Dimethylsulfoniopropionate Production Research Articles

DMSP in marine macroalgae and macroinvertebrates: Distribution, function, and ecological impacts

The production of dimethylsulfoniopropionate (DMSP) and its cleavage products are well studied in phytoplankton. However, less is known about their sources, distributions, functions, and impacts in other marine organisms. We examined the distribution of DMSP in benthic macroalgae and macroinvertebrates geographically and taxonomically. In macroalgae, concentrations significantly increased from the tropics to the poles in the northern, but not the southern, hemisphere. The increase in the northern hemisphere was due to an increase in concentrations with latitude in the Chlorophyta. This pattern was generated by a relatively high proportion of species in the order Ulvales (median [DMSP]: 145 μmol g-1 dry mass (DM)) at higher latitudes, and a high proportion of species in the orders Caulerpales and Siphonocladales (median [DMSP]: below detection level for both orders) in the tropics. Low DMSP concentrations (< 10 μmol g-1 DM) were reported from all red and brown macroalgae, except Polysiphonia and Halopytis. In macroalgae, some of the reported functions of DMSP and its cleavage products included acting as a compatible solute, an anti-herbivore defense, a reactive oxygen scavenger, and a cryoprotectant. Among macroinvertebrates, DMSP occurred in higher concentrations in cnidarians than in sponges and molluscs. Concentrations in animals harboring endosymbiotic algae were 6.5 times higher than animals without symbionts. This and direct measurements of DMSP from isolated symbionts suggest that endosymbionts are a major source of DMSP for some macroinvertebrates. Diet may be a source of DMSP in animals that lack endosymbionts. The functions and impacts of DMSP in invertebrates are not well known.

Effect of the diel cycle on production of dimethylsulfoniopropionate in batch cultures of Emiliania huxleyi

Changes in intracellular dimethylsulfoniopropionate (DMSP), nitrogen, carbon, chlorophyll a (chl a), total cell volume and cell numbers were measured during day and night in axenic, exponentially growing batch cultures of the coccolithophorid, Emiliania huxleyi, cultured at 20°C under a 12 h light:12 h dark cycle. Cellular DMSP content in the cultures increased at a specific rate of 0.80 ± 0,10 d -1 (mean ± SE) during the day and 0.53 ± 0.12 d -1 at night. By contrast, cellular carbon and chl a content of the culture and total cell volume increased only during the day (at specific rates of 1.30 ± 0.08 d -1 , 1.54 ± 0.12 d -1 and 1.39 ± 0.12 d -1 , respectively). Cellular nitrogen content of the culture showed a much higher specific rate of increase during the day (1.07 ± 0.07 d -1 ) than at night (0.22 ± 0.03 d -1 ). Because intracellular DMSP had a lower specific rate of synthesis during the day and a higher specific rate at night than specific production rates for the various cell biomass parameters (total cell volume, and cell carbon, nitrogen and chl a), ratios of DMSP to these parameters were highest at the end of the dark period and decreased during the day. The maximum intracellular DMSP concentrations at the beginning of the light period may provide some level of protection from oxidative stress with the daytime initiation of photosynthesis. Significant intracellular production of DMSP during the night contradicts current conventional wisdom, which assumes that no nighttime biosynthesis of DMSP occurs. Previous calculations based on this invalid assumption will need to be reassessed.

Assessing microbial responses to iron enrichment in the Subarctic Northeast Pacific: Do microcosms reproduce the in situ condition?

