6 Rotenone monitoring
Rotenone application was performed in early October 2021 by ADF&G staff. The treated bodies of water included Vogel Lake, North Vogel Lake, and Miller Creek. ADF&G collected pre and post-treatment water samples as part of the treatment event, and Kenai Watershed Forum monitored degradation through Summer 2022 when levels fell to undetectable.
Field sampling and analytical methods generally followed those described in Couture et al. 20222. Prior to rotenone treatment, we collected a composite grab sample from two locations at a depth of 0.5 m near the center of each lake. Following treatment, we collected lake water samples at a depth of 0.5 m from two locations around the center of the lake either as a grab sample or with a Kemmerer sampler. For each strata of each lake, a single composite sample was created from the two locations. For benthic samples, the Kemmerer sampler was lowered to a depth within 2 m from the bottom in the same two locations around the center of the lake. The collected water from two locations was then combined into a single 1 L composite sample. All samples were collected into sterilized 1 L amber glass bottles, immediately chilled on ice, stored out of the light and transported to the Applied Science, Engineering and Technology (ASET) Lab located at the University of Alaska Anchorage (UAA) within 72 h of collection. Upon arrival to the lab all samples were stored in the dark at 4°C and analyzed via high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) within seven days of collection.
6.1 Sampling schedule
The rotenone sampling schedule is described in table 6.1 or may be accessed in a Google Sheet linked here: https://tinyurl.com/8ba94nrn. The schedule is current as of 2022-11-29.
| Field Sample Count | Sample | Field Sample Date | Status | Location | Depth | Notes |
|---|---|---|---|---|---|---|
| 1 | Rotenone | 2021-09-27 | Complete | Vogel Lake | Surface | Pre-treatment |
| 1 | Rotenone | 2021-09-28 | Complete | North Vogel Lake | Surface | Pre-treatment |
| 1 | Rotenone | 2021-10-07 | Complete | Vogel Lake | Surface | |
| 1 | Rotenone | 2021-10-07 | Complete | Vogel Lake | Benthic | |
| 1 | Rotenone | 2021-10-07 | Complete | North Vogel Lake | Surface | |
| 1 | Rotenone | 2021-10-07 | Complete | North Vogel Lake | Benthic | |
| 1 | Rotenone | 2021-10-08 | Complete | Miller Creek Head | Surface | |
| 1 | Rotenone | 2021-11-10 | Complete | Miller Creek Weir | Surface | |
| 1 | Rotenone | 2021-11-10 | Complete | North Vogel Lake | Surface | Alternative sampling location due to thin ice |
| 1 | Rotenone | 2021-11-10 | Complete | Vogel Lake | Surface | Alternative sampling location due to thin ice |
| 1 | Rotenone | 2021-12-03 | Complete | Miller Creek | Surface | |
| 1 | Rotenone | 2021-12-02 | Complete | North Vogel Lake | Surface | |
| 1 | Rotenone | 2021-12-02 | Complete | Vogel Lake | Surface | |
| 1 | Rotenone | 2021-12-03 | Complete | Miller Creek | Benthic | |
| 1 | Rotenone | 2021-12-02 | Complete | North Vogel Lake | Benthic | |
| 1 | Rotenone | 2021-12-02 | Complete | Vogel Lake | Benthic | |
| 1 | Rotenone | 2022-01-05 | Complete | Miller Creek | Surface | |
| 1 | Rotenone | 2022-01-05 | Complete | North Vogel Lake | Surface | |
| 1 | Rotenone | 2022-01-05 | Complete | Vogel Lake | Surface | |
| 1 | Rotenone | 2022-02-04 | Complete | North Vogel Lake | Benthic | |
| 1 | Rotenone | 2022-02-04 | Complete | North Vogel Lake | Surface | |
| 1 | Rotenone | 2022-02-04 | Complete | Vogel Lake | Surface | Surface location A |
| 1 | Rotenone | 2022-02-04 | Complete | Vogel Lake | Surface | Surface location B |
| 1 | Rotenone | 2022-03-11 | Complete | North Vogel Lake | Benthic | |
| 1 | Rotenone | 2022-03-11 | Complete | North Vogel Lake | Surface |
6.2 Rotenone sampling map
Click the image above to access the online map at https://arcg.is/199PPj. The map layer titled “Rotenone Sampling” contains interactive click-able points with sampling details including coordinates.
