Phaeocystis antarctica is an important primary producer in the Southern Ocean and plays roles in sulfur cycles through intracellular production of dimethylsulfoniopropionate (DMSP), a principal precursor of dimethyl sulfide (DMS). Haptophytes, including P. antarctica, are known to produce more DMSP than other phytoplankton groups such as diatoms and green algae, suggesting their important contribution to DMS concentrations in the Southern Ocean. We assessed how sea ice formation and melting affect photosynthesis and DMSP accumulation in P. antarctica both in seawater and in sea ice. Incubations were undertaken in an ice tank, which simulated sea ice formation and melting dynamics. The maximum quantum yield of photochemistry (F_v/F_m) in photosystem II, as estimated from pulse‐amplitude‐modulated (PAM) fluorometry, was generally higher under low‐light conditions than high‐light conditions. Values of F_v/F_m, the relative maximum electron rate (rETR_max), and photosynthetic efficiency (α) were lower in sea ice than in seawater, implying reduced photosynthetic function inside the sea ice. The reduction in photosynthetic function was probably due to the hypersaline environment in the brine channels. Total DMSP (DMSPt) concentration normalized by chlorophyll‐a concentration was significantly higher in the sea ice than in the other environments, suggesting high accumulation of DMSP, probably due to its osmotic properties. F_v/F_m, specific growth rate, and DMSPt concentrations decreased with decreasing salinity with the lowest values found at a salinity of 22, that is, the lowest salinity tested. These results suggest that sea ice melting is responsible for a reduction in growth rate and DMSP production of P. antarctica.

中文翻译：

---

冰融化可以改变南极足类植物囊藻的DMSP产量和光合活性。

南极Phaeocystis南极洲是南大洋重要的主要生产国，通过细胞内产生二甲基硫代丙酸二甲酯（DMSP）（二甲基硫醚（DMS）的主要前体）在硫循环中发挥作用。已知包括南极疟原虫在内的七足类植物比其他浮游植物类（如硅藻和绿藻）产生的DMSP更高，表明它们对南大洋中DMS浓度的重要贡献。我们评估了海冰的形成和融化如何影响海水和海冰中南极体育的光合作用和DMSP积累。在一个冰罐中进行孵化，该罐模拟了海冰的形成和融化动力学。光化学的最大量子产率（F _v /根据脉冲幅度调制（PAM）荧光测量法估算，光系统II中的F _m）通常在弱光条件下要比强光条件下更高。海冰中的F _v / F _m值，相对最大电子率（rETR _max）和光合效率（α）均比海水中的值低，这意味着海冰内部的光合功能降低。光合功能的降低可能是由于盐水通道中的高盐环境造成的。叶绿素a归一化的总DMSP（DMSPt）浓度海冰中的浓度显着高于其他环境，这表明DMSP的高积累可能是由于其渗透特性。F _v / F _m，比生长速率和DMSPt浓度随着盐度的降低而降低，盐度最低的值为22，即所测试的最低盐度。这些结果表明，海冰融化是导致南极假单胞菌生长速率下降和DMSP产生的原因。