MIME regional assessment of status and trends in CB concentrations in sediment

Overview

The 2017 MIME assessment describes the trends and status of contaminant concentrations in biota and sediment at monitoring stations in the OSPAR area. Assessments are made for a large number of time series, each of a single contaminant in a single species (for biota) at a single monitoring station. This document is one of a series that synthesises the results of the individual time series to assess status and trends at the MIME regional level. In particular, it considers CB concentrations in sediment, where the CBs are CB28, CB52, CB101, CB118, CB138, CB153, CB180. For simplicity, the term ‘region’ is used throughout to describe MIME regions. OSPAR regions are always referred to as such.

The following sections:

  • summarise the individual time series results
  • describe the methods used to combine the individual time series results to estimate regional trends and status
  • present the estimates of regional trends
  • present the estimates of regional status


Summary of individual time series results

A time series of CB concentrations is assessed for status if:

  • there is at least one year with data in the period 2010 to 2015
  • there are at least three years of data over the whole time series
  • a parametric model can be fitted to the data and used to estimate the mean concentration in the final monitoring year (or, occasionally, if a non-parametric test of status is applied)

The conditions are more stringent for trends. Specifically, a time series is assessed for trends if:

  • there is at least one year with data in the period 2010 to 2015
  • there are at least five years of data over the whole time series
  • a parametric model can be fitted to the data and used to estimate the trend in mean concentrations

Note that all trend assessments for individual time series and most status assessments are based on the fit of a parametric model. This is important because only the parametric results are passed into the regional assessments in the following sections. Only 119 of 1016 CB time series were assessed for status using a non-parametric test.

The first tab below shows all the monitoring stations where there are individual time series assessments of trend or status for CBs. The magenta circles are stations where there is a trend assessment for at least one CB, and the cyan cirles are stations where there are only status assessments.

The next set of tabs show the trend and status assessments for each CB in turn. The colours have the following meaning:

  • blue: the mean concentration is significantly (p < 0.05) below the Background Assessment Concentration (BAC)
  • green: the mean concentration is significantly (p < 0.05) below the Environmental Assessment Criterion (EAC)
  • red: the mean concentration is not signficantly below the Environmental Assessment Criterion (EAC)

And the shapes have the following meaning:

  • downward triangle: the mean concentration is significantly decreasing (p < 0.05)
  • circle: there is no significant change in mean concentration (p > 0.05)
  • upward triangle: the mean concentration 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 MiME and OSPAR region
  • the same information presented as proportions
  • the number of time series with blue, green, or red status in each MIME and OSPAR region
  • the same information presented as proportions

Note that there are no BACs for the Gulf of Cadiz and the Iberian Sea. Time series in these regions are only assessed against the EAC, so can only be coloured green and red.


Stations


CB28


CB52


CB101


CB118


CB138


CB153


CB180


Trend summary (numbers)

Number of time series with upwards, downwards or no trend by MIME and OSPAR region

OSPAR region MIME region status CB28 CB52 CB101 CB118 CB138 CB153 CB180 total
2 Northern North Sea upward trend 2 1 1 1 1 1 1 8
no trend 2 2 7 8 7 13 6 45
downward trend 1 5 4 3 3 1 1 18
Southern North Sea upward trend 0 0 1 0 0 0 0 1
no trend 20 16 21 17 14 21 17 126
downward trend 9 6 10 14 18 10 10 77
Channel upward trend 0 0 0 0 0 0 0 0
no trend 0 0 1 1 0 1 1 4
downward trend 0 0 1 1 2 1 0 5
total upward trend 2 1 2 1 1 1 1 9
no trend 22 18 29 26 21 35 24 175
downward trend 10 11 15 18 23 12 11 100
3 Irish and Scottish West Coast upward trend 0 0 0 1 0 1 1 3
no trend 2 2 2 4 5 4 2 21
downward trend 0 2 3 1 1 1 0 8
Irish Sea upward trend 2 1 1 1 1 2 2 10
no trend 6 6 7 9 7 9 5 49
downward trend 3 4 4 2 4 1 3 21
Celtic Sea upward trend 0 0 0 0 0 0 0 0
no trend 0 1 0 0 0 0 0 1
downward trend 1 0 1 1 1 1 1 6
total upward trend 2 1 1 2 1 3 3 13
no trend 8 9 9 13 12 13 7 71
downward trend 4 6 8 4 6 3 4 35
4 Iberian Sea upward trend 0 4 0 0 0 0 0 4
no trend 13 10 15 15 15 15 15 98
downward trend 0 0 0 0 0 0 0 0
Gulf of Cadiz upward trend 0 0 0 1 0 0 0 1
no trend 6 7 5 5 9 12 8 52
downward trend 0 5 0 0 0 0 0 5
total upward trend 0 4 0 1 0 0 0 5
no trend 19 17 20 20 24 27 23 150
downward trend 0 5 0 0 0 0 0 5


