Role of dimethylsulfoniopropionate as an osmoprotectant following gradual salinity shifts in the sea-ice diatom Fragilariopsis cylindrus

Abstract

Environmental context Dimethylsulfoniopropionate (DMSP), a small sulfur compound biosynthesised by algae, plays an important role in global climate, particularly in polar regions. We investigated salinity effects on DMSP levels, and provide the first experimental measurements of DMSP and associated physiological changes in a polar diatom across to a range of gradual salinity shifts representative of sea-ice conditions. Quantitative estimates of DMSP in polar diatoms following salinity changes will facilitate new mathematical models to predict seasonal responses and reactions to climate change. Abstract Although extreme environmental gradients within sea-ice have been proposed to stimulate dimethylsulfoniopropionate (DMSP) accumulation in diatoms, a taxa whose temperate counterparts show relatively low concentrations, this has yet to be experimentally validated across a range of salinities representative of sea-ice conditions. The present study examined changes in DMSP concentrations in the widespread polar diatom Fragilariopsis cylindrus in response to gradual salinity shifts representative of those encountered during sea-ice formation and melt. DMSP concentrations were elevated up to 127% in 70-salinity cultures. Low-salinity shifts decreased intracellular DMSP concentrations in a gradient-dependent manner that suggests DMSP recycling rather than release under milder hyposalinity shifts. Permeable membranes were detected in ~45% of 10-salinity cells; therefore, loss of membrane integrity may only partially explain DMSP release in the lowest-salinity group. Growth rates, photosynthetic efficiency of photosystem II and reactive oxygen species detection indicated only partial impairment by salinity stress in this organism. Thus, experimental evidence supports the role of DMSP as a compatible solute in the acclimation of a sea-ice diatom across large salinity gradients and measurements of associated physiological changes will improve interpretation of environmental measurements.

Use of exogenous glycine betaine and its precursor choline as osmoprotectants in Antarctic sea‐ice diatoms1

“…In our study, intracellular GBT concentrations at normal seawater salinity (Table ) exceeded the values previously reported for DMSP in F. cylindrus (Lyon et al. , ) by ~3.5 times. Species‐specific uses of different compatible solutes, and their environmental controls, could have many important biogeochemical and ecological consequences.…”

“…, Lyon et al. ). Plants and microorganisms in general accumulate a wide range of organic compatible solutes that can serve numerous functions in the cell, but are mainly known to act as osmolytes maintaining positive turgor pressure and stabilizing protein structure in water‐stressed environments (Yancey et al.…”

“…, Lyon et al. ). High ratios of DMSP to chl a are often associated with communities dominated by Phaeocystis spp.…”

Dimethyl sulfide dynamics in first-year sea ice melt ponds in the Canadian Arctic Archipelago

“…DMSP is a cellular metabolite found in several phytoplankton species as particulate DMSP (DMSP p ) (see the review of Green and Hatton, 2014). DMSP p plays various roles in phytoplankton, including osmoregulation (Lyon et al, 2016), cryoprotection (Karsten et al, 1996), and prevention of cellular oxidation (Sunda et al, 2002). Part of the DMSP p produced by algae is released in the water column as dissolved DMSP (DMSP d ) via several pathways reviewed in Stefels et al (2007), including active exudation, cell lysis, viral lysis, and zooplankton grazing.…”

Foreword to the special issue on ‘Biological and environmental chemistry of DMS(P) and related compounds'

“…Lyon et al [7] break the ice by exploring the physiological role of DMSP as a compatible solute in sea-ice diatoms; changes in DMSP concentrations are compared with other physiological indicators across salinity shifts representative of sea-ice formation and melt. On similar lines, Kinsey et al [8] investigate the separate and synergistic effects of iron and light on DMSP and its transformation products dimethylsulfoxide (DMSO) and acrylate in an Antarctic alga.…”