6.3 Rotenone concentration results
6.3.1 Sample results
6.3.1.1 Tables
Laboratory analysis of water samples is performed by the ASET Laboratory at the University of Alaska Anchorage Department of Chemistry in Anchorage, Alaska. Detailed analytical methods can be found in Couture et al. 2022.
Original results received from UAA are available for download at the following link:
A table of final results that have been integrated into a single dataframe and reshaped to a “long” format are available for download at the the following link:
A summarised version of the above downloadable table is displayed in Table 6.2. Values shown in Table 6.2 are averages of duplicate lab values (overall mean percent difference = 1.25 ± 2.44 %, mean ± SD).
| sample_name | field_sample_date | waterbody | strata | rotenone_ppb | detection_note |
|---|---|---|---|---|---|
| Miller Creek Weir | 2021-11-10 | Miller_Creek | Creek | 2.010 | |
| Miller_Creek_1 | 2021-10-08 | Miller_Creek | Creek | 22.960 | |
| Miller_Creek_2 | 2021-12-03 | Miller_Creek | Creek | 6.585 | |
| Miller_Creek_2 | 2022-01-05 | Miller_Creek | Creek | 0.000 | value <0.5 ppb |
| N_Vogel_Benthic | 2021-10-07 | N_Vogel_Lake | Benthic | 13.605 | |
| N_Vogel_Benthic | 2021-12-02 | N_Vogel_Lake | Benthic | 12.280 | |
| N_Vogel_Benthic | 2022-01-05 | N_Vogel_Lake | Benthic | 8.755 | |
| N_Vogel_Benthic | 2022-02-02 | N_Vogel_Lake | Benthic | 0.000 | Not_Detected |
| N_Vogel_Benthic | 2022-03-11 | N_Vogel_Lake | Benthic | 0.000 | Not_Detected |
| N_Vogel_Surface | 2021-09-28 | N_Vogel_Lake | Surface | 0.000 | Not_Detected |
| N_Vogel_Surface | 2021-10-07 | N_Vogel_Lake | Surface | 26.900 | |
| N_Vogel_Surface | 2021-11-10 | N_Vogel_Lake | Surface | 15.335 | |
| N_Vogel_Surface | 2021-12-02 | N_Vogel_Lake | Surface | 13.710 | |
| N_Vogel_Surface | 2022-01-04 | N_Vogel_Lake | Surface | 9.000 | |
| N_Vogel_Surface | 2022-02-02 | N_Vogel_Lake | Surface | 8.765 | |
| N_Vogel_Surface | 2022-03-11 | N_Vogel_Lake | Surface | 0.000 | Not_Detected |
| Vogel_Benthic | 2021-10-07 | Vogel_Lake | Benthic | 18.555 | |
| Vogel_Benthic | 2021-12-02 | Vogel_Lake | Benthic | 10.715 | |
| Vogel_Benthic | 2022-01-05 | Vogel_Lake | Benthic | 0.000 | Not_Detected |
| Vogel_Surface | 2021-09-27 | Vogel_Lake | Surface | 0.000 | Not_Detected |
| Vogel_Surface | 2021-10-07 | Vogel_Lake | Surface | 25.355 | |
| Vogel_Surface | 2021-11-10 | Vogel_Lake | Surface | 12.735 | |
| Vogel_Surface | 2021-12-02 | Vogel_Lake | Surface | 8.810 | |
| Vogel_Surface | 2022-01-05 | Vogel_Lake | Surface | 0.000 | Not_Detected |
| Vogel_Surface | 2022-02-02 | Miller_Creek | Creek | 0.000 | Not_Detected |
6.3.1.2 Figures
Figure 6.1: Average rotenone concentrations in Vogel Lake and North Vogel Lake, Fall 2021 through Spring 2022.
Note on Miller Creek results:
- Rotenone values for Miller Creek are not shown in a continuous time series figure due to more limited sample results from varying locations. See Table 6.2 for results from Miller Creek.