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首页> 外文期刊>Lakes & Reservoirs >Impact of light regimen and self-shading by algal cells on primary productivity in the water column of a shallow tropical lake (Lake Naivasha, Kenya)
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Impact of light regimen and self-shading by algal cells on primary productivity in the water column of a shallow tropical lake (Lake Naivasha, Kenya)

机译：藻类细胞的光疗和自我遮荫对热带浅水湖（肯尼亚奈瓦夏湖）水柱初级生产力的影响

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Light is the factor that fundamentally determines the level of primary production. Primary productivity is controlled by bottom-up factors (nutrient levels), with secondary effects due to biological factors (zooplankton grazing). The light regimen experienced by algae is determined largely by mixing of the water column. The processes of photoinhibition and light attenuation combine with the resultant light–dark adaptation to shape the vertical productivity profile and it is important to determine their importance separately because they vary spatially and temporally. Daily variations in productivity can be as large as longer-term changes and events causing high productivity may not be important in whole-lake terms. At approximately 0.5 m depth, there is maximal photosynthesis causing depletion of nutrients, but there is vertical homogeneity in productivity control and horizontal similarity in productivity levels. There is zero productivity below 5 m depth due to light attenuation but, if the benthos becomes productive due to an environmental change, such as decreased turbidity, overall productivity may rise appreciably. Self-shading was investigated by incubating serial dilutions of whole lakewater with filtered water to reduce the density of algal cells. Photosynthetic efficiency was calculated as productivity per unit of chlorophyll a. Self-shading showed different responses for conditions of ‘low’ and ‘high’ productivity. With low productivity, there was a shading loss of 17%, while for high productivity this was 46%. Thus, self-shading is seen to have a considerable impact on potential productivity and may affect phytoplankton–cyanobacterial community structure with implications for lake management.
机译：光线是从根本上决定初级生产水平的因素。初级生产力由自下而上的因素（营养水平）控制，而由于生物学因素（浮游动物的放牧）而产生次级影响。藻类所经历的光照方案主要取决于水柱的混合。光抑制和光衰减的过程与所产生的明暗适应相结合，以形成垂直的生产率曲线，因此，重要的是要分别确定其重要性，因为它们在空间和时间上都会变化。生产率的每日变化可能与长期变化一样大，而导致高生产率的事件可能对整个行业而言并不重要。在大约0.5 m的深度处，最大程度的光合作用会导致养分消耗，但生产力控制方面存在垂直同质性，生产力水平方面存在水平相似性。由于光的衰减，在5 m深度以下的生产率为零，但是，如果由于环境变化（例如浊度降低）而使底栖动物变得有生产力，则总体生产率可能会明显提高。通过将整个湖水的连续稀释液与过滤水一起孵育以减少藻类细胞的密度，研究了自身遮光性。光合作用效率被计算为每单位叶绿素a的生产率。自阴影显示出对于“低”和“高”生产率条件的不同反应。生产率低时，遮光损失为17％，而生产率高时为46％。因此，自遮荫被认为对潜在生产力有相当大的影响，并可能影响浮游植物-蓝细菌群落结构，从而影响湖泊管理。

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