Abstract A microcosm experiment was conducted in the NE Pacific in July 2002 to compare the microbial response between microcosms and the Subarctic Ecosystem Response to Iron-Enrichment Study (SERIES) in situ iron-enrichment experiment. Seawater microcosms (20 L) were incubated aboard ship under natural light using three treatments: (1) low-iron seawater amended with 4 nmol l−1 FeSO4 (+Fe); (2) low-iron seawater amended with 4 nmol l−1 FeSO4 and 86 nmol l−1 GeO2 (+Fe+Ge); (3) seawater collected from the in situ Fe-enriched patch (PW). The +Fe+Ge treatment used germanium to control diatom growth to assess the role of diatoms in dimethylsulfoniopropionate (DMSP) production. The following variables were measured in the microcosms and in situ: chlorophyll a (chl a), nitrate ( NO 3 - ), silicic acid (Si(OH)4), phytoplankton abundance and species identification, bacterial abundance (including estimates of low- and high-DNA bacteria), bacterial production, bacterial specific growth rate, particulate and dissolved DMSP and dimethylsulfide (DMS) concentrations. There was little or no significant difference (ANCOVA) in the response of most variables between the +Fe and PW microcosms, but large differences were observed between both these treatments and the in situ data from the enriched patch. Chl a in all microcosms increased from ambient levels (approx. 0.5–1 μg l−1) to approx. 4.5–6.2 μg l−1 after 11 d incubation, when NO 3 - was fully depleted from all microcosms. During this same period, in situ chl a increased more slowly to a maximum of 2.9 μg l−1 on day 11. Nanophytoplankton and picophytoplankton were more abundant in the microcosms relative to the in situ community, which became dominated by large diatoms. Bacterial abundance was similar in the microcosms and in situ, but bacterial production was significantly higher in the microcosms. While neither DMSPd nor DMS accumulation showed significant differences between the microcosms and in situ, particulate DMSP concentrations increased significantly faster in the +Fe and PW treatments. These differences represent bottle effects resulting from the containment of the microcosms, which suppresses grazing, alters community and food web structure, enhances iron and nutrient regeneration, and isolates the community from physical transport and export processes including sinking. Thus during this experiment, the microcosms were not a good model for the in situ system in terms of the effects of iron on the phytoplankton biomass, nutrient uptake, bacterial dynamics and DMSPp production. In the germanium-amended treatment, the inhibition of diatom growth resulted in enhanced growth of other taxa and a suppression of bacterial production, leading to increased production of DMSP and DMS and strong correlations between DMSP, DMS and non-diatom phytoplankton taxa. Diatoms did not contribute significantly to particulate DMSP concentrations.

Dimethylsulfide and major sulfur compounds in a stratified coastal salt pond

We conducted a diurnal study of gradients of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), dimethylsulfoxide (DMSO), and bacterial numbers in a stratified coastal salt pond (Salt Pond, Falmouth, Massachusetts). Microlayer samples were collected with a surface skimmer, a partially submerged rotating glass cylinder that allows the collection of a thin layer of water by adherence to the drum. All sulfur compounds and bacteria increased toward the water surface, with a diurnal signal in DMSP and DMSO. Fractionation of DMSP and DMSO in dissolved (d) and particulate (p) pools revealed that any trend in DMSP was due to the p fraction, and trends in DMSO originated from the d fraction. Photoeffects are important for the distribution of DMSPp and DMSOd. In Salt Pond, the production of DMSP is probably linked to photosynthesis, and photooxidation is of greater importance to the production of DMSO than is biological oxidation.

Biogeochemistry of Dimethylsulfoniopropionate (DMSP) in the Surface Microlayer and Subsurface Seawater of Funka Bay, Japan

Twenty-eight sea surface microlayer samples, along with subsurface bulk water samples were collected in Funka Bay, Japan during October 2000–March 2001 and analyzed for dimethylsulfoniopropionate, dissolved (DMSPd) and particulate (DMSPp), and chlorophyll a. The aim of the study was to examine the extent of enrichment of DMSP in the microlayer and its relationship to chlorophyll a, as well as the production rate of dimethylsulfide (DMS) from DMSP and the factors that influence this. The enrichment factor (EF) of DMSPd in the surface microlayer ranged from 0.81 to 4.6 with a mean of 1.85. In contrast, EF of DMSPp in the microlayer varied widely from 0.85–10.5 with an average of 3.21. Chlorophyll a also appeared to be enriched in the microlayer relative to the subsurface water. This may be seen as an important cause of the observed enrichment of DMSP in the microlayer. The concentrations of DMSPp in the surface microlayer showed a strong temporal variation, basically following the change in chlorophyll a levels. Moreover, the microlayer concentrations of DMSPp were, on average, 3-fold higher than the microlayer concentrations of DMSPd and there was a significant correlation between them. Additionally, there was a great variability in the ratios of DMSPp to chlorophyll a over the study period, reflecting seasonal variation in the proportion of DMSP producers in the total phytoplankton assemblage. It is interesting that the production rate of DMS was enhanced in the microlayer and this rate was closely correlated with the microlayer DMSPd concentration. Microlayer enrichment of chlorophyll a and higher DMS production rate in the microlayer provide favorable evidence supporting the view that the sea surface microlayer has a greater biological activity than the underlying water.