Trend summary (proportions)

Proportion of time series with upwards, downwards or no trend by MIME and OSPAR region

OSPAR region MIME region status CB28 CB52 CB101 CB118 CB138 CB153 CB180 total
2 Northern North Sea upward trend 40 13 9 8 9 7 13 11
no trend 40 25 58 67 64 86 75 64
downward trend 20 62 33 25 27 7 12 25
Southern North Sea upward trend 0 0 3 0 0 0 0 0
no trend 69 73 66 55 44 68 63 62
downward trend 31 27 31 45 56 32 37 38
Channel upward trend 0 0 0 0 0 0
no trend 50 50 0 50 100 44
downward trend 50 50 100 50 0 56
total upward trend 6 3 4 2 2 2 3 3
no trend 65 60 63 58 47 73 67 62
downward trend 29 37 33 40 51 25 30 35
3 Irish and Scottish West Coast upward trend 0 0 0 16 0 16 33 9
no trend 100 50 40 67 83 67 67 66
downward trend 0 50 60 17 17 17 0 25
Irish Sea upward trend 18 9 9 8 9 17 20 13
no trend 55 55 58 75 58 75 50 61
downward trend 27 36 33 17 33 8 30 26
Celtic Sea upward trend 0 0 0 0 0 0 0 0
no trend 0 100 0 0 0 0 0 14
downward trend 100 0 100 100 100 100 100 86
total upward trend 14 6 6 11 5 16 21 11
no trend 57 56 50 68 63 68 50 60
downward trend 29 38 44 21 32 16 29 29
4 Iberian Sea upward trend 0 29 0 0 0 0 0 4
no trend 100 71 100 100 100 100 100 96
downward trend 0 0 0 0 0 0 0 0
Gulf of Cadiz upward trend 0 0 0 17 0 0 0 2
no trend 100 58 100 83 100 100 100 90
downward trend 0 42 0 0 0 0 0 8
total upward trend 0 15 0 5 0 0 0 3
no trend 100 66 100 95 100 100 100 94
downward trend 0 19 0 0 0 0 0 3


Status summary (numbers)

Number of time series with each status by MIME and OSPAR region

OSPAR region MIME region status CB28 CB52 CB101 CB118 CB138 CB153 CB180 total
2 Northern North Sea blue 7 0 0 3 4 5 5 24
green 12 22 21 8 19 18 18 118
red 1 1 2 12 0 0 0 16
Southern North Sea blue 0 1 0 1 1 0 0 3
green 37 33 37 11 39 42 42 241
red 6 5 6 31 3 1 1 53
Channel blue 0 0 0 0 0 0 0 0
green 2 5 8 1 3 34 23 76
red 10 12 19 31 0 0 0 72
total blue 7 1 0 4 5 5 5 27
green 51 60 66 20 61 94 83 435
red 17 18 27 74 3 1 1 141
3 Irish and Scottish West Coast blue 4 1 1 1 0 0 1 8
green 6 8 9 5 9 10 9 56
red 0 0 0 4 1 0 0 5
Irish Sea blue 2 0 0 1 0 0 1 4
green 15 19 18 4 19 19 18 112
red 3 0 1 15 1 0 0 20
Celtic Sea blue 0 0 0 0 0 0 0 0
green 1 1 1 0 1 1 1 6
red 0 0 0 1 0 0 0 1
total blue 6 1 1 2 0 0 2 12
green 22 28 28 9 29 30 28 174
red 3 0 1 20 2 0 0 26
4 Iberian Sea blue 0 0 0 0 0 0 0 0
green 14 14 9 0 9 15 11 72
red 1 1 6 15 6 0 4 33
Gulf of Cadiz blue 0 0 0 0 0 0 0 0
green 12 12 12 11 14 14 14 89
red 1 1 2 3 0 0 0 7
total blue 0 0 0 0 0 0 0 0
green 26 26 21 11 23 29 25 161
red 2 2 8 18 6 0 4 40


