TY - JOUR

T1 - The responses of photosynthesis and oxygen consumption to short-term changes in temperature and irradiance in a cyanobacterial mat (Ebro Delta, Spain)

AU - Epping, E.H.G.

AU - Kühl, Michael

PY - 2000

Y1 - 2000

N2 - We have evaluated the effects of short-term changesin incident irradiance and temperature on oxygenicphotosynthesis and oxygen consumption in a hypersalinecyanobacterial mat from the Ebro Delta, Spain,in which Microcoleus chthonoplastes was the dominantphototrophic organism. The mat was incubatedin the laboratory at 15, 20, 25 and 308C at incidentirradiances ranging from 0 to 1000 mmol photonsm22 s21. Oxygen microsensors were used to measuresteady-state oxygen profiles and the rates of grossphotosynthesis, which allowed the calculation of arealgross photosynthesis, areal net oxygen production,and oxygen consumption in the aphotic layer of themat. The lowest surface irradiance that resulted indetectable rates of gross photosynthesis increasedwith increasing temperature from 50 mmol photonsm22 s21 at 158C to 500 mmol photons m22 s21 at 308C.These threshold irradiances were also apparent fromthe areal rates of net oxygen production and point tothe shift of M. chthonoplastes from anoxygenic tooxygenic photosynthesis and stimulation of sulphideproduction and oxidation rates at elevated temperatures.The rate of net oxygen production perunit area of mat at maximum irradiance, J0, did notchange with temperature, whereas, JZphot, the flux ofoxygen across the lower boundary of the euphoticzone increased linearly with temperature. The rate ofoxygen consumption per volume of aphotic matincreased with temperature. This increase occurred indarkness, but was strongly enhanced at high irradiances,probably as a consequence of increased ratesof photosynthate exudation, stimulating respiratoryprocesses in the mat. The compensation irradiance(Ec) marking the change of the mat from a heterotrophicto an autotrophic community, increasedexponentially

AB - We have evaluated the effects of short-term changesin incident irradiance and temperature on oxygenicphotosynthesis and oxygen consumption in a hypersalinecyanobacterial mat from the Ebro Delta, Spain,in which Microcoleus chthonoplastes was the dominantphototrophic organism. The mat was incubatedin the laboratory at 15, 20, 25 and 308C at incidentirradiances ranging from 0 to 1000 mmol photonsm22 s21. Oxygen microsensors were used to measuresteady-state oxygen profiles and the rates of grossphotosynthesis, which allowed the calculation of arealgross photosynthesis, areal net oxygen production,and oxygen consumption in the aphotic layer of themat. The lowest surface irradiance that resulted indetectable rates of gross photosynthesis increasedwith increasing temperature from 50 mmol photonsm22 s21 at 158C to 500 mmol photons m22 s21 at 308C.These threshold irradiances were also apparent fromthe areal rates of net oxygen production and point tothe shift of M. chthonoplastes from anoxygenic tooxygenic photosynthesis and stimulation of sulphideproduction and oxidation rates at elevated temperatures.The rate of net oxygen production perunit area of mat at maximum irradiance, J0, did notchange with temperature, whereas, JZphot, the flux ofoxygen across the lower boundary of the euphoticzone increased linearly with temperature. The rate ofoxygen consumption per volume of aphotic matincreased with temperature. This increase occurred indarkness, but was strongly enhanced at high irradiances,probably as a consequence of increased ratesof photosynthate exudation, stimulating respiratoryprocesses in the mat. The compensation irradiance(Ec) marking the change of the mat from a heterotrophicto an autotrophic community, increasedexponentially

M3 - Journal article

VL - 2

SP - 465

EP - 474

JO - Environmental Microbiology

JF - Environmental Microbiology

SN - 1462-2912

IS - 4

ER -