Seal Slough: toxic algae advisories
Seal Slough, San Mateo County. See all San Mateo County waters.
What the state's records say
Caution advisory, last posted Jul 1, 2021. No all-clear recorded.
Reporting is voluntary, so the state may not have recorded an end even if conditions changed. Check posted signs and the official map.
What this level asks: Algae that can make toxins may be present. Keep people, children and pets away from algae and scum, and do not let pets drink the water.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Seal Slough
The state has an advisory on file for Seal Slough (Caution advisory), last posted Jul 1, 2021, and no all-clear recorded. Keep your dog out of the water and away from scum on the shore until the state records an end.
Reported spots
The state records each report at a spot, such as a beach or a boat ramp. Each spot's latest deciding record:
| Spot | Status |
|---|---|
| Seal Slough Marina Lagoon Parkside Aquatic Park | The state's latest record, from Jun 27, 2024, recommends no advisory. |
| near Parkside Aquatic Park | The state recorded an end date of Dec 31, 2022. |
| South end | Caution advisory, last posted Jul 1, 2021. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Seal Slough, newest first. "None" is the state's record that no advisory was recommended on that date. "NA" records do not change a status.
| Date | Spot | State's level | Notes |
|---|---|---|---|
| Jun 27, 2024 | Seal Slough Marina Lagoon Parkside Aquatic Park | None | Advisory based on visual and toxins |
| Jun 29, 2023 | near Parkside Aquatic Park | Caution | End date recorded: Dec 31, 2022. Testing results below posting triggers |
| Jun 19, 2023 | Seal Slough Marina Lagoon Parkside Aquatic Park | Algal mat alert sign | Advisory based on visual and toxins |
| Jun 19, 2023 | Seal Slough Marina Lagoon Parkside Aquatic Park | Caution | Advisory based on visual and toxins |
| May 18, 2023 | Seal Slough Marina Lagoon Parkside Aquatic Park | Caution | Floating/planktonic bloom observed |
| May 18, 2023 | Seal Slough Marina Lagoon Parkside Aquatic Park | Caution | Floating/planktonic bloom observed |
| May 18, 2023 | Seal Slough Marina Lagoon Parkside Aquatic Park | Blank in the state's file | Floating/planktonic bloom observed |
| Aug 30, 2022 | near Parkside Aquatic Park | None | End date recorded: Dec 31, 2022. Testing results below posting triggers |
| Aug 30, 2022 | near Parkside Aquatic Park | None | Testing results below posting triggers |
| Jun 29, 2022 | near Parkside Aquatic Park | None | Testing results below posting triggers |
| May 20, 2022 | near Parkside Aquatic Park | None | Testing results below posting triggers |
| May 20, 2022 | near Parkside Aquatic Park | None | Testing results below posting triggers |
| Jul 1, 2021 | South end | Caution | visual monitoring based advisory |
Source
Advisory data: California State Water Resources Control Board, Freshwater Harmful Algal Bloom Program, via data.ca.gov (public domain). Advisories are recommendations; reporting is voluntary and incomplete. The state's data. An advisory ends only when the state records a later "None" (no advisory recommended) at the same spot, or an end date. A blank end date is unknown.