The impact of sea animals on viruses

It is estimated that ocean viruses are in abundance of up to 10⁸ mL-¹. While studies have been undertaken to understand the impact sea viruses have on their host, little is understood regarding the impact ocean animals have on the viruses, until now. A study by Jennifer Walsh has discovered that sea animals can eliminate water viruses.

Sea animals as a filtration system

Through the use of the marine algal virus PgV-07T as a representative model system, Welsh studied the interaction of several non-host organisms with the virus. These organisms

  • Anemones
  • Cockles
  • Sea squirts
  • Polychaete larvae
  • Sponges
  • Crabs
  • Oysters

were monitored to ascertain the impact they have on macro parasite-host systems, known as transmission interference. These specific sea animals were chosen due to their geographic distribution concurrent with the algal host-virus model system. These organisms provide a variety of feeding mechanisms, such as filter feeders and predators, and range in size.

Transmission interference study method

The first experiment involved assessing the organisms’ ability to remove infectious virus particles from the surrounding water; essentially, their ability to interfere with the pathway of marine virus-host transmission.

The second experiment was carried out to analyse sponges and their ability to remove PgV continuously over a prolonged period. This experiment was formed as a continuance of experiment one, where the sponges significantly decreased the abundance of PgV.

Sea animals vs viruses results

Of the species analysed, there were four who played the most prominent role in significantly reducing viral abundance.

  • Sponges - 98% reduction in viral abundance
  • Crabs - 90% reduction in viral abundance
  • Cockles - 43% reduction in viral abundance
  • Oysters - 13% reduction in viral abundance

The second experiment confirmed that Breadcrumb sponges were able to reduce viruses at a rate of 176 mL h-¹ g tissue dry wt-¹ continually over an extended period.

The study concludes, therefore, that the range of non-host organisms capable of decreasing viral abundance highlights that viral ecology is overlooking viral loss via ambient organisms. Additionally,  temperate sponges hold great potential to remove viruses from the water column effectively.

Applications to natural habitat

Although the results of this study have been astounding, Walsh believes that the application to the natural habitat will not be as clear cut as the laboratory-based experiment.

The presence of additional animal species and their influence on each other, tidal currents, UV light and temperature, will all have an impact on the volume of viral abundance removed. However, this does not mean that these results should not be taken into consideration.

Applications to aquaculture

This study has potential applications to saltwater farms, for example, where the sea animals are kept together in a monoculture. This naturally increases the opportunity for an outbreak of disease that would spread to wildlife living in the sea.

Through the addition of sponges, the potential of an outbreak can be highly decreased.

On 30th March this year, Welsh will defend her thesis that suggests that ambient non-host organisms are removing viruses. Due to the spread of coronavirus, the committee will be held online.



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