Annual contribution of different plankton size classes to particulate dimethylsulfoniopropionate in a marine perturbed ecosystem

Dimethylsulfoniopropionate (DMSP) concentrations were observed from October 1999 to September 2000 in a Mediterranean ecosystem (Little Bay of Toulon) submitted to eutrophication. DMSP was measured in the particulate material (DMSP p), and more specifically in the >90, 5–90 and 0.2–5 μm fractions. DMSP was first converted into dimethylsulfide (DMS) by a cold alkali treatment. DMS was then analysed by gas chromatography equipped with a flame photometric detector (FPD). DMSP p concentrations were relatively high, showing a strong temporal variability with maxima in February–March (58.8 nM). The most elevated values were recorded in the 5–90 μm size class, and represented between 60% and 100% of the total DMSP p. This fraction was mostly composed of Dinoflagellates whose biomass was significantly correlated with DMSP p concentrations. These concentrations showed better correlations with Ceratium furca, Dinophysis acuminata, Prorocentrum arcuatum and also Alexandrium minutum. The intracellular contents of DMSP were much higher in Dinoflagellates (124.9±5.7 mM) than in Diatoms (25.1±1.1 mM). A. minutum produced the strongest intracellular concentrations (3387.6±121.9 mM). High DMSP contents were also found in D. acuminata (477.4±64.3 mM) and P. arcuatum (442.2±22.9 mM). The >90 μm size class had a minor importance in DMSP production, generally below 20% of the total DMSP p. However, DMSP in the >90 μm fraction was well correlated with cladoceran abundance. Plankton cells between 0.2 and 5 μm contained a low part of the DMSP p pool, lower than 20%. Besides, no correlation was found between their algal abundances and DMSP in the 0.2–5 μm size class. Temperature and photoperiod could have influenced the Dinoflagellate development, and consequently, the DMSP p concentrations. The strong autumnal rains affected the composition of the phytoplankton community and the production of sulfur compounds. These particular climatic conditions have induced an increase in nutrient concentrations and a drop in salinity, which may explain the low autumnal DMSP p concentrations.

DIMETHYLSULFONIOPROPIONATE PRODUCTION BY PSYCHROPHILIC DIATOM ISOLATES1

Dimethylsulfoniopropionate (DMSP) production by psychrophilic diatom strains, Chaetoceros sp., Navicula sp., and Nitzschia sp., were experimentally analyzed. All strains showed rapid growth (0.3–0.5 d−1) under cold culture conditions (1.7°C). DMSP concentrations (both as particulate, DMSPp, and dissolved, DMSPd) were negligible in cultures of Chaetoceros sp., whereas those for Navicula sp. and Nitzschia sp. increased toward the end of the 56‐day experiments. The ratio of DMSPp:chl a of the latter two species was approximately 5 in the early exponential growth phase and decreased slightly toward the early stationary phase. During the stationary phase, when chl a and fluorescence remained constant, the ratios in both species increased linearly by up to approximately 6.5 times the value at the start of the stationary phase. This growth‐related DMSP production by diatoms may result in the low concentrations of DMSPp observed in the early stage of diatom blooms under natural conditions.

