Emiliania huxleyi coccoliths in the sediment record and the relative climatic signal: examples from the Eastern Mediterranean

Emiliania huxleyi Emiliania huxleyi COCCOLITHS IN THE COCCOLITHS IN THE SEDIMENT RECORD AND THE RELATIVE SEDIMENT RECORD AND THE RELATIVE

CLIMATIC SIGNAL: EXAMPLES FROM THE CLIMATIC SIGNAL: EXAMPLES FROM THE EASTERN MEDITERRANEANEASTERN MEDITERRANEAN

Triantaphyllou M.V.1

1 University of Athens, Faculty of Geology and Geoenvironment, Dept. of Historical Geology and Paleontology, Panepistimiopolis 15784, Athens, Greece

Introduction Introduction

Emiliania huxleyi is by far the most abundant and widespread coccolithophore in the world ocean and was first identified by Lohmann (1902) using a light microscope. The coccolith complicated structure was first described by the pioneers of Scanning Electron Microscopy, distinguished three types: (A, B and C) of E. huxleyi based on heterococcolith morphology, demonstrating that the size of the different morphotypes is influenced by ecophenotypic and genotypic factors. The phylogenetic origins of E. huxleyi are documented in the fossil record. The monospecific genus Emiliania is considered to have evolved from the genus Prinsius through Toweius, Reticulofenestra and Gephyrocapsa.

Introduction Introduction Amongst the extant coccolithophores, E. huxleyi has the widest distribution dominating the living assemblages. It occasionally forms massive blooms, when water conditions are favorable, e.g. high light, limiting silicate and high carbonate saturation, and under certain environmental conditions it sheds coccoliths. The variation in E. huxleyi coccolith size and morphology is likewise frequent, being usually associated with temperature, salinity and available nutrients.

Introduction Introduction The increase in atmospheric CO2 partial pressure and the consequent changes in the seawater carbonate chemistry can cause a decrease in E. huxleyi cellular PIC/POC ratio as well as malformations of the coccoliths. Recently (Triantaphyllou et al., 2010) demonstrated the morphological variability of E. huxleyi var. huxleyi (= E. huxleyi type A) in the modern Aegean Sea, providing strong evidence for seasonal variation in E. huxleyi coccoliths.

A consistent pattern of increase in the size and calcification of coccoliths and coccospheres has been observed, including the thickness of the inner tube elements in winter/spring time low sea surface temperature and moderate productivity samples when compared with summer time high temperature–low productivity samples.

Black Sea

Greece

LevantineSea

Ionian Sea Aegean Sea

Athos

SK 4

5Skiros

Sigri

6

Evoiko s

And ros

Sou nioPoros

Rh odosM442

M940M1949

M2778

M3786M20296

M194948

Mean relative percentage of E. huxleyi in the Aegean water samples (5-120m) during the different sampling periods

E. huxleyi cell density:Jan: 34x103 cells/l, March: 23x103 cells/lAug.-Sept.: 2x103 cells/l

0

10

20

30

40

50

60

70

80

90

100

othe

r sp

ecie

s

Hol

ococ

co-

lith

opho

res

E. h

uxl

eyi

Ap ril Ma rc hJ a nua ry Aug ust Sep tem b er

%

Introduction Introduction

Triantaphyllou et al., 2010

In the central area there is evidence of heavy calcification with inner tubeelements beginning to merge and lose their individual identity, leading also to apparent fusion of the tube elements with the inner ends of the rays of the distal shield.

E. huxleyi coccospheres from low temperature (Jan.- March) water

assemblages


E. huxleyi coccospheres from high temperature (August-September) water

assemblages


Introduction Introduction The First Appearance Datum (FAD) of E. huxleyi in the geological record is used as a biostratigraphic marker and marks the base of the NN21 calcareous nannofossil biozone (NN21a, Martini, 1971). It has been dated at ~270 ka. The blooming life-style of the species started in warm periods between ~80 ka at the end of MIS 5 and 50 ka (MIS 3) (Kroon et al., 1998), associated with the E. huxleyi Acme Zone (NN21b, Martini 1971) in the fossil record.

