Ciliates and nanophytoplankton in Arthur Harbor ...
Ciliates and nanophytoplankton in Arthur Harbor, December 1984 and January 1985 J.F. HEINBOKEL and D.W. COATS Chesapeake Bay Institute Johns Hopkins University Shady Side, Maryland 20764
We have been engaged recently in research to define the significance of the microzooplankton in antarctic waters. These studies began in 1983 on a cruise to the Weddell Sea during which we studied the abundance and the reproductive (division) frequencies and periodicities of the tintinnids, a group of planktonic ciliates (Heinbokel and Coats 1984). In 1984 - 1985 we continued these studies at the Palmer Station (64°46'S 64°3W). Our studies were broadened last season to include definition of the entire ciliate assemblage in the waters of Arthur Harbor and definition of the phytoplankton population on the basis of size-fractionated (less than 5 micrometer, less than 10 micrometer, less than 20 micrometer, and total) chlorophyll a determinations. In addition, we continued the studies of ciliate reproduction begun the previous year. Sample analysis was largely completed while at Palmer Station. Data anlaysis is still incomplete, but general results are clear now. Our research during the 1984 - 1985 field season both confirmed our findings from the 1983 cruise in the Weddell Sea (Heinbokel and Coats 1984) and supported our suppositions concerning the numerical importance of the ciliate and nanophytoplankton assemblages. Five 24-hour stations were occupied in or near Arthur Harbor at approximately weekly intervals from 14 December 1984 through 10 January 1985. Samples were obtained at regular intervals from three depths: surface, 10 meters, and 20 meters. Water samples were sizefractionated using 10- and 20-micrometer Nitex mesh and 5micrometer Nuclepore filters prior to fluorometric analysis of chlorophyll a; ciliates in "whole water" samples were fixed and preserved in basic Lugol's fixative (iodine/potassium iodide) prior to enumeration using an inverted microscope. Net tows (35-micrometer mesh) were taken vertically from 20 meters to the surface to collect tintinnids for analysis of the frequency of dividing cells. Sample analyses for the first four stations were ompleted at Palmer Station; those data are summarized in the accompanying table. Tabulated data are presented as station averages for the purpose of this discussion, although the detailed and interesting points concerning depth distributions and diel effects are lost with such an approach. A more detailed discussion will be prepared when station 5 samples have been analyzed. Even at this level of analysis, however, several points are striking. As in the 1983 samples, there was no indication that tintinnine reproduction was phased over the diel cycle. Frequencies of dividing cells ranged approximately between 12 and 22 percent for Cymatocylis spp. and between 30 and 50 percent for the other two species of tintinnines studied. Division frequencies for all three species generally increased as the period of study (December and January) progressed. Observed frequencies were similar to those reported from the Weddell Sea in 1983 (Heinbokel and Coats 1984). 1985 REVIEW
The chlorophyll data were consistent with those of Fay (1973). Between 47 and 75 percent of the total chlorophyll passed a 10micrometer mesh (as much as 49 percent passed a 5-micrometer Nuclepore filter!). Unlike the 2 years sampled by Krebs (1973, 1974), however, a major phytoplankton bloom did not develop in Arthur Harbor during the December/January study period. Chlorophyll a concentrations greater than 6 micrograms per liter were never observed in the samples taken during this study, although other investigators (e.g., Quetin personal communication) reported heavy phytoplankton blooms in waters east and north of our study area. Finally, we were able to sample carefully and examine the total ciliate assemblage present in the vicinity of Palmer Station. Oligotrichs (including both tintinnine nd non-loricated forms) dominated all of our samples. Concentrations of tintinnines greatly exceeded values we observed in the Weddell Sea (Hembokel and Coats 1984) or those reported by Littlepage (1968) for McMurdo Sound. The most abundant tintinnine was a small species of Salpingella which, to our knowledge, has not been reported previously from the Antarctic, although we did observe it in samples collected from beneath the seasonal pack ice in 1983. At times it exceeded 2,000 individuals per liter. Relatively small (less than 50 micrometers) oligotrichines (genus Strombidiutn and/or closely related genera) generally exceeded the tintinnines in abundance. As in the case of tintinnine reproductive efforts (frequency-of-dividing-cells), the abundance of both tintinnines and non-loricate oligotrichs tended to increase as the season progressed but showed no general relationship to chlorophyll a concentrations. Our data on the size-distribution of the phytoplankton assemblage and on the abundance of ciliates in these waters support and extend the previous data appropriate for assessing the importance of the ciliates and nanophytoplankton in the Antarctic. While our data are quite limited in spatial and temporal extent, they clearly illustrate how important these minute and under-studied forms could be within the antarctic food web. This work was supported in part by National Science Foundation grant DPP 83-16216. The assistance of K. Henderson and the crew of the U.S. Coast Guard Arctic Survey Boat is gratefully acknowledged.