Status summary (proportions)

Proportion of time series with each status by MIME and OSPAR region

OSPAR region MIME region status CB28 CB52 CB101 CB118 CB138 CB153 CB180 total
2 Northern North Sea blue 35 0 0 13 17 22 22 15
green 60 96 91 35 83 78 78 75
red 5 4 9 52 0 0 0 10
Southern North Sea blue 0 2 0 2 2 0 0 1
green 86 85 86 26 91 98 98 81
red 14 13 14 72 7 2 2 18
Channel blue 0 0 0 0 0 0 0 0
green 17 29 30 3 100 100 100 51
red 83 71 70 97 0 0 0 49
total blue 9 1 0 4 7 5 6 5
green 68 76 71 20 89 94 93 72
red 23 23 29 76 4 1 1 23
3 Irish and Scottish West Coast blue 40 11 10 10 0 0 10 12
green 60 89 90 50 90 100 90 81
red 0 0 0 40 10 0 0 7
Irish Sea blue 10 0 0 5 0 0 5 3
green 75 100 95 20 95 100 95 82
red 15 0 5 75 5 0 0 15
Celtic Sea blue 0 0 0 0 0 0 0 0
green 100 100 100 0 100 100 100 86
red 0 0 0 100 0 0 0 14
total blue 19 3 3 6 0 0 7 6
green 71 97 94 29 94 100 93 82
red 10 0 3 65 6 0 0 12
4 Iberian Sea blue 0 0 0 0 0 0 0 0
green 93 93 60 0 60 100 73 69
red 7 7 40 100 40 0 27 31
Gulf of Cadiz blue 0 0 0 0 0 0 0 0
green 92 92 86 79 100 100 100 93
red 8 8 14 21 0 0 0 7
total blue 0 0 0 0 0 0 0 0
green 93 93 72 38 79 100 86 80
red 7 7 28 62 21 0 14 20


MIME 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.

Trends

For a regional trend assessment, the trend in each time series is summarised by the estimated change in log concentration over the last twenty years (or shorter if the time series doesn’t extend that far back). Regional trends are then estimated by fitting the following linear mixed model by restricted maximum likelihood:

  • response: trend (yearly change in log concentration)
  • fixed model: region
  • random model: CB + region.CB + station + trend estimation variation + residual variation

The fixed model means that a trend is estimated for each region. Trends in the different CBs are assumed to be broadly similar, because inputs and control measures are likely to affect all CBs in a similar way. Each regional trend can thus be interpreted as the common trend in CB concentrations in that region (i.e. the trend averaged across all CBs).

The random model has five terms:

  • CB allows for variation in trend between CBs common to all regions
  • region.CB allows for additional variation in trend between CBs within regions
  • station allows for variation in trend between stations common to all CBs
  • trend estimation variation is the variance of the trend 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

The meta-analysis is restricted to time series from monitoring stations that are classified as ‘representative’. ‘Baseline’ stations (those with near pristine conditions or only subject to very diffuse inputs) are omitted because any trends there will likely be caused by different processes to those at representative stations. Similarly ‘impacted’ stations (those close to a point source) are omitted because trends there will likely reflect changes due to the point source, and will be ‘unrepresentative’ at the regional level.

The meta-analysis is further restricted to:

  • regions with at least three trend stations with good geographic spread. Three stations is considered the minimum required to provide some sort of evidence base at the regional level
  • CBs with trend information for at least three stations (over all regions): CBs are treated as random effects in the meta-anlaysis, so information about trends in one CB can be ‘borrowed’ from the trend information in the other CBs

Status

For a regional status assessment, the status of each time series is summarised by the difference between the estimated mean log concentration in the final monitoring year and the log assessment concentration. This ensures that status is always measured on the same scale, even though the assessment criterion might vary between CBs and time series. Essentially the same linear mixed model as for trends is then fitted:

  • response: status (mean log concentration - log assessment concentration)
  • fixed model: region
  • random model: CB + region.CB + station + status estimation variation + residual variation

where status estimation variation is the variation in the status estimates from the individual time series analysis, assumed known and fixed.

