Holocene Diatoms Recovered in the Firth of Tay, Antarctic Peninsula (Sites NBP0602A-8 and NBP0703-02JPC) Susan Murr Foley

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2010 Holocene Diatoms Recovered in the Firth of Tay, Antarctic Peninsula (Sites NBP0602A-8 and NBP0703-02JPC) Susan Murr Foley

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HOLOCENE DIATOMS RECOVERED IN

THE FIRTH OF TAY,

ANTARCTIC PENINSULA

(Sites NBP0602A-8 and NBP0703-02JPC)

SUSAN MURR FOLEY

A Thesis presented to the Department of Geology in partial fulfillment of the requirements for the degree of Master of Science

Degree Awarded: Spring Semester, 2010

The members of the committee approve the thesis of Susan M. Foley defended on May 3, 2010.

______Sherwood W. Wise Professor Directing Thesis

______Anthony J. Arnold Committee Member

______Joseph F. Donoghue Committee Member

Approved:

______Lynn Dudley, Chair, Department of Geological Sciences

The Graduate School has verified and approved the above-named committee members.

ii TABLE OF CONTENTS

List of Tables ...... iv List of Figures ...... v Abstract ...... vi

INTRODUCTION ...... 1 OBJECTIVES ...... 5 STUDY AREA ...... 6 LITHOSTRATIGRAPHY ...... 7 PREVIOUS WORK ...... 9 METHODS AND MATERIALS ...... 10 RESULTS ...... 14 DISCUSSION ...... 16 CONCLUSION ...... 20 APPENDIX ...... 21 TABLES ...... 22 FIGURES ...... 30 PLATES ...... 45 REFERENCES ...... 51 BIOGRAPHICAL SKETCH ...... 54

iii LIST OF TABLES

I. Species abundance ...... 22 II. Chaetoceros spp. abundance, (T) Total diatom abundance/g sediment ...... 26 III. Radiocarbon age data ...... 28 IV. Shannon Wiener Index values ...... 29

iv LIST OF FIGURES

1. Map of study area ...... 30 2. Map of Antarctic Peninsula and site locations ...... 31 3. Seismic profile of core site NBP0602A-8B ...... 32 4. Bathymetric survey of study area ...... 33 5. Lithologic description sheet for core NBP0602A-8B ...... 34 6. Lithologic description sheet for core NBP0602A-8C ...... 35 7. Lithologic description sheet for core NBP0703 JPC-02 ...... 36 8. Down-core diatom data including “T” values, density, Chaetoceros spp. abundance, and diversity ...... 37 9. Shannon Wiener index values versus depth graph ...... 38 10. Relative diatom abundance (%) ...... 39 11. Subpolar proxy signal, climatic events, and radiocarbon age versus depth curve ...... 42 12. Map of Bransfield Basin and different surface water masses, the Bellinghausen Sea current, the Weddell Sea Gyre and the Antarctic Circumpolar Current (ACC) ...... 43 13. Map of Antarctica and the surrounding water masses ...... 44

v ABSTRACT

A greatly expanded section of Holocene sediment was recovered at Site NBP0602-8 in the Firth of Tay near the tip of the West Antarctic Peninsula during the SHALDRIL II cruise aboard the R/V Nathaniel B. Palmer, 2006. Recovery in the four holes at this site was ~85%, with the exception of the uppermost eight meters of water saturated sediments. The next year the site was revisited during Cruise NBP0703 and a jumbo piston core (JPC 02) recovered sediment to 23 meters below seafloor to fill missing gaps in the upper section. Fossil diatoms have been proven to be highly useful in paleontological climate reconstruction. Therefore, this investigation is a down-core quantitative study of diatom assemblages from this Firth of Tay sequence to identify and constrain changes in paleoenvironmental events. The project provides evidence of an early deglaciation episode, the Mid-Holocene Climatic Optimum, and subsequent cooling and Neoglacial conditions that persist until the present. The Mid-Holocene Climatic Optimum delineated in this study correlates closely with the timing and duration of this event in Maxwell Bay, to the north. The same event is recorded in Palmer Deep on the opposite (west) side of the Antarctic Peninsula but with an earlier onset and longer duration. The Climatic Optimum recorded at the Firth of Tay is less pronounced than at the other two sites, however, due to the colder water stemming from the Weddell Sea Gyre.

vi INTRODUCTION

In an extensive review of “Antarctic Climate Change and the Environment”, the Scientific Committee on Antarctic Research (SCAR) noted that following the early Holocene deglaciation the Mid-Holocene Climatic Optimum (sometimes referred to as the “Hypsithermal”) is present in many ice, lake, and coastal marine records from around the continent but that marine and climate anomalies are “apparently out of phase” (Turner et al. 2009). They go on to say that “there is an urgent need for well-dated, high resolution climate records in coastal Antarctica and in … particular regions of the Antarctic Peninsula to fully understand these regional climate anomalies.” Here I report on a new record from the Weddell Sea side of the Antarctic Peninsula. The primary tool I will use to interpret paleoclimate, in particular the presence/absence of the Mid- Holocene Climatic Optimum, is the fossil marine diatom assemblages. The hypothesis to be tested is whether or not this climate optimum can be detected at this site, and why or why not. Holocene Diatom Assemblages Diatoms (division Chrysophyta, class Bacillariophyceae) are autotrophic, single-celled, golden-brown algae that are widely distributed in the photic zones of virtually all aqueous and semi-aqueous environments. The cell is enclosed in an external mineralized skeleton or frustule made largely of opaline silica (SiO2.nH2O) with an upper valve, the epitheca and its associated girdle elements (cingulum) fitting tightly a lower valve, the hypotheca and its associated elements, similar to the design of a Petri Dish. In the Southern Ocean, diatoms dominate the phytoplankton community as the top primary producers and form the basis of various marine food webs. They are divided into two orders, the Centrales and the Pennales, on the basis of the shape and symmetry of their valve in plan view. They are further classified by their surface ornamentation of pores and pore patterns, grooves, spines, tubes, processes (Round et al. 1990). Of particular geologic significance to Antarctic research, the diatom opaline silica frustule is fairly resistant to diagenic processes within the sediment and can provide a reliable record of past environmental conditions. Diatoms are very diverse in the Southern Ocean and exhibit habitat preferences from dwelling within or underneath sea-ice to warmer open-water settings (Leventer and Dunbar 1998). Also, bloom events and spore abundances suggest seasonality or shifts in climate conditions (Krebs 1983). As relative latecomers to the paleontologic record with their

1 first known appearance in the Jurassic, fossil diatoms provide a valuable tool for biostratigraphic correlation and relative age dating of sediments. In this study I conducted a quantitative diatom census on three Holocene sequences taken at one locality in the Firth of Tay, northern Antarctic Peninsula (Figs. 1, 2), from the three core suites (NBP0602A-8B, -8C, and NBP0703-JPC02). Next, with the aid of complementary 14C age dates published by Michalchuk et al. (2009), I constructed a composite section based on their calibrated radiocarbon ages. With this initial information, plus additional calculations, including relative and absolute abundances, density, a diversity index, and proxy indicators, I will present a paleoclimate reconstruction of the study area with evidence for the Mid-Holocene Climatic Optimum. Taxa as Paleoclimate Proxies The combined down-core assemblage is comprised of extant diatoms with open- water and/or sea-ice affinities. Abundances of particular species or generic groups serve as proxies or indicators for paleoclimate reconstruction. All taxa referred to in the text are illustrated in Plates I-VI (pages 39-45). Chaetoceros spp. rs (resting spores) All samples examined from are dominated by Chaetoceros spp. resting spores (rs) associated with increased upper water-column stability and spring diatom blooms of high primary productivity. The stabilization results during periods of warmer temperatures and decreases in wind velocities and salinity (Sjunneskog and Taylor 2002; Leventer et al., 2002). Spore induction follows the bloom cycle with the advent of unfavorable growth conditions, including nutrient-limiting and temperature stress. Generally, Chaetoceros spp. rs peaks trail periods of elevated total diatom abundance. Eucampia Antarctica Eucampia antarctica forms curved or straight colonial chains, with different valve morphologies, and has been established as a valuable proxy for paleoclimate reconstruction (Leventer 2002). The straight colonial chain form, E. antarctica var. recta, with symmetric valve symmetry, has sea-ice and polar affinity. The curved, chain form, E. antarctica var. antarctica, with asymmetric valve symmetry has subpolar, open water affinity (Leventer et al. 2002). The terminal valves are affixed at both ends of the chain. Longer chains form in warmer conditions, and typically a lower ratio of terminal to intercalary valves is observed (Fryxell and Prasad

2 1990). Whitehead et al. (2005) document the utility of a ratio of intercalary and terminal valves, the Eucampia Index, as a climate proxy indicator. Unfortunately, the paucity of the individuals of this genus present in the samples evaluated for this study prevented the calculation of this index. Sea-Ice (polar) and Open Water (subpolar) Proxies Taxa of the polar floral community include Thalassiosira antarctica, Fragilariopsis curta, F. cylindrus, Eucampia antarctica var. recta (polar), and Cocconeis spp. Thalassiosira Antarctica, the second most dominant taxon in this study, is associated with platlet ice communities (Cunningham et al. 1999). Fragilariopsis curta has an affinity for very cold sea-surface temperatures and usually flourishes within the sea ice and at the sea-ice edge (Fryxell, 1989; Leventer and Dunbar, 1998; Cunningham et al., 1999). Fragilariopsis cylindrus also exhibits preference for sea-ice and melting-ice conditions (Garrison et al. 1987; Leventer et al. 1993). Cocconeis spp., a benthic genus, utilizes sea ice as a substrate and is typically found in fast-ice samples (Scott et al. 1994). Taxa of the warmer, open-water community include Fragilariopsis kerguelensis, Thalassiosira lentiginosa, Fragilariopsis rhombica, Fragilariopsis clementia, and Eucampia antarctica var. antarctica. Fragilariopsis kerguelensis is a dominant species in the subpolar waters of the Antarctic Circumpolar Current and is established as a valuable indicator for open marine deposition (Crosta et al. 2005). Thalassiosira lentiginosa is widespread in Antarctic waters but is more prevalent in warmer, ice-free conditions. Fragilariopsis rhombica is not a dominant species but is also associated with subpolar assemblages (Zielinski and Gersonde 1997). Of interest, Fragilariopsis clementia is typically not described as a sea-ice flora, but is present in a few samples in the lower section of the core (Zielinski and Gersonde 2002). As discussed above, the Eucampia antarcitca var. antarctica, with the asymmetric intercalary valve morphology, is a well-documented subpolar taxon.

