Acute Toxicity of the Lampricide 4-Nitro-3-(trifluoromethyl)phenol to the Mussel (Obovaria subrotunda), Its Host (Percina maculata), and a Surrogate Mussel Species (Obovaria olivaria).

The risk of lampricide applications (such as 4-nitro-3-[trifluoromethyl]phenol [TFM]) to nontarget fauna continues to be a concern within the Great Lakes Fishery Commission Sea Lamprey Control Program, especially among imperiled aquatic species-such as native freshwater mussels. The Grand River (Ohio, USA) is routinely treated for larval sea lampreys (Petromyzon marinus), and this river contains populations of the federally threatened mussel Obovaria subrotunda. Given this spatial overlap, information on the sensitivity of O. subrotunda to TFM is needed. Our objectives were to assess the toxicity of TFM to (1) adult Obovaria olivaria (a surrogate for O. subrotunda), (2) glochidial larvae of O. olivaria and O. subrotunda, (3) juveniles of O. olivaria and O. subrotunda, and (4) adult Percina maculata (host for O. subrotunda glochidia). In acute toxicity tests, TFM was not toxic to glochidia and adult mussels at exposure concentrations that exceed typical treatment rates. Although significant dose-response relationships were observed in hosts and juveniles, survival was ≥95% (Percina maculata), ≥93% (O. olivaria), and ≥74% (O. subrotunda) at typical treatment rates. However, the steep slope of these dose-response relationships indicates that an approximately 20% difference in the treatment level can result in nearly an order of magnitude difference in survival. Collectively, these data indicate that routine sea lamprey control operations are unlikely to acutely affect these species or their host. However, given that many mussel species are long-lived (30-100 years), the risks posed by lampricide treatments in the Great Lakes would be further informed by research on the potential long-term effects of lampricides on imperiled species. Environ Toxicol Chem 2024;43:1423-1430. Published 2024. This article is a U.S. Government work and is in the public domain in the USA.

Effect of imperfect detectability on adaptive and conventional sampling: simulated sampling of freshwater mussels in the upper Mississippi River.

Adaptive sampling designs are recommended where, as is typical with freshwater mussels, the outcome of interest is rare and clustered. However, the performance of adaptive designs has not been investigated when outcomes are not only rare and clustered but also imperfectly detected. We address this combination of challenges using data simulated to mimic properties of freshwater mussels from a reach of the upper Mississippi River. Simulations were conducted under a range of sample sizes and detection probabilities. Under perfect detection, efficiency of the adaptive sampling design increased relative to the conventional design as sample size increased and as density decreased. Also, the probability of sampling occupied habitat was four times higher for adaptive than conventional sampling of the lowest density population examined. However, imperfect detection resulted in substantial biases in sample means and variances under both adaptive sampling and conventional designs. The efficiency of adaptive sampling declined with decreasing detectability. Also, the probability of encountering an occupied unit during adaptive sampling, relative to conventional sampling declined with decreasing detectability. Thus, the potential gains in the application of adaptive sampling to rare and clustered populations relative to conventional sampling are reduced when detection is imperfect. The results highlight the need to increase or estimate detection to improve performance of conventional and adaptive sampling designs.

Lethal and sublethal effects of ammonia to juvenile Lampsilis mussels (Unionidae) in sediment and water-only exposures.

We compared the sensitivity of two juvenile unionid mussels (Lampsilis cardium and Lampsilis higginsii) to ammonia in 96-h water-only and sediment tests by use of mortality and growth measurements. Twenty mussels were placed in chambers buried 2.5 cm into reference sediments to approximate pore-water exposure (sediment tests) or elevated above the bottom of the experimental units (water-only tests). In the sediment tests, a pH gradient existed between the overlying water (mean 8.0), sediment- water interface (mean 7.7), and 2.5 cm depth (mean 7.4). We assumed that mussels were exposed to ammonia in pore water and report effect concentrations in pore water, but if they were exposed to the higher pH water, more of the ammonia would be in the toxic un-ionized (NH(3)) form. The only differences in toxicity and growth between mussel species occurred in some of the water-only tests. In sediment tests, median lethal concentrations (LC50s) ranged from 124 to 125 microg NH(3)-N/L. In water-only tests, LC50s ranged from 157 to 372 microg NH(3)-N/L. In sediment tests, median effective concentrations (EC50s based on growth) ranged from 30 to 32 microg NH(3)-N/L. Juvenile mussels in the water-only tests grew poorly and did not exhibit a dose-response relation. These data demonstrate that growth is a sensitive and valuable endpoint for studies on ammonia toxicity with juvenile freshwater mussels and that growth should be measured via sediment tests.

