PHOTOSYNTHETIC PIGMENT AND GENETIC DIFFERENCES BETWEEN TWO SOUTHERN OCEAN MORPHOTYPES OF EMILIANIA HUXLEYI (HAPTOPHYTA)1

Abstract. The Great Calcite Belt (GCB) of the Southern Ocean is a region of elevated summertime upper ocean calcite concentration derived from coccolithophores, despite the region being known for its diatom predominance. The overlap of two major phytoplankton groups, coccolithophores and diatoms, in the dynamic frontal systems characteristic of this region provides an ideal setting to study environmental influences on the distribution of different species within these taxonomic groups. Samples for phytoplankton enumeration were collected from the upper mixed layer (30 m) during two cruises, the first to the South Atlantic sector (January–February 2011; 60° W–15° E and 36–60° S) and the second in the South Indian sector (February–March 2012; 40–120° E and 36–60° S). The species composition of coccolithophores and diatoms was examined using scanning electron microscopy at 27 stations across the Subtropical, Polar, and Subantarctic fronts. The influence of environmental parameters, such as sea surface temperature (SST), salinity, carbonate chemistry (pH, partial pressure of CO2 (pCO2), alkalinity, dissolved inorganic carbon), macronutrients (nitrate + nitrite, phosphate, silicic acid, ammonia), and mixed layer average irradiance, on species composition across the GCB was assessed statistically. Nanophytoplankton (cells 2–20 µm) were the numerically abundant size group of biomineralizing phytoplankton across the GCB, with the coccolithophore Emiliania huxleyi and diatoms Fragilariopsis nana, F. pseudonana, and Pseudo-nitzschia spp. as the most numerically dominant and widely distributed. A combination of SST, macronutrient concentrations, and pCO2 provided the best statistical descriptors of the biogeographic variability in biomineralizing species composition between stations. Emiliania huxleyi occurred in silicic acid-depleted waters between the Subantarctic Front and the Polar Front, a favorable environment for this species after spring diatom blooms remove silicic acid. Multivariate statistics identified a combination of carbonate chemistry and macronutrients, covarying with temperature, as the dominant drivers of biomineralizing nanoplankton in the GCB sector of the Southern Ocean.

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Limited variability in the phytoplankton Emiliania huxleyi since the pre-industrial era in the Subantarctic Southern Ocean

Anthropocene ◽

10.1016/j.ancene.2020.100254 ◽

2020 ◽

Vol 31 ◽

pp. 100254

Author(s):

A.S. Rigual-Hernández ◽

J.M. Sánchez-Santos ◽

R. Eriksen ◽

A.D. Moy ◽

F.J. Sierro ◽

...

Keyword(s):

Southern Ocean ◽

Emiliania Huxleyi

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Morphological variability of Emiliania huxleyi in the Indian sector of the Southern Ocean during the austral summer of 2010

Marine Micropaleontology ◽

10.1016/j.marmicro.2014.01.005 ◽

2014 ◽

Vol 107 ◽

pp. 44-58 ◽

Cited By ~ 11

Author(s):

Shramik M. Patil ◽

Rahul Mohan ◽

Suhas Shetye ◽

Sahina Gazi ◽

Syed Jafar

Keyword(s):

Southern Ocean ◽

Morphological Variability ◽

Austral Summer ◽

Emiliania Huxleyi ◽

Indian Sector

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Influence of environmental variability and Emiliania huxleyi ecotypes on alkenone-derived temperature reconstructions in the subantarctic Southern Ocean

The Science of The Total Environment ◽

10.1016/j.scitotenv.2021.152474 ◽

2021 ◽

pp. 152474

Author(s):

A.S. Rigual-Hernández ◽

F.J. Sierro ◽

J.A. Flores ◽

T.W. Trull ◽

T. Rodrigues ◽

...

Keyword(s):

Southern Ocean ◽

Environmental Variability ◽

Emiliania Huxleyi ◽

Temperature Reconstructions

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Has (anthropogenic) climate change driven subantarctic Emiliania huxleyi populations beyond their natural state?

10.5194/egusphere-egu21-9748 ◽

2021 ◽

Author(s):

Andres S. Rigual-Hernandez ◽

Francisco J. Sierro ◽

José A. Flores ◽

José M. Sánchez-Santos ◽

Ruth S. Eriksen ◽

...

