Environmental factors controlling the phytoplankton blooms at the Patagonia shelf-break in spring

被引:90
作者
Garcia, Virginia M. T. [1 ]
Garcia, Carlos A. E. [2 ]
Mata, Mauricio M. [2 ]
Pollery, Ricardo C. [3 ]
Piola, Alberto R. [4 ,5 ]
Signorini, Sergio R. [6 ]
McClain, Charles R. [6 ]
Iglesias-Rodriguez, M. Debora [7 ]
机构
[1] Fed Univ Rio Grande, Dept Oceanog, BR-96201900 Rio Grande, RS, Brazil
[2] Fed Univ Rio Grande, Dept Phys, BR-96201900 Rio Grande, RS, Brazil
[3] Univ Santa Ursula, Inst Biol & Environm Sci, BR-22231010 Rio De Janeiro, Brazil
[4] Serv Hidog Naval, RA-1271 Buenos Aires, DF, Argentina
[5] Univ Buenos Aires, RA-1053 Buenos Aires, DF, Argentina
[6] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
[7] Univ Southampton, Sch Ocean & Earth Sci, Natl Oceanog Ctr, Southampton SO14 3ZH, Hants, England
基金
美国国家科学基金会;
关键词
phytoplankton bloom; nutrients; primary production; Patagonia shelf-break; Malvinas current;
D O I
10.1016/j.dsr.2008.04.011
中图分类号
P7 [海洋学];
学科分类号
0707 ;
摘要
The shelf-break front formed between Argentinean shelf waters and the Malvinas Current (MC) flow shows a conspicuous band of high phytoplankton biomass throughout spring and summer, detected by ocean color sensors. That area is the feeding and spawning ground of several commercial species of fish and squid and is thought to play an important role in CO2 sequestration by the ocean. Phytoplankton blooms in this area have been attributed mainly to coccolithophorids, a group of calcite-producing phytoplankton. Here we present the environmental factors associated with the spring bloom at the Patagonian shelf-break (40 degrees-48 degrees S) in the austral spring 2004. A remarkable bloom of diatoms and dinoflagellates (approximately 1200 km long) was observed along the front, where integrated chlorophyll values ranged from 90.3 to 1074 mg m(-2). It is suggested that supply of macro-nutrients by upwelling and probably iron by both upwelling and shelf transport contribute to maintaining the spring bloom. Strong water column stability along the front allowed the accumulation of algal cells mainly in the top 50m and their maintenance in the euphotic layer. East of the shelf-break front, macronutrient levels were high (surface nitrate = 16.6 mu M, phosphate = 0.35 mu M, silicate = 4.0 mu M), associated with low phytoplankton biomass (<2 mg m(-3)). This was due to mixing and advection associated with the MC flow and to grazing pressure at a transitional site between the MC and the high chlorophyll patch. Primary production rates (determined by the C-14 technique) ranged between 1.9 and 7.8 gCm(-2) d(-1). Primary production was highest near 42 degrees S partly because of the elevated phytoplankton biomass, which consumed most of the nitrate and phosphate in surface waters in this region. These high primary production rates are comparable with maximal seasonal productivity at eastern boundary currents. The large bloom extent at the Patagonian shelf-break (approximately 55,000 km(2) patch of > 2 mg m(-3) chlorophyll), the associated primary production rates and diatom dominance indicate a potentially significant biological control of gases such as O-2 and CO2 in surface layers. The main factors favoring the development and maintenance of these blooms are nutrient supply from MC upwelling and water column stability. Other processes such as mixing or grazing play an important role in biomass modulation in the region. (C) 2008 Elsevier Ltd. All rights reserved.
引用
收藏
页码:1150 / 1166
页数:17
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