Intra- and interlaboratory variability in acute toxicity tests with glochidia and juveniles of freshwater mussels (Unionidae).

The present study evaluated the performance and variability in acute toxicity tests with glochidia and newly transformed juvenile mussels using the standard methods outlined in American Society for Testing and Materials (ASTM). Multiple 48-h toxicity tests with glochidia and 96-h tests with juvenile mussels were conducted within a single laboratory and among five laboratories. All tests met the test acceptability requirements (e.g., >or=90% control survival). Intralaboratory tests were conducted over two consecutive mussel-spawning seasons with mucket (Actinonaias ligamentina) or fatmucket (Lampsilis siliquoidea) using copper, ammonia, or chlorine as a toxicant. For the glochidia of both species, the variability of intralaboratory median effective concentrations (EC50s) for the three toxicants, expressed as the coefficient of variation (CV), ranged from 14 to 27% in 24-h exposures and from 13 to 36% in 48-h exposures. The intralaboratory CV of copper EC50s for juvenile fatmucket was 24% in 48-h exposures and 13% in 96-h exposures. Interlaboratory tests were conducted with fatmucket glochidia and juveniles by five laboratories using copper as a toxicant. The interlaboratory CV of copper EC50s for glochidia was 13% in 24-h exposures and 24% in 48-h exposures, and the interlaboratory CV for juveniles was 22% in 48-h exposures and 42% in 96-h exposures. The high completion success and the overall low variability in test results indicate that the test methods have acceptable precision and can be performed routinely.

Simulated mussel mortality thresholds as a function of mussel biomass and nutrient loading.

A freshwater "mussel mortality threshold" was explored as a function of porewater ammonium (NH4+) concentration, mussel biomass, and total nitrogen (N) utilizing a numerical model calibrated with data from mesocosms with and without mussels. A mortality threshold of 2 mg-N L-1 porewater NH4+ was selected based on a study that estimated 100% mortality of juvenile Lampsilis mussels exposed to 1.9 mg-N L-1 NH4+ in equilibrium with 0.18 mg-N L-1 NH3. At the highest simulated mussel biomass (560 g m-2) and the lowest simulated influent water "food" concentration (0.1 mg-N L-1), the porewater NH4+ concentration after a 2,160 h timespan without mussels was 0.5 mg-N L-1 compared to 2.25 mg-N L-1 with mussels. Continuing these simulations while varying mussel biomass and N content yielded a mortality threshold contour that was essentially linear which contradicted the non-linear and non-monotonic relationship suggested by Strayer (2014). Our model suggests that mussels spatially focus nutrients from the overlying water to the sediments as evidenced by elevated porewater NH4+ in mesocosms with mussels. However, our previous work and the model utilized here show elevated concentrations of nitrite and nitrate in overlying waters as an indirect consequence of mussel activity. Even when the simulated overlying water food availability was quite low, the mortality threshold was reached at a mussel biomass of about 480 g m-2. At a food concentration of 10 mg-N L-1, the mortality threshold was reached at a biomass of about 250 g m-2. Our model suggests the mortality threshold for juvenile Lampsilis species could be exceeded at low mussel biomass if exposed for even a short time to the highly elevated total N loadings endemic to the agricultural Midwest.

Evaluation of the short term 12 hour toxicity of 3-trifluoromethyl-4-nitrophenol (TFM) to multiple life stages of Venustaconcha ellipsiformis and Epioblasma triquetra and its host fish (Percina caprodes).

The present study evaluated the risk of 12-h exposures of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) to multiple life stages of the federally endangered snuffbox (Epioblasma triquetra) and its primary host fish the common logperch (Percina caprodes) as well as a surrogate to the snuffbox, the ellipse (Venustaconcha ellipsiformis). Life stages examined included free glochidia, 1-wk juveniles, and adults of the ellipse; free glochidia, glochidia on host fish, and 1-wk juveniles of the snuffbox; and adult logperch. Larval sea lampreys were also tested alongside adult ellipse and logperch for direct comparison. Survival exceeded 82% among all life stages in both mussel species at levels up to 1.8 times what would be applied during treatments, suggesting that routine sea lamprey control operations would not adversely affect mussels. However, substantial mortality of adult logperch was observed at TFM concentrations typically applied to streams, and loss of host fish could adversely affect snuffbox reproduction. In addition, TFM had no significant effect on the number of glochidia that metamorphosed on adult logperch. Although the snuffbox is not likely to be acutely affected from sea lamprey control operations, mitigation efforts to minimize impacts to the host fish should be considered.

