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Checkley, DM.  1980.  The egg production of a marine panktonic copepod in relation to its food supply - Laboratory studies. Limnology and Oceanography. 25:430-446. AbstractWebsite

Egg production by Paracalanus parvus, a particle-grazingcopepod, was investigated in relation to its food supply. The concentration of available food (P) and the rates of ingestion (I) and egg production (B) were measured simultaneously at intervals of 6 h to 2 d for periods of 2-10 d. Concentration, chemical composition (carbon and nitrogen), and species of phytoplankton were experimental variables.Egg production was related to the food ingested during the previous day. For one food type, I and B were rectilinear functions of P. The average maximum rates of ingestion and egg production were 1.1 µg N ∙ female^-1 ∙ d^-1 and 53 eggs ∙ female^-1 ∙d^-1, equivalent to specific rates of 1.5 and 0.37 d^-1. B was proportional to I below a critical ingestion rate, Ic, and independent of I above Ic. For I < Ic, the gross efficiency of egg production (B ∙ I^-1) in terms of nitrogen was 0.37 while in terms of carbon it was a hyperbolic function of the ratio of C:N in the food, ranging between 0.41 (C:Nfood= 4.0) and 0.15 (C:Nfood= 11). For I >Ic, B ∙ I^-1 declined in terms of both carbon and nitrogen.These results, together with the ratio of C:N in particulate matteri n the sea off southern California, suggest that nitrogen (hence protein) potentially limits egg production by adult female Paracalanus and that ingested carbon is used inefficiently.

Checkley, DM, Entzeroth LC.  1985.  Elemental and isotopic fractionation of carbon and nitrogen by marine, planktonic copepods and implications to the marine nitrogen cycle . Journal of Plankton Research. 7:553-568.   10.1093/plankt/7.4.553   AbstractWebsite

Particle-grazing copepods, primarily Temora longicornis and T. stylifera, and seawater with natural particles were collected from the northwest Gulf of Mexico. Control and ammonium-enriched aliquots of seawater were incubated in triplicate for 2 days, copepods added and the incubation continued for 2 days. Analyses were made of dissolved nutrients (nitrate, ammonium and phosphate), suspended particles (chlorophyll a and phaeopigments, C, N, τ13C, τ15N), and copepod bodies and feces (C, N, τ13C, τ15N) and the rates of egg and feces production were estimated. Primary production Δchlorophyll a, C, N) was enhanced by N enrichment, indicating its initial N limitation. The rates of egg and feces production were greatest for copepods in N-enriched seawater, indicating food-limited ingestion and egg production. Elemental (C:N) and isotopic (τ13C, τ15N) fractionation by copepods occurred following ingestion of suspended particulate matter (spm) and during the production of tissue (b) and feces (f): C:Nf>C:Nspm >C:Nb, τ13Cb>τ13Cf>τ13Cspm, and τ15Nf>τ15Nb>τ15Nspm. In a second experiment, N-enriched and N-deficient phytoplankton were fed to Acartia tonsa and again C:Nf>C:Nspm>C:Nb. These data indicate that copepods in the present study (i) used nitrogen more efficiently than carbon for tissue production and (ii) produced tissue and feces enriched and excreta depleted in 13C and 15N relative to the suspended particulate matter. The implications of these results to the marine nitrogen cycle are discussed.

Checkley, DM, Dickson AG, Takahashi M, Radich JA, Eisenkolb N, Asch R.  2009.  Elevated CO2 Enhances Otolith Growth in Young Fish. Science. 324:1683-1683.   10.1126/science.1169806   AbstractWebsite

A large fraction of the carbon dioxide added to the atmosphere by human activity enters the sea, causing ocean acidification. We show that otoliths (aragonite ear bones) of young fish grown under high CO2 (low pH) conditions are larger than normal, contrary to expectation. We hypothesize that CO2 moves freely through the epithelium around the otoliths in young fish, accelerating otolith growth while the local pH is controlled. This is the converse of the effect commonly reported for structural biominerals.