1. Project coordinators: IOC-UNESCO & INGV
Italian Ministry for the Environment and Territory
Italian Ministry
of Foreign Affairs
ADRICOSM
IOC-UNESCO
Rome November 2006
ADRIatic sea integrated COastal areaS and river basin Management system pilot project EXTension National Institute of Oceanography and Applied Geophysics (OGS)
Trieste, Italy
Project coordinators: IOC-UNESCO & INGV

2. 3. Measurements of water particles light absorption.
Subtask 1.5.4: Assessment of primary production in the Gulf of Trieste coastal waters
Activities
Implementation of the primary production data set in observational areas with “in situ” 14C standard method.
2. Estimation of photosynthetic rate vs irradiance curves (PvsE) by means of a light incubator.
3. Measurements of water particles light absorption.
4. Assessment of primary production using optical model and comparison with the “in situ” 14C method.

3. Standard method Optical model
“in situ” 14C PP
(3 hours incubation
around noon)
“in situ”
Photosynthetic rate (PB)
Standard method
Phytoplankton Biomass
P vs E curves
Photosynthetically
available radiation
(PAR)
water particles light
absorption
PBmax , S
Modelled
Photosynthetic rate (PB)
Optical model

4. (period: March - October 2006)
cruises
(period: March - October 2006)
Date
"in situ" PP
"light-incubator" PP
Specific absorption coeff.
Biomass and abundances N°
(d/m)
incubation depth (m)
sampled depth
(m) 1
8-Mar
0, 5, 10, 15 5 - 2
28-Mar 3
5-Apr 4
4-May
7-Jun 6
27-Jun
5 , 14
0, 5, 10, 14 7
6-Jul
10 , 15 8
8-Aug 15 9
5-Sep 10
10-Oct

5. Assessment of primary production at four depths of a coastal station (“in situ” 14C method).
“In situ” 14C incubation was performed in station C1 located about 200 m from the coast with a maximum depth of 18 m.
3 replicates of transparent polycarbonate bottles and one dark bottle were inoculated with 300 ml of a 20 mCi/ml NaH14CO3 solution.
Each bottle was then mounted on a cross shaped support fixed on a rope to maintain the bottles for 3 hours at the fixed depths.

7. Estimation of photosynthetic rate vs irradiance curves (P vs E).
The determination of the photosynthetic rate versus irradiance curves were performed by means of an ICES “light incubator”.
A set of 12 incubation flask with transmission levels ranging from 0 to 100 % are used to simulate 11 different irradiance conditions and a dark flask.
0.059
0.132
0.230
0.476
0.845
1.153
1.310
1.641
1.993
2.357
2.800
E0 (Ein*m-2*h-1)
2.1
4.7
8.2 17
30.2
41.2
46.8
58.6
71.2
84.2
100
Trasm. (%) 1 2 3 4 5 6 7 8 9 10 11
Flask n°
20 fluorescent tube Osram TL-33 (8W)
The incubation time ranged from 45 minutes to 1 hour with a rotation speed of approximately 10 rpm.

8. Inc. max. light int. = 2.8 Ein*m-2*h-1
PBmax – Maximum photosyntethic rate
S – Maximum light utilization coefficient
* Sampled depth
Inc. max. light int. = 2.8 Ein*m-2*h-1

9. Measurement of phytoplankton absorption
The use of the “integrating-sphere” permits measurements of filter-retained particle samples in both the transmission mode and the reflection mode, allowing the correction for the sample backscattering.
Optical characteristics of coastal waters are strongly influenced by particles which does not covary with chlorophyll.
Particulate detritus, including all nonliving cellular material, fecal pellets, heterotrophic bacteria and zooplankton, strongly influences the light-scattering bias in absorption measurement of acquatic particles.

10. Transmittance-Reflectance method for
measuring in vivo light absorption by acquatic particles
Transmission mode
Reflection mode

11. 0 m
10 m
15 m
5 m
a* = āph(l)/[Chl a]
The ratio between the pigmented particulate matter absorption (aph) and phytoplankton biomass is called specific absorption coefficient (a*) and it is used in bio-optical models to assess
how much light is absorbed by phytoplankton according to its species composition and physiological acclimation.

13. Conclusions
- Estimates of photosynthetic rate obtained by means of a light-incubator are substantially consistent with “in situ” data, though the light range of the instrument used must still be increased in order to correctly describe phytoplankton response under high light intensity.
- The use of bio-optical models permit the assessment of photosynthetic rate with higher spatial resolution avoiding long “in situ” incubation.
- The characterization of light absorption by acquatic particles provides useful information about the inherent optical properties of the water column and permit to assess how much light is absorbed by the phytoplankton.

14. Thank you for your attention