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Introduction
This web-based tool allows users to calculate and visualise the Changes in Phytoplankton and Zooplankton Communities (PH1/FW5) indicator, which is used to assess the state of pelagic habitats for OSPAR, UK Marine Strategy (UKMS) and Marine Strategy Framework Directive (MSFD). For information on how the PH1/FW5 indicator is calculated, refer to: https://www.ospar.org/documents?v=39001.
This indicator evaluates covariance in the abundance of plankton functional groups or “lifeforms” through time. The lifeforms in each pair are considered to be ecologically linked in some way and their co-variance through time reveals information about changes in the pelagic environment. Indicators based on functional groups have been proven relevant for the description of the community’s structure and biodiversity and are more easily inter-compared than other indicators based on taxonomy.
The app contains all plankton abundance datasets submitted to support the OSPAR Quality Status Report 2023 assessment of Pelagic Habitats. It contains both zooplankton and microphytoplankton abundance data from 9 countries that are part of the OSPAR Convention, also known as “OSPAR contracting parties”. These taxon abundance datasets have been aggregated into plankton lifeform abundance via the Plankton Lifeform Extraction Tool (PLET: https://www.dassh.ac.uk/lifeforms/) and extracted spatially as monthly mean values grouped by their intersection with spatial assessment units (polygons). The OSPAR assessment currently uses the COMP4 assessment units and the Water Framework Directive uses the WFD assessment units. Both options are available in this tool. Datasets for fixed-point stations are represented as individual points.
Instructions
To use the tool, users must first select a plankton abundance dataset from the Select dataset drop-down menu. Datasets are organised by OSPAR contracting party in alphabetical order (BE: Belgium, DE: Germany, DK: Denmark, ES: Spain, FR: France, NL: Netherlands, PT: Portugal, SE: Sweden, UK: United Kingdom).
Once a dataset has been selected, the user must select a relevant lifeform pair from the Select lifeform pairdrop-down menu. This list contains all the lifeform pairs that exist in the selected dataset.
Once the lifeform pair is selected, the user can either select an assessment unit (spatial polygon or point, dependent on dataset type) from the Select assessment unit drop-down menu, or by clicking a polygon or point in either of the two map panels.
Once an assessment unit is selected, abundance time-series for the two lifeforms are rendered and Kendall statistics are calculated for the full time-series, indicating the direction of change over time, with negative numbers indicating decrease and positive indicating increase. This information is displayed above each time-series plot, along with Sen’s slope estimate, describing the mean rate of change over time only for cases when the Kendall statistic is significant (i.e. p<0.05). The distribution of samples through time is also displayed as a separate plot below the two abundance time-series.
The length of the time-series assessed can be modified by adjusting the bounds of the slider labelled Year range for calculating time-series trend.
The shaded periods on each time-series indicate the assessment period used to calculate the plankton index (PI) envelope (blue shading) and the comparison period (pink shading). Both periods can be changed by adjusting the Plankton Index assessment period (envelope) and the Plankton Index comparison period (points) sliders.
Monthly abundance values from the assessment period (blue) are used to derive a 95% confidence polygon or “envelope” representing the mean annual cycle of covariance between the two lifeforms. Data from the comparison period (pink) are overlaid on top of this envelope to visualise how they differ from the assessment period.
Diagnostic information below the map panels indicates the confidence in the plankton index (PI) calculation. In some cases, the PI cannot be calculated due to insufficient data or overlap between the comparison and assessment periods. When this occurs, diagnostic messages inform why the indicator cannot be calculated. In other circumstances, the PI can be calculated, but only with low confidence due to issues revealed to the user in the diagnostic text.
Finally, COMP4 and WFD layers can be switched on or off using the layers tab in the top right of each map pane.
