Distribution of calcifying and silicifying phytoplankton in relation to environmental and biogeochemical parameters during the late stages of the 2005 North East Atlantic Spring Bloom

Abstract

Abstract. The late stage of the North East Atlantic (NEA) spring bloom was investigated during June 2005 along a transect section from 45 to 66 • N between 15 and 20 • W in order to characterize the contribution of siliceous and calcareous phytoplankton groups and describe their distribution in relation to environmental factors. We measured several biogeochemical parameters such as nutrients, surface trace metals, algal pigments, biogenic silica (BSi), particulate inorganic carbon (PIC) or calcium carbonate, particulate organic carbon, nitrogen and phosphorus (POC, PON and POP, respectively), as well as transparent exopolymer particlesCorrespondence to: K. Leblanc (karine.leblanc@univmed.fr) (TEP). Results were compared with other studies undertaken in this area since the JGOFS NABE program. Characteristics of the spring bloom generally agreed well with the accepted scenario for the development of the autotrophic community. The NEA seasonal diatom bloom was in the late stages when we sampled the area and diatoms were constrained to the northern part of our transect, over the Icelandic Basin (IB) and Icelandic Shelf (IS). Coccolithophores dominated the phytoplankton community, with a large distribution over the Rockall-Hatton Plateau (RHP) and IB. The Porcupine Abyssal Plain (PAP) region at the southern end of our transect was the region with the lowest biomass, as demonstrated by very low Chla concentrations and a community dominated by picophytoplankton. Early depletion Published by Copernicus Publications on behalf of the European Geosciences Union. 2156 K. Leblanc et al.: Distribution of calcifying and silicifying phytoplankton of dissolved silicic acid (DSi) and increased stratification of the surface layer most likely triggered the end of the diatom bloom, leading to coccolithophore dominance. The chronic Si deficiency observed in the NEA could be linked to moderate Fe limitation, which increases the efficiency of the Si pump. TEP closely mirrored the distribution of both biogenic silica at depth and prymnesiophytes in the surface layer suggesting the sedimentation of the diatom bloom in the form of aggregates, but the relative contribution of diatoms and coccolithophores to carbon export in this area still needs to be resolved.

Role of mesoscale eddies on the variability of biogenic flux in the northern and central Bay of Bengal

“…[23] Introduction of nitrate and silicate during cyclonic eddy events, favor the formation of large (2-200 mm) diatom [Hasle and Syvertsen, 1997] and subsequent blooms. With the depletion of dissolved silicic acid and increased stratification of the surface layer most likely triggers the crash of the diatom bloom, and subsequently leads to cocolithophore dominance [LeBlanc et al, 2009]. Prasanna reported the higher concentrations of silicate (2mM) compared to nitrate (0.5mM) during the cyclonic eddy period in the surface waters and also observed doming of nitrate and silicate isopleths from 50 m to 10 m depth.…”

The Role of B Vitamins in Marine Biogeochemistry

“…Historically, major efforts have been dedicated to elucidating the mechanisms that trigger phytoplankton blooms and lead to temporal and spatial phytoplankton species successions in the ocean (Leblanc et al 2009, Mahadevan et al 2012. Although those studies have shown that a combination of ambient physical and chemical conditions could favor the predominance of certain algae at specific times and/or locations, they have also shown that, with the exception of iron requirements (Boyd et al 2000), nutritional requirements are similar across all algae (Redfield 1958).…”

Chlorophyll-a transformations associated with sinking diatoms during termination of a North Atlantic spring bloom

“…Rather, the particular transformation products produced appears to depend on the species of phytoplankton (Bale et al, 2011;Hallegraeff, 1981;Jeffrey and Hallegraeff, 1987;Louda et al, 1998Louda et al, , 2002Owens and Falkowski, 1982), the physiochemical environment (Louda et al, 1998(Louda et al, , 2002Yacobi et al, 2001), and, in the case of grazing, on the species of grazer and on whether the grazing is primary or secondary (coprophagy) (Burkill et al, 1987;Gieskes et al, 1991;Goericke et al, 2000;Hallegraeff, 1981). Furthermore, North Atlantic spring diatom blooms are often thought to be terminated by silicic acid limitation (Henson et al, 2006;Leblanc et al, 2009;Savidge et al, 1995), with major export of phytodetrital aggregates taking place upon bloom termination (Billett et al, 1983). However, while many studies have attributed certain chl-a transformation products to terms such as 'cell stress', 'senescence' and 'death', transformation products associated with potentially nutrient-depleted phytodetrital aggregates have not been studied.…”