blomqvist ver 2 bqi malmö 2015...model)building) mats)blomqvist,)malmö)6th)may)2015) slide10)...

Reducing uncertainty in assessment with the Benthic Quality Index

Examples from the Swedish west coast

Mats Blomqvist, Hafok Kjell Leonardsson, SLU Rutger Rosenberg, GU, Marine Monitoring Marina Magnusson, Marine Monitoring

Photo: Hans C Nilsson

BQI history •  Introduced 2004 (Rosenberg et al 2004) •  Legally binding WFD method 2008 (NFS 2008:1, HVMFS 2013:19)

•  Further developed 2009 (Leonardsson et al 2009) –  discuss uncertainty

•  Legally binding MSFD method 2012 (HVMFS 2012:18)

•  Species sensiGvity values improved 2015 (Leonardsson et al 2015) –  SGll lowest diversity a species is found (5th percenGle)

•  Richness instead of Hurlbert ES50 –  Based on

•  Tolerance or sensiGvity to disturbance •  Capability to coexist with other species

–  Uncertainty evaluated

Mats Blomqvist, Malmö 6th May 2015 Slide 2

Polyphysia crassa

SensiGvity value

(S0.05)

ProporGon of samples from disturbed areas

Species sensiGvity value


1411 staGons

Amphiura chiajei

SensiGvity value

(S0.05)

StraGfied: at least 20 disturbed and 20 undisturbed samples Not straGfied: at least 20 samples

Species sensiGvity value •  SensiGvity factor =

abundance weighted mean of sensiGvity values

•  Randomly select a sensiGvity value within the 95% conf int for each species in a sample

•  Calculate factor •  Repeat 1000 Gmes for

each sample •  Each dot is one sample

calculated one Gme


SensiGvity factor without uncertainty in S0.05

SensiGvity factor with

uncertainty in S

0.05

Absolute average error is 0.26 ± 0.22 or a CV of 1.8 ± 2.9 %

i.e. uncertainty in sensiGvity values has a very small influence on BQI!

Species sensiGvity value


Polyphysia crassa

SensiGvity value

(S0.05)

ProporGon of samples from disturbed areas

Upper error bar

Lower error bar

Species sensiGvity values -‐ conclusions

•  Uncertainty depends on – proporGon of samples from disturbed environments – number of samples

•  Low precision can reduce accuracy – exclude species from sensiGvity list if •  low value and high upper range error •  large lower error range


Read more Leonardsson et al: Marine Pollu3on Bulle3n 93 (2015) 94–102

Reducing spaGal variaGon


VerGcal subtypes: ≤ 20 m BalGc influence > 20 m AtlanGc water

From SGU 2010

Account for environmental variaGon

•  Subtypes: e.g. BQI today •  Include environmental variables in the index by sefng

reference values for index metric based on environmental variable, e.g. –  Danish DKIv2 (reference values for AMBI and H’ as funcGon of salinity) (DKIv2 = ((1-‐ ((AMBI-‐AMBImin)/7))+ (H/Hmax))/2 * (1-‐(1/N)))

–  BriGsh IQIvIV (reference values for AMBI, Lambda’ and S as funcGon of salinity and sediment)

•  Regression model –  include relevant environmental factors salinity, sediment, depth –  assessment based on residuals


Model building – index components


855 staGons

StaGon medians

Model building


Model AIC ΔΑΙC

Y=BQI2015(depth) 3241.2 0

Y=BQI2009(depth) 3365.4 124.2

Y=BQI2015 (salinity) 3377.6 136.4

Y=BQI2009 (salinity) 3478.7 237.5

Y=BQI2015 (sediment) 4003.8 762.6

Y=BQI2009 (sediment) 4017.9 776.7

Assessment is based on the residuals from the regression model instead of the index value itself.

Model building


TransformaGon of residuals


Residuals per type


Assessment – GM •  SE approach 5 staGons

for spaGal representaGveness

•  Boundary GM 5% limit of baseline data –  Select assessment unit/year (AY)

–  Select 5 staGons in AY –  Select 1 sample from each staGon

–  Calculate mean


If mean residual is less than -‐2.52 then status is less than good

EQR = (mean residual + 8.53) / 17.06

Bootstrapped mean of 5 transformed residuals

Conclusions •  SpaGal variaGon in BQI is reduced by a regression model based on depth

•  Assessment is based on the residuals from the regression model instead of the index value itself

•  Bootstrapping is used to find GM boundary (5 samples within assessment unit/year)

•  Final step in assessment: compare mean residuals against status class boundaries


blomqvist ver 2 bqi malmö 2015...model)building) mats)blomqvist,)malmö)6th)may)2015) slide10)...

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