Arroyo Seco: toxic algae advisories
Arroyo Seco, Monterey County. See all Monterey County waters.
What the state's records say
Algal mat alert sign, last posted May 9, 2025. 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: The state recorded an advisory of a type outside the Caution, Warning and Danger levels. Read the sign posted at the water.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Arroyo Seco
The state has an advisory on file for Arroyo Seco (Algal mat alert sign), last posted May 9, 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 |
|---|---|
| ~0.3mi above Rosevelt Cr. (309ARSARC) | Algal mat alert sign, last posted May 9, 2025. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Arroyo Seco, 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 |
|---|---|---|---|
| May 9, 2025 | ~0.3mi above Rosevelt Cr. (309ARSARC) | Algal mat alert sign | Updates from routine monitoring program-organization |
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.