Picture taken from our water sample microscopy April 22, 2020 featuring Thalassiosira and Skeletonema - welcome signs of spring.
The phytoplankton are beginning to bloom. Plankton help keep our air full of oxygen and our ocean well fed. However, when they bloom means it is time to be cautious with shellfish collecting. There are a few plankton species that produce toxins which are very harmful and even lethal to humans. Cooking and freezing have no impact on the toxin levels. So, it is important to stay informed if you are going to consume wild shellfish.
Blue mussels (Mytilus edulis) at Nahku Bay during low tide.
STC’s environmental department is continuing to collect blue mussels and water samples in order to monitor for harmful algal blooms in Nahku Bay. The lab in Sitka, where we send our samples for analysis, is still operating at a limited capacity. STC has sent in three samples over the last month; the first two have come back well under the FDA regulatory limit for paralytic shellfish poisoning (PSP), and results for the third have not come in yet. However, Ketchikan has begun to see levels over the regulatory limit already this season.
Results for Skagway’s shellfish tests can be seen on STC’s website at http://www.skagwaytraditional.org/psp through the “Historic Data” link or on Seator’s website at www.seator.org/data.
PSP results from STC’s environmental department web page.
It is important to note that currently the Sitka lab is only able to test for toxins from one of the three harmful plankters that we see here in SE Alaska. They are building their capacity, and they should be able to test for toxins from the other two species in the near future.
In addition to sending in shellfish samples every two weeks to be tested for PSP toxins, we collect water samples every week which we look at under the microscope. By looking at the water samples, we can see if there are any of the plankton species present that produce harmful toxins. Just because one of the plankton species are present doesn’t mean that the shellfish will necessarily be over safe limits for toxins, however, they can be a good indicator.
Pseudo-nitzschia seen in a water sample from late April. Pseudo-nitzchia can produce a neurotoxin called domoic acid which causes a neurological disorder known as amnesic shellfish poisoning.
In our last week’s water sample, we started to see an uptake in the number of Pseudo-nitzschia, one of the harmful plankters.
Reuben Cash, our environmental coordinator collecting water samples at Nahku Bay.
We will keep collecting shellfish samples to send to the Sitka lab and monitor water samples for harmful plankton species. Check our website and Seator’s for updates. When PSP levels go above the recommended levels, public service announcements will be posted. Keep an eye out because this is the time of year, we start to see levels rise.