SHALDRIL II Cruise Summary The RV/IB Nathaniel B. Palmer departed Punta Arenas, Chile on March 1, 2006, on a demonstration cruise to test a medium-size drill rig at sites in the northern Antarctic Peninsula

3 considered to have the thickest and most continuous Neogene sections known to date along the Antarctic margins (Anderson 1999). Operations at the first two Sites NBP0602A-1 and -2 were hindered by large, thick floes of multiyear sea ice. The ship could not hold station long enough to drill through the glacial overburden and reach the targeted material. Faced with extreme, unprecedented multiyear sea ice drifting rates, the decision was made to abandon, at least temporarily, the originally proposed sites and, except for the Firth of Tay Holocene, to drill instead back-up or newly-defined stratigraphic targets. At the first two Sites (NBP0602A-3 and -4) in the Firth of Tay, upper Eocene/lower Oligocene strata was cored, but operations had to be terminated due to the sea-ice conditions. The next two Sites, NBP0602A-5 and -6, located in a thick stratigraphic wedge on the southern margin of the Joinville Plateau, yielded middle Miocene muddy sands and Pliocene sands. Operations at Site -7 were halted due to a failure of the drill string apparatus. At the Firth of Tay Site, NBP0602A-8 (March 21 and 22) the ship held station in extremely strong winds to recover of a long 79-m sequence of presumed Holocene sediment. The following day, an attempt was made to return once more to the original proposed sites in hopes of locating open water. Unfortunately, at the two Sites, NBP0602A-9, and -10 unfavorable sea-ice conditions prevailed, and the sites were abandoned. The objectives of Site NBP0602A-11 were technical in nature, testing the penetration rate and core recovery of sedimentary rock in high-wind conditions. The ship returned to port to complete the 36-day voyage on 5 April, 2006 (Anderson et al. 2006).

4 OBJECTIVES

The objectives of this investigation are to: (1) Conduct a quantitative down-core diatom census; (2) Generate additional data, including relative and absolute abundances, and a diversity index; (3) Employ the use of proxy indicators to infer paleoclimate trends; (4) Establish the presence/absence of the Mid-Holocene Climatic Optimum Event, (5) Compare the Firth of Tay results to previous studies in Maxwell Bay (Milliken et al. 2010; Geary 2008) and Palmer Deep (Sjunneskog and Taylor 2002).

5 STUDY AREA

The samples for this study were cored in the Firth of Tay, situated on the tip of the Antarctic Peninsula (AP) in the extreme northwestern sector of the Weddell Sea between Dundee and Joinville Islands (Figs 1 and 2). Constituting one of the four discrete crustal blocks of West Antarctica (Anderson, 1999), the AP (~1250 km long, ~250 km wide, and average elevation of ~2 km) extends much further north than the rest of the continent and creates a topographic barrier, interrupting the lower atmospheric and oceanic circulations. Temperatures are milder on the northern tip of the AP, but gale force winds and severe snow storms can persist for days to weeks in duration. In contrast to the warmer, more open-water conditions on the western side of the AP, the study site is located on the colder, eastern tip of the AP, influenced by the continental winds and the cold, highly saline Weddell Sea conditions (Domack et al. 2003). The bay area has an average temperature of - 5˚C and an average precipitation rate of 200-500 mm/year (Michalchuk et al. 2009; Van Lipzig et al. 2004). During a 1991 Polar Duke cruise several air-gun seismic lines were gathered in the Firth of Tay vicinity. The profiles generated within and in the mouth of the bay indicate a thick (~50m), laminated sediment sequence overlying bedrock (Fig. 3). As part of the 2006 SHALDRIL II initiative, the site was revisited on 21 and 22 March and detailed seismic and bathymetric surveys of the bay indicated several small minibasins (Figs. 4). A site in ice-free waters containing the thickest sediment package was selected for the drill target (Anderson et al. 2006; Michalchuk et al. 2009).

6 LITHOSTRATIGRAPHY

NBP0602A Site 8 Two Kasten cores and two drill-core sequences were recovered in the Firth of Tay during SHALDRIL Cruise II (Fig. 2). Holes NBP0602A-8A-KC (Kasten Core) and NBP0602A-8B ( Fig. 5)) are located in 629 m of water (63º 20.572’ S, 55º 53.195’ W) whereas, Holes NBP0602A-C (Fig. 6) and NBP0602A-8D-KC are located in 624 m of water (63º 20.574’ S, 55º 53.145’ W) (Fig. 4). The longest hole, NBP0602A-8B, bottomed out at 79 mbsf in a stiff, mud-rich diamicton. The upper 8 m of this drill sequence were incoherent and not acceptable for sampling. Although the top 4 m of this sequence was recovered 100% by two Kasten Cores, that still left a subjacent sampling gap of 8 m. To cover this gap, a 23.76 m jumbo piston core (JPC) was taken a year later during the NBP0703 Cruise in 648 m of water (63° 20. 5003’ S, 55° 53.1001’ W). For the present study, samples were taken primarily from three of the four holes emplaced at NBP0602A Site 8 and the upper 8 m of the NBP0703 JPC Core 2. Summaries of their lithologies are given below. NBP0602A Drill Hole 8B Based on the original four core sequences taken at Site 8, the section in Hole B was divided into three lithologic units aboard ship as follows (Fig. 5, from Anderson et al. 2006): UNIT I (0-64.18 mbsf) consists of a greenish black to black diatomaceous mud with numerous thin (1-5 mm) black clay laminations and black mottling. Sand is present in trace percentages. Thin layers (1 to 3 cm) of silt-rich diatomaceous mud occur in the lower portion of the section. Macrofossils are rare to abundant, and sponge spicules, bivalves, and worm tubes occur throughout. Diatom percentages vary between 10-65% of the sediment. Other constituents include: clay (23-65%), quartz (3-22%), heavy minerals (4%), calcite (trace-2%), and feldspar, glauconite, hornblende, mica (trace to 1%). UNIT II (64.18-76.0 mbsf) consists of dark-gray clay to clayey mud with zones of pebbly mud and pebbly, sandy mud throughout the section. Graded-bed sequences of sand laminations and black silt are abundant. Macrofossils are very rare to absent. Diatom percentage abundances drop to 1-10% of the sediment. Other constituents include: clay

7 (62-80%), quartz (5-24%), feldspars and heavy minerals (trace to 7%), calcite (trace- 3%), and mica, glauconite, hornblende, and hematite (trace to 1%). UNIT III (76.0-79.0 mbsf) consists of a dark gray clay. No macrofossils or laminations are present. The upper 15 cm contains abundant pebbles and sand. Diatoms comprise traces (<1%-3%) of the sediment. Other constituents includes: clay (80-81%), quartz (10%), feldspars and heavy minerals (trace to 3%), calcite (3%), and trace amounts of mica, glauconite, hornblende, and hematite. NBP0602A Drill Hole 8C Hole 8C (25.0-33.04 mbsf) is offset 20 m from Hole 8B. This hole was drilled to complement an interval of Hole B with gaps and disturbed sections (Fig. 6, from Anderson et al. 2006). The sediment is a greenish black to black diatomaceous mud with evident black mottling. Bivalve shells, sponge spicules, and worm tubes occur throughout the sections. Diatoms comprise 10%-45% of the sediment. Other constituents include: clay (36-55%), quartz (7-17%), heavy minerals (1-5%), calcite (trace-1%), glauconite (trace-1%), and trace amounts of hornblende and hematite. NBP0703-JPC-02 Hole JPC 02 was taken to complement to the upper section (0-~8 mbsf) of disturbed sediments in Hole B (Fig. 7, from Anderson et al. 2009). The sections consist of diatom bearing clays, silty clays, and dark silty muds. A silty clay zone with dark organic matter and silty laminations occurs between 3.83-15.94 mbsf. Clays with bioturbated zones, dark organic matter, and shell fragments occur at 15.94-22.76 mbsf.

8 PREVIOUS WORK

The scientific party participants of the SHALDRIL II initiative conducted the shipboard analysis of the sediment cores recovered in the Firth of Tay (Anderson et al., 2006). Dr. Steven Bohaty, the diatom specialist, conducted a preliminary qualitative smear-slide analysis. His results include a relative abundance of individual taxa and paleoclimate interpretations. Drs. Winter and Iwai, the shipboard diatom specialists on the Ocean Drilling Project Leg 178, Site 1098, provided the initial analysis on marine sediment recovered in the Palmer Deep (Barker et al., 2002). Dr. Steven Bohaty also conducted the shipboard diatom analysis during the SHALDRIL I initiative at the Maxwell Bay Site (Anderson et al. 2005). Additional pertinent shore-based publications for the Palmer Deep include Domack et al. (2001), Sjunneskog and Taylor (2002), and Leventer et al. (2002). Subsequent studies for Maxwell Bay include a shore- based analysis of the diatom assemblage by Geary (unpublished 2008) and a Holocene climate record by Milliken et al. (2010). A robust radiocarbon chronostratigraphy has been derived from 31 marine-carbonate samples (mollusks, calcareous fragments) from the five cores collected in the Firth of Tay (Table III, from Michalchuk et al. 2009). Apparent ages were calculated using the Stuiver et al. (1998; 2005) CALIB. 5.0 radiocarbon calibration process with a 95% confidence interval. By accepted convention and for the sake of comparing circum-Antarctic glacial histories, in particular those from the Palmer Deep and Maxwell Bay sites, a 1300-year marine carbon reservoir correction was used to determine the 14C cal yr BP (Stuvier 1998, Domack 2001). All but one of the carbonate samples were collected in the upper 64 m of core. Twenty-eight of the radiocarbon dates fall into close chronological order with respect to depth. This study supports a strong age- depth agreement among the five holes cored at this site. The Kasten Cores 8A and 8D establish the sediment-water interface, and radiocarbon dates calculated from materials at 302 cm (8A) and 303 cm (8D) provide dates of 354 14C cal BP +/-61 and 394 cal 14C +/- 75, respectively. The JPC over-penetrated the sediment-water interface, but appropriate corrections were applied; the depths were adjusted downward one meter relative to sea floor and the core length expanded by 10% to compensate for possible compaction.

9 METHODS AND MATERIALS

Preparation of Settled Diatom Slides Sediment samples of 1-3 cc for this study were collected at approximately 50-cm intervals from the Firth of Tay cores take during the RV/IB N.B. Palmer cruises, NBP0602 and NBP0703. From these, diatom slides were prepared for quantitative study using a settling procedure adapted from the technique described by Scherer (1994). Each sample was placed in an oven and allowed to dry for two hours. Approximately 0.025 g of sediment was weighed out on a Mettler AE 200 scale and placed in a 2-dram bottle. Approximately 10 ml of a 30 % hydrogen peroxide solution was added to dissolve organic materials. In addition, 5 ml of a 0.5 % sodium hexametaphosphate solution was added to disperse clays. The contents of each bottle was gently stirred with a small glass rod and placed to warm, but not boil, on a hotplate for 5 minutes. The prepared solutions were added to beakers containing 500 ml of distilled water, gently stirred, and poured into clamped Bruckner funnels. With long arm tweezers, two prepared cover slips (coating removed by wiping with saliva) were carefully placed on the sieve base of each funnel. A minimum of six hours was allotted for the material to settle through the water column. The clamps on the tubing at the base of the funnels were loosened and the solution was dripped off at a very slow rate (one drip/second) to reduce turbidity. When the water was completely evacuated, the cover slips were allowed to dry in place for a minimum of 12 hours. The cover slips were then fixed to a clean, pre-labeled slide with Norland #61 optical cement and placed under an ultraviolet light to cure for a minimum of 10 minutes prior microscopic examination. Counting Procedures The diatoms on the prepared slides were identified and counted on a Zeiss Axioscope under Differential Interference Contrast illumination with 10x eyepieces and a 100x oil immersion objective. For floral assemblage census, two separate down-core counts were preformed on each of the slides. Only diatom valves more than 50 % intact were included in the tally to avoid counting the same specimen twice. Diatom abundances dropped significantly towards the base of the core (64-76.24 mbsf), and the