164 Chemical Antiherbivore Defenses of Temperate Green Macroalgae

Many temperate green macroalgae contain secondary meatbolites that provide protection from grazing by some herbivores. These include the production of dopamine hydrochloride by the ulvoid green alga Ulvaria obscura and the production of dimethylsulfoniopropionate (DMSP) by many species of Ulvales and Caulerpales. The dopamine hydrochloride defense was isolated using bioassay‐guided fractionation and is effective against sea urchins (Strongylocentrotus droebachiensis) and littorinid snails (Littorina sitkana). The DMSP activated defense system involves enzymatic cleavage of DMSP into dimethyl sulfide (DMS) and acrylic acid. It is found in many of the Ulvales and several species of Codium in the northeastern Pacific and Australasian regions. Many green algae such as Ulva fenestrata and Enteromorpha linza are avoided by urchins, which are deterred by DMS and acrylic acid in laboratory assays. However, these algae are often preferred foods of snails, which are deterred by DMS and acrylic acid. Snails may preferentially consume ulvoid green algae, despite being deterred by DMS and acrylic acid, because these algae contain relatively high nitrogen concentrations.

Dimethylsulfide release during macroinvertebrate grazing and its role as an activated chemical defense

Almost half the biogenic sulfur emitted globally originates as dimethylsulfide (DMS) in marine algae. Yet, despite its importance to climate and the global sulfur cycle, the reasons why many diverse algal taxa produce DMS remain unclear. DMS is produced when dimethylsulfoniopro- pionate (DMSP) is cleaved by the enzyme DMSP lyase into DMS and acrylic acid. Because acrylic acid can deter feeding by some herbivores, the production of DMSP has been postulated to be part of an antiherbivore chemical defense system, with DMS being a by-product of the production of the defensive compound acrylic acid. However, we found that DMS plays a more direct role in herbivore deterrence. Using laboratory bioassays, we demonstrated that DMS functions as a potent feeding deterrent against sea urchins Strongylocentrotus droebachiensis at a wide range of concentrations. The defensive function of DMSP cleavage is further supported by the results of a multiple-choice feeding preference assay in which we offered urchins a choice of 8 algal species. In these assays, algae containing DMSP tended to be consumed at lower rates than species that lacked it. By measur- ing headspace DMS concentrations during grazing, we showed that DMS is produced when urchins feed on algae containing DMSP, but not when urchins feed on algae without it. DMS production occurred while the urchins were feeding on the algae and for 18 h after the algae were removed, suggesting that post-ingestive processes might be playing a role in activation. These results demon- strate that DMS is produced when urchins feed on algae containing DMSP and that it functions as an herbivore deterrent, causing species that produce DMSP to be avoided by some herbivores.

Temperature, light, and the dimethylsulfoniopropionate (DMSP) content of Emiliania huxleyi (Prymnesiophyceae)

The precursor of the volatile S-compound dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), is produced by marine microalgae, notably by Prymnesiophyceae. The production of DMSP by an axenic isolate of Emiliania huxleyi (Lohm.) Hay et Mohler under different temperature and light conditions was studied as a first step towards understanding the role of DMSP-producing algae in climate regulation. Both light and temperature affected growth rate and cell size in batch cultures, but the concentration of DMSP in the cells was dependent on temperature only: at low temperature DMSP accumulated. This physiological response, assumed to be characteristic of DMSP-producing microalgae in general, is in line with the correlation that has been found between elevated concentrations of the DMS oxidation product MSA in ice core slices corresponding with low sea surface temperatures. Apparently, DMS does not play the role in climate regulation formulated in the CLAW hypothesis that proposes a feedback mechanism in which elevated temperatures lead to an increase in albedo via DMS-derived cloud condensation nuclei.

