The Use of an Index of Biotic Integrity to Assess Phytoplankton Habitat Conditions in Chesapeake Bay

Richard V. Lacouture

Morgan State University Estuarine Research Center

The Phytoplankton Index of Biotic Integrity

• The PIBI is a set of metrics (12) established for specific assemblage of organisms which describes habitat conditions for that assemblage

• Reference and degraded habitat conditions were classified (DIN, PO4, light)

• Metrics were selected based upon their power to discriminate (Kruskal-Wallis Chi-squared and Wilcoxon tests) the correct habitat conditions

• Scoring criteria were established from metric thresholds based on the distribution of each metric in the reference community

• A scoring system of 1-3-5 is used for all metrics such that a score of 1 reflects impaired conditions and a score of 5 indicates conditions within the ‘desirable’ half (50%) of the reference distribution

• The scores are totaled and averaged for a specific site and season • The PIBI was validated by applying it to an independent data set

Parameters Selected for PIBI - Spring

METRIC TF OH MH PH

C:Chl Ratio X X X X

Surface Chlorophyll a X X X X

% Cryptophyte Biomass X

Cyanophyte Biomass X

Diatom Biomass X

Dinoflagellate Biomass X

DOC X X X X

Pheophytin X X X X

P. minimum Abundance X X

Total Biomass X X X X

Parameters Selected for PIBI - Summer

METRIC TF OH MH PH

C:Chl Ratio X X

Surface Chlorophyll a X X X X

% Cryptophyte Biomass X

Cyanophyte Biomass X X

Diatom Biomass X X X

Dinoflagellate Biomass X X

DOC X X X X

M. aeruginosa Abundance X

Pheophytin X X X X

Picoplankton Abundance X X

Total Biomass X X

Meets Expectations

Establishing Metric Scoring Thresholds

Validation - Overall Classification Efficiencies

SPRING SUMMER

TF 70.0% TF 78.4%

OH 70.5% OH 75.5%

MH 78.1% MH 77.8%

PH 84.4% PH 79.8%

This was run on 2003 Monitoring data and 1998-2002 Pfiesteria Monitoring data

PHYTOPLANKTON IBI SPRING 2004-2006

BAD (1-1.8)

FAIR-BAD (>1.8-2.6)

FAIR (>2.6-3.4)

FAIR-GOOD (>3.4-4.2)

GOOD (>4.2-5)

PHYTOPLANKTON IBI SUMMER 2004-2006

BAD (1-1.8)

FAIR-BAD (>1.8-2.6)

FAIR (>2.6-3.4)

FAIR-GOOD (>3.4-4.2)

GOOD (>4.2-5)

Seasonal Kendall Linear Trend Analysis of Spring/Summer Mean PIBI Values 1985-2006

SUMMER

IMPROVING CONDITIONS

DEGRADING CONDITIONS

SPRING

IMPROVING CONDITIONS

DEGRADING CONDITIONS

SIGNIFICANT TREND = p < 0.05

SPRING MEAN P-IBI SCORES ET5.2 1985-2006

0

1

2

3

4

5

85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06

P-IB

I SCO

RE

MINIMUM RESTORATION GOAL

P-VALUE = 0.0001SLOPE = -0.0532

SUMMER MEAN P-IBI SCORES TF1.5 1985-2006

0

1

2

3

4

5

85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06

P-IB

I SCO

RE

MINIMUM RESTORATION GOAL

P-VALUE = 0.0055SLOPE = 0.0183

Incorporating the PIBI into an Overall Index of Bay Habitat Health (BHHI)

• 6 parameters have been selected for this BHHI - 3 water quality parameters – chlorophyll a, water clarity (secchi) and dissolved oxygen - 3 biotic parameters – PIBI, Benthic Index of Biotic Integrity and SAV coverage

• A goal for each parameter was established• A measure of percent attainment (temporally

and then areally weighted) of each parameter’s goal is used for the scoring system for the BHHI

Temporal Percent Attainment of PIBI Goal

Maryland Tributaries

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

19

85

19

86

19

87

19

88

19

89

19

90

19

91

19

92

19

93

19

94

19

95

19

96

19

97

19

98

19

99

20

00

20

01

20

02

20

03

20

04

20

05

20

06

% o

f P

IBI

Go

al

Upper Bay Choptank Patapsco Patuxent Potomac MidBay

Areally Weighted Percent Attainment of PIBI Goal

Chesapeake Bay Phytoplankton Index of Biotic Integrity by Salinity Regime

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

Are

a W

eig

hte

d P

IBI>

=3

MH\PH TF\OH

Bay Health Index

2002 data

Reporting Regions Chl-a DO Clarity WQI P-IBI B-IBI SAV BI BHI

Patapsco 0 51 0 17 0 27 2 10 13

Elizabeth 38 42 9 30 33 29 NGZ 31 30

York 25 65 5 31 11 60 34 35 33

South West tribs 46 54 0 33 NA 27 39 33 33

Patuxent 39 90 7 45 18 36 17 24 35

James 59 100 14 58 17 50 21 29 44

SE (Tangier) 49 93 7 49 NA 48 43 45 47

Potomac 58 82 30 57 41 28 47 39 48

Rappahannock 30 81 11 41 56 52 70 59 50

Mid Bay 63 73 45 61 86 22 28 46 53

North East tribs 50 81 44 58 NA 67 35 51 54

North West tribs 63 98 29 63 NA 68 29 49 56

N Bay 53 86 30 56 39 68 66 57 57

Choptank 70 83 49 67 18 60 69 49 58

S Bay 30 93 46 56 94 75 60 76 66