References
Fay, R. R. 1973. Significance of nannoplankton in primary production of the Ross Sea, Antarctica, during the 1972 austral summer. (Doctoral Thesis, Texas A&M University, Dissertation Abstracts No. 74-13,060.) Heinbokel, J.F., and D.W. Coats. 1984. Reproductive dynamics of ciliates in the antarctic ice-edge zone. Antarctic Journal of the U.S., 19(5), 111-113. Krebs, W.N. 1973. Ecology of antarctic marine diatoms. Antarctic Journal of the U.S., 8(5), 307 - 309. Krebs, W.N. 1974. Physical-chemical oceanography of Arthur Harbor, Anvers Island. Antarctic Journal of the U.S., 9(5), 219 - 221. Littlepage, J.L. 1968. Plankton investigations McMurdo Sound. Antarctic Journal of the U.S., 3(5), 162 - 163. Quetin, L.B. 1985. Personal communication. 135
Data summary: Arthur Harbor studies, December 1984 and January 1985 Station
Chlorophyll a (in micrograms per liter) Total ^ 20 micrometer ^ 10 micrometer ^ 5 micrometer
2.06 1.34 0.97 0.53
4.13 3.59 2.93 2.02
2.85 2.48 2.14 1.40
1.81 1.43 1.18 0.65
Chlorophyll a (percent of total) ^ 20 micrometer ^ 10 micrometer ^ 5 micrometer
65 47 26
87 71 49
87 75 49
79 65 36
Ciliate abundance (number per liter) Tintinnines Other oligotrichs Total ciliates
500 900 1,700
500 1,200 1,800
1,200 2,400 3,700
2,100 2,600 5,100
Frequency of dividing cells (percent of total cells) Cymatocylis spp. Laackmariniella spp.
Codenellopsis glacialis
12.7 31.4 30.1
Microheterotrophs in the ice-edge zone: An AMERIEZ study D.L. GARRISON and K.R. BUCK Center for Marine Studies University of California Santa Cruz, California 95064
Microheterotrophs, such as heterotrophic flagellates and ciliates, are now widely recognized as important components of pelagic food webs (e.g., Taylor 1982). The abundance of these organisms in the ice-edge zone may reflect increased production in ice communities and in ice-edge plankton blooms (Garrison et al. 1984). As part of the Antarctic Marine Ecosystem Research at the Ice-Edge Zone (AMERIEZ) program in November 1983, we began to study microheterotrophs in the ice-edge region of the Weddell Sea. In initial reports, we reported (Buck and Garrison 1984; Garrison, Buck, and Silver 1984; Garrison and Buck 1985) finding a surprising diversity and abundance of microheterotrophs in ice-edge zone, and an apparent increase 136
16.3 38.1 29.2
19.1 46.0 35.5
22.2 53.9 46.2
in microzooplankton at the ice edge. During 1984 and 1985, we have examined approximately 75 ice and water samples. Here, we present a summary of our continued studies. Population studies. The abundance of microheterotrophs in the upper water column for stations under heavy ice cover (stations 5 and 6) and along a transect across the ice-edge zone (stations 15 through 21) is shown in the figure. Most of the microzooplankton biomass was concentrated in the upper 50 meters; abundance dropped markedly below approximately 50 to 60 meters. Microheterotroph populations are much more concertrated in ice than in water but, because ice is limited to the upper 1 t 2 meters, the largest fraction of microheterotrophs will still be found in the water column (table; see Garrison et al. 1984). Our data for early spring conditions overlap the range of values von Brockel (1981) cites for late fall conditions. Our lower range of values suggests a seasonal abundance cycle for microzooplankton. This possibility will be addressed during an AMERIEZ cruise in March 1986. Microheterotroph populations in ice were often dominated by heterotrophic flagellates, (see Buck and Garrison 1984; Garrison et al. 1984), whereas those in water were almost entirely comprised of naked ciliates. We have been able to recognize several forms that occur in both ice and water. However, there are still many forms that we cannot yet identify with certainty, and our efforts to determine the relationships between ice and water is continuing. ANTARCTIC JOURNAl.