10 400 individual count was no longer feasible. Chaetoceros spp. (small veg. cells and resting spores) is the most abundant taxon present in the sediment samples. Often, with high abundances (>50/FOV), this taxon can obscure the background assemblage constituents and thereby mask climate signals. To alleviate this problem, two separate counts were conducted: 1) Chaetoceros spp., per field, and 2) a count of 400 specimens, excluding Chaetoceros spp., and the required fields of view to make the count. Other dominanat taxa include Thalassiosira antarctica, Fragilariopsis curta, F.cylindrus, F. vanheurckii, and Cocconeis spp. Diatoms of secondary dominance include Actinocyclus actinochilus, F. sublinearis, Navicula spp., and Porosira spp. The taxonomic index used in this study is shown in the Appendix. Where appropriate, identification was performed either to the species or genus level. In addition, one species, Eucampia Antarctica, was divided into the varieties Eucampia antarctica var. antarctica (asymmetric/subpolar), var. recta (symmetric/polar), and Eucampia antarctica terminal valve (Fryxell 1989). Chaetoceros spp. and non-Chaetoceros spp. Initial counts The two separate counts for Chaetoceros spp., small veg. cells and resting spores, and non-Chaetoceros spp. were conducted on all the slides examined for this project. As previously discussed, a very strong age-depth agreement of the five Firth of Tay cores has been established by the readiocarbon analysis (Michalchuk et al. 2009). Sections of Holes NBP0602A-8C and JPC0703-02 have been correlated to fill the gaps in Hole 8B. The composite core data, therefore, provide a continuous Holocene diatom record extending from 0-64 mbsf. Simpson’s Diversity Index (non-Chaetoceros spp.) The Simpson’s Diversity Index (1-D), which takes into account the species richness and evenness, is a measure of concentration of a classification. Richness is the number of species represented in the sample, and evenness is a measure of their relative abundances. Diversity (D) increases directly with increases in the species richness and evenness. D is a probability index that reflects the chance that any two individuals selected randomly from a sample will belong to a particular species.

11 ∑n(n-1) D = N(N-1) where n = the total number of individuals of a particular species (genus) N = number of individuals collected 1-D= the value adjustment

The D values range between 0 and 1, with 0 representing infinite diversity and 1, no diversity. This resultant number seems counter-intuitive, so the value is adjusted by subtracting D from 1; the index still ranges between 0 and 1, but the greater numerical value represents a greater the sample diversity. Shannon Wiener Diversity Index The Shannon Diversity information function is another widely used diversity formula. The H value is the average diversity per individual. s H = ∑ pi ln pi i = 1 where pi = proportion of the individuals found in the ith species ln indicates natural iogarithm 2 2 ∑ pi( ln pi) - (∑ pi ln pi) + S - 1 Var (H) = N 2N2 where S = total number of species N = total number of individuals σ = square root of Var (H) = the standard deviation There is a 95% confidence level that the mean of the Shannon Wiener index numbers will be between the high and low value. Probability (H-2σ < μ < H+2σ) = 95% where μ = the mean value of the Shannon Weiner index. Relative Abundance % Individual species/genus counts are expressed as a relative percentage as follows: A = n/400 where A = relative abundance (%) of a particular species (genus) n = number of valves of a species (genus)

12 Density The density of the non-Chaetoceros spp, count is expressed as follows: d = t/f where t = 400 (total number of valves) f = number of the fields of view Total Diatom Abundance Total diatom concentration (T) was calculated from a combined count including the total number of Chaetoceros spp. and non-Chaetoceros spp. individuals per sample. T = (NB/AF) Where N = total number of valves counted B = area of the bottom of funnel in mm2 A = area of the field of view in mm2 F = total number of fields of view M = mass of sample in grams m = total number of microfossils/unit mass (grams)

13 RESULTS

Initial Counts: Chaetoceros spp. and non-Chaetoceros spp. Chaetoceros spp. is the most abundant taxon present in all the samples examined for this study. Other dominanat taxa include Thalassiosira antarctica, Fragilariopsis curta, F.cylindrus, F. vanheurckii, and Cocconeis spp. Diatoms of secondary dominance include Actinocyclus actinochilus, F. sublinearis, Navicula spp., and Porosira spp. The data are shown in Figure 11 and Tables I and II. Species Diversity Indices, Density, and Total Diatom Abundance The data for these calculations are shown in Figures 8, 9 and Table IV. Species Richness Intervals (relative %) The relative % data of each species/genus was incorporated into a Sigma Plot program (Fig. 10) for visual examination and interpretation. The y-axis of the graphs represents the sample depths in mbsf. The x-axis displays the species/genus percentage contribution to the total non-Chaetoceros spp. count and is adjusted and normalized on each graph to allow easier visual comparison. Based on the diatom data, three intervals are designated in the compiled down-core sections. The summation of the relative abundances (%) of the subpolar proxies (Eucampia antarctica var. antarctica, Fragilariopsis kerguelensis, Fragilariopsis rhombica, Fragilariopsis clementia and Thalassiosira lentiginosa) and the accompanying radiocarbon dates (Milchalchuk et al. 2009) are shown in Figure 11. Zone 1: Zone 1 is subdivided into two subunits based on subtle variations within the diatom assemblages as follows: 0-30 mbsf: The assemblages are dominated by extant sea-ice associated flora including Thalassiosira antarctica (20-55 % of the assemblage), followed in decreasing abundance by Fragilariopsis curta (8-29 %), Cocconeis spp. (2-15.5%), F. cylindrus (4-10.75 %), Navicula spp. (1-8.25 %), F.vanheurckii (2-10.5 %), and Actinocyclus actinochilus, (1.25-6 %). Odontella weissflogii has strong acmes at

14 11.97 mbsf (23.75 %) and 13.12 mbsf (16.25 %). Pseudogomphomena spp. has two acmes at 5 mbsf (6.25 %) and 19.16 mbsf (6.25 %). Between 25-30 mbsf, F. cylindrus, Nitzschia spp., and Porosira spp. exhibit abundance increases. The T values range from 1.17E+08 to 6.14E+08, with acmes at 3.0 and 26.17 mbsf. The Simpson’s and Shannon Wiener Diversity Indices exhibit a cluster of high valves observed at the top of the core in samples recovered by the JPC 0703-02. 30-52 mbsf: The same sea-ice flora continue to dominate this section of the core. Slight overall abundance decreases, relative to the upper section, occur in several taxa, including Fragilariopsis curta, F. ritscheri, F. vanheurckii, Cocconeis spp., and Navicula spp. F. cylindrus contributes a higher average percentage of the assemblage, reaching an acme of 10.75 % at 26.082 mbsf. T values range from 1.01E+08 to 9.86E+08 with acmes at 32.44 and 50.04 mbsf. Zone 2 (52-64 mbsf): The zone is defined by abundance increases of Eucampia antarctica var. antarctica (0.25-3.75 %), E. antarctica var. recta (.25-5.5 %), Fragilariopsis kerguelensis ( .50- 7.0 %), F. sublinearis (1.75-8.5 %), Stellerima microtrias (.25-6.25 %), Thalassiosira gracilis var.gracilis/expecta (.75-8.5%), and T. lentiginosa (.25-2.5 %). Fragilariopsis clementia appears only in this zone at sample depths 57.79, 60.45, and 61.07 mbsf. Fragilariopsis curta, F. cylindrus, Navicula spp., Synedropsis spp., and T. antarctica decrease. T values range from 1.33E+08 to 6.55E+08 with acmes at 56.32 and 57.79 mbsf. The two diversity indices exhibit a cluster of high values at the lower portion of the interval from 57.79 to 64.07 mbsf. Zone 3 (64-76.35 mbsf): With the exception of sample depths of 65.87 and 66.37 mbsf, a significant abundance decrease of all taxa occurs and the remaining samples do not contain enough valves to support the Chaetoceros spp. and non-Chaetoceros spp. counts.

15 DISCUSSION

Species Diversity Relatively consistent extant sea-ice and open-water floral assemblages were observed throughout the three Firth of Tay cores examined for this study. Dominant taxa include Chaetoceros spp. resting spores, Thalassiosira antarctica, Fragilariopsis curta, F. cylindrus, F. vanheurckii, and Cocconeis spp. Taxa of secondary dominance significant for paleoclimate reconstruction include Eucampia antarctica var. antarctica, Fragilariopsis kerguelensis, and Thalassiosira lentginosa. Clusters of higher diversity index values in the Simpson’s Diversity index and the Shannon Wiener information function occur in the upper section (~4-8 mbsf) and lower in the section (~56-64 mbsf). A significant shift in the Shannon Wiener index indicates a dissimilar assemblage between ~56-64 mbsf. Total Diatom abundance (T) The quantitative term, T, determined by the diatom abundance formula (Scherer 1994), is the microfossil density of a sample to an established sediment weight (Fig. 8). The resulting abundance-per-mass absolute data has been utilized in recent paleoecological studies, including biostratigraphic and primary productivity interpretations (Leventer et al. 1993; Scherer 1994). In the previous Palmer Deep study, increased total diatom abundances correlate directly with increases in temperatures and primary productivity (Sjunneskog and Taylor, 2002). In the down- core sequence, the several T acmes in the upper and middle section and tight cluster of T acmes in the lower section correspond directly with Chaetoceros spp. acmes. Chaetoceros spp. resting spores (rs) The combined down-core assemblage is comprised of extant diatoms with open-water and/or sea-ice affinities. All samples examined from 0 – 64.18 mbsf are dominated by Chaetoceros spp. resting spores associated with increased upper water-column stability and spring diatom blooms of high primary productivity. The stabilization results during periods of warmer temperatures and decreases in wind velocities and salinity (Sjunneskog and Taylor 2002; Leventer 2002). Spore induction follows the bloom cycle with the advent of unfavorable growth conditions,

