Deep chlorophyll maximum

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The deep chlorophyll maximum (DCM), also called the subsurface chlorophyll maximum, [1] [2] is the region below the surface of water with the maximum concentration of chlorophyll. The DCM generally exists at the same depth as the nutricline, the region of the ocean where the greatest change in the nutrient concentration occurs with depth. [3]

Contents

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, especially in regions of strong thermal stratification. [4] The depth, thickness, intensity, composition, and persistence of DCMs vary widely. [2] [5]

A common way of determining the DCM is through the use of a CTD rosette, an underwater instrument that measures various parameters of water at specific depths. [4] The location and formation of the DCM depends on multiple factors, such as the resident organisms' nutritional needs and light availability. Some organisms have adapted to lower levels of light through increasing its cellular chlorophyll amounts, [6] and others have adapted by migrating vertically with varying nutrient and light levels. [7] The DCM species composition vary with water chemistry, location, seasonality, and depth. [3] [8] Not only is there a difference in DCM species composition between oceans and lakes, variation is also present within different oceans and lakes. Because the DCM holds much of the world's primary productivity, it plays a significant role in nutrient cycling, [9] the flow of energy, and biogeochemical cycles. [10]

Measurements

Fig. 1 Field photo of a CTD rosette, which measures the conductivity, temperature, and pressure of water samples. Ctd hg.jpg
Fig. 1 Field photo of a CTD rosette, which measures the conductivity, temperature, and pressure of water samples.

The DCM is often located tens of meters below the surface, and cannot be observed by using traditional satellite remote sensing methods. Estimates of primary productivity are often made via these remote sensing methods coupled with statistical models, though these statistical calculations may not have accurately included production in the DCM. [11] The DCM of a study area can be determined in-situ through the use of an underwater instrument (CTD rosette with niskin bottles) to measure various parameters such as salinity (including dissolved nutrients), temperature, pressure, and chlorophyll fluorescence. Collected water samples can be used to determine phytoplankton cell counts. These measurements can then be converted into chlorophyll concentrations, phytoplankton biomass, and phytoplankton productivity. [4] Another way to estimate primary productivity in the DCM is to create a simulation of the DCM formation in a region by making a 3D model of the region. This can be done if sufficient hydrodynamic and biogeochemical data exists for that ocean region. [11]

Location and formation

Since its initial discovery, oceanographers have presented various theories to explain the formation of deep chlorophyll maxima.

Abiotic factors

In-situ studies have determined that the depth of DCM formation is primarily dependent on light attenuation levels, and the depth of the nutricline, [7] although thermal stratification also plays a role. [10] [11] In lakes, the thickness of the DCM layer is mainly controlled by the sizes and maximum depths of lakes. [10]

The DCM forms near the nutricline and the bottom of the photic zone. [3] Phytoplankton growth in the DCM is limited by both nutrient and light availability, therefore either increased nutrient input, or increased light availability to the DCM can in turn increase the phytoplankton growth rate. [7]

The location and formation of the DCM also depends on season. In the Mediterranean Sea, the DCM is present in the summer due to water stratification, and is rare in the winter due to deep mixing. [11] The DCM can be present at shallower depths in the winter and early spring due to light limitation and higher nutrient availability in shallower regions due to mixing, and at lower depths during the summer and early fall as nutrients in the surface water are depleted by primary producers and stronger irradiance allows light to penetrate to greater depths. [7] [11]

The vertical mixing of limiting nutrients across the thermocline is a key process in supporting the deep water chlorophyll maximum. This mixing can be driven by a number of processes linked to wind driven oscillations, [12] [13] [14] internal tides [15] and entrainment through the deepening of the surface mixed layer. [16] In shallow seasonally stratified seas boundary layer processes can also drive mixing of limiting nutrients across the thermocline. [17]

Biotic factors

The formation of a DCM correlates with a number of biological processes, [6] affecting nutrient cycling for local heterotrophic bacteria [9] and composition of specialized phytoplankton. [2] [8] [18] [19]

Adaptations to light levels

Fig. 2. Example of the level of chlorophyll fluorescence at different water depths. Chlorophyll maximum.png
Fig. 2. Example of the level of chlorophyll fluorescence at different water depths.

