Nutrient and trace element limitation of phytoplankton growth and effects of groundwater influx, Lake Hayes, Otago

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Bayer, Tina

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Abstract:

In this study macronutrient and trace element (B, Cu, Fe, Si, Mo, Zn) limitation of phytoplankton growth in Lake Hayes, Otago, was investigated from March to July 2006, using nutrient enrichment bioassay experiments. In addition, groundwater and surface water were compared in their importance as sources of macronutrients and trace elements to the lake. Bioassay experiments suggest that phytoplankton growth was limited by N and Zn in May 2006. Although no direct conclusions can be drawn from bioassays in March and April, nutrient data indicates a potential shortage of dissolved nutrients, and a potential for N, or NP limitation in these months. This indicates that N (still) seems to be the limiting macronutrient in Lake Hayes late in the stratification period despite, or probably because of, land use changes in the catchment. Probably as a result of high nutrient stress in March and April, the phytoplankton community was dominated by Ceratium, a mixotrophic dinoflagellate, which is assumed to have a competitive advantage in times of shortage of inorganic nutrients. Due to Ceratium 's mixotrophy phytoplankton growth was not necessarily limited by the availability of dissolved inorganic nutrient in March and April, despite the low supply. Groundwater was found to be an important contributor of N, Si and some essential trace elements (B, Se, and Zn) to Lake Hayes from March to July 2006. Although no direct groundwater influx to the lake was recorded, influx via the Lake Hayes Spring supplied approximately one third of the total external nitrate load and 20% of Zn, despite the spring only accounting for 10 % of the total water influx. Future management should take into consideration that groundwater is an important pathway of nitrate and trace element influx.

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v. 113 p ill., diagrams., 30cm.

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OU geology Identifier:

2006Bayer

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POLYGON ((168.781473646059908 -44.954535188228874,168.838680682954475 -44.956637730288598,168.834180307065822 -45.004823227209428,168.778669589788365 -45.001828549862559,168.781473646059908 -44.954535188228874))

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http://download.otagogeology.org.nz/temp/Abstracts/2006Bayer.pdf

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Citation

Bayer, Tina, “Nutrient and trace element limitation of phytoplankton growth and effects of groundwater influx, Lake Hayes, Otago,” Otago Geology Theses, accessed February 7, 2025, https://theses.otagogeology.org.nz/items/show/454.

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