Evaluating biomass of Baltic filamentous cyanobacteria by image analysis

The biovolume of heterocystous cyanobacteria in the Central Baltic Sea was determined in natural, mixed-species samples by image analysis. Epifluorescence microscopy combined with computer-mediated image analysis was used to distinguish phycobiliprotein autofluorescent filaments of Anabaena, Aphanizomenon and Nodularia from other phytoplankters collected on membrane filters. A detailed description is given of the method based on the automatic measurement of single filament morphometry. Manual interactions and mathematical corrections were necessary during image processing to overcome filament overlapping and curvature on filters as well as the coiling of Nodularia spp.. The autofluorescence patchiness of Aphanizomenon sp. made it necessary to trace its dimensions manually. The data obtained were used to estimate variations in the vertical distribution of the biomass of the 3 cyanobacterial genera over a diel cycle

Biofilm cultures to understand Ostreopsis benthic HABs

BIOFILM CULTURES TO UNDERSTAND OSTREOPSIS BENTHIC HABS Roberta Congestri1 ([email protected]), Francesca Di Pippo2 ([email protected]), Patrizia Albertano1 ([email protected]) 1University of Rome “Tor Vergata”, Department of Biology, LBA- Laboratory of Biology of Algae, Via della Ricerca scientifica, 00133 Rome, 2CNR–IAMC, National Research Council, Institute for Coastal Marine Environment, Località Sa Mardini, Torregrande, 09072 Oristano, Italy. An incubator prototype specially designed for culturing aquatic phototrophic biofilms on substrata at controlled environmental conditions was used to perform semi-continuous flow microcosm experiments with microphytobenthos sampled during toxic Ostreopsis ovata outbreaks in summer along the middle Tyrrhenian Sea coast. The system provided the possibility of simultaneously controlling environmental conditions and co-culturing biofilm organisms on a set of artificial substrata in a closed photobioreactor, providing a realistic assessment of community processes and maintaining biofilm integrity during sampling. The design allowed to study the effect of time, site, substratum of in situ growth and the role of key species in community development starting from natural inocula, cultured on polycarbonate slides, in a moving film of K/2 medium (50 L h-1 flow velocity) under controlled temperature (25°C) and light conditions (110 mol photons m-2s-1). Benthic dinoflagellates, diatoms and filamentous cyanobacteria constituted significant fractions, in taxon richness and biomass, of the natural biofilms formed on macroalgae and bryozoans used as inocula. Biofilm cells were all embedded in a common mucilage matrix (EPS, exopolymeric substances). Non-destructive, real time monitoring of biomass accumulation was obtained by recordings of transmittance values by light sensors positioned under the slides. Growth curves indicated that biofilms reached a mature stage in 40 to 50 days. Species accrual, growth and compositional shifts over time were monitored using a variety of microscopical technique, including confocal laser scanning microscopy. Initial adhesion and substratum colonisation appeared as stochastic processes, then community structure and physiognomy, especially of the photosynthetic fraction, visibly changed with time. Prevalence of cyanobacteria at late growth stages was detected in all cultures, which showed complex layering, inner voids and channels. HPLC on matrix sugars revealed variations in total amounts and composition. No toxic compounds were detected in the final communities tested by LC-MS and MALDI-TOF MS techniques

Testing of two different strains of green microalgae for Cu and Ni removal from aqueous media

The concentration of metal ions in aqueous media is a major environmental problem due to their persistence and non-biodegradability that poses hazards to the ecosystem and human health. In this study, the effect of Cu and Ni on the growth of two green microalgal strains, Chlorella vulgaris and Desmodesmus sp., was evaluated along with the removal capacity from single metal solutions (12days exposure; metal concentration range: 1.9-11.9mgL(-1)). Microalgal growth showed to decrease at increasing metal concentrations, but promising metal removal efficiencies were recorded: up to 43% and 39% for Cu by Desmodesmus sp. and C. vulgaris, respectively, with a sorption capacity of 33.4mggDW(-1) for Desmodesmus sp. As for Ni, at the concentration of 5.7mgL(-1), the removal efficiency reached 32% for C. vulgaris and 39% for Desmodesmus sp. In addition, Desmodesmus sp. growth and metal removal were evaluated employing bimetallic solutions. In these tests, the removal efficiency for Cu was higher than that of Ni for all the mix solutions tested with a maximum of 95%, while Ni-removal reached 90% only for the lowest concentrations tested. Results revealed that the biosorption of both metals reached maximum removal levels within the fourth day of incubation (with metal uptakes of 67mgCugDW(-1) and 37mgNigDW(-1)). Intracellular bioaccumulation of metals in Desmodesmus sp. was evaluated by confocal laser scanning microscopy after DAPI staining of cells exposed or not to Cu during their growth. Imaging suggested that Cu is sequestered in polyphosphate bodies within the cells, as observable also in phosphorus deprived cultures. Our results indicate the potential of employing green microalgae for bioremediation of metal-polluted waters, due to their ability to grow in the presence of high metal concentrations and to remove them efficiently

Seasonal succession of phototrophic biofilms in an Italian wastewater treatment plant: Biovolume, spatial structure and exopolysaccharides

A multiphasic approach was applied to investigate the structural features of phototrophic biofilms that grow in a wastewater treatment plant (WWTP) at Fiumicino Airport (Rome, Italy). Seasonal variations in species composition, biomass and exopolysaccharides produced were analyzed by light (LM) and electron microscopy (SEM), high performance liquid chromatography (HPLC) and circular dichroism (CD). Phototroph contribution to the 3-dimensional structure of the biofilm and its development was assessed by confocal laser scanning microscopy. Analysis of biofilms grown on polypropylene slides showed a stable species composition; seasonal changes in biomass were mostly due to changes of major cyanobacterial and algal taxonomic groups. Extensive growth was evident on the range of artificial substrata that were implanted in the treatment plant. CD spectra and HPLC analyses of 2 operationally defined exopolysaccharide fractions extracted from samples scraped off the tank walls revealed that negatively charged heteropolysaccharides comprised most of the matrix and capsular components of the biofilms. Cytochemical staining distinguished between acidic and sulphated residues in the samples observed by LM. The data provide a new insight into the structural integrity and development of phototrophic biofilms in this hyper-eutrophic environment, indicating a potential use of autochthonous consortia in an environmentally sound tertiary water treatment alternative to conventional chemico-physical technologies