title: Seasonal changes on microbial metabolism and biomass in the euphotic layer of Sicilian Channel.
abstract: As a part of a wider project on fisheries ecology, several biological and environmental parameters were monitored during two oceanographic cruises (BANSIC 2012 and NOVESAR 2013) in the Sicily Channel, which connects the Western and Eastern Mediterranean basins. The prokaryotic abundances and biomass as well as hydrolysis rates on organic matter were investigated in the euphotic layer of a retention area for fish larval stages including anchovy (Engraulis encrasicolus, Linnaeus, 1758) with the aim to investigate the different biogeochemical signatures in two seasonal conditions. The environmental parameters, particulate organic carbon and nitrogen together with heterotrophic production were also measured. Results showed significant increases for most of the studied parameters with increasing temperature during summer. This had effects on the Carbon cycle and recycling of nutrients; in fact total prokaryotic abundance and biomass, as well as carbon hydrolyzed by two enzymes (Leucine aminopeptidase and β-glucosidase), increased significantly during summer. Conversely Alkaline phosphatase activity, Chlorophyll concentration and Oxygen increased during winter. The same environmental parameters affected also the presence of fish eggs. Moreover high percentages of free enzymes (i.e., enzymes not associated with cells) were measured, accounting for percentages variable from 12 to 95 % of the total enzymatic activity, with values generally higher in summer than in winter. In this oligotrophic environment, the prokaryotic biomass was supported by the C hydrolyzed by enzymatic activities. The ratio between the hydrolyzed C and prokaryotic biomass was higher in winter than in summer, indicating that alkaline phosphatase activity contribute to an efficient incorporation of C into biomass in winter.
authors.affiliation: CNR-IAMC, Spianata S. Raineri, 86, 98122 Messina, Italy. Electronic address: renata.zaccone@iamc.cnr.it.
authors.forename: R
authors.initials: R
authors.lastname: Zaccone
authors.affiliation: CNR-IAMC, Spianata S. Raineri, 86, 98122 Messina, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Caruso
authors.affiliation: CNR-IAMC, Spianata S. Raineri, 86, 98122 Messina, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Leonardi
authors.affiliation: CNR-IAMC, Spianata S. Raineri, 86, 98122 Messina, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Maimone
authors.affiliation: CNR-IAMC, Spianata S. Raineri, 86, 98122 Messina, Italy.
authors.forename: L S
authors.initials: LS
authors.lastname: Monticelli
authors.affiliation: CNR-IAMC, Spianata S. Raineri, 86, 98122 Messina, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Azzaro
authors.affiliation: CNR-IAMC, Via del Mare, 3, 91021 Capo Granitola, TP, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Cuttitta
authors.affiliation: CNR-IAMC, Via del Mare, 3, 91021 Capo Granitola, TP, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Patti
authors.affiliation: CNR-IAMC, Spianata S. Raineri, 86, 98122 Messina, Italy.
authors.forename: R
authors.initials: R
authors.lastname: La Ferla
mesh_terms: D001105:Archaea / Q000502:physiology*; D018407:Bacterial Physiological Phenomena; D018533:Biomass; D007558:Italy; D008522:Mediterranean Sea; D012621:Seasons; D012623:Seawater / Q000737:chemistry*
keywords: Carbon cycle; Enzymatic activities; Mediterranean Sea; Prokaryotic biomass; Seasonal variations