ABSTRACT: This study was conducted in 4 Labrador fjords (Nachvak, Saglek, Okak, and Anaktalak) during the summers of 2007 and 2013, early fall 2010, and late fall 2009. Our results show that water temperature combined with the availability of nutrients and organic substrates are the main abiotic factors controlling the abundance of heterotrophic bacteria in Labrador fjords. Bacterivory also played a crucial role, with heterotrophic bacteria exerting a significant bottom-up control on the abundance of heterotrophic nanoflagellates (r = 0.35, p < 0.05) and ciliates (r = 0.70, p < 0.01). During summer 2013, the intrinsic phytoplankton growth rate varied between <0 and 0.64 d^-1, with a mean value of 0.36 d^-1. The herbivory rate was highly variable, ranging from 0.01 to 0.86 d^-1, with a mean value of 0.31 d^-1. Grazing mortality was 6-fold higher than phytoplankton growth rate. Mean phytoplankton growth and herbivory rates in Labrador fjords were comparable to the Barents and Bering seas. The intrinsic growth rate of total heterotrophic bacteria ranged between <0 and 0.68 d^-1, with a mean value of 0.30 d^-1. Bacterivory varied from 0.01 to 0.95 d^-1, with a mean of 0.30 d^-1. Mortality due to grazing was up to 2.3 times higher than total bacterial growth rate. This study improves our understanding of the factors influencing the dynamics of heterotrophic bacteria and indicates that herbivory and bacterivory exert substantial control on microbial communities in Labrador fjords.

中文翻译：

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拉布拉多峡湾（加拿大东北部）的异养细菌丰度和浮游动物放牧的多变量控制

摘要：这项研究是在2007年和2013年夏季，2010年初和2009年秋末在4个拉布拉多峡湾（纳赫瓦克，萨格里克，奥卡克和阿纳克塔拉克）进行的。我们的结果表明，水温与养分的供应和有机底物是控制拉布拉多峡湾异养细菌丰富的主要非生物因素。噬菌体也起着至关重要的作用，异养细菌对异养纳米鞭毛（r = 0.35，p <0.05）和纤毛虫（r = 0.70，p <0.01）的丰度起着明显的自下而上的控制作用。2013年夏季，浮游植物的内在生长速率在<0和0.64 d ^-1之间变化，平均值为0.36 d ^-1。草食率变化很大，范围为0.01至0.86 d^-1，平均值为0.31 d ^-1。放牧死亡率是浮游植物生长速率的6倍。拉布拉多峡湾的平均浮游植物生长和草食率与巴伦支海和白令海相当。总异养细菌的固有生长速率在<0和0.68 d ^-1之间，平均值为0.30 d ^-1。噬菌体从0.01到0.95 d ^-1不等，平均值为0.30 d ^-1。放牧导致的死亡率比细菌总生长率高2.3倍。这项研究提高了我们对影响异养细菌动力学的因素的理解，并表明草食和细菌对拉布拉多峡湾的微生物群落具有实质性的控制作用。