Pacific Ocean Red Tide

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Pacific ocean red tide is defined as a harmful algae bloom (HAB) that occurs in the warm, summer months[1] It is named for the ominous red color that becomes visible along the surface of the ocean. These blooms are not always harmful, but in some cases they can be lethal to marine organisms and humans[1]. Humans are not directly impacted by swimming in the contaminated water, but by consuming shellfish that is infected with the harmful microbes[1]. Red tide has been reported in every coastal state within the United States and its occurrence is increasing. This rise in occurrence is thought to be a result of climate change[1]. Studies have shown that phytoplankton blooms together with other microbes are responsible for the occurrence of HAB2. HAB occur when algae blooms sink to the bottom, die and are broken down by microbes. The result of these blooms is the depletion of aquatic oxygen resulting in a massive die off of fish[2].

Physical environment

Pacific Ocean Currents

The Pacific Ocean is considered an area of high productivity this is due to the event of upwelling. Upwelling is the process when winds carry deep, cold nutrient-rich water to the surface of the ocean[1]. The great strength of upwelling mixed with ocean currents makes for an area rich in microbial and organismal diversity[3]. Distribution of dinoflagellate cysts in surface sediments from the northeastern Pacific ocean in relation to sea-surface temperature, salinity, productivity and coastal upwelling. There are three currents off the Pacific coast that impact this mixing that takes place. The first is the California Current (CC), which carries cold, oxygen and nutrient rich water southward along the pacific coast[3]. The second is the California Undercurrent (UC), which originates from the eastern pacific near the equator and brings warm, saline, phosphate and oxygen poor water northward[3]. The final current is the Davidson Current (DC), which occurs in the fall and winter bringing current northward[3].

Microbial communities

Marine Dinoflagellates

Marine Dinoflagellates are a very old lineage of microorganisms that are present through out the world’s oceans and consist of many different strains[4]Of the strains existing today about twenty of them are known to be toxic, which results in the occurrence of red tide[4]. Planktonic toxic dinoflagellates can create a buildup of toxins in filter feeding marine life, which can negatively impact the consumers of these organisms[4]. In this case known consumers are birds, marine mammals and humans[4]. These toxic species can also negatively impact fish communities either through the consumption of phytoplankton, the absorption of microbes or indirectly through the depletion of oxygen in the water[4]. Toxic dinoflagellates belong to eleven different genera (‘’Gonyaulax, Protogonyaulax, Dinophysis, Prorocentrum, Pyrodinium, Gymnodinium, Gambierdiscus, Ostreopsis, Ptychodiscus, Amphidinium and Gyrodinium’’)[4]. All species are thought to be morphologically similar but are genetically different[4].

Important Microbial Interactions

Phytoplankton and algae are main contributors to the world’s oxygen supply. They are primary producers that are at the core of the global food web. Without them the fixation of carbon dioxide and the creation of oxygen via photosynthesis would not be possible. The production of oxygen allows for the creation of organic matter, which is a factor that helps to establish some marine life. Occasionally, algal blooms result in the creation of too many of these organisms, which results in the occurrence of red tide[5]. The over production of these organisms can have a negative impact on organisms higher up in the food chain such as fish, marine mammals, shellfish and humans.

Microbial processes

Toxin production

In the past little has been known about why or how certain species of marine dinoflagellates produce toxins. Recently it has been shown that a specific species of dinoflagellate present in the Gulf of Mexico (‘’Karenia brevis’’) produces toxin during times of osmotic stress. These toxins are stored inside the cell and are released during cell death[6]. As algal blooms age cells start to die off consequentially a buildup of toxins occurs outside of the cell[6]. It is still not clear how the production of toxin is useful to the dinoflagellates. It is thought that toxin production decreases grazing pressures or helps to limit species competition[6] In the future toxin production is expected to increase due to changes in ocean climate [6].


Eutrophication is the process by which excess plant and algal growth occur due to the increase of certain limiting factors, including in this case nitrogen fertilizer, runoff and sewage[7]. This process is known to occur naturally over time but human activities have increased this[7]. Red tide is associated with the increase of excessive algal growth due to the increase in abundance of limiting factors such as Nitrogen and Phosphorous[8].


