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EFFECTS OF TEMPERATURE AND ILLUMINANCE ON CELL DIVISION RATES OF THREE SPECIES OF TROPICAL OCEANIC PHYTOPLANKTON(1)
1Institute of Marine Resources, Scripps Institution of Oceanography, University of California, San Diego, California.
Journal of Phycology
|April 8, 2016
Summary
This study investigated the growth rates of tropical oceanic phytoplankton, specifically Gymnoclinium, Chaetoceros, and Nannochloris species, under varying temperature and illuminance conditions. Results provide key insights into the environmental tolerances of these important marine algae.
Area of Science:
- Marine Biology
- Oceanography
- Phytoplankton Ecology
Background:
- Phytoplankton are crucial primary producers in marine ecosystems.
- Understanding their growth dynamics is essential for marine food web and biogeochemical cycle studies.
- Tropical oceanic environments harbor diverse phytoplankton communities with unique physiological adaptations.
Purpose of the Study:
- To determine the effects of temperature and illuminance on the exponential cell division rates of three tropical oceanic phytoplankton species.
- To establish optimal growth conditions and critical light levels (compensation and saturation illuminance) for Gymnoclinium, Chaetoceros, and Nannochloris.
- To investigate potential heterotrophic growth in Nannochloris.
Main Methods:
- Isolation and maintenance of unialgal cultures of Gymnoclinium sp., Chaetoceros sp., and Nannochloris sp. from the eastern Pacific Ocean.
- Experimental manipulation of temperature and illuminance to measure exponential cell division rates.
- Determination of compensation and saturation illuminance levels for each species.
Main Results:
- Gymnoclinium sp. exhibited maximum growth rates of 1.25-1.7 divisions/24 hr, with optimal temperatures between 23-29°C and light saturation above 750 ft-c.
- Chaetoceros sp. showed a higher maximum growth rate of 6.0 divisions/24 hr, thriving between 23-37°C, with light saturation above 600 ft-c.
- Nannochloris sp. achieved growth rates of 4.5 divisions/24 hr, with optimal temperatures of 27-37°C and light saturation above 800 ft-c; it also demonstrated heterotrophic growth.
Conclusions:
- The studied phytoplankton species possess distinct temperature and illuminance requirements for optimal growth.
- Nannochloris sp. displays metabolic flexibility, capable of both photosynthesis and heterotrophic nutrition.
- These findings contribute to understanding phytoplankton ecophysiology in tropical oceanic settings.
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