lake is meso-eutrophic and belongs to the meromictic type of circulation. The lake
provides an important economic source for the local population mainly in terms of
tourism recreation. It is the first Italian natural lake entirely transformed to a
hydroelectric reservoir in 1929. Throughout the past decade, the progressive
stabilisation of the water levels has enhanced the development, maintenance and
proliferation of dense macrophyte stands all around the littoral zone, as a probable
consequence of nutrient and organic matter accumulation in surface sediments. The
steep slopes surrounding the lake are colonised by a mixed deciduous forest.
Depending on the season, pollens, dead leaves and other terrestrial material might
be easily transported into the air and deposited in the lake.
Beyond the reproductive function, the role of pollen in ecosystems, including
Lake Idro, is poorly investigated. There are few evidences for its trophic function
[85] or for its ability to convey harmful substances and/or toxins. There are
numerous species, genera and families characterised by the production of allergenic
pollen, among these the Pinaceae. The family Pinaceae includes many genera
distributed throughout the Italian territory, anticipated pollen production in late
autumn. An example is represented by Cedrus (such as C. libani and C. deodara), in
the basin of Lake Idro, that during windy days is likely to be also transported on the
water surface.
The accumulation of floating materials on the water surface might lead to
complications for water-related interpretation and studies due to potential problems
of specular reflection and other influences on colour and brightness. Since floating
materials (e.g. plants) might have a significantly different spectra signal from that
of water, the detection of those materials can be remotely sensed. Commonly, the
algorithms which allow those materials to be detected from passive remote sensing
make use of the near-infrared wavelength as it is expected that in this region the
signal coming from water is usually relatively low. Villa et al. [86] showed how
good floating vegetation monitoring capabilities are ensured by the use of simple
and straightforward approaches based on vegetation indices.
Figure 8 shows a deposition phenomenon of terrestrial origin on Lake Idro
observed by MIVIS data acquired on 3 December 2009: because it was early
December, most likely the Cedrus species are responsible for the observed phenomenon. The atmospherically corrected reflectance obtained with ATCOR-4 shows
(cf. pasted graph in Fig. 8) the different behaviour of the signal coming from the
Lake Idro waters with respect to those where the pollen was floating. The spatial
dimension of the phenomenon underlines the possible local impact of the dispersion
of pollen and the role it may have in ecosystems, especially aquatic ecosystems.
74
C. Giardino et al.
provides an important economic source for the local population mainly in terms of
tourism recreation. It is the first Italian natural lake entirely transformed to a
hydroelectric reservoir in 1929. Throughout the past decade, the progressive
stabilisation of the water levels has enhanced the development, maintenance and
proliferation of dense macrophyte stands all around the littoral zone, as a probable
consequence of nutrient and organic matter accumulation in surface sediments. The
steep slopes surrounding the lake are colonised by a mixed deciduous forest.
Depending on the season, pollens, dead leaves and other terrestrial material might
be easily transported into the air and deposited in the lake.
Beyond the reproductive function, the role of pollen in ecosystems, including
Lake Idro, is poorly investigated. There are few evidences for its trophic function
[85] or for its ability to convey harmful substances and/or toxins. There are
numerous species, genera and families characterised by the production of allergenic
pollen, among these the Pinaceae. The family Pinaceae includes many genera
distributed throughout the Italian territory, anticipated pollen production in late
autumn. An example is represented by Cedrus (such as C. libani and C. deodara), in
the basin of Lake Idro, that during windy days is likely to be also transported on the
water surface.
The accumulation of floating materials on the water surface might lead to
complications for water-related interpretation and studies due to potential problems
of specular reflection and other influences on colour and brightness. Since floating
materials (e.g. plants) might have a significantly different spectra signal from that
of water, the detection of those materials can be remotely sensed. Commonly, the
algorithms which allow those materials to be detected from passive remote sensing
make use of the near-infrared wavelength as it is expected that in this region the
signal coming from water is usually relatively low. Villa et al. [86] showed how
good floating vegetation monitoring capabilities are ensured by the use of simple
and straightforward approaches based on vegetation indices.
Figure 8 shows a deposition phenomenon of terrestrial origin on Lake Idro
observed by MIVIS data acquired on 3 December 2009: because it was early
December, most likely the Cedrus species are responsible for the observed phenomenon. The atmospherically corrected reflectance obtained with ATCOR-4 shows
(cf. pasted graph in Fig. 8) the different behaviour of the signal coming from the
Lake Idro waters with respect to those where the pollen was floating. The spatial
dimension of the phenomenon underlines the possible local impact of the dispersion
of pollen and the role it may have in ecosystems, especially aquatic ecosystems.
74
C. Giardino et al.