required in order that these aggregates reach as
large sizes as those with which we have been
faced in recent years (Riebesell1992).
Acknowledgements. This study is part of the PRISMA Project,
founded by the Italian Ministry for University and Scientific
and Technological Research. Thanks are due to the crew of the
RN Urania and to Mr. F. Bacciu, of this Institute, for the collection of samples and analysis of DOC.
References
Bell RT (1993) Estimating production of heterotrophic bacterioplankton via incorporation of tritiated thymidine. In: Kemp
PF, et al (eds) Handbook of methods in aquatic microbial
ecology. Lewis Publishers, Boca Raton, pp 495-503
Benner R, Hedges JI (1993) A test of accuracy offresh water DOC
measurements by high-temperature catalytic oxidation and
UV-promoted persulfate oxidation. Mar Chem 41: 161-165
Benner R, Pakulski JD, McCarthy M, Hedges JI, Hatcher G (1992)
Bulk chemical characteristics of dissolved organic matter in
the oceans. Sciences 255: 1561-1564
Carlson CA, Ducklow HW, Michaels AF (1994) Annual flux of dissolved organic carbon from the euphotic zone in the northwestern Sargasso Sea. Nature 371: 405-408
Chin WC, Orellana MY, Verdugo P (1998) Spontaneous assembly
of marine dissolved organic matter into polymer gels.
Nature 391: 568-572
Chisholm S (1992) What limits phytoplankton growth? Oceanus
35(3): 36-46
Cupin-Montegut G, Avril B (1993) Vertical distribution and temporal variation of dissolved organic carbon in the NorthWestern Mediterranean Sea. Deep-Sea Res 40(10): 1963-1912
Degobbis D, Gilmartin M (1990) Nitrogen, phosphorus and biogenic silicon budgets for the northern Adriatic sea. Oceanol
Acta 13: 31-45
Degobbis D, Fonda-Umani S, Franco P, Malej A, Precali R,
Smodlaka N (1995) Changes in the northern Adriatic
ecosystem and the hypertrophic appearance of gelatinous
aggregates. Sci Total Environ 165: 43-58
Degobbis D, Malej A, Fonda Umani S (2000) The mucilage phenomenon in the northern Adriatic - a critical review of the
present scientific hypothesis. Proc Int Workshop State Art
New Sci Hypotheses Phenomenon Mucilages Adriatic Sea,
24-25 March 1997, Trieste. Ann 1st Super Banita (in press)
Druffel ER. Williams PM, Bauer JE, Ertel R (1992) Cycling of dissolved and particulate organic matter in the open ocean. J
Geophys Res 97: 639-659
Ducklow HW, Carlson CA (1992) Oceanic bacterial production.
In: Marshall KC (ed) Advances in microbial ecology. Plenum
Press, New York, pp 113-181
Ducklow HW, Shiah FK (1993) Bacterial production in estuaries.
In: Ford TE (ed) Aquatic microbiology: an ecological
approach. Blackwell, Oxford, pp 261-287
Dugdale RC, Wilkerson FP (1998) Silicate regulation of new production in the equatorial Pacific upwelling. Nature, 391: 270273
Faganeli J,Herndl G (1991) Dissolved organic matter in the waters
of the Gulf of Trieste (Northern Adriatic). Thalassia Jugosl
23:51-63
Fonda Umani S, Cauwet G, Cok S, Martecchini E, Predonzani S
(1997) Chemical and biological seasonal patterns of the Gulf
of Trieste: the example of early and late summer. In: Cauwet
DOC Seasonality in N. Adriatic and Aggregate Formation
465
G (ed) PALOMA - production and accumulation of labile
organic matter in adriatic (contract n. EV5V-CT94-0420).
EEC Environ Climate Progr Final Rep 2
Guo L, Coleman CH, Santschi PH (1994) The distribution of colloidal and dissolved organic carbon in the Gulf of Mexico.
Mar Chem 45: 105-119
Guo L, Santschi PH, Warnken KW (1995) Dynamics of dissolved
organic carbon (DOC) in oceanic environments. Limool
Oceanogr 40(8): 1392-1403
Hobbie JE. Daley RI, Jasper S (1977) Use of NUclepore filters for
counting bacteria by fluorescence microscopy. Appl Environ
Microbio133(5): 1225-1228
Karner M, Rassoulzadegan F (1995) Extracellular enzyme activity: indications for high short-term variability in a coastal
marine ecosystem. Microb Eco130: 143-156
Ke:pkay PE(1994) Particle aggregation and the biological reactivity of colloids. Mar Ecol Prog Ser 109: 293-304
Kirchman DL (1993) Leucine incorporation as a measure of biomass production byheterotrophic bacteria. In: Kemp PF, et al
(eds) Handbook of methods in aquatic microbial ecology.
