Relations of phytoplankton in situ primary production, chlorophyll concentration and underwater irradiance in turbid lakes

Abstract

In order to study the relationships among primary productivity, chlorophyll content and light conditions (underwater quantum irradiance, diffuse attenuation coefficient) in turbid lakes, we performed a series of measurements in three Estonian lakes (Peipsi, Võrtsjärv and Harku) during 2003-2005. We focused on (1) comparison of in situ vertical profiles of planar and scalar quantum irradiances in the water, (2) extremely high values of chlorophyll content and primary production in some turbid lakes and (3) analysis of the formation of the vertical profiles of primary production (shape and the depth of its maximum value) as a function of incident irradiance. The following parameters were measured: (a) primary production at different depths, (b) incident planar quantum irradiance in the region of 400-700 nm, (c) underwater downwelling planar and scalar quantum irradiances at different depths in the same waveband, (d) relative transparency of water (Secchi depth), (e) concentrations of chlorophyll a and (f) spectra of beam attenuation coefficient for unfiltered and filtered water in the wavelength range of 350-700 nm (from water samples). During 36 measurement days (14 in Peipsi, 14 in Võrtsjärv and 8 in Harku), and we collected reliable dataset for 53 measurement series. Our data showed the relative difference between underwater planar and scalar quantum irradiance in a range of about 25-65% implying big differences in primary production models if instead of the preferable scalar quantum irradiance planar irradiance data are used. The results showed a large variation of vertical profiles of primary production in relation to illumination conditions. The depth of maximum primary production depended on water turbidity and incident irradiance, and was located at the water surface in case of low illumination. The relationship between vertically integrated primary production and chlorophyll concentration could be described by a power function with an exponent of 0.64 (R 2 = 0.81).

Planktonic production and respiration in a subtropical lake dominated by Cyanobacteria

“…The production rates and assimilation numbers from Peri Lake showed lower values than other tropical lakes (Erikson et al, 1998;Stenuite et al, 2007;Arst et al, 2008;Tilahun and Ahlgren, 2010;Montero et al, 2011), but were similar to Brazilian lakes, such as some lakes in the middle of the Rio Doce basin (Petrucio et al, 2006), Carioca Lake (Barbosa, 1979), and Guarapina Lake, in southeastern Brazil (Moreira and Knoppers, 1990). Although, the production rates of Peri Lake are within the range of data derived from Bassoli (2006), it was lower than some environments, such as Paranoá Lake (Cavalcanti et al, 1992) and Jurumirim Reservoir (Henry et al, 1998), the latter classified as oligotrophic.…”

Development and application of a phytoplankton primary production model for well-mixed lakes

“…Figure 7 demonstrates this regression relying on the values of measured int P (2-hour incubations at six depths in the water) obtained using the results of our episodic measurements of ( ) P z in three lakes (Peipsi, Võrtsjärv, Harku) from 2003 to 2009 (altogether 78 results of int ). P Lake Harku is a small hypertrophic lake in northern Estonia, described in (Arst et al, 2008c). In Fig.…”

“…Its water is optically turbid (in summer conditions the Secchi depth, SD , z usually varies from 0.3 to 1.6 m), and the underwater light climate is strongly affected by the water level and ice conditions (Reinart and Nõges, 2004;Nõges and Nõges, 2006;Arst et al, 2008c). The diffuse attenuation coefficient for the PAR region (400-700 nm), d,PAR , K is normally between 1.5 and 3.8 m -1 (only in September 1996, after a very dry summer, SD z was as low as 0.15 m and d,PAR K was 6.5 m -1 ) (Reinart and Herlevi, 1999;Arst et al, 2008c). The range of chl C in ice-free conditions is 20-102 mg m -3 (Paavel et al, 2008).…”

“…It is the fourth largest lake in Europe. According to Arst et al (2008c), its SD z varies in summer from 0.4 to 4.8 m, the values of d,PAR K are between 0.74 and 2.58 m -1 , and chl C varies between 1.8 and 37 mg m -3 . Lake Peipsi is defined as a large unstratified eutrophic lake with oligohumic water of medium hardness (Jaani, 2001).…”

Primary production of aquatic macrophytes and their epiphytes in two shallow lakes (Peipsi and Võrtsjärv) in Estonia

“…To compare the PP of phytoplankton with the littoral production of epiphytes and macrophytes we used the results of depth-integrated pelagic phytoplankton PP estimates. Concurrent phytoplankton PP measurements were carried out by the 14 C assimilation technique (see Arst et al 2008). Areal epiphyte and macrophyte PP (mg C m -2 day -1 ) were calculated using available information on macrophyte biomass (g m -2 , DW) for both lakes.…”