We have been engaged recently in research to define the significance of the microzooplankton in antarctic waters. These studies began in 1983 on a cruise to the Weddell Sea during which we studied the abundance and the reproductive (division) frequencies and periodicities of the tintinnids, a group of planktonic ciliates (Heinbokel and Coats 1984). In 1984 - 1985 we continued these studies at the Palmer Station (64°46'S 64°3W). Our studies were broadened last season to include definition of the entire ciliate assemblage in the waters of Arthur Harbor and definition of the phytoplankton population on the basis of size-fractionated (less than 5 micrometer, less than 10 micrometer, less than 20 micrometer, and total) chlorophyll a determinations. In addition, we continued the studies of ciliate reproduction begun the previous year. Sample analysis was largely completed while at Palmer Station. Data anlaysis is still incomplete, but general results are clear now. Our research during the 1984 - 1985 field season both confirmed our findings from the 1983 cruise in the Weddell Sea (Heinbokel and Coats 1984) and supported our suppositions concerning the numerical importance of the ciliate and nanophytoplankton assemblages. Five 24-hour stations were occupied in or near Arthur Harbor at approximately weekly intervals from 14 December 1984 through 10 January 1985. Samples were obtained at regular intervals from three depths: surface, 10 meters, and 20 meters. Water samples were sizefractionated using 10- and 20-micrometer Nitex mesh and 5micrometer Nuclepore filters prior to fluorometric analysis of chlorophyll a; ciliates in "whole water" samples were fixed and preserved in basic Lugol's fixative (iodine/potassium iodide) prior to enumeration using an inverted microscope. Net tows (35-micrometer mesh) were taken vertically from 20 meters to the surface to collect tintinnids for analysis of the frequency of dividing cells. Sample analyses for the first four stations were ompleted at Palmer Station; those data are summarized in the accompanying table. Tabulated data are presented as station averages for the purpose of this discussion, although the detailed and interesting points concerning depth distributions and diel effects are lost with such an approach. A more detailed discussion will be prepared when station 5 samples have been analyzed. Even at this level of analysis, however, several points are striking. As in the 1983 samples, there was no indication that tintinnine reproduction was phased over the diel cycle. Frequencies of dividing cells ranged approximately between 12 and 22 percent for Cymatocylis spp. and between 30 and 50 percent for the other two species of tintinnines studied. Division frequencies for all three species generally increased as the period of study (December and January) progressed. Observed frequencies were similar to those reported from the Weddell Sea in 1983 (Heinbokel and Coats 1984). 1985 REVIEW
The chlorophyll data were consistent with those of Fay (1973). Between 47 and 75 percent of the total chlorophyll passed a 10micrometer mesh (as much as 49 percent passed a 5-micrometer Nuclepore filter!). Unlike the 2 years sampled by Krebs (1973, 1974), however, a major phytoplankton bloom did not develop in Arthur Harbor during the December/January study period. Chlorophyll a concentrations greater than 6 micrograms per liter were never observed in the samples taken during this study, although other investigators (e.g., Quetin personal communication) reported heavy phytoplankton blooms in waters east and north of our study area. Finally, we were able to sample carefully and examine the total ciliate assemblage present in the vicinity of Palmer Station. Oligotrichs (including both tintinnine nd non-loricated forms) dominated all of our samples. Concentrations of tintinnines greatly exceeded values we observed in the Weddell Sea (Hembokel and Coats 1984) or those reported by Littlepage (1968) for McMurdo Sound. The most abundant tintinnine was a small species of Salpingella which, to our knowledge, has not been reported previously from the Antarctic, although we did observe it in samples collected from beneath the seasonal pack ice in 1983. At times it exceeded 2,000 individuals per liter. Relatively small (less than 50 micrometers) oligotrichines (genus Strombidiutn and/or closely related genera) generally exceeded the tintinnines in abundance. As in the case of tintinnine reproductive efforts (frequency-of-dividing-cells), the abundance of both tintinnines and non-loricate oligotrichs tended to increase as the season progressed but showed no general relationship to chlorophyll a concentrations. Our data on the size-distribution of the phytoplankton assemblage and on the abundance of ciliates in these waters support and extend the previous data appropriate for assessing the importance of the ciliates and nanophytoplankton in the Antarctic. While our data are quite limited in spatial and temporal extent, they clearly illustrate how important these minute and under-studied forms could be within the antarctic food web. This work was supported in part by National Science Foundation grant DPP 83-16216. The assistance of K. Henderson and the crew of the U.S. Coast Guard Arctic Survey Boat is gratefully acknowledged.
