Suspended particle organic composition and cycling in surface and midwaters of the equatorial Pacific Ocean |
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| Institution: | 1. Marine Sciences Research Center, Stony Brook University, Stony Brook, NY 11794-5000, USA;2. Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411, USA;3. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 90-1116, Berkeley, CA 94720, USA;1. National Centre for Antarctic and Ocean Research, Ministry of Earth Sciences, Headland Sada, Goa, India;2. Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pashan, India;1. National Centre for Antarctic and Ocean Research, Earth System Science Organization, Ministry of Earth Sciences, Vasco-Da-Gama, Goa 403804, India;2. Centre for Marine Living Resources and Ecology, Earth System Science Organization, Ministry of Earth Sciences, P.B. no. 5415, Kochi 682037, India;1. Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;2. Department of Geology and Geophysics, Louisiana State University, Baton Rouge, LA 70803, USA;3. State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China;1. Key Laboratory of Petroleum Resources, Gansu Province/Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000, China;2. Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology, Ministry of Land and Resources, Qingdao, Shandong 266071, China;3. Qingdao Institute of Marine Geology, Qingdao 266071, China |
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| Abstract: | In this study we relate spatial and temporal variation in the organic composition of suspended particles to current conceptual models of open-ocean particle cycling. Suspended particles in surface (0–200 m) and midwaters (200–1000 m) of the equatorial Pacific Ocean were collected during the 1992 US JGOFS Equatorial Pacific (EqPac) program. Samples collected during El Niño (Survey I) and normal conditions (Survey II) were analyzed for pigment, amino acid, fatty acid, and neutral lipid concentrations and compositions. Principal Components Analysis (PCA) and other statistical methods were used to assess changes in particulate organic composition between Surveys I and II, over 24° of latitude, from 15 to 850 m depth, and to compare our compositional data with previously published data from EqPac sinking particles. These analyses indicated that surface suspended particles (0–200 m) were similar in composition to surface ocean phytoplankton and were less degraded than particles sinking out of the euphotic zone (105 m). The organic composition of suspended particles in surface waters varied with latitudinal and El-Niño-induced changes in phytoplankton assemblages. Midwater suspended particles (200–1000 m) contained labile phytodetrital material derived from particles exiting the euphotic zone (105 m). However, labile organic constituents of midwater suspended particles were increasingly degraded by microbes or consumed by midwater metazoans with depth. The increase in degradation state observed for midwater suspended particles may also have been caused by dilution of deeper (450–850 m) suspended particle pools with more refractory material originating from fast-sinking particles, e.g., fecal pellets. However, the mechanism controlling midwater particle degradation state varied with flux regime; dilution of midwater suspended particles dominated only in the higher flux regime found at equatorial latitudes (5°N–5°S) during Survey II (normal conditions). In summary, it is apparent that organic matter alteration in midwaters, and not cycling within the euphotic zone, has the larger effect on organic composition of suspended particles in the deep equatorial Pacific Ocean. |
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