Phytoplankton chlorophyll &lt;i&gt;a&lt;/i&gt; biomass, composition, and productivity along a temperature and stratification gradient in the northeast Atlantic Ocean

Abstract. Relationships between sea surface temperature (SST, > 10 m) and vertical density stratification, nutrient concentrations, and phytoplankton biomass, composition, and chlorophyll a (Chl a) specific absorption were assessed in spring and summer from latitudes 29 to 63° N in the northeast Atlantic Ocean. The goal of this study was to identify relationships between phytoplankton and abiotic factors in an existing SST and stratification gradient. Furthermore, a bio-optical model was used to estimate productivity for five phytoplankton groups. Nutrient concentration (integrated from 0 to 125 m) was inversely correlated with SST in spring and summer. SST was also inversely correlated with near-surface (0–50 m) Chl a and productivity for stratified stations. Near-surface Chl a and productivity showed exponential relationships with SST. Chl a specific absorption and excess light experiments indicated photoacclimation to lower irradiance in spring as compared to summer. In addition, Chl a specific absorption suggested that phytoplankton size decreased in summer. The contribution of cyanobacteria to water column productivity of stratified stations correlated positively with SST and inversely with nutrient concentration. This suggests that a rise in SST (over a 13–23 °C range) stimulates productivity by cyanobacteria at the expense of haptophytes, which showed an inverse relationship to SST. At higher latitudes, where rising SST may prolong the stratified season, haptophyte productivity may expand at the expense of diatom productivity. Depth-integrated Chl a (0–410 m) was greatest in the spring at higher latitudes, where stratification in the upper 200 m was weakest. This suggests that stronger stratification does not necessarily result in higher phytoplankton biomass standing stock in this region.

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Phytoplankton biomass, composition, and productivity along a temperature and stratification gradient in the Northeast Atlantic Ocean

Biogeosciences Discussions ◽

10.5194/bgd-10-1793-2013 ◽

2013 ◽

Vol 10 (1) ◽

pp. 1793-1829 ◽

Cited By ~ 1

Author(s):

W. H. van de Poll ◽

G. Kulk ◽

K. R. Timmermans ◽

C. P. D. Brussaard ◽

H. J. van der Woerd ◽

...

Keyword(s):

Atlantic Ocean ◽

Phytoplankton Biomass ◽

Nutrient Concentration ◽

North Atlantic Ocean ◽

Standing Stock ◽

Biomass Composition ◽

Nutrient Concentrations ◽

Exponential Relationship ◽

Near Surface ◽

Chl A

Abstract. The North Atlantic Ocean experiences considerable variability in sea surface temperature (SST, >10 m) on seasonal and inter-annual time-scales. Relationships between SST and vertical density stratification, nutrient concentrations, and phytoplankton biomass, composition, and absorption were assessed in spring and summer from latitudes 30–62° N. Furthermore, a bio-optical model was used to estimate productivity for five phytoplankton groups. Nutrient concentration (integrated from 0–125 m) was inversely correlated with SST in spring and summer. SST was also inversely correlated with near surface (0–50 m) Chl a and productivity for stratified stations. However, near surface Chl a showed an exponential relationship with SST, whereas a linear relationship was found for productivity and SST. The response of phytoplankton to changes in SST is therefore most likely to be observed by changes in Chl a rather than productivity. The discrepancy between relationships of Chl a and productivity were probably related to changes in phytoplankton cell size. The contribution of cyanobacteria to water column productivity correlated positively with SST and inversely with nutrient concentration. This suggests that a rise in SST (over a 13–23 °C range) stimulates productivity by cyanobacteria at the expense of haptophytes, which showed an inverse relationship to SST. At higher latitudes, where rising SST may prolong the stratified season, haptophyte productivity may expand at the expense of diatom productivity. Depth integrated Chl a (0–410 m) was greatest in the spring at higher latitudes, where stratification in the upper 200 m was weakest. This suggests that stronger stratification does not necessarily result in higher phytoplankton biomass standing stock in this region.