A number of on land and marine core A number of on land and marine core sediment records are presented in the sediment records are presented in the context of this review, as examples context of this review, as examples considering NN21a and NN21b biozones, considering NN21a and NN21b biozones, including NN21a/NN21b boundary. The including NN21a/NN21b boundary. The detected detected E. huxleyi E. huxleyi assemblages, beyond assemblages, beyond their application as a unique their application as a unique biostratigraphic tool, are used to evaluate biostratigraphic tool, are used to evaluate the paleoenvironmental and paleoclimatic the paleoenvironmental and paleoclimatic conditions prevailing in the related time conditions prevailing in the related time intervals.intervals.

Scope of the studyScope of the study

Materials and MethodsMaterials and MethodsThe presented sediment records represent on land sequence at the Aravonitsa plateau, northern Peloponnese (location L11, Palyvos et al., 2009), deep sea gravity core records ADE3-23 Libyan Sea (Triantaphyllou et al., 2010b), NS-14 south-eastern Aegean Sea (Triantaphyllou et al., 2009), HCMR2-22 south Cretan margin (Ioakim et al., 2009; Katsouras et al., 2010) and long piston core record LC-08, Pantelleria Trough (Anastasakis & Pe-Piper, 2006) .

Materials and MethodsMaterials and Methods

The definition of E. huxleyi NN21a biozone is based on the presence of the first representatives of the species as the midpoint of the slope of the initial increase of the species in 300 specimens counts is defined as the interval where E. huxleyi frequency values are exceeding the 20% level (Castradori, 1993).

Specimens resembling to Reticulofenestra spp. were assigned here as EHMC (Emiliania huxleyi Moderately Calcified) morphotypes, following Crudeli et al. (2004).

Results and DiscussionResults and DiscussionON LAND RECORDSON LAND RECORDS

Species % Samples

W146A W146B

E. huxleyi 1 1small Reticulofenestra spp. 34 12Small Gephyrocapsa spp. 60 80Syracosphaera pulchra 1 1Gephyrocapsa oceanica 3 2G. protohuxleyi 3Calcidicus leptoporus 0.7 0.6Umbilicosphaera sibogae 0.3 0.4

The studied material contained abundant small Gephyrocapsa spp. including Gephyrocapsa protohuxleyi. Small coccoliths resembling to E. huxleyi, are very rarely present, nevertheless they bear platy distal shield elements in contact for much of their length and do not show any trace of hammer-heads. They have been determined as small Reticulofenestra spp. specimens which have undergone etching resulting in separation of the ends of the elements

Micropalaeontological analyses of calcareous nannoplankton in two samples from the fine-grained shallow marine deposits (location L11; Palyvos et al., 2009) in Aravonitsa plateau (westernmost part of the Corinth Gulf), yielded nannoplankton assemblages in highly diluted terrigenous material.


1-5. G. protohuxleyi

6-7. small Reticulofenestra

8-9. E. huxleyi

The lowest occurrence of E. huxleyi (at 270 ka) in the stratigraphic record of the eastern Mediterranean falls within the cold MIS8, a period of low sea-levels based on sea-level curves (e.g. Shackleton & Pisias, 1985; Sidall et al., 2003). However, during this period, the Corinth Gulf was expectedly a lake, isolated from the sea by a sill. Depending on the elevation of the sill at the time, the lowest occurrence of E. huxleyi in the Corinth Gulf is thus expected more or less close to the MIS7e highstand (i.e. a few kyr before 240 ka), because only then the sea water had the chance to enter the gulf.


