Nutrient chemistry of the water column of Lake Tanganyika

Edmond, John M.; Stallard, Robert F.; Craig, H.; Craig, Valerie; Weiss, Ray F.; Coulter, G. W.

doi:10.4319/lo.1993.38.4.0725

Cited by 70 publications

(87 citation statements)

References 16 publications

(21 reference statements)

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“…Lake Kivu, Lake Malawi, and shallow Lake Kyoga (Table 6) were severely P deficient, while Lake George would be considered severely deficient in both N and P. Viner (1973) found rapid uptake in the dark of phosphate and ammonium added to samples of water from Lake George and concluded that both elements could control phytoplankton growth in the lake. There are no particulate analyses for Lake Tanganyika, but Edmond et al (1993) found that inorganic fixed N and phosphate were regenerated in near-Redfield proportions.…”

Section: Discussionmentioning

confidence: 99%

The stoichiometry of carbon, nitrogen, and phosphorus in particulate matter of lakes and oceans

Hecky¹,

Campbell²,

Hendzel³

1993

Limnology & Oceanography

545

345

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The mean carbon, nitrogen, and phosphorus contents of particulate material for 5 1 lakes or lake basins, extending from arctic to tropical climatic regions, including small lakes as well as the largest lakes in the world, indicate that Redfield ratios are the exception rather than the rule in freshwater. The C: P and N : P ratios are more variable for lake particles but generally higher than marine particles, and the mean molar C: N, C: P, and N : P ratios are substantially higher than the Redfield ratio of 106 : 16: 1. On average, lower C : N, C : P, and N : P ratios occur in subarctic lakes while higher ratios occur in the tropics and in temperate, oligotrophic lakes on the Canadian Shield. In shield lakes with long residence times (>6 months) the high ratios of C : N, C : P, and N : P do not originate from streamborne or atmospherically deposited particles but arise from in-lake processes. Regression analysis demonstrates that small lakes are generally more N and P deficient than large lakes. In freshwaters, particulate composition ratios imply that a wide variety of conditions exists in lakes, including N and P deficiency, as well as N and P sufficiency. In the Experimental Lakes Area of Canada, independent physiological nutrient status indicators generally agree with the status indicated by seston ratios. The relative uniformity of marine C : N : P composition (compared to lakes) at the Redfield ratio suggests that marine plankton cannot be as severely, or as frequently, limited by N and P as lake plankton. Consequently, the paradigm of N limitation in the oceans requires qualification.Based on particulate comDosition, it is more correct to say that ocean plankton is noi as N grid P deficient as lake-plankton.The composition of marine particulate matter is relatively uniform. Redfield (1934Redfield ( , 1958 noted the near constancy of the ratio of C : N : P in marine plankton and the similarity of the N : P ratio of plankton to the oceanic deepwater ratio of nitrate to phosphate. As early as 1940, the C : N : P molar composition ratio of marine plankton was accepted to be 106 : 16 : 1 (Redfield et al. 1963); this ratio is now referred to as the Redfield ratio. The ratio has withstood the test of time, and the ever-growing number of analyses of marine particles and nutrient regeneration profiles, with relatively AcknowledgmentsWe thank G. J. Bumskill and H. E. Welch for permission to publish particulate C, N, and P data on Lake Winnipeg and the Saqvaqjuac lakes, respectively. Dana Cruikshank and his field assistants sampled the ELA lakes for us.

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Section: Discussionmentioning

confidence: 99%

The stoichiometry of carbon, nitrogen, and phosphorus in particulate matter of lakes and oceans

Hecky¹,

Campbell²,

Hendzel³

1993

Limnology & Oceanography

545

345

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“…1), one in the north and one in the south, each of which is over 1300 m deep. The lake is meromictic (i.e., seasonal mixing affects only the upper layers, while below 100-200 m in depth the lake water is permanently anoxic and relatively rich in nutrients) (Hecky et al 1991;Edmond et al 1993). Vertical exchange and especially upwelling driven by southeast trade winds provide the prime nutrient source to sustain primary production by internal nutrient loading .…”

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confidence: 99%

The physics of the warming of Lake Tanganyika by climate change

Verburga

Hecky

2009

Limnology & Oceanography

124

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Climate warming over the 20th century has increased the density stratification and stability of Lake Tanganyika, a deep rift valley lake. Here we examine the physical processes involved in and affected by the warming of the lake, and we discuss effects on lake productivity. The rate of net heat absorption by Lake Tanganyika has been 0.4 W m 22 since 1913, twice the rate in the global ocean, indicating stronger climate forcing in the East African region. Lakes warm through increased incoming long-wave radiation. While lakes in general will increase heat outputs in a warming climate, heat outputs will increase more slowly in deeper lakes than in shallower lakes. Temperatures have increased by 0.2uC at 1000 m in depth, in part because of reduced cool marginal inflows, while water surface temperatures have increased by about 1.3uC. This differential heating over depth has increased the density gradient through the water column, reducing the potential for vertical mixing and thereby limiting nutrient fluxes to the phototrophic zone. An increase in transparency, indicating a reduction in productivity as a result of the reduced vertical mixing, occurred both in Lake Tanganyika and in Lake Malawi, a similar deep tropical lake in which warming has also been documented.

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“…N limitation has been inferred from low dissolved inorganic N : P (Coulter 1977;Hecky et al 1991;Edmond et al 1993) and is indicated by blooms of N-fixing cyanobacteria following upwelling (Hecky and Kling 1981;Salonen et al 1999;Descy et al 2005). In contrast, whole-lake nutrient budgets implicate P as the ''master element'' (Hecky et al 1996), and dissolved nutrient ratios sometimes indicate P limitation (Chale 2004).…”

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confidence: 99%

Top-down and bottom-up controls on periphyton biomass and productivity in Lake Tanganyika

2006

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We studied the effects of nutrient availability and grazers on periphyton in the littoral zone of Lake Tanganyika. Using a combination of dissolved nutrient ratios, nutrient diffusing substrates, and benthic productivity responses to nutrient supplementation, we evaluated whether nitrogen (N) or phosphorus (P) limited periphyton productivity near Kigoma, Tanzania, during the dry seasons of 2001 and 2002. The relative effects of grazers and nutrients on periphyton were quantified by manipulating grazer access to nutrient diffusing substrates. We found very low ambient concentrations of inorganic N and soluble reactive P, but generally higher concentrations of dissolved organic nutrients. Nutrient diffusing substrates indicated a shift from P limitation in 2001 to co-limitation by N and P in 2002, probably as a consequence of unusual coastal upwelling in 2002. Productivity responses of natural epilithic algae to nutrient supplementation also indicated N-P co-limitation in 2002. However, fish and other large grazers had much stronger effects on periphyton than nutrients. Grazers strongly suppressed periphyton biomass, but had weaker negative effects on area-specific gross primary productivity as a result of large increases in biomass-specific gross primary productivity. We conclude that littoral nutrient availability influenced periphyton productivity, but that top-down control predominated.

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Nutrient chemistry of the water column of Lake Tanganyika

Cited by 70 publications

References 16 publications

The stoichiometry of carbon, nitrogen, and phosphorus in particulate matter of lakes and oceans

The stoichiometry of carbon, nitrogen, and phosphorus in particulate matter of lakes and oceans

The physics of the warming of Lake Tanganyika by climate change

Top-down and bottom-up controls on periphyton biomass and productivity in Lake Tanganyika

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