Use of Stress Signals of Their Attached Bacteria to Monitor Sympagic Algae Preservation in Canadian Arctic Sediments

Abstract

Based on the strong aggregation of sympagic (ice-associated) algae and the high mortality or inactivity of bacteria attached to them, it was previously hypothesized that sympagic algae should be significant contributors to the export of carbon to Arctic sediments. In the present work, the lipid content of 30 sediment samples collected in the Canadian Arctic was investigated to test this hypothesis. The detection of high proportions of trans vaccenic fatty acid (resulting from cis-trans isomerase (CTI) activity of bacteria under hypersaline conditions) and 10S-hydroxyhexadec-8(trans)-enoic acid (resulting from 10S-DOX bacterial detoxification activity in the presence of deleterious free palmitoleic acid) confirmed: (i) the strong contribution of sympagic material to some Arctic sediments, and (ii) the impaired physiological status of its associated bacterial communities. Unlike terrestrial material, sympagic algae that had escaped zooplanktonic grazing appeared relatively preserved from biotic degradation in Arctic sediments. The expected reduction in sea ice cover resulting from global warming should cause a shift in the relative contributions of ice-associated vs. pelagic algae to the seafloor, and thus to a strong modification of the carbon cycle.

Environmental micro‐niche filtering shapes bacterial pioneer communities during primary colonization of a Himalayas' glacier forefield

“…IPL analysis deepens the knowledge of the resident microbiomes by providing information that helps in clarifying the adaptation and diversity of the entire community (Sturt et al, 2004 ). The presence in the study area of oxidized phosphatidyl choline, betaine and ornithine lipids having one to multiple hydroxylations and oxylipins indicates that microorganisms have to cope with high oxidative and photo‐oxidative stress, associated with low temperature and high irradiation (Amiraux, 2017 ). Furthermore, the predominant fatty acids had monounsaturated chains, a molecular component of the biochemical strategy used by psychrophiles to maintain cell membrane integrity in low‐temperature environments (Collins & Margesin, 2019 ).…”

Cellular Damage of Bacteria Attached to Senescent Phytoplankton Cells as a Result of the Transfer of Photochemically Produced Singlet Oxygen: A Review

“…However, the amount and composition of OM preserved in marine sediments varies greatly between different regions and depositional environments [ 118 , 119 ]. Indeed, organic carbon preservation is mediated by several parameters, including: (i) oxygen concentration [ 120 ], (ii) sedimentation rate [ 121 ], (iii) protection through interactions with a mineral matrix (mainly clays and iron oxides) [ 119 , 122 ], (iv) physiological status of the bacterial communities associated with sinking particles [ 59 ], and (v) match or mismatch of zooplanktonic grazing with algae fluxes [ 123 ].…”

“…In the Arctic, sympagic algae are assumed to be one of the main sources of organic matter reaching the seafloor [ 59 , 124 , 125 ], as they strongly aggregate (due to the high concentrations of EPS produced by these organisms in the ice) and, thus, sink faster than pelagic algae [ 126 ]. Moreover, the bacteria associated with them are in a weak physiological state and, thus, have only weak mineralization capabilities [ 59 , 123 ]. Indeed, in ice, these bacterial communities are strongly altered by: (i) intense osmotic stress induced by salinity changes in brine channels during the early stages of ice melt [ 59 ], (ii) production of bactericidal FFA and hydroperoxides by sympagic algae in response to light stress [ 112 , 123 ], and (iii) intense transfer of 1 O 2 from sympagic algae [ 41 ] (also see Section 5 ).…”

“…Moreover, the bacteria associated with them are in a weak physiological state and, thus, have only weak mineralization capabilities [ 59 , 123 ]. Indeed, in ice, these bacterial communities are strongly altered by: (i) intense osmotic stress induced by salinity changes in brine channels during the early stages of ice melt [ 59 ], (ii) production of bactericidal FFA and hydroperoxides by sympagic algae in response to light stress [ 112 , 123 ], and (iii) intense transfer of 1 O 2 from sympagic algae [ 41 ] (also see Section 5 ). We recently examined the lipid content of surficial sediments (0–1 cm) and sinking particles collected in summer from central and eastern Baffin Bay during the 2016 GreenEdge campaign [ 112 ].…”

“…Due to the effects of global warming (reducing the extent and duration of sea ice), we are currently witnessing a decline in the contribution of sympagic algae to primary production. Unfortunately, as these algae are assumed to be one of the main sources of OM reaching the seafloor [ 59 , 61 , 123 , 124 ], the biological pump may act as a positive feedback loop for global warming.…”