MICROBIAL METABOLISM AND TURNOVER OF ORGANIC MATTER IN THE EUPHOTIC LAYER OF SICILIAN CHANNEL Zaccone R.1, La Ferla R.1, Caruso G.1, Monticelli L.S.1, Maimone G.1, Leonardi M.1, Cuttitta A.2, Patti B.2 1CNR,
IAMC Messina, Italy; 2 IAMC, Capo Granitola (TP), Italy
[email protected]
Background: Knowledge of microbial metabolism in the Sicilian channel is still limited or absent. To provide an ecosystem approach to fisheries management, the monitoring of biological and environmental parameters was carried out during two oceanographic cruises (BANSIC 2012- NOVESAR 13) performed in the Sicilian Channel in different seasonal conditions. The aims were: 1. To determine the prokaryotic abundance and biomass, their metabolic activities on organic matter at three selected stations in the euphotic layer in an area of anchovy (Engraulis encrasicolus) spawning. 2. To quantify the turnover of organic carbon through the prokaryotic community
Sampling site and stations
NOVESAR 2013, January 26 BANSIC 2012, July 20-21 Stations
Depth layer (m) 0 - 25
n°Larvae m-3 0,0
n°Eggs m-3 0,2
137
0 - 15 15 - 25 25 - 60
0,1 0,0 0,0
4,2 0,8 0,1
22
0 - 10 10 - 20
0,0 0,0
10,6 7,9
188
Salinity 38.0 - 38.4
Temperature °C 18.1 - 26.9
Oxygen mg/l 6.37 - 8.15
38.3 - 38.4 38.1 - 38.3 38.1 - 38.5
26. - 26.1 19.1 - 26.0 15.0 - 19.1
6.37 - 6.44 6.63 - 8.21 7.22 - 8.21
38.2 - 38.3 37.9 - 38.3
26.2 - 26.3 19.6 - 26.2
6.38 - 6.43 6.41 - 7.67
Significant differences observed by ANOVA (F-test and P) between July 2012 and January 2013, in the values of physical, chemical and biological parameters Variable Temperature Salinity Oxygen Fluorescence Prokaryotic abundance Prokaryotic Biomass Picophytoplankton abundance Picophytoplankton biomass Leucine- aminopeptidase ß-Glucosidase Alkaline phosphatase Dissolved LAP Dissolved GLU
Carbon cycle in the ocean, from Herndl and Reinthaler, 2013
Seasonal fluctuations in PA, PPPA and biomass were evident when comparing warm vs cold periods (Table ANOVA). The Pearson’s coefficients of correlation showed that PA, PPPA and biomass were significantly related to prokaryotic heterotrophic production (PHP) and Ox during summer. In winter significant correlations were also found with AP.
Prokaryotic Heterotrophic Production (PHP) in July
Abbreviation T S Ox Chl PA PB PPPA PPPB LAP GLU AP Diss LAP Diss GLU
F 7.55 0.03 6.18 4.97 55.08 299.42 26.50 29.84 11.68 12.59 76.50 80.63 2.32
P 5% ns 5% 5% 1% 1% 1% 1% 1% 1% 1% 1% ns
Particulated Organic Carbon (POC) in July
PHP distribution in summer showed maximum values at 25 m and decreased with depth. The particulate organic carbon (POC) was generally low (40.05- 109.9 µgL-1 in summer), as well as the particulate nitrogen (PN) ranging from 5.95 to 16.12 µg N L-1, reflecting a typical oligotrophic condition. Carbon mobilized by total enzymatic activities Carbon mobilized by dissolved enzymes (LAP+GLU) (LAP+GLU)
Total LAP was always higher than GLU; in fact the LAP/GLU ratio showed Phosphorus released by Alkaline Phosphatase (AP) generally positive values (mean ratios: 8.1 in July and 21.1 in January), suggesting the ability of prokaryotes to preferentially metabolize proteins rather than polysaccharides (when > 1). Total LAP activity rates were inversely related to protein substrates as Chl and POC or PN and positively related to dissolved LAP rates. Concerning the dissolved enzymes, the LAP/GLU ratio was very high in summer (mean ratios: 167.3 in July and 21.7 in January respectively), suggesting the preferential flow of proteins (as aminoacids) through the prokaryotes. 0.56%
July 2012 (18.35°C) 73.3 POC (µgC L-1)
0.47%
7.56%
0.35 LAP+GLU
January 2013 (14.96°C) 0.13
0.026
61.6
PHP
PB
0.11 CO2
1.48%
8.5
Unlike the other microbial parameters, the highest AP values were observed in January with significant (P
