Estimation of Fish Biomass Using Environmental DNA

Environmental DNA (eDNA) from aquatic vertebrates has recently been used to estimate the presence of a species. We hypothesized that fish release DNA into the water at a rate commensurate with their biomass. Thus, the concentration of eDNA of a target species may be used to estimate the species biomass. We developed an eDNA method to estimate the biomass of common carp (Cyprinus carpio L.) using laboratory and field experiments. In the aquarium, the concentration of eDNA changed initially, but reached an equilibrium after 6 days. Temperature had no effect on eDNA concentrations in aquaria. The concentration of eDNA was positively correlated with carp biomass in both aquaria and experimental ponds. We used this method to estimate the biomass and distribution of carp in a natural freshwater lagoon. We demonstrated that the distribution of carp eDNA concentration was explained by water temperature. Our results suggest that biomass data estimated from eDNA concentration reflects the potential distribution of common carp in the natural environment. Measuring eDNA concentration offers a non-invasive, simple, and rapid method for estimating biomass. This method could inform management plans for the conservation of ecosystems

Release of Extracellular Transformable Plasmid DNA from Escherichia coli Cocultivated with Algae

We studied the effects of cocultivation with either Euglena gracilis (Euglenophyta), Microcystis aeruginosa (Cyanophyta), Chlamydomonas neglecta (Chlorophyta), or Carteria inversa (Chlorophyta) on the production of extracellular plasmid DNA by Escherichia coli LE392(pKZ105). Dot blot hybridization analysis showed a significant release of plasmid DNA by cocultivation with all the algae tested. Further analysis by electrotransformation confirmed the release of transformable plasmid DNA by cocultivation with either E. gracilis, M. aeruginosa, or C. inversa. These results suggest algal involvement in bacterial horizontal gene transfer by stimulating the release of transformable DNA into aquatic environments

Seasonal Distribution of Cyprinid Herpesvirus 3 in Lake Biwa, Japan▿ †

The seasonal distribution of the cyprinid herpesvirus 3 (CyHV-3) in Lake Biwa, Japan, was investigated. CyHV-3 was distributed all over the lake 5 years after the first outbreak. The mean concentration of CyHV-3 in water showed annual oscillation, with a peak in the summer and a trough in winter. Our results suggested that CyHV-3 is present at high density in reductive environments, such as reed zones and turbid or eutrophic water

Relationships between concentration of environmental DNA (eDNA) from common carp and water temperature in Iba-naiko lagoon.

<p>The regression line showed a significant trend by GLM (<i>p</i><0.05, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035868#s3" target="_blank">Results</a>).</p

Relationships between the concentration of environmental DNA (eDNA) from common carp and their biomass in the outdoor pond experiment.

<p>The eDNA in the water samples was concentrated using (a) 3.0-µm and (b) 0.8-µm pore-sized filters. The regression line for both filter types showed that there was a positive relationship between eDNA concentration and carp biomass per 1-L water (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035868#s3" target="_blank">Results</a>). Dotted lines represent the lower or upper limits of the 95% confidence intervals for the slope of the regression. The open and closed circles represent data from ponds A and B, respectively.</p

Relationships between the concentration of environmental DNA (eDNA) of common carp and three factors (duration, water temperature, and biomass) in aquarium experiments.

<p>(a) Time-dependent change in eDNA concentration at two biomass levels (one or three fish per tank). The error bars represent ±1 SD. (b) Effect of temperature on eDNA concentrations 6 d after introduction of fish to the tank. “<i>n.s.</i>" indicates no significant differences. The error bars represent ±1 SD. (c) Relationship between eDNA concentration and carp biomass per 1-L water 6 d after introduction of fish to the tank. The regression was significant (<i>p</i><0.05). Dotted lines represent the lower or upper limits of the 95% confidence intervals for the slope of the regression.</p