Lewis Publishers, Boca Raton, pp 509-512
Landry MR, Barber RT, Bidigare RB, Chai F, Coale K, Dam HG et al
(1997) Iron and grazing constraints on primary production
in the central equatorial Pacific. Limool Ocanogr 42(3): 405418
Lee S, Fuhrman JA (1987) Relationships between biovolume and
biomass of naturally derived marine bacterioplankton. Appl
Environ Microbio153(6): 1298-1303
Lipizer M, Cozzi S, Catalano G (1997) Accumulation of DON and
DOP and "new" production in the northern Adriatic Sea. In:
Dehairs F,Elskens M, Goeyens L (eds) Integrated marine system analysis. In: Proc 2nd Network Meet Brussels. 29-31 May
1997, pp 85-97
Martin JH (1992) Iron as a limiting factor in oceanic productivity. In: Falkowski P, Woodhead AD (eds) Primary productivity and biogeochemical cycles in the sea. Plenum, New York,
pp 123-127
Martin JM, Dai MH (1995) Significance of colloids in the biogeochemical cycling of organic carbon and trace metals in the
Venice Lagoon (Italy). Limnol Oceanogr 40(1}: 119-131
Muller-Niklas G, Schuster S, KaltenbOck E, Herndl G (1994)
Organic content and bacterial metabolism in amorphous
aggregations of the northern Adriatic sea. Limnol Oceanogr
30(1): 58-68
Pettine M, Pagnotta R, Liberatod A (1995) Composition of
mucilaginous macroaggregates and hypotheses for their formation. Ann Chim 85: 431-441
Pettine M. Patrolecco L,Manganelli M, Capri S. Farrace MG (1999)
Seasonal variations of dissolved organic matter in the northern Adriatic Sea. Mar Chem 64: 153-169
Puddu A, La FerIa R, Allegra A. Bacci C, Lopez M, Oliva F, Pierotti
C (1998) Seasonal and spatial distribution of bacterial production and biomass along a salinity gradient (Northern
Adriatic Sea). Hydrobio1363: 271-282
Riebesell U (1992) The formation of large marine snow and its
sustained residence in surface waters. Limnol Oceanogr
37(1); 63-76
Riemann B, S0ndergaard M (1984) Measurements of diel rates of
bacterial secondary production in aquatic environments.
Appl Environ Microbiol47{ 4}: 632-638
Sherr EB, Sherr BF (1996) Temporal offset in oceanic production
and respiration processes implied by seasonal changes in
atmospheric oxygen: the role of heterotrophic microbes.
Aquat Microb Ecol11:91-1oo
Smith DC,Azam F (1992) A simple. economical method for mea-
large sizes as those with which we have been
faced in recent years (Riebesell1992).
Acknowledgements. This study is part of the PRISMA Project,
founded by the Italian Ministry for University and Scientific
and Technological Research. Thanks are due to the crew of the
RN Urania and to Mr. F. Bacciu, of this Institute, for the collection of samples and analysis of DOC.
References
Bell RT (1993) Estimating production of heterotrophic bacterioplankton via incorporation of tritiated thymidine. In: Kemp
PF, et al (eds) Handbook of methods in aquatic microbial
ecology. Lewis Publishers, Boca Raton, pp 495-503
Benner R, Hedges JI (1993) A test of accuracy offresh water DOC
measurements by high-temperature catalytic oxidation and
UV-promoted persulfate oxidation. Mar Chem 41: 161-165
Benner R, Pakulski JD, McCarthy M, Hedges JI, Hatcher G (1992)
Bulk chemical characteristics of dissolved organic matter in
the oceans. Sciences 255: 1561-1564
Carlson CA, Ducklow HW, Michaels AF (1994) Annual flux of dissolved organic carbon from the euphotic zone in the northwestern Sargasso Sea. Nature 371: 405-408
Chin WC, Orellana MY, Verdugo P (1998) Spontaneous assembly
of marine dissolved organic matter into polymer gels.
Nature 391: 568-572
Chisholm S (1992) What limits phytoplankton growth? Oceanus
35(3): 36-46
Cupin-Montegut G, Avril B (1993) Vertical distribution and temporal variation of dissolved organic carbon in the NorthWestern Mediterranean Sea. Deep-Sea Res 40(10): 1963-1912
Degobbis D, Gilmartin M (1990) Nitrogen, phosphorus and biogenic silicon budgets for the northern Adriatic sea. Oceanol
Acta 13: 31-45
Degobbis D, Fonda-Umani S, Franco P, Malej A, Precali R,
Smodlaka N (1995) Changes in the northern Adriatic
ecosystem and the hypertrophic appearance of gelatinous
aggregates. Sci Total Environ 165: 43-58
Degobbis D, Malej A, Fonda Umani S (2000) The mucilage phenomenon in the northern Adriatic - a critical review of the
present scientific hypothesis. Proc Int Workshop State Art
New Sci Hypotheses Phenomenon Mucilages Adriatic Sea,
24-25 March 1997, Trieste. Ann 1st Super Banita (in press)
Druffel ER. Williams PM, Bauer JE, Ertel R (1992) Cycling of dissolved and particulate organic matter in the open ocean. J
Geophys Res 97: 639-659
Ducklow HW, Carlson CA (1992) Oceanic bacterial production.
