Lake Merritt: toxic algae advisories
Lake Merritt, Alameda County. See all Alameda County waters.
What the state's records say
Caution advisory, last posted Jun 5, 2025. No all-clear recorded.
7 reported spots here have an advisory with 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 Lake Merritt
The state has an advisory on file for Lake Merritt (Caution advisory), last posted Jun 5, 2025, 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 |
|---|---|
| at Lakeshore Ave. near Chalet (204LME010) | The state's latest record, from Oct 7, 2026, recommends no advisory. |
| Lake Merritt Boating Center (204LME025) | The state's latest record, from Oct 7, 2026, recommends no advisory. |
| Rocky Shore Nature Center (204LME200) | The state's latest record, from Aug 28, 2025, recommends no advisory. |
| Lakeside Park | Caution advisory, last posted Jun 5, 2025. No all-clear recorded. |
| Glen Echo arm | The state's latest record, from Mar 19, 2024, recommends no advisory. |
| Lake Merritt at Bandstand Beach | The state's latest record, from Sep 7, 2023, recommends no advisory. |
| Rotary Nature Center | The state's latest record, from Nov 28, 2022, recommends no advisory. |
| Lake Merritt Boating Center | Caution advisory, last posted Sep 16, 2022. No all-clear recorded. |
| Lake Merritt Ampitheater | Caution advisory, last posted Sep 16, 2022. No all-clear recorded. |
| Lake Merritt at Lakeshore Ave. near Boden Way | Caution advisory, last posted Sep 16, 2022. No all-clear recorded. |
| Lake Merritt at beach south of Edoff Memorial Bandstand | Caution advisory, last posted Aug 30, 2022. No all-clear recorded. |
| Lake Merritt shoreline between 1200 and 1400 Lakeshore Avenue | Caution advisory, last posted Aug 8, 2022. No all-clear recorded. |
| Near Light Post 82 and Cleveland Cascade at Lake Shore Ave. | Caution advisory, last posted May 19, 2022. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Lake Merritt, 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 |
|---|---|---|---|
| Oct 7, 2026 | at Lakeshore Ave. near Chalet (204LME010) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Oct 7, 2026 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Sep 4, 2026 | at Lakeshore Ave. near Chalet (204LME010) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Sep 4, 2026 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Jul 2, 2026 | at Lakeshore Ave. near Chalet (204LME010) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Jul 2, 2026 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Jun 5, 2026 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Jun 5, 2026 | at Lakeshore Ave. near Chalet (204LME010) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Nov 20, 2025 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Nov 20, 2025 | at Lakeshore Ave. near Chalet (204LME010) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Oct 8, 2025 | at Lakeshore Ave. near Chalet (204LME010) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Oct 8, 2025 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Aug 28, 2025 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Aug 28, 2025 | Rocky Shore Nature Center (204LME200) | None | Updates from routine monitoring program-organization |
| Jul 30, 2025 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Jul 30, 2025 | at Lakeshore Ave. near Chalet (204LME010) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Jun 27, 2025 | Rocky Shore Nature Center (204LME200) | None | Updates from routine monitoring program-organization |
| Jun 27, 2025 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Jun 27, 2025 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Jun 5, 2025 | Lakeside Park | Caution | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Jun 5, 2025 | Lake Merritt Boating Center (204LME025) | Caution | Updates from routine monitoring program-organization |
| Nov 8, 2024 | at Lakeshore Ave. near Chalet (204LME010) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Nov 8, 2024 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Oct 4, 2024 | Lakeside Park | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Oct 4, 2024 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Aug 28, 2024 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Aug 28, 2024 | at Lakeshore Ave. near Chalet (204LME010) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Aug 28, 2024 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| Jul 5, 2024 | Lake Merritt Boating Center (204LME025) | None | Updates from routine monitoring program-organization |
| May 31, 2024 | Lake Merritt Boating Center (204LME025) | None | Advisory based on visual and toxins; Updates from routine monitoring program-organization |
