Annual patterns of phytoplankton density and primary production in a large, shallow lake: the central role of light

Abstract

1. We studied the seasonal dynamics of suspended particulate matter in a turbid, large shallow lake during an annual period . We relate the patterns of seston concentration (total suspended solids), phytoplankton biomass and water transparency to the seasonal pattern of incident solar radiation (I 0 ). We also report the seasonal trends of phytoplankton primary production (PP) and photosynthesis photoinhibition due to photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) (I b and UV 50 ). 2. We first collected empirical evidence that indicated the conditions of light limitation persisted during the study period. We found that the depth-averaged irradiance estimated for the time of the day of maximum irradiance (I mean-noon ) was always lower than the measured onset of light saturation of photosynthesis (I k ). 3. We then contrasted the observations with theoretical expectations based on a light limitation scenario. The observed temporal patterns of seston concentration, both on a volume and area basis, were significantly explained by I 0 (R 2 = 0.39 and R 2 = 0.37 respectively). The vertical diffuse attenuation coefficient (kd PAR ) (R 2 = 0.55) and the depthaveraged irradiance (I mean ) (R 2 = 0.66), significantly increased with the I 0 ; while the irradiance reaching the lake bottom (I out ) significantly decreased with the incident irradiance (R 2 = 0.49). However, phytoplankton biovolume maxima were not coincident with the time of the year of maximum irradiance. 4. A significant positive relationship was observed between PP estimated on an area basis and I 0 (R 2 = 0.51, P < 0.001). In addition, the parameters describing the photosynthetic responses to high irradiances displayed marked seasonal trends. The photosynthesis photoinhibition due to PAR as well as to UV were significantly related to incident solar radiation (PAR: R 2 = 0.73; UV: R 2 = 0.74). These results suggest adaptation of the phytoplankton community in response to changes in incident solar radiation.

Long-Term Seasonal Trends in the Prey Community of Delta Smelt (Hypomesus transpacificus) Within the Sacramento-San Joaquin Delta, California

“…Solar insolation and precipitation are two factors that influence these processes, along with water column light penetration and heat absorbance (Cloern 1991;Torremorell et al 2009). To describe ecological succession of the Estuary's food web taxa, we calculated monthly mean solar declination for San Francisco Bay using the NOAA solar calculator (http:// www.esrl.noaa.gov/gmd/grad/solcalc/).…”

New approaches for growth improvement in pejerrey Odontesthes bonariensis (Valenciennes, 1835) culture (Atherinomorpha: Atherinopsidae)

“…Moreover, through this method, Colautti et al (2010) obtained the best mean daily growth rate of 0.86mm day -1 ever recorded for juveniles of 45-60 days of age, and survival rates between 59-65%, which are within the range registered by intensive and semi-intensive culture practices. Nevertheless, those authors pointed out that during the months of autumn and winter, when the productivity of these lakes decreases (Torremorell et al, 2009), pejerrey growth in extensive cage culture becomes limited by low temperatures and by the zooplankton availability. As extension of this findings, Colautti et al (2010) suggested that those rates could be improved by supplying artificial food during the periods when the lakes productivity diminish.…”

The effects of storm-induced events on the seasonal dynamics of epilithic algal biomass in subtropical mountain streams

“…The growth of darkacclimated algae may show increased sensitivity to variations in incidental irradiance than do light-acclimated algal communities (O'Brien et al 2009). We suggest that direct measurements of the irradiance intensity, the site-specific algal growth rate, and quantitative assessments of the relationship between photosynthesis and irradiance (P-I) are needed to develop a better understanding of how light availability alters the temporal dynamics of algal biomass and to examine the combined effects of light and nutrients on the growth of epilithic algae in streams (Kaiblinger et al 2007;Torremorell et al 2009). …”