Monsoon-driven biogeochemical dynamics in an equatorial shelf sea: time-series observations in the Singapore Strait

Marine dimethyl sulfide (DMS) emissions are an important source of atmospheric sulfate aerosols which exert a strong influence on climate. The major biological precursor for DMS is dimethylsulfoniopropionate (DMSP), an abundant compatible solute produced by many marine eukaryotes and prokaryotes.&#160; Despite the importance of DMSP, knowledge of how, why and by what it is produced is limited. For example, haptophytes (inc. coccolithophores) and dinoflagellates typically produce 50-100 times more DMSP per unit Chlorophyll a than diatoms and prochlorophytes. However, the reasons for this are not fully understood as the relevant enzymes have until recently been poorly characterised. Furthermore, although the DMSP synthesis genes and their transcripts are widespread in surface ocean bacterial communities, the contribution by this group of organisms to total DMSP production is so far unquantified. Here, we present a 6-month time series (April &#8211; September 2018) of in-vivo DMSP synthesis rates at an established time series station in temperate shelf sea waters, alongside characterisation of the key S-methylation step of DMSP synthesis pathways. DMSP concentrations ranged from 21 &#8211; 165 nM, with peaks in DMSP production rates in late April (26.1 nmol L-1 d-1) and early July (19.1 nmol L-1 d-1). These DMSP production peaks coincided with significant increases in the abundance of known DMSP producing algae and bacteria, and of their transcription of DSYB/dsyb genes, as indicated by RT-qPCR and &#8216;omics analysis. &#160;These novel state and rate data, have been used to refine a DMS dynamics model by including newly defined DMSP-specific functional types, including both algal and bacterial DMSP producers.

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The LDE-Type Flare Occurrence (1969-1993)

International Astronomical Union Colloquium ◽

10.1017/s0252921100025458 ◽

1994 ◽

Vol 144 ◽

pp. 279-282

Author(s):

A. Antalová

Keyword(s):

Time Series ◽

Fourier Analysis ◽

Sunspot Cycle ◽

List Type ◽

Type Number ◽

Solar Cycles ◽

Type Iv ◽

Long Duration ◽

Cycle Maximum ◽

Flare Index

AbstractThe occurrence of LDE-type flares in the last three cycles has been investigated. The Fourier analysis spectrum was calculated for the time series of the LDE-type flare occurrence during the 20-th, the 21-st and the rising part of the 22-nd cycle. LDE-type flares (Long Duration Events in SXR) are associated with the interplanetary protons (SEP and STIP as well), energized coronal archs and radio type IV emission. Generally, in all the cycles considered, LDE-type flares mainly originated during a 6-year interval of the respective cycle (2 years before and 4 years after the sunspot cycle maximum). The following significant periodicities were found:• in the 20-th cycle: 1.4, 2.1, 2.9, 4.0, 10.7 and 54.2 of month,• in the 21-st cycle: 1.2, 1.6, 2.8, 4.9, 7.8 and 44.5 of month,• in the 22-nd cycle, till March 1992: 1.4, 1.8, 2.4, 7.2, 8.7, 11.8 and 29.1 of month,• in all interval (1969-1992):a)the longer periodicities: 232.1, 121.1 (the dominant at 10.1 of year), 80.7, 61.9 and 25.6 of month,b)the shorter periodicities: 4.7, 5.0, 6.8, 7.9, 9.1, 15.8 and 20.4 of month.Fourier analysis of the LDE-type flare index (FI) yields significant peaks at 2.3 - 2.9 months and 4.2 - 4.9 months. These short periodicities correspond remarkably in the all three last solar cycles. The larger periodicities are different in respective cycles.

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