A 7‐yr spatial time series resolves the island mass effect and associated shifts in picocyanobacteria abundances near O'ahu, Hawai'i

IF 3.8 1区 地球科学 Q1 LIMNOLOGY
Christina M. Comfort, Chris Ostrander, Craig E. Nelson, David M. Karl, Margaret A. McManus
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Abstract

Islands in oligotrophic oceans act as local sources of nutrients. These nutrients originate from land and from deep oceanic nutrients introduced to the photic zone by tides, currents, and internal waves interacting with island bathymetry. These processes create the island mass effect (IME), in which increased chlorophyll a (Chl a) is found near islands compared to oceanic waters. The IME has been described via satellite observations, but the effects on phytoplankton community structure are not well documented. From 2013 to 2020, chlorophyll, nutrient, and picoplankton samples were collected from multiple depths on quarterly cruises at two sites south of O'ahu, Hawai'i. Prochlorococcus, Synechococcus, picoeukaryotes, and heterotrophic bacteria were enumerated using flow cytometry. We compared nearshore results to Sta. ALOHA, 100 km from O'ahu. Consistent with the expected IME, Chl a concentrations were significantly enhanced at both nearshore sites compared to Sta. ALOHA. Prochlorococcus concentrations increased with greater distance from shore, particularly below 50 m; mixed layer concentrations of Synechococcus and picoeukaryotes significantly decreased with greater distance from shore, as did concentrations of nitrate and phosphate below the mixed layer. Heterotrophic bacteria concentrations did not show a spatial trend. Carbon‐based biomass estimates of the picoplankton population indicated that the IME‐associated Chl a increases near the island are likely driven by larger phytoplankton classes. This study describes the IME‐associated shift in the picophytoplankton community distribution, which has implications for nutrient cycling, food web dynamics and fisheries in oligotrophic island ecosystems, and adds to the understanding of spatial heterogeneity in carbon fixation in the ocean.
7 年空间时间序列解析了夏威夷奥阿胡附近的岛屿质量效应和相关的皮蓝藻丰度变化
寡营养海洋中的岛屿是当地的营养源。这些营养物质来自陆地,以及潮汐、海流和内波与岛屿水深相互作用而引入光照区的深海营养物质。这些过程产生了岛屿质量效应(IME),即岛屿附近的叶绿素 a(Chl a)比大洋水域高。卫星观测已对 IME 进行了描述,但关于其对浮游植物群落结构的影响却没有很好的记录。从 2013 年到 2020 年,在夏威夷奥阿胡以南的两个地点,每季度巡航一次,从多个深度采集叶绿素、营养物质和微小浮游生物样本。使用流式细胞仪对原链球菌、中链球菌、微小核菌和异养细菌进行了计数。我们将近岸结果与距奥阿胡岛 100 公里的 ALOHA 站进行了比较。与预期的 IME 相一致,两个近岸地点的 Chl a 浓度均明显高于 ALOHA 站。原绿球藻的浓度随着离岸距离的增加而增加,特别是在 50 米以下;混合层中 Synechococcus 和皮氏藻的浓度随着离岸距离的增加而显著降低,混合层以下的硝酸盐和磷酸盐浓度也是如此。异养细菌的浓度没有呈现出空间趋势。对微小浮游生物种群进行的基于碳的生物量估算表明,岛屿附近与 IME 相关的 Chl a 增加可能是由较大的浮游植物类别驱动的。这项研究描述了与 IME 相关的浮游微藻群落分布的变化,这对寡营养岛屿生态系统的营养循环、食物网动力学和渔业都有影响,并加深了人们对海洋碳固定空间异质性的理解。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Limnology and Oceanography
Limnology and Oceanography 地学-海洋学
CiteScore
8.80
自引率
6.70%
发文量
254
审稿时长
3 months
期刊介绍: Limnology and Oceanography (L&O; print ISSN 0024-3590, online ISSN 1939-5590) publishes original articles, including scholarly reviews, about all aspects of limnology and oceanography. The journal''s unifying theme is the understanding of aquatic systems. Submissions are judged on the originality of their data, interpretations, and ideas, and on the degree to which they can be generalized beyond the particular aquatic system examined. Laboratory and modeling studies must demonstrate relevance to field environments; typically this means that they are bolstered by substantial "real-world" data. Few purely theoretical or purely empirical papers are accepted for review.
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