Robotic Observations of Enhanced Carbon Biomass and Export at 55°S during SOFeX

Science

Volumn 304, Issue 5669, 2004, Pages 417-420

  Bishop, James K B ^a   Wood, Todd J ^a   Davis, Russ E ^b   Sherman, Jeffrey T ^b  

^a LAWRENCE BERKELEY NATIONAL LABORATORY   (United States)

^b UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

BIOMASS; CARBON; IRON; NITRATES; OCEANOGRAPHY; SURFACE WATERS;

CARBON BIOMASS; HIGH-NITRATE LOW-SILICATE WATERS; IRON AMENDED LOW-SILICATE WATERS; IRON FERTILIZATION;

ROBOTICS;

CARBON; IRON; NITRATE; SILICATE; SURFACE WATER;

BIOMASS; CARBON CYCLE; FERTILIZER APPLICATION; IRON; SEAWATER;

ARTICLE; BIOMASS; CARBON CYCLE; GLOBAL POSITIONING SYSTEM; OCEAN ENVIRONMENT; PRIORITY JOURNAL; ROBOTICS; SALINITY; TEMPERATURE;

BIOMASS; CARBON; IRON; OCEANS AND SEAS; PHYTOPLANKTON; ROBOTICS; SEAWATER; TEMPERATURE;

SOUTHERN OCEAN;

EID: 1942520237     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.1087717     Document Type: Article

References (25)

1. J. L. Sarmiento, J. C. Orr, Limnol. Oceanogr. 36, 1928 (1991).
2. D. M. Sigman, E. A. Boyle, Nature 407, 859 (2000).
3. J. R. Petit et al., Nature 399, 429 (1999).
4. K. H. Coale et al., Science 304, 408 (2004).
5. J. K. B. Bishop, R. E. Davis, J. T. Sherman, Science 298, 817 (2002).
6. Materials and methods are available as supporting material on Science Online.
7. CFI is the measure of the accumulation of particles on the upward-looking optical (detector end) window of the Explorer's transmissometer-based POC sensor (WETLabs Inc., Philomath, OR) while the float is "parked" at 100 m. Before profiling starts, the raw transmission "counts" from the POC sensor are read; then, the exhaust from the Explorer's pumped CTD removes settled particles and the transmission counts are read again. The difference between "after" and "before" readings divided by the time that the Explorer was parked at depth gives the CFI (counts/day). More detail, including pictures of instrument setup, is found in (6).
8. The serial numbers of the Explorers are assigned by the Scripps Instrument Development Group; we retain these identities because they uniquely identify the data sets underlying this paper. For simplicity, we refer to Explorer 1177 as the "control" Explorer and Explorer 2104 as the "in-patch" Explorer. Explorers 2054 and 2103 were also deployed "in patch" at 55°S and 66°S, respectively. The POC sensor on Explorer 2054 had a start-up problem that precluded CFI results; poor data transmission success resulted in only sporadic profile data (29 profiles in 2 months). The first week of 2054's profile data is combined with the time series from 2104 in Fig. 2A. Data from 2054 beginning 2 weeks after its deployment no longer showed evidence of the iron-enhanced biomass. Explorers 1177 and 2104 operated for more than 14 months; Explorer 2103, deployed at 66°S, last communicated on 23 July 2003, 18 months after deployment.
9. Retrospective analysis shows that Explorer 2104 was deployed 8 km north of the Monterey Bay Aquarium Research Institute's "center" drifter and near the north edge of the second patch laid down by R/V Revelle. In the coordinate system of Explorer 2104, it was deployed approximately 7 km west of the second Fe patch and ∼8 km north of the drifter. The float, however, was deployed in waters containing SF6 and immediately registered higher POC levels. During Revelle's second visit to the North Patch in early February 2002, the float was "in" the narrow feature (6).
10. Moderate Resolution Imaging Spectroradiometer (MODIS) satellite image of surface chlorophyll was provided by F. Chavez and is described in (4).
11. Two pairs of Carbon Explorers operating in high-nutrient, low chlorophyll waters of the subarctic North Pacific in 2001 and 2003 yielded virtually identical biomass records over much longer periods (5, 24) and thus provide confidence in the differences described here.
12. Mixed-layer depth is the depth where seawater potential density is increased by 0.05 units relative to the surface value.
13. D. A. Siegel, W. G. Deuser, Deep-Sea Res. 44, 1519 (1997).
14. K. Buesseler, J. Andrews, S. Pike, M. Charrette, Science 304, 414 (2004).
15. -1.
16. S. Honjo, R. Francois, S. Manganini, J. Dymond, R. Collier, Deep-Sea Res. II 47, 3521 (2000).
17. J. H. Martin, G. A. Knauer, D. M. Karl, W. W. Broenkow, Deep-Sea Res. 34, 267 (1987).
18. -1 to 55°S CFI data.
19. -2. These calculations assume no net production of POC over the 2-week period of the loss and thus represent lowest estimates.
20. I. Y. Fung et al., Global Biogeochem. Cycles 14, 281 (2000).
21. J. H. Martin, R. M. Gordon, S. Fitzwater, W. B. Broenkow, Deep-Sea Res. 36, 649 (1989).
22. P. W. Boyd et al., Nature 407, 695 (2000).
23. F. Gervais, U. Riebesell, M. Y. Gorbunov, Limnol Oceanogr. 47, 1324 (2002).
24. J. K. B. Bishop, unpublished data.
25. We thank K. Johnson and F. Chavez, Moss Landing Marine Laboratories; C. Guay, Lawrence Berkeley National Laboratory (LBNL), and P. Lam, LBNL/University of California, Berkeley; and the crew and scientific parties aboard RV Revelle for their assistance. We thank M. Altabet and D. Timothy for their measurements of POC in multiple unit large volume in-situ filtration system (MULVFS) samples and for providing the Rosette POC results described in (6). This work was supported by the U.S. Department of Energy (DOE) Office of Science, Office of Biological and Environmental Research (KP1202030). Implementation of the CFI scheme on DOE SOFeX Explorers was supported through the National Oceanographic Partnership Program (N00014-99-F0450 to LBNL and N00014-99-1-1045 to Scripps Institute of Oceanography).