105
Obviously the above topics do not exhaus·t the roster of important unresolved
questions concerning marine ecosystems but they illustrate the point that any comprehensive paradigm will need to encompass many new observations. In respect to oligotrophic seas, a brisk controversy still rages which can be summarized thus: 1) Are
the primary producers in the oligotrophic seas growing at 1-2 doublings day-lor
at 0.2 doublings day-1? 2) Is there greater biomass in the higher trophic levels
than can be accounted for by primary productivity as measured by conventional means
in these regions?
THE EASTERN MEDITERRANEAN AS A MODEL OLIGOTROPHIC SEA.
In 1981 we began a baseline study on the biological productivity of the Eastern
Mediterranean Basin. Our initial observations prompt us to suggest that this may
be a very convenient area in which to study the structure of an extremely oligotrophic
ecosystem. Here we present some data on optical characteristics, chlorophyll distribution and primary productivities to substantiate this claim.
Hydrostations and Methods
The data were collected during five cruises (AID-1, 23-31 July 1981; AID-2, 10-14
December 1981; AID-3, 9-12 April 1982; AID-4, 18-22 July 1982; AID-5, 13-15 February
1983), covering the area shown in Fig. 1. Surface chlorophyll was monitored between
stations en route by in vivo fluorescence (Lorenzen 1966). All water samples from
hydrocasts were prefiltered through a 130 pm mesh Nitex net. For size distribution
studies, samples were subsequently filtered through 10 pm Nitex nets or 3 pm Nuclepore
filters. Chlorophyll and phaeophytin concentrations were measured in discrete samples
fluorometrically after concentration on 0.45 pm Millipore filters and extraction in
90% acetone (Holm-Hansen et ~. 1965). Photosynthetic carbon fixation was measured
with 14C bicarbonate using an on-deck simulator cooled with surface water with incubations of 4 to 6.5 hours. Photosynthetically available surface and downwelling
irradiance were determined with a LiCor Quantum meter.
Transparency and downwelling attenuation coefficients
In Table 1 we list Secchi depths, diffuse downwelling attenuation coefficients (K)
and chlorophyll concentrations integrated to approximately 37% of surface irradiance.
(This corresponds to one attenuation unit and is approximately the depth to which
chlorophyll concentrations are determined by remote sensors such as the Coastal
Color Zone Scanner mounted on the Nimbus 7 satellite).
Secchi depths ranged from maxima in the offshore waters of 42 to 46 m (in July
1981 and 1982 respectively) to a minimum of 6 mfor very close inshore waters (July
Obviously the above topics do not exhaus·t the roster of important unresolved
questions concerning marine ecosystems but they illustrate the point that any comprehensive paradigm will need to encompass many new observations. In respect to oligotrophic seas, a brisk controversy still rages which can be summarized thus: 1) Are
the primary producers in the oligotrophic seas growing at 1-2 doublings day-lor
at 0.2 doublings day-1? 2) Is there greater biomass in the higher trophic levels
than can be accounted for by primary productivity as measured by conventional means
in these regions?
THE EASTERN MEDITERRANEAN AS A MODEL OLIGOTROPHIC SEA.
In 1981 we began a baseline study on the biological productivity of the Eastern
Mediterranean Basin. Our initial observations prompt us to suggest that this may
be a very convenient area in which to study the structure of an extremely oligotrophic
ecosystem. Here we present some data on optical characteristics, chlorophyll distribution and primary productivities to substantiate this claim.
Hydrostations and Methods
The data were collected during five cruises (AID-1, 23-31 July 1981; AID-2, 10-14
December 1981; AID-3, 9-12 April 1982; AID-4, 18-22 July 1982; AID-5, 13-15 February
1983), covering the area shown in Fig. 1. Surface chlorophyll was monitored between
stations en route by in vivo fluorescence (Lorenzen 1966). All water samples from
hydrocasts were prefiltered through a 130 pm mesh Nitex net. For size distribution
studies, samples were subsequently filtered through 10 pm Nitex nets or 3 pm Nuclepore
filters. Chlorophyll and phaeophytin concentrations were measured in discrete samples
fluorometrically after concentration on 0.45 pm Millipore filters and extraction in
90% acetone (Holm-Hansen et ~. 1965). Photosynthetic carbon fixation was measured
with 14C bicarbonate using an on-deck simulator cooled with surface water with incubations of 4 to 6.5 hours. Photosynthetically available surface and downwelling
irradiance were determined with a LiCor Quantum meter.
Transparency and downwelling attenuation coefficients
In Table 1 we list Secchi depths, diffuse downwelling attenuation coefficients (K)
and chlorophyll concentrations integrated to approximately 37% of surface irradiance.
(This corresponds to one attenuation unit and is approximately the depth to which
chlorophyll concentrations are determined by remote sensors such as the Coastal
Color Zone Scanner mounted on the Nimbus 7 satellite).
Secchi depths ranged from maxima in the offshore waters of 42 to 46 m (in July
1981 and 1982 respectively) to a minimum of 6 mfor very close inshore waters (July