Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Parameters
• Instruments
• Project Information
• Funding

This dataset contains abundance and size distribution of marine snow aggregates from profiles conducted during R/V Polar Star cruises in the Ross Sea, Antarctica between 2001 and 2005.

Related dataset (collected during the same profiles):
IVARS Phaeocystis: https://www.bco-dmo.org/dataset/768570

Methodology:

A marine snow imaging system was lowered through the water column to acquire photographs of aggregates. The imaging system consisted of a collimated strobe system and either a 35-mm film camera (Lobsiger Deepslope 6000; Years 1 - 3) or a digital camera (Insite Pacific Scorpio; Year 4) mounted on an aluminum frame. The system was lowered at a rate of 10 m min-1 through the water column, acquiring ca. six images min-1 at an interval of ca. 1.7 m throughout the entire water column. Illumination was provided by a pair of strobe lights (Deep Sea Power and Light) positioned to produce an 8.4-cm deep beam of uniform, collimated light 66 or 79 cm from the camera lens (Fig. 2). Aggregates larger than 0.5 mm within this volume (3 - 15 L, depending on the camera, lens and resultant geometry) are quantified from images taken by a camera that is mounted perpendicular to the long axis of the light beam, which can subsequently be distinguished and quantified by digital analysis. Ambient light illuminates particles in front of and behind this light beam and invalidates the calculation of illuminated volume. Thus, profiles were obtained near local midnight whenever possible (24-h photoperiods occurred throughout all cruises) to minimize this interference; images with the frame visible, due to ambient light, were discarded. The depth of first aggregate counts ranged from 30 - 88 m (a function of water clarity and solar angle). A Sea-Bird SeaCat CTD and 25-cm SeaTech transmissometer mounted on the camera frame provided continuous measurements of temperature, salinity and optical transmission. These data were used to calculate the depth at which each image was acquired. All film (Tmax 400) and images were returned to the laboratory for processing except for short sections viewed at sea to assess camera operation. The films were developed and then digitized to JPG format either in house, using a Nikon camera and macro lens (3767 x 2368), or commercially (3544 x 2341).

The images were analyzed with Image Pro Plus, with a final resolution of the digitized images (2048 x 1536 pixels) of 4.2 pixels mm-1. Digital images were analyzed directly with a final resolution of 4.2 Pixels mm-1. To insure that the same portion of each image was analyzed, an area of Interest (AOI) was created within the region of maximum illumination. This AOI was positioned to the same location within each image before particles were counted.

BCO-DMO Data Manager Processing Notes:
* station information added to marine snow data from separate Excel spreadsheet.
* various date formats in the date column changed to ISO 8601 (yyyy-mm-dd)
* longitude was decimal degrees with directional (W E), corrected so longitude negative for W, positive for E.
* replaced comma in station comment with ; to better support export as csv format
* removed padded whitespaces
From originally submitted profiles in individual Excel sheets:
* copied and pasted contests of sheets (contained data by profile) into two separate tables to concatenate all the profiles together. Split into two "datasets" for marine snow and Phaeocystis ghost colonies.
* Some sheets in the original file had two separate tables in each of the sheets (for profiles that didn't have canister letter). Separate datasets made for particles per liter and ghost colonies.
* Changed column names so they could be imorted into BCO-DMO data system (column names can't start with number or contain > or - characters. e.g. column named "0.0 - 0.5" changed to "bin_0_0_to_0_5" and "> 2.5 - 3.0" changed to "bin_gt_2_5_to_3_0"

version 2 (2019-06-12) replaces version 1 (2019-05-28):
* The latitude and longitude maximum and minimum bounds updated. The latitude changed to negative values. The latitude and longitude in the dataset itself remain unchanged as they were accurate.

NSF Award Abstract:
During the past few decades of oceanographic research, it has been recognized that significant variations in biogeochemical processes occur among years. Interannual variations in the Southern Ocean are known to occur in ice extent and concentration, in the composition of herbivore communities, and in bird and marine mammal distributions and reproductive success. However, little is known about the interannual variations in production of phytoplankton or the role that these variations play in the food web. This project will collect time series data on the seasonal production of phytoplankton in the southern Ross Sea, Antarctica. Furthermore, it will assess the interannual variations of the production of the two major functional groups of the system, diatoms and Phaeocystis Antarctica, a colonial haptophyte. The Ross Sea provides a unique setting for this type of investigation for a number of reasons. For example, a de facto time-series has already been initiated in the Ross Sea through the concentration of a number of programs in the past ten years. It also is well known that the species diversity is reduced relative to other systems and its seasonal production is as great as anywhere in the Antarctic. Most importantly, seasonal production of both the total phytoplankton community (as well as its two functional groups) can be estimated from late summer nutrient profiles. The project will involve short cruises on the US Coast Guard ice breakers in the southern Ross Sea that will allow the collection of water column nutrient and particulate after data at specific locations in the late summer of each of five years. Additionally, two moorings with in situ nitrate analyzers moored at fifteen will be deployed, thus collecting for the first time in the in the Antarctic a time-series of euphotic zone nutrient concentrations over the entire growing season. All nutrient data will be used to calculate seasonal production for each year in the southern Ross Sea and compared to previously collected information, thereby providing an assessment of interannual variations in net community production. Particulate matter data will allow us to estimate the amount of export from the surface layer by late summer, and therefore calculate the interannual variability of this ecosystem process. Interannual variations of seasonal production (and of the major taxa of producers) are a potentially significant feature in the growth and survival of higher trophic levels within the food web of the Ross Sea. They are also important in order to understand the natural variability in biogeochemical processes of the region. Because polar regions such as the Ross Sea are predicted to be impacted by future climate change, biological changes are also anticipated. Placing these changes in the context of natural variability is an essential element of understanding and predicting such alterations. This research thus seeks to quantify the natural variability of an Antarctic coastal system, and ultimately understand its causes and impacts on food webs and biogeochemical cycles of the Ross Sea.

