Effects of AOC and Phosphorus on Bacterial Growth under Oligotrophic Condition (1)

The effects of phosphorus and organic carbon on bacterial growth were investigated in the laboratory. The bacteria sampled from the drinking water network of Tianjin were inoculated into water samples with different content of phosphorus (0～15µg PO43--P/L) and assimilable organic carbon (10～200µgAOC/L). The inoculated water samples were incubated at 20°C. Bacterial growth was monitored in every 2 days in the beginning of cultivation and in every 4 days or more in the later of the cultivation. Results showed that Phosphorus had obvious promotion on bacterial growth, which included shortening the lag phase evidently, increasing the growth rate and the maximum cell count in stationary phase. Carbon can only increase bacterial number. Under oligotrophic condition，when ratio of AOC: P in nutrients of water was more than 100:5, phosphorus was the limiting factor of bacterial growth. The bacterial yield factors against phosphorus and AOC were 1.1×109CFU/µgP and 9.0×107CFU/µgAOC respectively. Phosphorus was more sensitive than AOC. When the phosphorus concentration was less than 0.7µg/L in water samples, it was very difficult for bacteria to obtain phosphorus, and then growth of bacteria was very slowly or in lag phase in the first nine days of incubation time. In drinking water with low concentration of phosphorus (<0.7µg/L) and disinfectants, bacterial regrowth may be controlled. The paper will be Narrated in two parts, “Effects of AOC and Phosphorus on Bacterial Growth under Oligotrophic Condition (1)” and “Effects of AOC and Phosphorus on Bacterial Growth under Oligotrophic Condition (2)”.

Effects of AOC and Phosphorus on Bacterial Growth under Oligotrophic Condition (2)

The effects of phosphorus and organic carbon on bacterial growth were investigated in the laboratory. The bacteria sampled from the drinking water network of Tianjin were inoculated into water samples with different content of phosphorus (0～15µg PO43--P/L) and assimilable organic carbon (10～200µgAOC/L). The inoculated water samples were incubated at 20°C. Bacterial growth was monitored in every 2 days in the beginning of cultivation and in every 4 days or more in the later of the cultivation. Results showed that Phosphorus had obvious promotion on bacterial growth, which included shortening the lag phase evidently, increasing the growth rate and the maximum cell count in stationary phase. Carbon can only increase bacterial number. Under oligotrophic condition，when ratio of AOC: P in nutrients of water was more than 100:5, phosphorus was the limiting factor of bacterial growth. The bacterial yield factors against phosphorus and AOC were 1.1×109CFU/µgP and 9.0×107CFU/µgAOC respectively. Phosphorus was more sensitive than AOC. When the phosphorus concentration was less than 0.7µg/L in water samples, it was very difficult for bacteria to obtain phosphorus, and then growth of bacteria was very slowly or in lag phase in the first nine days of incubation time. In drinking water with low concentration of phosphorus (<0.7µg/L) and disinfectants, bacterial regrowth may be controlled. The paper will be Narrated in two parts, “Effects of AOC and Phosphorus on Bacterial Growth under Oligotrophic Condition (1)” and “Effects of AOC and Phosphorus on Bacterial Growth under Oligotrophic Condition (2)”.

Planktonic ciliates from an oligotrophic South Andean lake, Morenito Lake (Patagonia, Argentina)

In this contribution we have studied the planktonic ciliates from Morenito Lake, an oligotrophic lake situated in the South Andes of Argentina. Six species that are new records for South America or Argentina are described and illustrated. Besides, population dynamics of the ciliate species were studied during a spring--summer period. Strobilidium lacustris and Balanion planctonicum were the most abundant species, showing a maximum in mid summer. Paradileptus elephantinus was present all over the period while Urotricha furcata was observed in late summer samples. Strobilidium lacustris and S. humile were found to be occasional species during the studied period. The recorded ciliate assemblage with oligotrichs and prostomates as dominant indicate the oligotrophic condition of the lake.

Use of Lake Fossil Diatom Assemblages to Determine Historical Changes in Trophic Status

Based on the composition of surface sediment diatom assemblages of 30 lakes a classification index for lake trophic status was developed. The lakes were selected to represent a continuum ranging from oligotrophic to eutrophic lake types. A trophic index quotient was derived. The log diatom inferred trophic index (D.I.T.I.) was regressed against the trophic status of the lakes as determined by the log total phosphorus (r = 0.84) and log chlorophyll-a (r = 0.91). Multiple regression analyses showed significant correlations between log D.I.T.I. and the log percentage abundances of oligotrophic, mesotrophic, and eutrophic species (r = 0.89). The abundance of the trophic indicator diatom species depends not only on total phosphorus and chlorophyll-a, but possibly on the interaction of these with other factors. Using this approach, past trophic changes were inferred for oligotrophic Barbara Lake and eutrophic Chemung Lake. The study suggested that Barbara Lake had retained its present day oligotrophic condition over the last 200 yr, whereas major trophic changes have occurred in Chemung Lake.

