为了研究紫外线辐射的影响(UVR,280-400nm)在营养有限的条件下,我们种植了Gephyrocapsaoceanica,以确定其在硝酸盐可用性范围(100、24、12、6和3μM)下对连续每日短期暴露于UVR(辐照度>295nm)的抵抗力。+仅UVR就严重阻碍了G.oceanica的生长,+UVR和N限制的协同负面影响比单独的UVR或N限制高约58%和22%,分别。大多数3μM硝酸盐培养物死亡,但是那些暴露于UVR的人更快屈服了。这是由于在暴露于UVR的低N可用性下的光保护和修复机制失败。此外,UVR诱导的对光系统II(PSII)的有效量子产率的抑制作用明显更高,并且由于N限制而进一步加剧。藻类细胞优先增加光保护色素和吸收紫外线的化合物,而不是使用钙化来防御UVR,表明能源和资源分配的权衡。我们的结果表明UVR对球藻生长和光合作用的负面影响,并强调了N可用性在防御UVR和高PAR中的重要作用。我们预测,由于变暖引起的分层,未来表层海洋中N限制的增强将加剧G.oceanica对UVR的敏感性,而由于营养限制水平的增加,球藻可能更容易受到其他环境压力的影响。
To investigate effects of UV radiation (
UVR, 280-400 nm) on coccolithophorids under nutrient-limited conditions, we grew Gephyrocapsa oceanica to determine its resilience to consecutive daily short-term exposures to +
UVR (irradiances >295 nm) under a range of nitrate availabilities (100, 24, 12, 6 and 3 μM). +UVR alone significantly hampered the growth of G. oceanica, with the synergistic negative effects of +
UVR and N-limitation being about 58% and 22% greater than under
UVR or N-limitation alone, respectively. Most 3 μM nitrate cultures died, but those exposed to
UVR succumbed sooner. This was due to a failure of photoprotection and repair mechanisms under low N-availability with exposures to UVR. Additionally, the UVR-induced inhibition of the effective quantum yield of photosystem II (PSII) was significantly higher and was further aggravated by N limitation. The algal cells increased photoprotective pigments and UV-absorbing compounds as a priority rather than using calcification for defense against UVR, indicating a trade-off in energy and resource allocation. Our results indicate the negative effects of UVR on coccolithophorid growth and photosynthesis, and highlight the important role of N availability in defense against
UVR as well as high PAR. We predict that enhanced N-limitation in future surface oceans due to warming-induced stratification will exacerbate the sensitivity of G. oceanica to UVR, while coccolithophores can be potentially more susceptible to other environmental stresses due to increased levels of nutrient limitation.