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. However, the few time series with a non-parametric assessment of status must be excluded, because there is no summary measure of status to use in the mixed model.

Again, the meta-analysis is restricted to regions with at least three status stations with good geographic spread and to CBs with status information for at least three stations (over all regions).

Presentation

The results of both the trend and status regional assessments are back-transformed for presentation. The estimated regional trend is then interpreted as the percentage yearly change in concentration and the estimated regional status as the ratio of the mean regional concentration to the assessment concentration. To illustrate the latter, a value of 1 indicates that the mean regional concentration is equal to the assessment concentration; a value of 0.5 indicates that it is half the assessment concentration, and a value of 2 indicates that it is twice the assessment concentration.


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 tabs show the stations with parametric trend and status assessments for each OSPAR region in turn, having excluded trend assessments at baseline and impacted stations. The magenta circles are stations where there is a trend assessment for at least one CB, and the cyan cirles are stations where there are only status assessments.

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

  • trend: Celtic Sea, Channel
  • status: Celtic Sea, Iberian Sea


OSPAR region 1


OSPAR region 2


OSPAR region 3


OSPAR region 4


Regional trends

The first 4 tabs show:

  • Regional trends: estimates of the regional trend (averaged over CBs) with pointwise 95% confidence limits
  • Regional trends by CB: regional trend estimates for each CB with pointwise 95% confidence limits plotted by CB
  • Regional trends by region: regional trend estimates for each CB with pointwise 95% confidence limits plotted by biogeographic region
  • Individual time series: the trend estimates from the individual time series on which the regional assessment is based. The estimates from regions with insufficient geographic spread (and excluded from the meta-analysis) are also shown.
  • The symbols in all these plots have the following interpretation:

    • downward triangle: the mean concentration is significantly decreasing (p < 0.05)
    • circle: there is no change in mean concentration (p > 0.05)
    • upward triangle: the mean concentration is significantly increasing (p < 0.05)

    The final 2 tabs show the estimates of the regional trend (averaged over CBs) and the regional trend by CB.


    Regional trends


    Regional trends by CB


    Regional trends by region


    Individual time series


    Estimates by region

    This table shows the estimates of the regional trend:

    • trend: the estimated mean yearly change in log concentration across the region (multiplied by 100 for presentation)
    • se: the corresponding standard error
    • lower, upper: the corresponding pointwise 95% confidence limits
    • % yearly change: the estimated mean % yearly change in concentration across the region
    • %yc lower, %yc upper: the corresponding pointwise 95% confidence limits


    MIME region trend se lower upper % yearly change %yc lower %yc upper
    Northern North Sea -5.01 1.52 -7.99 -2.03 -4.89 -7.68 -2.01
    Southern North Sea -2.44 1.02 -4.45 -0.44 -2.41 -4.35 -0.44
    Irish and Scottish West Coast -3.25 2.29 -7.74 1.23 -3.20 -7.44 1.24
    Irish Sea -2.41 1.80 -5.94 1.12 -2.38 -5.77 1.13
    Gulf of Cadiz -9.66 2.68 -14.90 -4.41 -9.21 -13.84 -4.32


    Estimates by region and CB

    This table shows the estimates of the regional trend by determinand:

    • trend: the estimated mean yearly change in log concentration across the region (multiplied by 100 for presentation)
    • se: the corresponding standard error
    • lower, upper: the corresponding pointwise 95% confidence limits
    • % yearly change: the estimated mean % yearly change in concentration across the region
    • %yc lower, %yc upper: the corresponding pointwise 95% confidence limits


