recovery of a hypereutrophic urban lake (onondaga lake, ny): implications for monitoring water...

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Daniele Baker Master's Capstone November 15, 2013 Abstract: A 23-year record of limnological parameters for Onondaga Lake was used to evaluate changes during recovery from eutrophication. I (1) compared phytoplankton responses to total phosphorus (TP) in ecologically defined seasonal periods with those in a calendar date defined annual period, (2) ascertained whether chlorophyll-a (Chl-a) concentration was a good proxy for phytoplankton biomass, and (3) assessed whether the phytoplankton assemblage was altered in response to the environmental remediation. Seasonal variations in the relationships between Chl-a and biomass to TP were common. Irregular temporal patterns in Chl-a per unit biomass were due to a shift from Chl-a deficient to Chl-a rich phytoplankton, not changes in light regime. The phytoplankton assemblage varied mostly as a function of changes in total nitrogen (TN), TP, and TN:TP ratios. Phytoplankton diversity did not increase, but phytoplankton bloom frequencies and cellular biovolumes decreased. Synurophyceae and Chrysophyceae, absent since the onset of eutrophication, reappeared in 1998.

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Recovery of a Hypereutrophic Urban Lake (Onondaga Lake, NY): Implications for Monitoring

Water Quality and Phytoplankton Ecology

Capstone Presentation By Daniele BakerM.S. Ecology, Dept. of EFB Advisors: Dr.’s Myron Mitchell and Kimberly Schulz

Publications relating to this presentation …

Baker, D.M. 2013. Recovery of a hypereutrophic urban lake (Onondaga Lake, NY): Implications for monitoring water quality and phytoplankton ecology. Master’s thesis. SUNY, College of Environmental Science and Forestry

Baker, D.M., K.L Schulz and M.J. Mitchell. A shift in phytoplankton assemblage composition and dynamics during recovery from eutrophication. Limnology and Oceanography. (submitted)

Baker, D.M., K.L Schulz and M.J. Mitchell. Evaluating methods used in monitoring recovery from eutrophication: the importance of examining seasonal trends and the limitations of Chlorophyll-a as a proxy for phytoplankton Biomass. Fundamental and Applied Limnology. (In prep.)

Please contact me for additional information or with questions on any of the publications or this presentation. Thank you and enjoy!

Eutrophication in the U.S.

50% of the lakes classified as impaired (Conley et al. 2009)

Economic losses ~2 billion dollars (Dodds et al. 2009)

Eutrophication in the 21st Century

dailyail.co.uk

Point and non-point loading remains a problem (Schindler and Vallentyne 2008)

toledoblade.comToledoblade.com

clf.orgLake Champlain

Lake Erie

Olympic Venue, China

Symptoms of Eutrophication

P NP N

Figure edited from University of Maryland Center of Environmental Science

Oligotrophic Eutrophic

Variability in Phytoplankton

Differ dramatically in size

Glibert and Burkholder 2011

Fish Orca Factory Eiffel Tower Manhattan

Proch

loroc

occu

sSyn

echo

cocc

usEm

iliania

Astero

lampr

a

Karen

ia

Rhizos

olenia

Cerat

ium

Tricho

dem

ium

10 100 1,000 10,000 100,000

µm

m

Evolution 2nd ed 2009

dnrec.state.de.us

dnrec.state.de.us

Tolweb.org

eos.unh.edu

Bio.miami.edu

dr-ralf-wagner.de

Tolweb.org

plantbiology.msu.edu

serc.carleton.edu

Are extremely phylogenetically diverse

cfb.unh.edu/phycokey

analogicalplanet.com

.rook.org/ea

trees.com

Phytoplankton assemblage will decrease in biomassBut also may change in…

• Taxonomic composition• Diversity• Cell Size • Morphology• Chl-a concentration• Seasonal patterns• Bloom frequency

However, phytoplankton responses are generally monitored by measuring only total Chl-a

Phytoplankton Responses to Recovery from Eutrophication

wyrdscience.wordpress.com

Thesis Goals

The study focuses on the changes in the phytoplankton assemblage during the recovery of a hypereutrophic lake

Two parts:

(1) Do two common monitoring approaches accurately capture the response of phytoplankton parameters to decreasing TP?

(2) How have the dynamics, composition and morphology of the phytoplankton assemblage changed?

