The Southern Ocean (SO) is a fragile ecosystem as judged by changes in the timing of the advance and retreat of its ice cover. In the SO, the Antarctic Circumpolar Current (ACC) and the near shore gyres (Weddell Sea and Ross Sea) provide local environments with distinct temperature and salinity attributes associated with varying sea ice history. Phaeocystis antarctica is a prymnesiophyte often dominating polar phytoplankton blooms in the (SO) and is a keystone species there because its abundance can have negative effects on higher trophic levels and it can influence air/sea gas exchange involved in DMSP production, Thus, its ability to survive in response to perturbations in the environments may be linked to its genetic diversity within its populations as they move around the SO. Here we apply increased (70 PSU) and decreased (18 PSU) salinity treatments to five genetically different P. antarctica strains isolated from three different water masses to test whether genetic similarity or water mass physical features were more important in determining responses to salinity changes, such as those encountered by inclusion into sea ice brine channels and/or its subsequent melt water in those water masses that have annual ice cover. Strains that were geographically close (isolated from the same water mass), but genetically distinct (ca. 30% similar and from different gene pools as judged by microsatellite (MS) and amplified fragment linked polymorphisms (AFLP) analyses responded similarly to higher and lower salinity regimes, whereas genetically close strains (ca. 95% identical or from the same gene pool) that originated from different water masses and hence different environmental conditions responded differently. Dimethylsulphoniopropionate (DMSP) production in response to these salinity changes were not significantly different between any of the strains/treatments. Considering the presence of highly similar genotypes in ice-free as well as seasonally ice covered sampling sites, the observed phenotypic differences most likely result from rapid local adaptation between both habitat types or a hybridization of isolates from the two gene pools with the resultant genotype for salinity tolerance being that from which the isolate originated, suggesting that the selective effect of seasonal presence or year-round absence of sea ice overrides gene flow between these habitats to adapt the physiology of cells to the environment in a relatively short period of time.

根据其冰盖进退时间的变化判断，南大洋是一个脆弱的生态系统。在南极洲，南极极地洋流（ACC）和近岸回旋带（Weddell Sea和Ross Sea）为当地环境提供了不同的温度和盐度属性，并伴随着不同的海冰历史。球形棕囊南极洲往往是主导极性浮游植物prymnesiophyte华在（SO）是一个关键物种存在，因为它的存在，会具有较高营养水平的负面影响，它会影响参与DMSP生产空/对海气交换，因此，它的能力为了应对环境中的干扰而生存下来，可能与其它们在SO周围移动时其种群内的遗传多样性。在这里，我们对五个遗传上不同的南极疟原虫应用盐度增加（70 PSU）和盐度降低（18 PSU）治疗分离自三种不同水团的菌株，以测试遗传相似性或水团物理特征在确定盐度变化的响应中是否更重要，例如盐分包含在海冰盐水通道和/或其后续融化水中时遇到的盐分变化有每年的冰盖。地理上接近的菌株（分离自相同水质），但遗传上不同（约30％相似，通过微卫星（MS）和扩增的片段连锁多态性（AFLP）分析判断，来自不同的基因库）对更高和更低的响应相似盐分制度，而源于不同水量并因此不同环境条件的遗传接近菌株（约95％相同或来自相同基因库）的反应也不同。响应于这些盐度变化的二甲基磺酸丙二酸酯（DMSP）的生产在任何菌株/处理之间均无显着差异。考虑到在无冰以及季节性冰覆盖的采样点中存在高度相似的基因型，观察到的表型差异很可能是两种生境类型之间快速的局部适应性或来自两个基因库的分离株与由此产生的基因型杂交的结果。盐分耐受性是分离物起源的盐分耐受性，表明季节性存在或全年不存在海冰的选择性作用会覆盖这些生境之间的基因流，从而在相对较短的时间内使细胞的生理适应环境。