Lake phytoplankton

Intercalibration – 40 shades of green?

Gary Free, Wayne Trodd, Deirdre Tierney, Ruth Little,

Caroline Plant, Bryan Kennedy, Caroline Wynne

Water Framework Directive Intercalibration Exercise Update, Marine Institute, Oranmore, Co. Galway, 13/10/11.

Overview of method used in IE to

assign phytoplankton status in lakes

Phytoplankton composition metric

Chlorophyll a

IE Lake Phytoplankton Index

Normalised

Normalised

Averaged

Chlorophyll a

A traditional and long established parameter used to

determine biological response to nutrient enrichment

•SAKAMOTO, M., 1966: Primary production by phytoplankton

community in some Japanese lakes and its dependence on

lake depth. Archiv fur Hydrobiologie, 62, 1-28.

•DILLON, P.J., RIGLER, F.H., 1974: The phosphorus -

chlorophyll relationship in lakes. Limnology and

Oceanography, 19, 767-773.

Plot of log mean total phosphorus concentrations against log

mean chlorophyll a concentrations found in the study lakes

between March 1996 and December 1997. Regression: log y =

0.15 + 0.62 log x; r2 = 0.58; P < 0.01.

Irvine, K., Allott, N., deEyto, E., Free, G., White, J., Caroni, R., Kennelly,

C., Keaney, J., Lennon, C., Kemp, A., Barry, E., Day, S., Mills, P., O' Riain,

G., Quirke, B., Twomey, H., Sweeney, P., 2001: Ecological assessment of

Irish lakes. Environmental Protection Agency, Wexford, 503pp

Phytoplankton composition metric

Chlorophyll a

IE Lake Phytoplankton Index

Normalised

Normalised

Averaged

Composition and abundance must

also be included in assessment of

phytoplankton

0.5 mm

Free, G., Little, R., Tierney,

D., Donnelly, K., Caroni, R.,

2006. A reference based

typology and ecological

assessment system for Irish

lakes. Preliminary

investigations. 266pp. EPA,

Wexford, Ireland. ISBN:1-

84095-215-6. www.epa.ie

Development of

composition metric for lake

phytoplankton

•The assessment system was developed for summer

phytoplankton based on quantitative samples.

•Summer was chosen as it is the period when the

excessive growth of phytoplankton most often occurs.

•Assessment is based on nine groups or genera of

indicator taxa, each of which is awarded a score

ranging from 1 to 0.1 based on abundance. Sample

chlorophyll a is also awarded a score ranging from 1 to

0.1.

Development of composition index

•Reference value for the composition metric was

taken from a set of lakes in reference status

confirmed by a palaeolimnological study of 34

candidate reference lakes.

•These lakes had similar assemblages from a

comparison of top and bottom core samples. The

average reference composition metric value for

these lakes was 0.9383.

•This was used as a denominator to generate an

EQR following guidance document 10 (Tool 3 page

53, REFCOND (2003)).

Taylor et al.,

2006

www.EPA.ie

Reference values

Scores applied to abundance:

R2 0.67

Performance of composition metric

Phytoplankton composition metric

Chlorophyll a

IE Lake Phytoplankton Index

Normalised

Normalised

Averaged

x3 years

mean and

confidence

Normalising EQR

Metric

value

20

0

G/M 11

SG/G 17

7

4

national EQR for the metric

1

0

0,8517/20

11/200,55

7/200,35

4/200,20

Normalised EQR for the metric

1

0

0,80

0,60

0,40

0,20

15 0,75(0,75-0,55)*(0,80-0,60)

(0,85-0,55)+0,60

0,73

M/D

SD/D

REF

Metric

value

20

0

G/M 11

SG/G 17

7

4

national EQR for the metric

1

0

0,8517/20

11/200,55

7/200,35

4/200,20

Normalised EQR for the metric

1

0

0,80

0,60

0,40

0,20

15 0,75(0,75-0,55)*(0,80-0,60)

(0,85-0,55)+0,60(0,75-0,55)*(0,80-0,60)

(0,85-0,55)+0,60

0,73

M/D

SD/D

REF

PreparedPrepared byby: : AAnnenne LycheLyche SolheimSolheim & JRC& JRC

Type Lake Characterisation

Altitude

m

Mean depth

m

Alkalinity

meq l-1

Colour mg l-1

PtCo

Residence

time

L-N1

Lowland, shallow, moderate

alkalinity, clear <200 3 - 15 0.2 - 1 < 30

L-N2a

Lowland, shallow, low

alkalinity, clear <200 3 - 15 < 0.2 < 30

L-N3a

Lowland, shallow, low

alkalinity, meso-humic <200 3 - 15 < 0.2 30 - 90

L-N8a

Lowland, shallow, moderate

alkalinity, meso-humic <200 3 - 15 0.2 - 1 30 - 90

L-CB1

Lowland, shallow calcareous

lakes < 200 3 - 15 > 1

1-10

L-CB2

Lowland, very shallow

calcareous lakes < 200 < 3 > 1

0.1-1

NGIG and CBGIG lake types

intercalibrated for eutrophication pressure

by Ireland.

