Date of Award

Fall 1981

Project Type

Dissertation

Program or Major

Botany

Degree Name

Doctor of Philosophy

Abstract

Myriophyllum heterophyllum is a nuisance, submersed hydrophyte in New Hampshire. First observed in Lake Winnipesaukee, New Hamsphire during the 1960s, the plant infested over 22 miles of the lake's shoreline by 1980. Circumstantial evidence suggests that M. heterophyllum was accidently introduced to New Hamsphire by trailered boats. Physiological and ecological data that relate to the recent success of this species in the state are reviewed.

Myriophyllum heterophyllum submersed apices were analyzed for ash, phosphorus, sodium, potassium, calcium, magnesium, iron, manganese, zinc, copper and lead over a 2 1/2 year period, and the floral stem, apex, sub-apex, mid-stem, lower stem and root for one year.

Apical mineral content was influenced by both the seasons and sample location. The recurrent seasonal variations in apical mineral content suggest that the time of sampling can greatly influence the results and interpretation of tissue chemistry analysis in submersed hydrophytes. The six plant structures sampled differed significantly in mineral content, but seasonal pulses for each mineral were usually in synchrony between the different structures sampled. Dominant minerals were sodium and potassium in the stem, calcium in the floral spike and iron in the roots. The data suggest that M. heterophyllum does not fulfill its nutrient requirements by previous storage, but instead, it mobilizes minerals directly from the sediments.

The competitive interactions between M. heterophyllum, phytoplankton and sediments in the littoral zone of Lake Winnipesaukee were examined. Nutrient additions were made to in situ enclosures with (a) littoral water only, (b) littoral water and rooted M. heterophyllum, (c) littoral waters and sediments, and (d) littoral water, sediments and rooted M. heterophyllum. Changes in littoral waters before and after continuous nutrient additions from nutrient rich sewage treatment plant effluent were also monitored. The results suggest that nutrient levels in the water determine whether submersed macrophytes or phytoplankton will become dominant in the littoral zone, and that the capacity of the littoral sediments to sorb phosphorus is a critical factor in regulating nutrient availability in the water. Data on the seasonal changes in phytoplankton and water chemistry in littoral waters harboring dense growths of M. heterophyllum, and herbicide-treated waters are also presented.

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