Abstract

Some of most used indicators in marine ecology are nucleic acid-derived indices. They can be divided by target levels in three groups: 1) at the organism level as ecophysiologic indicators, indicators such as RNA:DNA ratios, DNA:dry weight and RNA:protein, 2) at the population level, indicators such as growth rate, starvation incidence or fisheries impact indicators, and 3) at the community level, indicators such as trophic interactions, exergy indices and prey identification. The nucleic acids derived indices, especially RNA:DNA ratio, have been applied with success as indicators of nutritional condition, well been and growth in marine organisms. They are also useful as indicators of natural or anthropogenic impacts in marine population and communities, such as upwelling or dredge fisheries, respectively. They can help in understanding important issues of marine ecology such as trophic interactions in marine environment, fish and invertebrate recruitment failure and biodiversity changes, without laborious work of counting, measuring and identification of small marine organisms. Besides the objective of integrate nucleic acid derived indices across levels of organization, the paper will also include a general characterization of most used nucleic acid derived indices in marine ecology and also advantages and limitations of them. We can conclude that using indicators, such RNA:DNA ratios and other nucleic acids derived indices concomitantly with organism and ecosystems measures of responses to climate change (distribution, abundance, activity, metabolic rate, survival) will allow for the development of more rigorous and realistic predictions of the effects of anthropogenic climate change on marine systems.

Highlights

  • In marine ecology the determination of the in situ physiological state of marine organisms and communities are among of the main challenges

  • Measurements of metabolic activity have been especially valuable as indicators of condition in studies of marine organisms, groups for which accurate determination of field metabolic rates is difficult [1]

  • Molecular methods based on nucleic acid derived indices [2] and the polymerase chain reaction has recently become an important tool in this field [3]

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Summary

Introduction

In marine ecology the determination of the in situ physiological state of marine organisms and communities are among of the main challenges. Since the RNA:DNA ratio was first proposed 38 years ago as a biochemical indicator of the physiological and nutritional state of aquatic organisms in natural environment [5] it has been continuously explored [6,7,8,9,10] These indices have been applied with success in marine ecology in microbial communities’ [11] and in invertebrates and fishes [12,13,14,15,16]. There was an increase number of published studies using nucleic derived indices, such as RNA:DNA ratio, after 1990 (Figure 1) This was due to much progress been made in improving the sensitivity of analytical methods, with the application of fluorometric techniques allowing measurement at the individual level, of small marine organisms such as marine larvae and copepods. The advantages and limitations of them will be discussed

Organism level indices
Conclusions

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