    MIME region CB trend se lower upper % yearly change %yc lower %yc upper
    Northern North Sea CB28 -3.35 1.72 -6.73 0.02 -3.30 -6.51 0.02
    CB52 -8.20 1.68 -11.49 -4.92 -7.88 -10.86 -4.80
    CB101 -6.57 1.60 -9.70 -3.43 -6.35 -9.24 -3.38
    CB118 -4.85 1.60 -7.98 -1.71 -4.73 -7.67 -1.70
    CB138 -5.45 1.62 -8.62 -2.27 -5.30 -8.26 -2.25
    CB153 -2.79 1.56 -5.84 0.26 -2.75 -5.67 0.26
    CB180 -3.86 1.68 -7.15 -0.57 -3.79 -6.90 -0.57
    Southern North Sea CB28 -2.78 0.96 -4.67 -0.90 -2.74 -4.56 -0.90
    CB52 -2.26 0.99 -4.19 -0.32 -2.23 -4.10 -0.32
    CB101 -1.91 0.94 -3.76 -0.06 -1.89 -3.69 -0.06
    CB118 -2.36 0.94 -4.20 -0.53 -2.33 -4.11 -0.52
    CB138 -3.27 0.93 -5.10 -1.44 -3.22 -4.97 -1.43
    CB153 -1.86 0.94 -3.69 -0.02 -1.84 -3.63 -0.02
    CB180 -2.67 0.97 -4.56 -0.77 -2.63 -4.46 -0.77
    Irish and Scottish West Coast CB28 -2.93 2.51 -7.84 1.99 -2.88 -7.54 2.01
    CB52 -5.53 2.55 -10.53 -0.53 -5.38 -9.99 -0.53
    CB101 -5.16 2.54 -10.14 -0.18 -5.03 -9.65 -0.18
    CB118 -2.64 2.44 -7.43 2.14 -2.61 -7.16 2.17
    CB138 -3.67 2.44 -8.45 1.10 -3.61 -8.10 1.11
    CB153 -1.21 2.37 -5.86 3.45 -1.20 -5.69 3.51
    CB180 -1.64 2.58 -6.69 3.42 -1.62 -6.47 3.48
    Irish Sea CB28 -1.56 1.82 -5.13 2.02 -1.54 -5.00 2.04
    CB52 -4.59 1.89 -8.29 -0.88 -4.48 -7.95 -0.88
    CB101 -3.85 1.85 -7.48 -0.22 -3.78 -7.20 -0.22
    CB118 -1.84 1.82 -5.41 1.74 -1.82 -5.27 1.75
    CB138 -2.75 1.81 -6.31 0.80 -2.72 -6.12 0.81
    CB153 -0.71 1.82 -4.28 2.87 -0.70 -4.19 2.91
    CB180 -1.58 1.85 -5.20 2.04 -1.57 -5.07 2.06
    Gulf of Cadiz CB28 -8.54 2.95 -14.33 -2.76 -8.19 -13.35 -2.72
    CB52 -12.70 2.85 -18.29 -7.12 -11.93 -16.72 -6.87
    CB101 -10.37 3.01 -16.27 -4.47 -9.85 -15.02 -4.37
    CB118 -8.21 2.91 -13.91 -2.51 -7.88 -12.99 -2.48
    CB138 -9.70 2.94 -15.46 -3.94 -9.25 -14.33 -3.87
    CB153 -8.94 2.81 -14.44 -3.44 -8.55 -13.45 -3.38
    CB180 -9.12 2.96 -14.93 -3.32 -8.72 -13.87 -3.26


    Regional status compared to the Environmental Assessment Criterion (EAC)

    The first 4 tabs show:

  • Regional status: estimates of the regional status (averaged over CBs) with pointwise upper one-sided 95% confidence limits
  • Regional status by CB: regional status estimates for each CB with pointwise upper one-sided 95% confidence limits plotted by CB
  • Regional status by region: regional status estimates for each CB with pointwise upper one-sided 95% confidence limits plotted by biogeographic region
  • Individual time series: the status estimates from the individual time series on which the regional assessment is based. The estimates from 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 concentration is significantly (p < 0.05) below the Background Assessment Concentration (BAC)
    • green: the mean concentration is significantly (p < 0.05) below the EAC
    • red: the estimate of the mean concentration is not significantly below the EAC

    Note that to see why some points are coloured blue, it is necessary to look ahead to the next section, where status is compared to the BAC. Unfortunately, it isn’t easy to present the assessment of status relative to the EAC with the assessment of status relative to the BAC because the ratio of the BAC to the EAC can vary between CBs, between regions and, for biota, between species.