Production and consumption of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) in a diatom-dominated intertidal sediment

Intertidal sediments usually contain a high amount of dimethylsulfoniopropionate (DMSP) and therefore represent environments with a potentially high emission of dimethylsulfide (DMS). However, knowledge on production and release of DMSP in intertidal sediments is limited. Here, we present data on the diel variation of the total DMS and DMSP content (DMS(P)total) and the DMS(P) concentration in the porewater (DMS(P)porewater) in an intertidal sediment covered by diatoms. Measurements were made at low tide during the day and during the night. Both DMS(P)total and DMS(P)porewater were constant and did not respond to the changing conditions of light and oxygen in the sediment, indicating that production and consumption processes were in equilibrium. Incuba- tion of diatoms under light/oxic, dark/oxic and dark/anoxic conditions suggested that no large amounts of DMSP were excreted under the different conditions applied. DMS(P)porewater was around 100 nM, which was about 3 orders of magnitude lower than DMS(P)total. Only after the onset of a heavy rainfall DMS(P)porewater in the sediment suddenly increased above 1 µM, which was explained by excretion of DMSP by DMSP-containing microorganisms in response to the osmotic shock. Both DMSP and DMS were rapidly degraded in sediment slurries, especially under oxic conditions, and degradation closely followed first order kinetics. We conclude that although intertidal sediments con- tain high total amounts of DMSP, a relatively low amount of DMSP is released by the microphyto- benthos under naturally fluctuating light and oxygen conditions, and once released, DMSP and DMS are rapidly degraded in the upper oxygenated sediment. This explains the low flux of DMS from intertidal sediments to the atmosphere reported in the literature.

UV radiation induced stress does not affect DMSP synthesis in the marine prymnesiophyte Emiliania huxleyi

A possible coupling between UV radiation (UVR; 280 to 400 nm) induced stress and the production of dimethylsulfoniopropionate (DMSP), the precursor of the climate-regulating gas dimethylsulfide (DMS), was investigated in the marine prymnesiophyte Emiliania huxleyi. To this end, axenic cultures of E. huxleyi were exposed to a range of UVR doses for 2 consecutive days. During and after these treatments, growth, photosynthetic activity, cell size, DNA damage, sugar accumulation and DMSP concentrations were followed. The vulnerability of E. huxleyi for relatively low UVR doses was demonstrated by the inhibition of growth and the simultaneous occurrence of DNA damage. Also, mean cell size increased and sugars accumulated as a result of the UVR treat- ments. In contrast, no effect was observed on the optimal quantum yield of Photosystem II (PSII), a measure of the efficiency of photosynthesis. With increasing UVR dose, cellular DMSP content increased. However, the intracellular DMSP concentrations remained constant at the level typical for the applied temperature and salinity conditions, due to accompanying increase in cell size. The increased cellular DMSP content did not compensate, therefore, for the decreased growth rates, resulting in an overall decrease in the total amount of DMSP produced in the cultures. The UVR effects as induced in this study are assumed to be severe as compared with natural solar conditions, especially because high in situ UVAR (315 to 400 nm) may ameliorate UVBR damage by activation of photorepair. Yet the presented results imply that when (increased) UV(B)R causes growth rate reduc- tion of E. huxleyi in situ, DMSP fluxes are likely to be reduced too.

Effects of iron, silicate, and light on dimethylsulfoniopropionate production in the Australian Subantarctic Zone

Shipboard bottle incubation experiments were performed to investigate the effects of iron, light, and silicate on algal production of particulate dimethylsulfoniopropionate (DMSPp) in the Subantarctic Zone (SAZ) south of Tasmania during March 1998. Iron enrichment resulted in threefold to ninefold increases in DMSPp concentrations relative to control treatments, following 7 and 8‐day incubation experiments. Additions of Fe and Si preferentially stimulated the growth of lightly‐silicified pennate diatoms and siliceous haptophytes, respectively, to which we attribute the increased DMSPp production in the incubation bottles. Both of these algal groups were previously believed to be low DMSPp producers; however, our experimental data suggest that addition of iron and silicate to the low‐silicate low‐iron waters of the SAZ will result in increased production of DMSPp by lightly silicified diatoms and siliceous haptophytes, respectively. Increased irradiance enhanced DMSPp production in iron‐amended treatments with both low (0.5 nM) and high (5 nM) concentrations of added iron. However, the role of light in stimulating DMSPp production was apparently of secondary importance compared to the effects of iron addition. The combination of high irradiance and high iron enrichment produced the highest DMSPp production in the experiments, suggesting that iron and light may have a synergistic effect in limiting algal DMSPp production in subantarctic waters.

