Using DNA barcodes to detect harmful algal bloom forming plankton in the Arctic

Authors

1. R.E. Collins, Centre for Earth Observation Science, University of Manitoba, Winnipeg, Manitoba, Canada, eric.collins@umanitoba.ca
2. R.M. Lekanoff, College of Fisheries and Ocean Science, University of Alaska Fairbanks, Fairbanks, Alaska, United States

Citation information

Collins, R.E. and Lekanoff, R.M. 2020. Using DNA barcodes to detect harmful algal bloom-forming plankton in the Arctic. Polar Knowledge: Aqhaliat Report, volume 3, Polar Knowledge Canada, p. 18–22. DOI: 10.35298/pkc.2020.05.eng

Abstract

Seawater flows north from the Pacific Ocean through the Bering Strait to the Chukchi Sea, where it then becomes entrained into a stream of water that follows the northern coast of Alaska to the Beaufort Sea and into the Canadian Archipelago. As the Arctic warms, invasive species of algae from the south are expected to be entrained into these water currents, and perhaps even grow in the Arctic. Among these algae are those that produce toxins that are poisonous to fish, marine mammals, and humans, forming Harmful Algal Blooms (HABs) when they grow to high abundance. We used DNA barcoding to identify the relative abundance and distributions of these algae during three research cruises in the Summer of 2017.

Introduction

Several groups of algae form Harmful Algal Blooms, including Cyanobacteria, Dinoflagellates, and Diatoms. Cyanobacteria are not common in the Arctic Ocean, but may be present in ponds and lakes. The main algae that are of potential concern in the Arctic are Pseudo-nitzschia (a diatom) and the dinoflagellates Alexandrium and Dinophysis. Some of these algae can produce toxins that kill fish, while others are eaten by filter feeders like clams, which accumulate the toxins in their tissues. The toxins may be further accumulated in birds (Shearn-Bochsler et al. 2014) or marine mammals that eat the shellfish, like walruses (Lefebvre et al. 2016). When humans eat the poisoned animals, they can become sick.

DNA barcoding is the best technique we have to identify microbes like algae, because many of them look the same under the microscope. However, unique variations in their DNA sequences can allow exact identifications of each microbe, which are named here by the genus they belong to followed by a unique number indicating the rank order of the abundance of that sequence in our dataset.

HAB forming Diatoms

About half of all known species of Pseudo-nitzschia produce a toxin called domoic acid that causes a condition called Amnesic Shellfish Poisoning (Percopo et al. 2016, Tammilehto et al. 2012). We identified three types of Pseudonitzschia in our study. Two types (Pseudo-nitzschia #518 and #849) were typically found at low abundance in colder waters (i.e., below 4 °C). Another type (Pseudo-nitzschia #274) was typically found at higher abundance in warmer (i.e., above 6 °C), fresher waters, and at more northern latitudes. For example, this type was prominent in August between Point Hope and Utqiagvik. Therefore, Pseudo-nitzschia #274 may be more likely to make it into Canadian waters than the other types.

HAB forming Dinoflagellates

Alexandrium species can produce a toxin called saxitoxin that causes a condition known as Paralytic Shellfish Poisoning (Gessner and Middaugh 2015, Natsuike et al. 2013, Natsuike et al. 2017, Vandersea et al. 2017). We identified 14 types of Alexandrium in our study, but only two were relatively common. Alexandrium #17 was one of the most abundant plankton species detected in our study. It was present in all conditions in the Chukchi Sea, being especially prominent in August. A less abundant type (Alexandrium #99) was present primarily in warmer, fresher, coastal waters similar to Pseudo-nitzschia #274. As a result of their distributions in the Chukchi Sea, both of these types of algae are likely to make it into Canadian waters.

Dinophysis species can produce toxins called okadaic acid and dinophysistoxin that cause a condition known as Diarrhetic Shellfish Poisoning. Dinophysis were quite rare in our study. We identified only deux types (Dinophysis #1901 and #4867) that were present occasionally in waters warmer than 4 °C.

Community consideration

The safety of country foods is a prominent concern for local communities that rely on these traditional sources of sustenance. We do not yet know if any of the species we have identified here produce toxins in nature, although domoic acid and saxitoxin have both recently been found in shellfish from the Bering Strait. Climate change is expected to alter the structure of plankton communities and may allow the introduction of harmful species that were not present before. Now that we have built a database of DNA barcodes for arctic algae, we will continue to monitor their abundance and distribution in the Alaskan and Canadian Arctic. To do this, we will recruit community-based observers into the program to collect samples, report their observations on water quality and animal health, and engage their communities to better understand the roles that microbes play in the environment. In addition, we will work to discover which of these arctic taxa produce toxins and under what conditions, to better predict where and when HABs might occur in the Arctic.

Acknowledgements

This research was funded by the National Oceanographic Partnership Program through the Arctic Marine Biodiversity Observing Network (NA14NOS0120158), the National Oceanic and Atmospheric Administration (NA15OAR0110208, NA14OAR0110266), the North Pacific Research Board (NA17NMF4720289 subaward 1802), and the National Science Foundation (OPP #1303901). We thank the captain, crew, and fellow scientists during the following research cruises: DBO-NCIS (US CGC Healy), ASGARD (R/V Sikuliaq), and AMBON (Norseman II).

Online resources

• Alaska Harmful Algal Bloom Network. Arctic Ocean Observing Network
• Shellfish Poisoning Resources. Alaska Department of Health and Social Services
• Alaska Marine Biotoxin Monitoring and Contigency Plan for Bivalve Shellfish (other than Geoducks). Alaska Department of Environmental Conservation.
• Sitka Tribe of Alaska Environmental Research Lab
• Bering Strait: Walruses and Saxitoxin-late summer/fall 2017. Alaska Sea Grant
• Paralytic shellfish poisoning—Alaska, 1993-2014. State of Alaska Epidemiology Bulletin
• Little Known About Algal Toxins' Effects on Subsistence in Arctic Waters. KNOM, Nome, Alaska

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