William H. Funk

Influence of aquatic macrophytes on phosphorus and sediment porewater chemistry in a freshwater wetland

Abstract The influence of the emergent aquatic macrophyte, Menyanthes trifoliata L. on sediment interstitial porewater chemistry, particularly on the distribution of soluble reactive phosphorus (SRP), was investigated at Silver Lake in southwestern Washington (Cowlitz County). Menyanthes trifoliata and many other wetland species create an oxygenated rhizosphere by translocation of oxygen to the roots. Close interval diffusion sampling showed that SRP, total soluble phosphorus (TSP), and concentrations of other redox-sensitive species such as TFe, Fe 2+ , and TMn were reduced in interstitial waters when macrophytes were present. Total alkalinity and pH also were lower and oxidation-reduction potentials were higher in sediments with plants than those in which the plants were removed. Rhizosphere oxidation appears to provide wetland species with a mechanism for sequestering phosphorus and for creating favorable concentration gradients within the root zone.

Habitat Availability and Benthic Invertebrate Population Changes Following Alum Treatment and Hypolimnetic Oxygenation in Newman Lake, Washington

Abstract Changes in benthic macroinvertebrate population density and diversity were studied in a mesotrophic lake with seasonal hypoxia/anoxia prior to and following aluminum sulfate (alum) treatment and hypolimnetic oxygenation. Historically, low oxygen concentrations created a benthic zone with reduced fish predation pressures which allowed chaoborids to flourish. Population densities of chironomids and oligochaetes were suppressed by prolonged periods of summer anoxia Benthic macroinvertebrate community diversity values were indicative of poor water quality and/or habitat quality. Following alum treatment and prior to hypolimnetic oxygenation, chaoborid densities doubled. This was due, in part, to changes in trophic structure which provided an abundant food source for early instar chaoborids. In addition, Newman Lake was stocked with fewer trout in 1990 and 1991 resulting in reduced predation on the invertebrate community. Alum treatment had no effect on chironomid or oligochaete populations. Hypolimne...

Water Quality, Fishery, and Biologic Characteristics in a Shallow, Eutrophic Lake with Dense Macrophyte Populations

ABSTRACT Giffin Lake is a shallow, eutrophic lake in south central Washington and the sub ject of an intensive Phase I restoration diagnostic/feasibility study. Water quality problems in the lake have been manifested principally as excessive growth of the floating-leaved macrophyte, Nymphaea odorata, white water lily. Study results indicate that these macrophytes play a central role in chemical, physical, and biological functioning of the lake. The extensive macrophyte canopy prevents diffusion of oxygen to the sediments by inhibiting both gas exchange with the atmosphere and transfer of wind energy to the water column. Anaerobic conditions develop under the summer macrophyte canopy, as do steep nutrient gradients. Phytoplankton seasonal distribution appears to be strongly influenced by competition with macrophytes for nutrients and light. Zooplankton communities are dominated by rotifers which can tolerate low oxygen conditions and which feed on bacteria and detritus prevalent beneath the macrophytes. Fi...

Zooplankton Responses to Aluminum Sulfate Treatment of Newman Lake, Washington

ABSTRACT Pelagic zooplankton were sampled prior to and following the whole-lake aluminum sulfate (alum) treatment of Newman Lake, Washington, to determine zooplankter responses. Signs of perturbation such as pronounced declines in zooplankton numbers, biomass, and species diversity were exhibited within two weeks after the treatment. These observations may be attributed to a combination of physical action of the settling alum floc, removal of and change in primary food sources, predation by planktivorous fish, and toxicity of aluminum ion. Declines were only temporary, and substantial zooplankter proliferation was evident in the following months due to the abundance of small algae and other food particles. Subsequent monitoring of the zooplankton for 21/2 years showed that the community composition changed after the treatment. Rotifers became more abundant, while biomass dominance shifted from cladocerans and copepods to copepods. Long-term compositional changes may also be attributed to a shift in zoopla...