Production of glycine betaine and dimethylsulfoniopropionate in marine phytoplankton. I. Batch cultures

The quantitative significance of the nitrogenous compound glycine betaine (GBT) and its sulfur analog dimethylsulfoniopropionate (DMSP) to intracellular pools in marine phytoplankton is not well known. In a series of experiments conducted in August 1993, we measured these compounds, as well as total organic sulfur, carbon, and nitrogen, over the growth cycle in six isolates of marine phytoplankton, Amphidinium carterae Hulburt, Chrysochromulina sp. Lackey, Emiliania huxleyi Hay et Mohler, Prorocentrum minimum (Pavillard) Schiller, Skeletonema costatum (Greville) Cleve, and Tetraselmis sp. At the same time, we measured cellular concentrations of protein, amino acids, chlorophyll, and inorganic nutrients. All six species produced DMSP, while three produced GBT at lesser levels. In the Chrysochromulina sp. isolate, levels of GBT were greater than DMSP during the exponential phase of growth, but declined sharply as the culture approached stationary phase. This change appeared to coincide with the onset of nitrogen limitation. Other nitrogenous osmolytes were produced in five of the six species but in much smaller quantities. DMSP contributed significantly to cellular sulfur throughout the growth cycle although, in some algae, the proportion of dissolved DMSP increased substantially during stationary growth. When present, GBT formed a sizeable fraction of the cellular nitrogen only during exponential growth. A significant percentage (ca. 50%) of the organic nitrogen could not be accounted for even when cellular pools of protein, amino acids, inorganic nitrogen, and nitrogenous osmolytes were combined. Based on these experiments, there does not appear to be a reciprocal relationship between DMSP and GBT production, although GBT production does appear to be correlated with nitrogen availability.

Dimethylsulfoxide (DMSO) and related sulfur compounds in the Saguenay Fjord, Quebec

The biogeochemical cycling of dimethylated sulfur compounds was investigated in the Saguenay Fjord during June 1996, just prior to the flooding in the catchment area. Dimethylated sulfur compounds, namely dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide (DMSO), were determined at six sites. In comparison with other coastal environments, including the Gulf of St. Lawrence, DMS (0-1.8 nmol·L-1, average &lt;0.2 nmol·L-1) and DMSP (0-23 nmol·L-1, average &lt;0.8 nmol·L-1) concentrations were relatively low because the brackish waters were poor in algal abundance and dominated by species not noted as major DMS and DMSP producers. Similarly, dissolved DMSO levels (&lt;0.016 nmol·L-1) were low due to the limited availability of its DMS precursor and the shallow photic zone. Particulate DMSO was measured (0-110 nmol·L-1, average ~8 nmol·L-1) and occasionally exceeded particulate DMSP concentrations (0.016-140 nmol·L-1, average ~3.5 nmol·L-1). Given the low dissolved DMSO concentrations, the presence of particulate DMSO provides evidence for its direct biosynthesis by phytoplankton.

Microbial consumption and production of dimethyl sulfide (DMS) in the Labrador Sea

