Geography Reference
In-Depth Information
17.4.1 Direct visualisationof stress (or itseffects)
At trace concentrations, copper is an essential micronutri-
ent for most living organisms, because it is important for
many biologically important reactions. However, copper
can become highly cytotoxic if accumulated in excess of
cellular needs (e.g. causing oxidative damage). Nanoscale
secondary-ion mass spectrometry has been able to detect
and visualise the copper-ion distribution in microal-
gal cells exposed to copper (Slaveykova et al., 2009;
Figure 17.13).
Variations of the physiological characteristics (e.g.
under factors of stress) of macrophytes can be inferred
from their spectral response during reflectance measure-
ments, due to alterations in optically active substances
(e.g. chlorophyll concentration, chemical composition,
photosynthetic efficiency) under environmental pressures
(see a review in Silva et al., 2008). At a smaller scale, plant
damage due to herbivory (or other factors of stress) can
be assessed from simple IA (e.g. quantification of leaf area
removed or damaged plants: O'Neal et al., 2002) or more
complex investigations (e.g. chlorophyll fluorescence or
thermal imaging: Aldea et al. 2006).
The analysis of molluscan internal organs is widely
utilized for biomonitoring purposes. For example, mol-
luscan kidneys are able to excrete solids in the urine in
the form of concretions and it is thought that increased
formation of these concretions occur under stresses such
as toxic exposure. Klobucar et al. (2001) examined the
formation of such concretions in the kidney of the fresh-
water snail Planorbarius corneus experimentally exposed
to pentachlorophenol (PCP). IA of the PCP-exposed indi-
viduals revealed significantly enhanced production of the
kidney concretions (e.g. number of kidney concretions
and area of the concretions) when compared to control
individuals. After manual segmentation of microscopic
images, Giamberini and Cajaraville (2005) showed the
general activation of the lysosomal system, including an
increase in both the number and the size of lysosomes,
in the digestive gland cells of the zebra mussel ( Dreissena
polymorpha ) experimentally exposed to cadmium. This
type of IA can also be used for in situ experiments to
examine the effects of toxic exposure on specific organs
(e.g. Guerlet et al., 2006).
To enlarge the range of potential sentinel species,
Guerlet et al. (2008), utilised histochemistry coupled to
IA, to assess the spatial and temporal (monthly) morpho-
logical variations of four cellular compartments and their
contents in the hepatopancreatic caeca of the freshwater
Figure 17.12 Automatic detection (before counting) of Greater
Flamingos ( Phoenicopterus Roseus ) from a low-resolution aerial
image (from Descamps et al., 2008). Each pink circle represents
a specimen. Reproduced with permission from Descamps, S. et
al. (2008) Automatic flamingo detection using a multiple birth
and death process. In Proc. IEEE International Conference on
Acoustics, Speech and Signal Processing (ICASSP), Las Vegas,
March 2008.
©
INRIA/Tour du Valat.
As a complement to counting, imagery may also allow
the estimation of fish biomass, which provides useful
information for ecological or applied studies. Hockaday
et al. (2000) demonstrated that individual fish biomass
can be accurately estimated from truss dimensions. Ruff
et al. (1995) described a non-invasive technology based
on optical stereo visualisation and computer IA for con-
tinuous monitoring of size, position, shape, and spatial
orientation of single fish among many others. Stereo IA
requires two views of a fish, so that a point on the fish in
one 2D image may be matched with the corresponding
point in the second image. Given a calibration of the
optical arrangement of the system, the coordinates of
these two points may be used to directly estimate the
3D coordinates. Using this technique, fish dimensions
could be measured to millimeter accuracy and fish could
be tracked over limited time intervals to observe detailed
movement. This underwater stereo IA technique was used
to estimate key dimensions of free-swimming fish (Tillett
et al., 2000), from which fish mass could be estimated
(Lines et al., 2001).
17.4 Detection of stress and diseases
Visual inspection of the appearance and/or the activity of
animals and plants can provide a variety of information
regarding their health and development, or the presence
of potential factors of stress in their environment.
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