Field Determination of the Critical Nutrient Concentrations for Cladophora in Streams

Abstract

Many streams in southern Ontario experience excessive seasonal growth of aquatic plants such as Cladophora and Potamogeton. A direct relation, with a regression coefficient of 0.87, was observed between ambient P concentration in the water and P content of plant tissue in six rivers. Critical or growth controlling total P concentration of 60 μg/liter in stream water and 1.6 mg/gram dry weight in plant tissue were determined. Unlike P, no significant correlation was observed between N content of plant tissue and N concentration in water. The correlation of total P with plant growth can be used to estimate the waste load which would result in maximum growth rate of Cladophora.

Studies on the growth ofCladophora glomeratain laboratory continuous-flow culture

“…However, this mean treatment level was based on 60 individual measurements and, since the precision of phosphate estimation was to the nearest 0.05 mg1-1, calculation reveals that this value might actually have been as high as 0.098 mg PO4-Cladophora 443 P 1-1. Wong & Clark (1976) evaluated the critical phosphorus concentration as 0.060 mg P1-1, whilst Herbst (1969) supported the suggestion of 0.030mg P l-l; results from this study generally support these estimates. Pitcairn & Hawkes (1973), however, found that rivers containing less than 1.0 mg P1 -a supported only modest growths of Cladophora, and Robinson (1983) found biomass significantly less in a simulated stream ecosystem with mean monthly phosphate concentrations of 0.5-0.7 mg P 1-1 than in similar streams with phosphate concentrations of 1.9-3.1 and 3.0-3.8 mg P 1-1.…”

Inorganic mineral nutrient level studies on Potamogeton pectinatus L. and Enteromorpha prolifera in Forfar Loch, Scotland

“…In a similar study in North Thames River in Canada, Wong & Clark (1976) found significant positive correlation in total phosphorus concentration in water and in P . pectinatus tissue, having a regression coefficient of o .84, which is slightly lower than in this study (r = 0.941).…”

“…Gerloff & Krombholz, 1966;Gossett & Norris, 1971 ;Casey &Downing, 1976 andWong &Clark, 1976 . In such studies, one must assume the ability of the plants to take up mineral nutrients from the surrounding water .…”

Seasonal Changes of Nitrogen Metabolism in the Sporophyte of Laminaria japonica (Phaeophyceae).

“…10,11,[18][19][20][21][22] It is considered that the discrepancy is due to the difference in experimental condition (nitrogen source, water flow rate, density, etc.) between fields and laboratory.…”