References
Fay, R. R. 1973. Significance of nannoplankton in primary production of the Ross Sea, Antarctica, during the 1972 austral summer. (Doctoral Thesis, Texas A&M University, Dissertation Abstracts No. 74-13,060.) Heinbokel, J.F., and D.W. Coats. 1984. Reproductive dynamics of ciliates in the antarctic ice-edge zone. Antarctic Journal of the U.S., 19(5), 111-113. Krebs, W.N. 1973. Ecology of antarctic marine diatoms. Antarctic Journal of the U.S., 8(5), 307 - 309. Krebs, W.N. 1974. Physical-chemical oceanography of Arthur Harbor, Anvers Island. Antarctic Journal of the U.S., 9(5), 219 - 221. Littlepage, J.L. 1968. Plankton investigations McMurdo Sound. Antarctic Journal of the U.S., 3(5), 162 - 163. Quetin, L.B. 1985. Personal communication. 135
Data summary: Arthur Harbor studies, December 1984 and January 1985 Station
Chlorophyll a (in micrograms per liter) Total ^ 20 micrometer ^ 10 micrometer ^ 5 micrometer
2.06 1.34 0.97 0.53
4.13 3.59 2.93 2.02
2.85 2.48 2.14 1.40
1.81 1.43 1.18 0.65
Chlorophyll a (percent of total) ^ 20 micrometer ^ 10 micrometer ^ 5 micrometer
65 47 26
87 71 49
87 75 49
79 65 36
Ciliate abundance (number per liter) Tintinnines Other oligotrichs Total ciliates
500 900 1,700
500 1,200 1,800
1,200 2,400 3,700
2,100 2,600 5,100
Frequency of dividing cells (percent of total cells) Cymatocylis spp. Laackmariniella spp.
Codenellopsis glacialis
12.7 31.4 30.1
Microheterotrophs in the ice-edge zone: An AMERIEZ study D.L. GARRISON and K.R. BUCK Center for Marine Studies University of California Santa Cruz, California 95064
Microheterotrophs, such as heterotrophic flagellates and ciliates, are now widely recognized as important components of pelagic food webs (e.g., Taylor 1982). The abundance of these organisms in the ice-edge zone may reflect increased production in ice communities and in ice-edge plankton blooms (Garrison et al. 1984). As part of the Antarctic Marine Ecosystem Research at the Ice-Edge Zone (AMERIEZ) program in November 1983, we began to study microheterotrophs in the ice-edge region of the Weddell Sea. In initial reports, we reported (Buck and Garrison 1984; Garrison, Buck, and Silver 1984; Garrison and Buck 1985) finding a surprising diversity and abundance of microheterotrophs in ice-edge zone, and an apparent increase 136
16.3 38.1 29.2
19.1 46.0 35.5
22.2 53.9 46.2
in microzooplankton at the ice edge. During 1984 and 1985, we have examined approximately 75 ice and water samples. Here, we present a summary of our continued studies. Population studies. The abundance of microheterotrophs in the upper water column for stations under heavy ice cover (stations 5 and 6) and along a transect across the ice-edge zone (stations 15 through 21) is shown in the figure. Most of the microzooplankton biomass was concentrated in the upper 50 meters; abundance dropped markedly below approximately 50 to 60 meters. Microheterotroph populations are much more concertrated in ice than in water but, because ice is limited to the upper 1 t 2 meters, the largest fraction of microheterotrophs will still be found in the water column (table; see Garrison et al. 1984). Our data for early spring conditions overlap the range of values von Brockel (1981) cites for late fall conditions. Our lower range of values suggests a seasonal abundance cycle for microzooplankton. This possibility will be addressed during an AMERIEZ cruise in March 1986. Microheterotroph populations in ice were often dominated by heterotrophic flagellates, (see Buck and Garrison 1984; Garrison et al. 1984), whereas those in water were almost entirely comprised of naked ciliates. We have been able to recognize several forms that occur in both ice and water. However, there are still many forms that we cannot yet identify with certainty, and our efforts to determine the relationships between ice and water is continuing. ANTARCTIC JOURNAl.
