Hypoxic effects on growth of Palaemonetes vulgaris larvae and other species: Using constant exposure data to estimate cyclic exposure response.

First stage larval marsh grass shrimp, Palaemonetes vulgaris, were exposed to patterns of diurnal, semidiurnal, and constant hypoxia to evaluate effects on growth and to determine if there was a consistent relationship between exposures. A comparison of growth with cyclic exposures versus constant low dissolved oxygen (D.O.) concentrations equivalent to the minima of the cycles showed the cyclic exposures resulted in less growth impairment than constant low-D.O. exposures, when compared to saturated controls. The mean extent of growth impairment of cyclic hypoxia was, however, almost 1.5 times more than would be estimated using an arithmetic time-weighted-average of the hypoxic portion of the cycle. Additional testing with other life stages and species resulted in similar patterns of response. Based on this relationship, an adjusted time-weighted-average could be used to estimate field related responses to cyclic dissolved oxygen from laboratory-derived constant exposure data.