16 including nutrient limiting and temperature stress. Generally, as observed in the Maxwell Bay study, Chaetoceros spp.rs peaks trailed periods of elevated total diatom abundance (Geary 2008). Eucampia Antarctica Eucampia antarctica forms curved or straight colonial chains with different valve morphologies, and has been established as a valuable proxy for paleoclimate reconstruction (Leventer 2002). The straight colonial chain form, E. antarctica var. recta, with symmetric valve symmetry has sea-ice and polar affinity. The curved chain form, E. antarctica var. antarctica, with asymmetric valve symmetry has subpolar, open-water affinity (Leventer 2002). The terminal valves are affixed at both ends of the chain. Longer chains form in warmer conditions and typically, a lower ratio of terminal to intercalary valves is observed (Fryxell and Prasad 1990). Whitehead et al. (2005) document the utility of a ratio of intercalary and terminal valves, the Eucampia Index, as a climate proxy indicator. Unfortunately, the paucity of the individuals of this genus present in the samples for this study prevented the calculation of this index. Climate Interpretation Zone 3, 64-76.35 mbsf (~9400-7800 14C cal yr BP): The base of the core is a firm, homogenous diamicton, characteristic of a sub-glacial till or glacio-marine sediment deposited in the vicinity of the grounding line and represents the initiation of the ice sheet retreat and the early glacial melt-out period (Anderson 1999, Michalchuk et al. 2009). Several samples contained rare, highly fragmented diatom assemblages, but the record is patchy due to the high input of terrigenous material and sedimentation processes. This interval was delineated primarily by the paucity of diatoms that is a function of the early glacio-marine depositional environment. The low number of diatoms supports the initial establishment of sea-ice coverage and limited early open-water conditions in the embayment. Zone 2, 64-52 mbsf (~7800-6000 14C cal yr BP): The dark greenish-gray to black diatomaceous mud indicates a significant and abrupt shift from terrigenous to biogenic sediment composition. The diatom assemblages are ice-associated, but interestingly, relative to the up-core sections, contain lower abundances of the polar proxies, Fragilariopsis curta, F. cylindrus, Cocconeis spp., and Thalassiosira antarctica, and higher abundances of the subpolar proxies Eucampia antarctica var. antarctica, Fragilariopsis kerguelensis, Fragilariopsis clementia, Fragilariopsis rhombica, and Thalassiosira lentiginosa. The Chaetoceros spp. percentages and total diatom abundance (T), slightly elevated in comparison to the up-core values, suggest periods of higher

17 primary productivity (Table II). The Shannon Wiener index (with error bars) indicates a noticeable diversity shift, indicating a dissimilar assemblage. The increase in the relative abundances of the subpolar proxies, supported by the diversity shift, provides a recognizable signal for a warming interval, inferring a Mid-Holocene Climatic Optimum, which correlates to the radiocarbon dates of ~7800-6000 14C cal yr BP (Fig. 10). Zone 1, 52-0 mbsf (~6000-0 14C cal yr BP): The sediment in this interval is a dark-black to very dark greenish-gray diatomaceous mud, similar to the lithology in the section down-core. As the abundances of the subpolar floral proxies decrease upsection at ~ 52 mbsf (Fig.11), the abundances of the polar proxies, Fragilariopsis curta, F. cylindrus, Cocconeis spp., and Thalassiosira antarctica, increase. With the exception of several samples between 33-36 mbsf, Eucampia antarctica var. antarctica disappears from the assemblages. The diversity index and the total diatom abundance values are relatively uniform and generally lower than in the previous interval. An isolated acme of the Chaetoceros spp resting spores and the total diatom abundance (T) occurs at 32.44 mbsf, which hints at a brief interval of elevated temperatures and productivity (Fig. 8). A return to cooler temperatures, an expansion of the sea ice coverage, and reduced open water-conditions are indicated in this interval. Mid-Holocene Climatic Optimum; Comparison to Palmer Deep and Maxwell Bay Records The diatom analysis in this study supports evidence for the Climatic Optimum at approximately 64-52 mbsf with radiocarbon dates of 7780-6010 14C cal yr BP (Michalchuk et al. 2009). This differs only slightly from the interval documented at Maxwell Bay, on the northern tip of the peninsula: 8200-5900 14C cal yr BP (Milliken et al. 2010). The same event in Palmer Deep, on the northwestern side of the peninsula, is more extensive: 8700-4400 14C cal yr BP (Sjunneskog and Taylor 2002). Variations in the timing of the Mid-Holocene Climatic Optimum recorded in the three sites are largely affected by their settings. The earlier onset and longer duration of the event recorded in the Palmer Deep site may have been influenced by the warm current flowing from the Bellinghausen Sea (Fig. 12) that apparently stems from the Ross Sea Gyre (Fig.13). In contrast, the event is expressed with a later onset and shorter duration in the Maxwell Bay and the Firth of Tay sites, located on the continental side of the peninsula. Of interest, the event is more strongly indicated in the Maxwell Bay site, which may have been influenced by two water masses, the

18 warm Bellinghausen Sea current and the cold, dense water flowing counterclockwise in the Weddell Sea gyre (Fig. 13). The warming interval is less pronounced in the Firth of Tay site, suggesting a colder setting predominately influenced by the Weddell Sea gyre.

19 CONCLUSION

This study examines diatom assemblages in Holocene marine sediments in the Firth of Tay, off the northeastern tip of the Antarctic Peninsula. A down-core diatom census for the three cores studied, NBP0602A-8B, -8C, and NBP0703-02JPC, documents a relatively uniform sea-ice associated population throughout the section. Analysis of the diatom relative and absolute abundances, density, diversity, and proxy indicators, however, reveal paleoenvironmental variability throughout the Holocene. Three climatic events are recorded in the sediments: (1) a period of deglaciation from ~77- 64 mbsf, Zone 3 (radiocarbon dates, ~9400-7800 cal yr BP), supported by the sparse diatoms and glacio-marine sediments; (2) a Mid-Holocene Climatic Optimum from ~64-52 mbsf, Zone 2 (~7800-6000 cal yr BP), supported by the appearance of subpolar diatom proxies and a decrease of polar proxies; (3) and a cooling interval from ~52-0 mbsf, Zone 1 (~6000-0 cal yr BP), supported by the decrease and/or absence of subpolar diatom proxies and the increase in polar proxies. The Mid-Holocene Climatic Optimum is present in the Firth of Tay sequence and correlates closely with the timing and duration of the event in Maxwell Bay to the north (Milliken et al. 2010; Geary 2008). The same event is recorded in Palmer Deep on the opposite (west) side of the Antarctic Peninsula, but with an earlier onset and longer duration. The Climatic Optimum recorded at the Firth of Tay is less pronounced than at the other two sites however, due to the influence of the colder water from the Weddell Sea Gyre.

20 APPENDIX: TAXONOMIC INDEX

Achnanthes spp. Actinocyclus actinochilus (Ehrenberg) Simonsen, Villareal & Fryxell Amphora spp. Astermophalus hookeri (Ehrenberg) Fryxell & Hasle Chaetoceros rs (Ehrenberg) Cocconeis spp. Corethron criophilum (Castracane) Dactyliosolen spp. (girdle bands) Eucampia antarctica var. antarctica (Castracane) antarctica var. recta terminal valve Fallacia spp. Fragilariopsis curta (Van Heurck) Fragilariopsis cylindrus (Grunow) Krieger Fragilariopsis kerguelensis (O’Hara) Hustedt Fragilariopsis obliquecostata (Van Heurck) Heiden Fragilariopsis rhombica (O’Meara) Hustedt Fragilariopsis ritscheri (Hustedt) Fragilariopsis sublinerais (Van Heurck) Heiden Fragilariopsis vanheurckii (Perag.) Hustedt Gramataphora spp. Navicula spp. Nitzschia clementia (Gombos) Nitzschia spp. Odontella weissflogii (Janish) Grunow Paralia spp. Pleurosigma spp. Porosira spp. Proboscia spp. Pseudogomphonema spp. Rhizosolenia spp. Stellarima microtrias (Ehrenberg) Hasle & Sims Synedropsis spp. Thalassiothrix/nema spp. Thalassiosira antarctica (Comber) Thalassiosira gracilis var. Expecta (VanLandingham) gracilis var. gracilis (Karsten) Hustedt Thalassiosira lentiginosa (Janish) Fruxell Thalassiosira ritscheri (Hustedt) Hasle Thalassiosira tumida (Janish) Hasle

21 Table I: Species abundance

Hole/ Core/ Depth in cm Meters below seafloorAchnanthes spp. Actinocyclus actinochilus Am phora app. Asteromphalus spp. Biddulphia spp. Cocconeis spp. Corethron criophilim Coscinodiscus spp. Dactyliosolen girdle bands Delphineis spp. Fallacia spp. Entomoneis spp. Eucampia Antarctica terminal Eucampia ant. var.antarctica Eucampia ant. Var. recta Fragilariopsis curta Fragilariopsis cylindrus FragilariopsisFragilariopsis kerguelensis obliquecostata Fragilariopsis rhombica Fragilariopsis ritscheri Fragilariopsis sublinearis Fragilariopsis vanheurckii Gramataphora spp. Hylosynedra spp. JPC 02 01 1a, 1-2 0.01 10 3 31 4 27930 2181612 JPC 02 01 1a, 250 2.5 201 631 21 25520 32 41920 JPC 02 01 1b, 300 3 16 2234 1 1 116436 42 2 32828 JPC 02 01 2a, 350 3.5 212 1 4110 3 3 3 1 5028 3 5 4 52614 1 JPC 02 01 2b, 400 4 243 28 62 2 1 1863711 32029 JPC 02 01 2b, 450 4.51220 638 3 3 2 2 364619 6 222 6 5 8 JPC 02 01 2b, 500 5 2 26 2 139 8 94318 6 2 62215 1 JPC 02 01 3a, 650 6.5 8 120 2 1 2 37642215 2 4 7 2 JPC 02 01 3a, 700 7 230 1 12612 1 1 3 1 1 46037 9 3 1227 2 NBP0602-8B-5E, 39 cm 8.39 412 4 30 1 3 1 15329 2 8 1 31314 2 NBP0602-8B-5E, 88cm 8.88 16 27 2 2 2 5134 3 4 101221 NBP0602-8B-6E, 51cm 9.51 214 1 21 1 1 2 4 1 1 3624 4 21721 NBP0602-8B-6E, 116cm 10.16 413 1 18 2 4 2 5824 3 2 2 41419 2 NBP0602-8B-6E, 185cm 10.85 219 2 26 5 1 3 3 82 9 5 8 1 8 612 NBP0602-8B-7E, 30cm 11.30 212 7 22 3 1 211617 4 3 11215 NBP0602-8B-7E, 97cm 11.97 10 1 1 5 1 1 1 1 37521 113 2 6 9 NBP0602-8B-7E, 156cm 12.56 119 29 7 1 1 1 6 5818 2 5 21120 NBP0602-8B-7E, 212cm 13.12 2 5 2 8 1 2 9824 510 1 10 3 15 NBP0602-8B-7E, 292cm 13.92 2 2 16 1 1 2 10 9732 3 5 101320 NBP0602-8B-8E, 52cm 14.52 5 24 30 3 2 7925 410 12 15 22 NBP0602-8B-8E, 141cm 15.92 2 15 1 1 22 4 1 1 2 6516 520 6 1 424 NBP0602-8B-8E, 255cm 16.55 16 1 18 3 1 3 802312 8 1201420 NBP0602-8B-9E, 29.5cm 17.295 15 1 39 4 9916 1 1 1810 5 NBP0602-8B-9E, 92cm 17.92 114 27 1 1 1033110 11 292 NBP0602-8B-9E, 152.5cm 18.525 10 1 21 13215 6 81110 NBP0602-8B-9E, 216cm 19.16 5 32 1 1 1 55437 10 51110 9 NBP0602-8B-10E, 29cm 20.29 2 5 2 12 1 5820 4 2 315 814 NBP0602-8B-10E, 82.5cm 20.825 1 13 1 1910 1 3 5120 1 4 9 12 28 NBP0602-8B-10E, 139.5cm 21.395 1 17 1 28 10 36220 2 4 71322 1 NBP0602-8B-10E, 187.5cm21.875 3 6 14 6 1 1 2 5119 1 3 2 3 15 25 NBP0602-8B-12E, 15cm 23.15 3 9 2 39 6 1 2 3824 2 2 5 816 NBP0602-8B-12E, 73.5cm 23.735 10 4 19 1 1 1 5 6116 16 6 6 10 20 NBP0602-8B-12E, 134.5cm24.345 13 35 3 1 1 3 6119 2 5 2 6 6 7 NBP0602-8B-12E, 195cm 24.95 9 1 1 12 2 1 1 1 212117 1 7 5 10 13 20 NBP0602-8C-1E, 32.5cm 25.325 2 12 1 18 4 36438 1 1 51021 NBP0602-8B-12E, 244cm 25.44 310 2 28 3 1 6125 1 3 131031 NBP0602-8C-1E, 108.2cm 26.082 11 3 14 2 1 1 1 2 6420 5 2 2 5 7 14 NBP0602-8C-1E, 168.5cm 26.168 7 15 1 2 9222 11 13 71036 NBP0602-8B-13E, 17cm 26.17 1121 27 2 3 143 9 4 1522 NBP0602-8B-13E, 94.5cm 26.945 9 8 4 64815 2 1 6 530 NBP0602-8C-1E, 258cm 27.58 120 131 1 2 1 274 8 2 1 410 4 NBP0602-8B-13E, 234.5cm 28.23 4 16 31 4 1 1 4 5818 4 6 1 20 17 24 NBP0602-8C-2E, 26cm 28.26 115 1 245 1 1 26118 2 4 1 5 9 NBP0602-8C-2E, 94cm 28.94 1 19 1 1 20 4 522524 5 7 4 NBP0602-8B-13E, 302cm 29.02 1 19 1 20 1 1 1 6 6431 7 1 17 4 10 42 NBP0602-8C-2E, 161cm 29.61 3 14 3 42 2 3408 6 3612 NBP0602-8C-3E, 7cm 31.07 1 15 1 1 1 24 152 4 5 4 5 1 3271 NBP0602-8C-3E, 81cm 31.81 1 15 27 3 166 9 2 5 1 51219