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 18:197-205 (1999) - doi:10.3354/ame018197 Microbial consumption and production of dimethyl sulfide (DMS) in the Labrador Sea Gordon V. Wolfe*, Maurice Levasseur**, Guy Cantin, Sonia Michaud Institut Maurice-Lamontagne, Ministère des Pêches et des Océans, CP 1000, Mont-Joli, Québec G5L 3A1, Canada *Present address: College of Oceanic and Atmospheric Sciences, Oregon State University, 104 Ocean. Admin. Bldg., Corvallis, Oregon 97331-5503, USA. **Addressee for correspondence. E-mail: levasseurm@dfo-mpo.gc.ca ABSTRACT: We examined microbial production and consumption of dimethyl sulfide (DMS) in Labrador Sea surface waters ranging in temperature from -0.1 to 6.9°C. 200 nM dimethyl disulfide (DMDS) was used to inhibit DMS consumption. We also studied DMS consumption kinetics by additions of 5 to 50 nM DMS, DMS production from added dimethylsulfoniopropionate (DMSP), and DMS production and consumption during zooplankton grazing. During the cruise, DMS concentrations were low, ranging from 1 to 7 nM throughout the study area, which included a bloom of the colonial haptophyte alga Phaeocystis pouchetii. DMDS additions often revealed rapid DMS production and consumption (up to 5 nM d-1) and very rapid turnover (<1 to 3 d), similar to rates found in coastal waters at much higher temperatures. There was no clear effect of temperature on DMS consumption; rather, DMS consumption appeared to be tightly coupled with production. Turnover was most rapid at low DMS concentrations, and DMS consumption was stimulated by additions of DMS, or by increased DMS production from additions of dissolved DMSP. DMDS additions to zooplankton grazing incubations revealed rapid gross DMS production and consumption which were nearly balanced, resulting in net steady-state DMS patterns. DMDS did not affect production or grazing of algal pigments or DMSP. DMS consumption saturated at 18 to 32 nM [DMS] and saturation kinetics were similar within the photic zone, but consumption was near-zero at greater depths. We suggest that DMS consumption likely saturates more easily than microbial DMS production from DMSP, and this, combined with temperature limitation on the growth of prokaryotic DMS consumers, may lead to the periodic buildup of high DMS concentrations previously observed in polar and subpolar waters. KEY WORDS: Dimethyl sulfide · Dimethylsulfoniopropionate · DMSP · DMS · Inhibitor technique · Consumption kinetics · Zooplankton grazing Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 18, No. 2. Publication date: August 09, 1999 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 1999 Inter-Research.

DMSP synthesis and exudation in phytoplankton:a modeling approach

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 180:37-49 (1999) - doi:10.3354/meps180037 DMSP synthesis and exudation in phytoplankton: a modeling approach D. Laroche1,2, A. F. Vézina1,*, M. Levasseur1, M. Gosselin2, J. Stefels3, M. D. Keller4, P. A. Matrai4, R. L. J. Kwint3 1Institut Maurice-Lamontagne, Ministère des Pêches et des Océans, CP 1000, 850 route de la Mer, Mont-Joli, Québec G5H 3Z4, Canada 2Département d'océanographie, Université du Québec à Rimouski, 310, allée des Ursulines, Rimouski, Québec G5L 3A1, Canada 3Department of Marine Biology, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands 4Bigelow Laboratory for Ocean Sciences, 180 McKown Point, W. Boothbay Harbor, Maine 04575-475, USA *Addressee for correspondence. E-mail: vezinaa@dfo-mpo.gc.ca ABSTRACT: In the marine environment, phytoplankton are the fundamental producers of dimethylsulfoniopropionate (DMSP), the precursor of the climatically active gas dimethylsulfide (DMS). DMSP is released by exudation, cell autolysis, and zooplankton grazing during phytoplankton blooms. In this study, we developed a model of phytoplankton DMSP and DMS production allowing quantification of the exudation rates of these compounds during different growth phases. The model was tested on published data from axenic cultures of Prorocentrum minimum and Phaeocystis sp.; DMSP exudation rates vary considerably between the 2 species. Model results show that P. minimum exudes around 1% d-1 of its DMSP quota during the latent, exponential and senescent phases. This is comparable to the average exudation rate estimated from previous laboratory experiments. However, Phaeocystis sp. exudes from 3 to 11% d-1 of its DMSP quota. For this species, DMSP exudation rates apparently show an inverse relationship with the population growth rate. The maximum DMSP exudation rate in Phaeocystis sp. is 10 times higher than previously reported DMSP or DMS exudation rates. Our results suggest that exudation may be as important as cell autolysis in the release of DMSP during Phaeocystis sp. blooms. We conclude that exudation should be incorporated in models of DMS cycling in the marine environment. Moreover, our results for Phaeocystis sp. suggest that a low and constant exudation rate, as sometimes used in models, is not suitable for all conditions. KEY WORDS: DMS · DMSP · Exudation · Synthesis · Phaeocystis · Model Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 180. Publication date: May 03, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Spatial distribution of dimethylsulfide and dimethylsulfoniopropionate in the Australasian sector of the Southern Ocean

