Smithsonian at the Poles: Contributions to International Polar

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concentrations are lower and the water column is more deeply mixed. As is typical of polar regions, the massive phytoplankton production that is observed during the early stages of this bloom (in the early to mid austral spring) is not accompanied by signifi cant micro- or macrozooplankton grazing (Caron et al., 2000). The spring bloom also appears to be a period of low bacterial abundance and activity (Ducklow et al., 2001), although bacteria do bloom during the later stages of the algal bloom, in early to mid summer, coinciding with an increase in dissolved and particulate organic carbon (Carlson et al., 2000). Depending on physiological and hydrodynamic factors, this ecological decoupling between primary productivity and both microbial productivity and grazing may cause the phytoplankton to sink out of the photic zone (DiTullio et al., 2000; Becquevort and Smith, 2001; Overland and Stabeno, 2004). This may lead to a signifi cant fl ux of organic matter to the ocean fl oor and to deepwater CDOM production. Export of the phytoplankton out of the photic zone may also lead to a decoupling of bloom dynamics and CDOM cycling. Here we report on spatial and temporal patterns in CDOM spectra observed during the early stages of the 2005 austral spring Phaeocystis antarctica bloom in the seasonal Ross Sea polynya. Our results show that CDOM changed very little during a period when chl a concentrations increased more than one-hundred-fold. Implications of this fi nding for CDOM cycling in the Ross Sea are discussed. METHODS ROSS SEA SITE DESCRIPTION AND SAMPLING A fi eld campaign was conducted aboard the R/V Nathaniel B. Palmer in the seasonal ice-free polynya in the Ross Sea, Antarctica, from 8 November to 30 November 2005 (Figure 1). During this time, the surface seawater temperature was approximately – 1.8°C and the phytoplankton assemblage was dominated by colonial Phaeocystis antarctica. Three main hydrographic stations were occupied within the Ross Sea polynya for approximately seven days each (i.e., R10, R13, R14). Seawater samples were collected from early morning hydrocasts (0400-0700 local time) directly from Niskin bottles attached to a conductivity, temperature, and depth (CTD) rosette. Vertical profi les of a suite of routine measurements were obtained at each station including downwelling irradiance (and coupled incident surface irradiance), chl a, and CDOM absorption spectra. Additionally, a profi le of dissolved organic carbon (DOC) was collected at one station (14F). CHROMOPHORIC DISSOLVED ORGANIC MATTER CYCLING 321 FIGURE 1. Locations of transect sampling stations south of New Zealand to the Ross Sea (open circles) and the main hydrographic stations that were occupied in the Ross Sea (solid black circles) during the NBP05-08 cruise. Latitude and longitude information for specifi c hydrographic stations (e.g., R10A and R10D) are given in fi gure captions 4, 5, 8 and 9. In addition to studying CDOM cycling in the Ross Sea, we also collected and analyzed surface water CDOM samples during our North-South transit from New Zealand through the Southern Ocean to the Ross Sea (28 October– 7 November, 2005). Transect sampling for CDOM was conducted from �49 to �75°S. Details of the cruise track, sampling protocols, analyses conducted and meteoro logical and sea ice conditions for the southbound transect are presented in Kiene et al. (2007). The transect encompassed open waters of the Southern Ocean, the northern sea-ice melt zone, and ice-covered areas near the northern Ross Sea. Chlorophyll a was determined fl uorometrically by employing the acidifi cation method described by Strickland and Parsons (1968). Briefl y, 50– 250 mL of seawater was fi ltered onto a 25-mm GF/C glass fi ber fi lter (Whatman Inc., Floram Park, New Jersey) with low vacuum. Filters were placed in 5 mL of 90% HPLC-grade acetone and extracted for 24 h at – 20°C. Chlorophyll fl uorescence in the acetone extracts was quantifi ed with a Turner Designs 10-AU fl uorometer (Sunnyvale, Calafornia) before and after 80-�L addition of 10% HCl. Dissolved organic carbon samples were
322 SMITHSONIAN AT THE POLES / KIEBER, TOOLE, AND KIENE collected and concentrations were determined by employing the techniques outlined in Qian and Mopper (1996). For nutrient and CDOM samples, seawater was collected directly from Niskin bottles by gravity fi ltration through a 20-�m Nitex mesh (held in a 47-mm-diameter polycarbonate (PC) fi lter holder) followed by a precleaned 0.2-�m AS 75 Polycap fi lter capsule (nylon membrane with a glass microfi ber prefi lter enclosed in a polypropylene housing). Silicone tubing was used to attach the PC fi lter to the Niskin bottle spigot and the Polycap to the PC fi lter outlet. Nutrient samples were collected into 50-mL polypropylene centrifuge tubes, while samples for CDOM were fi ltered into precleaned 80-mL Qorpak bottles sealed with Tefl on-lined caps (see Toole et al., 2003, for details regarding sample fi ltration and glassware preparation). Nutrient samples were stored frozen at �80°C until shipboard analysis by standard fl ow-injection techniques. CDOM ABSORPTION SPECTRA Absorbance spectra were determined with 0.2-�m fi ltered seawater samples that were warmed to room temperature in the dark immediately after they were collected and then analyzed soon thereafter (generally within 24 h). Absorbance spectra were determined in a 100-cm path length, Type II liquid capillary waveguide (World Precision Instruments) attached to an Ocean Optics model SD2000 dual-channel fi ber-optic spectrophotometer and a Micropack DH 2000 UV-visible light source. Prior to analysis, a sample or blank was fi rst deaerated with ultrahigh purity He in an 80-mL Qorpak bottle and then pulled through the capillary cell slowly with a Rainin Rabbit peristaltic pump. Deaeration with He eliminated