Phytoplankton community analysis in the Northern Adriatic | Emodnet Biology

Phytoplankton community analysis in the Northern Adriatic

Introduction

This data product discloses the data collected in the framework of the LTER (Long Term Ecological Research) site in the northern Adriatic, close to Trieste. A time series has been built of observations on the species composition of the plankton.

Data series

The plankton series from the LTER site in the Northern Adriatic comprises three datasets in EMODnet biology: phytoplankton, microzooplankton and mesozooplankton. The phytoplankton series was started in 1986 and is continued until present. Results of the microzooplankton series and mesozooplankton series are available between 1998 and 2005. However, due to taxonomic problems, these two zooplanktondatasets are currently not used. Also for the phytoplankton, uncertainty and changes over time in the identification at species level has led to the decision to present species grouped into genera as the lowest taxonomic level.

The phytoplankton dataset "Phytoplankton North Adriatic-Gulf of Trieste LTER time-series" can be retrieved from EMODNET biology: http://emodnet-biology.eu/data-catalog?module=dataset&dasid=4462.

Downloads are possible through the data portal toolbox: http://www.emodnet-biology.eu/toolbox/en/download/occurrence/dataset/4462

The phytoplankton series is described in Cabrini et al. (2012). We refer to this paper for all details concerning sampling and working up of samples.

Data  product

We show the evolution over time of depth-averaged abundance of major groups of species, as well as the most frequent genera in the dataset. A frequency limit has been set to those groups and genera that have at least 20 occurrences during the course of the time series. The major groups are defined at the Class level. In the major groups, all species belonging to the group have been summed, also including the rare species that are not shown as separate species in the product.

In the Yearly series (R shiny app: top plot in tab observations), we have averaged all data per year and present the results as box plots. When transformation is used (double square root transformation is offered), transformation has preceded the calculation of the box plots.

The Monthly series (R shiny app: bottom plot in tab observations), shows the average (over the years) monthly pattern of occurrence of the species or group. No distinction between several periods has been made.

The Multivariate representation of phytoplankton (R shiny app: tab Multiv), is based on a PCA of double square-root transformed genus abundances of the most frequent genera (the same genus set that is shown in the time series). We present a biplot of samples and genera, but we have grouped samples (and present centroids) in two different ways: per year and per season. This allows to show the long-term trend as a shift in yearly centroid (in red), and the seasonal fluctuation as variation between months (in blue). Both trends are at right angles in the biplot, suggesting little correlation between the seasonal and long-term fluctuations. The biplot further shows the scores of the genera as arrows from the origin. The genera selected and used to show yearly and monthly temporal variation, is/are highlighted in green in this graph. Upon selection of a new group or genus, this highlighting is dynamically adapted. Thus, the multivariate graph shows how the selected group or genus contributes to the temporal evolution of the community on long-term and seasonal scales.

R Shiny application:

More Information

References

M. Cabrini, D. Fornasaro, G. Cossarini, M. Lipizer, D. Virgilio. 2012. Phytoplankton temporal changes in a coastal northern Adriatic site during the last 25 years. Estuarine, Coastal and Shelf Science 115: 113-124. https://doi.org/10.1016/j.ecss.2012.07.007

Code and methodology

https://github.com/EMODnet/EMODnet-Biology-Phytoplankton-community-analy...

Authors

Product created by Peter M.J. Herman

 

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