters and toxins, and higher levels of microbial
degradation and remineralization than found in the seawater immediately
above and below them (Sieburth and Donaghay 1993). The thin layers also
affect optical and acoustical characteristics of the upper ocean (see Section
Alldredge et al. (2002) observed thin layers of phytoplankton and marine
snow and in the distributions of associated zooplankton in the near-surface
layer of a shallow fjord (Figure 7-8). Four days before the measurements
shown in Figure 7-8, strong winds advected a plume of fresher and warmer
water (generated by a river) into the experimental area. The wind speed then
dropped to 1 - 1.5 m s
-1 .
Profiles of physical and optical structure suggest that the position of thin
biota layers was related to the near-surface pycnocline. There are two
distinct thin layers in Figure 7-8. The thin layer associated with
phytoplankton fluorescence is at the bottom of the near-surface mixed layer
(~ 3 m depth). There is also a layer of marine snow, an accumulation of
microscopic aggregates of detritus particulate matter > 0.5 mm in diameter,
which occurred about 1.5 to 2 m below the layer of high fluorescence.
The data shown in Figure 7-8 was obtained under low wind speed
conditions. When wind increased later, the snow layer and phytoplankton
layers merged.
There was a pattern of maximum zooplankton abundance in the surface
layer and minimum abundance within the marine snow layer. Zooplankton
457
7.4).
oxygen in seawater form highly reactive chemical compounds including
hydrogen peroxide and hydroxyl radicals. Another type of secondary
reaction occurs between “excited” CDOM and other chemical compounds
such as trace metals and sulfur compounds. Since CDOM strongly absorbs
the solar radiation in the UV, it regulates the penetration depth of the
biologically harmful UV radiation into the ocean (Zepp et al., 1995).
A complex mixture of photochemical reaction products (reactive oxygen
species, inorganic nutrients, and trace gases) accumulates in the near-surface
layer of the ocean affecting the biological availability of dissolved organic
matter as well as the optical properties of surface water. Remotely sensed
spectral radiance can therefore provide estimates of CDOM absorption and
concentration (Bissett et al., 2001).
An interesting phenomenon, sometimes observed in the upper ocean, is
the formation of thin biologically active layers. The layers of phytoplankton,
zooplankton, and marine snow ranging from a few cm to a few m thick,
extending up to many km horizontally, and lasting for days have been
reported in estuaries, fjords, and coastal shelves (Donaghay et al., 1992;
Rines et al., 2002). These thin layers may have elevated levels of nutrient
uptake, increased intensity of competition and predation, higher
accumulation of chemical waters and toxins, and higher levels of microbial
degradation and remineralization than found in the seawater immediately
above and below them (Sieburth and Donaghay 1993). The thin layers also
affect optical and acoustical characteristics of the upper ocean (see Section
Alldredge et al. (2002) observed thin layers of phytoplankton and marine
snow and in the distributions of associated zooplankton in the near-surface
layer of a shallow fjord (Figure 7-8). Four days before the measurements
shown in Figure 7-8, strong winds advected a plume of fresher and warmer
water (generated by a river) into the experimental area. The wind speed then
dropped to 1 - 1.5 m s
-1 .
Profiles of physical and optical structure suggest that the position of thin
biota layers was related to the near-surface pycnocline. There are two
distinct thin layers in Figure 7-8. The thin layer associated with
phytoplankton fluorescence is at the bottom of the near-surface mixed layer
(~ 3 m depth). There is also a layer of marine snow, an accumulation of
microscopic aggregates of detritus particulate matter > 0.5 mm in diameter,
which occurred about 1.5 to 2 m below the layer of high fluorescence.
The data shown in Figure 7-8 was obtained under low wind speed
conditions. When wind increased later, the snow layer and phytoplankton
layers merged.
There was a pattern of maximum zooplankton abundance in the surface
layer and minimum abundance within the marine snow layer. Zooplankton
457
7.4).