Grimes et al. (2014) discuss methods of observing Vibrios’ and Cyanobacteria using remote sensing, discussing the environmental drivers
associated with such monitoring. They also discuss its applications and
significance with reference to multiple case studies.
Most data is recorded passively by satellites using the
colour sensors (recording light/heat) to detect changes blooms (i.e. monitoring
chlorophyll types/auxillajry pigments).
Remote sensing is ultimately easier, quicker, and cheaper way
of gaining information than research vessels, though it’ findings currently need
to be validated by such means.
A limitation of remote sensing is that about 90-95% of light
detected by the sensor is light scattered by the atmosphere and not of oceanic
origin, and must be extracted. This is considerably harder in coastal waters
due to the heterogeneity of the water content, and the atmosphere surrounding
it. This issue remains one of the biggest uncertainties surrounding remote
sensing.
A further complication is that certain measurements are
easier to make with remote sensing than others. For instance sea surface
temperature (SST) is relatively easy to measure, while sea surface salinity
cannot be measured closer than 200km to the coast. Developments in satellite
technology i.e. the GEO-CAPE planned for US coastal waters, with higher spatial
resolution will likely allow for coastal measurements, hopefully allowing more
accurate predictions of blooms and vibrios proliferation.
A common and well known vibrio that remote sensing is used
to detect is Vibrio cholorea. Most of
the work concerning this organism has taken place in the Bay of Bengal but
other promising research in east and South Africa has shown interesting
results. Research shows that just one
environmental variable used to estimate blooms isn’t completely accurate and
that it is only used as an indicator of blooms. However work in East Africa has shown sea surface temperatures to have
less than a month lag when predicting V.
cholerae blooms. Studies have shown that the occurrence of V. cholerae are associated with up
welling of cold water and with increased run off from rivers containing
terrestrial nutrients.
Combined with data for viewing Vibrio parahaemolyticus, for which SST is also a primary environmental driver the general conclusion for this kind of data is for use as an
early warning system for outbreaks of such pathogens. In the case of V. parahaemolyticus studies have been
undertaken combining remote sensing data with the continuous plankton recorder
data (1961-1995), (amongst other such surveys) in order to give estimations for
future levels of vibrio with rising sea temperatures. This is of particular
importance for areas such as Northern Europe
which has the some of fastest rising temperatures (studies concerning Vibrio vulnificus).
Other applications of remote sensing include the detection
of ocean colour which can help understand the role of ocean picoplankton
populations in the global carbon cycle. Achievement noted in this area include
differentiation of Trichhodesmium
from clouds, the characterisation of Nodularia
(a cyanobacteria associated with two nasty toxins) and understanding of its
formation and migration, and detecting Mycrocytis
in lakes which has implications with drinking water safety.
In other cases Bioluminescence of Vibrio harveyi can be used for mapping chemical contamination on a
coastal scale using a bioluminescent to total bacteria scale. There is no
published literature on this but satellites exist are likely able to be applied
to this type of work. Harmful algal blooms have also been detected for many
years, helping to warn of harmful toxins produced by them for coastal
communities.
Grimes, D. J., Ford, T.
E., Colwell, R. R., Baker-Austin, C., Martinez-Urtaza, J., Subramaniam,
A., & Capone, D. G. (2014). Viewing Marine Bacteria, Their Activity
and Response to Environmental Drivers from Orbit. Microbial Ecology, 1-12.
No comments:
Post a Comment