Palmer LTER
Long-Term Ecological Research (LTER) program—Antarctic Peninsula and the McMurdo Dry Valleys sites Palmer LTER: Patterns of distribution of inorganic macronutrients, phytoplankton pigmentation, and photosynthetic activity in an ice-dominated ecosystem in austral winter 1993 BARBARA SULLIVAN, H. ALLEN MATLICK, and BARBARA PRIZELIN, Marine Primary Productivity Group, Department of
Biological Sciences, University of California, Santa Barbara, Santa Barbara, California 93106
n August and September 1993, we resolved the I mesoscale variability in phytoplankton pigmentation, nutrition, and photosynthetic activity in waters west of the Palmer Peninsula. Procedures have been previously described (Prézelin et al. 1992). Samples were collected at geographically defined stations within a 400- x 200-kilometer (km) portion of the LongTerm Ecological Research (LTER) grid, which is characterized by diverse bottom topography and water-mass movement (Hofmann et al. 1993; Klinck and Smith 1994) and where spring ice coverage varies widely from year to year (Stammerjohn 1994). The grid was largely ice free in early August; soon after, a cold snap resulted in ice coverage over the entire grid area for the duration of the cruise. Figure 1 provides contour plots of the vertical distribution of total plant biomass for each transect line (spaced 100 km apart), as well as chemotaxonomic carotenoid markers for diatoms, prymnesiophytes (largely Phaeocystsis spp.), and chrysophytes. Figure 2 displays the distribution of macronutrients within the same area, and figure 3 presents the results of a simple linear correlation between most of the parameters thus far analyzed. Pigmentation was very dilute in the late winter period. Maximum chlorophyll-a biomass was approximately 250 nanograms per liter (ngIL), or about onefourth that measured for the same region the previous austral fall (March and April 1993, Prézelin unpublished data) and about one-half that measured in the austral spring (November) of 1991 when the region was also heavily ice-covered (Prézelin et al. 1992). Chlorophyll was most abundant at either ends of the transect, with highest concentrations and co-occurrence of all chemotaxonomic pigments occurring at the southern most end of the grid (200 line). Here, offshore waters
gure 1. Uontour plots for phytoplankton pigment concentrations (ngIL) for each LTER grid line sampled during the late austral winter 1993. Sampling shown for chlorophyll-a is identical for all pigments. Note different scales.
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207
Figure 2. Contour plots for inorganic nutrient concentrations (i.tM) tor each LTER grid line. Ammonia samples for stations 200.040, 200.060, and 300.040 were lost. Sampling shown for ammonia is consistent for all nutrients. x z+ 6 E
.2 CL
C a
x
-
Z (n
nitrate phosphate silicate NO3/PO4 0.000 0.042 0.204 0.0331 Si(OH)4/NO3 0.004 0.037 0.015 0.719 10.009 0.948 0.000 0.001 0.006 0.000 0.010 chlorophyll a 0.004 0.110 0.093 0.074 0.001 0.012 but-fucoxanthin 0.000 0.093 0.087 0.117 0.002 0.049 fucoxanthin 0.006 0.061 0.049 0.012 0.001 0.003 hex-fucoxanthin 0.000 0.041 0.044 0.099 0.003 0.064 chlorophyll c 0.006 0.130 0.078 0.030 0.005 0.003 peridinin 0.003 0.095 0.058 0.016 0.002 0.004 prasinoxanthin 0.001 0.042 0.024 0.019 0.003 0.001 diadinoxanthin 0.005 0.078 0.067 0.068 0.002 0.016 diatoxanthin 0.000 0.041 0.035 0.070 0.000 0.039 lutein 0.003 0.002 0.001 0.040 0.017 0.051 chlorophyll b 0.000 0.070 0.038 0.050 0.006 0.012 Pmax 0.019 0.049 0.025 0.013 0.000 0.098 1k 0.011 0.021 0.007 0.014 0.004 0.002
0z 0z
were diatom dominated, and ammonia levels were generally greater than 4 micromolar (.tM). Nitrate and phosphate levels were also uniformly high along the 200 line, whereas levels of silicate were significantly enriched in nearshore waters. Further north along the 300 line, the general pattern of volumetric productivity (Pmax) in the upper 60 meters (not shown) resembled that of chlorophyll distribution. Diatoms dominated surface waters of the shallower inshore waters, but a fairly even mixture of diatoms, prymnesiophytes, and chrysophytes constituted offshore communities with no clear relationship to nutrient distribution. Ammonia was elevated in the middle of the transect; nitrate