In: Marshall KC (ed) Advances in microbial ecology. Plenum
Press, New York, pp 113-181
Ducklow HW, Shiah FK (1993) Bacterial production in estuaries.
In: Ford TE (ed) Aquatic microbiology: an ecological
approach. Blackwell, Oxford, pp 261-287
Dugdale RC, Wilkerson FP (1998) Silicate regulation of new production in the equatorial Pacific upwelling. Nature, 391: 270273
Faganeli J,Herndl G (1991) Dissolved organic matter in the waters
of the Gulf of Trieste (Northern Adriatic). Thalassia Jugosl
23:51-63
Fonda Umani S, Cauwet G, Cok S, Martecchini E, Predonzani S
(1997) Chemical and biological seasonal patterns of the Gulf
of Trieste: the example of early and late summer. In: Cauwet
DOC Seasonality in N. Adriatic and Aggregate Formation
465
G (ed) PALOMA - production and accumulation of labile
organic matter in adriatic (contract n. EV5V-CT94-0420).
EEC Environ Climate Progr Final Rep 2
Guo L, Coleman CH, Santschi PH (1994) The distribution of colloidal and dissolved organic carbon in the Gulf of Mexico.
Mar Chem 45: 105-119
Guo L, Santschi PH, Warnken KW (1995) Dynamics of dissolved
organic carbon (DOC) in oceanic environments. Limool
Oceanogr 40(8): 1392-1403
Hobbie JE. Daley RI, Jasper S (1977) Use of NUclepore filters for
counting bacteria by fluorescence microscopy. Appl Environ
Microbio133(5): 1225-1228
Karner M, Rassoulzadegan F (1995) Extracellular enzyme activity: indications for high short-term variability in a coastal
marine ecosystem. Microb Eco130: 143-156
Ke:pkay PE(1994) Particle aggregation and the biological reactivity of colloids. Mar Ecol Prog Ser 109: 293-304
Kirchman DL (1993) Leucine incorporation as a measure of biomass production byheterotrophic bacteria. In: Kemp PF, et al
(eds) Handbook of methods in aquatic microbial ecology.
Lewis Publishers, Boca Raton, pp 509-512
Landry MR, Barber RT, Bidigare RB, Chai F, Coale K, Dam HG et al
(1997) Iron and grazing constraints on primary production
in the central equatorial Pacific. Limool Ocanogr 42(3): 405418
Lee S, Fuhrman JA (1987) Relationships between biovolume and
biomass of naturally derived marine bacterioplankton. Appl
Environ Microbio153(6): 1298-1303
Lipizer M, Cozzi S, Catalano G (1997) Accumulation of DON and
DOP and "new" production in the northern Adriatic Sea. In:
Dehairs F,Elskens M, Goeyens L (eds) Integrated marine system analysis. In: Proc 2nd Network Meet Brussels. 29-31 May
1997, pp 85-97
Martin JH (1992) Iron as a limiting factor in oceanic productivity. In: Falkowski P, Woodhead AD (eds) Primary productivity and biogeochemical cycles in the sea. Plenum, New York,
pp 123-127
Martin JM, Dai MH (1995) Significance of colloids in the biogeochemical cycling of organic carbon and trace metals in the
Venice Lagoon (Italy). Limnol Oceanogr 40(1}: 119-131
Muller-Niklas G, Schuster S, KaltenbOck E, Herndl G (1994)
Organic content and bacterial metabolism in amorphous
aggregations of the northern Adriatic sea. Limnol Oceanogr
30(1): 58-68
Pettine M, Pagnotta R, Liberatod A (1995) Composition of
mucilaginous macroaggregates and hypotheses for their formation. Ann Chim 85: 431-441
Pettine M. Patrolecco L,Manganelli M, Capri S. Farrace MG (1999)
Seasonal variations of dissolved organic matter in the northern Adriatic Sea. Mar Chem 64: 153-169
Puddu A, La FerIa R, Allegra A. Bacci C, Lopez M, Oliva F, Pierotti
C (1998) Seasonal and spatial distribution of bacterial production and biomass along a salinity gradient (Northern
Adriatic Sea). Hydrobio1363: 271-282
Riebesell U (1992) The formation of large marine snow and its
sustained residence in surface waters. Limnol Oceanogr
37(1); 63-76
Riemann B, S0ndergaard M (1984) Measurements of diel rates of
bacterial secondary production in aquatic environments.
Appl Environ Microbiol47{ 4}: 632-638
Sherr EB, Sherr BF (1996) Temporal offset in oceanic production
and respiration processes implied by seasonal changes in
atmospheric oxygen: the role of heterotrophic microbes.
Aquat Microb Ecol11:91-1oo
Smith DC,Azam F (1992) A simple. economical method for mea-