Light attenuation factors have been shown to be quite predictive of the DCM depth, since the phytoplankton present in the region require sufficient sunlight for growth, [4] resulting in a DCM that is generally found in the euphotic zone. However, if the phytoplankton population has adapted to lower light environments, the DCM can also be located in the aphotic zone. [7] [20] The high chlorophyll concentration at the DCM is due to the high number of phytoplankton that have adapted to functioning in low light conditions. [2] [6] [9]

To adapt to low light conditions, some phytoplankton populations have been found to have increased amounts of chlorophyll counts per cell, [2] [18] [19] which contributes to the formation of the DCM. [3] Rather than an increase of overall cell numbers, seasonal light limitation or low irradiance levels can raise the individual cellular chlorophyll content. [6] [18] As depth increases within the mixing zone, phytoplankton must rely on having higher pigment counts (chlorophyll) to capture photic energy. Due to the higher concentration of chlorophyll in the phytoplankton present, the DCM does not predict the depth of the biomass maximum in the same region. [18]

In addition, compared to shallower regions of the mixing zone, the DCM has high nutrient concentrations and/or lower respiratory, grazing, and death rates which further promote phytoplankton cell production. [21]

Vertical migration

Vertical migration, or movement of phytoplankton within the water column, contributes to the establishment of the DCM due to the diversity of resources required by the phytoplankton. Dependent on factors like nutrients and available light, some phytoplankton species will intentionally move to different depths to fulfill their physiological requirements. [7] A mechanism employed by certain phytoplankton, such as certain species of diatoms and cyanobacteria, is to regulate their own buoyancy to move through the water column. Other species such as dinoflagellates use their flagella to swim to their desired depth. This intentional movement of phytoplankton contributes to the formation of the DCM in areas where these species make up a significant proportion of the phytoplankton community. Generally these species are larger in size and are not found in significant abundance in nutrient poor regions, so these physiological aspects of phytoplankton contribute less to DCM formation in oligotrophic waters. [7]

In lakes, the thickness of the DCM shows positive correlations with lake sizes. However, due to the great diversity of lakes, there is no constant factor for light and temperature that can be utilized to predict DCM depths across different lake types. [10]

Composition

The composition of microorganisms present in the DCM varies significantly with geographical location, season, and depth. [3] [8]

The species of phytoplankton present in the DCM varies with depth due to varying accessory pigmentation. Some phytoplankton species have accessory pigments, compounds that have adapted them to gather light energy from certain wavelengths of light, [8] even in areas of low light penetration. [2] [9] To optimize light energy collection, phytoplankton will move to specific depths to access different wavelengths of visible light. [22]

The difference in phytoplankton composition between the epilimnion layer and the DCM are consistent throughout several bodies of water. The DCM tends to harbour more flagellated organisms and cryptophytes, [23] [24] whereas the epilimnion layer tends to have a larger centric diatom abundance. [25]

Oceans

In the Northwestern Mediterranean, the most abundant phytoplankton present are coccolithophorids, flagellates, and dinoflagellates. The Southeastern Mediterranean has a similar composition, where coccolithophorids and monads (nano- and picoplankton) make up the majority of the phytoplankton community in the DCM. [23]

In the Indian Ocean, the most abundant phytoplankton present in the DCM are cyanobacteria, prochlorophytes, coccolithophorids, dinoflagellates and diatoms. [8]

In the North Sea, dinoflagellates are the main phytoplankton species present in the DCM at and below the pycnocline. In shallower parts of the DCM - above the pycnocline, dinoflagellates are also present, as well as nanoflagellates. [4]

