Some relationships between algal standing crop, water chemistry, and sediment chemistry in the English lakes

Estimates of standing crop, derived approximately from algal counts in surface waters, have been used to separate the English Lakes into three groups of low, intermediate, and high fertility. The fertile lakes are proportionally poorer than the infertile lakes in p-algae, but richer in “large algae” and Cyanophyta. The fertile lakes are richer in dissolved ions, especially calcium and bicarbonate, in filter-passing and particulate vitamin Bx, in sedimentary sulfur, and in sedimentary chlorophyll derivatives and carotenoids. The relationship noted by Pearsall between lake fertility and agricultural activity is shown by a strong correlation between algal standing crop and the percentage of the drainage basin under cultivation. Sediment ratios of carbon to sulfur and of chlorophyll derivatives to carotenoids decline with increasing lake fertility, whereas the ratio of carbon to nitrogen shows little change. This study lends support to the use of sedimentary pigments as indicts to lake productivity. The pigment data also indicate that much of the organic matter in sediments of productive lakes comes from autochthonous sources within the lakes.