Algae and phytoplankton are major contributors to the global oxygen supply. They are primary producers that fix carbon dioxide into oxygen. This is a key process that helps to establish the marine community.

Current Research

Progress in understanding harmful algal blooms

Anderson ‘’et al. ‘’discussed current research on the impact of HABs on public health, fisheries, tourism and ecosystem[9]. This study has lead to the establishment of new management ideas for the future[9]. This study has also established new knowledge about different genetic data that can better help with understanding this spreading phenomenon[9]. In particular this research looked into the ecological and genetic basis for the production of toxins that occur during red tide[9].

Global change and the future of harmful algal blooms in the ocean

Fu ‘’et al.’’ discussed current research on how climate change impacts the amount of HABs[10]. In particular, it discussed how ocean acidification could ultimately lead to the increase of HAB[10]. It also discussed how this will affect overall microbial community composition in the future[10].

Vulnerability of coastal ecosystems to changes in harmful algal bloom distribution in response to climate change

Gilbert discussed current research on how future projections show increased vulnerability for coastal ecosystems to HAB[11]. It is thought that HAB will occur more readily because of more suitable environmental conditions caused by climate change[11]. Specifically, this study stated that difference species relating to HAB could increase in location in the future[11].


  1. 1.0 1.1 1.2 1.3 1.4 Cite error: Invalid <ref> tag; name "first" defined multiple times with different content Cite error: Invalid <ref> tag; name "first" defined multiple times with different content Cite error: Invalid <ref> tag; name "first" defined multiple times with different content
  2. S.J. Bien. 1954. A study of certain chromogenic bacteria isolated from “red tide” water with a description of a new species. ‘’Bulletin of marine science’’ 4(2):110-119
  3. 3.0 3.1 3.2 3.3 V.Pospelova, Vernal, A.D. and Pedersen, T.F. 2008
  4. 4.0 4.1 4.2 4.3 4.4 4.5 4.6 K.A. Steidinger and Baden, D.G. 1984. Toxic Marine Dinoflagellates. Bureau of Marine research Florida department of natural resources.
  5. [D. Karl et al. 1997. The role of nitrogen fixation in biogeochemical cycling in the subtropical north pacific ocean. ‘’Nature‘’388: 533-538
  6. 6.0 6.1 6.2 6.3 R.M. Errera and Campbell, L. 2011. Osmotic stress triggers toxin production by the dinoflagellate Karenia brevis. ‘’PNAS’’. 108(26): 10597-10601
  7. 7.0 7.1 M.F. Chislock , Doster, E., Zitomer, R.A. and Wilson, A.E. 2013. Eutrophication: Causes, Consequences and Controls in aquatic ecosystems. ‘’Nature Education Knowledge’’ 4(4):10
  8. J. Heilser et al. 2008. Euthrophication and harmful algal blooms: a scientific consensus. ‘’Harmful algae’’ 8(1): 3-13
  9. 9.0 9.1 9.2 9.3 D.M. Anderson, Cembella, A.D. and Hallegraeff, G.M. 2012. Progress in understanding harmful algal blooms: paradigm shifts and new technologies for research, monitoring and management. ‘’Annual review of marine science’’ 4:143-176
  10. 10.0 10.1 10.2 F.X. Fu, Tatters, A.O. and Hutchins, D.A. 2012. Global change and the future of harmful algal blooms in the ocean. ‘’Marine ecology progress series’’ 470:207-233
  11. 11.0 11.1 11.2 P.M. Glibert. 2014. Vulnerability of coastal ecosystems to changes in harmful algal bloom distribution in response to climate change: projections based on model analysis. ‘’Global change biology’’ 20(12):3845-3858

Edited by <Nina Mullin>, a student of Mary Beth Leigh at the University of Alaska Fairbanks Template adapted from one used by Angela Kent at the University of Illinois at Urbana-Champaign.

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