Onondaga Lake as a Case Study

Eutrophic due to waste water effluent (METRO)

68% of total phosphorus (TP) 80% of total nitrogen (TN) Ammonium (NH4

+) at toxic levels

Wastewater Treatment Upgrades

TP TP

Reduce Eutrophication

Symptoms

Reduce NH4

+ Levels

TP TP

NH4+ NH4+ NH4

+ NH4+ NO3

- NO3-

High-Rate Flocculated Settling

High-Rate Flocculated Settling

Tertiary Treatment

Tertiary Treatment

Upgraded Tertiary Treatment

Upgraded Tertiary Treatment

Seasonal Nitrification

Seasonal Nitrification

Upgraded Seasonal Nitrification

Upgraded Seasonal Nitrification

Biologically Aerated Filtration

Biologically Aerated Filtration

In 1998 Court order against METRO

By 2008Met NYSDEC TP guidance value of 20 µg/LRemoved from NYSDEC list for NH4

+ toxicity

(15 years, $380 million)

NO3- NO3-

Data Collection

Data for parts one and two were collected biweekly by Onondaga County (METRO)

Phytoplankton enumerated by PhycoTech Biomass data available from

1998 to 2011Calculated annual mean

epilimnion values for all parameters

Thesis Goals

Two parts:

(1) Do two common monitoring approaches accurately capture the response of phytoplankton parameters to decreasing TP?

(2) How have the dynamics, composition and morphology of the phytoplankton assemblage changed?

Part One: Monitoring Approaches

1. Monitoring Approaches Objectives

Objective 1:

Did the response of the phytoplankton parameters (Chl-a and phytoplankton biomass) to the decreases in TP vary seasonally?

Objective 2:

Has the Chl-a content per unit biomass varied due to shifts in the…

(A) light availability? (B) composition of the phytoplankton assemblage?

and/or

Month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Bio

mas

s (u

g/L)

0

10000

20000

30000

40000

50000 Spring Stratification Fall Turnover

Lakes often monitored with calendar date defined periods Annual (April to October) sampling period

Seasonal variability in nutrients, light and mixingDrive seasonal variability in phytoplankton dynamics

Seasonal Variability

1. Monitoring Approaches Background

Different Phytoplankton Taxa

Calendar date defined periods may miss important seasonal trends

Seasonal periods can be easily defined quantitativelyBiological periods (defined with peak detector program)Physical periods (defined with NOAA’s regime shift detector)

Seasonal Periods

1. Monitoring Approaches Background

Month

Mar Apr May Jun Jul Aug Sep Oct Nov

Ch

loro

ph

yll-

a (

ug

/L)

0

10

20

30

40

50 Spring Stratification Fall Turnover

Fall BloomClear-Water

Phase(CWP)

Spring Bloom

Summer StratifiedAnnual

Summer Blooms

Chl-a as a Biomass Proxy

Chl-a used as a proxy for phytoplankton biomassBut Chl-a per unit biomass may vary due to two

mechanisms…(A) Change in light availability

(B) Change in phytoplankton composition

1. Monitoring Approaches Background

Cyanophyceae Chlorophyceae

serc.carleton.edu

Cryptophyceae

plantbiology.msu.edu dnrec.state.de.us

More Chl-aLess Chl-a

Part One: Monitoring Approaches

Objective 1: Seasonal Variability

Did the response of the phytoplankton parameters

to TP vary seasonally?

Seasonal Period

Annual Spring CWP Summer Fall

TP

(mm

ol L

-1)

-0.8

-0.4

0.0

p= 0.3

Annual Spring CWP Summer Fall

Bio

mas

s (

g L

-1)

-3000

-2000

-1000

0

Chl

-a ( g

L-1

)

-4

-2

0 ba

b b

Seasonal PeriodBloom Stratified Bloom

p= 0.03

p= 0.1

Rat

e of

Cha

nge

wit

h Y

ear

Rat

e of

Cha

nge

wit

h Y

ear

Bloom Stratified Bloom

Seasonal Period

Annual Spring CWP Summer Fall

TP

(mm

ol L

-1)

-0.8

-0.4

0.0

p= 0.3

Annual Spring CWP Summer Fall

Bio

mas

s (

g L

-1)

