Some swimmers on the Central Coast are noticing red, murky waters at local beaches, which experts say shouldn’t impact your weekend plans to hit the coast.
These conditions are expected for this time of year.
High concentrations of phytoplankton, or tiny plant-like creatures in the ocean, can cause what’s often described as a red tide.
Late summer and early fall are prime conditions for algae blooms to grow - rapidly and in high numbers.
Just like plants on land, different species of blooms take on different colors, like a dark green hue or they can become illuminated at night.
While the change in water color raises concerns for beachgoers, experts say, there is no direct impact on humans.
“Some of these organisms and just a small fraction of the species do produce toxins but we are less worried about direct contact with those toxins, and more if organisms like mussels and clams eat the algae, those toxins get accumulated and so it can be dangerous to eat those organisms. So we do measure toxins and keep track of that,” said Alexis Pasulka, Assistant Professor in the Biological Sciences Department at Cal Poly.
Another harmful effect of the blooms is dissolved oxygen.
"During large bloom events, oxygen dissolved in the water column, which is used by organisms living in the ocean like fish and invertebrates for respiration, can become depleted due to the breakdown of the large blooms by bacteria as well as nighttime respiration by the phytoplankton. In some cases this can lead to hypoxic levels and cause adverse effects to marine life, including fish kills in the extreme cases. We are seeing low oxygen values right now at one of our real-time water quality stations at the mouth of Morro Bay," said Ryan Walter, Associate Professor in the Physics Department at Cal Poly. "It remains to be seen how this will locally impact different organisms."
Cal Poly students regularly collect samples from the Cal Poly pier and from the mouth of Morro Bay as part of the California Harmful Algal Blooms Monitoring and Alert Program (CALHABMAP).
Student Elysa Romanini monitors algae levels weekly and is seeing elevated concentrations in some areas.
“At the Morro Bay site this week, we saw super elevated concentrations of Akashiwo sanguinea, which also helped us realize that’s probably the culprit of what we are seeing in Pismo as well,” said Romanini.
Because conditions and tides are constantly changing, blooms can last anywhere from days to months.
Pasulka says, a variety of blooms are expected to make appearances through the fall.