Lakes

Lake Superior

The DCM of clear, stratified water is commonly found below the epilimnion. [25] Lake Superior is one of the world's largest freshwater lakes, and in the summer, its DCM ranges from approximately 20 m to 35 m [25] [26] below the surface. Although the epilimnion and DCM are neighbouring layers of water, the species composition of the epilimnion and the DCM differ almost entirely. [25] These differences include the presence of less centric diatoms, more pennate diatoms, cryptophytes, and pyrrophytes at the DCM compared to the epilimnion layer. Additionally, the most significant difference in between these two layers is the abundance of Cyclotella comta, which occurs much less in the DCM. [25]

Much more of the DCM community are flagellated (e.g. cryptophytes and pyrrophytes) compared to those of the epilimnion. [25] As flagellated species are better swimmers, this could explain how they are able to reside at their desired depth, the DCM. [25] Another factor for the development of the DCM is nutrient availability. It has been found that the DCM had a lower ratio of particulate organic carbon (POC) to phosphorus (P) than the epilimnion. [25] Since phosphorus is one of the limiting factors for growth, [27] [28] especially in Lake Superior during stratified times, [29] this phenomenon may indicate that phytoplankton in the DCM is more enriched with phosphorus than in the epilimnion. The higher availability of phosphorus may have allowed more phytoplankton to prefer the DCM even with the lower amount of light compared to the epilimnion. [25] On the other hand, the fact that the DCM has lower light availability could be used to argue that the lower POC:P ratio is due to light limitation rather than increased nutrient (P) concentrations. [25] [30]

Lake Tahoe

In Lake Tahoe, the DCM is unique, as the depth of the region is much lower than normal, present at around 90-110 metres below the surface. [21] [20] Typically, DCM's are found closely below the thermocline, which is present at around 30-40 metres. [5] [20] Lake Tahoe represents a chlorophyll gradient similar to that of oligotrophic areas, [21] such that the depth of the region is dependent on seasonal fluctuations. Due to these temporal shifts, especially between spring and summer, Lake Tahoe's phytoplankton communities undergo distinct changes. During the spring months, the DCM coincides with the upper surface of the nitracline, [21] [31] making the water nutrient-rich for diatoms Cyclotella striata and chrysophytes Dinobryon bavaricum to thrive in. During the summer months, the DCM deepens, and productivity within the layer almost becomes entirely light dependent. [31] Similar to the chlorophyll structures found in oceans, [5] the DCM becomes incredibly fluid and variable, such that certain phytoplankton species (diatoms Synedra ulna, Cyclotella comta and green flagellates) begin to dominate, despite being absent during the spring productivity period. [21] [31]

Overall, the phytoplankton community between the epilimnion and the DCM in Lake Tahoe differ with size. Both regions are abundant with diatoms; small diatoms (cell volume = 30.5μm³) such as Cyclotella stelligera, Synedra radians make up the majority in the epilimnion, while larger diatoms (cell volume = 416.3μm³) such as C.ocellata, Stephanodiscus alpinus, Fragilaria crotonensis, dominate the DCM. [21]

Lakes of the North Patagonian Andean Region

Lakes of the North Patagonian Andean Region can be divided into larger deeper lakes and smaller shallow lakes. Although these lakes are found in the same region, they exhibit different conditions leading to varying DCM species compositions. The large deep lakes are ultra-oligotrophic, as they are very transparent and contain low DOC and nutrients. [32] Unlike the homogenous thermal profile of the shallower lakes, deeper lakes undergo strong thermal stratification during the late spring and summer. The two lake types also differ in light attenuation coefficients: it is lower in the transparent deeper lakes, which means more light is able to penetrate though. [32]

As such, the main difference between the two lake types that was found to contribute to the DCM community is the light climate. Shallow lakes were found to contain greater concentrations of dissolved yellow particles than the deeper lakes. As a result, for deeper lakes, maximum absorption wavelengths were mainly at the red end of the spectra, whereas shallow lakes exhibited green and blue absorption wavelengths in addition to red. [32]