-3000

-2000

-1000

0

Chl

-a ( g

L-1

)-4

-2

0 ba

b b

Seasonal PeriodBloom Stratified Bloom

p= 0.03

p= 0.1

Rat

e of

Cha

nge

wit

h Y

ear

Rat

e of

Cha

nge

wit

h Y

ear

Bloom Stratified Bloom

TP decreased in all seasonal periodsChl-a varied seasonallyTrends in Chl-a and biomass differed

Seasonality in TP, Chl-a and Biomass

1. Monitoring Approaches: Seasonal Variability Results

Significant decrease

Method: ANCOVA and post-hoc F-test

Phytoplankton Response to TPPhytoplankton response to TP weaker in CWP and Fall Bloom

1. Monitoring Approaches: Seasonal Variability Results

Method: Linear Regression

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0p= 0.03

R2 R3Regime 1

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

PredictedObserved

R2 R3Regime 1

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

ObservedPlot 1 Upper control line

R2 R3Regime 1

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0p= 0.03

R2 R3Regime 1

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

PredictedObserved

R2 R3Regime 1

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

ObservedPlot 1 Upper control line

R2 R3Regime 1

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0p= 0.03

R2 R3Regime 1

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

PredictedObserved

R2 R3Regime 1

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

ObservedPlot 1 Upper control line

R2 R3Regime 1

Observed Chl-a vs. Predicted

Method: Two-way ANOVA

Chl-a predicted from standard Chl-a, TP relationship (Vollenweider-OECD, Vollenweider and Kerekes 1980)

Annual

88 94 00 06 12L

og C

hl-a

(m

g L

-1)

0.0

0.5

1.0

1.5

2.0p= 0.03

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

PredictedObserved

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

ObservedPlot 1 Upper control line

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

Spring Bloom

88 94 00 06 12

Clear Water Phase

88 94 00 06 12

Summer Stratified

88 94 00 06 12

Fall Bloom

88 94 00 06 12

PredictedObserved

Seasonal Period

R1 R2 R3

p= 0.03 p= <0.001

p= 0.001 p= 0.006

R2 R3R1 R2 R3R1 R2 R3R1R2 R3Regime 1

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

Spring Bloom

88 94 00 06 12

Clear Water Phase

88 94 00 06 12

Summer Stratified

88 94 00 06 12

Fall Bloom

88 94 00 06 12

PredictedObserved

Seasonal Period

R1 R2 R3 R2 R3R1 R2 R3R1 R2 R3R1R2 R3Regime 1

1. Monitoring Approaches: Seasonal Variability Results

Phosphorus (mg m-3)

Chl

orop

hyll-

a (m

g m

-3)

(Dillon and Rigler 1974)

Annual

88 94 00 06 12

Log

Chl

-a ( g

L-1

)

0.0

0.5

1.0

1.5

2.0p= 0.03

R2 R3Regime 1

Annual

88 94 00 06 12

Log

Chl

-a ( g

L-1

)

0.0

0.5

1.0

1.5

2.0

PredictedObserved

R2 R3Regime 1

Annual

88 94 00 06 12

Log

Chl

-a ( g

L-1

)

0.0

0.5

1.0

1.5

2.0

ObservedPlot 1 Upper control line

R2 R3Regime 1

Annual88 94 00 06 12

Log

Chl

-a ( g

L-1

)

0.0

0.5

1.0

1.5

2.0

Spring Bloom88 94 00 06 12

CWP88 94 00 06 12

Summer Stratified88 94 00 06 12

Fall Bloom88 94 00 06 12

PredictedObserved

Seasonal Period

R1 R2 R3

p= 0.03 p< 0.001

p= 0.001 p= 0.01

R2 R3R1 R2 R3R1 R2 R3R1R2 R3Regime 1

Observed Chl-a vs. Predicted

Method: Two-way ANOVA

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0p= 0.03

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

PredictedObserved

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

ObservedPlot 1 Upper control line

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

Spring Bloom

88 94 00 06 12

Clear Water Phase

88 94 00 06 12

Summer Stratified

88 94 00 06 12

Fall Bloom

88 94 00 06 12

PredictedObserved

Seasonal Period

R1 R2 R3

p= 0.03 p= <0.001

p= 0.001 p= 0.006

R2 R3R1 R2 R3R1 R2 R3R1R2 R3Regime 1

Annual

88 94 00 06 12

Log

Chl

-a (

mg

L-1

)

0.0

0.5

1.0

1.5

2.0

Spring Bloom

88 94 00 06 12

Clear Water Phase

88 94 00 06 12

Summer Stratified

88 94 00 06 12

Fall Bloom

88 94 00 06 12

PredictedObserved

Seasonal Period

R1 R2 R3 R2 R3R1 R2 R3R1 R2 R3R1R2 R3Regime 1

More Chl-a

Less Chl-a

Regime 1 Regime 1 All Years

All Years

1. Monitoring Approaches: Seasonal Variability Results

Part One: Monitoring Approaches

Objective 2: Chl-a Content

Has the Chl-a content per unit biomass varied due to shifts in

(A) light availability and/or

(B) the composition of the phytoplankton assemblage?

