Whole‐lake experiments: The annual record of fossil pigments and zooplankton

Abstract

The annual record of fossil pigments and zooplankton was compared with detailed contemporaneous records from two manipulated lakes from 1940 to 1986. Annually resolved sedimentary records accurately monitored known changes in plankton communities, identified periods of trophic change, and proved a powerful tool for examining long-term, complex interactions. Both Paul and Peter Lakes underwent the same three complete changes in their fish assemblages (trout, cyprinid, bass), and Peter Lake received repeated inputs of lime. Alterations in fish community composition produced long-lived changes in zooplankton communities that cascaded to the microbial level of the food web. Liming, in concert with trophic changes, caused distinctive phytoplankton dynamics in Peter Lake.Paleolimnological data recorded all major plankton dynamics known from coeval limnological data. Specifically, the sediment record showed transitions in cladoceran size structure and species composition, changes in water clarity resulting from both food web and chemical manipulations that affected vertical zonation of primary producers, and changes in absolute abundance of all algal divisions except dinoflagellates. Undegraded Chl a indicated deep blooms and, in conjunction with Chl c, fucoxanthin and P-carotene, indicated metalimnetic chrysophytes. Transient (2-3 yr) nonselective increases in sedimentation corresponded with increases in grazing rates. Isorenieratene indicated overlap of photic and anoxic zones, revealing changes in transparency and conditions for pigment preservation.

Rapid, local adaptation of zooplankton behavior to changes in predation pressure in the absence of neutral genetic changes

“…G ST values were lower than 0.022 in both cases (Fig. 4) (24,25). The strong fit between the egg-density profile and inferred fish predation pressure supports the notion that the Oud Heverlee sediment record is intact and not disturbed at either of our core sites.…”

Spatial distribution of diatom and pigment sedimentary records in surface sediments in Doubtful Sound, Fiordland, New Zealand

“…In contrast, several other aquatic studies have shown that alloxanthin (cryptophytes) can dominate carotenoid concentrations in surface sediments (Repeta & Gagosian 1987;Leavitt et al 1989;Hurley & Armstrong 1991). Goebel (2001) described a maximum of cryptophytes in the LSL just outside Deep Cove, which is supported by the elevated alloxanthin concentrations in the sediment traps at this site.…”

Trophic cascade and biomanipulation: Interface of research and management‐A reply to the comment by DeMelo et al

“…In designing tests for these ideas, we have favored an experimental approach (Carpenter 1988a;Carpenter and Kitchell 1988;Carpenter et al 199 1). Paleolimnological reconstructions (Kitchell and Carpenter 198 7;Leavitt et al 1989;Carpenter and Leavitt 199 l), longterm records (Mills et al 1987;Jassby et al 1990), and multilake comparative studies (Mills and Schiavone 1982;Pace 19 84;Carpenter et al 199 1) have also provided valuable evidence. Since DeMelo et al restrict their scope to experiments, we will not address other research approaches in our comment.…”

“…Evidence of those effects will typically take more time than the duration of most experiments. Recent results of paleolimnological studies offer confirmation of lag effects and the encouragement of an approach that can serve as a surrogate for longterm studies (Leavitt et al 1989;Carpenter and Leavitt 199 1).…”