At the DCM region of the large deep lakes, the mixotrophic ciliate Ophrydium naumanni were dominant. Their phototrophic abilities come from their endosymbiotic algae Chlorella , which are strong competitors in poor light conditions. [32] In addition, the ciliates can undergo phagotrophy to obtain other necessary elements. In shallower lakes, O. naumanni were found to be absent, likely due to higher levels of competition with phytoplankton and turbulence intensity. [32]

Ecological implications

The DCM plays an important ecological role in harbouring much of the world's primary production, and in nutrient cycling. In oligotrophic waters, like the North Sea and the Mediterranean Sea, the DCM is where over half of the overall primary production occurs due to phytoplankton growth. [4] [11] The high rate of primary production in the DCM facilitates nutrient cycling to higher trophic levels in the mixed layer. The DCM forms at the same depth as the nuricline, [3] so phytoplankton in the DCM can access nutrients coming up from the deep ocean. The phytoplankton in the DCM can then cycle back up the water column providing nutrients for heterotrophs in the mixed layer. [7] [9]

Since the DCM environment plays a fundamental role in primary productivity, it can be associated with many aspects of aquatic predator-prey interactions, energy and biomass flow, and biogeochemical cycles. [10] Significant export of organic material from the water column occurs due to the DCM, as heterotrophs consume phytoplankton in the DCM and the fecal matter of grazers sinks to the deep ocean. [8] The DCM is an important food source for secondary producers as it has a relatively high concentration of primary producers at one region of the water column. This makes it easier and faster for grazers to find and consume phytoplankton which in turn increases the rate of movement of energy through the trophic levels. [11]

Related Research Articles

The photic zone is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological processes that supply nutrients into the upper water column. The photic zone is home to the majority of aquatic life due to the activity of the phytoplankton. The thicknesses of the photic and euphotic zones vary with the intensity of sunlight as a function of season and latitude and with the degree of water turbidity. The bottommost, or aphotic, zone is the region of perpetual darkness that lies beneath the photic zone and includes most of the ocean waters.

<span class="mw-page-title-main">Algal bloom</span> Spread of planktonic algae in water

An algal bloom or algae bloom is a rapid increase or accumulation in the population of algae in freshwater or marine water systems. It is often recognized by the discoloration in the water from the algae's pigments. The term algae encompasses many types of aquatic photosynthetic organisms, both macroscopic multicellular organisms like seaweed and microscopic unicellular organisms like cyanobacteria. Algal bloom commonly refers to the rapid growth of microscopic unicellular algae, not macroscopic algae. An example of a macroscopic algal bloom is a kelp forest.

<span class="mw-page-title-main">Biological pump</span> Carbon capture process in oceans

The biological pump (or ocean carbon biological pump or marine biological carbon pump) is the ocean's biologically driven sequestration of carbon from the atmosphere and land runoff to the ocean interior and seafloor sediments. In other words, it is a biologically mediated process which results in the sequestering of carbon in the deep ocean away from the atmosphere and the land. The biological pump is the biological component of the "marine carbon pump" which contains both a physical and biological component. It is the part of the broader oceanic carbon cycle responsible for the cycling of organic matter formed mainly by phytoplankton during photosynthesis (soft-tissue pump), as well as the cycling of calcium carbonate (CaCO3) formed into shells by certain organisms such as plankton and mollusks (carbonate pump).

<span class="mw-page-title-main">Hypolimnion</span> Bottom layer of water in a thermally-stratified lake

The hypolimnion or under lake is the dense, bottom layer of water in a thermally-stratified lake. The word "hypolimnion" is derived from Ancient Greek: λιμνίον, romanized: limníon, lit. 'lake'. It is the layer that lies below the thermocline.

