The 2009 Alexandrium bloom

Donald M. Anderson- Woods Hole Oceanographic Donald M. Anderson- Woods Hole Oceanographic InstitutionInstitution

Scott Libby - Battelle, Brunswick, MEScott Libby - Battelle, Brunswick, ME

Overview of MWRA’s InvolvementOverview of MWRA’s Involvement• Ambient Monitoring Plan and Contingency Plan call on Ambient Monitoring Plan and Contingency Plan call on

MWRA to support targeted MWRA to support targeted AlexandriumAlexandrium monitoring monitoring– Development of the Development of the AlexandriumAlexandrium Rapid Response Plan Rapid Response Plan

• Gain a better understanding of bloom dynamics and Gain a better understanding of bloom dynamics and

• Evaluate the potential impact of MWRA outfall Evaluate the potential impact of MWRA outfall

– MWRA has conducted MWRA has conducted AlexandriumAlexandrium focused sampling the last five years focused sampling the last five years

– Often in conjunction with efforts of WHOI/GOMTOX and CCSOften in conjunction with efforts of WHOI/GOMTOX and CCS

So what happened in 2009?So what happened in 2009? – – A moderate regional red tide, with toxicity in Mass Bay A moderate regional red tide, with toxicity in Mass Bay and Boston Harborand Boston Harbor

But first – the 2009 forecastBut first – the 2009 forecast

AlexandriumAlexandrium Population Dynamics Model Population Dynamics ModelCyst Dist. (# / cm^2)

Endogenous Clock

Growth (per day)

Germ. rate (% / day)

Growth = min ( f(PAR) , g(T,S) )

Upward swimming 10 m/day

“Mortality” = 0.1 per day, with a temperature dependence

1997 2004 2005

2006 2007 2008

2004

2005

2006

2007

2008

2008

Hydrodynamics& meteorology

Benthic Cyst 2009 Bloom ensemble seasonal forecast

Scenario 1

Scenario 2

Scenario 3

Scenario 4

Scenario 5

Impact of cyst abundance on the next year’s bloom

(1997)

200520052007200720062006 20082008

Shellfish Shellfish harvesting harvesting closuresclosures

2009 2009 AlexandriumAlexandrium chronology chronology• March 24 – WHOI releases 2008 cyst data and predicts March 24 – WHOI releases 2008 cyst data and predicts

“moderately large” red tide for 2009 – comparable to 2006“moderately large” red tide for 2009 – comparable to 2006

• April 17 – Nauset system PSP toxicity closureApril 17 – Nauset system PSP toxicity closure

• Late April - early May PSP toxicity observed in Maine and NHLate April - early May PSP toxicity observed in Maine and NH

• May 7 – High PSP approaching closure levels at Star Island, NHMay 7 – High PSP approaching closure levels at Star Island, NH

• May 12May 12thth MWRA sampled for MWRA sampled for AlexandriumAlexandrium on regular nearfield on regular nearfield survey (150 cells/L at N18)survey (150 cells/L at N18)

• MWRA conducted three ARRS surveys and a harbor surveyMWRA conducted three ARRS surveys and a harbor survey

• May 22 – North Shore and parts of Mass Bay closedMay 22 – North Shore and parts of Mass Bay closed

• June 3 – Additional closure on South ShoreJune 3 – Additional closure on South Shore

• Abundances reached a maximum of 356 cells/L in late May – Abundances reached a maximum of 356 cells/L in late May – coincident with highest PSP toxicity coincident with highest PSP toxicity

• Bloom ended by June 8Bloom ended by June 8thth survey survey

May 20, 2009May 20, 2009

May 29, 2009May 29, 2009

June 8, 2009 – bloom overJune 8, 2009 – bloom over

Boston Harbor Boston Harbor Closed June 12Closed June 12thth

2008 Boston Harbor counts2008 Boston Harbor counts. .

Boston Harbor sampled June 17th

(cells gone a week later)

