Phytoplankton pigments tn macrozooplankton feces: variability in carotenoid alterations

During a period of 8 d in late September and early October 1992, 5 grazing experiments were carried out in an area off the coast of Morocco. Water was collected from the depth of the chlorophyll maximum and fed to copepods of either 500 to 1000 pm or 200 to 500 pm in size. Two chlorophylls and 2 carotenoids dominated the pigment composition of the particulate material: chlorophyll (chl) a; chl c (c, + cz); fucoxanthin and 19-hexanoyloxyfucoxanthin. Initial concentrations of chl a in experiments were between 0.4 and 2.2 pg I-' and those of chl c were between 0.04 and 0.54 pg 1-' Initial concentrations of fucoxanthin were between 0.1 and 1.1 pg I-' and those of 19-hexanoyloxyfucoxanthin between 0.07 and 0.32 pg 1-l. The ratio of fucoxanthin:l9-hexanoyloxyfucoxanthin varied between 0.3 and 15 (w/w). The fucoxanthin was probably associated with diatoms and the 19-hexanoyloxyfucoxanthin w~t h prymnesiophytes. Some chl a-derived fluorescent breakdown products were found in faecal pellets collected after grazing, but neither fucoxanthin nor 19-hexanoyloxyfucoxanthin were present. Hence these carotenoids were destroyed following ingestion by copepods, so that decreases in their concentrations in the incubation medium could be used to measure grazing rates on the different types of phytoplankton independently. In this way it was shown that copepods 500 to 1000 pm in size fed preferentially on diatoms, and that their overall feeding rate was depressed when fucoxanthin: 19-hexanoyloxyfucoxanth~n ratios were relatively low. By contrast, copepods 200 to 500 pm in size fed randomly or preferred the prymnesiophytes. When chl a concentrations were initially < 1 pg I-', then for both size ranges of copepods, only a very small proportion (< 10%) of the ingested chl a was converted into a-type phaeopigments, the rest apparently being destroyed during digestion. In one case, however, when copepods 200 to 500 pm were fed with water in which the initial chl a concentration was > 2 pg I-', about 30% of ingested chl a was recovered in a-type phaeopign~ents.

Section: Introductioncontrasting

confidence: 57%

Feeding selectivity by copepods grazing on natura: mixtures of phytoplankton determined by HPLC analysis of pigments

Head¹,

Harris²

1994

“…Undegraded carotenoids are found in copepod guts (Keppel 1988) and faecal pellets (Nelson 1989, Roy et al 1989). The same is true for accessory chlorophylls (Vernet & Lorenzen 1987).…”

Section: Phaeocystis Pouchetii Blooms and Vertical Flux Of Organic Mamentioning

confidence: 99%

Mass sedimentation of Phaeocystis pouchetii in the Barents Sea

Wassmann¹,

Vernet²,

Mitchell³

et al. 1990

180

102

Mass sedimentation of gelatinous colonies of the prymensiophyte Phaeocystis pouchetii were observed in the upper 100 m of Atlantic water in the central Barents Sea. Sedimentation rates of particulate organic carbon and nitrogen as well as pigments were the highest recorded so far from oceanic environments of the North Atlantic or coastal areas of Norway. High relative concentrat~ons of phytoplankton pigments found in the traps are interpreted as a combination of sinlung of intact phytoplankton cells and undegraded pigments present in macrozooplankton faecal pellets. Evldence presented in this study implies that the zooplankton community of the Barents Sea was not able to control this phytoplankton spnng bloom. The suspended and sedimenting organic matter was rlch in carbon and pigments, but poor in nitrogen. This is explained by the presence of large amounts of carbon-rich mucilage which P. pouchetii colonies develop during their development. In addition to diatoms, sedimentation of a gelatinous phytoplankton species like P. pouchetii may contribute significantly to the formation of marine snow and vertical flux from the euphotic zone. However, degradation of P. pouchetii derived detritus at depths less than 100 m greatly diminishes the likely significance of P. pouchetii blooms in processes such as the carbon flux to the deep ocean and sequestering of CO2.

“…The pigment degradation during digestive processes has been largely investigated in the grazing experiments of copepods (Kleppel & Pieper 1984, Nelson 1989, Swalding & Marcus 1994, BuffanDubau et al 1996. In contrast, few data are available on the pigment destruction in the gut of bivalves (Numagushi 1985, Hawkins et al 1986, Bayne et al 1987, Pastoureaud et al 1996.…”

Section: Stationmentioning

confidence: 99%

Phytoplankton composition and selective feeding of the pearl oyster Pinctada margaritifera in the Takapoto lagoon (Tuamotu Archipelago, French Polynesia):in situ study using optical microscopy and HPLC pigment analysis

Loret¹,

Pastoureaud²,

Bacher³

et al. 2000

The in situ diet of the pearl oyster Pinctada margaritifera was determined in the lagoon of Takapoto Atoll by comparing the phytoplankton composition of water and bivalve gut contents using 2 different methods, optical microscopy and HPLC pigment analysis. In order to evaluate the available food resources for pearl oysters in the water column, a new method for estimating the pigment/chlorophyll a (chl a) ratio (based on an inverse analysis) was developed which allowed us to determine the contribution of the main phytoplanktonic groups in terms of chl a. In the water, picocyanobacteria and nanoflagellates predominated, the latter being mainly chlorophytes and prymnesiophytes. Comparisons between the results obtained by the 2 methods of investigation indicated that most of the dinoflagellates are unpigmented and, therefore, heterotrophic. An examination of the gut contents showed that picocyanobacteria were only weakly ingested by the oyster and, thus, nanoflagellates constituted the main food resource. Cryptophytes, although poorly represented in the water, were preferentially ingested. Chlorophytes were inefficiently hgested since they were found alive and motile in the faeces of the oyster. The ecological implications of this feeding behaviour are discussed.