A study of a cyanobacterial bloom in the Albert Dock in Preston, Lancashire, UK

Abstract

An account is presented of work undertaken relating to a cyanobacterial bloom which occurs during the late Spring and Summer months in the Albert Dock at Preston in Lancashire. The causal organism has been identified as P1anktothrix (Oscillatoria) agardhii. Attempts at the purification of the causal organism from dock samples were only partially successful due to the lack of time available.
However, the maintenance of crude cultures and axenic cultures acquired from culture collections was successfully achieved using Jaworski's Medium. MALDI TOF MS (Matrix-Assisted Laser Desorption I tonisation Time Of Flight Mass Spectrometry) was used to obtain characteristic mass spectral fingerprints of the strains analysed, which were fed into databases. The results show that it is possible to discriminate between strains of the same species and to show the relationship between the causal organism and the other available axenic cultures of Planktothrix species. A dendrogram, produced by comparing of mass spectral fingerprints of the strains is presented, which shows that two groups could be discriminated using MALDI TOF MS with the Preston Dock isolate being the most distantly related strain. Strains PCC 7805 and PCC 7811 are shown to be
more closely related to the CEll Windermere strain CCAP 1459/23.
A growth measuring technique is described in which a computer programme is used to measure the total filament length of this microorganism in a known volume of sample (rn/cm). The technique, which uses photographic images of filaments taken in a Neubauer haemocytometer, provides a method for measuring straight and curved filaments. The results show that the technique is a suitable and reliable assay method.
A method for estimation chlorophyll a is described. It is used to quantify the presence of cyanobacteria in samples. The results of this technique when compared to those for measuring of filament length show that there was no direct relationship between filament length and chlorophyll a content
The results of visualisation studies using fluorochromes, demonstrate the use of acridine orange (AO) and 4'6-diamidino-2-phenylindole dihydrochloride (DAPI) to visualise cells, and the use of propidium iodide (P1) to identify viable cells. It is
suggested that AO may be used to provide information on the physiological state of filaments at the time of sampling.
These techniques were applied to assess the efficacy of a biocide preparation. A consensus of re-growth and viability experiments of biocide treated samples show that the concentration at which the stabilised biocide inhibited the growth
of Planktothrix (Osdilatoria) agardhi4 was in the range of 50-100 ppm, whilst the non-stabilised form was effective only in the 150-200 ppm range.