Viral diversity and Interactions in a Changing Environment on Kelp

Kelps are brown algae from the order Laminariales that predominate along rocky coastal areas with cold and relatively shallow waters around the world. Like other marine photosynthetic organisms, kelps fuel secondary production via macroalgal detritus; thereby supporting complex food webs in coastal zones. Since they grow in dense groupings, like underwater forests, they also provide physical habitat, nursery ground and food for organisms, such as marine mammals, fishes, crabs, sea urchins, mollusks, other algae and epibiota. Kelp forest can alter local oceanography and ecology by dampening wave surge, which influence water flow, coastal erosion, sedimentation, benthic productivity (primary and secondary) and recruitment. Kelp is not just a key species for the marine environment, but also for us. Their multiple industrial applications have led to an increase in the economic importance of seaweed aquaculture. However, 38% of the world's kelp forests have been in decline over the past five decades possibly due to coastal eutrophication and rising sea temperatures, among others. Norwegian Kelp populations have been fluctuating without an obvious reason and, the recent discovery of Phaeoviruses infecting Kelp species opens a new door for studying viral infection as a possible vector for this regime shift. Domesticated seaweeds are more susceptible to abiotic stressors, disease, and parasites. If they are a reservoir for disease, besides the economic burden, they can impact natural populations. ViralICE project therefore aims to find out whether and how kelp viruses affect the natural kelp forest in Norway and kelp aquaculture under the current climate change situation. With help from our Industry partners, IFF and Ocean Forest, we have received kelp samples from Laminaria hyperborea and Saccharina latissima. These kelp species are relevant due to their strong commercial interest in Norway: L. hyperborea as a raw material in alginat production, and S. latissima used for example as animal feed. During 2022, we have been on four research cruises with the research vessel “Hans Brattstrom”. Here we have harvested L. hyperborea and S. latissima at the same locations throughout a full year. Also, since S. latissima grows at more shallow waters compared to L. hyperborea, we have harvested S. latissima from shore at several locations on Haugalandet. We now consider the kelp harvesting for finished, with a total number of 799 samples. From these, 529 samples correspond to S. latissima, and 270 to L. hyperborea, coming from different places along the Norwegian coast (from Troms and Finnmark county, to Rogaland), including the Norwegian fiords (Sognefjorden and Hardangerfjorden). Phaeoviruses have not previously been studied in Norway, but the discovery of Phaeoviruses in kelps from England, makes it likely to find the virus in Norway. To investigate this, DNA has been extracted from the kelp samples, followed by screening for Phaeoviruses using PCR-technology. The results show that most of the kelps contain Phaeoviruses (about 80%), and we have now started sequencing the viral DNA. The DNA-sequences will give us important information on phylogeny and diversity among Phaeoviruses on cultivated and natural kelps in Norway. We have focus on outreaching activities in this research project. The children’s book “Olle Kråkebolle og tareskogens mysterier” was recently published by Vormedal Forlag and is a part of our dissemination plan. Please visit our website www.viralice.net to learn more about the ViralICE-project.

Being the most abundant and diverse entities in planet Earth, marine viruses have been proved to control their host populations, acting as driving force for the inter- and intra-species competition and succession. Their outstanding roles in food webs, competitive interactions, biodiversity patterns, and the regulation of keystone species, manifest therefore, their contribution structuring ecological communities and impacting ecosystem functioning. However, we still do not completely understand how viruses interact with their hosts. Kelp forest (brown algae from the order Laminariales) impacts local oceanography and ecology, and constitute enormous energy sources for coastal benthic secondary production supporting fisheries worldwide; from temperate, to polar rocky ecosystems. Kelp deforestation has been reported globally and, after the recent discovery of Phaeoviruses on kelp, viral diseases should be taken into consideration. Evidence posses that host-pathogen interactions will become more frequent and intense in the future, leading to higher virus multiplication rates, increased transmission and host species jumps. Wild seaweed domestication is making crops more susceptible to abiotic stressors, disease and parasites, and these may act as a disease reservoir which could impact natural populations. Therefore, viral infection could not only affect natural kelp forest, but also impact the Norwegian blue bioeconomy. ViralICE has been designed to throw some light into viral diseases that could potentially affect kelp communities and relevant species to the Norwegian industry. This project intends to contribute with Phaeoviral infection knowledge in brown algae, and we will: 1) study Phaeoviral diversity, 2) study the Phaeoviral host-range, 3) study the potential ecological consequences of climate change on algal-pathogen interactions, and 4) build relevant networks between research communities, industry and government.