<span class="mw-page-title-main">Spring bloom</span> Strong increase in phytoplankton abundance that typically occurs in the early spring

The spring bloom is a strong increase in phytoplankton abundance that typically occurs in the early spring and lasts until late spring or early summer. This seasonal event is characteristic of temperate North Atlantic, sub-polar, and coastal waters. Phytoplankton blooms occur when growth exceeds losses, however there is no universally accepted definition of the magnitude of change or the threshold of abundance that constitutes a bloom. The magnitude, spatial extent and duration of a bloom depends on a variety of abiotic and biotic factors. Abiotic factors include light availability, nutrients, temperature, and physical processes that influence light availability, and biotic factors include grazing, viral lysis, and phytoplankton physiology. The factors that lead to bloom initiation are still actively debated.

<span class="mw-page-title-main">Lake stratification</span> Separation of water in a lake into distinct layers

Lake stratification is the tendency of lakes to form separate and distinct thermal layers during warm weather. Typically stratified lakes show three distinct layers: the epilimnion, comprising the top warm layer; the thermocline, the middle layer, whose depth may change throughout the day; and the colder hypolimnion, extending to the floor of the lake.

High-nutrient, low-chlorophyll (HNLC) regions are regions of the ocean where the abundance of phytoplankton is low and fairly constant despite the availability of macronutrients. Phytoplankton rely on a suite of nutrients for cellular function. Macronutrients are generally available in higher quantities in surface ocean waters, and are the typical components of common garden fertilizers. Micronutrients are generally available in lower quantities and include trace metals. Macronutrients are typically available in millimolar concentrations, while micronutrients are generally available in micro- to nanomolar concentrations. In general, nitrogen tends to be a limiting ocean nutrient, but in HNLC regions it is never significantly depleted. Instead, these regions tend to be limited by low concentrations of metabolizable iron. Iron is a critical phytoplankton micronutrient necessary for enzyme catalysis and electron transport.

<span class="mw-page-title-main">Critical depth</span> Hypothesized depth at which phytoplankton growth is matched by losses

In biological oceanography, critical depth is defined as a hypothetical surface mixing depth where phytoplankton growth is precisely matched by losses of phytoplankton biomass within the depth interval. This concept is useful for understanding the initiation of phytoplankton blooms.

<span class="mw-page-title-main">Mixed layer</span> Layer in which active turbulence has homogenized some range of depths

The oceanic or limnological mixed layer is a layer in which active turbulence has homogenized some range of depths. The surface mixed layer is a layer where this turbulence is generated by winds, surface heat fluxes, or processes such as evaporation or sea ice formation which result in an increase in salinity. The atmospheric mixed layer is a zone having nearly constant potential temperature and specific humidity with height. The depth of the atmospheric mixed layer is known as the mixing height. Turbulence typically plays a role in the formation of fluid mixed layers.

<span class="mw-page-title-main">Diel vertical migration</span> A pattern of daily vertical movement characteristic of many aquatic species

Diel vertical migration (DVM), also known as diurnal vertical migration, is a pattern of movement used by some organisms, such as copepods, living in the ocean and in lakes. The adjective "diel" comes from Latin: diēs, lit. 'day', and refers to a 24-hour period. The migration occurs when organisms move up to the uppermost layer of the water at night and return to the bottom of the daylight zone of the oceans or to the dense, bottom layer of lakes during the day. DVM is important to the functioning of deep-sea food webs and the biologically-driven sequestration of carbon.

Monomictic lakes are holomictic lakes that mix from top to bottom during one mixing period each year. Monomictic lakes may be subdivided into cold and warm types.

<span class="mw-page-title-main">Langmuir circulation</span> Series of shallow, slow, counter-rotating vortices at the oceans surface aligned with the wind

In physical oceanography, Langmuir circulation consists of a series of shallow, slow, counter-rotating vortices at the ocean's surface aligned with the wind. These circulations are developed when wind blows steadily over the sea surface. Irving Langmuir discovered this phenomenon after observing windrows of seaweed in the Sargasso Sea in 1927. Langmuir circulations circulate within the mixed layer; however, it is not yet so clear how strongly they can cause mixing at the base of the mixed layer.