Related publications:
Smith, W.O., Jr., M.S. Dinniman, J.M. Klinck, and E. Hofmann. 2003. Biogeochemical climatologies in the Ross Sea, Antarctica: seasonal patterns of nutrients and biomass. Deep-Sea Res. II 50: 3083-3101.

Smith, W.O., Jr., A.R. Shields, J.A. Peloquin, G. Catalano, S. Tozzi, M.S. Dinniman and V.A. Asper. 2006. Biogeochemical budgets in the Ross Sea:  variations among years. Deep-Sea Res. II 53: 815-833.

Tremblay, J.-E. and W.O. Smith, Jr.  2007. Phytoplankton processes in polynyas.  In:  Polynyas: Windows to the World’s Oceans (W.O. Smith, Jr. and D.G. Barber, eds.), Elsevier, Amsterdam, Pp. 239-270.

Smith, W.O. Jr. and D.G. Barber (Eds.).  2007. Polynyas: Windows to the World’s Oceans. Elsevier, Amsterdam. 437 pp.

Smith, W.O. Jr. and D.G. Barber. 2007. Polynyas and climate change: a view to the future.  In: Polynyas: Windows to the World’s Oceans (W.O. Smith, Jr. and D.G. Barber, eds.), Elsevier, Amsterdam, Pp. 409-417.

Smith, W.O. Jr., D.G. Ainley and R. Cattaneo-Vietti. 2007. Trophic interactions within the Ross Sea continental shelf ecosystem. Phil. Trans. Roy. Soc., ser. B 362: 95-111.

Peloquin, J. A., and W. O. Smith, Jr.  2007. Phytoplankton blooms in the Ross Sea, Antarctica: Interannual variability in magnitude, temporal patterns, and composition. J. Geophys. Res. 112: C08013, doi:10.1029/2006JC003816.

Smith, W.O. Jr. and J.C. Comiso. 2009. Southern Ocean primary productivity: variability and a view to the future. In Smithsonian at the Poles: Contributions to International Polar Year Science (I. Krupnik, M.A. Lang, and S.E. Miller, Eds.), Smithsonian Inst. Scholarly Press, Washington, D.C., pp. 309-318.

Smith, W.O. Jr., M. Dinniman, G.R. DiTullio, S. Tozzi, O. Mangoni, M. Modigh and V. Saggiomo. 2010. Phytoplankton photosynthetic pigments in the Ross Sea: Patterns and relationships among functional groups. J. Mar. Systems 82: 177-185.

Smith, W.O. Jr., V. Asper, S. Tozzi, X. Liu and S.E. Stammerjohn. 2011a. Surface layer variability in the Ross Sea, Antarctica as assessed by in situ fluorescence measurements. Prog. Oceanogr.  88: 28-45 (doi: 10.1016/j.pocean.2010.08.002).

Smith, W.O. Jr., A.R. Shields, J. Dreyer, J.A. Peloquin and V. Asper. 2011b. Interannual variability in vertical export in the Ross Sea: magnitude, composition, and environmental correlates. Deep-Sea Res. I 58: 147-159.

Liu, X. and W.O. Smith, Jr.  2012. A statistical analysis of the controls on phytoplankton distribution in the Ross Sea, Antarctica. J. Mar. Systems 94: 135-144.

Smith, W.O. Jr., P.N. Sedwick, K.R. Arrigo, D.G. Ainley, and A.H. Orsi. 2012. The Ross Sea in a sea of change. Oceanography 25: 44-57.

Peloquin, J., C. Swan, N. Gruber, M. Vogt, H. Claustre, J. Ras, J. Uitz, J-C. Marty, R. Barlow, M. Behrenfeld, R. Bidigare, H. Dierssen, G. DiTullio, E. Fernandez, C. Gallienne, S. Gibb, R. Goericke, L. Harding, E. Head, P. Holligan, S. Hooker, D. Karl, T. Knap, M. Landry, R. Letelier, C.A. Llewellyn, M. Lomas, M. Lucas, A. Mannino, J.-C. Marty, B. G. Mitchell, F. Müller-Karger, N. Nelson, C. O'Brien, B. Prezelin, D. Repeta, W. O. Smith, Jr., D. Smythe-Wright, R. Stumpf, A. Subramaniam, K. Suzuki, C. Trees, M. Vernet, K. Wasmund, and S. Wright. 2014. The MAREDAT global database of high performance liquid chromatography marine pigment measurements.  Earth System Science Data 5: 109-123.

Smith, W.O. Jr., D.G. Ainley, K.R. Arrigo, and M.S. Dinniman. 2014. The oceanography and ecology of the Ross Sea.  Annu. Rev. Mar. Sci. 6: 469-487.

Smith, W.O., Jr. and K. Donaldson. 2015. Photosynthesis-irradiance responses in the Ross Sea, Antarctica: a meta-analysis. Biogeosciences 12: 1-11.

Asper, V.L. and W.O. Smith, Jr. Variations in the abundance and distribution of aggregates in the Ross Sea, Antarctica. Deep-Sea Res. I (submitted).

Smith, W.O., Jr. and D.E. Kaufman. Particulate organic carbon climatologies in the Ross Sea: evidence for seasonal acclimations within phytoplankton. Prog. Oceanogr. (submitted).