Symbiotic associations among the microplankton in oligotrophic marine environments, with special reference to the Gulf of Aqaba, Red Sea

Kimor, B.; Gordon, N.; Neori, Amir

doi:10.1093/plankt/14.9.1217

Cited by 46 publications

(25 citation statements)

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“…The distinguishing spindles connecting the H. hauckii cells and their length (40 mm), enabled identification of the Hemiaulus as H. hauckii (Heinbokel, 1986;Kimor et al, 1987Kimor et al, , 1992Villareal, 1994). Under chlorophyll excitation only H. hauckii chloroplasts were visible (Figure 3a).…”

Section: Identification and Characterization Of The Diatomdiazotroph mentioning

confidence: 99%

Seasonal dynamics of the endosymbiotic, nitrogen-fixing cyanobacterium Richelia intracellularis in the eastern Mediterranean Sea

et al. 2008

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Biological nitrogen fixation has been suggested as an important source of nitrogen for the ultraoligotrophic waters of the Levantine Basin of the Mediterranean Sea. In this study, we identify and characterize the spatial and temporal distribution of the N-fixing (diazotrophic) cyanobacterium Richelia intracellularis. R. intracellularis is usually found as an endosymbiont within diatoms such as Rhizosolenia spp and Hemiaulus spp. and is an important diazotroph in marine tropical oceans. In this study, two stations off the Mediterranean coast of Israel were sampled monthly during 2005-2007. R. intracellularis was identified by microscopy and by reverse transcribed-PCR which confirmed a 98.8% identity with known nifH sequences of R. intracellularis from around the world. The diatom-diazotroph associations were found throughout the year peaking during autumn (October-November) at both stations. Abundance of R. intracellularis ranged from 10 to 55 heterocysts l À1 and correlated positively with the dissolved Si(OH) 4 /(NO 3 þ NO 2 ) ratio in surface waters. Although the rates of nitrogen fixation were very low, averaging B1.1 nmol N l À1 day À1 for the R. intracellularis size fraction (410 lm) from surface waters, they correlated positively with heterocyst counts during thermal stratification. The lack of large-scale diatom-diazotroph blooms and the low rates of nitrogen fixation by these diazotrophs may result from the P-starved conditions affecting the Levantine basin.

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Section: Identification and Characterization Of The Diatomdiazotroph mentioning

confidence: 99%

Seasonal dynamics of the endosymbiotic, nitrogen-fixing cyanobacterium Richelia intracellularis in the eastern Mediterranean Sea

et al. 2008

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“…Among the diatoms, a mechanism that could contribute to a more diverse range of nutrient conditions is the presence of endosymbionts capable of fixing molecular nitrogen (KIMOR et al, 1992). Pseudosolenia calcar-avis (that also bloomed in both October peaks), Hemiaulus hauckii and Rhizosolenia hebetata could present symbionts under oligotrophic conditions, releasing them under favourable conditions.…”

Section: Species Response To Nutrient Variabilitymentioning

confidence: 99%

Spatio-temporal distribution of the dominant Diatom and Dinoflagellate species in the Bay of Tunis (SW Mediterranean Sea)

et al. 2005

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Microphytoplankton composition and its relationships with hydrology and nutrient distributions were investigated over 24 months (December 1993 -November 1995 in the Bay of Tunis (SW Mediterranean Sea). A new index, the 'Specific Preference Index' (SPI) obtained by computing the median value of each parameter weighed by the numerical value of each species density was developed. Using this index, the relationships between each species and temperature, salinity and major nutrients were analysed.The distribution of chlorophyll a did not show a clear correlation with microplankton abundance suggesting that other factors contribute to chlorophyll concentration, such as smaller phytoplankton size fractions or detritus. The winter-spring diatom blooms did not show a regular pattern during both years. High nutrient inputs in late summer, associated with mild meteorological conditions, contributed to the development of a large diatom bloom in autumn 1995 where significant silicate depletion was witnessed. Generally, diatoms were more stenotherm than dinoflagellates in the Bay, whereas dinoflagellates were more stenohaline than diatoms. The statistical analyses showed that the two species, Bellerochea horologicalis and Lithodesmioides polymorpha var. tunisiense, appeared in a wide range of environmental conditions. An excess of phosphate versus nitrate appeared to be associated with red tides of Gymnodinium spp, whereas Peridinium quinquecorne showed the opposite. Phosphate concentrations appear to be crucial in this coastal environment, where diatom blooms are often limited by low silicate availability.