ENHANCEMENT OF INTERNAL CYCLING OF PHOSPHORUS BY AQUATIC MACROPHYTES, WITH IMPLICATIONS FOR LAKE MANAGEMENT

ABSTRACT Observations over a 14-year period at Liberty Lake, Wash., have indicated a close relationship between the seasonal decline of aquatic macrophyte populations and the onset of planktonic Cyanobacteria blooms. Tracer methods, using radiophosphorus, have been employed in laboratory and in in situ experiments to investigate the ability of Elodea canadensis, an important component of the Liberty Lake macrophyte community, to translocate phosphorus from sediments to the open water. Results of these experiments showed good agreement between release rates determined in the laboratory and in situ for senescing macrophytes. Experiments with actively growing Elodea plants indicate some release or leakage of phosphorus from healthy plants. Nutrient budgets and a phosphorus model for Liberty Lake indicate that internal cycling of sediment phosphorus by aquatic macrophytes is an important source of phosphorus to planktonic primary production as well as direct sediment/water exchange. Indeed, in Liberty Lake, i...

Effects of Multiphase Restoration, Particularly Aluminum Sulfate Application, on the Zooplankton Community of a Eutrophic Lake in Eastern Washington

ABSTRACT Zooplankton populations of Liberty Lake, Washington were investigated over a span of four years to determine the short-term effects of a series of multiphase lake restoration measures on lake zooplankton. The effects of the treatments, particularly of suction dredging of lake bottom sediments and of a two stage whole-lake aluminum sulfate application, were assessed by analyzing population density and biomass fluctuations of Rotifera, Cladocera, and Eucopepoda for several years before and after the treatments were completed. Suction dredging had no apparent effect upon the zooplankton in Liberty Lake. The gross effects of aluminum sulfate applications on the zooplankton population were also minimal. A sharp decline in numbers was observed in all major groups immediately following each alum application, but recovery was evident in the maintenance of typical seasonal growth patterns. The Eucopepoda exhibited rapid recovery following both alum treatments, responding most favorably to the short term o...

Seasonal Patterns in the Zooplankton Community of a Eutrophic Lake in Eastern Washington Prior to Multiphased Restoration

ABSTRACT The zooplankton community of eutrophic Liberty Lake, Washington was investigated at two pelagic stations for a period of one year prior to the initiation of a multiphased lake restoration treatment. Analysis of the microinvertebrate population formed an integral part of an intensive limnological investigation of the physical, chemical, and biological characteristics of the lake prior to, during, and following a series of restoration treatments completed during 1980–81 (Funk et al. 1980). Seasonal variations in the composition, density, and biomass of the major groups and species of the zooplankton are discussed in relation to patterns observed in other localities. The rotifers numerically dominated the community throughout the study period with the species Keratella cochlearis, Kellicottia longispina and Polyarthra spp. making up the largest share of zooplankton density. Cladocerans, primarily Daphnia pulex and D. galeata mendotae, accounted for the largest portion of total biomass. Copepods assu...

Long-term Effects of Dredging on Phosphorus Availability from Liberty Lake Sediments

ABSTRACT The results of dredging at Liberty Lake offer some valuable lessons for the conduct of sediment removal operations for lake restoration objectives. It was planned that approximately 50 ha were to be dredged at Liberty Lake. Differing dredge patterns were produced by two different contractors who performed the actual work, which included the removal of over 4 × 105 m3 of sediment material. In Area 1, deeply dug trenches were separated by undredged rows, while the bottom contour was more uniform in Area 2. The trenching pattern resulted in an actual dredged area of only about 21 ha. Because of slumping of undredged material into the trenches, and because of the remaining pool of high-phosphorus sediments, the dredging at Liberty Lake, especially in Area 1 was not as successful in reducing internal phosphorus loading as anticipated. In addition, macrophyte control from the dredging was not realized in Area 1, as macrophyte regrowth has been rapid. Some considerations for sediment removal in lake res...

OXYGEN DEMAND BY SEDIMENT-GENERATED METHANE

ABSTRACT Although the contribution of sediment-generated methane to dissolved oxygen demand has been well documented in a number of stratified lakes throughout the world, little work on the subject has been performed in shallow, un-stratified lakes. To quantify the role of methane in carbon and oxygen cycling in such environments, carbon and methane budgets were prepared for Carlisle Lake, a small, shallow, unstratified, hypereutrophic lake. The budgets reveal that about 10 percent of the summer oxygen demand is exerted by the bacterial oxidation of methane. Methane production accounts for recycling of about 5 percent of the carbon produced by primary production and about 10 percent of the carbon reaching the sediments. Methanogenesis may indicate the degree of heterotrophic activity in sediments. This work supports such a conclusion and also suggests that methanogenesis may be indicative of the intensity of nutrient regeneration from sediments.