The 2009 Alexandrium bloom Donald M. Anderson- Woods Hole Oceanographic Institution Scott Libby - Battelle, Brunswick, ME

Overview of MWRA’s Involvement Ambient Monitoring Plan and Contingency Plan call on MWRA to support targeted Alexandrium monitoringAmbient Monitoring Plan and Contingency Plan call on MWRA to support targeted Alexandrium monitoring –Development of the Alexandrium Rapid Response Plan Gain a better understanding of bloom dynamics andGain a better understanding of bloom dynamics and Evaluate the potential impact of MWRA outfallEvaluate the potential impact of MWRA outfall –MWRA has conducted Alexandrium focused sampling the last five years –Often in conjunction with efforts of WHOI/GOMTOX and CCS So what happened in 2009? – A moderate regional red tide, with toxicity in Mass Bay and Boston Harbor – A moderate regional red tide, with toxicity in Mass Bay and Boston Harbor

But first – the 2009 forecast

Alexandrium Population Dynamics Model Cyst 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

Hydrodynamics & meteorology Benthic Cyst2009 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)

Shellfish harvesting closures

2009 Alexandrium chronology March 24 – WHOI releases 2008 cyst data and predicts “moderately large” red tide for 2009 – comparable to 2006 March 24 – WHOI releases 2008 cyst data and predicts “moderately large” red tide for 2009 – comparable to 2006 April 17 – Nauset system PSP toxicity closure April 17 – Nauset system PSP toxicity closure Late April - early May PSP toxicity observed in Maine and NH Late April - early May PSP toxicity observed in Maine and NH May 7 – High PSP approaching closure levels at Star Island, NH May 7 – High PSP approaching closure levels at Star Island, NH May 12 th MWRA sampled for Alexandrium on regular nearfield survey (150 cells/L at N18) May 12 th MWRA sampled for Alexandrium on regular nearfield survey (150 cells/L at N18) MWRA conducted three ARRS surveys and a harbor survey MWRA conducted three ARRS surveys and a harbor survey May 22 – North Shore and parts of Mass Bay closed May 22 – North Shore and parts of Mass Bay closed June 3 – Additional closure on South Shore June 3 – Additional closure on South Shore Abundances reached a maximum of 356 cells/L in late May – coincident with highest PSP toxicity Abundances reached a maximum of 356 cells/L in late May – coincident with highest PSP toxicity Bloom ended by June 8 th survey Bloom ended by June 8 th survey

May 20, 2009

May 29, 2009

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

Boston Harbor Closed June 12 th 2008 Boston Harbor counts. Boston Harbor sampled June 17 th (cells gone a week later)

Alexandrium abundance – MWRA nearfield area Contingency Plan Threshold Exceedance: >100 cells/L from May 12 th to 29 th (≤150 cells/L)

Baywide Alexandrium Abundance 2009 comparable to 2007

Importance of winds for Mass Bay blooms

5/4 5/14 5/24 6/3 6/13 6/ GoMOOS Buoy A data supplied by Neal Pettigrew's group at the University of Maine 2009

Shellfish harvesting closures

Summary Alexandrium population dynamics model & cyst abundance were good predictors of the magnitude of the 2009 bloomAlexandrium population dynamics model & cyst abundance were good predictors of the magnitude of the 2009 bloom Winds during the critical May – early June interval were light with only one small Northeasterly event. As a result, 2009 cell abundance in Mass Bay was relatively low, but still high enough to cause PSP closures (comparable in geographic extent to 2006, as predicted)Winds during the critical May – early June interval were light with only one small Northeasterly event. As a result, 2009 cell abundance in Mass Bay was relatively low, but still high enough to cause PSP closures (comparable in geographic extent to 2006, as predicted) Early May winds transported cells into Massachusetts Bay, but unlike previous years, there were no subsequent storms and the bloom petered out. The 2009 bloom was offshore most of the season.Early May winds transported cells into Massachusetts Bay, but unlike previous years, there were no subsequent storms and the bloom petered out. The 2009 bloom was offshore most of the season. Shellfish toxicity within Massachusetts Bay seems to relate to transport of blooms from the north. There was no significant stimulation of Alexandrium cell abundance in the bay..Shellfish toxicity within Massachusetts Bay seems to relate to transport of blooms from the north. There was no significant stimulation of Alexandrium cell abundance in the bay..

Summary Boston Harbor cell concentrations were low. This suggests that these populations are transported into the Harbor, and do not originate from in situ cyst germination and growth.Boston Harbor cell concentrations were low. This suggests that these populations are transported into the Harbor, and do not originate from in situ cyst germination and growth. It will be interesting to see the results of the fall 2009 cyst survey. In past years, there has been an inverse relationship between the size of the bloom and the size of the resulting cyst populationIt will be interesting to see the results of the fall 2009 cyst survey. In past years, there has been an inverse relationship between the size of the bloom and the size of the resulting cyst population

Impact of cyst abundance on the next year’s bloom (1997)

Impact of bloom cell abundance on that year’s cyst abundance (1997) ???

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

Acknowledgements 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 #NA06NOS ) and the Woods Hole Center for Oceans and Human Health –MA DMF PSP data

The 2009 Alexandrium fundyense bloom

Summary It will be interesting to see the results of the fall 2009 cyst survey. In past years, there has been an inverse relationship between the size of the bloom and the size of the resulting cyst populationIt will be interesting to see the results of the fall 2009 cyst survey. In past years, there has been an inverse relationship between the size of the bloom and the size of the resulting cyst population We still believe we are in a “new era” of frequent and high levels of PSP toxicity in the western Gulf of Maine.We still believe we are in a “new era” of frequent and high levels of PSP toxicity in the western Gulf of Maine.