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“…and Rhizosolenia spp.) also occur in warm oligotrophic areas of the Atlantic, the Indian Ocean, the Mediterranean and in the Red Sea (Sundstrom 1984, Kimor et al 1992, Villareal 1992,1994. It has already been proposed that these diatom endosymbionts provide a considerable contribution to overall N, fixation in oligotrophic waters (Mague et al 1974, Venrick 1974, Villareal 1991, 1992.…”

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Diatom fluxes to the deep sea in the oligotrophic North Pacific gyre at Station ALOHA

Scharek¹,

Tupas²,

Karl³

1999

Mar. Ecol. Prog. Ser.

144

103

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Planktonic diatoms are important agents of vertical transport of photosynthetically fixed organic carbon to the ocean's interior and seafloor. Diatom fluxes to the deep sea were studied for 2 yr using bottom-moored sequencing sediment traps located in the vicinity of the Hawaii Ocean Timeseries (HOT) program station 'ALOHA ' (22'45'N, 158" W). The average flux of empty diatom frustules was around 2.8 X 10' cells m-' d ' in both years, except in late summer when it increased approximately 30-fold. Flux of cytoplasm-containing diatom cells was much lower (about 8 X 103 cells n1Y2 d") but increased 500-fold in late July 1992 and 1250-fold in August 1994. Mastogloia woodiana Taylor, Hemjaulus hauckii Grunow and Rliizosolenia cf. clevei var. communis Sundstrom were the domlnant diatom species observed during the July 1992 event, with the former 2 species again dominant in August 1994. The 1994 summer flux event occurred about 3 wk after a documented bloom of H. hauckii and M. woodiana in the mixed-layer and a simultaneous increase in vertical flux of these species. This surface flux signal was clearly detectable at 4000 m, suggesting rapid settling rates. A further indication of very high sinking speeds of the diatoms was the much larger proportion of cytoplasm-containing cells in the bottom-moored traps during the 2 summer events. Cells of H. hauckii and R. cf. clevej var. communis frequently contained endosymbiotic cyanobacteria with heterocysts (cf. Richelia), similar to the cells of these specles in the mixed-layer. Our data show for the first time that diatoms containing nitrogenfixing cyanobacteria contribute drectly to the vertical flux of organic matter to the deep sea in the oligotrophic regions. The peak of diatom flux coincided with a significant flux increase of biogenic silica in both years. During periods of rapid sinking, the vertical flux of diatom assemblages out of the uppermost water column seems to be more important than the diatom flux out of the deep chlorophyll maximum layer (DCML). Aggregate formation may be responsible for the fast sinking of the diatoms.

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Symbiotic associations among the microplankton in oligotrophic marine environments, with special reference to the Gulf of Aqaba, Red Sea

Cited by 46 publications

References 0 publications

Seasonal dynamics of the endosymbiotic, nitrogen-fixing cyanobacterium Richelia intracellularis in the eastern Mediterranean Sea

Seasonal dynamics of the endosymbiotic, nitrogen-fixing cyanobacterium Richelia intracellularis in the eastern Mediterranean Sea

Spatio-temporal distribution of the dominant Diatom and Dinoflagellate species in the Bay of Tunis (SW Mediterranean Sea)

Diatom fluxes to the deep sea in the oligotrophic North Pacific gyre at Station ALOHA

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