Alexandrium Alexandrium abundance – MWRA nearfield areaabundance – MWRA nearfield area

Contingency Plan Threshold Exceedance: >100 cells/L from Contingency Plan Threshold Exceedance: >100 cells/L from May 12May 12thth to 29 to 29thth (≤150 cells/L) (≤150 cells/L)

Baywide Alexandrium Abundance2009 comparable to 2007

Importance of winds for Mass Bay bloomsImportance of winds for Mass Bay blooms

5/4 5/14 5/24 6/3 6/13 6/23

2005

2006

2007

2008

2009

20052005 2007200720062006

20082008

Shellfish Shellfish harvesting harvesting closuresclosures

2009200920092009

SummarySummary• Alexandrium Alexandrium population dynamics model & cyst abundance were population dynamics model & cyst abundance were

good predictors of the magnitude of the 2009 bloomgood predictors of the magnitude of the 2009 bloom

• Winds during the critical May – early June interval were light Winds during the critical May – early June interval were light with only one small Northeasterly event. As a result, 2009 cell with only one small Northeasterly event. As a result, 2009 cell abundance in Mass Bay was relatively low, but still high enough to abundance in Mass Bay was relatively low, but still high enough to cause PSP closures (comparable in geographic extent to 2006, as cause PSP closures (comparable in geographic extent to 2006, as predicted)predicted)

• Early May winds transported cells into Massachusetts Bay, but Early May winds transported cells into Massachusetts Bay, but unlike previous years, there were no subsequent storms and the unlike previous years, there were no subsequent storms and the bloom petered out. The 2009 bloom was offshore most of the bloom petered out. The 2009 bloom was offshore most of the season.season.

• Shellfish toxicity within Massachusetts Bay seems to relate to Shellfish toxicity within Massachusetts Bay seems to relate to transport of blooms from the north. There was no significant transport of blooms from the north. There was no significant stimulation of stimulation of Alexandrium Alexandrium cell abundance in the bay..cell abundance in the bay..

SummarySummary• Boston Harbor cell concentrations were low. This suggests Boston Harbor cell concentrations were low. This suggests

that these populations are transported into the Harbor, and that these populations are transported into the Harbor, and do not originate from in situ cyst germination and growth.do not originate from in situ cyst germination and growth.

• It will be interesting to see the results of the fall 2009 cyst It will be interesting to see the results of the fall 2009 cyst survey. In past years, there has been an survey. In past years, there has been an inverse inverse relationship relationship between the size of the bloom and the size of the resulting between the size of the bloom and the size of the resulting cyst populationcyst population

Impact of cyst abundance on the next year’s bloom

(1997)

Impact of bloom cell abundance on that year’s cyst abundance

(1997)

???

SummarySummary• We still believe we are in a “new era” of frequent and high We still believe we are in a “new era” of frequent and high

levels of PSP toxicity in the western Gulf of Maine. levels of PSP toxicity in the western Gulf of Maine.

AcknowledgementsAcknowledgements

The data presented are the result of the efforts from a variety of intuitions and programs including:– MWRA/Battelle HOM6 team

– WHOI scientists and GOMTOX Program (funded via NOAA/ Center for Sponsored Coastal Ocean Research/Coastal Ocean Program Grant #NA06NOS4780245) and the Woods Hole Center for Oceans and Human Health

– MA DMF PSP data

1997 2004 2005

2006 2007 2008

The 2009 The 2009 Alexandrium fundyenseAlexandrium fundyense bloom bloom

SummarySummary• It will be interesting to see the results of the fall 2009 cyst It will be interesting to see the results of the fall 2009 cyst

survey. In past years, there has been an inverse relationship survey. In past years, there has been an inverse relationship between the size of the bloom and the size of the resulting between the size of the bloom and the size of the resulting cyst populationcyst population

• We still believe we are in a “new era” of frequent and high We still believe we are in a “new era” of frequent and high levels of PSP toxicity in the western Gulf of Maine. levels of PSP toxicity in the western Gulf of Maine.