Phytoplankton are tiny algae that live in the ocean. They can occur in vast numbers and are at the bottom of the food chain that supports all life in the ocean.
When conditions are just right, including supply of nutrients and temperature, phytoplankton numbers can explode, causing a bloom. This in turn can set off a cascade of population growth throughout the ecosystem, from krill to fish, to seabirds, whales, and other life – including important fisheries.
Yet, scientists have observed that sometimes phytoplankton blooms end abruptly and before they run out of nutrients.
In a paper in Nature: The ISME Journal, Andrew Bissett and colleagues from the Australian Antarctic Division sampled water from the Southern Ocean and found a kind of parasite called syndiniales in unprecedented levels near the sea-ice edge of Antarctica, forming as much as 50 per cent of the living matter in the samples.
The team of scientists used DNA sequencing to analyse the water samples, as opposed to looking through a microscope, to get a better understanding of the marine environment.
The discovery of the parasite in such high levels could result in a rethink of how scientists understand the Southern Ocean ecosystem.
Once the plankton-killing parasite infects a cell, they will eventually kill it and until now, scientists have ignored the impacts of parasites in their models of ocean nutrient cycling.
Their presence may explain why phytoplankton blooms sometimes end before they run out of nutrients. However, further research is needed to truly understand the role of this parasite and its impact on the food chain, and in turn on fisheries that humans rely on.
For more details, read the ABC news article.
Image credit: P1100067 Sea and Ice near Antarctic Peninsula by Paul Seligman available at https://www.flickr.com/photos/paul_seligman_cardiff/43049641411/in/photolist under a Creative Commons Attribution 2.0. Full terms available at https://creativecommons.org/licenses/by-nc-nd/2.0/.