Supervisors info:
Οικονόμου-Αμίλλη Αθηνά, Ομότιμη Καθηγήτρια, Τμήμα Βιολογίας, ΕΚΠΑ
Summary:
Marine phytoplankton is used widely in intensive cultures of bivalves, rotifer rearing and pseudo-green waters in marine fin-fish hatcheries as well as in other minor applications in terms of volumes. Normally these cultures are based on one selected species with high cost to keep the cultures unialgal indoors while the options to deploy them outdoors are very limited due to high risks of crushing due to contamination and/or large fluctuations of environmental conditions. A cheap alternative is to use natural inflows of seawater, coarse filtered to avoid predators and seaweeds, enriched with nutrients and let to thrive until high concentrations.
The phytoplankton species, which can be found in the natural populations, in most cases, have grown together and survived for periods of 15-20 days before one or two species becoming overwhelmingly dominant.
In theory, mixed cultures satisfy the need of a cost–effective marine microalgae production. They are suitable solutions against the high cost and contamination effects caused by monoculture production. Additionally, the large variety of blooms in mixed cultures is usable for the development of different species.
Οbjective of the current study is the production of marine microalgae biomass for further use in aquacultures by applying appropriate techniques of natural algal bloom development and the isolation and characterization of the domain species.
In this study, water was used as described above from three locations in the South Aegean Sea (Saronic Gulf, Euboic Gulf, Aegean part of Evia Island) at two distinct media strengths (1.18 - 2.36 mM NO3-; 0.145-0.29 mM PO43-), all the rest as in Conway medium, Walne 1970) in 1.5 L bottles. Phytoplankton present in the water was left to thrive until a dense bloom occurred. Successful blooms were then diluted in triplicates and left to bloom repeatedly monitoring the biomass production and species composition (dry weight, abundance and biovolume of each species apparently present in daily sampling). Bottles were placed under sufficient light (65 μmol photons m-2s-1) of 12:12 h L:D photoperiod, 20±1˚C and nutrients as in Conway medium at natural salinity of 38 units. Dominating species were isolated, identified to the most possible taxonomic level and characterised (kinetics, chemical composition). The overall score of each bloom was then characterised in terms of abundance, biomass and fatty acid profile.
Stable and adequately productive natural blooms of marine phytoplankton were produced in lab scale cultures from sea water collected in different locations of the Aegean Sea at different seasons. At large scale this technique might provide cheap algae biomass needed for several applications in aquaculture and other uses.
Keywords:
Natural Algae Blooms - NAB, fatty acid, PCR, isolation, aquaculture
