A qualitative study of zooplankton grazing in an oligo‐mesotrophic lake using phytoplanktonic pigments as organic markers

Abstract

The impact of grazing by various zooplankton fractions (calanoid copepods, cyclopoid copepods, cladocerans, and small‐sized zooplankton: 80–315 µm) on various phytoplankton groups was measured in Lake Pavin (Central Massif, France) by means of phytoplankton pigments separated by HPLC as natural organic markers. The impact of grazing was determined from April to November in the depth‐sampling layers (0–7 and 7–20 m) in which most zooplankton organisms were concentrated. Selective grazing by consumers created spatial (vertical) and temporal variation in mortality exerted on the various phytoplankton groups. For example, the avoidance of dinoflagellates (characterized by peridinin) by most of the zooplankton organisms studied led to low grazing impacts (<280 ml liter‒1 d‒1) on this phytoplankton group during all seasons. In contrast, preferential consumption of diatoms and chrysophytes (characterized by fucoxanthin) and chlorophytes and cyanobacteria (characterized by lutein and zeaxanthin) was recorded, depending on the zooplankton fraction in question. The grazing impact exerted on these phytoplanktonic groups was much higher than that measured on dinoflagellates, reaching values of 2,300 ml liter‒1 d‒1. Grazing mostly affected diatoms and chrysophytes in the 0–7‐m layer and chlorophytes and cyanobacteria in the 7–20‐m layer; the differences between these two layers were related to the heterogeneity in the vertical distribution of both phytoplankton cells and grazing organisms.

Characteristics of phytoplankton community structure during and after a bloom of the dinoflagellate Scrippsiella trochoidea by HPLC pigment analysis

“…Chl a samples were stored in a freezer. Phytoplankton pigments were analysed within one month after sampling to minimize the loss of pigments (Wright et al, 1991;Quiblier-Llobéras et al, 1996).…”

Terrestrial carbon contribution to lake food webs: could the classical stable isotope approach be misleading?

“…Pigments were extracted and analyzed using an ion-pairing reagent solution (0.75 g tetrabutyl ammonium acetate and 7.7 g ammonium acetate in 100 mL of Easy-Pure water; Quiblier-Lloberas et al 1996). Briefly, all samples were ground in 5 mL of 90% high-performance liquid chromatography (HPLC)-grade acetone and transferred into scintillation vials (5 mL).…”

“…Zooplankton samples intended for pigment analyses were anaesthetized in carbonated water to prevent regurgitation (Quiblier-Lloberas et al 1996), immediately put in the dark onto dry ice to limit organic matter degradation, and kept at cryogenic temperature (-80 8C) in the lab. Samples intended for isotope analyses were maintained in lake-filtered water overnight for gut clearance.…”

History of anthropogenically mediated eutrophication of Lake Peipsi as revealed by the stratigraphy of fossil pigments and molecular size fractions of pore-water dissolved organic matter

“…As mentioned previously, canthaxanthin has been widely detected also in herbivores. Moreover, when Quiblier-Llobéras et al (1996) observed the summer planktonic community in an oligo-mesotrophic lake, canthaxanthin was found only in zooplankton, but it Table 2 Spearman rank order correlations for selected characteristics of pore-water dissolved organic matter (pDOM) and fossil pigments obtained by different methods (given in parentheses) for the analysed sediments of Lake Peipsi Pair of characteristics Spearman P-level was totally absent from phytoplankton. In the case of Lake Peipsi, further investigations should be conducted to determine whether canthaxantin is a marker pigment of specific cyanobacteria taxa or whether it is confined to herbivores.…”