Use of RNA:DNA ratios for assessing secondary production of planktonic food webs effects of temperature, salinity, food and heavy metals /
Abstract (Summary)Acartia tonsa is a dominant copepod in coastal waters and is an important link in the food web between microplankton and higher trophic levels. RNA:DNA ratios have been used to describe growth and nutritional condition of field collected copepods and to show strong correlation between group egg production and RNA:DNA ratios. A method was developed using a sensitive, nucleic acid fluorescent dye and automated microplate fluorometer to measure RNA, DNA and RNA:DNA ratio of individual A. tonsa. RNA, DNA, RNA:DNA ratios and egg production were all significantly higher in copepods fed Thalassiosira spp. compared to starved copepods. There was a general trend toward an increase in RNA:DNA ratios with increase in egg production, but due to the high degree of variation in both RNA:DNA ratios and egg production of individual copepods no significant correlation between RNA:DNA ratios and egg production was found. Significant differences in the RNA:DNA ratios between fed (7.2) and starved (3.4) copepods were found after 2 days. In the future this assay may be applied to other species of copepods sampled directly from the field, to provide an index of the health of planktonic food webs in nature.
School Location:USA - Texas
Source Type:Master's Thesis
Keywords:copepoda rna dna marine plankton
Date of Publication: