Changes in depth and time of certain chemical and physical conditions and of the standing crop of Asterionella formosa Hass. In the North Basin of Windermere in 1947
Changes in depth and time of certain chemical and physical conditions and of the standing crop of Asterionella formosa Hass. In the North Basin of Windermere in 1947
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某些化学和物理条件以及 Asterionella formosa Hass 的直立作物的深度和时间的变化。
DOI：
10.1098/rstb.1963.0006
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发表时间：
1963
期刊：
影响因子：
--
通讯作者：
C. Mortimer
中科院分区：
文献类型：
--
作者：
J. Lund;F. Mackereth;C. Mortimer
30年来，温德米尔北部盆地浮游植物生产的年循环一直是淡水生物协会研究的主要对象。1947年提供了第一次联合尝试的机会——集中在最深处附近的水柱上——详细描述和解释温度、藻类细胞数量和选定的化学变量的年循环，目的是呈现开放水域条件的综合图景，以供其他不太详细或更专业的研究参考。从1947年1月2日至1948年1月12日，每隔一周或有时更频繁的间隔，以及在以下或有时更频繁的深度间隔，测量温度并采集样本进行浮游植物计数和化学分析（溶解和总二氧化硅、碱度、氧、硝酸盐和磷酸盐）；距离地面6米，距离地面2米，距离地面12米，距离地面15米，距离地面60米，距离地面5米。尽管冬季异常寒冷，夏季异常炎热，但年温度周期（图1）遵循正常进程。三月中旬冰消失后，等温条件一直持续到五月初。当月末，热分层开始形成；在夏季的大部分时间里，主要的温跃层位于9或10 m附近，偶尔会形成和破坏临时的温跃层。随着秋季的降温和风暴，温跃层深度增加，直到12月初重新建立等温条件。对整个盆地温度分布变化的平行研究（mortimer 1952年的另一篇论文的主题）揭示了风引起的等温线位移，随后是内部地震运动，其主导周期接近14小时。讨论了这些运动对选定水柱事件的影响。由于石柱位于海水淤积区附近，里面的情况与开阔水域的平均情况差别不大。垂直密度梯度最大的层（斜斜）如图2所示。相同的点画叠加在后面的图上，说明了密度分层与水柱中化学和生物不连续性的发展之间的强烈相关性。湍流混合和相关摩擦的抑制使斜斜具有光滑界面的性质；因此，在风的推动下，或在冰层的推动下，表层可以相对自由地滑动，而不会与下面的地层发生太多混合。在大部分季节里，由于表层深度与光层深度一致，浮游植物的生长主要局限于表层；从下面补充营养盐受到阻碍。虽然尾层的湍流足以使硅藻细胞悬浮，但背斜层的情况并非如此，它们可以被动地下沉，几乎没有机会返回。硅藻是温德米尔浮游植物的主要成员。本文给出了1932- 1961年期间北盆地季节循环的一般情况。1947年的事件周期遵循1932- 1961年的正常过程，通过图表详细描述了活细胞（图3）、总细胞（图4）、死细胞（图5）和每个群体的细胞数量（图6）在深度和时间上的分布。冬至作物产量低，早春开始增加，6月初达到最大值（0 - 8米水柱每升超过500万个细胞）。随着种群的增加，水中的硅酸盐浓度也相应下降（图7），下降到这样一个水平，即没有足够的水来支持再一次的直立作物划分。6月初，当硅酸盐供应不能再满足硅藻生长的需要时，出现了严重的死亡和尾膜细胞数量的灾难性下降，直到8月底，0至5米水柱中每升只有不到一个活细胞。死细胞数在活细胞数达到最大值几周后达到最大值，但从后脑膜中移除细胞的过程最终将那里的总数（和总二氧化硅，图8）降低到非常低的水平。后来从流入中补充了一些硅酸盐，但最大期后的主要特征是细胞通过沉降损失，因为单个死亡细胞和含有高比例死亡细胞的菌落下沉相对较快（图5、9）。在这一阶段，低阴离子上层的数量有所增加。但这只是暂时的，在水柱的最底层没有堆积，尽管在泥浆表面发现了一层死亡和垂死的细胞。根据本摘要第一段列出的化学变量的波动，讨论生物状况（特别是已经概述的硅藻种群的变化）与物理化学环境之间的关系。溶解二氧化硅和总二氧化硅分布的变化（图7、8）与硅藻生长密切相关，并在此用于推断硅藻总产量的大小和下沉损耗率（图9）。低氧阴离子的呼吸耗氧发生在泥浆表面和自由水中。夏季分层结束时的深度氧浓度分布（图11、13和表1至3）表明，实验室测量的泥浆表面的消耗速率高于湖泊中发生的消耗速率，或者氧气在低磷离子中发生了相当大的向下迁移。总呼吸耗氧量与沉积和溶解有机碳估算相结合，推断出湖泊的粗略碳收支。结果表明，浮游植物光合作用固定的碳只占进入湖泊总有机碳的一小部分。尾膜中碱度（图10）和硝酸盐浓度（图14）的变化反映了流入水体的季节变化；而且有证据（特别是从氧饱和度的分布来看，图12）表明，在湖表面的水平流动中，浅海沿岸地区的水变暖了。磷的浓度一般小于1jag /1，而低磷的浓度约为2jag /1，总是接近可靠估计的下限。然而，这些小浓度足以支持观察到的最大硅藻产量。深层沉积物对溶解营养物的浓度没有显著贡献，在整个观察期间，其表面保持有氧状态。
The annual cycle of phytoplankton production in the North Basin of Windermere has been a major object of study by the Freshwater Biological Association for 30 years. The year 1947 provided the first opportunity for a combined attempt—concentrated on the water column near the deepest point—to describe in detail and to interpret the annual cycle of temperature, algal cell numbers, and selected chemical variables, with the aim of presenting an integrated picture of openwater conditions, to which other less detailed or more specialized studies may be referred. Temperatures were measured and samples were taken for phytoplankton counts and for chemical analyses (dissolved and total silica, alkalinity, oxygen, nitrate, and phosphate) at weekly or sometimes more frequent intervals from 2 January 1947 to 12 January 1948 and at the following or sometimes more frequent depth intervals; every metre from the surface to 6 m, every 2 m to 12 m and every 5 m from 15 to 60 m. Although marked by an abnormally cold winter and hot summer, the annual temperature cycle (figure 1) followed a normal course. After the ice had disappeared in mid-March isothermal conditions prevailed until the beginning of May. Thermal stratification became established by the end of that month; the main thermocline lay near 9 or 10 m during most of the summer, and occasional temporary thermoclines were formed and destroyed. With autumnal cooling and storms, thermocline depth increased until isothermal conditions were re-established in early December. A parallel study of changes in temperature distribution in the whole basin (the subject of another paper—Mortimer 1952) disclosed a picture of wind-induced displacements of isotherms, followed by internal seiche motion with a dominant uninodal period near 14 h. The influence of these movements on events in the selected water column is discussed. As the column lay near the seiche uninode, conditions in it did not diverge widely from average conditions in the open water. The layer of greatest vertical density gradient (pycnocline) is shown stippled in figure 2. Identical stippling superimposed on later figures illustrates the strong correlation between density stratification and the