Abstract
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.
Highlights
Cyanobacteria, a class of photosynthetic microbes, have a long evolutionary history, starting about 3-3.5 billion years ago (Whitton and Potts, 2000)
Reliable mapping of the cyanobacterial community is of importance in the coastal waters and inland seas, such as the Baltic Sea
To obtain detailed fluorescence features of Polycyclic Aromatic Hydrocarbons (PAHs), oil samples were pipetted into sample well plates and measured with a fiber-optic attachment on the same Perkin Elmer LS55 spectrometer (PE-LS55)
Summary
Cyanobacteria, a class of photosynthetic microbes, have a long evolutionary history, starting about 3-3.5 billion years ago (Whitton and Potts, 2000). 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. The frequency and extent of intense cyanobacterial blooms have increased in inland and coastal waters around the world (Kahru, 1997) These blooms have potentially harmful effects on both humans and the flora and fauna, and 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). Reliable mapping of the cyanobacterial community is of importance in the coastal waters and inland seas, such as the Baltic Sea
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