Deep chlorophyll maximum

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A deep chlorophyll maximum (DCM) is a subsurface maximum in the concentration of chlorophyll in the ocean or a lake. A DCM is not always present—sometimes there is more chlorophyll at the surface than at any greater depth—but it is a common feature of most aquatic ecosystems. The depth, thickness, intensity, composition, and persistence of DCM's vary widely.[1]

Location and formation[edit]

Throughout much of the tropical ocean, the DCM is a permanent structure, while in temperate and polar waters it is a more variable feature. In some cases, the DCM may coincide with a maximum in phytoplankton biomass; in others, it is made up of strongly shade-adapted cells, which contain a high ratio of chlorophyll to biomass, and is well separated vertically from the location of maximum biomass.[2]

In several studies, the DCM layer was found to be located in the thermocline, adjacent to the nutracline, at the bottom of the euphotic layer, where light attenuation ranges from ~1-2%[3][4] up to ~10% of that at the surface.[5] A DCM can also exist below the euphotic zone, where less than 1% of the surface light remains and little photosynthetic growth is possible; these layers are formed by subduction of surface waters, or sinking of cells.

Plankton community[edit]

The plankton community within the DCM is highly variable and diverse. One study in the western pacific gyre found over 223 major taxa, including alga, coccolithophorids, dinoflagellates, silicoflagellates, and diatoms.[6]

References[edit]

  1. ^ Cullen, JJ. (1982). "The Deep Chlorophyll Maximum: Comparing Vertical Profiles of Chlorophyll a". Canadian Journal of Fisheries and Aquatic Sciences. 39 (5): 791–803. doi:10.1139/f82-108. 
  2. ^ Miller, Charles B. (2004). Biological Oceanography. Blackwell Science Ltd. pp. 56–58. 
  3. ^ Veldhuis, MJC; Kraay, G.W. (1990). "Vertical distribution and pigment composition of a picoplanktonic prochlorophyte in the subtropical North Atlantic: A combined study of HPLC-analysis and flow cytometry". Mar. Ecol. Prog. Ser. 68: 121–127. doi:10.3354/meps068121. 
  4. ^ Kononen, K.; Hallfors, S.; Kokkonen, M.; Kuosa, H.; Laanemets, J.; Pavelson, J. (1998). "Development of a subsurface chlorophyll maximum at the entrance to the Gulf of Finland, Baltic Sea". Limnology Oceanography. 43: 1089–1106. doi:10.4319/lo.1998.43.6.1089. 
  5. ^ Mackey, D. J.; Parslow, J.; Higgins, H.W.; Griffith, F.B.; O'Sullivan, J.E. (1995). "Plankton productivity and biomass in the western equatorial Pacific:Biological and physical controls". Deep-Sea Research. 42: 499–533. doi:10.1016/0967-0645(95)00038-r. 
  6. ^ Furuya, Ken; Marumo, Ryuzo (1983). "The structure of the phytoplankton community in the subsurface chlorophyll maxima in the western North Pacific Ocean". Journal of Plankton Research. 5 (3): 393–406. doi:10.1093/plankt/5.3.393.