ausblenden:
Schlagwörter:
-
Zusammenfassung:
Patterns in lipid, carbohydrate, and protein production and the photosynthetic parameters describing their production were determined for ultra-phytoplankton communities of deep chlorophyll maxima (DCM) from the eastern Mediterranean Sea. There were strong similarities in the photosynthetic characteristics of the DCM of the eastern Mediterranean and DCM of other oligotrophic freshwater and marine systems. Pmax of DCM at different stations varied between 1.1-7.8 109g C (μg Chl-a)⁻¹ h⁻¹ (mean = 2.47; S.D. 0±2.05). Light utilization efficiency (a) was high and varied between 0.015-0.116 109g C (μg Chl-a)⁻¹ h⁻¹ (μmol quanta m⁻²s⁻¹)⁻¹, (mean 0.036; S.D. = ± 0.03). Estimates of lk from this study fall within the range of 48-139 μmol m⁻²s⁻¹. These values of Ik are consistent with published estimates (50-150 μmol m⁻²s⁻¹) from different freshwater and marine environments. In this study lk estimates indicate that DCM ultraphytoplankton communities are adapted to low light. Artificially irradiated DCM communities were susceptible to photoinhibition, however, the photoinhibition parameters exhibited great variability (mean = 1.13 × 10⁻³; range 2.89 × 10⁻⁴ to 3.0 × 10⁻³ μg C (μg Chl-a)⁻¹h⁻¹ (μmol m⁻²s⁻¹)⁻¹. Most of the ¹⁴C was incorporated into polysaccharide (range = 38-72%; mean = 55%; C.V. = 8.7%), with lowest amounts incorporated into protein (range = 12-23%; mean = 17%; C.V. = 11.3%). Percentage of carbon fixation into lipid (LIP-FCF) varied between 16-44% (mean = 23.7%; CV = 18.1%). In contrast to previous marine literature which has shown an increase in algal lipids when either P or N is exhausted, or results indicate no such relationship. This discrepancy may be due to different algae, which may exhibit different physiological responses. Further, this study shows that nutrient deficiency does not affect the LIP-FCF in natural populations of the DCM from the eastern Mediterranean Sea.