and phosphate patterns tended to covary but without a discernable pattern; and silicate distribution was concentrated in nearshore deep waters and significantly less in offshore waters. Data from the 400, 500, and 600 lines showed significant coherence with regards to phytoplankton but not inorganic nutrient distribution. Two diatom patches (approximately 20-50 km wide) were apparent in the middle of each transect. The flagellated prymnesiophytes and chrysophytes tend to covary and were more prevalent in offshore waters. Highest photosynthetic activity appeared associated with the diatoms. The availability of surface nutrients was lowest on the 600 line, though a "chimney" of nitrate, phosphate, and silicate seems to occur over a topographical rise in the middle of the transect, a characteristic repeatedly observed on various LTER cruises (Prézelin unpublished data). For the combined database, correlations between pigments (chlorophyll-a, fucoxanthin, but-fucoxanthin, and hex-fucoxanthin) and nutrient concentra-
c (5
(C
0
• c .0
c
8
8
8
C
0.000 0.004 0.878 0.001 0.877 0.663 0.005 0.801 0.916 0.554 0.001 0.294 0.201 0.299 0.139 0.000 0.431 0.351 1 0.411 0.287 10.354 0.000 0.310 0.235 0.246 0.235 0.214 0.224 0.000 0.911 0.798 0.768 0.785 0.289 0.389 0.309 I 0.004 0.463 0.512 0.313 0.535 0.151 0.221 0.240 0.504 0.010 0.232 0.285 0.168 0.293 0.044 0.150 0.099 0.220 0.172 0.004 0.351 0.346 0.258 0.350 0.231 0.243 0.182 0.370 0.250 0.185 0.001 0.217 0.084 0.202 0.017 0.228 0.229t0.1 24 0.157 0.002 0.008 0.163 0.023 0.028 0.019 0.012 0.007 0.002 0.026 0.002 0.046 0.009 0.012 0.01510.038
Figure 3. Linear regression values (r 2) between macronutrients (n>200), phytoplankton pigments (n>200), and photosynthetic parameters (n>67) measured within a 400- x 200-kilometer portion of the Palmer LTER offshore grid during late austral winter 1993. Regressions with r 2 >0.5 are in bold. ANTARCTIC JOURNAL - REVIEW 1994 208
tions (nitrate, phosphate, and silicate) were not significant. Although some significance might be resolved within defined water masses within the database, preliminary findings of high nutrients, low biomass, high assimilation rates, and low carbon-to-nitrogen ratios (Prézelin unpublished data) suggest overall phytoplankton growth was not nutrient-limited but light-limited. One is left asking, however, why distinct phytoplankton communities are evident late in the winter, when successional events would not yet have come into play; whether these early seasonal patterns reflect those left at the end of the last growing season; and whether they will be the prevalent signatures in the upcoming spring/summer season. Our Marine Primary Productivity Group plans to combine the measurements presented here with other LTER datasets to • assess temporal and spatial scales for significant changes in the abundance and diversity of phytoplankton communities within the sampling area, • advance physical-based and optical-based models of primary productivity, and • contribute to ecosystem-based models of trophic interactions within the antarctic food web.
This project was supported by a University of California at Santa Barbara May Company Scholarship to Barbara Sullivan and National Science Foundation grant OCE 93-01322 to Barbara B. Prézelin. Special thanks to B. Boczar, T. Diem, T. Westberry, M. Moline, and the crew of the R/V Polar Duke. (This is LTER contribution number 43.)
References Hofmann, E.E., B.L. Lipphardt, Jr., D.A. Smith, and R.A. Locarnini. 1993. Palmer LTER: Hydrography in the LTER region. Antarctic Journal of the U.S., 28(5), 209-211. Klinck, J.M., and R.C. Smith. 1994. Heat budgets and implications for circulation on the continental shelf west of the Antarctic Peninsula. Abstracts, Proceedings of SCAR Sixth Biology Symposium. Cambridge Press: Scientific Committee on Antarctic Research. [Abstract] Prézelin, B.B., N.P. Boucher, M. Moline, E. Stephens, K. Seydell, and K. Scheppe. 1992. Palmer LTER: Spatial variability in phytoplankton distribution and surface photosynthetic potential within the peninsula grid, November 1991. Antarctic Journal of the U.S., 27(5), 242-245. Stammerjohn, S.E. 1994. Spatial and temporal variability in southern ocean sea ice cover. (Masters of Arts thesis, University of California at Santa Barbara.)