    The final 2 tabs show the estimates of the regional status (averaged over CBs) and the regional status by CB.


    Regional status


    Regional status by CB


    Regional status by region


    Individual time series


    Estimates by region

    This table shows the estimates of the regional status:

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


    MIME region status se upper concentration conc upper
    Northern North Sea -3.01 0.50 -2.19 0.05 0.11
    Southern North Sea -2.07 0.48 -1.28 0.13 0.28
    Channel -1.56 0.48 -0.77 0.21 0.46
    Irish and Scottish West Coast -3.48 0.55 -2.57 0.03 0.08
    Irish Sea -2.18 0.50 -1.36 0.11 0.26
    Gulf of Cadiz -3.27 0.52 -2.42 0.04 0.09


    Estimates by region and CB

    This table shows the estimates of regional status by determinand:

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


    MIME region CB status se upper concentration conc upper
    Northern North Sea CB28 -2.09 0.22 -1.73 0.12 0.18
    CB52 -2.78 0.21 -2.44 0.06 0.09
    CB101 -2.55 0.21 -2.21 0.08 0.11
    CB118 -1.02 0.21 -0.68 0.36 0.50
    CB138 -3.51 0.21 -3.17 0.03 0.04
    CB153 -4.83 0.20 -4.50 0.01 0.01
    CB180 -4.26 0.21 -3.92 0.01 0.02
    Southern North Sea CB28 -1.35 0.14 -1.11 0.26 0.33
    CB52 -2.15 0.15 -1.91 0.12 0.15
    CB101 -1.61 0.14 -1.38 0.20 0.25
    CB118 0.01 0.14 0.24 1.01 1.28
    CB138 -2.36 0.14 -2.13 0.09 0.12
    CB153 -3.60 0.14 -3.36 0.03 0.03
    CB180 -3.45 0.14 -3.21 0.03 0.04
    Channel CB28 -1.44 0.18 -1.14 0.24 0.32
    CB52 -1.69 0.18 -1.40 0.18 0.25
    CB101 -0.90 0.16 -0.63 0.41 0.53
    CB118 0.64 0.16 0.90 1.90 2.47
    CB138 -1.73 0.23 -1.35 0.18 0.26
    CB153 -3.03 0.16 -2.77 0.05 0.06
    CB180 -2.82 0.17 -2.54 0.06 0.08
    Irish and Scottish West Coast CB28 -3.00 0.33 -2.46 0.05 0.09
    CB52 -2.92 0.36 -2.32 0.05 0.10
    CB101 -3.26 0.34 -2.70 0.04 0.07
    CB118 -1.22 0.33 -0.68 0.29 0.51
    CB138 -3.96 0.32 -3.42 0.02 0.03
    CB153 -5.23 0.32 -4.70 0.01 0.01
    CB180 -4.78 0.35 -4.21 0.01 0.01
    Irish Sea CB28 -1.27 0.21 -0.92 0.28 0.40
    CB52 -2.25 0.21 -1.90 0.11 0.15
    CB101 -1.99 0.21 -1.64 0.14 0.19
    CB118 -0.05 0.21 0.30 0.96 1.35
    CB138 -2.44 0.21 -2.10 0.09 0.12
    CB153 -3.90 0.21 -3.55 0.02 0.03
    CB180 -3.38 0.21 -3.03 0.03 0.05
    Gulf of Cadiz CB28 -3.30 0.25 -2.88 0.04 0.06
    CB52 -3.96 0.27 -3.52 0.02 0.03
    CB101 -2.84 0.26 -2.42 0.06 0.09
    CB118 -1.20 0.25 -0.79 0.30 0.45
    CB138 -3.06 0.25 -2.65 0.05 0.07
    CB153 -4.71 0.26 -4.29 0.01 0.01
    CB180 -3.78 0.25 -3.37 0.02 0.03


    Regional status compared to the Background Assessment Concentration (BAC)

    The first 4 tabs show:

  • Regional status: estimates of the regional status (averaged over CBs) with pointwise upper one-sided 95% confidence limits
  • Regional status by CB: regional status estimates for each CB with pointwise upper one-sided 95% confidence limits plotted by CB
  • Regional status by region: regional status estimates for each CB with pointwise upper one-sided 95% confidence limits plotted by biogeographic region
  • Individual time series: the status estimates from the individual time series on which the regional assessment is based. The estimates from 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 concentration is significantly (p < 0.05) below the BAC
    • green: the mean concentration is significantly (p < 0.05) below the Environmental Assessment Criterion (EAC)
    • red: the estimate of the mean concentration is not significantly below the EAC

    The final 2 tabs show the estimates of the regional status (averaged over CBs) and the regional status by CB.


