Chemical Analyses
To analyse total suspended matter (TSM),
suspended pigments, particulate carbohydrate,
protein and lipid concentrations, sub-aliquots
(100-1000 ml) of the samples were filtered under
gentle vacuum onto Whatman GF/F glass-fibre
filters (0.8-llm nominal pore size). To determine
TSM, Whatman GF/F filters (0.45 Ilm nominal
pore size) were weighed after desiccation (60 ac.
24 h, Strickland and Parson 1972) using a Mettler
M3 balance (accuracy ± 1 Ilg). Particulate chlorophyll-a (P-Chl-a) analysis was carried out
according to Lorenzen and Jeffrey (1980).
Pigments were extracted with 90% acetone.
Phaeopigments (Phaeo) were determined after
acidification with 0.1 N HCL Particulate organic
carbon (PaC) and nitrogen (PaN) were determined with a Perkin-Elmer CHN Elemental
Analyser (Mod. 2400), using acetanilide at 925 ac
as a standard, the inorganic carbon having been
removed using HCl (Hickel 1984; Iseki et al.
1987). Particulate carbohydrates (P-CHO) were
determined according to Dubois et al. (1956). d
(+) Glucose was used as the standard. Particulate
proteins (P-PRT) were determined according to
Hartree (1972), using bovine serum albumin
(BSA) as the standard. Particulate lipids (P-LIP)
were extracted according to Bligh and Dyer
(1959) and analysis was performed by carbonisation according to Marsh and Weinstein (1966).
Tripalmitine was used as the standard. The biopolymeric fraction of particulate organic carbon
(P-BPC) was defined as the sum of carbohydrate,
protein and lipid carbon (Fabiano and Pusceddu,
1998).
Analyses of sediment chlorophyll-a (S-Chl-a)
and phaeopigments (S-Phaeo) were carried out
according to Lorenzen and Jeffrey (1980).
Pigments were extracted with 90% acetone (24 h
in the dark at 4 QC). After centrifugation, the
supernatant was used to determine the functional Chl-a and acidified with 0.1 N HCl to estimate the amount of phaeopigments (Plante-Cuny
1974). Sedimentary chloroplastic pigment equivalents (S-CPE) were calculated as sum of chlorophyll-a and phaeopigment concentrations.
Microphytobenthic carbon was calculated by
converting S-Chl-a concentrations to carbon
content using a conversion factor of 40 (de Jonge
1980).
After sonication in deionized water, total sediment lipids (S-LIP) were extracted by direct eluPelagic-benthic Coupling in a Semi-enclosed Marine System
437
tion with chloroform and methanol according to
Bligh and Dyer (1959) and Marsh and Weinstein
(1966). Data are reported in tripalmitine equivalents. Sedimentary protein (S-PRT) analyses of
three replicates were conducted following
extraction with NaOH (0.5 M, 4 h) and were
determined according to Hartree (1972) as
modified by Rice (1982), to compensate for phenol interference and expressed as BSA equiva1ents. Sedimentary carbohydrates (CHO) of three
replicate samples were analysed according to
Gerchacov and Hatcher (1972) and expressed as
glucose equivalents. The assay. which reacts with
reducing saccharides and is widely utilised in the
literature, is based on the same principle as the
widely utilised method of Dubois et a1. (1956),
but it is specifically adapted for carbohydrate
determination in sediments.
For each biochemical analysis, blanks were
performed using sediments that had been precombusted at 450 QC for 2 h. Sedimentary lipid,
carbohydrate and protein were converted into
carbon equivalents using 0.75, 0.40 and 0.49 g C
g-l conversion factors. respectively (Fabiano and
Pusceddu 1998). The sedimentary biopolymeric
organic carbon (S-BPC) was defined as the sum
of carbohydrate, protein and lipid carbon
(Fabiano et al. 1995).
Statistical Analyses
Temporal and spatial fluctuations were investigated by means of analysis of variance (ANOVA;
Underwood, 1997) with time (month) and space
(station) as sources of variation. When a significant difference (p < 0.05) for the main effect was
observed, means were analysed by a Tukey's multiple comparison test to determine the differences between sampling stations and months. Data
were transformed, only when necessary, to meet
the assumptions of the parametric statistics.