22 Table I: (continued)

ca i var.

. t ntarct an A a a i i ucamp ucamp Hole/ Core/ Depth in cm Meters below seafloorAchnanthes spp. Actinocyclus actinochilus Amphora app. Asteromphalus spp. Biddulphia spp. Cocconeis spp. Corethron criophilim Coscinodiscus spp. Dactyliosolen girdle bands Delphineis spp. Fallacia spp. Entomoneis spp. E terminal E antarctica Eucampia ant. Var. recta Fragilariopsis curta Fragilariopsis cylindrus FragilariopsisFragilariopsis kerguelensis obliquecostata Fragilariopsis rhombica Fragilariopsis ritscheri Fragilariopsis sublinearis Fragilariopsis vanheurckiiGramataphora spp. Hylosynedra spp. NBP0602-8C-3E, 144cm 32.44 14 1 14 3 2 2 34115 5 6 3 53223 NBP0602-8C-3E, 204cm 33.04 18 2 27 2 1 2 25813 2 5 1 81925 NBP0602-8B-17E, 114cm 34.14 2 10 40 6 1 26635 5 1111112 NBP0602-8B-17E, 167cm 34.67 2 15 2 1 21 2 1 5552610 6 71419 NBP0602-8B-17E, 222cm 35.22 4 13 1 40 4 1 6131 4 5 2 1 8 4 NBP0602-8B-18E, 83cm 36.83 20 2 1 41 1 1 4020 1 1 21030 NBP0602-8B-18E, 155cm 37.55 4 2 21 10 1 1 59333 3 9 1917 NBP0602-8B-18E, 215cm 38.15 2 9 24 10 1 34310 2 3 1417 NBP0602-8B-19E, 38cm 39.38 7 1 14 1 370 91 2 34 7 7 NBP0602-8B-19E, 127cm 40.27 1 13 1 21 3 1 7528 110 3 61816 NBP0602-8B-19E, 173.5cm 40.73517 1861 2 13035121 1017 NBP0602-8B-19E, 245cm 41.45 1 4 2 1 19 8 2 2 102427 3 6 2 2511 1 NBP0602-8B-20E, 5cm 42.05 6 1 25 1 1 4 255412 4 1 3182223 NBP0602-8B-20E, 154cm 43.54 29 1 3 33 7 3 4934 1 4 11715 NBP0602-8B-20E, 216cm 44.16 8 1 25 3 24836 4 3 2 927 NBP0602-8B-21E, 18cm 45.18 10 1 1 10 4 2 1 12 31151511 911 8 7 NBP0602-8B-21E, 97.5cm45.975 1 15 3 24 9 1 65642 4 3 419 NBP0602-8B-21E, 145cm 46.45 1 22 1 1 21 10 1 2 62615 1 2 822 NBP0602-8B-21E, 225cm 47.25 2 5 1 11 2 1135643 5 8 1 1 8 NBP0602-8B-21E, 294cm 47.94 9 15 3 1 87154 112 92418 NBP0602-8B-22E, 23.5cm 48.235 3 13 22 1 5433 2 4 4 2 1726 NBP0602-8B-22E, 113cm 49.13 2 8 1 1 18 4 1 2 1 64542 5 3 818 NBP0602-8B-22E, 168cm 49.68 316 13 2 66642 1 7 720 NBP0602-8B-22E, 204cm 50.04 316 45 2 1 4828 1 21011 NBP0602-8B-22E, 256cm 50.56 2 9 1 16 1 251402 2 1119 NBP0602-8B-22E, 289cm 50.89 11 1 31 6 1 1 1 13411 1220 NBP0602-8B-23E, 17cm 51.17 1 19 1 1 26 6 1 15616 1 21027 NBP0602-8B-23E, 82.5cm51.8251 9 624121 2 403731 8162 NBP0602-8B-23E, 144cm 52.44 3 1 5 91 4211 1 114 29 14 NBP0602-8B-23E, 204cm 53.04 1 17 1 1 18 1 14124 9 2 2 1116 NBP0602-8B-23E, 222cm 53.22 21 1 10 3 1 7 46126 5 2 1 4 713 NBP0602-8B-24E, 34cm 54.34 1 20 2 1 17 1 1 1 1 4 5 5916 2 3 1 21330 NBP0602-8B-24E, 87cm 54.87 2 17 1 1 20 1 1 1511811 9 410 924 NBP0602-8B-24E, 173cm 55.73 11 2 1 8 3 15 85024 3 3 91018 NBP0602-8B-24E, 231.5cm 56.315 4 8 22122035114 132731 NBP0602-8B-24E, 254.5cm 56.545 41 1 61 710332449 83414 NBP0602-8B-25Es, 18cm 56.68 13 1 2 7 2 2 61249 6 6 263021 NBP0602-8B-25Es, 75.5cm 57.2554 124 4522761715 3587 NBP0602-8B-25Es, 129cm 57.79 1 9 3 8 3 1 2 1 11 17 3825 9 2 212 2433 NBP0602-8B-25Es, 174cm 58.24 4 19 1 1 2 16 11 3 2 10 6 321610 1 6 5 1827 3 NBP0602-8B-26E, 29cm 59.79 30 2 9 4 1 1 4 6461715 6 8 72433 NBP0602-8B-26E, 95cm 60.45 1 25 1 8 5 2 110 8 411520 9 9101723 NBP0602-8B-26E, 157cm 61.07 20 6 5 214 8341428 813 8 820 NBP0602-8B-26E, 227cm 61.77 18 4 3 12 2 1 12 11 44351312 6 4 3425 NBP0602-8B-27E, 23.5cm62.735 26 4 10 5 4 2 7 11 352212 8 811 19 30 NBP0602-8B-27E, 155cm 64.05 40 16 2 6 23911 412 1232 8 NBP0602-8B-27E, 238cm 64.43 1 4 11 NBP0602-8B-28E, 37cm 65.87 10 13 5 2 2 2 49418 3 8 112625 NBP0602-8B-28E, 86.5cm66.365 10 19 3 1 98 75 61414 NBP0602-8B-28E, 175cm 67.25 2 1 95 1 14 NBP0602-8B-28E, 243cm 67.93 1 2 NBP0602-8B-29E, 232cm 70.82 2 4 103 151 NBP0602-8B-30E, 7cm 71.57 NBP0602-8B-30E, 145.2cm 72.952 11 2 1 1 616 7 123 NBP0602-8B-30E, 280cm 73.3 1 1

23 Table I: (continued)

var.

c ili grac

. l a Hole/ Core/ Depth in cm Meters below seafloorNitzschia clementia Pseudo-Nitzschia spp. Odontella weissflogii Paralia spp. Pleurosigma spp. Porosira spp. Probosica spp. Pseudogomphonema spp. Rhizosolena spp. Stellarima microtris Synedropsis spp. Thalassiosira AntarcticaTh gracilis/expecta Thalassiosira lentiginosa Thalassiosira ritscheri Thalassiosira tumida Trachyneis spp. Pinnularia spp. JPC 02 01 1a, 1-2 0.01 5 6 36 15 6 7100 8 3 2 JPC 02 01 1a, 250 2.5 7 2 2 19 7 1 9145 4 3 JPC 02 01 1b, 300 3 5 11222 1297 7 2 JPC 02 01 2a, 350 3.5 7 2 2 2 151012 4 218 87 6 9 1 1 JPC 02 01 2b, 400 44 5 18 2 2 1 397 1 93 1 JPC 02 01 2b, 450 4.5 3 2 3 61412 7 1 6 91 4 3 JPC 02 01 2b, 500 5 722 16 2 5 3 1106 715 2 JPC 02 01 3a, 650 6.5 214 1555 461 1 6 47 2 4 1 JPC 02 01 3a, 700 7 3 3 2 1 18 8 5102 4 51 1 NBP0602-8B-5E, 39 cm 8.39 1029 2 31 2 5 10104 3 2 NBP0602-8B-5E, 88cm 8.88 14 8 19 1 6129 4 4 3 2 2 NBP0602-8B-6E, 51cm 9.51 5 6 48 3 1 6170 1 2 1 NBP0602-8B-6E, 116cm 10.16 4 9 10 1 2 3 2 8153 2 2 3 NBP0602-8B-6E, 185cm 10.85 5 7 13 2 1 411143 6 5 3 1 NBP0602-8B-7E, 30cm 11.30 221 8 2 2 1 6 8111 5 2 1 1 NBP0602-8B-7E, 97cm 11.97 495 15 1 7 5 7 87 2 5 2 NBP0602-8B-7E, 156cm 12.56 2 6 2 1 1 2 9155 10 2 8 NBP0602-8B-7E, 212cm 13.12 465 18 411 2 8 76 5 3 2 1 NBP0602-8B-7E, 292cm 13.92 211 19 8 1 122 10 2 NBP0602-8B-8E, 52cm 14.52 1 1 19 3 1 4 24 79 4 1 2 2 NBP0602-8B-8E, 141cm 15.92 2 7 12 11 5 2 6143 2 2 1 4 1 NBP0602-8B-8E, 255cm 16.55 5 6 4 1 1 4 4 12112 7 3 2 3 NBP0602-8B-9E, 29.5cm 17.3 3 2 8 3 2 2 2 16123 2 1 1 2 NBP0602-8B-9E, 92cm 17.92 715 10 111 14 78 3 1 3 1 NBP0602-8B-9E, 152.5cm 18.53 4 4 25 3 1 12220 2 2 1 1 NBP0602-8B-9E, 216cm 19.16 7 8 2 225 2 36103 3 1 NBP0602-8B-10E, 29cm 20.29 2 1 12 1 3 2 20179 2 2 3 2 NBP0602-8B-10E, 82.5cm 20.83 6 8 16 4 1 8149 5 1 NBP0602-8B-10E, 139.5cm 21.4 26 814 21712482 2 NBP0602-8B-10E, 187.5cm 21.88 58 12 38 14168421 1 NBP0602-8B-12E, 15cm 23.15 20 6 1 10 4 4 2 1 16144 4 1 1 1 1 1 NBP0602-8B-12E, 73.5cm 23.74 4 13 14 3 2 2 2 16133 3 1 NBP0602-8B-12E, 134.5cm 24.35 716 23 2 26 1 8151 5 NBP0602-8B-12E, 195cm 24.95 613 10 4 3 2114 2 2 3 1 1 NBP0602-8C-1E, 32.5cm 25.33 10 8 18 1 2 3 8136 3 3 6 NBP0602-8B-12E, 244cm 25.44 26 9 7 3 2 4 6125 7 2 1 3 1 NBP0602-8C-1E, 108.2cm 26.08 614 18 2 12171 4 1 1 1 NBP0602-8C-1E, 168.5cm 26.17 16 1 1 13 1 3 10126 3 NBP0602-8B-13E, 17cm 26.17 2 8 39 1 1 1 9181 2 2 1 1 NBP0602-8B-13E, 94.5cm 26.95 4 6 58 2 3 1 7165 2 2 2 NBP0602-8C-1E, 258cm 27.58 8 22 3 121156 1 2 3 1 NBP0602-8B-13E, 234.5cm 28.23 34 25413 2 4124 1112 NBP0602-8C-2E, 26cm 28.26 7 22 2 112160 6 2 3 NBP0602-8C-2E, 94cm 28.94 5 2 10 234 12164 2 7 2 1 NBP0602-8B-13E, 302cm 29.02 6 4 22 2 2 2 8 94 1 2 NBP0602-8C-2E, 161cm 29.61 9 6 25 2 2 12173 3 1 2 NBP0602-8C-3E, 7cm 31.07 720 30 1 10166 4 2 2 1 NBP0602-8C-3E, 81cm 31.81 6 4 17 3 210174 4 2 1 1