<span class="mw-page-title-main">Trophic state index</span> Measure of the ability of water to sustain biological productivity

The Trophic State Index (TSI) is a classification system designed to rate water bodies based on the amount of biological productivity they sustain. Although the term "trophic index" is commonly applied to lakes, any surface water body may be indexed.

<span class="mw-page-title-main">Ecosystem of the North Pacific Subtropical Gyre</span> Major circulating ecosystem of ocean currents

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<span class="mw-page-title-main">Haida Eddies</span>

Haida Eddies are episodic, clockwise rotating ocean eddies that form during the winter off the west coast of British Columbia's Haida Gwaii and Alaska's Alexander Archipelago. These eddies are notable for their large size, persistence, and frequent recurrence. Rivers flowing off the North American continent supply the continental shelf in the Hecate Strait with warmer, fresher, and nutrient-enriched water. Haida eddies are formed every winter when this rapid outflow of water through the strait wraps around Cape St. James at the southern tip of Haida Gwaii, and meets with the cooler waters of the Alaska Current. This forms a series of plumes which can merge into large eddies that are shed into the northeast Pacific Ocean by late winter, and may persist for up to two years.

Freshwater phytoplankton is the phytoplankton occurring in freshwater ecosystems. It can be distinguished between limnoplankton, heleoplankton, and potamoplankton. They differ in size as the environment around them changes. They are affected negatively by the change in salinity in the water.

<span class="mw-page-title-main">Viral shunt</span>

The viral shunt is a mechanism that prevents marine microbial particulate organic matter (POM) from migrating up trophic levels by recycling them into dissolved organic matter (DOM), which can be readily taken up by microorganisms. The DOM recycled by the viral shunt pathway is comparable to the amount generated by the other main sources of marine DOM.

<span class="mw-page-title-main">Lake metabolism</span> The balance between production and consumption of organic matter in lakes

Lake metabolism represents a lake's balance between carbon fixation and biological carbon oxidation. Whole-lake metabolism includes the carbon fixation and oxidation from all organism within the lake, from bacteria to fishes, and is typically estimated by measuring changes in dissolved oxygen or carbon dioxide throughout the day.

Low-nutrient, low-chlorophyll (LNLC)regions are aquatic zones that are low in nutrients and consequently have low rate of primary production, as indicated by low chlorophyll concentrations. These regions can be described as oligotrophic, and about 75% of the world's oceans encompass LNLC regions. A majority of LNLC regions are associated with subtropical gyres but are also present in areas of the Mediterranean Sea, and some inland lakes. Physical processes limit nutrient availability in LNLC regions, which favors nutrient recycling in the photic zone and selects for smaller phytoplankton species. LNLC regions are generally not found near coasts, owing to the fact that coastal areas receive more nutrients from terrestrial sources and upwelling. In marine systems, seasonal and decadal variability of primary productivity in LNLC regions is driven in part by large-scale climatic regimes leading to important effects on the global carbon cycle and the oceanic carbon cycle.

<span class="mw-page-title-main">Water clarity</span> How deeply visible light penetrates through water

Water clarity is a descriptive term for how deeply visible light penetrates through water. In addition to light penetration, the term water clarity is also often used to describe underwater visibility. Water clarity is one way that humans measure water quality, along with oxygen concentration and the presence or absence of pollutants and algal blooms.

