The uptake and/or release rates of carbon (C), nitrogen (N), phosphorus (P) and sulphur (S) during Ulva rigida growth and/or decomposition were determined in two different nutrient-enriched areas of the Venice lagoon. The field investigation included 20 experiments subdivided in four different seasonal periods. Experiments were carried out by suspending 150 g fw of Ulva biomass in 12 net wire cages, 6 fixed at the surface and 6 at the bottom of each area studied. Weight determinations and collection of samples from the cages for the nutrient tissue analysis were carried out at 4-10 day intervals, depending on the season. Temperature, light and the nutrient concentrations in the whole water column as well as in the surface sediment porewater were also determined. The daily cage and in situ biomass variations (DBVs) were up to 23% and 137%, respectively. The rates of biomass production were 2-3 times higher in the more nutrient-enriched area and within the cages suspended close to the water surface. The rates of the daily nutrient uptake by Ulva tissue were up to 43% for P, 19% for N, 6.8% for C and 9.3% for S. Significant (P < 0.01) correlation coefficients between the environmental and tissue nutrient concentrations and the biomass increase and/or decrease were found. However, besides interesting data suggesting a phosphorus (from tissue N:P atomic ratios up to 61:1 and P water concentrations <1 mu mol L(-1)) or a nitrogen (from critical biomass N concentrations <20 mg g dw(-1)) growth limitation, no effective limitations in the biomass production were monitored. These results confirm previous results on the key role of the water renewal by tides and of the nutrient fluxes from the water-sediment interface as the main factors controlling the availability of nutrient elements for the algal growth in the Venice lagoon.

Temporal and spatial responses of growth of Ulva rigida C.Ag. to environmental and tissue concentrations of nutrients in the lagoon of Venice

SFRISO, Adriano
1995-01-01

Abstract

The uptake and/or release rates of carbon (C), nitrogen (N), phosphorus (P) and sulphur (S) during Ulva rigida growth and/or decomposition were determined in two different nutrient-enriched areas of the Venice lagoon. The field investigation included 20 experiments subdivided in four different seasonal periods. Experiments were carried out by suspending 150 g fw of Ulva biomass in 12 net wire cages, 6 fixed at the surface and 6 at the bottom of each area studied. Weight determinations and collection of samples from the cages for the nutrient tissue analysis were carried out at 4-10 day intervals, depending on the season. Temperature, light and the nutrient concentrations in the whole water column as well as in the surface sediment porewater were also determined. The daily cage and in situ biomass variations (DBVs) were up to 23% and 137%, respectively. The rates of biomass production were 2-3 times higher in the more nutrient-enriched area and within the cages suspended close to the water surface. The rates of the daily nutrient uptake by Ulva tissue were up to 43% for P, 19% for N, 6.8% for C and 9.3% for S. Significant (P < 0.01) correlation coefficients between the environmental and tissue nutrient concentrations and the biomass increase and/or decrease were found. However, besides interesting data suggesting a phosphorus (from tissue N:P atomic ratios up to 61:1 and P water concentrations <1 mu mol L(-1)) or a nitrogen (from critical biomass N concentrations <20 mg g dw(-1)) growth limitation, no effective limitations in the biomass production were monitored. These results confirm previous results on the key role of the water renewal by tides and of the nutrient fluxes from the water-sediment interface as the main factors controlling the availability of nutrient elements for the algal growth in the Venice lagoon.
1995
38
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10278/12988
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