Scientists estimate that our oceans contain approximately 10^8 (one hundred million) viruses per milliliter. Yet, very little is known about the interaction with non-host marine animals. A team of researchers discovered that various sea creatures are able to filter viruses from seawater.

The North Sea coast - Image Credit: mark_gusev via shutterstock - HDR tune by Universal-Sci

Researchers discovered that various sea creatures are able to absorb virus particles while filtering seawater to get oxygen and food. Sponges, in particular, seem to be exceptionally good at this. The findings have been published in the science journal Nature.

When it comes to seas and oceans, viruses are the most plentiful occurring biological entities. Scientists estimate that approximately 10^8 (one hundred million) viruses per milliliter dwell in our oceans. Interestingly though, despite its possible ecological impact, very little is known concerning virus removal by ambient non-host organisms.

Jennifer Welsh, lead author of the Nature article, explained in an interview with the Royal Netherlands Institute for Sea Research that when a virus infects a cell, it uses its host to create new viruses. Later, when those new viruses are released, they can, for their part, infect many more new cells. Welsh observed that the numerous virus particles can also end up for as the food for a varied assortment of sea animals.

As an illustration, the Japanese oyster filters seawater to withdraw food ( for instance, bacteria and algae) or oxygen. In doing so, the oyster also ingests virus particles. According to Welsh, the research team found that in their experiments (during which they did not feed the oysters forcing them to only filter the water for oxygen intake), the oysters removed 12% of the virus particles contained in the water.

The scientists tested the filtering capabilities of various non-host sea animals at the Royal Netherlands Institute for Sea Research virus ecology lab. The aforementioned Japanese oyster, with its 12% filtering performance, took up the fourth place in terms of efficiency. Sponges, crabs, and cockles made it to the podium. Sponges turned out to be the most efficient, filtering viruses from seawater for up to 94% within just 3 hours. An additional investigation revealed that the uptake of viruses happens very fast and effectively, even when additional viruses were introduced to the water every twenty minutes, the sponges remained remarkably efficient in filtering viruses.

Sea sponges appear to be particularly good at filtering viruses. - Image Credit: Humbak via shutterstock - HDR tune by Universal-Sci

Up until recently, scientists didn't know that a number of non-host sea-dwelling species could have such a substantial impact on virus populations. Nevertheless, Welsh noted that the results observed in the lab might not be the same as in real-life conditions as there are many additional variables at play.

Usefulness

The newly found understandings could, in time, be beneficial in aquaculture. Various types of fish and shellfish that are intended for human consumption, are held in enclosures with a direct link to the sea or ocean.

Aquaculture is growing to become a more significant and sustainable substitute for fishing. However, there is a lot of criticism from conservationists. According to Welsh, this is due to the fact that large amounts of fish of a single species are customarily put together in a single saltwater farm. As these fish live together in monoculture, a contagious disease outbreak creates a high risk of spreading to wild fish populations living out at the sea or ocean. Adding virus-filtering sea sponges to the farm could reduce the danger of a virus outbreak. This potential use case would be an ideal topic for further research.

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