Change in Chl-a per unit Biomass

Annual Spring CWP Summer Fall

Chl

-a :

Bio

mas

s pe

r ye

ar

-0.0010

-0.0005

0.0000

0.0005

0.0010

Seasonal Period

p= 0.3

Annual Spring CWP Summer Fall

Mea

n li

ght:

TP

pe

r ye

ar

-0.01

0.00

0.01

0.02

Seasonal Period

p= 0.3

Bloom Stratified Bloom

Bloom Stratified Bloom

Method: Linear Regression; ANCOVA and post-hoc F-test

1. Monitoring Approaches: Chl-a Content Results

Increase in Chl-a per unit biomass (Chl-a: biomass)No seasonal variability

Mechanism A: Light Availability

Increase in light availability in annual and seasonal periods

Should yield a decrease in Chl-a per unit biomass

But Chl-a per unit biomass not correlated with light availability

Method: Linear Regression; Pearson Corrleation

1. Monitoring Approaches: Chl-a Content Results

Mechanism B: Phytoplankton

Method: Pearson

Annual Spring CWP Summer Fall

Chl

-a :

Bio

mas

s pe

r ye

ar

-0.0010

-0.0005

0.0000

0.0005

0.0010

Seasonal Period

p= 0.3

Annual Spring CWP Summer Fall

Mea

n lig

ht: T

P

per

year

-0.01

0.00

0.01

0.02

Seasonal Period

p= 0.3

Bloom Stratified Bloom

Bloom Stratified Bloom

Negatively correlated with a decrease in Cyanophyceae relative biomass in Annual and CWP

Positively correlated with a decrease in Chlorophyceae relative biomass in Spring Bloom

Positively correlated with an increase in Cryptophyceae relative biomass in the Fall Bloom

1. Monitoring Approaches: Chl-a Content Results

TP, Chl-a and biomass all decreasedResponse to decreased TP varied markedly between seasons

Month

Mar Apr May Jun Jul Aug Sep Oct Nov

Ch

loro

ph

yll-

a (

ug

/L)

0

10

20

30

40

50 Spring Stratification Fall Turnover

Fall Bloom

Clear-Water Phase

Spring Bloom

Summer Stratified

Was There Seasonal Variability?

1. Monitoring Approaches: Seasonal Variability Discussion

Rate of decrease in Chl-a greatest

Weak Chl-a response to TP

Weak Chl-a + biomass response to TP

Less Chl-a than predicted

More Chl-a than predicted

Year

88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11

Mon

th

JanFebMarAprMayJunJul

AugSepOct

NovDec

Year

88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11

Mon

th

JanFebMarAprMayJunJul

AugSepOct

NovDec

Regime 1 Regime 2 Regime 3

Year

88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11

Mon

th

JanFebMarAprMayJunJul

AugSepOct

NovDec

Year

88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11

Mon

th

JanFebMarAprMayJunJul

AugSepOct

NovDec

Year

88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11

Mon

th

JanFebMarAprMayJunJul

AugSepOct

NovDec

Why Seasonally Defined Periods?S

um

mer S

tratified

An

nu

al

Timing of seasonal periods varies between yearsCalendar date defined periods may fail to capture

the same ecological periods in each year

1. Monitoring Approaches: Seasonal Variability Discussion

Fall Bloom

Spring Bloom

CWP

Chl-a and biomass were not consistently correlatedChl-a per unit biomass increased

(A) Not due to light availability

(B) Driven by change in phytoplankton composition

Indicates the importance of directly measuring phytoplankton biomass

Why Did Chl-a Content Vary?

dnrec.state.de.usNegatively Correlated Positively Correlated Positively Correlated

Cyanophyceae Chlorophyceae

serc.carleton.edu

Cryptophyceae

plantbiology.msu.edudnrec.state.de.us

More Chl-aLess Chl-a

1. Monitoring Approaches: Chl-a Content Discussion

Thesis Goals

Two parts:

(1) Calendar dates defined periods miss important seasonal trends and Chl-a is a weak proxy for biomass due to the variability in Chl-a per unit biomass

(2) How have the dynamics, composition and morphology of the phytoplankton assemblage changed?

