An in situ nutrient addition bioassay study on eight Westland lakes

By: Payne, G.W.
Contributor(s): Kemp, L.J. (DSIR, Division of Marine and Freshwater Science. Taupo) | DSIR, Division of Marine and Freshwater Science. Taupo.
Material type: materialTypeLabelBookSeries: Taupo Research Laboratory report: no. 79Publisher: Taupo, N.Z. : Taupo Research Laboratory, 1985Description: 37 leaves (various pagings) : illustrations (figures, tables) ; 30 cm.Report number: TRL-FR--27/T/79Subject(s): WESTLAND | LAKES | LAKE AHAURA | LAKE BRUNNER | LAKE HAUPIRI | LAKE HOCHSTETTER | KANGAROO LAKE | LAKE KANIERE | LADY LAKE | LAKE POERUA | BIOASSAYS | NUTRIENTS | CHLOROPHYLL A | ATP | BIOCHEMICAL ANALYSIS | WATER CHEMISTRY | NITROGEN COMPOUNDS | NITRATES | PHOSPHORUS | PHOSPHATES | CARBON | NITROGEN | NITROGEN DEFICIENCY | PHOSPHORUS COMPOUNDS | TRACE ELEMENTS | STRATIFICATION | NZMS260K32 | NZMS260K31 | NZMS262 10
Incomplete contents:
Results suggested phosphorus limitation in all lakes studied with nitrogen limitation in samples from lakes Kaniere, Lady and Poerua. In the bioassays particulate phosphorus increased in all lake samples which suggests the microfloras internal phosphorus pools were not full; this is also supported by the short /sup 32/P-phosphate turnover times. Chlorophyll <a> and /sup 14/C uptake suggest many different limitations, phosphorus was the primary or secondary limiting nutrient in samples from lakes Ahaura, Brunner, Haupiri, Hochstetter, Kangaroo and Lady while the last three also showed nitrogen limitation. The Lake Ahaura sample showed a response to nitrate and phosphate in combination only and the sample from Lake Poerua responded to nitrate alone although with such strange responses (decrease on phosphate additions) other limitations may have been masked. The sample from Lake Kangaroo was the only one to show a significant response to the trace element mix. The contention that in these lakes phosphate is the most limiting nutrient is partially true. Particulate phosphorus increases and /sup 32/P-phosphate turnover times support this but five of the eight lake samples also responded to nitrate additions. This work was carried out on one midsummer sample at a time when stratification was approaching its maximum, thus epilimnion nutrients were probably at a minimum, and increases in hypolimnion nutrients were minimal suggesting that there is little decomposition occurring in the hypolimnion therefore producing only a small injection of nutrients when stratification breaks down. Only frequent monitoring of the biologically important nutrients in these lakes will demonstrate if these are low throughout the year. (auth/EIM)
In: Taupo Research Laboratory report
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JOURNAL JOURNAL WELLINGTON
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STACK NO. 79 1985 1 Available J016665

l4 refs; 13 figs; 9 tables

Results suggested phosphorus limitation in all lakes studied with nitrogen limitation in samples from lakes Kaniere, Lady and Poerua. In the bioassays particulate phosphorus increased in all lake samples which suggests the microfloras internal phosphorus pools were not full; this is also supported by the short /sup 32/P-phosphate turnover times. Chlorophyll <a> and /sup 14/C uptake suggest many different limitations, phosphorus was the primary or secondary limiting nutrient in samples from lakes Ahaura, Brunner, Haupiri, Hochstetter, Kangaroo and Lady while the last three also showed nitrogen limitation. The Lake Ahaura sample showed a response to nitrate and phosphate in combination only and the sample from Lake Poerua responded to nitrate alone although with such strange responses (decrease on phosphate additions) other limitations may have been masked. The sample from Lake Kangaroo was the only one to show a significant response to the trace element mix. The contention that in these lakes phosphate is the most limiting nutrient is partially true. Particulate phosphorus increases and /sup 32/P-phosphate turnover times support this but five of the eight lake samples also responded to nitrate additions. This work was carried out on one midsummer sample at a time when stratification was approaching its maximum, thus epilimnion nutrients were probably at a minimum, and increases in hypolimnion nutrients were minimal suggesting that there is little decomposition occurring in the hypolimnion therefore producing only a small injection of nutrients when stratification breaks down. Only frequent monitoring of the biologically important nutrients in these lakes will demonstrate if these are low throughout the year. (auth/EIM)

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