| May 31, 2024 | Lakeside Park | None | Testing results below posting triggers; Updates from routine monitoring program-organization |
| Apr 9, 2024 | Lake Merritt Boating Center (204LME025) | Caution | Lake-wide advisory |
| Mar 19, 2024 | Glen Echo arm | None | De-posting advisory. |
| Mar 15, 2024 | Glen Echo arm | Caution | Floating/planktonic bloom observed |
| Mar 15, 2024 | Lake Merritt Boating Center (204LME025) | None | Posted general awareness |
| Mar 7, 2024 | Lake Merritt Boating Center (204LME025) | NA - refer to Report Details | Marine bloom suspected (red tide); Suspected bloom, investigation ongoing |
| Mar 7, 2024 | Lake Merritt Boating Center (204LME025) | NA - refer to Report Details | Marine bloom suspected (red tide); Suspected bloom, investigation ongoing |
| Mar 7, 2024 | Lake Merritt Boating Center (204LME025) | None | Marine bloom suspected (red tide); Suspected bloom, investigation ongoing |
| Nov 9, 2023 | at Lakeshore Ave. near Chalet (204LME010) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Nov 9, 2023 | Lake Merritt Boating Center (204LME025) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Oct 12, 2023 | at Lakeshore Ave. near Chalet (204LME010) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Oct 12, 2023 | Lake Merritt Boating Center (204LME025) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Sep 7, 2023 | Lake Merritt at Bandstand Beach | None | Updates from routine monitoring program-organization |
| Sep 7, 2023 | Lake Merritt Boating Center (204LME025) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Jun 30, 2023 | Lake Merritt Boating Center (204LME025) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Jun 30, 2023 | at Lakeshore Ave. near Chalet (204LME010) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Jun 9, 2023 | at Lakeshore Ave. near Chalet (204LME010) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Jun 9, 2023 | Lake Merritt Boating Center (204LME025) | None | No cyano bloom w/testing; Updates from routine monitoring program-organization |
| Nov 28, 2022 | Rotary Nature Center | None | End date recorded: Nov 28, 2022. Lake-wide advisory; Marine bloom present (red tide); Suspected bloom, investigation ongoing |
| Nov 28, 2022 | Rotary Nature Center | None | End date recorded: Nov 28, 2022. Lake-wide advisory; Marine bloom present (red tide); Suspected bloom, investigation ongoing |
| Nov 22, 2022 | Rotary Nature Center | Caution | Lake-wide advisory; Marine bloom present (red tide); Suspected bloom, investigation ongoing |
| Sep 16, 2022 | Lake Merritt Boating Center | Caution | Advisory based on visual and toxins; Suspected illness reported |
| Sep 16, 2022 | Lake Merritt Ampitheater | Caution | Advisory based on visual and toxins; Suspected illness reported |
| Sep 16, 2022 | Lake Merritt at Lakeshore Ave. near Boden Way | Caution | Advisory based on visual and toxins; Suspected illness reported |
| Sep 16, 2022 | Lake Merritt Boating Center | Caution | Advisory based on visual and toxins; Suspected illness reported |
| Sep 16, 2022 | Lake Merritt Boating Center | Caution | Marine bloom present (red tide); Suspected illness reported |
| Aug 30, 2022 | Lake Merritt at Lakeshore Ave. near Boden Way | Caution | Advisory based on visual and toxins |
| Aug 30, 2022 | Lake Merritt at beach south of Edoff Memorial Bandstand | Caution | Advisory based on visual and toxins |
| Aug 25, 2022 | Lake Merritt Boating Center | Caution | Marine bloom present (red tide); Suspected illness reported |
| Aug 25, 2022 | Lake Merritt Boating Center | Caution | Lake-wide advisory; Suspected bloom, investigation ongoing; Suspected illness reported |
| Aug 8, 2022 | Lake Merritt shoreline between 1200 and 1400 Lakeshore Avenue | NA - refer to Report Details | Lake-wide advisory; Marine bloom present (red tide) |
| Aug 8, 2022 | Lake Merritt shoreline between 1200 and 1400 Lakeshore Avenue | Caution | Marine bloom present (red tide) |
| Aug 8, 2022 | Lake Merritt shoreline between 1200 and 1400 Lakeshore Avenue | Caution | Suspected bloom, investigation ongoing |
| Jun 29, 2022 | Lake Merritt at Lakeshore Ave. near Boden Way | Caution | Advisory based on visual and toxins |
| Jun 29, 2022 | Lake Merritt at beach south of Edoff Memorial Bandstand | Caution | Advisory based on visual and toxins |
| May 19, 2022 | Near Light Post 82 and Cleveland Cascade at Lake Shore Ave. | Caution | Advisory based on visual and toxins |
| May 19, 2022 | Near Light Post 82 and Cleveland Cascade at Lake Shore Ave. | Caution | Advisory based on visual and toxins |
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.