Part Two: Assemblage Changes

Objective 1:

Did changes in limnological parameters result in a distinct shift in the phytoplankton assemblage between Regimes 2 and 3 ?

Objective 2:

What were the specific changes in phytoplankton assemblage in terms of diversity, cell size, bloom dynamics, common species, and composition?

2. Assemblage Changes Background

Mean lightMean light

Effect of Limnological Parameters

Phytoplankton assemblages can vary due to...Nutrients

Stoichiometry

Light

1:1 = 1 4:8 = 1/2

2. Assemblage Changes Background

TNTN TPTP

N:PN:P Si:PSi:P Si:NSi:N

Secchi depthSecchi depth

Parameters ExaminedParameters Examined

NH4+:NO3

-NH4+:NO3

-

Increase S:V, decrease nutrient uptake rate

Vary in uptake sites and rate for different nutrients

Vary in Chl-a concentration Some mobile or bouyant

Phytoplankton assemblage may change in…

Diversity

Cell Size

Bloom frequencies

Number of common species

Taxonomic composition

• Class Level

• Functional groups

Phytoplankton Assemblage Changes

≥ 80% of phytoplankton biomassSp. 1 Sp. 2 Others

Top 90% of phytoplankton biomass

Unicellular

or

Colonial

≤ 3 species

Large Small

2. Assemblage Changes Background

Part Two: Assemblage Changes

Objective 1: Limnological Parameters

Did changes in limnological parameters

result in a distinct shift in the phytoplankton assemblage between Regimes 2 and 3 ?

Nutrient Parameters

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

NH

4+:N

O3-

0123

Si:P

0.0

0.4

0.8

N:P

0

100

200

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

SD (

m)

0

2

4

6

Mea

n li

ght

0.25

0.50

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

TN

(m

ol L

-1)

0

150

300

TP

(m

ol L

-1)

0

2

4 Regime 1 Regime 2 Regime 3

p= 0.2

p= 0.001

p= 0.8

p= 0.9Si

:N

0

250

500

p= 0.002

p= <0.001

p= 0.005

p= 0.005

Regime 1 Regime 2 Regime 3

Regime 1 Regime 2 Regime 3

Limnological Parameters

2. Assemblage Changes: Limnological Parameters Results

TP decreased

Method: Linear Regression

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

NH

4+:N

O3-

0123

Si:P

0.0

0.4

0.8

N:P

0

100

200

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

SD (

m)

0

2

4

6

Mea

n li

ght

0.25

0.50

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

TN

(m

ol L

-1)

0

150

300

TP

(m

ol L

-1)

0

2

4 Regime 1 Regime 2 Regime 3

p= 0.2

p= 0.001

p= 0.8

p= 0.9Si

:N

0

250

500

p= 0.002

p= <0.001

p= 0.005

p= 0.005

Regime 1 Regime 2 Regime 3

Regime 1 Regime 2 Regime 3

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

NH

4+:N

O3-

0123

Si:P

0.0

0.4

0.8

N:P

0

100

200

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

SD (

m)

0

2

4

6

Mea

n li

ght

0.25

0.50

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

TN

(m

ol L

-1)

0

150

300

TP

(m

ol L

-1)

0

2

4 Regime 1 Regime 2 Regime 3

p= 0.2

p= 0.001

p= 0.8

p= 0.9

Si:N

0

250

500

p= 0.002

p= <0.001

p= 0.005

p= 0.005

Regime 1 Regime 2 Regime 3

Regime 1 Regime 2 Regime 3

Light Parameters

Limnological Parameters

2. Assemblage Changes: Limnological Parameters Results

TP decreased

Method: Linear Regression

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

NH

4+:N

O3-

0123

Si:P

0.0

0.4

0.8

N:P

0

100

200

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

SD (

m)

0

2

4

6

Mea

n li

ght

0.25

0.50

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

TN

(m

ol L

-1)

0

150

300

TP

(m

ol L

-1)

