John E. Titus

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The Eurasian watermilfoil (Myriophyllum spicatum L.) has partially replaced wild celery (Vallisneria americana Michx.) as a community dominant in the littoral zones of lakes of Madison, Wisconsin. The two species have very different growth forms, with that of M. spicatum corresponding more closely to the optimal growth form simulated by the macrophyte(More)
The submersed macrophyte Vallisneria americana was grown for seven weeks in a greenhouse to test for differences in the ability of three different sediments to support growth stimulation in response to CO2 enrichment at low pH. Plants accumulated 21- to 24-fold greater biomass at 10 × ambient CO2 concentrations than at ambient CO2 on all sediments. At both(More)
Biomass of the submersed macrophyte Vallisneria americana rose steadily from early June to 50 g dry wt·m−2 in ealry August. Leaves dominated the biomass of this perennial from mid-June through August, after which plants senesced to leave only winter buds as perennating organs. Only 24% of plants sampled flowered during the 1978 growing season, yielding a(More)
Riparian wetlands have a demonstrated ability to filter and control nitrogen (N) and phosphorus (P) movement into streams and other bodies of water; few studies, however, have examined the roles that individual plant species serve in sequestering N and P pollutants. We evaluated the potential for growth and consequent N and P accumulation by five species of(More)
Sphagnum fallax (Klinggr.) Klinggr., a moss growing in hollows close to the water table, is more desiccation tolerant than S. nemoreum Scop., a hummock former distributed high above the hollows. Sphagnum fallax recovered to a greater proportion of its predesiccation photosynthetic rate after one and five days of tissue dryness. Further, a greater percentage(More)
The relative importance of aqueous vs. trophic exposure of fish to polychlorinated biphenyls (PCBs) was investigated. The potential role of different invertebrate prey upon PCB accumulation by fish was also investigated. Pumpkinseed sunfish (Lepomis gibbosus) were exposed in the upper Hudson River under conditions that either permitted feeding upon(More)
We transplanted Nuphar variegata with submersed leaves only into natural lake sediments in pH-, [CO(2)]-, depth-, and temperature-controlled greenhouse tanks to test the hypotheses that more fertile sediment, lower free [CO(2)], and shallower depth would all stimulate the development of floating leaves. Sediment higher in porewater [NH(4)(+)] favored(More)
The submersed macrophyte Utricularia inflata (inflated bladderwort) is a recent invader of Adirondack Mountain lakes (NY, USA). A 15-week greenhouse experiment and a 7-week field experiment were conducted to test the hypothesis that this rootless species fundamentally changes sediment chemistry through its suppression of the native short-statured species,(More)
The submersed freshwater macrophyte Utricularia inflata is a recent invader of Adirondack Mountain lakes (NY, USA). Previous experiments suggested that U. inflata can indirectly change nutrient cycling in Adirondack lake ecosystems by reducing the growth of native isoetid macrophytes, which in turn affects sediment chemistry. A 13-week greenhouse experiment(More)
Experimental and observational studies of the submersed, freshwater macrophyte Vallisneria americana Michx. revealed that depth, wind and wave exposure, and current velocity may all influence fruit set. In this dioecious species, long-pedunculate female flowers are pollinated by free-floating male flowers at the water surface. Average fruit set in the(More)