Effects of ammonia on juvenile unionid mussels (Lampsilis cardium) in laboratory sediment toxicity tests.

Ammonia is a relatively toxic compound generated in water and sediments by heterotrophic bacteria and accumulates in sediments and pore water. Recent data suggest that unionid mussels are sensitive to un-ionized ammonia (NH3) relative to other organisms. Existing sediment exposure systems are not suitable for ammonia toxicity studies with juvenile unionids; thus, we modified a system to expose juveniles to ammonia that was continuously infused into sediments. This system maintained consistent concentrations of ammonia in pore water up to 10 d. Juvenile Lampsilis cardium mussels were exposed to NH3 in pore water in replicate 96-h and 10-d sediment toxicity tests. The 96-h median lethal concentrations (LC50s) were 127 and 165 microg NH3-N/L, and the 10-d LC50s were 93 and 140 microg NH3-N/L. The median effective concentrations (EC50s) (based on the proportion affected, including dead and inactive mussels) were 73 and 119 microg NH3-N/L in the 96-h tests and 71 and 99 microg NH3-N/L in the 10-d tests. Growth rate was substantially reduced at concentrations between 31 and 76 microg NH3-N/L. The lethality results (when expressed as total ammonia) are about one-half the acute national water quality criteria for total ammonia, suggesting that existing criteria may not protect juvenile unionids.

Effects of pore-water ammonia on in situ survival and growth of juvenile mussels (Lampsilis cardium) in the St. Croix Riverway, Wisconsin, USA.

We conducted a series of in situ tests to evaluate the effects of pore-water ammonia on juvenile Lampsilis cardium in the St. Croix River (WI, USA). Threats to this river and its associated unionid fauna have accelerated in recent years because of its proximity to Minneapolis-St. Paul, Minnesota, USA. In 2000, caged juveniles were exposed to sediments and overlying water at 12 sites for 10 d. Survival and growth of juveniles was significantly different between sediment (mean, 47%) and water column (mean, 86%) exposures; however, these effects were unrelated to pore-water ammonia. During 2001, juveniles were exposed to sediments for 4, 10, and 28 d. Pore-water ammonia concentrations ranged from 0.3 to 62.0 microg NH3-N/L in sediments and from 0.5 to 140.8 microg NH3-N/L within exposure chambers. Survival (mean, 45, 28, and 41% at 4, 10, and 28 d, respectively) and growth (range, 3-45 microm/d) of juveniles were highly variable and generally unrelated to ammonia concentrations. Although laboratory studies have shown unionids to be quite sensitive to ammonia, further research is needed to identify the route(s) of ammonia exposure in unionids and to understand the factors that contribute to the spatial variability of ammonia in rivers.

Environmental occurrence and reproductive effects of the pharmaceutical fluoxetine in native freshwater mussels.

The present study measured the occurrence, distribution, and bioaccumulation of fluoxetine in samples of water, polar organic chemical integrative sampler (POCIS), sediment, and caged freshwater mussels at stream sites near a municipal wastewater treatment facility effluent discharge. We assessed the relation of the environmental concentrations to reproductive endpoints in mussels in acute laboratory tests. Concentrations of fluoxetine in water and POCIS samples were similar (<20% difference) within each site and were greatest in the effluent channel (104-119 ng/L), and decreased at 50 m and 100 m downstream. Likewise, concentrations of fluoxetine in sediment and mussel (Elliptio complanata) tissue were greatest in the effluent channel (17.4 ng/g wet wt for sediment and 79.1 ng/g wet wt for mussels). In 96-h lab tests, fluoxetine significantly induced parturition of nonviable larvae from female E. complanata exposed to 300 microg/L (p = 0.0118) and 3,000 microg/L (p < 0.0001) compared to controls. Fluoxetine exposure at 300 microg/L (p = 0.0075) and 3,000 microg/L (p = 0.0001) also resulted in stimulation of lure display behavior in female Lampsilis fasciola and Lampsilis cardium, respectively. In male E. complanata, 3,000 microg fluoxetine/L significantly induced release of spermatozeugmata during a 48-h exposure. These results suggest that fluoxetine accumulates in mussel tissue and has the potential to disrupt several aspects of reproduction in freshwater mussels, a faunal group recognized as one of the most imperiled in the world. Despite the disparity between measured environmental concentrations of fluoxetine and effects concentrations in our short-term tests with these long-lived animals, additional tests are warranted to evaluate the effects of long-term exposure to environmentally relevant concentrations and critical lifestages (e.g., juveniles).