Abstract Title

Session S-09A: Harmful Algal Blooms, Climate, Shellfish, and Public Health - Emerging Issues in a Changing World

Proposed Abstract Title

Paralytic shellfish poisoning: The need for historical records of Alexandrium to foresee the future

Keywords

Harmful Algal Blooms and Shellfish

Location

Room 615-616-617

Start Date

2-5-2014 10:30 AM

End Date

2-5-2014 12:00 PM

Description

Paralytic shellfish poisoning (PSP) in Puget Sound is generally caused by the dinoflagellate genus Alexandrium. Formal records of PSP in the Puget Sound date back only to the 1960s. The existing 50-year PSP records may not provide a long-enough timeframe to infer the impacts of climate change on Alexandrium populations. After a bloom, Alexandrium can form a dormant cyst stage that rests on the seafloor and serves as the inoculum for subsequent blooms. Historical abundances of Alexandrium cysts in sediments may act as a proxy record, allowing us to statistically assess whether or not PSP is increasing in frequency and if so, what the causes may be. In order to interpret the historical record of Alexandrium cysts, it is important to know if and at what rate cysts in sediments degrade over time. Here we report on a laboratory study to assess the role that cyst fullness and age may have on germination success. Sediments were dated using the isotope Lead-210. Cysts of Alexandrium spp. were isolated from a 100-cm core collected in Sequim Bay, WA in December 2011, imaged and placed in germination well plates with growth medium. Germination was monitored for four weeks. The image analysis program Image J and a custom-designed plug-in called "Dinocyst" were used to quantitatively measure the surface area of the cysts’ internal contents. An index of cyst fullness and age is compared with germination success or failure. Our research indicates that the cyst stage can remain viable in sediments for an est. 50-80 years, show little visual evidence of physical degradation, and germination rates are relatively constant over this timescale. These new results are used to help us interpret a historical reconstruction of Alexandrium cysts from sediment cores. Longer records of Alexandrium will allow us to better infer how changes in sea surface temperature, air temperature and climate change are affecting HABs regionally.

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May 2nd, 10:30 AM May 2nd, 12:00 PM

Paralytic shellfish poisoning: The need for historical records of Alexandrium to foresee the future

Room 615-616-617

Paralytic shellfish poisoning (PSP) in Puget Sound is generally caused by the dinoflagellate genus Alexandrium. Formal records of PSP in the Puget Sound date back only to the 1960s. The existing 50-year PSP records may not provide a long-enough timeframe to infer the impacts of climate change on Alexandrium populations. After a bloom, Alexandrium can form a dormant cyst stage that rests on the seafloor and serves as the inoculum for subsequent blooms. Historical abundances of Alexandrium cysts in sediments may act as a proxy record, allowing us to statistically assess whether or not PSP is increasing in frequency and if so, what the causes may be. In order to interpret the historical record of Alexandrium cysts, it is important to know if and at what rate cysts in sediments degrade over time. Here we report on a laboratory study to assess the role that cyst fullness and age may have on germination success. Sediments were dated using the isotope Lead-210. Cysts of Alexandrium spp. were isolated from a 100-cm core collected in Sequim Bay, WA in December 2011, imaged and placed in germination well plates with growth medium. Germination was monitored for four weeks. The image analysis program Image J and a custom-designed plug-in called "Dinocyst" were used to quantitatively measure the surface area of the cysts’ internal contents. An index of cyst fullness and age is compared with germination success or failure. Our research indicates that the cyst stage can remain viable in sediments for an est. 50-80 years, show little visual evidence of physical degradation, and germination rates are relatively constant over this timescale. These new results are used to help us interpret a historical reconstruction of Alexandrium cysts from sediment cores. Longer records of Alexandrium will allow us to better infer how changes in sea surface temperature, air temperature and climate change are affecting HABs regionally.