Average Chlorophyll Concentration Research Articles

Effects of Annual Draining on the Limnology of Sunfish Ponds

Abstract Average concentrations of total phosphorus and chlorophyll α increased annually over a 3-year period in fertilized sunfish ponds that were not drained. Average concentrations of these variables remained approximately the same each year in ponds that were drained annually. Greater phytoplankton production in the undrained ponds, as evident from larger chlorophyll-α concentrations, was attributed to increased availability of phosphorus from sediments. Because phosphorus accumulates in sediments of undrained ponds, fertilization rates likely can be reduced in many ponds with a history of fertilization.

An Integration of Forest and Lake Fertilization: Transport and Transformations of Fertilizer Elements

Forest fertilization (435 kg urea∙ha−1) on the Mohun drainage, northern Vancouver Island, during late fall 1979 resulted in a combined increase in urea, ammonia, and nitrate concentrations to 8000 μg N∙L−1 above control levels in streams not protected with 50-m-wide leave (i.e. unfertilized) strips and 350 μg N∙L−1 in those having leave strips. By spring 1980, dissolved nitrogen loads to Mohun Lake increased by a minimum of 55% in the largest basin and 1924% in the smallest basin. This corresponded to fertilizer losses of 2.1% of the total applied from drainages that had leave strips and up to 5.2% from those where the treatment included direct application to stream channels. Nitrogen transport was dominated by reduced nitrogen species and lasted up to 144 d. Relatively small changes in nitrate transport were attributed to low temperatures, which reduced rates of nitrification. Duringthe3-yr prior to forest fertilization, nitrogen and phosphorus were added to the lake at an N:P ratio of 4.5 (wt/wt) and a load of 1.4–2.2 mg P∙m−2∙wk−1. Spring overturn phosphorus concentrations were 4–5 μg∙L−1 throughout the study and, except during the spring following forest fertilization, N:P ratios (NO3-N:TP) at spring overturn were 3–6 (wt/wt). Despite the low ratios, nitrogen-fixing phytoplankton were not dominant in Mohun Lake. After forest fertilization, average epilimnetic chlorophyll concentrations were 1.8 times higher than in 1979, the last year of lake fertilization. The increase is attributed to the much higher spring overturn N:P ratio that occurred after forest fertilization and to phosphorus recycling processes within the extensive littoral zone of the lake.

Effets des fluctuations rapides de la lumière sur la photosynthèse du phytoplancton

[ 14 C]-assimilation rates were measured on cultures of two unicellular green algae ( Chlamydomonas sp. and Oocystis sp.) as a function of light intensities (saturation curves), under steady light and also under rapidly alternating high and low light intensities. Assimilation rates vary according to the frequency of the intermittent light regime and it falls under two categories: (1) at 0.1 and 0.2 Hz, the assimilation rate is equal to the average of the rates observed at high and low light intensities under steady light, and (2) under 1.0, 1.6 and 10 Hz the assimilation rate is equal to the rate observed under a mean steady irradiance. Moreover, the range of assimilation rates at a given frequency depends on the difference between the high and the low intensities. Batch cultures of Oocystis sp. have been grown under intermittent light of 0.1, 1.0 and 10.0 Hz (same mean intensity). Growth rate under intermittent light of 0.1 Hz is −40% lower than the control under steady light. Photosynthetic potential (P Bmax )and efficiency (α) change with the growth stages of the cultures. At the end of the logarithmic growth phase, both photosynthetic parameters are maximum at 1.0 Hz and minimum at 0.1 Hz. Average cell concentrations of chlorophyll a increase as the frequency of the light regime decreases. During the log phase, concentration of carotenoids relative to chlorophyll a increases at 1.0 Hz, decreases at 0.1 Hz, and remains constant at 10.0 Hz. Under clear sky conditions, wave-induced light fluctuations in the photic layer may therefore enhance primary production, especially (1) in the lower part of the photic layer, where low frequency light changes might cause cell chlorophyll a to increase, and (2) at a depth of 1–4 m, where the main frequencies (of the order of 1.0 Hz), might cause a significant increase of both the photosynthetic potential (P Bmax )and efficiency (α).

Spatial and temporal feeding patterns of copepods from the North Pacific centra gyre

Spatial and temporal feeding patterns (determined from an index of gut fullness) are described for 10 typical species of calanoid copepods collected from the North Pacific central gyre (September 1968 to June 1977), an area where the zooplankton is food limited and there were a-priori reasons to suspect that feeding and competition for food were important in regulating zooplankton community structure. Over 100 samples from 11 cruises to the eastern part of the gyre were examined, and patterns of gut fullness were related to environmental variables and the copepod species structure. The copepods studied all tended to be omnivores and food generalists. Males had lower indices of gut fullness than females but both males and females of a species had similar spatial and temporal feeding patterns. Guts were usually fuller at night than during the day, even in nonmigrating species; however, within nighttime depth distributions, no depths were preferred for feeding. There were also differences between species in mean gut fullness, but different species tended to have similar spatial and temporal feeding patterns. There was considerable spatial variability, and locales could be identified in which most species had higher indices of gut fullness. The copepods were not necessarily more abundant in these locales, nor did these tend to be areas of above average chlorophyll concentration. These patterns were consistent with relatively nonselective feeding, and there was no evidence that these species separate their niches by feeding at differing places or times.

Antenna chlorophyll a and P700. Exciton transitions in chlorophyll a arrays

Exciton calculations have been carried out for 16 distinct cases of randomly generated chlorophyll a arrays to assist in the assessment of various possibilities for the chlorophyll distribution in the thylakoid membrane of green plants. Each of the cases is distinguished by its packing density and by the constraints applied to the orientation of transition dipoles. Each array consists of 40 antenna chlorophyll a molecules with an absorption maximum at 670 nm before transition density coupling and one P700 chromophore with an absorption maximum at 700 nm. Transition density coupling always broadens the absorption bands and sometimes shifts the position of the absorption maxima. Transition density coupling between the P700 chromophore and the antenna chlorophyll molecules shifts the P700 absorption band to lower energies and, for some cases, increases or decreases the dipole strength of the P700 absorption band by as much as 50 percent. In general, for comparable packing densities, the effects of transition density coupling are more pronounced for two-dimensional arrays than for three-dimensional arrays. The present exciton calculations show that if the various in vivo ''forms'' of chlorphyll a correspond to exciton transitions in chlorophyll a arrays, then the local chlorophyll concentration in the arrays must bemore » much greater than the average chlorophyll concentration of approximately 0.1 M in the thylakoid membrane; perhaps the local chlorophyll concentration could be as high as 1 M.« less

本州中部湖沼の夏季におけるけん濁態蛋白質および核酸の鉛直分布

Vertical distributions of particulate protein, RNA and DNA were surveyed in 15 lakes in central Japan in late summer. Average concentrations of chlorophyll a, protein, RNA and DNA in the photic zone of these lakes were 1.6-185.5 mg/m3, 143-4565 mg/m3, 24-2086 mg/m3 and 1.0-46.8 mg/m3, respectively. Concentrations of particulate protein and nucleic acids, especially of DNA, showed marked vertical changes in stratified lakes. The changes were rather small in homothermal lakes. In wellstratified eutrophic lakes, concentrations of protein and nucleic acids were much higher in the hypolimnion than in the epilimnion. The ratios of RNA/protein and DNA/protein fluctuated vertically. Higher values for the former were found in upper layers of extremely eutrophic lakes and those for the latter were detected in lower layers of stratified eutrophic lakes. A high DNA/protein value was found at the same depth with concentration-maximum of bacteriochlorophyll.