Estimate of algal biomass in two Mediterranean lagoons: shifting between planktonic and macroalgal production.

Abstract

The results presented in this work are part of a pilot project aimed at the evaluation of the potential biodiesel production from algal biomass. Specifically, macroalgal and phytoplanktonic biomass of two Italian lagoon, Orbetello (north Tyrrhenian Sea) and Lesina (south Adriatic Sea), regarded as highly productive and eutrophic, were monitored in spring and summer 2011 and 2012. The study has been divided in two main sections. Firstly, a general qualitative outline of the submerged vegetation distribution by visual census techniques was conducted. Secondly, macroalgae and water samples for chlorophyll a determination were collected in order to study the primary production (in Kg.m-2 and ?g.L-1 for macroalgae and phytoplankton, respectively). Accordingly the lagoons have been divided into transects oriented according to the direction NS and WE. We obtained a total of 18 transects oriented in NW-SE direction in the Orbetello (8 in the western basin and 10 in the eastern basin) and 13 in the Lesina (10 of them in the "Sacca Orientale"). At the same time, physico-chemical parameters were measured by multiparametric probe. The results show a basic difference between the two systems, with a productivity shift towards phytoplankton biomass in Lesina and macroalgae in Orbetello. In Lesina, mean concentrations of chlorophyll a were 2.97 ± 3.63 ?g.L-1 (spring, with maximum of 15.27??g.L-1) and 2.36 ± 2.60 ?g.L-1 (summer, with peak of 12??g.L-1), while macroalgal biomass ranged from 1.9 to 2.6 kg.m-2 for both observation periods. Conversely, in Orbetello lagoon mean phytoplanktonic chlorophyll a did not exceed the level of 0.51 ±0.31 ?g.L-1 in spring and 0.81 ± 0.70 ?g.L-1 in summer (with maximum of 3.21 ?g.L-1), while biomass of submerged vegetation was always an order of magnitude greater. In particular, macroalgal biomass was higher in the western basin than in the Eastern one with mean values that increased from spring (28.2 Kg.m-2) to summer (66.1 kg.m-2). This study indicates that the high macroalgal production in Orbetello lagoon could be evaluated for biodiesel production, while in Lesina the macroalgae distribution is more casual e quantitatively less abundant.


Tutti gli autori

  • Specchiulli A.; Borghini F.; Cassin D.; D'Adamo R.; Fabbrocini A.; Fanello E.; Penna P.; Scirocco T.; Bastianoni S.

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Anno di pubblicazione

2013

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