bubble formation in the sample cell, while increasing the pH slightly from 8.0 to 8.3. This pH change is not expected to affect absorption spectra, although this was not explicitly tested. The reference solution consisted of 0.2-�m-fi ltered 0.7-M NaCl prepared from precombusted (600°C, 24 h) high-purity sodium chloride (99.8%, Baker Analyzed) and dissolved in high-purity (18.2 M� cm) laboratory water obtained from a Millipore Milli-Q ultrapure water system (Millipore Corp., Billerica, Massachusetts). The sodium chloride solution was used to approximately match the ionic strength of the Ross Sea seawater samples and minimize spectral offsets due to refractive index effects. Even though a sodium chloride solution was used as a reference, sample absorbance spectra still exhibited small, variable baseline offsets (�0.005 AU). This was corrected for by adjusting the absorbance (Aλ) to zero between 650 and 675 nm where the sample absorbance was assumed to be zero. The capillary cell was fl ushed after every fourth or fi fth seawater sample with deaerated Milli-Q water and high-purity, distilled-in-glass-grade methanol (Burdick and Jackson, Muskegon, Michigan). Corrected absorbance values were used to calculate absorption coeffi cients: aλ � 2.303Aλ / l, (1) where l is the path length of the capillary cell. Each sample was analyzed in triplicate, resulting in �2% relative standard deviation (RSD) in spectral absorbance values �400 nm. On the basis of three times the standard deviation of the sodium chloride reference, the limit of detection for measured absorption coeffi cients was approximately 0.002 m �1 . To characterize sample absorption, spectra were fi t to the following exponential form (e.g., Twardowski et al., 2004): aλ � aλ o e �S(λ– λo) , (2) where aλ o is the absorption coeffi cient at the reference wavelength, λo, and S is the spectral slope (nm �1 ). Data were fi t to a single exponential equation using SigmaPlot (SPSS Inc.). Slope coeffi cients were evaluated from 275 to 295 nm (S275–295; λo � 285 nm) and from 350 to 400 nm (S350–400; λo � 375 nm). These wavelength ranges were selected for study of spectral slopes instead of using broader wavelength ranges (e.g., 290– 700 nm) because the former can be measured with high precision and better refl ects biogeochemical changes in CDOM in the water column (Helms et al., 2008). OPTICAL PROFILES Vertical profi les of spectral downwelling irradiance (Ed(z,λ)) and upwelling radiance (Lu(z,λ)), as well as the time course of surface irradiance (Ed(0 � ,λ, t)), were determined separately for ultraviolet and visible wavebands. Ultraviolet wavelengths were sampled using a Biospherical Instruments, Inc. (BSI, San Diego, California) PUV-2500 Profi ling Ultraviolet Radiometer coupled with a continuously sampling, deck-mounted, cosine-corrected GUV- 2511 Ground-based Ultraviolet Radiometer. Both sensors had a sampling rate of approximately 6 Hz and monitored seven channels centered at 305, 313, 320, 340, 380, and 395 nm, as well as integrated photosynthetically active radiation (PAR). Each channel had an approximate bandwidth of 10 nm, except for the 305-nm channel, whose bandwidth was determined by the atmospheric ozone cutoff and the PAR channel, which monitored the irradiance
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Smithsonian at the Poles Contributi
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Contents FOREWORD by Ira Rubinoff i
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Elaina Jorgensen, Alaska Fisheries
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CONTENTS vii Watching Star Birth fr
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x SMITHSONIAN AT THE POLES blooms i
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xii SMITHSONIAN AT THE POLES Change
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xiv SMITHSONIAN AT THE POLES Museum
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Advancing Polar Research and Commun
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James P. Espy (1785- 1860), the fi
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ology fueled hopes that the scienti
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Meteorologists also provided critic
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visualize weather patterns remotely
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in ice sheets. The latest collapse
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Cooperation at the Poles? Placing t
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British Association for the Advance
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cations, in which the Smithsonian s
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ence” (Robinson, 2006: 76), he ha
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Taylor, C. J. 1981. First Internati
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24 SMITHSONIAN AT THE POLES / KORSM
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36 SMITHSONIAN AT THE POLES / De VO
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From Ballooning in the Arctic to 10
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ern Svalbard in 1896 (Capelotti, 19
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FIGURE 2. The Andrée campsite in 1
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National Zoo in Washington, D.C.—
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FROM BALLOONING TO 10,000-FOOT RUNW
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e rapidly deployed to South America
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“Of No Ordinary Importance”: Re
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1942). Ethnological collecting had
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group. More importantly, Murdoch’
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gan to study the question of Indian