Palmer LTER: Spatial distribution of viruses in the Palmer LTER region ROxANE MARANGER and DAVID F. BIRD, Department of Biology, University of Quebec at Montreal, Montreal,
Quebec H3C 3P8, Canada DAVID M. KARL, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, Hawaii 96822
i ruses have been identified as dynamic components in Vseveral aquatic environments including marine and fresh waters (Bergh et al. 1989; Klut and Stockner 1990; Proctor and Fuhrman 1990), marine and freshwater sediments (Paul et al. 1993; Maranger and Bird unpublished data), and polar sea ice (Maranger, Bird, and Juniper in press). High abundances and rapid changes in viral abundance (Bratbak et al. 1990) along with rapid viral decay rates (Heldal and Bratbak 1991) suggest that viruses may play an important role in controlling microbial populations. Viruses are also thought to be involved in carbon transfer within the microbial loop (Bratbak et al. 1992); however, their quantitative role in carbon and nutrient cycling has not been fully established. Viruses have previously been observed in the southern oceans and abundances have been reported for the Drake Passage (D.C. Smith et al. 1992) and for the coastal waters of Paradise Harbor (Bird, Maranger, and Karl 1993). During cruise 94-01 of the R/V Polar Duke (January 1994), we enumerated viruses from surface water samples taken at each station of the Palmer Long-Term Ecosystem Research (LTER) transect lines 300, 400, 500, and 600 (Waters and Smith 1992). Our objective was to determine onshore-to-offshore gradients in viral abundance and to compare these results with other
physical, chemical, and microbiological characteristics of the surface waters. Viruses were counted in different size classes by head capsid diameter [less than 30 nanometers (nm), 30-60 nm, 60-80 nm, greater than 80 nm) to determine changes in the viral community composition between sites. Depth profiles of virus samples were taken at the endpoint stations (nearest to and farthest from shore) of each transect line. Virus samples were fixed with electron microscopy (EM) grade glutaraldehyde (2.5 percent final concentration), stored in polypropylene vials at 4°C, and prepared on board the R/V Polar Duke as soon as sea conditions were calm. Water samples were concentrated using AMICON microconcentrators (10,000 molecular weight cutoff filter) in a micro centrifuge. Viruses from these concentrated water samples were then pelleted directly onto 400-mesh formvar-coated copper EM-grids using an EM-90 rotor in a Beckman airfuge for 30 minutes at 100,000 x g. Once removed, the grids were floated on a drop of filtered (0.02-micrometer) distilled water to remove salts. Grids were stained with uranyl acetate (2 percent final concentration) for 30 minutes. Viruses were counted directly by transmission electron microscopy at high magnification (90,000x). Virus particles were identified on the basis of shape, size, and staining properties. Our criteria for virus
ANTARCTIC JOURNAL - REVIEW 1994 209
Biological Sciences, University of California, Santa Barbara, Santa Barbara, California 93106
n August and September 1993, we resolved the I mesoscale variability in phytoplankton pigmentation, nutrition, and photosynthetic activity in waters west of the Palmer Peninsula. Procedures have been previously described (Prézelin et al. 1992). Samples were collected at geographically defined stations within a 400- x 200-kilometer (km) portion of the LongTerm Ecological Research (LTER) grid, which is characterized by diverse bottom topography and water-mass movement (Hofmann et al. 1993; Klinck and Smith 1994) and where spring ice coverage varies widely from year to year (Stammerjohn 1994). The grid was largely ice free in early August; soon after, a cold snap resulted in ice coverage over the entire grid area for the duration of the cruise. Figure 1 provides contour plots of the vertical distribution of total plant biomass for each transect line (spaced 100 km apart), as well as chemotaxonomic carotenoid markers for diatoms, prymnesiophytes (largely Phaeocystsis spp.), and chrysophytes. Figure 2 displays the distribution of macronutrients within the same area, and figure 3 presents the results of a simple linear correlation between most of the parameters thus far analyzed. Pigmentation was very dilute in the late winter period. Maximum chlorophyll-a biomass was approximately 250 nanograms per liter (ngIL), or about onefourth that measured for the same region the previous austral fall (March and April 1993, Prézelin unpublished data) and about one-half that measured in the austral spring (November) of 1991 when the region was also heavily ice-covered (Prézelin et al. 1992). Chlorophyll was most abundant at either ends of the transect, with highest concentrations and co-occurrence of all chemotaxonomic pigments occurring at the southern most end of the grid (200 line). Here, offshore waters
gure 1. Uontour plots for phytoplankton pigment concentrations (ngIL) for each LTER grid line sampled during the late austral winter 1993. Sampling shown for chlorophyll-a is identical for all pigments. Note different scales.