24 Table I: (continued)

. gracilic var . Hole/ Core/ Depth in cm Meters below seafloor Nitzschia clementia Pseudo-Nitzschia spp. Odontella weissflogii Paralia spp. Pleurosigm a spp. Porosira spp. Probosica spp. Pseudogomphonema spp. Rhizosolena spp. Stellarima microtris Synedropsis spp. ThalassiosiraThal Antarctica gracilis/expecta Thalassiosira lentiginosa Thalassiosira ritscheriThalassiosira tum ida Trachyneis spp. Pinnularia spp. NBP0602-8C-3E, 144cm 32.44 10 9 1 8 6 10164 4 2 NBP0602-8C-3E, 204cm 33.04 221 25 4 4 2 2 7131 3 3 2 1 NBP0602-8B-17E, 114cm 34.14 9 1 18 1 6 2 12120 3 1 1 1 2 NBP0602-8B-17E, 167cm 34.67 12 5 26 1 1 5 1 16135 1 1 NBP0602-8B-17E, 222cm 35.22 11 2 18 1 4 1 22114 2 2 2 2 NBP0602-8B-18E, 83cm 36.83 14 4 30 1 6 155 6 1 2 NBP0602-8B-18E, 155cm 37.55 9 7 10 4 3 13 9417 5 NBP0602-8B-18E, 215cm 38.15 12 4 16 9 1 1 36170 2 1 NBP0602-8B-19E, 38cm 39.38 7 6 25 2 1 12191 5 3 3 3 NBP0602-8B-19E, 127cm 40.27 210 34 1 2 6130 4 3 2 1 1 NBP0602-8B-19E, 173.5cm 40.735 202 22 29 7174 924 NBP0602-8B-19E, 245cm 41.45 19 16 6 34 2 1313310 8 2 NBP0602-8B-20E, 5cm 42.05 12 5 12 1 4141 8 1 1 1 NBP0602-8B-20E, 154cm 43.54 10 3 10 7 2 7147 1 1 2 NBP0602-8B-20E, 216cm 44.16 9 15 2 3 4 5 716717 1 1 NBP0602-8B-21E, 18cm 45.18 9 4 23 3198 1 5 2 1 NBP0602-8B-21E, 97.5cm 45.975 7 1 11 2 5 155 3 5 2 NBP0602-8B-21E, 145cm 46.45 2 16 1 2 6216 9 1 1 NBP0602-8B-21E, 225cm 47.25 2711 18 1 1 18140 7 3 1 NBP0602-8B-21E, 294cm 47.94 6 1 8 2 2 2 8129 2 9 1 1 NBP0602-8B-22E, 23.5cm 48.235 9 5 8 3 2 4163 9 6 1 5 NBP0602-8B-22E, 113cm 49.13 6 8 2 1 3 1 6189 7 2 NBP0602-8B-22E, 168cm 49.68 21 1 12 1 1 155 2 2 1 1 NBP0602-8B-22E, 204cm 50.04 5 9 3 6 200 3 2 NBP0602-8B-22E, 256cm 50.56 28 2 12181 4 3 1 NBP0602-8B-22E, 289cm 50.89 2 26 2 12202 4 2 2 NBP0602-8B-23E, 17cm 51.17 8 1 8 718 16156 1 1 1 1 NBP0602-8B-23E, 82.5cm 51.825 6 1 17 1 3 1 6163 4 2 2 1 NBP0602-8B-23E, 144cm 52.44 11 1 2 11 1 1 4 10130 1 1 NBP0602-8B-23E, 204cm 53.04 6 14 3 2 1 12204 3 NBP0602-8B-23E, 222cm 53.22 6 4 22 1 3 2 6174 2 3 NBP0602-8B-24E, 34cm 54.34 5 20 1 4 1 17155 4 1 2 NBP0602-8B-24E, 87cm 54.87 14 3 26 1 310 146 4 1 NBP0602-8B-24E, 173cm 55.73 13 2 9 3 6 816511 7 1 2 NBP0602-8B-24E, 231.5cm 56.315 12 115 1 3 419513 NBP0602-8B-24E, 254.5cm 56.545 81 2 30 2 2 51724522 NBP0602-8B-25Es, 18cm 56.68 15 14 2 3 2 155 7 1 2 NBP0602-8B-25Es, 75.5cm57.255 5 1 16 1 1 414733 5 1 NBP0602-8B-25Es, 129cm 57.79 3 8 9 19 4 11 3 9113 3 4 2 1 NBP0602-8B-25Es, 174cm 58.24 3 7 5 13 2 6 12 911410 10 5 1 NBP0602-8B-26E, 29cm 59.79 2 10 7 17 5 1 11 1 7 96 8 7 3 3 NBP0602-8B-26E, 95cm 60.45 12 8 25 2 1 5 1 6108 7 4 1 2 1 NBP0602-8B-26E, 157cm 61.07 10 4 51 4 2117 8 1 1 NBP0602-8B-26E, 227cm 61.77 14 8 18 3 2 2 100 3 4 1 NBP0602-8B-27E, 23.5cm 62.735 15 6 1 20 1 10 5 2 94 9 8 3 1 NBP0602-8B-27E, 155cm 64.05 16 6 725 113014 7 4 NBP0602-8B-27E, 238cm 64.43 1 NBP0602-8B-28E, 37cm 65.87 16 2 28 8034 6 8 NBP0602-8B-28E, 86.5cm 66.365 521 1 18 2 2 311242 7 5 NBP0602-8B-28E, 175cm 67.25 1 1412 1 NBP0602-8B-28E, 243cm 67.93 13 5 NBP0602-8B-29E, 232cm 70.82 1 1 24 3 NBP0602-8B-30E, 7cm 71.57 NBP0602-8B-30E, 145.2cm 72.952 2 6 5011 1 NBP0602-8B-30E, 280cm 73.3 42 1

25 Table II: Chaetoceros spp. abundance, (T) Total diatom abundance/ g sediment

Core mbsf # FOV Chaet. spp. Chaet. spp. Total Sed (M) in gArea (A) (B) Funne T # valves 400 count /FOV total valves FOV mm² base mm² /g sed JPC 02 01 1a, 1-2 cm 0.01 140 23 3220 3620 0.0252 0.044 9075 2.12E+08 JPC 02 01 1a, 250 cm 2.50 118 40 4720 5120 0.0255 0.044 9075 3.51E+08 JPC 02 01 1b, 300 cm 3.00 98 70 6860 7260 0.025 0.044 9075 6.11E+08 JPC 02 01 2a, 350 cm 3.50 124 10 1240 1640 0.0253 0.044 9075 1.08E+08 JPC 02 01 2b, 400 cm 4.00 122 40 4880 5280 0.0255 0.044 9075 3.50E+08 JPC 02 01 2b, 450 cm 4.50 116 65 7540 7940 0.0247 0.044 9075 5.72E+08 JPC 02 01 2b, 500 cm 5.00 94 55 5170 5570 0.0247 0.044 9075 4.95E+08 JPC 02 01 3a, 650 cm 6.50 92 30 2760 3160 0.0252 0.044 9075 2.81E+08 JPC 02 01 3a, 700 cm 7.00 103 55 5665 6065 0.0247 0.044 9075 4.92E+08 8B-5E, 39 cm 8.39 127 15 1905 2305 0.0256 0.044 9075 1.46E+08 8B-5E, 88cm 8.88 325 17 5525 5925 0.025 0.044 9075 1.50E+08 8B-6E, 51cm 9.51 250 30 7500 7900 0.0253 0.044 9075 2.58E+08 8B-6E, 116cm 10.16 230 15 3450 3850 0.0257 0.044 9075 1.34E+08 8B-6E, 185cm 10.85 140 25 3500 3900 0.0251 0.044 9075 2.29E+08 8B-7E, 30cm 11.30 170 12 2040 2440 0.0253 0.044 9075 1.17E+08 8B-7E, 97cm 11.97 77 17 1309 1709 0.025 0.044 9075 1.83E+08 8B-7E, 156cm 12.56 165 15 2475 2875 0.0255 0.044 9075 1.41E+08 8B-7E, 212cm 13.12 117 20 2340 2740 0.0251 0.044 9075 1.92E+08 8B-7E, 292cm 13.92 102 15 1530 1930 0.0259 0.044 9075 1.51E+08 8B-8E, 52cm 14.52 210 23 4830 5230 0.0257 0.044 9075 2.00E+08 8B-8E, 141cm 15.92 88 28 2464 2864 0.0255 0.044 9075 2.63E+08 8B-8E, 255cm 16.55 108 30 3240 3640 0.0254 0.044 9075 2.74E+08 8B-9E, 29.5cm 17.30 206 25 5150 5550 0.0257 0.044 9075 2.16E+08 8B-9E, 92cm 17.92 112 20 2240 2640 0.0254 0.044 9075 1.91E+08 8B-9E, 152.5cm 18.53 136 30 4080 4480 0.0247 0.044 9075 2.75E+08 8B-9E, 216cm 19.16 229 16 3664 4064 0.0245 0.044 9075 1.49E+08 8B-10E, 29cm 20.29 141 20 2820 3220 0.0257 0.044 9075 1.83E+08 8B-10E, 82.5cm 20.83 170 35 5950 6350 0.025 0.044 9075 3.08E+08 8B-10E, 139.5cm 21.40 138 35 4830 5230 0.0247 0.044 9075 3.16E+08 8B-10E, 187.5cm 21.88 144 20 2880 3280 0.026 0.044 9075 1.81E+08 8B-12E, 15cm 23.15 141 65 9165 9565 0.0255 0.044 9075 5.49E+08 8B-12E, 73.5cm 23.74 122 45 5490 5890 0.0243 0.044 9075 4.10E+08 8B-12E, 134.5cm 24.35 119 30 3570 3970 0.0255 0.044 9075 2.70E+08 8B-12E, 195cm 24.95 95 35 3325 3725 0.0259 0.044 9075 3.12E+08 8C-1E, 32.5cm 25.33 108 15 1620 2020 0.0268 0.044 9075 1.44E+08 8B-12E, 244cm 25.44 162 18 2916 3316 0.026 0.044 9075 1.62E+08 8C-1E, 108.2cm 26.08 127 20 2540 2940 0.0246 0.044 9075 1.94E+08 8C-1E, 168.5cm 26.17 144 30 4320 4720 0.0252 0.044 9075 2.68E+08 8B-13E, 17cm 26.17 166 75 12450 12850 0.026 0.044 9075 6.14E+08 8B-13E, 94.5cm 26.95 151 25 3775 4175 0.0244 0.044 9075 2.34E+08 8B-13E, 234.5cm 28.23 126 21 2646 3046 0.0261 0.044 9075 1.91E+08 8C-1E, 258cm 27.58 177 30 5310 5710 0.0257 0.044 9075 2.59E+ 08 8C-2E, 26cm 28.26 264 25 6600 7000 0.0251 0.044 9075 2.18E+08 8C-2E, 94cm 28.94 142 20 2840 3240 0.0261 0.044 9075 1.80E+08 8B-13E, 302cm 29.02 119 20 2380 2780 0.0252 0.044 9075 1.91E+08 8C-2E, 161cm 29.61 128 25 3200 3600 0.0267 0.044 9075 2.17E+08