0

2

4 Regime 1 Regime 2 Regime 3

p= 0.2

p= 0.001

p= 0.8

p= 0.9

Si:N

0

250

500

p= 0.002

p= <0.001

p= 0.005

p= 0.005

Regime 1 Regime 2 Regime 3

Regime 1 Regime 2 Regime 3

Stoichiometry Parameters

Limnological Parameters

2. Assemblage Changes: Limnological Parameters Results

TP decreasedN:P, Si:N and

Si:P increasedNH4

+:NO3-

decreased

Method: Linear Regression

1998

1999

2000

2001

2002

2003 2004

2005

2006

2007

2008

2009

2010

2011

Axis 1

Axi

s 2

1998

1999

2000

2001

2002

2003 2004

2005

2006

2007

2008

2009

2010

2011TN

TP

N:P

Si:N

Si:PN:N

Secchi

Axis 1

Axi

s 2

Phytoplankton Assemblage Shift

2. Assemblage Changes: Limnological Parameters Results

Regimes differTP, N:N, Si:N and Si:P

between Regimes Secchi depth

within Regimes TP, TN, N:P most

important drivers

Method: NMDS; BIO-ENV

Regime 1Regime 1

Regime 2Regime 2

RegimeRegime 33

Part Two: Assemblage Changes

Objective 2: Specific Changes

What were the specific changes in the phytoplankton

assemblage in terms of diversity, cell size, bloom

dynamics, common species and composition?

No change in Richness, Shannon’s Diversity, or Evenness

Method: Linear Regression

Diversity Indices

2. Assemblage Changes: Specific Changes Results

Change in Cell Size

Cell size (biovolume) decreased

Method: Linear Regression

2. Assemblage Changes: Specific Changes Results

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Num

ber

of W

eeks

0

5

10

15

20

25Regime 1 Regime 2 Regime 3

p= 0.02

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Num

ber

of W

eeks

0

5

10

15

20

25Regime 1 Regime 2 Regime 3

p= 0.02

Change in Bloom PeriodsStrong dominant weeks = weeks with 3 or fewer species are

> 80% of the assemblageSteady states > two consecutive strong dominant weeks

2. Assemblage Changes: Specific Changes Results

Method: Linear Regression, T-test

Number of Common SpeciesIncrease in the number of common species

Peak from 2002-2007

Method: Non-Linear Regression

2. Assemblage Changes: Specific Changes Results

Intermediate Period

Number of Common SpeciesIncrease in the number of common species

Peak from 2002-2007

Variability in common taxa

Method: Non-Linear Regression

2. Assemblage Changes: Specific Changes Results

Intermediate Period

Class Level Composition

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

by C

lass

0.0

0.2

0.4

0.6

0.8

1.0 Charo- Zygnematophyceae Chloro- Chlorophyceae Trebouxiophyceae UlvophyceaeCrypto- CryptophyceaeCyano- CyanophyceaeDino- DinophyceaeEugle- EulgenophyceaeOchro- Bacillarophyceae Chrysophyceae Synurophyceae Xanthophyceae

Clear shift in the composition

2. Assemblage Changes: Specific Changes Results

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.000

0.002

0.004

0.006

0.008

0.010

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.2

0.4

0.6

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.00

0.05

0.10

0.15

0.20

Decrease in relative biomass

Cyanophyceae

serc.carleton.edu

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

Decrease in relative biomassDecrease in size

Cyanophyceae

serc.carleton.edu

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

50

100

150

200

250

300

Regime 2Regime 3

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

400

800

1200

1600

2000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

500

1000

1500

2000

2500

3000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

2000

4000

6000

8000

10000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

500

1000

1500

2000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

1000

2000

3000

4000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

100

200

300

400

500

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0100200300400500600700

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

200

400

600

800

1000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

20

40

60

80

100

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

1000

2000

3000

4000a

b

ab

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.00

0.05

0.10

0.15

0.20

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.00.10.20.30.40.50.6

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4UnicellColonial

Plot 1 Upper specificationPlot 1 Upper control line

Decrease in relative biomassDecrease in sizeShift from large colonial to small unicellular

Cyanophyceae

serc.carleton.edu

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

# C

omm

on S

peic

es

0

2

4

6

8

10

Charo- Zygnematophyceae Chloro- Chlorophyceae Trebuxiophyceae

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

# C

omm

on S

peic

es

0

2

4

6

8

10

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

# C

omm

on S

peic

es

0

2

4

6

8

10

Decrease in relative biomassDecrease in sizeShift from large colonial to small unicellularDecrease in commonness