Results
Physical Measurements, Total Suspended
Matter and Suspended Pigments
Temperature and salinity showed a clear seasonal trend (Fig. 2). The minimum temperature
was observed in January (12.38 ± 0.53 QC), while
the maximum was measured in August (27.65 ±
To analyse total suspended matter (TSM),
suspended pigments, particulate carbohydrate,
protein and lipid concentrations, sub-aliquots
(100-1000 ml) of the samples were filtered under
gentle vacuum onto Whatman GF/F glass-fibre
filters (0.8-llm nominal pore size). To determine
TSM, Whatman GF/F filters (0.45 Ilm nominal
pore size) were weighed after desiccation (60 ac.
24 h, Strickland and Parson 1972) using a Mettler
M3 balance (accuracy ± 1 Ilg). Particulate chlorophyll-a (P-Chl-a) analysis was carried out
according to Lorenzen and Jeffrey (1980).
Pigments were extracted with 90% acetone.
Phaeopigments (Phaeo) were determined after
acidification with 0.1 N HCL Particulate organic
carbon (PaC) and nitrogen (PaN) were determined with a Perkin-Elmer CHN Elemental
Analyser (Mod. 2400), using acetanilide at 925 ac
as a standard, the inorganic carbon having been
removed using HCl (Hickel 1984; Iseki et al.
1987). Particulate carbohydrates (P-CHO) were
determined according to Dubois et al. (1956). d
(+) Glucose was used as the standard. Particulate
proteins (P-PRT) were determined according to
Hartree (1972), using bovine serum albumin
(BSA) as the standard. Particulate lipids (P-LIP)
were extracted according to Bligh and Dyer
(1959) and analysis was performed by carbonisation according to Marsh and Weinstein (1966).
Tripalmitine was used as the standard. The biopolymeric fraction of particulate organic carbon
(P-BPC) was defined as the sum of carbohydrate,
protein and lipid carbon (Fabiano and Pusceddu,
1998).
Analyses of sediment chlorophyll-a (S-Chl-a)
and phaeopigments (S-Phaeo) were carried out
according to Lorenzen and Jeffrey (1980).
Pigments were extracted with 90% acetone (24 h
in the dark at 4 QC). After centrifugation, the
supernatant was used to determine the functional Chl-a and acidified with 0.1 N HCl to estimate the amount of phaeopigments (Plante-Cuny
1974). Sedimentary chloroplastic pigment equivalents (S-CPE) were calculated as sum of chlorophyll-a and phaeopigment concentrations.
Microphytobenthic carbon was calculated by
converting S-Chl-a concentrations to carbon
content using a conversion factor of 40 (de Jonge
1980).
After sonication in deionized water, total sediment lipids (S-LIP) were extracted by direct eluPelagic-benthic Coupling in a Semi-enclosed Marine System
437
tion with chloroform and methanol according to
Bligh and Dyer (1959) and Marsh and Weinstein
(1966). Data are reported in tripalmitine equivalents. Sedimentary protein (S-PRT) analyses of
three replicates were conducted following
extraction with NaOH (0.5 M, 4 h) and were
determined according to Hartree (1972) as
modified by Rice (1982), to compensate for phenol interference and expressed as BSA equiva1ents. Sedimentary carbohydrates (CHO) of three
replicate samples were analysed according to
Gerchacov and Hatcher (1972) and expressed as
glucose equivalents. The assay. which reacts with
reducing saccharides and is widely utilised in the
literature, is based on the same principle as the
widely utilised method of Dubois et a1. (1956),
but it is specifically adapted for carbohydrate
determination in sediments.
For each biochemical analysis, blanks were
performed using sediments that had been precombusted at 450 QC for 2 h. Sedimentary lipid,
carbohydrate and protein were converted into
carbon equivalents using 0.75, 0.40 and 0.49 g C
g-l conversion factors. respectively (Fabiano and
Pusceddu 1998). The sedimentary biopolymeric
organic carbon (S-BPC) was defined as the sum
of carbohydrate, protein and lipid carbon
(Fabiano et al. 1995).
Statistical Analyses
Temporal and spatial fluctuations were investigated by means of analysis of variance (ANOVA;
Underwood, 1997) with time (month) and space
(station) as sources of variation. When a significant difference (p < 0.05) for the main effect was
observed, means were analysed by a Tukey's multiple comparison test to determine the differences between sampling stations and months. Data
were transformed, only when necessary, to meet
the assumptions of the parametric statistics.
Results
Physical Measurements, Total Suspended
Matter and Suspended Pigments
Temperature and salinity showed a clear seasonal trend (Fig. 2). The minimum temperature
was observed in January (12.38 ± 0.53 QC), while
the maximum was measured in August (27.65 ±