Population dynamics of modern planktonic foraminifera in the western Barents Sea

Abstract

<p><strong>Abstract.</strong> This study reports on species diversity and distribution of planktonic foraminifera (PF) at the Barents Sea Opening (BSO). PF populations living in late summer (collected by mean of stratified plankton tows) and recently settled individuals (sampled by interface corer) were studied and compared. High abundances reaching up to 400 ind.m<sup>−3</sup> in tow samples and 8000 ind.cm<sup>−3</sup> in surface sediments were recorded in the centre of the studied area while low abundances were observed in coastal areas, likely hampered by continental influences. The living and subfossil (i.e. core-top) assemblages are mainly composed of the four same species <i>Neogloboquadrina pachyderma</i>, <i>Neogloboquadrina incompta</i>, <i>Turborotalita quinqueloba</i> and <i>Globigerinita uvula</i>. The two species <i>G. uvula</i> and <i>T. quinqueloba</i> largely dominate the upper water column whereas surface sediment assemblages display especially high concentrations of <i>N. pachyderma</i>. The unusual dominance of <i>G. uvula</i> in the water sample assemblages compared to its low occurrence in surface sediments might be the signature of (1) a seasonal signal due to summer phytoplankton composition changes at the BSO, linked to the increase of summer temperature at the study site, and/or (2) a signal of a larger time-scale and wide geographical reach phenomenon inducing poleward temperate/subpolar species migration and consecutive foraminiferal assemblage diversification at high latitudes under global climate forcing. Protein concentrations were measured on single specimens and used as a proxy of individual carbon biomass. Specimens of all species show the same trend, i.e. a northward decrease of their size-normalized-protein concentration suggesting foraminiferal biomass to be potentially controlled by different constituents of their organelles (e.g. lipids). The originality of coupling data from plankton tows, protein measurements and surface sediments allows us to hypothesise that PF dynamics (seasonality and distribution) is decoupled from their metabolism.</p>

Planktonic foraminifera eDNA signature deposited on the seafloor remains preserved after burial in marine sediments

“…Therefore, we retain the possibility that the high abundance of this species in surface metabarcoding datasets reflects a genuine signal. Indeed, it has been shown that the ongoing climate warming induces large latitudinal shifts in planktonic foraminifera communities globally 40 , and higher abundance of G. uvula in recent plankton samples from the North Atlantic has been noted by two independent studies 41,42 . We speculate that a potential recent increase of G. uvula in the studied region due to ongoing global change could in theory indeed be first observed in the eDNA on the sea floor.…”