ANTARCTIC JOURNAL - REVIEW 1994
207
Figure 2. Contour plots for inorganic nutrient concentrations (i.tM) tor each LTER grid line. Ammonia samples for stations 200.040, 200.060, and 300.040 were lost. Sampling shown for ammonia is consistent for all nutrients. x z+ 6 E
.2 CL
C a
x
-
Z (n
nitrate phosphate silicate NO3/PO4 0.000 0.042 0.204 0.0331 Si(OH)4/NO3 0.004 0.037 0.015 0.719 10.009 0.948 0.000 0.001 0.006 0.000 0.010 chlorophyll a 0.004 0.110 0.093 0.074 0.001 0.012 but-fucoxanthin 0.000 0.093 0.087 0.117 0.002 0.049 fucoxanthin 0.006 0.061 0.049 0.012 0.001 0.003 hex-fucoxanthin 0.000 0.041 0.044 0.099 0.003 0.064 chlorophyll c 0.006 0.130 0.078 0.030 0.005 0.003 peridinin 0.003 0.095 0.058 0.016 0.002 0.004 prasinoxanthin 0.001 0.042 0.024 0.019 0.003 0.001 diadinoxanthin 0.005 0.078 0.067 0.068 0.002 0.016 diatoxanthin 0.000 0.041 0.035 0.070 0.000 0.039 lutein 0.003 0.002 0.001 0.040 0.017 0.051 chlorophyll b 0.000 0.070 0.038 0.050 0.006 0.012 Pmax 0.019 0.049 0.025 0.013 0.000 0.098 1k 0.011 0.021 0.007 0.014 0.004 0.002
0z 0z
were diatom dominated, and ammonia levels were generally greater than 4 micromolar (.tM). Nitrate and phosphate levels were also uniformly high along the 200 line, whereas levels of silicate were significantly enriched in nearshore waters. Further north along the 300 line, the general pattern of volumetric productivity (Pmax) in the upper 60 meters (not shown) resembled that of chlorophyll distribution. Diatoms dominated surface waters of the shallower inshore waters, but a fairly even mixture of diatoms, prymnesiophytes, and chrysophytes constituted offshore communities with no clear relationship to nutrient distribution. Ammonia was elevated in the middle of the transect; nitrate and phosphate patterns tended to covary but without a discernable pattern; and silicate distribution was concentrated in nearshore deep waters and significantly less in offshore waters. Data from the 400, 500, and 600 lines showed significant coherence with regards to phytoplankton but not inorganic nutrient distribution. Two diatom patches (approximately 20-50 km wide) were apparent in the middle of each transect. The flagellated prymnesiophytes and chrysophytes tend to covary and were more prevalent in offshore waters. Highest photosynthetic activity appeared associated with the diatoms. The availability of surface nutrients was lowest on the 600 line, though a "chimney" of nitrate, phosphate, and silicate seems to occur over a topographical rise in the middle of the transect, a characteristic repeatedly observed on various LTER cruises (Prézelin unpublished data). For the combined database, correlations between pigments (chlorophyll-a, fucoxanthin, but-fucoxanthin, and hex-fucoxanthin) and nutrient concentra-
c (5
(C
0
• c .0
c
8
8
8
C
0.000 0.004 0.878 0.001 0.877 0.663 0.005 0.801 0.916 0.554 0.001 0.294 0.201 0.299 0.139 0.000 0.431 0.351 1 0.411 0.287 10.354 0.000 0.310 0.235 0.246 0.235 0.214 0.224 0.000 0.911 0.798 0.768 0.785 0.289 0.389 0.309 I 0.004 0.463 0.512 0.313 0.535 0.151 0.221 0.240 0.504 0.010 0.232 0.285 0.168 0.293 0.044 0.150 0.099 0.220 0.172 0.004 0.351 0.346 0.258 0.350 0.231 0.243 0.182 0.370 0.250 0.185 0.001 0.217 0.084 0.202 0.017 0.228 0.229t0.1 24 0.157 0.002 0.008 0.163 0.023 0.028 0.019 0.012 0.007 0.002 0.026 0.002 0.046 0.009 0.012 0.01510.038
Figure 3. Linear regression values (r 2) between macronutrients (n>200), phytoplankton pigments (n>200), and photosynthetic parameters (n>67) measured within a 400- x 200-kilometer portion of the Palmer LTER offshore grid during late austral winter 1993. Regressions with r 2 >0.5 are in bold. ANTARCTIC JOURNAL - REVIEW 1994 208
tions (nitrate, phosphate, and silicate) were not significant. Although some significance might be resolved within defined water masses within the database, preliminary findings of high nutrients, low biomass, high assimilation rates, and low carbon-to-nitrogen ratios (Prézelin unpublished data) suggest overall phytoplankton growth was not nutrient-limited but light-limited. One is left asking, however, why distinct phytoplankton communities are evident late in the winter, when successional events would not yet have come into play; whether these early seasonal patterns reflect those left at the end of the last growing season; and whether they will be the prevalent signatures in the upcoming spring/summer season. Our Marine Primary Productivity Group plans to combine the measurements presented here with other LTER datasets to • assess temporal and spatial scales for significant changes in the abundance and diversity of phytoplankton communities within the sampling area, • advance physical-based and optical-based models of primary productivity, and • contribute to ecosystem-based models of trophic interactions within the antarctic food web.