26 Table II: (continued)

Core mbsf # FOV Chaet. spp.Chaet. spp.Total Sed (M) in g Area (A) (B) Funnel T # valves 400 count / FOV total valves FOV mm² base mm² / g sed 8C-3E, 7cm 31.07 128 20 2560 2960 0.026 0.044 9075 1.83E+08 8C-3E, 81cm 31.81 162 52 8424 8824 0.0252 0.044 9075 4.46E+0 8 8C-3E, 144cm 32.44 206 75 15450 15850 0.0253 0.044 9075 6.27 E+ 08 8C-3E, 204cm 33.04 163 40 6520 6920 0.0262 0.044 9075 3.34E+ 08 8B-17E, 114cm 34.14 159 20 3180 3580 0.0262 0.044 9075 1.77E+08 8B-17E, 167cm 34.67 150 30 4500 4900 0.0259 0.044 9075 2.60E+08 8B-17E, 222cm 35.22 164 12 1968 2368 0.0255 0.044 9075 1.17E+08 8B-18E, 83cm 36.83 142 10 1420 1820 0.0257 0.044 9075 1.03E+ 08 8B-18E, 155cm 37.55 150 45 6750 7150 0.0252 0.044 9075 3.90E+08 8B-18E, 215cm 38.15 94 12 1128 1528 0.0255 0.044 9075 1.31E+ 08 8B-19E, 38cm 39.38 182 27 4914 5314 0.0256 0.044 9075 2.35E+ 08 8B-19E, 127cm 40.27 204 13 2652 3052 0.0262 0.044 9075 1.18E+08 8B-19E, 173.5cm 40.74 142 55 7810 8210 0.0243 0.044 9075 4.91E+08 8B-19E, 245cm 41.45 140 27 3780 4180 0.0255 0.044 9075 2.41E+08 8B-20E, 5cm 42.05 90 45 4050 4450 0.026 0.044 9075 3.92E+08 8B-20E, 67.5cm 42.68 144 30 4320 4720 0.0261 0.044 9075 2.59 E+ 08 8B-20E, 154cm 43.54 209 10 2090 2490 0.0243 0.044 9075 1.01E+08 8B-20E, 216cm 44.16 140 15 2100 2500 0.0244 0.044 9075 1.51E+08 8B-21E, 18cm 45.18 184 22 4048 4448 0.0251 0.044 9075 1.99E+ 08 8B-21E, 97.5cm 45.98 225 15 3375 3775 0.0255 0.044 9075 1.36 E+ 08 8B-21E, 145cm 46.45 154 17 2618 3018 0.0247 0.044 9075 1.64E+08 8B-21E, 225cm 47.25 150 23 3450 3850 0.0254 0.044 9075 2.08E+08 8B-21E, 294cm 47.94 146 28 4088 4488 0.0254 0.044 9075 2.50E+08 8B-22E, 23.5cm 48.24 164 24 3936 4336 0.0243 0.044 9075 2.24 E+ 08 8B-22E, 113cm 49.13 172 17 2924 3324 0.025 0.044 9075 1.59E+ 08 8B-22E, 168cm 49.68 170 62 10540 10940 0.0245 0.044 9075 5.42E+08 8B-22E, 204cm 50.04 205 10 2050 2450 0.025 0.044 9075 9.86E+ 07 8B-22E, 256cm 50.56 196 33 6468 6868 0.0253 0.044 9075 2.86E+08 8B-22E, 289cm 50.89 162 10 1620 2020 0.0255 0.044 9075 1.01E+08 8B-23E, 17cm 51.17 122 37 4514 4914 0.0247 0.044 9075 3.36E+ 08 8B-23E, 82.5cm 51.83 121 8 968 1368 0.0257 0.044 9075 9.07E+ 07 8B-23E, 144cm 52.44 154 65 10010 10410 0.0254 0.044 9075 5.49E+08 8B-23E, 204cm 53.04 99 16 1584 1984 0.0253 0.044 9075 1.63E+ 08 8B-23E, 222cm 53.22 145 15 2175 2575 0.0251 0.044 9075 1.46E+08 8B-24E, 34cm 54.34 160 15 2400 2800 0.0259 0.044 9075 1.39E+ 08 8B-24E, 87cm 54.87 137 30 4110 4510 0.0255 0.044 9075 2.66E+ 08 8B-24E, 173cm 55.73 120 25 3000 3400 0.0251 0.044 9075 2.33E+08 8B-24E, 231.5cm 56.32 175 70 12250 12650 0.0247 0.044 9075 6.04E+ 08 8B-24E, 294.5cm 56.55 126 20 2520 2920 0.0247 0.044 9075 1.94E+08 8B-25Es, 18cm 56.68 161 75 12075 12475 0.0253 0.044 9075 6.32E+08 8B-25Es, 75.5cm 57.26 62 20 1240 1640 0.0247 0.044 9075 2.21 E+ 08 8B-25Es, 129cm 57.79 71 75 5325 5725 0.0254 0.044 9075 6.55E+08 8B-25Es, 174cm 58.24 68 30 2040 2440 0.025 0.044 9075 2.96E+ 08 8B-26E, 29cm 59.79 80 40 3200 3600 0.0251 0.044 9075 3.70E+0 8 8B-26E, 95cm 60.45 79 20 1580 1980 0.0258 0.044 9075 2.00E+0 8 8B-26E, 157cm 61.07 176 65 11440 11840 0.0257 0.044 9075 5.40E+08 8B-26E, 227cm 61.77 170 30 5100 5500 0.0247 0.044 9075 2.70E+08 8B-27E, 23.5cm 62.74 184 40 7360 7760 0.0249 0.044 9075 3.49 E+ 08 8B-27E, 155cm 64.05 320 5 1600 2000 0.0257 0.044 9075 5.02E+ 07 8B-28E, 37cm 65.87 297 20 5940 6340 0.0257 0.044 9075 1.71E+ 08 8B-28E, 86cm 66.46 282 15 4230 4630 0.0255 0.044 9075 1.33E+ 08

27 Table III: Radiocarbon data with 14C age BP (uncalibrated) and 14C age (calibrated) value. Sample name Core–core depth Core depth Core depth (mbsf) Fraction modern ± d14C ± 14C age (BP) ± 14C age ± UCIAMS31896 8A-KC-80 80 0.8 0.8351 0.0014 164.90 1.4 1445 15 190 70.5 UCIAMS40677 8A-KC-302 302 3.02 0.8183 0.0015 181.70 1.5 1610 15 354 61 UCIAMS40693 8B-5E-54 854 8.54 0.7898 0.0015 210.20 1.5 1895 20 582 51.5 UCIAMS40678 8B-6E-159 1059 10.59 0.764 0.0016 236.00 1.6 2165 20 811 75 UCIAMS40685 8B-6E-201 1101 11.01 0.7655 0.0014 234.50 1.4 2145 15 783 73 UCIAMS40684 8B-7E-236 1336 13.36 0.7881 0.0017 211.90 1.7 1915 20 594 51 UCIAMS40692 8B-9E-140 1840 18.4 0.7153 0.0013 284.70 1.3 2690 15 1326 48 UCIAMS40689 8B-12E-99 2399 23.99 0.6502 0.0012 349.80 1.2 3460 20 2238 79 UCIAMS40705 8B-12E-269 2569 25.69 0.6436 0.0012 356.40 1.2 3540 15 2323 50.5 UCIAMS40842 8B-13E-26 2626 26.26 0.6187 0.0017 381.30 1.7 3855 25 2732 51.5 UCIAMS40858 8B-16E-29 3279 32.79 0.6087 0.0017 391.30 1.7 3990 25 2858 86 UCIAMS40680 8B-16E-29 3279 32.79 0.6081 0.0014 391.90 1.4 3995 20 2864 81 UCIAMS40681 8B-17E-30 3330 33.3 0.7739 0.0014 226.10 1.4 2060 15 699 45.5 UCIAMS40691 8B-17E-102 3402 34.02 0.5619 0.0012 438.10 1.2 4630 20 3652 85.5 UCIAMS40855 8B-18E-282 3882 38.82 0.7205 0.002 279.50 2 2635 25 1286 55.5 UCIAMS40679 8B-19E-58 3958 39.58 0.5377 0.001 462.30 1 4985 20 4127 93 UCIAMS40846 8B-20E-134 4334 43.34 0.4881 0.0016 511.90 1.6 5760 30 5172 115.5 UCIAMS40841 8B-21E-268 4768 47.68 0.4783 0.0014 521.70 1.4 5925 25 5375 74 UCIAMS40857 8B-22E-254 5054 50.54 0.443 0.0016 557.00 1.6 6540 30 6042 1.075 UCIAMS40856 8B-24E-253 5653 56.53 0.4214 0.0047 578.60 4.7 6940 90 6465 192.5 UCIAMS40848 8B-26E-204 6154 61.54 0.3737 0.0015 626.30 1.5 7905 35 7500 68 UCIAMS40687 8C-1E-57 2557 25.57 0.6291 0.0013 370.90 1.3 3725 20 2594 103.5 UCIAMS28068 8C-1E-174 2674 26.74 0.6236 0.0011 376.40 1.1 3795 15 2642 11 UCIAMS31895 8C-2E-88 2888 28.88 0.6031 0.001 396.90 1 4060 15 2946 85.5 UCIAMS40844 8D-KC-303-318 303 3.03 0.8144 0.0025 185.60 2.5 1650 25 394 75 UCIAMS40699 JPC02-5A-62 1253 12.53 0.7526 0.0014 274.40 1.4 2285 15 930 48 UCIAMS40694 JPC02-7D-47.5 2088 20.88 0.6608 0.0013 339.20 1.3 330 20 2068 76 UCIAMS40697 JPC02-8A-38 2153 21.53 0.6551 0.0013 344.90 1.3 3400 20 2168 95 UCIAMS40854 JPC02-8B-8 2273 22.73 0.6351 0.0018 364.90 1.8 3645 25 2586 121.5 UCIAMS40696 JPC02-core 2376 23.76 0.6215 0.0012 378.50 1.2 3820 20 2710 44.5 OS-69717 8B-29E-50–52 6900 69 0.3387 0.0018 663.60 0 8700 40 8264 91 OS-69716 8B-31E-10–12 7460 74.6 0.523 0.27 480.60 0 5210 40 4433 125 OS-66058 8B-31E-110 7550 75.5 0.5741 0.0031 3.90 0 4460 45 3449 112 (from Michalchuk et al. 2009)

