PHOTOSYNTHESIS AND REGULATION OF RUBISCO ACTIVITY IN NET PHYTOPLANKTON FROM DELAWARE BAY

Citation
Hl. Macintyre et al., PHOTOSYNTHESIS AND REGULATION OF RUBISCO ACTIVITY IN NET PHYTOPLANKTON FROM DELAWARE BAY, Journal of phycology, 32(5), 1996, pp. 718-731
Citations number
89
Categorie Soggetti
Plant Sciences","Marine & Freshwater Biology
Journal title
ISSN journal
00223646
Volume
32
Issue
5
Year of publication
1996
Pages
718 - 731
Database
ISI
SICI code
0022-3646(1996)32:5<718:PARORA>2.0.ZU;2-K
Abstract
Net phytoplankton (> 20 mu m) comprised 51 +/- 9% of the total chlorop hyll (Chl) in a Skeletonema costatum-dominated spring bloom in Delawar e Bay. The net phytoplankton had low C:N and high protein: carbohydrat e ratios, indicating that their growth was nutrient-replete. Their pho tosynthetic responses were characterized by low specific absorption, l ow light-limited and light-saturated rates of photosynthesis, and high quantum yields, indicative of acclimation to low irradiance and inter nal self-shading. High fucoxanthin: Chl ratios also indicated low ligh t acclimation, but high photoprotective xanthophyll: Chl ratios sugges ted a high capacity for photoprotective energy dissipation. Ribulose-1 ,5-bisphosphate carboxylase/oxygenase (Rubisco) could be activated and deactivated in response to changes in irradiance and was fully activa ted at the surface of the water column and fully deactivated in aphoti c deep water. Maximum Rubisco activity was correlated with Rubisco con tent and bulk protein content of the phytoplankton and with light-satu rated rates of photosynthesis measured in short (< 20-min) incubations . Long (60-min) incubations caused a decrease in the light-saturated r ate of photosynthesis, possibly because of feedback limitation. While feedback limitation is unlikely to occur in the water column, it shoul d be considered when estimating productivity in well-mixed waters from fixed light-depth incubations.