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Carbon: pheopigment ratios of zooplankton fecal pellets as an index of herbivorous feeding 1
Author(s) -
Downs Jan Newton,
Lorenzen Carl J.
Publication year - 1985
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1985.30.5.1024
Subject(s) - copepod , zooplankton , phytoplankton , photic zone , bay , pellets , biology , calanus , zoology , ecology , environmental chemistry , oceanography , nutrient , chemistry , crustacean , paleontology , geology
A simple model using carbon to pheopigment ratios (C:Ph) to estimate the fraction of carbon derived from recently ingested phytoplankton was used on fecal pellets from laboratory‐fed Calanus pacificus and field zooplankton and on sediment trap material from Dabob Bay, Washington. During the grazing season of herbivorous macrozooplankton, fecal pellets from laboratory‐fed C. pacificus have C : Ph ratios of 7–13, yielding calculated copepod assimilation efficiencies (AE%) of 77%. Diapausal copepods produce pellets with higher C : Ph ratios (24–33) and yield lower calculated AE% (46%), suggesting reduced digestive enzyme activities at this time. On the basis of measurements of field phytoplankton C : Chl and estimates of field copepod assimilation efficiencies, the C : Ph ratio of fecal pellets from exclusively herbivorous field copepods ranges from 11 to 18. Higher values (25–29) found from naturally feeding copepods indicate a significant amount of omnivory, carnivory, or both. The amount of the total organic carbon flux out of the euphotic zone in Dabob Bay resulting from herbivorous feeding was quantified. Its magnitude was directly related to the primary productivity and the seasonal grazing pattern of C. pacificus, averaging 36% when grazers are actively feeding and 9% when many are in diapause. On an annual basis, 31% of the carbon flux out of the surface layer in Dabob Bay is derived from ingested or sunken phytoplankton cells.