References

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  20. 1 2 3 Kiefer, Dale A.; Holm-Hansen, Osmund; Goldman, Charles R.; Richards, Robert; Berman, Thomas (May 1972). "Phytoplankton in Lake Tahoe: Deep-Living Populations1". Limnology and Oceanography. 17 (3): 418–422. Bibcode:1972LimOc..17..418K. doi: 10.4319/lo.1972.17.3.0418 . ISSN   0024-3590.
  21. 1 2 3 4 5 6 Coon, Thomas G.; Lopez, Matilde M.; Richerson, Peter J.; Powell, Thomas M.; Goldman, Charles R. (1987). "Summer dynamics of the deep chlorophyll maximum in Lake Tahoe". Journal of Plankton Research. 9 (2): 327–344. doi:10.1093/plankt/9.2.327. ISSN   0142-7873.
  22. ↑ "Light in the Ocean | manoa.hawaii.edu/ExploringOurFluidEarth". manoa.hawaii.edu. Retrieved 2018-10-28.
  23. 1 2 Kimor, B.; Berman, T.; Schneller, A. (1987). "Phytoplankton assemblages in the deep chlorophyll maximum layers off the Mediterranean coast of Israel". Journal of Plankton Research. 9 (3): 433–443. doi:10.1093/plankt/9.3.433. ISSN   0142-7873.
  24. ↑ Antonio, Camacho (2006). On the occurrence and ecological features of deep chlorophyll maxima (DCM) in Spanish stratified lakes. Asociación Española de Limnología. OCLC   784331078.
  25. 1 2 3 4 5 6 7 8 9 10 Barbiero, Richard P.; Tuchman, Marc L. (2004-09-01). "The Deep Chlorophyll Maximum in Lake Superior". Journal of Great Lakes Research. 30: 256–268. Bibcode:2004JGLR...30..256B. CiteSeerX   10.1.1.502.2180 . doi:10.1016/s0380-1330(04)70390-1. ISSN   0380-1330.
  26. ↑ Fahnenstiel, Gary L.; Glime, Janice (1983). "Subsurface Chlorophyll Maximum and AssociatedCyclotella Pulse in Lake Superior". Internationale Revue der Gesamten Hydrobiologie und Hydrographie. 68 (5): 605–616. doi:10.1002/iroh.3510680502. ISSN   0020-9309.
  27. ↑ Ivanikova, Natalia V.; Popels, Linda C.; McKay, R. Michael L.; Bullerjahn, George S. (2007-06-15). "Lake Superior Supports Novel Clusters of Cyanobacterial Picoplankton". Appl. Environ. Microbiol. 73 (12): 4055–4065. Bibcode:2007ApEnM..73.4055I. doi:10.1128/AEM.00214-07. ISSN   0099-2240. PMC   1932735 . PMID   17468271.
  28. ↑ Brembu, Tore; Mühlroth, Alice; Alipanah, Leila; Bones, Atle M. (2017-09-05). "The effects of phosphorus limitation on carbon metabolism in diatoms". Phil. Trans. R. Soc. B. 372 (1728): 20160406. doi:10.1098/rstb.2016.0406. ISSN   0962-8436. PMC   5516115 . PMID   28717016.
  29. ↑ Guildford, Stephanie J.; Hecky, Robert E. (2000-09-12). "Total nitrogen, total phosphorus, and nutrient limitation in lakes and oceans: Is there a common relationship?". Limnology and Oceanography. 45 (6): 1213–1223. Bibcode:2000LimOc..45.1213G. doi: 10.4319/lo.2000.45.6.1213 . ISSN   0024-3590.
  30. ↑ Nalewajko, C.; Lee, K.; Shear, H. (1980-09-26). "Phosphorus Kinetics in Lake Superior: Light Intensity and Phosphate Uptake in Algae". Canadian Journal of Fisheries and Aquatic Sciences. 38 (2): 224–232. doi:10.1139/f81-029. ISSN   0706-652X.
  31. 1 2 3 R., Abbott, Mark R. Denman, Kenneth L. Powell, Thomas M. Richerson, Peter J. Richards, Robert C. Goldman, Charles (2009-09-28). Mixing and the dynamics of the deep chlorophyll maximum in Lake Tahoe. American Society of Limnology and Oceanography. OCLC   651036421.{{cite book}}: CS1 maint: multiple names: authors list (link)
  32. 1 2 3 4 5 Perez, G. L. (2002-06-01). "Light climate and plankton in the deep chlorophyll maxima in North Patagonian Andean lakes". Journal of Plankton Research. 24 (6): 591–599. doi: 10.1093/plankt/24.6.591 . ISSN   1464-3774.
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