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Late-summer distribution of phytoplankton in relation to water mass characteristics in Hudson Bay and Hudson Strait (Canada)

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f97-099 ◽

1997 ◽

Vol 54 (8) ◽

pp. 1937-1952 ◽

Cited By ~ 31

Author(s):

M Harvey ◽

J -C Therriault ◽

N Simard

Keyword(s):

Phytoplankton Biomass ◽

Water Mass ◽

Environmental Gradients ◽

Late Summer ◽

Tidal Mixing ◽

Nutrient Concentrations ◽

Hudson Bay ◽

Phytoplankton Assemblage ◽

Near Surface ◽

Chl A

Descriptive and multivariate analytical methods were used to analyze the early September (1993) abundance and species composition of phytoplankton in relation to water mass characteristics in Hudson Bay and Hudson Strait. Four groups of stations distributed along well-defined environmental gradients characterizing the distribution of physical and chemical variables were identified. The first group, located in the most southern region of Hudson Bay, was strongly influenced by freshwater runoffs from James Bay and from the other major rivers around the bay and was characterized by a relatively high phytoplankton biomass (chlorophyll a (Chl a) > 1.0 µg ·L-1) in the near-surface waters and by a phytoplankton assemblage equally dominated by small flagellates and dinoflagellates. The second group, located in an area northwest of the Belcher and Sleeper islands, was characterized by relatively well-mixed conditions where small diatoms composed about 50% of the phytoplankton assemblage. The third group occupied the upper part of the bay and the entrance of the strait and was characterized by the lowest surface nutrient concentrations encountered. A clear subsurface chlorophyll maximum dominated by small flagellates (>55% of the assemblage) was observed in this region. The fourth group was located in the central part of the strait where the highest surface nutrient concentrations and phytoplankton biomass values (Chl a > 2.0 µg ·L-1) were observed. The phytoplankton assemblage there was clearly dominated by small diatoms (>80%). These conditions are related to the presence of more intense tidal mixing in this region. The phytoplankton standing crop within this area was comparable with that observed during an autumn bloom situation in most temperate regions of the world's ocean.

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Validation of Stratification-Driven Phytoplankton Biomass and Nutrient Concentrations in the Northeast Atlantic Ocean as Simulated by EC-Earth

Geosciences ◽

10.3390/geosciences9100450 ◽

2019 ◽

Vol 9 (10) ◽

pp. 450 ◽

Cited By ~ 1

Author(s):

Nomikos Skyllas ◽

Richard Bintanja ◽

Anita G. J. Buma ◽

Corina P. D. Brussaard ◽

Matthias Gröger ◽

...

Keyword(s):

Atlantic Ocean ◽

North Atlantic ◽

Vertical Mixing ◽

Greenland Ice Sheet ◽

Nutrient Concentrations ◽

Mixing Processes ◽

Phytoplankton Productivity ◽

Northeast Atlantic ◽

Northeast Atlantic Ocean ◽

Seasonal Stratification

We validated simulations of the Earth system model (ESM) EC-Earth-NEMO of present-day temperature, salinity, nutrient, and chlorophyll a profiles with in situ observations in the Northeast Atlantic Ocean (29–63º N). Simulations with standard parametrization (run 1) and improved parametrization of vertical mixing (run 2) were compared. Run 1 showed shallower mixed layer depths (MLDs) in spring as compared to observations owing to lower salinities in the upper 200 m of the subpolar North Atlantic (>55º N). This coincided with a mismatch with observed timing and magnitude of the phytoplankton spring bloom. In contrast, the model performed well south of 55º N. Run 2 showed improved springtime MLD, phytoplankton dynamics, and nutrient distributions in the subpolar North Atlantic. Our study underlines the sensitivity of subpolar North Atlantic phytoplankton blooms to surface freshening, suggesting that future fresh-water inflow from Arctic and Greenland Ice sheet melting could significantly affect phytoplankton productivity. These findings contribute to the generic validation of the EC-Earth ESM and underline the need for rigorous validation of physics-biology links, in particular the sub polar North Atlantic where complex seasonal stratification/vertical mixing processes govern upper ocean phytoplankton productivity.

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