Keyword(s):

Southern Ocean ◽

Environmental Change ◽

Ocean Acidification ◽

Emiliania Huxleyi ◽

Global Ocean ◽

Natural State ◽

Sedimentary Record ◽

Subtle Change ◽

Assemblage Composition ◽

Biogeographical Distribution

The global ocean acts as a climate regulator through the uptake of Earth&#8217;s excess heat and the absorption of about 30% of anthropogenic CO2 emissions since 1750. &#160;Southern Ocean waters are warming faster than the global ocean average and their low temperatures and moderate alkalinity make this region especially vulnerable to ocean acidification. Coccolithophores are a major group of calcifying phytoplankton and an important component of the Southern Ocean carbon cycle. Controlled laboratory experiments on Emiliania huxleyi (the most abundant coccolithophore) over a broad range of carbonate chemistry scenarios suggest that this taxon may be susceptible to ongoing environmental change. However, it remains uncertain whether Southern Ocean coccolithophore populations have been modified by environmental change during the industrial era. The main reason for this knowledge gap is the lack of observational data since the onset of the Industrial Revolution. In particular, continuous monitoring of key Southern Ocean ecosystems only started a few decades ago, a period insufficiently long to permit assessments of whether anthropogenic impacts on the environment have affected coccolithophore populations beyond their natural state. In order to overcome this limitation, here we take advantage of the preservation capacity of coccolithophores in the sedimentary record to provide a benchmark of their pre-industrial state. We compare the morphotype assemblage composition and morphometric parameters in coccoliths of E. huxleyi from a suite of Holocene-aged sediments south of Tasmania with annual sediment trap records retrieved at the Southern Ocean Time Series observatory in the Australian sector of the Subantarctic Zone. Our results suggest that carbonate dissolution in the sediments reduced the coccolith mass and length of the coccoliths but, coccolith thickness appeared to be decoupled from dissolution. The biogeographical distribution of coccolith thickness in subtropical and subantarctic sediments mirrored the distribution of E. huxleyi morphotypes, highlighting the important role of E. huxleyi assemblage composition on the control of coccolith morphometrics. Moreover, comparison of coccolith assemblages from the sedimentary record with those collected from subantarctic sediment traps indicates that modern E. huxleyi coccoliths are about 2% thinner than those from the pre-industrial Holocene. The subtle change in coccolith thickness is in stark contrast with previous work that documented a dramatic reduction in shell calcification in the planktonic foraminifera Globigerina bulloides that resulted in a shell-weight decrease of 30-35%, most likely induced by ocean acidification. Overall, our results underscore the variable sensitivity of different marine calcifying plankton groups to ongoing environmental change in the Southern Ocean.

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The Influence of Environmental Variability on the Biogeography of Coccolithophores and Diatoms in the Great Calcite Belt

10.5194/bg-2017-110 ◽

2017 ◽

Cited By ~ 2

Author(s):

Helen E. K. Smith ◽

Alex J. Poulton ◽

Rebecca Garley ◽

Jason Hopkins ◽

Laura C. Lubelczyk ◽

...

Keyword(s):

Species Composition ◽

Southern Ocean ◽

Silicic Acid ◽

Dissolved Inorganic Carbon ◽

Emiliania Huxleyi ◽

Nutrient Concentrations ◽

The South ◽

Carbonate Chemistry ◽

Atlantic Sector ◽

South Indian

Abstract. The Great Calcite Belt (GCB) of the Southern Ocean is a region of elevated summertime upper ocean calcite concentration derived from coccolithophores, despite the region being known for its diatom predominance. The overlap of two major phytoplankton groups, coccolithophores and diatoms, in the dynamic frontal systems characteristic of this region, provides an ideal setting to study environmental influences on the distribution of different species within these taxonomic groups. Water samples for phytoplankton enumeration were collected from the upper 30 m during two cruises, the first to the South Atlantic sector (Jan–Feb 2011; 60 °W–15 °E and 36–60 °S) and the second in the South Indian sector (Feb–Mar 2012; 40–120 °E and 36–60 °S). The species composition of coccolithophores and diatoms was examined using scanning electron microscopy at 27 stations across the Sub-Tropical, Polar, and Sub-Antarctic Fronts. The influence of environmental parameters, such as sea-surface temperature (SST), salinity, carbonate chemistry (i.e., pH, partial pressure of CO2 (pCO2), alkalinity, dissolved inorganic carbon), macro-nutrients (i.e., nitrate &plus; nitrite, phosphate, silicic acid, ammonia), and mixed layer average irradiance, on species composition across the GCB, was assessed statistically. Nanophytoplankton (cells 2–20 μm) were the numerically abundant size group of biomineralizing phytoplankton across the GCB, the coccolithophore Emiliania huxleyi and the diatoms Fragilariopsis nana, F. pseudonana and Pseudonitzschia sp. were the most dominant and widely distributed species. A combination of SST, macro-nutrient concentrations and pCO2 were the best statistical descriptors of biogeographic variability of biomineralizing species composition between stations. Emiliania huxleyi occurred in the silicic acid-depleted waters between the Sub-Antarctic Front and the Polar Front, indicating a favorable environment for this coccolithophore in the GCB after spring diatom blooms remove silicic acid to limiting levels. After full consideration of variability in carbonate chemistry and temperature on the distribution of nanoplankton in the GCB, we find that temperature remains the dominant driver of biogeography in a large proportion of the modern Southern Ocean.

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