COMPOSIÇÃO E DISTRIBUIÇÃO DO FITOPLÂNCTON EM ÁREAS COSTEIRAS E OCEÂNICAS DA REOIAO SUESTE DO BRASIL

Total phytoplankton samples and hydrographical parameters were collected from the surface of 16 stations located in the southeastern sector of the brazilian coast during the autumn cruise of the R/V “ Almirante Saldanha” . The limits of temperature (22 — 25°C) and salinity (35,0 — 37,1 x 10‘s) observed indicated the great influence of the Tropical Water over the sampling area where the oligotrophic condition is certainly due to the low nutrient concentrations of this watermass. Phosphate, nitrate and silicate ranged from 0.0 to 0.63, 1.41 to 5.69 and from 4.10 to 25,25 ftg-at.r1, respectively.The most frequent diatoms were Coscinodiscus spp, Coscinosira sp, Pleurosigma sp, Pseudoeunotia doliolus, Thalassionema nitzschioides, Thalassiothrix frauenfeldii and T. mediterrânea, among 49 species observed. Prorocentrum and Protoperidinium spp dominated the dinoflagellate population although the genus Ceratium was represented by a greater number of species. Cyanophycean cells were abundant in coastal (Anabaena sp) and oceanic (Trichodesmium erythraeum) samples.The phytoplankton community was numerically dominated by nanoplanktonic organisms like phytoflagellates (including monads) and the coccolithophorid Coccolithus huxleyi. The phytoplankton association observed in the present study is typical of oligotrophic warm waters of the Brazil Current. Amostras de fitoplâncton total e parâmetros hidrográficos foram obtidos na superfície de 16 estações localizadas no setor sudeste da costa brasileira durante o outono de 1983. Os limites de temperatura (22 — 25°C) e salinidade (35,0 — 37,1 x10 “) observados indicaram a influência da Água Tropical na área estudada onde as condições oligotróficas são devidas à baixa concentração de nutrientes nessa massa d’água. Fosfato, nitrato e silicato variaram entre 0,0 e 0,63, 1,41 e 5,69, e 4,10 e 25,25 /ig-at.r1, respectivamente.As diatomáceas mais freqüentes foram Coscinodiscus spp, Coscinosira sp, Fleurosigma sp, Pseudoeunotia doliolus, Thalassionema nitszchioides, Thalassiothrix frauenfeldii e T. mediterrânea, dentre as 49 espécies observadas. Prorocentrum e Protoperidinrum spp dominaram a população de dinoflagelados apesar do gênero Ceratium ter apresentado o maior número deespécies. As cianofíceas Anabaena sp e Oscillatoria (=Trichodesmium) erythraeum foram abundantes nas amostras costeiras e oceânicas.A comuindade fitoplanctônica foi numericamente dominada por organismos do nanoplâncton, tais como fitoflagelados (incluindo-se mônadas) e o cocolitoforídeo Coccolithus huxleyi. A associação fitoplanctônica observada no presente trabalho é típica das águas quentes e oligotróficas da Corrente do Brasil.

Whole-Lake Fertilization Experiments in Coastal British Columbia Lakes: Empirical Relationships between Nutrient Inputs and Phytoplankton Biomass and Production

Seventeen warm monomictic coastal lakes in British Columbia were studied from 1980 to 1983. Inorganic nitrogen and phosphorus were applied to 13 of the lakes in some or all years of the study. In the untreated condition, lakes were ultraoligotrophic with low concentrations of nutrients (1.0–4.1 μg total P-L−1 at spring overturn), of average summer chlorophyll (0.49–2.57 μg∙L−1), and of average daily primary production (3.0–10.5 mg C∙m−3∙d−1). The lakes' oligotrophic condition is sustained by their low residence time (0.2–7.3 yr) and by low nutrient inputs from the generally steep granitic drainage basins. The lakes respond predictably to nitrogen and phosphorus additions and are generally phosphorus limited, as shown by the significant positive relationships between average summer chlorophyll and total phosphorus at spring overturn (r = 0.81) in unfertilized lakes, between average summer chlorophyll and phosphorus load from fertilizer (r2 = 0.62) in fertilized lakes, by the high average particulate C:N:P ratios (152:20:1), and by the high average TN:TP ratio (89).