development of chemical and biological discontinuities in the water column. Suppression of turbulent mixing and of associated friction gave the pycnocline the properties of a slippery interface; and the epilimnion, driven by wind or impelled by seiches, could therefore slide relatively freely without much mixing with layers below. As epilimnion depth coincided with that of the photic layer for much of the season, phytoplankton growth was largely confined to the epilimnion; and replenishment of nutrient salts from below was impeded. While turbulence in the epilimnion was sufficient to keep diatom cells in suspension, this was not so in the pycnocline, where they could sink passively through with little chance of return. The diatom Asterionella is the dominant member of Windermere phytoplankton. A general account of the seasonal cycle in the North Basin is given for the period 1932-61. The cycle of events in 1947, which followed the normal course for the period 1932-61, is described in detail with the aid of diagrams showing the distribution of live cells (figure 3), total cells (figure 4), dead cells (figure 5), and number of cells per colony (figure 6) in depth and time. The crop was low in midwinter, started to increase in early spring, and reached maximum numbers (over 5 million cells per litre in the 0 to 8 m water column) in early June. As the population increased there was a corresponding fall in concentration of silicate in the water (figure 7) to a level at which there was not enough remaining to support one more division of the standing crop. When, in early June, silicate supply could no longer meet the demands of diatom growth, there was a heavy mortality and a catastrophic decline in cell numbers in the epilimnion, until, by late August, there was less than one live cell per litre in the 0 to 5 m water column. Dead cells reached a maximum some weeks after the live cell maximum, but processes removing cells from the epilimnion eventually reduced total numbers (and total silica, figure 8) there to very low levels. Some silicate replenishment from inflows later occurred, but the main feature of the post-maximum phase was loss of cells through the pycnocline, because single dead cells, and colonies containing a high proportion of dead cells, sank relatively rapidly (figures 5, 9). During this phase there was some increase of numbers in the upper layers of the hypolimnion. But this was only temporary, and there was no accumulation in the lowest layers of the water column, although a layer of dead and dying cells was found on the mud surface. The relationships between the biological situation—in particular the changes in diatom population, already outlined—and the physico-chemical environment are discussed in the light of fluctuations in the chemical variables listed in the first paragraph of this summary. Changes in the distribution of dissolved and total silica (figures 7, 8) were closely related to diatom growth, and are here used to infer the magnitude of total production of diatoms and rates of loss by sinking (figure 9). Respirational consumption of oxygen in the hypolimnion occurred both at the mud surface and in the free water. The distribution of oxygen concentration in depth at the end of summer stratification (figures 11, 13, and tables 1 to 3) suggests, either that the rate of consumption at the mud surface measured in the laboratory is higher than that occurring in the lake, or that considerable downward migration of oxygen occurred within the hypolimnion. Total respirational oxygen consumption is used, in conjunction with sedimentary and dissolved organic carbon estimates, to infer a rough carbon budget for the lake. It is concluded that the carbon fixed by phytoplanktonic photosynthesis was a small proportion of the total organic carbon entering the lake. Changes in alkalinity (figure 10) and nitrate concentration (figure 14) in the epilimnion reflected seasonal changes in the inflowing water; and there was evidence (particularly from distribution of oxygen saturation, figure 12) of horizontal flow, out over the lake surface, of water warmed in shallow littoral areas. The concentration of phosphate, always near the lower limit of reliable estimation, was generally less than 1 jag/1, in the epilimnion and about 2 jag/1, in the hypolimnion. These small concentrations were, however, sufficient to support the observed maximum diatom crop. No significant contribution to the concentration of dissolved nutrients was derived from the deep sediments, the surface of which remained aerobic throughout the period observed.