Total oxygen fluxes, and diatom density, diatom biomass and diversity of the diatom community in spring 2016 and environmental photosynthetically active radiation from 2015 and 2016 from three stations in Potter Cove, Antarctica@en

The Antarctic Peninsula experiences a fast retreat of glaciers, which correlates with an increased release of particles and related increased sedimentation and thus, a decrease in the available light for benthic primary production. We investigated how changes in the general sedimentation and shading patterns affect the primary production by benthic microalgae, the microphytobenthos. In order to determine potential net primary production and respiration of the microphytobenthic community, sediment cores from locations exposed to different sedimentation rates and shading were exposed to photosynthetic active radiation (PAR, 400–700 nm) of 0–70 µmol photons m-2 s-1. Total oxygen fluxes and microphytobenthic diatom community structure, density, and biomass were determined. Our study revealed that the net primary production of the microphytobenthos decreased with increasing sedimentation and shading, while the microphytobenthic diatom density and composition remained similar. By comparing our experimental results with in situ measured PAR intensities, we furthermore assessed the microphytobenthic primary production as an important carbon source within Potter Cove's benthic ecosystem. We propose that the microphytobenthic contribution to the total primary production may drop drastically due to Antarctic glacial retreat and correlated sedimentation and shading, with yet unknown consequences for the benthic heterotrophic community, its structure, and diversity.南极半岛的冰川正经历快速消退，这与颗粒物释放量增加、沉积作用增强存在显著关联，进而导致底栖初级生产可利用的光照资源大幅减少。本研究针对沉积作用与遮光模式的变化如何影响微型底栖藻类（microphytobenthos）的初级生产活动展开了探究。为测定微型底栖藻类群落的潜在净初级生产与呼吸作用，研究人员将取自不同沉积速率与遮光程度区域的沉积岩芯，暴露于0–70 微摩尔光子·米⁻²·秒⁻¹的光合有效辐射（photosynthetic active radiation，缩写PAR，波长范围400–700 nm）环境中。实验过程中，研究人员测定了总氧通量，以及微型底栖硅藻群落的结构、密度与生物量。本研究结果显示，微型底栖藻类的净初级生产随沉积作用增强与遮光程度加剧呈下降趋势，但其硅藻密度与群落组成并未发生明显改变。通过将实验结果与原位测得的PAR强度进行对比，本研究进一步评估了微型底栖藻类初级生产作为波特湾（Potter Cove）底栖生态系统中关键碳源的生态地位。研究人员据此提出，受南极冰川消退及相关联的沉积作用与遮光效应影响，微型底栖藻类对总初级生产的贡献可能会大幅下降，而这一变化对底栖异养群落的结构、多样性所造成的影响目前仍未明确。