Abstract
Biofouling on artificial and biotic solid substrata was studied in several locations in the Baltic Sea brackish water (Gulf of Gdansk) during a three-year period with contact angle wettability, confocal microscopy and photoacoustic spectroscopy techniques. As a reference, the trophic state of water body was determined from chemical analyses according to the following parameters: pH, dissolved O2, phosphate, nitrite, nitrate, ammonium etc. concentrations and further correlated to the determined biofilm characterizing parameters by means of Spearman’s rank correlation procedure. Biofilm adhesive surface properties (surface free energy, work of adhesion etc.) were obtained with the contact angle hysteresis (CAH) approach using an automatic captive bubble solid surface wettability sensor assigned for in-situ, on-line and quasi-continuous measurements of permanently submerged samples (Pogorzelski et al., 2013, Pogorzelski and Szczepańska, 2014). Structural and morphological biofilm features (biovolume, substratum coverage, area to volume ratio, spatial spreading, mean thickness and roughness) were determined from confocal reflection microscopy (COCRM) data. Photosynthetic properties (photosynthetic energy storage (ES), photoacoustic amplitude and phase spectra) of biofilm communities exhibited a seasonal variability as indicated by a novel closed-cell type photoacoustic spectroscopy (PAS) system. That allowed mathematical modeling of a marine biofilm under steady state, in particular the specific growth rates μi, and the conditioning or induction times λi to be derived from simultaneous multitechnique signals. A set of the established biofilm structural and physical parameters could be modern water body trophic state indexes.
Highlights
In the previous marine biofilm wettability studies), dynamics of the selected parameters variability, for samples registered in the short-time marine biofilm formation interval, is depicted in Figures 3A–D of Pogorzelski and Szczepanska (2014)
It was evidenced that CAH less than 10◦Could lead to removal of biofilm covering submerged macrophyte leaf blades by shear water flow (Genzer and Efimenko, 2006)
In-situ and on-line measurements can be performed on permanently submerged solid substrata, so-called biointerfaces
Summary
The characteristic formation time scale is apparently related to the length scale of the organisms forming the biofilm colony on solid submersed surfaces (Figure 1B). The biofilm development at solid substrata in aquatic environments is presented as a sequence of phases starting from the formation of a conditioning film via microfouling to complex mature macrofouling organisms community. Various time scales for biofilm-related processes were found (Picioreanu et al, 1998). Periphyton is a complex mixture of algae, cyanobacteria, heterotrophic microbes, and detritus this is attached to submerged surfaces in most aquatic ecosystems (Dang and Lovell, 2016). EPS is critical in the formation of microcolony aggregates acting as a binding hydrated and heterogeneous matrix or “glue” which holds microbes together, and bind them to the submersed substratum (Flemming, 2009).
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