Relationship between national final EQRs

(standardised to remove country effects) and total P.

a)SE, b)FI, c)NO, d)UK, e)IE for LN8A lake type

Results from

Geoff Phillips

19/9/2011

Annex2 Milestone 6 Relationship between phytoplankton EQR and mean growing

season total phosphorus (µg/l), regression relationship fitted to data where total

phosphorus <200µg/l, results from Geoff Phillips.

Common metric ‘translates’ a country’s

boundaries into units comparable with other

Member states

H/G Bias as Class Width

-0.14

0.17

0.02

0.21

-0.23

0.43

-0.23 -0.24

0.17

-0.30

-0.20

-0.10

0.00

0.10

0.20

0.30

0.40

0.50

UK

DE

EE

(ind

ex)

LV BE

NL

DK PL IR

Countries’ H/G and G/M boundaries

should be within 0.25 of a class width

Harmonised

boundaries

for LCB1

lakes

For most types IE was within the

band

Lake type HG Bias GM bias

L-N1 0.10 -0.08

L-N2a 0.33 0.19

L-N3a 0.21 -0.02

L-N8a 0.25 0.14

L-CB1 0.17 0.21

L-CB2 0.54 0.69

LCB2 - One of these lake

types is doing its own thing

2 v 21 µg l-1

chlorophyll a

Still looking good??

IE reference and boundary values for

chlorophyll a for intercalibrated types

0

3

6

9

12

Ch

loro

ph

yll a

µg

l-1

Lake Type

Good/Moderate

High/Good

Reference

How did IE set boundaries?

Selection of TP bands (- - -) based on the lowess smoothed relationship (──) between

Simpson’s diversity index and transformed (Log x+1) TP. Smoothed relationship of

chlorophyll a with transformed (Log x+1) TP is overlain (green line). Graph refers to lakes >

20 mg l-1 CaCO3 only, TP values were mostly measured in Spring.

Diversity starts to decrease,

therefore resulting in an

‘undesirable disturbance to the

balance of organisms’ which

corresponded to a TP

concentration of 25 mg l-1.

The increase in diversity between

10 and 25 mg l-1 TP may

correspond to normative

definitions of good status in that

the change in not an ‘undesirable’

one.

For marl lakes (part of the LCB types)

stricter standards may need to adopted

nationally

From page 221 of Free, G., Little, R., Tierney, D., Donnelly, K., Caroni, R., 2006. A

reference based typology and ecological assessment system for Irish lakes. Preliminary

investigations. 266pp. EPA, Wexford, Ireland. ISBN:1-84095-215-6. www.epa.ie

OTSUKI, A., WETZEL, R.G., 1972: Coprecipitation of

phosphate with carbonates in a marl lake. Limnology and

Oceanography, 17, 763-767.

Joint Nature Conservation Committee (2007) Second

Report by the UK under Article 17 on the implementation

of the Habitats Directive from January 2001 to December

2006. JNCC, Peterborough.

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 50 100 150 200

Median MRP mg l-1

Q v

alue

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 10 20 30 40 50 60

Median TP mg l-1

Mac

roph

yte

mult

imet

ric

.

Fig 1 and 2 Comparison of metric response to pressure (Molybdate Reactive

Phosphorus and TP) for the Irish EPA macroinvertebrate Q-Value system for rivers

(McGarrigle, 1998) and the macrophyte multimetric (> 20 mg l-1 CaCO3 alkalinity)

(Free et al., 2006). Logarithmic trend-lines fitted. Fig 3 ILPI and TP with smoothed

line fitted CBGIG dataset.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 20 40 60 80 100

IE L

ake

Ph

yto

pla

nkt

on

In

de

x

TP mg l-1

Most biological change takes place at

initial stage of eutrophication

Implications for IE and future role in

WFD

•Some additional work on boundaries in marl lakes

•Need to translate boundaries from IC types into

national types.

•Classification for phytoplankton in lakes should now

use both chlorophyll a and composition to classify the

BQE and not just one parameter.

•Phytoplankton will be used as part of a OOAO

assessment in assigning status.

•Confidence of assessment critical for status

assignment.

•TP standards

•Zebra mussels