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  • 1
    Electronic Resource
    Electronic Resource
    Ammonium enhancement of dark carbon fixation and nitrogen limitation in zooxanthellae symbiotic with the reef coralsMadracis mirabilis andMontastrea annularis (1994)
    Springer
    Marine biology 118 (1994), S. 157-165 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nutrient status (limitation vs sufficiency) of dinoflagellates (zooxanthellae) symbiotic with reef corals in Bermuda was assessed in 1989 and 1990 by measuring the enhancement of dark carbon fixation with 20 μM ammonium by isolated symbionts. A colony ofMadracis mirabilis was kept in the laboratory and fed daily or starved for one month. Symbionts from fed portions of the colony had ammonium-enhancement ratios (NH 4dark + ; SWdark;SW=seawater without added ammonium) similar to those of the original field population (1.2 to 1.3). Ammonium-enhancement ratios increased with starvation of the host (x≧1.7) as did values forV D′:V L [(ammonium dark rate-seawater dark rate): light rate in seawater]. Both parameters indicated decreasing nitrogen sufficiency of the algae when the host was not fed, but starvation appeared to affect these algae less than symbionts of sea anemones. Field samples of zooxanthellae fromM. mirabilis (Three Hill Shoals and Bailey's Bay Flats) yielded results similar to those for fed corals, but those taken from Bailey's Bay Flats in May 1990 yielded exceptionally high values for enhancement (〉3) andV D′:V L indicating pronounced nitrogen limitation at the time of sampling. We sampled zooxanthellae from populations ofMontastrea annularis at 8 m (Three Hill Shoals) and 24 m (Soldier's Point) depths. Enhancement andV D′:V L values for zooxanthellae from the 8 m corals were density-dependent: symbionts from corals with “normal” symbiont densities displayed the most nitrogen limitation (enhancement values=1.4 to 2.0), while those from bleached corals with lower density exhibited enhancement andV D′:V L values typical of nitrogen-sufficient algae. Symbionts isolated from the 25 m corals yielded the highest values, and appeared to exhibit the least nitrogen-sufficiency for this species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00699230
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of host feeding and dissolved ammonium on cell division and nitrogen status of zooxanthellae in the hydroid Myrionema amboinense (1994)
    Springer
    Marine biology 121 (1994), S. 343-348 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There is a relationship between host feeding, nitrogen status and mitotic activity of zooxanthellae symbiotic with the marine hydroid Myrionema amboinense. Decreases in the mitotic index of zooxanthellae in starved M. amboinense, and in internal pool sizes of glutamine and glutamate, amino acids involved in ammonium assimilation via the glutamine synthetase-glutamate synthase (GS/GOGAT) pathway, were partially restored by addition of ammonium chloride to seawater in which hydroids were incubated. Levels of glutamine were more sensitive to host starvation than levels of glutamate, resulting in a decrease in the glutamine: glutamate molar ratio to that found in zooxanthellae cultured on nitrate. Hydroids starved for 5 d and then incubated in different concentrations of ammonium chloride showed a positive correlation between ammonium concentration and mitotic index of their symbiotic zooxanthellae. Host starvation caused a decrease in perturbation of levels of glutamine and glutamate during ammonium assimilation, as well as decreases in rates of assimilation of [14C]-leucine into TCA-insoluble protein, and in photosynthetic incorporation of [14C]-bicarbonate. These observations suggest that host starvation reduces nitrogen supply to the zooxanthellae, causing nitrogen stress to the symbionts and reduction in metabolic processes associated with nitrogen assimilation and photosynthesis as well as with cell division.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346743
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of crude oil and chemical dispersant on photosynthesis in the brain coral Diploria strigosa (1983)
    Springer
    Marine biology 78 (1983), S. 21-27 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An eight-hour exposure of Diploria strigosa (Dana) to a mixture of Arabian Light crude oil (19 ppm) and the chemical dispersant “Corexit 9527” (1 ppm) in a flowing seawater system reduced photosynthesis by symbiotic zooxanthellae by 85%, while either oil or dispersant alone had no effect. The greatest effect of crude oil plus dispersant occurred in the incorporation of photosynthetic products into lipids. Synthesis of was esters and triglycerides, the major storage lipids, was particularly affected. Total carbon fixation was restored within 3–5 h after treatment, and lipid synthesis was restored within 5–24 h after exposure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392967
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  • 4
    Electronic Resource
    Electronic Resource
    Host feeding and nutrient sufficiency for zooxanthellae in the sea anemone Aiptasia pallida (1988)
    Springer
    Marine biology 98 (1988), S. 253-262 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nutrient sufficiency of zooxanthellae in the sea anemone Aiptasia pallida cultured in low nutrient seawater depends on the availability of particulate food to the host. Zooxanthellae in anemones unfed for 20 to 30 d exhibited the following characteristics of nutrient deficiency: cell division rates decreased; chlorophyll a content gradually decreased from 2 to 〈1 pg cell−1; and C:N ratios increased from 7.5 to 16. Over a 3-mo period, algal populations in unfed anemones gradually decreased, indicating that zooxanthellae were lost faster than they were replaced by division. The mitotic index of zooxanthellae in unfed anemones was stimulated either by feeding the host or by the addition of inorganic N and P to the medium. Whether algae are nutrient-limited in hosts under field conditions has not been examined fully; however, C:N ratios in zooxanthellae from field-collected hosts are slightly higher (9.4 vs 7.5) than in hosts fed to repletion in laboratory cultures. This observation might indicate N limitation in the field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391203
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  • 5
    Electronic Resource
    Electronic Resource
    Prostaglandin F2α metabolite levels in normal and uterine-infected postpartum cows (1987)
    Springer
    Veterinary research communications 11 (1987), S. 503-507 
    Details
    ISSN: 1573-7446
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The stable metabolite of prostaglandin F2α, 15 keto-13, 14-dihydroprostaglandin F2α (PGFM), was measured from peripheral blood samples collected at specified intervals postpartum from 7 normal dairy cows and 4 cows with apparent endometritis. Plasma PFGM levels were significantly (P〈.05) elevated for the first 5 days postpartum in the cows with endometritis (ranging from 4.0 to 5.0 ng/ml) compared to the controls (approximately 1.0 ng/ml). Beyond 5 days postpartum, plasma PGFM levels were not significantly different and decreased to approximately 0.4 ng/ml by day 13 in both groups. Time to uterine involution was not different between groups (less than 30 days). Therefore, uterine infections in cows during the puerperium was associated with elevated circulating PGFM levels. These findings and the observation that PGF2α is not uterotonic in the puerperal cow do not suggest a therapeutic use of PGF2α in order to evacuate the uterus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396367
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    Paper (German National Licenses)
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