Barry C. Moore

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.

Survival of Salmonella enterica in Freshwater and Sediments and Transmission by the Aquatic Midge Chironomus tentans (Chironomidae: Diptera)

ABSTRACT Survival of a nalidixic acid-resistant strain of Salmonella enterica serovar Typhimurium mr-DT-104 in water and sediments was tested using artificially contaminated aquaria. Water samples remained culture positive for salmonella for up to 54 days. Sediment samples were culture positive up to 119 days. In addition, potential mechanisms for spreading salmonella in the environments by chironomid larvae and adults were tested. We evaluated the acquisition of mr-DT-104 by chironomids from contaminated aquatic sediments and subsequent spread to uncontaminated sediments. Larval chironomids raised in contaminated sediments became culture positive, and the bacteria were carried over to adults after emergence. Contamination of clean sediments by chironomid larvae was not demonstrated. These findings clearly suggest that mr-DT-104 serovar organisms can survive in aquatic sediments for at least several months. Uptake of salmonellae by chironomid larvae and adults suggests that they are possible vectors of mr-DT-104 in both aquatic and terrestrial environments, although the role of larval defecation in movement of bacteria to new sediments was not demonstrated.

Morphological abnormalities in Chironomus tentans exposed to cadmium—and copper-spiked sediments

The induction of mouthpart deformities and the developmental response with exposure to sediments spiked with three concentrations (9, 39, and 61 microgg(-1) Cd dry wt.) of cadmium (Cd) and three concentrations (30, 125, and 215 microgg(-1) Cu dry wt.) of copper (Cu) were investigated. Mouthpart deformity proportions in Chironomus tentans larvae were compared between metal-spiked and control populations and between parent and offspring (F1) populations. Cd- and Cu-treated sediments induced deformities (low Cd=13%, medium Cd=7%, high Cd=4%, low Cu=6%, medium Cu=9%, high Cu=6%) at significantly higher proportions than control (3%) sediments. No negative developmental response was determined. Larval sizes in metal-treated aquaria and control aquaria were not significantly different. F1 larvae from parents reared in medium and high Cu had significantly lower deformity rates than their parents. Our research adds to the growing evidence implicating heavy metals in general, and Cd and Cu specifically, as teratogenic agents.

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...

Induction of morphological deformities in Chironomus tentans exposed to zinc‐ and lead‐spiked sediments

Laboratory experiments were used to assess morphological responses of Chironomus tentans larvae exposed to three levels of zinc and lead. Chironomus tentans egg masses were placed into triplicate control and metal-spiked aquaria containing the measured concentrations 1,442, 3,383, and 5,562 microg/g Pb dry weight and 1,723, 3,743, and 5,252 microg/g Zn dry weight. Larvae were collected at 10-d intervals after egg masses were placed in aquaria until final emergence. Larvae were screened for mouthpart deformities and metal body burdens. Deformities increased with time of exposure in both Zn and Pb tanks. Deformity rates between the three Zn concentrations differed statistically, with low and medium Zn levels containing the highest overall deformity rates of 12%. Deformity rates for larvae held in the Pb aquaria were found to differ significantly. Larvae in the low-Pb tanks had a deformity rate of 9%. Larvae and water from both the Zn and Pb aquaria had increasing metal concentrations with increasing sediment metal concentration. Results demonstrate that Zn and Pb each induce chironomid mouthpart deformities at various concentrations. However, a clear dose-related response was not demonstrated. Our research provides more support for the potential use of chironomid deformities as a tool for the assessment of heavy metal pollution in aquatic systems.

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...

Newman Lake restoration: A case study. Part I. Chemical and biological responses to phosphorus control

Abstract In the late 1960s and early 1970s, summer and fall blooms of cyanobacteria began to occur in Newman Lake, Washington (zavg: 5.6 m, zmax: 9.0 m); through the next decade, these blooms intensified and became an annual occurrence. Community efforts in the mid-1980s sparked a Restoration Feasibility assessment of the lake and watershed that indicated total annual gross phosphorus loading of at least 3000 kg, with a major portion (∼83%) attributable to internal recycling associated with summer hypolimnetic oxygen depletion. Implementation activities began September 1989, with watershed controls and a whole-lake alum treatment, followed in 1992 by installation of a Speece cone for hypolimnetic oxygenation and in 1997 by addition of a dual-port, microfloc alum injection system. Average summer volume-weighted total phosphorus has declined from prerestoration levels exceeding 50 μg-P/L to an average of 21 μg-P/L over the past 7 years (15–28 μg-P/L). Most notably, peak annual biovolumes of cyanobacteria and their representation within the phytoplankton community have decreased substantially, with increased prevalence of diatoms, green and golden-brown algae. A clearwater phase following spring blooms of diatom and/or golden-brown algae has occurred during those last 7 years, although this phenomenon was observed in the prior three decades. Overall, the restoration has been a success, and lake response to nutrient reduction at Newman Lake is consistent with worldwide observations that emphasize the need for long-term perspectives and commitment in lake restoration and management. Continuation of internal load controls and increased emphasis on external nutrient abatement will be necessary to continue the positive water quality trends despite future development increases and land use changes.

