The aim of this study was to determine the variations of δ¹³C and δ¹⁵N of
particulate organic matter (POM) and the factors that control the isotopic fractionation from inorganic substrates to zooplankton and lead to variations in the isotopic composition of suspended and sinking POM in the subarctic northeast Pacific Ocean. Along a transect from Station L (48°39'N, 126°40'W) to Station P (50°N, 145°W), surface δ¹⁵NO₃⁻ decreased from 11.2‰ to 7.6‰, while [NO₃⁻] increased from 3 to 12 pM. The δ¹⁵N trends for bulk POM, < 5 pm POM, 50-253 pm POM, < 253 pm POM
and zooplankton were similar to that for nitrate. The fractionation factor (e) for the
nitrogen isotopes was 5‰. Trophic enrichment of ¹⁵N was observed with
mesozooplankton being isotopically heavier than suspended POM by 3.9‰ at Station P
and 2.2‰ at Station L. The range of δ¹⁵N among six zooplankton groups was 3.7‰. At
Station P, sinking δ¹³C[sub POM] and δ¹⁵N[sub POM] at 3800 m between 1982 and 1990 show
significant annual changes. The δ¹³C[sub POM] ranges from -25.3‰ to -22.0‰ and the
δ¹⁵N[sub POM] ranges from 10.2‰ to 7.7‰, isotopically depleted values occurring in summer and heavier values occurring in winter. The change in trophic length may be the principal
controlling factor of the variations. The δ¹³C[sub POM] at 200,1000 and 3800 m show a ¹³C
enrichment with depth. Suspended POM δ¹³C and δ¹⁵N increased with depth and were
higher than those of sinking POM, suggesting that the two types of POM did not interact
in deep water. At Station L, high frequency variations of δ¹³C and δ¹⁵N in summer are
due to the periodic injection of subsurface nitrate by upwelling, which leads to diatom
blooms, resulting in a heavier δ¹³C and a lighter δ¹⁵N in sinking POM. The sinking
δ¹⁵N[sub POM] value (8%c) is much heavier than that of nitrate (4%c) at 500 m, suggesting that
the lateral input of lower nitrate δ¹⁵N from the open ocean (3‰) was important. This
study develop our understanding of the isotopic biogeochemistry of carbon and nitrogen
in the ocean.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/6846 |
| Date | 05 1900 |
| Creators | Wu, Jinping |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
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