Factors affecting the distribution and abundance of submersed aquatic vegetation in Topock Marsh, an impounded desert wetland (Arizona)

To determine the factors affecting the distribution and abundance of submersed aquatic vegetation (SAV) within Topock Marsh, I measured 4 factors: (1) light availability (water depth and turbidity); (2) substrate type (grain size and organic content); (3) sediment nutrient availability; and (4) exposure to wave action.; Multiple regression indicated that turbidity negatively affected the distribution and abundance of SAV in Topock Marsh during 1996 and 1997. Principal components analysis of sediment data in combination with a manipulative experiment indicated substrate type and sediment nutrients may influence SAV. Young shoots of Najas marina L. grew taller and had more branches when grown in sediments that had a smaller grain size and relatively higher amounts of NH{dollar}sb4{dollar}-N and soluble K.; If the main objective of the refuge is to provide waterfowl foraging habitat, careful manipulation of water levels may be necessary to adequately promote the growth of SAV in Topock Marsh.