T11 AM Aquatic Plants: Methods, Mechanisms and Markers
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 343-344

(POO-1117-836626) Development of a standard growth protocol for the submersed macrophyte Myriophyllum spicatum to test non-target effects of chemicals in aquatic systems.

Poovey, A.¹, Getsinger, K.¹, ¹ US Army Engineer Research and Development Center, Vicksburg, MS, USA

ABSTRACT- Myriophyllum spicatum L. is a rooted submersed macrophyte native to Eurasia, however, it is invasive in North America. Because M. spicatum reproduces through vegetative fragmentation, grows rapidly and is easily cultivated, it has potential as a test species for non-target effects of chemicals in aquatic systems. Growth of this plant was investigated in a series of studies under controlled conditions using combinations of both natural and artificial sediments, fertilization rates, and a variety of aqueous media. The objective was to develop a test system that would support healthy shoot and root growth over a short period, while minimizing algal contamination. Apical shoots were planted in beakers filled with sediment, placed in aquaria containing an aqueous medium, and allowed to grow for 21 d. Initial results demonstrated that plants generated longer shoots and produced more highly developed roots in light intensities of 7000 versus 14,000 lux. As growth in fertilized artificial sediments (e.g. OECD chironomid sediment) was similar to that in a fertilized natural lake sediment, a modified OECD sediment was chosen for subsequent studies. OECD sediment in combination with an aqueous medium modified from the OECD daphnia reproduction test provided acceptable growth when amended with 300 mg L^-1 of both NH₄Cl and Na₂HPO₄ providing a total shoot length increase of 41.6 cm and weight increase of 1.4 g. This sediment and medium combination generally had little algal contamination (chlorophyll a ≤4 mg m^-3). Rooted macrophtyes, such as M. spicatum, effectively mine N and P from the sediments. Aqueous media high in N and P may stimulate phytoplankton blooms rather than contribute to macrophyte nutrition. Phytoplankton blooms developed in aquaria with unfertilized OECD sediment and 1x AAP growth media where chlorophyll a was 12 to 17 mg m^-3, and shoot growth was unacceptable (length increase = 2.8 cm, weight increase = -0.03 g). Based on this work M. spicatum is a candidate for non-target testing of chemicals in aquatic systems; using the sediment and media described, doubling of shoot length has been obtained in 14 days. Further work is needed to refine the method and identify additional causes of algal contamination.

Key words: Eurasian watermilfoil