Results and DiscussionResults and DiscussionMARINE CORE RECORDSMARINE CORE RECORDS


Species % Samples

LC08-3 40cm

LC08-3 50cm

LC08-3 60cm

LC08-3 70cm

LC08-3 80cm

LC08-3 95cm

LC08-3 100cm

E. huxleyi 35 29.4 5.5 7.4 3.9 2.1 6.3

G. muellerae 41.1 48.2 47.9 47.6 57.1 86.1 74.4

small Reticulofenestra spp. 11.8 5.7 38.9 39.6 31.9 8.9 16.7

Syracosphaera pulchra 3.6 6.3 1.4 2.9 2.8 2.1 0.4

Helicosphaera carteri 3.2 3.3 1.9 0.3 1.7 0.6 1.6

Calcidicus leptoporus 3.2 2.7 3.9 1.2 1.8 0.3 0.4

BIOZONE NN21b NN21a

A very clear transition from NN21a to NN21b is recorded at the lower part of the long piston core LC 08 in Pantelleria Trough, Sicily Channel. This part of the core is featured by the presence of a thick volcaniclastic interval deposited from a large gravitative flow during the Green Tuff eruption (Anastasakis & Pe-Piper, 2006). The lower hemipelagic marls, immediately below the base of the volcaniclastic interval have been examined for their nannofossil content. E. huxleyi presents abundance below 10% at the lower parts of this interval, which sharply change to prominently high numbers above 20% upwards. Age of 41190±1090 BP (Beta 198833) with a calibrated radiocarbon age of 43-47±2 ka (Anastasakis & Pe-Piper, 2006).

Results and DiscussionResults and DiscussionMARINE CORE RECORDSMARINE CORE RECORDS1.NN21a biozone, sample LC08-3-100cm, 2. E. huxleyi distal, sample LC08-3-100cm, 3. E. huxleyi distal, sample LC08-3-60cm, 4. E. huxleyi proximal, sample LC08-3-40cm, 5. G. muellerae coccosphere, sample LC08-3-60cm, 6. Helicosphaera carteri, sample LC08-3-60cm, 7-8. Coccolithus pelagicus distal and proximal, sample LC08-3-60cm, 9. H. carteri HOL (Syracolithus confusus), sample LC08-3-60cm.


1-2. E. huxleyi Acme Zone, sample 67-68 cm, 3. G. muellerae, G. muellerae Acme Zone, samples 145-146 cm, 173-174 cm, 4-8. G. muellerae Acme Zone, samples 118-119cm, 145-146 cm, 173-174cm, 9. small Reticulofenestra spp., sample 173-174 cm.

Samples from gravity core HCM2/22.

The presented sediment records reveal varied E. huxleyi assemblages in different time intervals, nevertheless strongly associated with climate variability during marine isotope stages MIS 1-8.

In particular, based on E. huxleyi assemblages:

• The lowermost part of biozone NN21a has been documented with the first representatives of the species in Aravonitsa plateau on land samples (northern Peloponnese), which are most probably placed at the warm MIS 7e at approx. 240 ka.

• The definition of NN21a/NN21b boundary is marked by an abrupt increase of E. huxleyi within relatively warm MIS 3, at 50ka, in the marine core ADE3-23 sediment record, followed by the top of the Gephyrocapsa muellerae Acme Zone (45.7 ka). The latter event has also been recognized at the lower part of one more sediment record, core HCM2/22 from the south Cretan margin

• A very clear transition from NN21a to NN21b is recorded at the lower part of the long piston core LC 08 in Pantelleria Trough, Sicily Channel. The available AMS radiocarbon age provides temporal calibration for the basal part of biozone NN21b in the eastern Mediterranean.

ConclusionsConclusions

• E. huxleyi displays values well below 20% during the cold MIS 6 and MIS 4 in the marine core ADE3-23 sediment record, although during the latter stage, values are comparably higher. It exceeds slightly 10% during the warm MIS 5.

• Further increase of E. huxleyi is recorded within warm MIS 1, whereas EHMC morphotypes are particularly present during the cold MIS 2 in the marine core ADE3-23 sediment record. The considerable fluctuations of E. huxleyi documented in the high resolution marine core NS-14 record (south-eastern Aegean Sea), reveal millennial climate variability during MIS 1 in the Late Glacial-Holocene.

ConclusionsConclusions

Technology

Emiliania huxleyi coccoliths in the sediment record and the relative climatic signal: examples from the Eastern Mediterranean