This project was supported by a University of California at Santa Barbara May Company Scholarship to Barbara Sullivan and National Science Foundation grant OCE 93-01322 to Barbara B. Prézelin. Special thanks to B. Boczar, T. Diem, T. Westberry, M. Moline, and the crew of the R/V Polar Duke. (This is LTER contribution number 43.)
References Hofmann, E.E., B.L. Lipphardt, Jr., D.A. Smith, and R.A. Locarnini. 1993. Palmer LTER: Hydrography in the LTER region. Antarctic Journal of the U.S., 28(5), 209-211. Klinck, J.M., and R.C. Smith. 1994. Heat budgets and implications for circulation on the continental shelf west of the Antarctic Peninsula. Abstracts, Proceedings of SCAR Sixth Biology Symposium. Cambridge Press: Scientific Committee on Antarctic Research. [Abstract] Prézelin, B.B., N.P. Boucher, M. Moline, E. Stephens, K. Seydell, and K. Scheppe. 1992. Palmer LTER: Spatial variability in phytoplankton distribution and surface photosynthetic potential within the peninsula grid, November 1991. Antarctic Journal of the U.S., 27(5), 242-245. Stammerjohn, S.E. 1994. Spatial and temporal variability in southern ocean sea ice cover. (Masters of Arts thesis, University of California at Santa Barbara.)
Palmer LTER: Spatial distribution of viruses in the Palmer LTER region ROxANE MARANGER and DAVID F. BIRD, Department of Biology, University of Quebec at Montreal, Montreal,
Quebec H3C 3P8, Canada DAVID M. KARL, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, Hawaii 96822
i ruses have been identified as dynamic components in Vseveral aquatic environments including marine and fresh waters (Bergh et al. 1989; Klut and Stockner 1990; Proctor and Fuhrman 1990), marine and freshwater sediments (Paul et al. 1993; Maranger and Bird unpublished data), and polar sea ice (Maranger, Bird, and Juniper in press). High abundances and rapid changes in viral abundance (Bratbak et al. 1990) along with rapid viral decay rates (Heldal and Bratbak 1991) suggest that viruses may play an important role in controlling microbial populations. Viruses are also thought to be involved in carbon transfer within the microbial loop (Bratbak et al. 1992); however, their quantitative role in carbon and nutrient cycling has not been fully established. Viruses have previously been observed in the southern oceans and abundances have been reported for the Drake Passage (D.C. Smith et al. 1992) and for the coastal waters of Paradise Harbor (Bird, Maranger, and Karl 1993). During cruise 94-01 of the R/V Polar Duke (January 1994), we enumerated viruses from surface water samples taken at each station of the Palmer Long-Term Ecosystem Research (LTER) transect lines 300, 400, 500, and 600 (Waters and Smith 1992). Our objective was to determine onshore-to-offshore gradients in viral abundance and to compare these results with other
physical, chemical, and microbiological characteristics of the surface waters. Viruses were counted in different size classes by head capsid diameter [less than 30 nanometers (nm), 30-60 nm, 60-80 nm, greater than 80 nm) to determine changes in the viral community composition between sites. Depth profiles of virus samples were taken at the endpoint stations (nearest to and farthest from shore) of each transect line. Virus samples were fixed with electron microscopy (EM) grade glutaraldehyde (2.5 percent final concentration), stored in polypropylene vials at 4°C, and prepared on board the R/V Polar Duke as soon as sea conditions were calm. Water samples were concentrated using AMICON microconcentrators (10,000 molecular weight cutoff filter) in a micro centrifuge. Viruses from these concentrated water samples were then pelleted directly onto 400-mesh formvar-coated copper EM-grids using an EM-90 rotor in a Beckman airfuge for 30 minutes at 100,000 x g. Once removed, the grids were floated on a drop of filtered (0.02-micrometer) distilled water to remove salts. Grids were stained with uranyl acetate (2 percent final concentration) for 30 minutes. Viruses were counted directly by transmission electron microscopy at high magnification (90,000x). Virus particles were identified on the basis of shape, size, and staining properties. Our criteria for virus
ANTARCTIC JOURNAL - REVIEW 1994 209