28 Table IV: Shannon Wiener Index data with high and low error values.

depth depth (mbsf) low Shannon high (mbsf) low Shannon high 0.01 2.393313 2.447294 2.501274 31.81 2.04076 2.110861 2.180962 2.50 2.270874 2.333668 2.396463 32.44 2.238378 2.306508 2.374637 3.00 2.445841 2.496771 2.547701 33.04 2.392313 2.455373 2.518434 3.50 2.775509 2.831065 2.886621 34.14 2.350831 2.410085 2.469339 4.00 2.370405 2.427802 2.485199 34.67 2.374024 2.435495 2.496967 4.50 2.728117 2.782133 2.83615 35.22 2.351918 2.409637 2.467356 5.00 2.593505 2.647323 2.701141 36.83 2.123195 2.183969 2.244743 6.50 2.554933 2.605427 2.655922 37.55 2.41669 2.471866 2.527041 7.00 2.542535 2.600728 2.658921 38.15 2.114328 2.180684 2.24704 8.39 2.536688 2.591656 2.646624 39.38 1.919451 1.993925 2.068398 8.88 2.372916 2.431032 2.489147 40.27 2.268684 2.330909 2.393134 9.51 2.086185 2.154736 2.223286 40.74 2.139177 2.207794 2.276411 10.16 2.269152 2.338137 2.407122 41.45 2.505559 2.567029 2.628498 10.85 2.284376 2.354457 2.424538 42.05 2.30963 2.371369 2.433108 11.30 2.239957 2.306403 2.37285 43.54 2.218604 2.280274 2.341945 12.56 2.21479 2.281441 2.348092 44.16 2.098019 2.164552 2.231085 11.97 2.28856 2.349605 2.41065 45.18 2.061653 2.138274 2.214896 13.12 2.397808 2.45698 2.516151 45.98 2.1393 2.203108 2.266916 14.52 2.512843 2.562527 2.612211 46.45 1.837914 1.91447 1.991027 15.92 2.342359 2.410515 2.478671 47.25 2.251455 2.312622 2.373789 16.55 2.459311 2.520031 2.580751 47.94 2.23497 2.296267 2.357563 17.30 2.140873 2.202712 2.26455 48.24 2.146271 2.213326 2.280381 17.92 2.364292 2.416658 2.469024 49.13 1.998245 2.072564 2.146883 18.53 1.784967 1.860596 1.936225 49.68 2.050163 2.111547 2.172931 19.16 2.432617 2.484312 2.536007 50.04 1.76248 1.830182 1.897884 20.29 2.038225 2.109565 2.180904 50.56 1.907745 1.972211 2.036678 20.83 2.254747 2.317205 2.379662 50.89 1.848112 1.917704 1.987296 21.40 2.377717 2.436811 2.495906 51.17 2.170789 2.234987 2.299185 21.88 2.181858 2.251944 2.32203 51.83 2.052994 2.121667 2.190339 23.15 2.369489 2.435892 2.502294 52.44 2.099779 2.159348 2.218917 23.74 2.369136 2.430693 2.49225 53.04 1.880213 1.952906 2.025599 24.35 2.217124 2.282569 2.348015 53.22 2.081846 2.153196 2.224546 24.95 2.215497 2.284617 2.353737 54.34 2.216212 2.284458 2.352704 25.33 2.284809 2.346591 2.408372 54.87 2.31077 2.373885 2.437 25.44 2.391051 2.451634 2.512217 55.73 2.261505 2.331632 2.401758 26.08 2.108071 2.179038 2.250005 56.32 1.93246 2.003259 2.074058 26.17 2.171048 2.229636 2.288223 56.55 2.180965 2.251999 2.323032 26.17 1.989403 2.058066 2.12673 56.68 2.228796 2.293185 2.357575 26.95 2.037355 2.103824 2.170293 57.26 2.171226 2.236673 2.30212 27.58 2.065806 2.131406 2.197007 57.79 2.682607 2.742099 2.801591 27.35 2.420232 2.481016 2.541801 58.24 2.804661 2.865059 2.925458 28.02 2.472418 2.525031 2.577644 59.79 2.75738 2.812337 2.867294 28.26 2.074032 2.139736 2.20544 60.45 2.721744 2.778956 2.836169 28.94 2.137473 2.204551 2.271629 61.07 2.501614 2.55703 2.612447 29.61 2.083766 2.151674 2.219583 61.77 2.639106 2.691845 2.744585 31.07 2.11434 2.182191 2.250043 62.74 2.827253 2.878855 2.930457

Figure 1: Study area (from Anderson et al. 2007).

Figure 2: Map of Antarctic Peninsula and site locations: Firth of Tay drill hole locations: Drill Hole NBP0602A-8B, 63˚ 20.572’ S, 55˚ 53.195’ W Drill Hole NBP0602A-8C, 63˚ 20.574’ S, 55˚ 53.145’ W Drill Hole NBP0703-02 JPC, 63˚ 20.5003’ S, 55˚ 53.1001’ W (after commons.wikimedia.org/wiki/Antarctic_Peninsula_location_map.svg)

Figure 3: Seismic profile of core site NBP0602A-8B (from Anderson et al. 2006).

Figure 4: Bathymetric survey of study site (from Anderson et al. 2006).

Figure 5: Lithologic description for core NBP0602A-8B (from Anderson et al. 2006).

Figure 6: Lithologic description sheet for core NBP0602A-8C (from Anderson et al. 2009).

Figure 7: Lithologic description of core NBP0703 JPC-02 (from Anderson et al. 2009).

Figure 8: Down-core diatom data, including T values (total number of valves/g sed.), density, Chaetoceros spp. abundance, and Simpson’s Diversity Index. Radiocarbon data points are in uncalibrated Age BP (Michalchuk et al. 2009).

37 Shannon-Wiener index

35 Depth (mbsf)Depth

65 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0

Index

Figure 9: Shannon Wiener index values with error bars (95% confidence).

Figure 10: Relative diatom abundance (%)

Figure 10: (continued)

Cooling interval Mid-Holocene Mid-Holocene Climatic Optimum Deglaciation

)

= 0.98 = 2

) R Sed.cm/yr rate = 0.7 ( (cal. yr BP) Age = 0.98 =

2 Age (calibrated yearsBP) Age R Sed.cm/yr rate = 1.6 (

0 2000 4000 6000 8000 10000

10 20 30 40 50 60 70 6

) (mbsf Depth

Warm water taxa (%) taxa water Warm

(%) Water-water taxa

0481 0

10 20 30 40 50 60 70

) (mbsf Depth Depth (mbsf)

Figure 11: Summation of the subpolar proxies as supporting evidence for a Mid-Holocene Climatic Optimum with the calibrated radiocarbon age data points (Michalchuk et al. 2009). Best-fit lines provide an alternate interpretation of sedimentation rates.

Figure 12: Map of the Bransfield Basin and different surface water masses, the Bellinghausen Sea current, the Weddell Sea gyre, and the Antarctic circumpolar Current (ACC) (from Anderson 1999).

Figure 13: Map of Antarctica and the surrounding water masses (from Barcena et al 1998)

44 Plate I

| 10 µ |

1 2

4 3

5 6

Figures: 1. Asteromphalus spp.; 2 Asteromphalus spp.; 3.Actinocyclus actinochilis; 4. Porosira spp.; 5. Coscinodiscus spp.; 6. Coscinodiscus spp.

45 Plate II

2 1

| 10 µ |

6 5

7 8

Figures: 1. Thalassiosira antarctica; 2. Thalassiosira letinginosa spp.; 3. Thalassiosira gracilis var. gracilis; 4. Thalassiosira gracilis var. expecta; 5. Thalassiorira ritcherii: 6. Thalassiorira ritcherii: 7. Thalassiosira tumida; 8. Stellerima microtris

46 Plate III

3 | 10 µ |

5 6

7 8 9

Figures: 1. Fragilariopsis cylindrus; 2. Fragilariopsis ritscheri; 3. Fragilariopsis kerguelensis; 4. Fragilariopsis curta; 5. Fragilariopsis rhombica; 6. Fragilariopsis vanheurckii; 7. Fragilariopsis obliquecostata; 8. Fragilariopsis sublinerais; 9. Silicoflagellate sp.

47 Plate IV

1 2 3

4 5

| 10 µ |

7 8

Figures: 1. Cocconeis spp.; 2. Pseudo-nitzschia spp.; 3. Pseudo-nitzschia spp.; 4. Navicula spp.; 5. Trachyneis aspera; 6. Amphora spp.; 7. Pleurosigma spp.; 8. Entomoneis spp.; 9. Fallacia spp.

48 Plate V

2 1 3

4 6

| 10 µ |

7 8

Figures: 1. Rhizosolenia spp.; 2. Rhizosolenia spp.; 3. Pseudogomphonema spp.; 4. Biddulphia weissflogii; 5. Gramataphora spp.; 6. Achnanthes spp.; 7. Corethron criophilum; 8. Biddulphia spp.

49 Plate VI

1 2 3

3 4 5

| 10 µ |

Figures: 1. Chaetoceros spp.; 2. Chaetoceros spp. rs; 3. Chaetoceros spp. rs; 4. Eucampia Antarctica var. antarctica; 5. Eucampia antarctica var. recta; 6. Eucampia antarctica terminal valve.

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BIOGRAPHICAL SKETCH

In the summer of 1977, Susan Murr Foley completed her Bachelor of Science degree at Tulane University in New Orleans, Louisiana. Under the advisement of Dr. Sherwood W. Wise, she will receive her Master of Science in Geological Sciences in August, 2010, at Florida State University in Tallahassee, Florida.