Cyanophyceae

serc.carleton.edu

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.000

0.002

0.004

0.006

0.008

0.010

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.2

0.4

0.6

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.00

0.05

0.10

0.15

0.20

Chrysophyceae + Synurophyceae

Increase in relative biomass Chrysophyceae Synurophyceae

dr-ralf-wagner.de

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

Chrysophyceae + Synurophyceae

Increase in relative biomassDecrease in size

Chrysophyceae Synurophyceae

dr-ralf-wagner.de

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

50

100

150

200

250

300

Regime 2Regime 3

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

400

800

1200

1600

2000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

500

1000

1500

2000

2500

3000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

2000

4000

6000

8000

10000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

500

1000

1500

2000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

1000

2000

3000

4000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

100

200

300

400

500

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0100200300400500600700

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

200

400

600

800

1000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

20

40

60

80

100

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

1000

2000

3000

4000a

b

ab

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

SmallLargePlot 1 Upper specificationPlot 1 Upper control line

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

50

100

150

200

250

300

Regime 2Regime 3

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

400

800

1200

1600

2000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

500

1000

1500

2000

2500

3000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

2000

4000

6000

8000

10000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

500

1000

1500

2000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

1000

2000

3000

4000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

100

200

300

400

500

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0100200300400500600700

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

200

400

600

800

1000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

20

40

60

80

100

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

1000

2000

3000

4000a

b

ab

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.00

0.05

0.10

0.15

0.20

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.00.10.20.30.40.50.6

Chrysophyceae + Synurophyceae

Increase in relative biomassDecrease in size Increase in both large and small Chrysophytes

Chrysophyceae Synurophyceae

dr-ralf-wagner.de

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

SmallLargePlot 1 Upper specificationPlot 1 Upper control line

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

# C

omm

on S

peic

es

0

1

2

3

4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

# C

omm

on S

peic

es

0

2

4

6

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

# C

omm

on S

peic

es

0

2

4

6

8

10

Chrysophyceae + Synurophyceae

Increase in relative biomassDecrease in size Increase in both large and small Chrysophytes Increase in commonness

Chrysophyceae Synurophyceae

dr-ralf-wagner.de

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.000

0.002

0.004

0.006

0.008

0.010

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.2

0.4

0.6

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.00

0.05

0.10

0.15

0.20

Bacillariophyceae

Increase in relative biomass

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

Bacillariophyceae

Increase in relative biomassNo change in size

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

50

100

150

200

250

300

Regime 2Regime 3

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

400

800

1200

1600

2000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

500

1000

1500

2000

2500

3000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

2000

4000

6000

8000

10000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

500

1000

1500

2000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

1000

2000

3000

4000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

100

200

300

400

500

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0100200300400500600700

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

200

400

600

800

1000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

20

40

60

80

100

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

1000

2000

3000

4000a

b

ab

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.2

0.4

0.6

Bacillariophyceae

Increase in relative biomassNo change in sizeShift to large species

SmallLargePlot 1 Upper specificationPlot 1 Upper control line

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

# C

omm

on S

peic

es

0

1

2

3

4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

# C

omm

on S

peic

es

0

2

4

6

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

# C

omm

on S

peic

es

0

2

4

6

8

10

Bacillariophyceae

Increase in relative biomassNo change in sizeShift to large species No change in commonness

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

Charo- Zygnematophyceae Chloro- Chlorophyceae Mamiellophyceae Nephroselmidophyceae Trebouxiophyceae Ulvophyceae

Crypto- CryptophyceaeCyano- CyanophyceaeDino- DinophyceaeEugleno- EulgenophyceaeOchro- Bacillarophyceae Chrysophyceae Synurophyceae Xanthophyceae

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.000

0.002

0.004

0.006

0.008

0.010

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.2

0.4

0.6

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11R

elat

ive

Bio

mas

s0.00

0.05

0.10

0.15

0.20

Dinophyceae

No change in relative biomasseos.unh.edu

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

Dinophyceae

No change in relative biomassNo change in size eos.unh.edu

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

50

100

150

200

250

300

Regime 2Regime 3

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

400

800

1200

1600

2000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

500

1000

1500

2000

2500

3000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

2000

4000

6000

8000

10000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

500

1000

1500

2000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

1000

2000

3000

4000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

100

200

300

400

500

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0100200300400500600700

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

200

400

600

800

1000

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

20

40

60

80

100

Regime

2 3

Bio

volu

me

(mm

3 nat

ural

uni

t-1)

