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Significance of photosynthetic endosymbionts to the carbon budget of the scyphomedusa Linuche unguiculata
Author(s) -
Kremer Patricia,
Costello John,
Kremer James,
Canino Michael
Publication year - 1990
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1990.35.3.0609
Subject(s) - diel vertical migration , zooxanthellae , photosynthesis , respiration , light intensity , biology , botany , respiration rate , algae , zoology , compensation point , oxygen , carbon dioxide , chemistry , ecology , symbiosis , genetics , physics , organic chemistry , bacteria , optics , transpiration
Symbiotic dinoflagellates (zooxanthellae) associated with the medusa of Linuche unguiculata constituted 22–26% of the total C and N biomass. The maximal net production for intact medusae ( P m ) averaged 4.5 mg O 2 (mg Chl a ) −1 h −1 , equivalent to an assimilation number of 2.0 mg C (mg Chl a ) −1 h −1 . At the midday maximum, gross oxygen production averaged four times the respiration rate. The saturating light intensity was 200–300 µ Einst m −2 s −1 (Einstein = mol quanta) and the compensation light intensity (dO 2 = 0) was ∼20 µ Einst mn −2 s −1 . On a diel basis P grow : R averaged 1.7 for intact medusae at ambient near‐surface light. Diel periodicity with a midday maximum was measured for the production potential under artificial, saturating light. Both intact medusae and freshly isolated zooxanthellae demonstrated similar diel production patterns. Respiration did not show the same strong diel pattern as net production, but respiration declined steadily when medusae were held unfed in the dark. Respiration was independent of the ambient oxygen concentration over a range from 4 to 16 mg O 2 liter −1 . Diel periodicity was measured in egg release and division rates of zooxanthellae. Estimates of both algal and host growth ranged from 0.01 to 0.04 d −1 . Calculations indicated that only 21% of the C fixed in photosynthesis was used in algal respiration and growth. If the remaining photosynthate were translocated, it could provide all the C required for host respiration and somatic growth. Egg production represented another large C flux in adult females, with a daily release equivalent to 4–8% of host body C for medusae of 0.2–1.2 ml in displacement volume.