During 1991–1995, seven voyages were made to the Southern Ocean to determine the distribution of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) in seawater and air in the Australasian sector (60°E to 165°E). Measurements of DMSP in sea ice were also made. During the summer months the Subtropical Convergence (STC) and Antarctic Convergence (AC) were identified as important source regions of these sulfur compounds. In the Seasonal Ice zone (SIZ) there were marked longitudinal differences possibly reflecting higher productivity and the extent of the sea ice in this region. Levels of DMSP in sea ice cores were consistent with this regional difference. High and variable concentrations of DMSP also occurred in the Subantarctic Zone (SAZ) (45°‐53°S), decreasing to lower levels around 64°S, close to the Antarctic Divergence (AD). Upwelling of deep water around the AD is suggested to have been responsible for the low biological activity and low DMSP levels. While there was generally a good relationship between DMSPp and biomass, there was a marked difference in the DMSPp:chlorophyll a ratio between regions, and between years. DMSP was generally negatively correlated with dissolved nitrate, however, it was unclear if the level of nitrate directly affected DMSP production. DMSwlevels were highest in the mixed layer, with lower, yet detectable, levels in the deeper ocean. DMSwwas occasionally elevated in Antarctic Bottom Water (AABW), suggesting that ice shelf water transports this substance to deeper waters. DMSP was not found above detection limits below the mixed layer, but some evidence was found that DMSP may be transported to deeper waters, close to the Antarctic continent.

Release of Dimethylsulfide from Dimethylsulfoniopropionate by Plant-Associated Salt Marsh Fungi

The range of types of microbes with dimethylsulfoniopropionate (DMSP) lyase capability (enzymatic release of dimethylsulfide [DMS] from DMSP) has recently been expanded from bacteria and eukaryotic algae to include fungi (a species of the genus Fusarium [M. K. Bacic and D. C. Yoch, Appl. Environ. Microbiol. 64:106-111, 1998]). Fungi (especially ascomycetes) are the predominant decomposers of shoots of smooth cordgrass, the principal grass of Atlantic salt marshes of the United States. Since the high rates of release of DMS from smooth cordgrass marshes have a temporal peak that coincides with peak shoot death, we hypothesized that cordgrass fungi were involved in this DMS release. We tested seven species of the known smooth cordgrass ascomycetes and discovered that six of them exhibited DMSP lyase activity. We also tested two species of ascomycetes from other DMSP-containing plants, and both were DMSP lyase competent. For comparison, we tested 11 species of ascomycetes and mitosporic fungi from halophytes that do not contain DMSP; of these 11, only 3 were positive for DMSP lyase. A third group tested, marine oomycotes (four species of the genera Halophytophthora and Pythium, mostly from mangroves), showed no DMSP lyase activity. Two of the strains of fungi found to be positive for DMSP lyase also exhibited uptake of DMS, an apparently rare combination of capabilities. In conclusion, a strong correlation exists between a fungal decomposer's ability to catabolize DMSP via the DMSP lyase pathway and the host plant's production of DMSP as a secondary product.

Alkali-labile precursors of dimethyl sulfide in marine benthic cyanobacteria

By the method of cold alkali hydrolysis, 29 marine benthic cyanobacteria were screened for production of alkali-labile precursors of dimethyl sulfide (DMS) including dimethylsulfoniopropionate (DMSP), a compound of significant importance in marine environments. Concentrations of DMS precursors ranged from undetectable to 0.8 mmol (g Chl a)-1. The data correspond to some previous investigations concerning DMSP content of marine cyanobacteria and suggest that marine benthic cyanobacteria are only minor producers of DMSP.