Algal species such Heterosigma akashiwo and the genus Chrysochromulina can form dense blooms which can be damaging to fisheries, resulting in losses in the aquaculture industry.

[4] Heterosigma akashiwo virus (HaV) has been suggested for use as a microbial agent to prevent the recurrence of toxic red tides produced by this algal species.

[5] Phycodnaviridae cause death and lysis of freshwater and marine algal species, liberating organic carbon, nitrogen and phosphorus into the water, providing nutrients for the microbial loop.

At 3–4 p.i, virions are assembled in the cytoplasm, with the help of ATPase (a DNA packaging protein) and transported to the plasma membrane where they are released from the host via a budding mechanism.

Researchers have found that the production of viral sphingolipids produced during the lytic stage are involved in programmed cell death in coccolithophore populations.

The coccolithovirus possesses an Acute life strategy characterized by high reproduction and mutation rates and greater dependency on dense host populations for transmission.

The proteins translated from the early stage of transcription are involved in initiating viral DNA replication, occurring 60–90 minutes post infection.

[39] Members of the genus Prasinovirus infect small unicellular green algae in the order Mamiellales, commonly found in coastal marine waters.

[44] One of the most widely studied prasinoviruses, strain OtV5 whose genome is fully sequenced infects Ostreococcus tauri, the smallest free-living eukaryotes currently known.

[45] Prasinoviruses employ a nucleo-cytoplasmic replication strategy where virions adhere to the host-cell surface, followed by injection of DNA into the host cytoplasm.

Thomas et al. (2011) found that in resistant host cells, the viral genome was replicated and viruses were released via a budding mechanism.

[46] This low rate of viral release through budding allows for prolonged survivability of the host and virus progeny, resulting in a stable co-existence.

[45] The TFIID complex is necessary for transcription of eukaryotes, as it binds to the TATA box in the core promoter of the gene to initiate the assembly of RNA polymerase.

[29] Thirteen nucleotide metabolic enzymes have been found in PBCV-1, two of which include dUTP pyrophosphatase and dCMP deaminase, which can produce dUMP (i.e. the substrate for thymidylate synthetase).

[12][29] PBCV-1 also encodes a 187-amino-acid protein that resembles the Cu-Zn SOD with all of the conserved amino acid residues for binding copper and zinc, which can decompose the rapid accumulated superoxide in host cells during infection, thereby benefiting virus replication.

[62] These algal blooms can be extremely harmful to aquatic life, causing mortality in wild and cultured fish, such as salmon, yellowtail and sea bream.

The researchers found that HaV not only plays in important role in controlling biomass, but also influences the clonal composition or characteristics of H. akashiwo cells.

The authors suggest that viral infection, during the bloom termination period influences the properties of dominant cells in H. akashiwo populations.

[65] Selective pressure exerted by the viruses in the later stage of infection may promote genetic diversity, allowing the H. akashiwo population to thrive after bloom termination.

[citation needed] As mentioned, H. akashiwo blooms are detrimental to fish populations in temperate and subarctic waters, and continue to pose serious threats for aquaculture.

E. huxleyi has a global distribution from the tropics to subarctic waters and occasionally forms dense blooms which can cover 100,000s of square kilometers.

The researchers found that the concentrations of viruses were higher inside the 'high reflectance area', suggesting that virus-induced lysis of E. huxleyi cells resulted in coccolith detachment.

[citation needed] One of the best-studied phaeoviruses, EsV-1, infects the small, filamentous brown algae E. siliculosus, which has a cosmopolitan distribution (found in most of the world's oceans).

Using PCR amplification of a viral gene fragment, Muller et al. (2005) monitored levels of pathogen infection in Ectocarpus samples from the Gran Canaria Island, North Atlantic and southern Chile.

[citation needed] Members of the genus Chlorovirus are found in freshwater sources around the world and infect the green algae symbionts zoochlorellae.

Chloroviruses and viruses in general cause death and lysis of their hosts, releasing dissolved organic carbon, nitrogen and phosphorus into the water.

Chyrsochromulina, found in global fresh and marine waters, occasionally forms dense blooms which can produce harmful toxins, having negative effects on fisheries.

In oligotrophic environments, marine picophytoplankton account for up to 90% of the autotrophic biomass and thus are an important food source for nanoplanktonic and phagotrophic protists.

[79] Viruses such as OtV5, play important roles in regulating phytoplankton populations, and through lysis of cells contribute to the recycling of nutrients back towards other microorganisms, otherwise known as the viral shunt.

[43] On a larger scale, viral infection of M. pusilla is responsible for nutrient and energy recycling in aquatic food webs, which is yet to be quantified.