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small museums and culture centers i
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fer of Alaskan objects and informat
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fi rst time in polar research— di
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Boas, Franz. 1888a. “The Central
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Lindsay, Debra. 1993. Science in th
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80 SMITHSONIAN AT THE POLES / FIENU
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90 SMITHSONIAN AT THE POLES / BURCH
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100 SMITHSONIAN AT THE POLES / CROW
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From Tent to Trading Post and Back
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in befriending an extraordinary Inu
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The Smithsonian Institution’s pre
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of departure for research during th
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FIGURE 8. A drawing of the so-calle
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situated experiential education and
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the Past: Archaeologists, Native Am
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130 SMITHSONIAN AT THE POLES / KRUP
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144 SMITHSONIAN AT THE POLES / PARK
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Brooding and Species Diversity in t
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iefl y consider below some of the i
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ment. Consequently, the selective e
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ated from the Antarctic. Strong cur
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the four main genera of brooding sc
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ing such cryptic speciation suggest
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LITERATURE CITED Absher, T. M., G.
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Madon-Senez, C. 1998. Disparité Mo
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Persistent Elevated Abundance of Oc
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ABUNDANCE OF ANTARCTIC OCTOPODS 199
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206 SMITHSONIAN AT THE POLES / WINS
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Considerations of Anatomy, Morpholo
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Many theories have been hypothesize
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FIGURE 4. A three dimensional recon
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are wider and more bulbous in the a
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mimicked the shape and profi le of
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faces for SEM observation. The spec
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DISCUSSION Imaging and dissection o
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out its length. The pulp chamber al
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pulpal neurons and dentin tubules.
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Scientifi c Diving Under Ice: A 40-
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TABLE 2. Principal Investigators an
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attaching ice anchors to the chunks
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dumping of weight under water. The
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MARINE LIFE HAZARDS Few polar anima
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Urine should be copious and clear a
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Environmental and Molecular Mechani
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face (�1.8°C) are likely to pose
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FIGURE 2. Illustrated selection shi
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FIGURE 4. Distribution of respirati
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invertebrates were placed in the ba
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Meehan, R. R., D. S. Dunican, A. Ru
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266 SMITHSONIAN AT THE POLES / KOOY
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268 SMITHSONIAN AT THE POLES / KOOY
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Page 352 and 353: Capital Expenditure and Income (For
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372 SMITHSONIAN AT THE POLES / MART
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374 SMITHSONIAN AT THE POLES / WALK
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Watching Star Birth from the Antarc
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STAR BIRTH FROM THE ANTARCTIC PLATE
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is constructing and deploying the P
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Antarctic Meteorites: Exploring the
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at the Field Museum, and pieces wer
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the description and curation of Ant
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led these committees throughout the
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Index AAUS. See American Academy of
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temperature, 350-355 tourism, 354 B
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Fishing. See also Biological invasi
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McMurdo Station, xiv, 265-267, 393
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Rogick, Mary, 206 Ronne, Finn, 55 R
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U.S. Naval Support Force Antarctica
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