0

1000

2000

3000

4000a

b

ab

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.00

0.05

0.10

0.15

0.20

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

Rel

ativ

e B

iom

ass

0.0

0.1

0.2

0.3

0.4

Dinophyceae

No change in relative biomassNo change in sizeDecrease in large species

eos.unh.edu

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

SmallLargePlot 1 Upper specificationPlot 1 Upper control line

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

# C

omm

on S

peic

es

0

1

2

3

4

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

# C

omm

on S

peic

es

0

2

4

6

Year

98 99 00 01 02 03 04 05 06 07 08 09 10 11

# C

omm

on S

peic

es

0

2

4

6

8

10

Dinophyceae

No change in relative biomassNo change in sizeDecrease in large speciesNo change in commonness

eos.unh.edu

Method: Linear Regression; T-test

2. Assemblage Changes: Specific Changes Results

Effect of Limnological Parameters

Shift in phytoplankton assemblage between Regimes 2 and 3

TNTN TPTP

N:PN:P Si:PSi:P Si:NSi:N

Secchi depthSecchi depth

Mean lightMean light

Parameters ExaminedParameters Examined

NH4+:NO3

-NH4+:NO3

-

Change in TP and Stoichiometric parameters

TN, TP and N:P correlated with changes in phytoplankton

2. Assemblage Changes: Limnological Parameters Discussion

Effect of Limnological Parameters

Shift in phytoplankton assemblage between Regimes 2 and 3

TNTN TPTP

N:PN:P Si:PSi:P Si:NSi:N

Secchi depthSecchi depth

Mean lightMean light

Parameters ExaminedParameters Examined

NH4+:NO3

-NH4+:NO3

-

Change in TP and Stoichiometric parameters

TN, TP and N:P correlated with changes in phytoplankton

2. Assemblage Changes: Limnological Parameters Discussion

Change in Phytoplankton Assemblage

No Change in Diversity

Decrease in Cell Size

Decrease in Bloom Frequency

Increase in # of Common Species

Shift in Taxonomic composition

• Class Level

• Functional GroupsUnicellularColonial

Eutrophic Species

MesotrophicSpecies

15.6 weeks yr-1 8 weeks yr-1

10 sp. yr-1 17 sp. yr-1

Bacillariophyceae Chrysophyceae Synurophyceae

Cyanophyceae

Large Small

Regime 3Regime 2

2. Assemblage Changes: Specific Changes Discussion

Thesis Goals

Two parts:

(1) Calendar dates defined periods miss important seasonal trends and Chl-a is a weak proxy for biomass due to the variability in Chl-a per unit biomass

(2) Changes in the phytoplankton assemblage included decreased cell size, decreased number of bloom periods, increased number of common species and a shift in composition to less eutrophic taxa

Thesis Goals

Two parts:

(1) Calendar dates defined periods miss important seasonal trends and Chl-a is a weak proxy for biomass due to the variability in Chl-a per unit biomass

(2) Changes in the phytoplankton assemblage included decreased cell size, decreased number of bloom periods, increased number of common species and a shift in composition to less eutrophic taxa

Part One: Conclusions

Julian date periods may be easy to define but may miss important seasonal trendsMethods used here represent a simple method for

consistently defining seasonal periods between years

Chl-a is a weak proxy for phytoplankton biomass

Part Two: Conclusions

Large shift in phytoplankton assemblage driven mostly by TN, TP and N:P

Edibility increasing (cell size decreased) More phytoplankton taxa are considered common Shift from eutrophic to mesotrophic species

Decrease in nuisance species (Cyanobacteria) and increase in more edible species

Chrysophyceae and Synurophyceae were not present in the lake sample record before 1998 (found only in the paleolimnogical record)

ImplicationsImplicationsUsing seasonal periods, measuring Using seasonal periods, measuring phytoplankton biomass directly and phytoplankton biomass directly and

examining the phytoplankton examining the phytoplankton assemblage will allow managers to see assemblage will allow managers to see

more directly what is driving year to more directly what is driving year to year variation in metrics associated year variation in metrics associated with improved water quality (secchi with improved water quality (secchi

depth) resulting in higher-quality depth) resulting in higher-quality management decisions. management decisions.

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