Description of Use in Document

Main Reasons:

1. 
   Given the multiple potential interactions in this study that could contribute to either a direct or indirect effect, this study was not considered sufficient for use as a threshold value.
   
2. 
   It is unclear if populations of zooplankton and algae were consistent between treatments when added to tanks
   

Other Reasons:

1. The source of the test organism were not reported, prior exposure to potential contaminants is not known;

2) Based on the paper, it appears that some of the frogs collected prior to the pond drying were not completely metamorphosed, but had at least one forelimb, and were retained until they did complete metamorphosis. It is unclear how many frogs were retained in this manner and the potential effect this secondary container may have had on mass and time to metamorphosis.

Hua, J. and R.A. Relyea. 2012. East Coast vs West Coast: effects of an insecticide in communities containing different amphibian assemblages. Freshwater Sci. 31 (3): 787-799.

Two geographically distinct amphibian assemblages, Rana sylvatica (PA) or Rana cascadae (OR) were exposed to malathion along with peri- and phytoplankton and zooplankton in the presence or absence of a zooplankton predator (larval salamanders, Ambystoma gracile (PA) and Ambystoma laterale (OR)) in aquatic mesocosms (approx. 545L well water). Amphibians and salamanders eggs were collected from natural ponds and wetlands and allowed to hatch on-site. Pond water was collected and invertebrate predators were removed and equal aliquots were added to each mesocosm along with 200 g dry leaves (primarily Quercus spp.). Algae and zooplankton communities were in the cosms 15 days prior to addition of amphibians or malathion treatment. Twenty amphibian larvae and 10 salamanders were added to each mesocosm (initial mass ± SE: wood frog = 208 ± 11 mg, Cascades frogs = 194 ± 12 mg; spotted salamander = 103 ± 8 mg; northwestern salamanders = 101 ± 9 mg). Malathion (Malathion Plus (50%)) was applied to the mesocosms at a concentration of either 1 or 10 µg/L malathion; a control group was also included. However, after analysis, the measured concentration of the 10 µg/L group was 1 µg/L (the sample for the nominal treatment group of 1 µg/L was lost in transit). Additionally, the zooplankton in this treatment did not appear affected, therefore, on day 10, malathion was re-applied to the cosms at 5 and 50 µg/L. Chemical analysis of samples collected 3 hours after application indicated measured concentrations of 6 and 40 µg/L, respectively. Malathion was not detected in the well water used in previous tests. On test day 22, temperature, pH, dissolved oxygen and light attenuation were measured. Also on day 22, zooplankton was collected (0.2L tube sampler at 5 different locations in mesocosms, pooled, and screened) and total abundance was calculated in terms of cladocerans or copepods. Phytoplankton and periphyton abundance were measured on day 22 (phytoplankton: 500mL water, filtered and chlorophyll a concentrations measured; periphyton: removed from tiles, filtered and dry weight measured). Beginning on day 16 (first observance of a metamorph) until day 40, cosms were checked daily for metamorphs (removed when both forelimbs had emerged and tail was <3 cm). The removed frogs were placed in 1L tubs with moss until complete tail resorption (GS 46). The study was terminated on day 40 and any remaining amphibians that had forelimbs were allowed to complete metamorphosis. For the amphibians, survival, time to metamorphosis and body mass were analyzed. Only two salamanders had completed metamorphosis by day 40 and therefore body mass only was measured. Multivariate analysis of variance (MANOVA) was used to evaluate control and treatment groups to test for effects of malathion, amphibian assemblage and presence/absence of salamanders.

Light attenuation was increased at the 40 µg/L treatments compared to control. Results for biotic variables are presented below in Figures 1 and 2 (Figures 3 and 4 in paper);magnitude of effects in this review are approximations based on Figure 3 in the paper. After 22 days, copepod abundance was greater (approx. 60-70%) in the 6 µg/L treatment group compared to controls, and cladoceran abundance was lower (abundance approx. 0%) in both malathion treatment groups compared to control. Additionally, periphyton biomass was significantly lower (approx. 20-70%) at 40 µg/L compared to control, and phytoplankton biomass was greater (>100%) in both malathion treatments. Amphibian survival was high across the treatments: 97.1% in wood frogs and 99.4% in Cascades frogs. The mass of amphibian metamorphs was significantly greater (approx. 30%) in both species compared to control, but time to metamorphosis was not affected. Salamander mass was also significantly lower in both treatments (approx. 30-70%).

Figure 1 (as presented as Figure 3 in paper). Effects on Zooplankton, Periphyton and Phytoplankton.

Figure 2 (Figure 4 in paper). Effects on Amphibians and Salamanders

Main Reasons:

1. 
   Given the multiple potential interactions in this study that could contribute to either a direct or indirect effect, this study was not considered sufficient for use as a threshold value.
   
2. 
   It is unclear if populations of zooplankton and algae were consistent between treatments when added to tanks.
   
3. 
   
   

1) Based on paper, it appears that frogs still remaining on day 40, that were not completely metamorphosed, but had forelimbs were retained in 1L plastic containers until they did complete metamorphosis. It is unclear how many frogs were retained in this manner and the potential effect this secondary container may have had on mass and time to metamorphosis;

2) The concentration of malathion was increased in the study on Day 10 due to the low recovery of the first application and the lack of response in zooplankton. It is not known how this first application may have impact the other endpoints/taxa in the study;

3) As organisms were field collected, prior exposure to potential contaminants is not known.

Hansen, D., and P. Parrish. 1977. Suitability of sheepshead minnows (Cyprinodon variegatus) for life-cycle toxicity tests In: F. Mayer and J. Hamelink (Eds.), Aquatic Toxicology and Hazard Evaluation, 1st Symposium, ASTM STP 634, Philadelphia, PA 117-126. E5074

January 15, 2015

The information contained in Hansen and Parrish (1977) contains limited summary data. Additional information (e.g., test concentration summary data) is reported in the citation below and was used in preparing this review:

In the acute study, the mean measured test concentrations were 72-95% of nominal and were 100-143% of nominal in the chronic study. The 96-hr acute LC50 value was 51 µg/L (95% CI 41-63) at a salinity of 20 ppt and 29°C.

1. 
   While the size of the parental fish used in the acute and chronic assay were reported, specific age classes were not.
   
2. 
   The range in salinity was quite variable, and since the reported average and range were for two chemicals, the specific range for malathion is uncertain.
   
3. 
   This study was conducted prior to effects to reduce toxic impurities in the technical grade test material which may have impacted the results of the test
   

Amy Blankinship, ERB6

Webb CM and D.A. Crain. 2006. Effects of Ecologically Relevant Doses of Malathion on Developing Xenopus laevis Tadpoles. Bios 77(1): 1. E118382.