University of Maryland Center for Environmental Science, Solomons, MD, United States of America.
Amundsen Science, Université Laval, Québec, QC, Canada.
PLoS One. 2020 Apr 22;15(4):e0231178. doi: 10.1371/journal.pone.0231178. eCollection 2020.
An assessment of the production, distribution and fate of highly branched isoprenoid (HBI) biomarkers produced by sea ice and pelagic diatoms is necessary to interpret their detection and proportions in the northern Bering and Chukchi Seas. HBIs measured in surface sediments collected from 2012 to 2017 were used to determine the distribution and seasonality of the biomarkers relative to sea ice patterns. A northward gradient of increasing ice algae deposition was observed with localized occurrences of elevated IP25 (sympagic HBI) concentrations from 68-70°N and consistently strong sympagic signatures from 71-72.5°N. A declining sympagic signature was observed from 2012 to 2017 in the northeast Chukchi Sea, coincident with declining sea ice concentrations. HBI fluxes were investigated on the northeast Chukchi shelf with a moored sediment trap deployed from August 2015 to July 2016. Fluxes of sea ice exclusive diatoms (Nitzschia frigida and Melosira arctica) and HBI-producing taxa (Pleurosigma, Haslea and Rhizosolenia spp.) were measured to confirm HBI sources and ice associations. IP25 was detected year-round, increasing in March 2016 (10 ng m-2 d-1) and reaching a maximum in July 2016 (1331 ng m-2 d-1). Snowmelt triggered the release of sea ice algae into the water column in May 2016, while under-ice pelagic production contributed to the diatom export in June and July 2016. Sea ice diatom fluxes were strongly correlated with the IP25 flux, however associations between pelagic diatoms and HBI fluxes were inconclusive. Bioturbation likely facilitates sustained burial of sympagic organic matter on the shelf despite the occurrence of pelagic diatom blooms. These results suggest that sympagic diatoms may sustain the food web through winter on the northeast Chukchi shelf. The reduced relative proportions of sympagic HBIs in the northern Bering Sea are likely driven by sea ice persistence in the region.
有必要评估海冰和海洋硅藻产生的高度支化异戊二烯（HBI）生物标志物的产生、分布和归宿，以解释其在北白令海和楚科奇海的检测和比例。2012 年至 2017 年采集的表层沉积物中测量的 HBIs 用于确定标志物相对于海冰模式的分布和季节性。观察到冰藻沉积向北增加的梯度，68-70°N 处出现 IP25（共生 HBI）浓度升高的局部情况，71-72.5°N 处持续存在强烈的共生特征。2012 年至 2017 年，楚科奇海东北部的共生特征呈下降趋势，与海冰浓度下降相一致。2015 年 8 月至 2016 年 7 月，在楚科奇海东北部大陆架上部署了一个系泊沉积物陷阱，研究了 HBI 通量。测量了海冰特有硅藻（Nitzschia frigida 和 Melosira arctica）和产生 HBI 的类群（Pleurosigma、Haslea 和 Rhizosolenia spp.）的冰通量，以确认 HBI 来源和冰的关联。IP25 全年都有检测到，2016 年 3 月增加（10 ng m-2 d-1），2016 年 7 月达到最大值（1331 ng m-2 d-1）。2016 年 5 月，融雪将海冰藻类释放到水柱中，而 2016 年 6 月和 7 月，冰下浮游生物的生产促进了硅藻的输出。海冰硅藻通量与 IP25 通量呈强相关，然而，浮游硅藻和 HBI 通量之间的关联尚无定论。尽管发生了浮游硅藻大量繁殖，但生物扰动可能有利于在陆架上持续埋藏共生有机物。这些结果表明，共生硅藻可能通过冬季维持楚科奇海东北部的食物网。北白令海共生 HBIs 的相对比例较低可能是由于该地区海冰的持续存在。
