Comparisons of phytoplankton community characteristics at different chlorophyll concentrations: “Are we seeing a shift in algal community structure?”– discrete (10µg/L bins)

0-10, 10-20, 20-30, 30-40, 40-50, 50-60, 60-70, 70-80, 80-90, 90-100, >100

– ANOVA, multiple comparison post-hoc test – Species Richness, Species Evenness, Shannon

Diversity, % Dinoflagellate Biomass, % Cyanobacteria Biomass

– Each season and segment analyzed separately– Lower James: Annual corrected YSI chla data, Upper

James: Uncorrected extracted chla data 7/23/14

Todd EgertonOld Dominion University

7/23/14Todd Egerton

Old Dominion University

Phytoplankton community characteristics: Segment: JMSMH Years: 2011-2013 ANOVA/REGWF

ANOVAP<0.000

ANOVAP<0.000

ANOVAP<0.000

Spring (March-May)

Summer (July-August)

ANOVAP<0.000

AA

AB

ANOVAP<0.000

ABCABC

BCBC

CC C

ANOVAP<0.000

N.S.: Species Richness, % Cyano

Comparisons of exceeding HAB thresholds at different chlorophyll concentrations: “What proportion of samples within a given Chla range exceed a HAB density of concern?”

7/23/14Todd Egerton

Old Dominion University

Comparisons of exceeding HAB thresholds at different chlorophyll concentrations: “What proportion of samples within a given Chla range exceed a HAB density of concern?”

7/23/14Todd Egerton

Old Dominion University

(Wood and Bukaveckas)Chla bins (10µg/L) x likelihood of impairment (proportion of collections when microcystin exceeds a threshold). Microcystin concentrations based on Rangia bioassaysQuestion: test of significance?

Comparisons of exceeding HAB thresholds at different chlorophyll concentrations: “What proportion of samples within a given Chla range exceed a HAB density of concern?”– Cochlodinium polykrikoides• Example thresholds: presence (>10/ml), 1000 cells/ml,

3000 cells/ml, 6000 cells/ml, 12,000 cells/ml

– discrete (10µg/L bins)0-10, 10-20, 20-30, 30-40, 40-50, 50-60, 60-70, 70-80, 80-90, 90-100, >100

– Percentage of samples within each Chla bin with C. polykrikoides densities exceeding thresholds

– 2011-2013, summer season, by segment7/23/14

Todd EgertonOld Dominion University

7/23/14Todd Egerton

Old Dominion University

Cochlodinium polykrikoides thresholdsSeason: summer (July-August) Years: 2011-2013Segments: JMSMH n=165

7/23/14Todd Egerton

Old Dominion University

Cochlodinium polykrikoides thresholdsSeason: summer (July-August) Years: 2011-2013Segments: JMSPH n=78

7/23/14Todd Egerton

Old Dominion University

Cochlodinium polykrikoides thresholdsSeason: summer (July-August) Years: 2011-2013Segments: ER n=98

7/23/14Todd Egerton

Old Dominion University

Cochlodinium polykrikoides thresholdsSeason: summer (July-August) Years: 2011-2013Segments: LAF n=105

7/23/14Todd Egerton

Old Dominion University

Cochlodinium polykrikoides thresholdsSeason: summer (July-August) Years: 2011-2013Segments: JMSMH, JMSPH, ER & LAF n=446

7/23/14Todd Egerton

Old Dominion University

Cochlodinium polykrikoides thresholdsSeason: summer (July-August) Years: separateSegments: JMSMH, JMSPH, ER & LAF

?tbd

2014

Chla to Cochlodinium abundance• All Summer season data,

all lower James segments, 2011-2013

• Chla>400 excluded• Sig. positive relationships

between Chla and C. polykrikoides densities each year….

• But: different relationships/regressions– 2012 and 2013 similar

• If ‘concern levels’ are >5000 cells/ml, 2011 data shouldn’t be used due to lower bloom densities?

7/23/14Todd Egerton

Old Dominion University

Chla to Cochlodinium abundance• 2012-2013 data merged• Summer (July-September)• JMSMH,JMSPH, LAF, ER• N=301• p<0.000, R2=0.64• Linear RegressionY= C. polykrikoides abundance (cells/ml)

X= Chla µg /L (annual correction)

Y=87.204x-753.91

7/23/14Todd Egerton

Old Dominion University

Chla to Cochlodinium abundance• 2012-2013 data merged• Summer (July-September)• JMSMH,JMSPH, LAF, ER• N=301• p<0.000, R2=0.64• Linear RegressionY= C. polykrikoides abundanceX= corrected Chla (annual)Y=87.204x-753.91

10 cells/ml = 8.8µg Chla/L1000 cells/ml =20.1 Chla/L3000 cells/ml = 43.0 µg Chla/L6000 cells/ml = 77.4 µg Chla/L12,000 cells/ml = 146.3 µg Chla/L

7/23/14Todd Egerton

Old Dominion University

Next steps• Finalize HAB density threshold(s)• Algal community structure analysis for each

segment/season• Additional HAB species (Microcystis aeruginosa in

JMSTF)• 2014 Cochlodinium data (increase confidence in

Chl a relationship)• IBI calculation and analyses• Moving beyond discrete binned analysis:– Changepoint analysis, correlation/regression, PCA,

multivariate (ANOSIM, PERMANOVA) 7/23/14Todd Egerton

Old Dominion University