OSPAR CEMP Guideline. Common indicator: PH1/FW5 Change in plankton communities

Abstract

Indicators based on plankton lifeforms have been used to assess community response to sewage pollution (Charvet et al. 1998; Tett et al. 2008), anoxia (Rakocinski 2012), fishing (Bremner et al. 2004), eutrophication (HELCOM 2012), climate change (Beaugrand 2005; Bedford et al. 2020; McQuatters-Gollop et al. 2019), and ocean acidification (Keys et al. 2018). 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 (Estrada et al. 2004; Gallego et al. 2012; Garmendia et al. 2012; Mouillot et al. 2006). In practice, it is often preferable to aggregate species with similar traits into functional groups, such as lifeforms, rather than assessing the dynamics of individual species. Measures of species abundance are frequently subject to large interannual and regional variation, often due to natural physical dynamics and habitat preferences rather than anthropogenic stressors (de Jonge 2007). Functional group abundance is often less variable because variability in the abundances of the group’s constituent species averages out. Cryptic speciation (species with near-identical appearance) within the plankton community, alongside the limitations of identifying plankton using routine light microscopy techniques, make it difficult to generate accurate counts at a species or genus level. Functional group abundance is more reliable as many plankton lifeforms are easily identified, making comparisons between different laboratories and institutes feasible. Both abundance and biomass data can be used to inform lifeform time-series, depending on the lifeform in question and data availability from monitoring programmes.