Photosynthesis-irradiance parameters and community structure associated with coastal filaments and adjacent waters in the northern Arabian Sea

Rory K. Toon, Steven E. Lohrenz*, Catherine E. Rathbun, A. Michelle Wood, Robert A. Arnone, Burton H. Jones, John C. Kindle, Alan D. Weidemann

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Comparisons were made among size-fractionated photosynthesis-irradiance (P-E) parameters, chlorophyll a size distributions, and accessory pigment composition of natural phytoplankton assemblages in filaments, coastal upwelling waters, and an oligotrophic region of the northern Arabian Sea during the Fall Intermonsoon in 1995. Differences between P-E parameters, P(max)/(B) and α(B), were observed between filaments and adjacent waters and were associated with differences in phytoplankton community structure. In a southern filament and coastal upwelled waters, the majority of the estimated biomass (chlorophyll a) was present in the larger (2-20 and 20-200 μm) size fractions; dominant accessory pigments were 19'-butanoyloxyfucoxanthin and peridinin. In higher salinity waters, high percentages of chlorophyll a and lutein/zeaxanthin were observed in the smallest size-fraction (< 2 μm). Whole water values of P(max)/(B) ranged from 1.77 to 2.31 (g C g chl a-1 h-1) when the majority of the biomass was in the largest fractions. Higher values (more than 4.48 g C g chl a-1 h-1) were determined in whole water samples for communities comprised primarily of small cells. A size dependence was also observed in the value of α(B), 0.017 or greater (g C g chl a-1 h-1)/(μmol quanta m-2s-1) for whole water samples at stations dominated by small cells and 0.013 when derived from stations dominated by large cells. The observed pattern of larger phytoplankton associated with upwelling and filament waters was consistent with previous investigations and was, for the most part, comparable to findings in the California Current system. Our results show that differences in taxonomic composition and photosynthetic characteristics were indeed present between filament waters and other distinct regions; these results suggest that taxonomic variations may be associated with size-related variations in P-E parameters. Our findings provide a unique data set describing filament biology in the northern Arabian Sea during the Fall Intermonsoon thus adding important details in efforts to model biogeochemical processes in this region. (C) 2000 Elsevier Science Ltd.

Original languageEnglish (US)
Pages (from-to)1249-1277
Number of pages29
JournalDeep-Sea Research Part II: Topical Studies in Oceanography
Issue number7-8
StatePublished - 2000
Externally publishedYes

Bibliographical note

Funding Information:
X. Chen is gratefully acknowledged for supplying helpful advice and assistance constructing photosynthetrons. We extend thanks to K. Thornton for assistance in collection and ship-board processing of samples. Thanks are also due to the captain and crew of the R/V Thomas G. Thompson. Financial support was provided by The Naval Research Laboratory through the 6.1 Forced Upper Ocean Dynamics ARI under Program Element 61153N sponsored by the Office of Naval Research, NASA contract number NAG5-4570, and by ONR grant #N0003414-94-1- 0429 (to AMW). This is USM contribution number 0192, and US JGOFS contribution 491.

ASJC Scopus subject areas

  • Oceanography


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