The ensemble algorithm for estimation of model parameters in the problem of assessing greenhouse gases fluxes

The problem of assessing the greenhouse gases fluxes from the Earth’s surface based on observations is currently very urgent. To solve it, it is customary to use data assimilation systems (or a more general concept — inverse modeling), which include the observations on the concentration of greenhouse gases and models of the transport and diffusion. Since such problems involve large volumes of satellite data and the global model of transport and diffusion, it has a huge dimension. For this reason, the development of effective algorithms to enable the practical implementation of the task is required. The paper discusses data assimilation algorithms based on the ensemble Kalman filter and ensemble Kalman smoothing, which can be used to solve the problem of estimating greenhouse gases fluxes. Economical algorithms for estimating a parameter that is constant over a given time interval are proposed.

Short-lived detection of an introduced vertebrate eDNA signal in a nearshore rocky reef environment

Environmental DNA (eDNA) is increasingly used to measure biodiversity of marine ecosystems, yet key aspects of the temporal dynamics of eDNA remain unknown. Of particular interest is in situ persistence of eDNA signals in dynamic marine environments, as eDNA degradation rates have predominantly been quantified through mesocosm studies. To determine in situ eDNA residence times, we introduced an eDNA signal from a non-native fish into a protected bay of a Southern California rocky reef ecosystem, and then measured changes in both introduced and background eDNA signals across a fixed transect over 96 hours. Foreign eDNA signal was no longer detected only 7.5 hours after introduction, a time substantially shorter than the multi-day persistence times in laboratory studies. Moreover, the foreign eDNA signal spread along the entire 38 m transect within 1.5 hours after introduction, indicating that transport and diffusion play a role in eDNA detectability even in protected low energy marine environments. Similarly, native vertebrate eDNA signals varied greatly over the 96 hours of observation as well as within two additional nearby fixed transects sampled over 120 hours. While community structure did significantly change across time of day and tidal direction, neither accounted for the majority of observed variation. Combined, results show that both foreign and native eDNA signatures can exhibit substantial temporal heterogeneity, even on hourly time scales. Further work exploring eDNA decay from lagrangian perspective and quantifying effects of sample and technical replication are needed to better understand temporal variation of eDNA signatures in nearshore marine environments.