Overview

The 2022 assessment of CSEMP contaminant and biological effects data includes an assessment of the status and trends of the prevalence of micronucleated cells (MNC) in fish at monitoring stations around the UK. Assessments are made for a large number of time series, each of micronucleated cell prevalence in a single species at a single monitoring station. This document synthesises the results of the individual time series to assess the status and trends of micronucleated cell prevalence at the biogeographic regional level.

The regional assessment only considers coastal and offshore stations and excludes estuarine stations. The results are therefore based on the monitoring data collected within the waters assessed under the UK Marine Strategy (MS). For simplicity, the term ‘region’ is used throughout to describe biogeographic regions. MS sub-regions are always referred to as such.

The following sections:


Summary of individual time series results

A time series of MNC prevalence is assessed for status if:

  • there is at least one year with data in the period 2016 to 2021
  • there are at least three years of data over the whole time series

A time series is also assessed for trends if:

  • there are at least five years of data over the whole time series

The first tab below shows all the monitoring stations where there are individual time series assessments of trend or status for MNC. The purple circles are stations where there is a trend assessment and the light blue cirles are stations where there is only a status assessment, The areas delineated by the thinner black lines are the biogeographic regions; those delineated by the thicker black lines are the MS sub-regions.

The next set of tabs show the trend and status assessments for MNC. The colours have the following meaning:

  • blue: the mean prevalence is significantly (p < 0.05) below the Background Assessment Criterion (BAC)
  • orange: the mean prevalence is not significantly below the BAC

And the shapes have the following meaning:

  • downward triangle: the mean prevalence is significantly decreasing (p < 0.05)
  • circle: there is no significant change in mean prevalence (p > 0.05) or there are too few years to test for trends
  • upward triangle: the mean prevalence is significantly increasing (p < 0.05)

The final set of tabs give:

  • the number of time series with upwards, downwards or no trend in each biogeographic region and MS sub-region
  • the same information presented as proportions
  • the number of time series with blue and orange status in each biogeographic region and MS sub-region
  • the same information presented as proportions


Stations


#### MNC


Trend summary (numbers)

Number of time series with upwards, downwards or no trend by biogeographic region and MS sub-region

MS sub-region biogeographic region status MNC
Celtic Seas Irish Sea upward trend 0
no trend 1
downward trend 1
W Channel & Celtic Sea upward trend 0
no trend 0
downward trend 2
total upward trend 0
no trend 1
downward trend 3


Trend summary (proportions)

Proportion of time series with upwards, downwards or no trend by biogeographic region and MS sub-region

MS sub-region biogeographic region status MNC
Celtic Seas Irish Sea upward trend 0
no trend 50
downward trend 50
W Channel & Celtic Sea upward trend 0
no trend 0
downward trend 100
total upward trend 0
no trend 25
downward trend 75


Status summary (numbers)

Number of time series with each status by biogeographic region and MS sub-region

MS sub-region biogeographic region status MNC
Greater North Sea Northern North Sea blue 2
orange 3
Southern North Sea blue 2
orange 5
E Channel blue 0
orange 2
total blue 4
orange 10
Celtic Seas Irish Sea blue 5
orange 3
W Channel & Celtic Sea blue 2
orange 1
total blue 7
orange 4


Status summary (proportions)

Proportion of time series with each status by biogeographic region and MS sub-region

MS sub-region biogeographic region status MNC
Greater North Sea Northern North Sea blue 40
orange 60
Southern North Sea blue 29
orange 71
E Channel blue 0
orange 100
total blue 29
orange 71
Celtic Seas Irish Sea blue 62
orange 38
W Channel & Celtic Sea blue 67
orange 33
total blue 64
orange 36


Regional assessment - methods

Tabulating the number of time series with each status category by region provides a quick summary of the individual time series results. However, it does not provide an objective regional assessment of status. Similarly, tabulating the number of time series with an upward or downward trend does not provide an objective regional assessment of trend. This section describes how the individual time series results can by synthesised in a meta-analysis to assess both status and trend at the regional level. In practice there are insufficient time series with trend information to do a regional trend assessment; only a regional status assessment is possible

Status

For a regional status assessment, the status of each time series is summarised by the difference between the estimated log mean prevalence in the final monitoring year and the log assessment criterion. This ensures that status is always measured on the same scale, even though the assessment criterion might vary between species. Regional status is then estimated by fitting the following linear mixed model by restricted maximum likelihood:

  • response: status (log mean prevalence - log assessment criterion)
  • fixed model: region
  • random model: status estimation variation + residual variation

The fixed model means that status is estimated for each region. The random model has two terms:

  • status estimation variation is the variance of the status estimates from the individual time series analysis, assumed known and fixed
  • residual variation is the variation that cannot be explained by any of the fixed effects or the other random effects

There are no restrictions on the time series used in the status meta-analysis based on the classification of the monitoring station; time series from baseline, representative and impacted stations are all included.

The meta-analysis is restricted to regions with at least three status stations with good geographic spread.

Presentation

The results of the regional status assessment are back-transformed for presentation. The estimated regional status is then interpreted as the ratio of the regional mean prevalence to the assessment criterion. To illustrate the latter, a value of 1 indicates that the regional mean prevalence is equal to the assessment criterion; a value of 0.5 indicates that it is half the assessment criterion, and a value of 2 indicates that it is twice the assessment criterion.


Regional assessment - availability of time series

This section provides more detail on the number and geographic spread of the time series available for the meta-analyses. The map shows the stations with trend and status assessments. The purple circles are stations where there is a trend assessment and the light blue cirles are stations where there is only a status assessment,

The following regions have an insufficient number or time series or spread of stations and are excluded from the regional assessment:

  • trend: Irish Sea, W Channel & Celtic Sea
  • status: E Channel



Regional status compared to the Background Assessment Criterion (BAC)

The first 2 tabs show:

  • Regional status: estimates of the regional status for MNC with pointwise upper one-sided 95% confidence intervals
  • Individual time series: the status estimates from the individual time series on which the regional assessment is based. The estimates for regions with insufficient geographic spread (and excluded from the meta-analysis) are also shown.

The symbols in all the plots have the following interpretation:

  • blue: the mean prevalence is significantly (p < 0.05) below the BAC
  • orange: the mean prevalence is not significantly below the BAC

The final tab shows the estimates of the regional status in MNC.


Regional status


Individual time series


Estimates by region

This table shows the estimates of the regional status:

  • status: the estimated mean log prevalence minus the log BAC
  • se: the corresponding standard error
  • upper: the corresponding pointwise upper one-sided 95% confidence limit
  • concentration: the estimated mean prevalence relative to the BAC
  • conc upper: the corresponding pointwise upper one-sided 95% confidence limit


biogeographic region status se upper concentration conc upper
Northern North Sea -0.60 0.24 -0.21 0.55 0.81
Southern North Sea -0.66 0.19 -0.35 0.52 0.71
Irish Sea -0.89 0.20 -0.56 0.41 0.57
W Channel & Celtic Sea -1.26 0.35 -0.69 0.28 0.50