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1. The macrophyte community of Lake George, New York is diverse, composing of forty-eight submersed species representing a wide range of habitats, depth ranges and life-history strategies. The photosynthetic rates of seven representative submersed aquatic macrophytes were determined in laboratory studies using measurements of short-term changes in oxygen concentration at eight light intensities from 0 to 1000 |.imol m~^ s'' at 20°C. The species examined were: Elodea canadensiSy Myriophyllum spicatum., Potamogeton amplifoUus, P. graminet4S, P. praelongus, P. robbinsii, and ValUsneria americana.2. Comparisons of maximum net photosynthesis, Miehaelis-Menten V(nax and Km for photosynthesis versus irradiance, and dark respiration rates correlated with changes in community composition and species distribution with depth.3. In particular, Myriophyllum spicatum exhibited a high photosynthetic rate (V^ax) and high hght requirement (both in compensation point and higher half-saturation constant {K^) indicative of a high lightadapted species. In contrast, the native species exhibited shade-^tolerant characteristics.4. Simple daily carbon balance models indicate that M. spicatum has a higher positive carbon balance near the surface than the native species, but carbon balance decreased more rapidly with decreased light. All species showed greatly reduced carbon balances under a simulated M. spicatum canopy, indicating that native species might not survive. Myriopyllum spicatum leaves would experience self-shading and eventual sloughing.

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Effects of eugenol (AQUI-S â 20E, 10% active eugenol) sedation on cool water, yellow perch Perca flavescens (Mitchill), and warm water, Nile tilapia Oreochromis niloticus L. fish metabolic rates were assessed. Both species were exposed to 0, 10, 20 and 30 mg L À1 eugenol using static respirometry. In 17°C water and loading densities of 60, 120 and 240 g L À1 , yellow perch controls (0 mg L À1 eugenol) had metabolic rates of 329.6-400.0 mg O 2 kg À1 h À1 , while yellow perch exposed to 20 and 30 mg L À1 eugenol had significantly reduced metabolic rates of 258.4-325.6 and 189.1-271.0 mg O 2 kg À1 h À1 respectively. Nile tilapia exposed to 30 mg L À1 eugenol had a significantly reduced metabolic rate (424.5 AE 42.3 mg O 2 kg À1 h À1 ) relative to the 0 mg L À1 eugenol control (546.6 AE 53.5 mg O 2 kg À1 h À1 ) at a loading density of 120 g L À1 in 22°C water. No significant differences in metabolic rates for Nile tilapia were found at 240 or 360 g L À1 loading densities when exposed to eugenol. Results suggest that eugenol sedation may benefit yellow perch welfare at high densities (e.g. live transport) due to a reduction in metabolic rates, while further research is needed to assess the benefits of eugenol sedation on Nile tilapia at high loading densities.