Work

The effects of elevated CO 2 on the growth and toxicity of field populations and cultures of the saxitoxin-producing dinoflagellate, Alexandrium fundyense

Year: 2014

Type: article

Abstract: The effects of coastal acidification on the growth and toxicity of the saxitoxin-producing dinoflagellate Alexandrium fundyense were examined in culture and ecosystem studies. In culture experiments, Alexandrium strains isolated from Northport Bay, New York, and the Bay of Fundy, Canada, grew significantly faster (16–190%; p < 0.05) when exposed to elevated levels of P CO 2 (∼ 90–190 Pa = 900–1900 μatm) compared to lower levels (∼ 40 Pa = 400 μatm). Exposure to higher levels of P CO 2 also resulted in significant increases (71–81%) in total cellular toxicity (fg saxitoxin equivalents cell−1) in the Northport Bay strain, while no changes in toxicity were detected in the Bay of Fundy strain. The positive relationship between P CO 2 enrichment and elevated growth was reproducible in natural populations from New York waters. Alexandrium densities were significantly and consistently enhanced when natural populations were incubated at 150 Pa P CO 2 compared to ∼ 39 Pa. During natural Alexandrium blooms in Northport Bay, P CO 2 concentrations increased over the course of a bloom to more than 170 Pa and were highest in regions with the greatest Alexandrium abundances, suggesting Alexandrium may further exacerbate acidification and/or be especially adapted to these acidified conditions. The co-occurrence of Alexandrium blooms and elevated P CO 2 represents a previously unrecognized, compounding environmental threat to coastal ecosystems. The ability of elevated P CO 2 to enhance the growth and toxicity of Alexandrium indicates that acidification promoted by eutrophication or climate change can intensify these, and perhaps other, harmful algal blooms.

Source: Limnology and Oceanography

DOI: 10.1002/lno.10012