Aphotic pigment degradation in the hypolimnion: Implications for sedimentation studies and paleolimnology

Abstract

Reversed‐phase high pressure liquid chromatography was used to quantify carotenoid and Chl degradation resulting from bacterial and microfaunal action during aphotic, hypolimnetic incubations of natural phytoplankton assemblages and detrital material in three lakes. Decay of carotenoids (to −0.0870 d−1) and chlorophylls (to −0.1226 d−1was potentially rapid but site‐specific. Chl a decay spanned a wide range (to −0.1226 d−1) with greatest losses in circumneutral, unstained Peter Lake and least in acidic, stained Tuesday Lake. The usefulness of Chl a as an indicator of algal sedimentation was compromised by its rapid degradation, lack of compensatory production of recognizable derivatives, and an abundance of unknown, chlorophyllous compounds. β‐carotene degraded less rapidly and variably (to −0.0167 d−1) and is a useful addition to both sedimentation and paleolimnological studies. Differences among ca rotenoids in decay pose difficulties in reconstructing accurate estimates of former algal community composition, especially dinoflagellates, whose peridinin decays rapidly (−0.0843 d−1). Changes in the relative (within‐core) abundance of individual pigments may be combined, however, with changes in Chl a : β‐carotene ratios to differentiate between periods of enhanced productivity (or pigment preservation) and changes in the vertical zonation of algal communities.

Short-term variability in pelagic-benthic exchange of phytopigments and their relations to benthic bacterial variables in the North Sea

“…The decrease in benthic phytopigments might be due to selective burial by mixing activities of macrofauna, but it is also likely that part of the decrease was due to decomposition/transformation reactions in situ. Pigment degradation following first-order kinetics resulted in decay rates, which were of the same order of magnitude as found by others (Leavitt & Carpenter 1990, Abele-Oeschger 1991, Sun et al 1993b). Contrary to CH and FU, PH and the PH/CH ratio were significantly related to BBP and BBN respectively.…”

Zooplankton effects on vertical particulate flux: Testable models and experimental results

“…Estimates of sinking loss based on chlorophyll sedimentation may underestimate actual loss rates because chlorophyll degrades rapidly after cell death (Leavitt and Carpenter 1990). To examine the magnitude of this bias, sinking loss rates were estimated with microscopic counts of phytoplankton in sediment traps and the euphotic zone during the 1989 enclosure experiment (see Sarnelle 1993 for details on phytoplankton counting methods).…”

Effects of ultraviolet radiation on periphyton in an alpine lake

“…Pigments were extracted in the field with acetone : methanol : water (80 : 15 : 5 by volume; Leavitt and Carpenter 1990). Extracts were stored in the dark in a 5°C stream for 3 d until transportation (at OOC) to the laboratory.…”