Identifying best methods for routine ELISA detection of microcystin in seafood

Ingestion of water contaminated with the cyanotoxin, microcystin (MC), can pose serious health risks to humans. MC is also known to accumulate in seafood; however, this exposure pathway is much less understood. A fundamental element of this uncertainty is related to analytical difficulties. Commercially available enzyme-linked immunosorbent assays (ELISAs) offer one of the best options for routine MC detection, but methods of detecting MC in tissue are far from standardized. We spiked freshwater finfish and marine mussel tissues with MC, then compared recovery rates using four different preparation protocols and two ELISA types (polyclonal anti-MC-ADDA/direct monoclonal (DM)). Preparation protocol, type of ELISA, and seafood tissue variety significantly affected MC detection. This is the first known study to use DM ELISA for tissue analyses, and our findings demonstrate that DM ELISA combined with a short solvent extraction results in fewer false positives than other commonly used methods. This method can be used for rapid and reliable MC detection in seafood.

Effects of hypolimnetic oxygen addition on mercury bioaccumulation in Twin Lakes, Washington, USA

Twin Lakes, located on the Confederated Tribes of the Colville Indian Reservation in eastern Washington, USA, include North Twin Lake (NT) and South Twin Lake (ST). The mesotrophic, dimictic lakes are important recreational fishing sites for both warm-water bass and cold-water trout. To improve summertime cold-water habitat for trout in NT, dissolved oxygen (DO) addition to the hypolimnion, using liquid oxygen as an oxygen gas source, started in 2009. This study assessed mercury (Hg) in the water column, zooplankton and fish, and related water quality parameters, in Twin Lakes from 2009 to 2012. Because methylmercury (MeHg) buildup in lake bottom water is commonly associated with hypolimnetic anoxia, hypolimnetic oxygenation was hypothesized to reduce Hg in bottom waters and biota in NT relative to ST. Oxygen addition led to significantly higher DO (mean hypolimnetic DO: 2-8 mg/L versus <1 mg/L) and lower MeHg (peak mean hypolimnetic MeHg: 0.05-0.2 ng/L versus 0.15-0.4 ng/L) in North Twin. In North Twin, years with higher DO (2009 and 2011) exhibited lower MeHg in bottom waters and lower total Hg in zooplankton, inferring a positive linkage between oxygen addition and lower bioaccumulation. However, when comparing between the two lakes, Hg levels were significantly higher in zooplankton (total Hg range: 100-200 versus 50-100 μg/kg dry weight) and trout (spring 2010 stocking cohort of eastern brook trout mean total Hg: 74.9 versus 49.9 μg/kg wet weight) in NT relative to ST. Lower Hg bioaccumulation in ST compared to NT may be related to bloom dilution in chlorophyll-rich bottom waters, a vertical disconnect between the location of zooplankton and MeHg in the water column, and high binding affinity between sulfide and MeHg in bottom waters.

Using stable isotopes and a multiple-source mixing model to evaluate fish dietary niches in a mesotrophic lake

Abstract Christensen, D.R. and B.C. Moore. 2009. Using stable isotopes and a multiple-source mixing model to evaluate fish dietary niches in a mesotrophic lake. Lake Reserv. Manage. 25:167–175. We used stable isotope analysis (SIA) of δ13C and δ15N and a multiple-source mixing model to evaluate dietary niches within the Twin Lakes, Washington, fish community to identify potential for exploitative competition, resource partitioning, and predation. The SIA revealed distinct spatial feeding niches; pelagic species were δ13C depleted, while littoral organisms were δ13C enriched. Trophic feeding niches were identified from δ15N enrichment with each successive trophic level. We found δ15N progression with increasing largemouth bass size, suggesting ontogenetic diet variability. Model results suggested that the smaller bass (i.e., ⩽299 mm length) fed principally on golden shiner, crayfish, and macroinvertebrates while larger bass (⩾300 mm) primarily consumed brook trout and golden shiner. Isotopic signatures for golden shiner were intermediary, indicating both pelagic and littoral feeding sources, including phantom midges (nocturnal and pelagic) and damselflies (littoral) as principal diet sources, suggesting possible horizontal diel migration in golden shiner. Pelagic zooplankton was indicated as the most important food source for rainbow trout. Food resources appeared to be partitioned among the Twin Lakes fish community, possibly limiting competitive interactions. Piscivory in largemouth bass was focused on golden shiner and brook trout, suggesting possible top-down regulation of lower trophic levels. Stable isotope analysis and multiple-source mixing models are useful tools that can improve lake and fishery management decisions by providing data on food web dynamics such as competition, resource partitioning, and predation in lakes.