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Seasonal-to-decadal scale variability in primary production and particulate matter export at Station ALOHA
Progress in Oceanography ( IF 3.8 ) Pub Date : 2021-04-02 , DOI: 10.1016/j.pocean.2021.102563
David M. Karl , Ricardo M. Letelier , Robert R. Bidigare , Karin M. Björkman , Matthew J. Church , John E. Dore , Angelicque E. White

Station ALOHA (A Long-term Oligotrophic Habitat Assessment) was established in the North Pacific Subtropical Gyre (22°45′N, 158°W) as an oligotrophic ocean benchmark to improve our understanding of processes that govern the fluxes of carbon (C) into and from the surface ocean. At approximately monthly intervals, measurements of the primary production of particulate C (PC) using the 14C method, and the export of PC and particulate nitrogen (PN) using surface-tethered sediment traps deployed at 150 m have been made along with a host of complementary physical, biological, and biogeochemical measurements. Euphotic zone depth-integrated (0–200 m) primary production ranged from 220.2 (standard deviation, SD, 10.8) mg C m−2 d−1 in Feb 2018 to 1136.5 (SD = 17.1) mg C m−2 d−1 in Jun 2000, with a 30-yr (1989–2018) mean of 536.8 (SD = 135.0) mg C m−2 d−1 (n = 271). Although the monthly primary production climatology was fairly well constrained, we observed substantial sub-decadal variability and a significant 0–125 m depth-integrated increasing trend of 4.0 (p < 0.01; 95% confidence interval, CI, 2.1–5.9) (mg C m−2 d−1) yr−1 since 1989, displaying a large relative increase of 37% (CI = 18–55%) in the lower portion (75–125 m) of the euphotic zone. Chlorophyll (Chl) a and suspended PC and PN concentrations also displayed significant (p < 0.01) increases in the 75–125 m region of the euphotic zone. PC export at 150 m exhibited both short-term (monthly) and longer-scale variability with a 30-yr mean of 27.9 (SD = 9.7, n = 265) mg C m−2 d−1. PC and PN export exhibited extended, multi-year periods of significantly lower or higher values compared to the 30-yr mean. These multi-year periods of anomalously low and high particle export, in the absence of contemporaneous variations in primary production, probably reflect periodic changes in remineralization efficiencies. The PC export ratio (e-ratio; PC export at 150 m ÷ 0–150 m depth-integrated 14C-based primary production) was low, with a 30-yr mean of 0.054 (SD = 0.021, n = 248), and exhibited a significant (p < 0.01) long-term decreasing trend over the 30-yr observation period. The 30-yr long-term increases in primary production (~37%), Chl a, and suspended PC and PN concentrations (~17%, 8%, and 8%, respectively) in the 75–125 m portion of the water column are hypothesized to result from an enhanced supply of nutrients to the lower portion of the water column over the past three decades.



中文翻译:

ALOHA站初级生产和颗粒物出口的季节性变化到十年尺度的变化

在北太平洋亚热带环流(22°45′N,158°W)中建立了ALOHA站(长期低营养栖息地评估),作为低营养海洋基准,以增进我们对控制碳通量(C)的过程的了解。进入和离开表层海洋。每隔大约一个月,就使用14 C方法测量一次颗粒C(PC)的初次生产,并使用部署在150 m处的表面束缚沉积物捕集阱对PC和颗粒氮(PN)的出口进行了测量。互补的物理,生物学和生物地球化学测量。深度区(0–200 m)的一次生化集成度范围为220.2(标准偏差,SD,10.8)mg C m -2 d -1在2018年2月达到1136.5(SD = 17.1)mg C m -2 d -1(2000年6月),30年(1989-2018)的平均值为536.8(SD = 135.0)mg C m -2 d -1(n = 271)。尽管每月的主要生产气候受到很好的限制,但我们观察到年代际变化很大,深度整合深度0-125 m的增加趋势为4.0(p <0.01; 95%置信区间,CI为2.1-5.9)(mg 1989年以来的C m -2 d -1)yr -1,在富油区下部(75-125 m)中显示了37%(CI = 18-55%)的相对大幅度增加。叶绿素(Chl)a悬浮的PC和PN浓度在富营养区75-125 m区域也显示显着(p <0.01)升高。150 m处的PC出口表现出短期(每月)和较大范围的变化,其30年平均值为27.9(SD = 9.7,n = 265)mg C m -2 d -1。与30年平均值相比,PC和PN出口表现出长期的,多年的增长,其价值明显更低或更高。在初级产品没有同期变化的情况下,这些多年异常低和高颗粒出口的时期,可能反映了再矿化效率的周期性变化。PC出口比率(e比; PC出口为150 m÷0–150 m深度积分14基于C的初级生产)较低,其30年平均值为0.054(SD = 0.021,n = 248),并且在30年观察期内表现出显着的(p <0.01)长期下降趋势。在75-125 m的水域中,初级生产(〜37%),叶绿素a和悬浮的PC和PN浓度(分别为〜17%,8%和8%)的30年长期增加据推测,这是由于过去三十年来水柱下部养分供应的增加所致。

更新日期:2021-05-12
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