Pigments From the Bottom Deposits of an English Lake

Abstract

Acetone-soluble pigments in the sediments of Esthwaite Water, English Lake District, have been separated and characterized chromatographically and spectrophotometrically. Chlorophyll degradation products similar to those described from North American lakes have been found to predominate but a-and (S-carotene, lutein, and two unidentified epiphasict carotenoids were also present. In an attempt to relate the amounts of these pigments at difiFerent depths to the ecological history of the lake and its catchment area, total amounts of chlorophyll degradation products, of epiphasic carotenoids (mainly p-earotene), and of hypophasici carotenoid (lutein), have been determined in samples taken at 10 cm intervals from a core reaching down into the glacial clays. The amounts of each of these three types of pigment were found to show a general correlation with the amounts of organic matter at different depths in the deposits and certain fiuctuations appear to be related to ecological changes in the past. The ratio of chlorophyll degradation products to epiphasic carotenoids has been found to remain nearly constant down to 100 cm, indicating that no appreciable decomposition of these pigments has occurred since the sediments were laid down, and below this to fiuctuate in a rather regular manner with peaks at about 53 cm intervals (a statistical examination of these fluctuations is included as an appendix). The ratio of chlorophyll degradation products to hypophasic carotenoid has been found to vary in a similar manner except for a general trend indicating the slow decomposition of lutein. These results suggest the occurrence of regular cyclic ecological changes from the Boreal period onwards which were interrupted at about A.D. 1000 by forest clearance.

STUDIES ON THE DEGRADATION OF CHLOROPHYLL a AND CAROTENOIDS IN FRESHWATERS

“…The conclusion that leaves do not contribute major amounts of pigments to the sediments of Abbot's Pond does not necessarily obviate the view (Fogg and Belcher, 1961) that deciduous leaf matter forms a large part of the organic material accumulating on the bottom of the English Lakes, since the leaf material may simultaneously contribute large amounts of total organic matter and small quantities of pigments. It is feasible that most of the finely divided surface sediment consists of algal and faecal remains, the organic matter of which is rapidly re-mineralized relative to the leaf material, which would then make up the bulk of the persistent material thereafter preserved.…”

“…i, therefore, is not explicable by contamination of the samples with carotenoid rich autumn leaf material. Fogg and Belcher (1961) point out that deficiency in nitrate can induce high carotenoid to chlorophyll ratios in cultures. Nitrate deficiency sometimes limits growth of epipelic diatom populations in Abbot's Pond and Priddy Pool (Eaton, 1967), but there was no evidence of colour changes in old algal populations in the w ater bodies studied.…”

“…This approach, however, is still open to the limitations noted above. Fogg and Belcher (1961) and Belcher and Fogg (1964) found statistically significant trends in the ratio of 'sedimentary chlorophyll degradation products' (SCDP) to carotenes and xanthophylls in cores from lake sediments in the English Lake District, but were unable to determine definitively the reasons for these trends.…”

“…Destruction of carotenoids also appears to be slow in sediments (Fogg and Belcher, 1961). Estimation of total carotenoids (TC) is less open to criticism, therefore, than estimation of total chlorophyll a derivatives as SCDP.…”

“…Satisfactory interpretation of the clearly non-random changes observed in the pigment composition of successive sediment layers (Vallentyne, 1955;Fogg and Belcher, 1961;Gorham, 1961;Belcher and Fogg, 1964) will depend on increased knowledge of at least three factors-the origin and nature of the pigments, the influence of physical, chemical and biotic agencies on pigment destruction, and the pigment composition of living plant populations. The present study was made possible by the evolution of a simple method of distinguishing chlorophyll a and chlorophyllide a from pheo a pigments (Moss, 1967a, b).…”