    Regional status


    Regional status by CB


    Regional status by region


    Individual time series


    Estimates by region

    This table shows the estimates of the regional status:

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


    MIME region status se upper concentration conc upper
    Northern North Sea 0.36 0.23 0.75 1.44 2.12
    Southern North Sea 1.30 0.18 1.60 3.67 4.97
    Channel 1.81 0.20 2.14 6.09 8.46
    Irish and Scottish West Coast -0.12 0.34 0.43 0.88 1.54
    Irish Sea 1.19 0.24 1.59 3.28 4.89
    Gulf of Cadiz


    Estimates by region and CB

    This table shows the estimates of regional status by determinand:

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


    MIME region CB status se upper concentration conc upper
    Northern North Sea CB28 -0.05 0.22 0.32 0.95 1.38
    CB52 0.33 0.21 0.68 1.39 1.97
    CB101 0.51 0.21 0.86 1.67 2.37
    CB118 0.25 0.21 0.60 1.28 1.82
    CB138 0.46 0.21 0.80 1.58 2.23
    CB153 0.53 0.21 0.87 1.69 2.39
    CB180 0.52 0.21 0.87 1.69 2.39
    Southern North Sea CB28 0.70 0.15 0.94 2.02 2.57
    CB52 0.98 0.15 1.22 2.66 3.40
    CB101 1.45 0.15 1.69 4.28 5.44
    CB118 1.28 0.14 1.51 3.59 4.55
    CB138 1.60 0.14 1.84 4.94 6.27
    CB153 1.75 0.14 1.99 5.76 7.31
    CB180 1.34 0.15 1.58 3.82 4.87
    Channel CB28 0.69 0.18 0.99 1.99 2.70
    CB52 1.46 0.18 1.75 4.30 5.77
    CB101 2.16 0.17 2.43 8.64 11.38
    CB118 1.90 0.16 2.17 6.71 8.77
    CB138 2.16 0.22 2.52 8.64 12.41
    CB153 2.31 0.16 2.58 10.11 13.21
    CB180 1.97 0.17 2.24 7.14 9.43
    Irish and Scottish West Coast CB28 -0.89 0.34 -0.34 0.41 0.71
    CB52 0.08 0.36 0.67 1.08 1.94
    CB101 -0.16 0.34 0.40 0.85 1.50
    CB118 0.02 0.34 0.58 1.02 1.78
    CB138 0.00 0.33 0.55 1.00 1.73
    CB153 0.11 0.33 0.66 1.12 1.93
    CB180 -0.03 0.35 0.54 0.97 1.72
    Irish Sea CB28 0.78 0.22 1.13 2.17 3.10
    CB52 0.88 0.22 1.24 2.42 3.47
    CB101 1.09 0.22 1.45 2.97 4.26
    CB118 1.22 0.22 1.57 3.38 4.82
    CB138 1.51 0.22 1.87 4.53 6.47
    CB153 1.45 0.22 1.81 4.26 6.09
    CB180 1.40 0.22 1.75 4.04 5.78
    Gulf of Cadiz CB28
    CB52
    CB101
    CB118
    CB138
    CB153
    CB180


    CB profiles

    The profile of concentrations across CBs can sometimes be useful for examining sources, and for comparing concentrations across regions where assessment criteria are not available. Profiles were examined by fitting the following linear mixed model by restricted maximum likelihood:

    • response: mean log concentration
    • fixed model: region
    • random model: CB + region.CB + station + estimation variation + residual variation

    where, for each time series, the mean log concentration is the estimated mean log concentration in the final monitoring year and the estimation variance is the variance associated with this estimate.

    The estimated CB concentration profiles by region are shown below with pointwise 95% confidence limits. The units are ug/kg dw.