3, 2012
WR.
ile).
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
FLUORESCENT ANALYSIS OF PHOTOSYNTHETIC MICROBES AND POLYCYCLIC
AROMATIC HYDROCARBONS LINKED TO OPTICAL REMOTE SENSING
D. Zhang “*, J.-P. Muller “, S. Lavender ^ D. Walton * L.R. Dartnell *?
* Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, UK
^ ARGANS Ltd, Tamar Science Park, Plymouth, UK
* UCL Institute for Origins, University College London, Gower Street, London WCIE 6B, UK
4 The Centre for Planetary Sciences at UCL/Birkbeck, Earth Sciences, University College London, Gower Street, London WCIE 6B,
daz@mssl.ucl.ac.uk
Commission VIII/9: Oceans
KEY WORDS: Fluorescence, Excitation-Emission Matrix, Cyanobacteria, Crude oil, PAHs
ABSTRACT:
Fluorescence analysis, being a non-invasive technique, has become one of the most powerful and widely used techniques for
microbiologists and chemists to study various types of sample from photosynthetic microbes to hydrocarbons. The work reported
here focuses on experimental results of fluorescent features of photosynthetic microbial species (cyanobacteria) and also five
different crude oil samples. The cyanobacteria samples were collected from the Baltic Sea at the end of July 2011 and were
associated with cyanobacterial bloom events, and the crude oil samples were from various oil spill events. The aim of the study was
to find fluorescent biosignatures of cyanobacteria (initially a species specific to the Baltic Sea) and the fingerprints of crude oil; oil
spills can be difficult to differentiate from biogenic films when using Synthetic Aperture Radar (SAR) or sunglint contaminated
optical imagery. All samples were measured using a Perkin Elmer LS55 Luminescence spectrometer over a broad range of excitation
and emission wavelength from ultraviolet (UV) to near infrared (NIR). The results are presented in Excitation Emission Matrices
(EEMs) that exhibit the fluorescent features of each sample. In the EEM of the seawater sample containing cyanobacteria, there is an
intense emission peak from tryptophan with fluorescent excitation and emission peaks at 285 and 345 nm respectively. In addition,
fluorescent signatures of phycocyanin and chlorophyll-a are present with excitation and emission centre wavelengths at 555 nm, 645
nm and 390 nm, 685 nm, respectively. Additionally, the fluorescence signatures of Polycyclic Aromatic Hydrocarbons (PAHs) are
present in the EEMs of crude oil samples with excitation and emission peaks at 285 nm and 425 nm. This study underpins further
research on how to distinguish cyanobacteria species by their fluorescence signatures and the potential role that PAHs play in
detection of cyanobacteria fluorescence features.
1. INTRODUCTION
Cyanobacteria, a class of photosynthetic microbes, have a long
evolutionary history, starting about 3-3.5 billion years ago
(Whitton and Potts, 2000). Cyanobacteria that obtain energy
through oxygenic photosynthesis are ubiquitous in almost all
ecosystem habitats on the earth from temperate regions such as
oceans to extreme environments i.e. deserts and the dry valleys
of Antarctica.
Cyanobacteria were able to dominate the oceans after past mass
extinction events. They can evolve under anoxic (low oxygen)
conditions and are well adapted to environmental stress
including exposure to UV, high solar flux, nuclear radiation and
temperatures. Cyanobacteria assimilate carbon dioxide, playing
a significant role in the carbon cycle that impacts climate
change. Additionally, the frequency and extent of intense
cyanobacterial blooms have increased in inland and coastal
waters around the world (Kahru, 1997). These blooms not only
have potentially harmful effects on both humans and the flora
and fauna, but also the environment at large e.g. surface
accumulations of cyanobacteria increase sea surface
temperature in areas such as the southern Baltic Sea (Kahru et
al, 1993). Therefore, reliable mapping of the cyanobacterial
community is of importance in the coastal waters and inland
seas, such as the Baltic Sea.
Polycyclic Aromatic Hydrocarbons (PAHs) are a large group of
organic compounds containing two or more aromatic rings.
PAHs exist on the Earth as a result of previous meteoritic
bombardment and more recently from fossil fuel combustion
and by-products of industrial processing. They are commonly
found in a variety of naturally occurring products such as crude
oil and petroleum gas. There are several pathways (Cerniglia,
1992) that PAHs can be used to enter into ecosystems, i.e. direct
aerial fallout, sewage effluents, natural seeps and accidental
discharges during the transport, use and disposal of petroleum
products and from events such as oil spills, one of which
recently occurred in The Gulf of Mexico after the explosion of
the Deepwater Horizon oil rig and the subsequent release of
approximately 780,000 m? of crude oil into the Gulf (Mitsch,
2010). This release resulted in extensive damage to the marine
environment and wildlife habitats. It is therefore urgent to be
able to monitor the migration of oil slicks on the sea surface and
find out an effective and environmental friendly means to clean
up the oil spill. On the other hand, the capability of
cyanobacteria in terms of reduction and degradation of PAHs
has been shown by several researchers (Cerniglia et al., 1980;
Cerniglia, 1992; Steinbüchel et al. 1997; Abed and Koster
2005).
In this research, the fluorescent properties of a seawater sample
(cyanobacterial bloom in the Baltic Sea) together with a series
of crude oils from various oil spill events are discussed. The
