Phytoplankton Monitoring Program
The CDPH Marine Biotoxin Program coordinates a volunteer-based
monitoring effort for toxic phytoplankton along the entire California coastline.
Interactive map layers provide information on our weekly data for the
distribution and relative abundance of toxin-producing phytoplankton along the
California coast. The following information provides an overview of the program
and an explanation of why phytoplankton monitoring is an important tool for
public health protection.
Phytoplankton
Phytoplankton are single-celled algae that are the base of the
marine food chain. The vast majority of marine life in our coastal waters could
not exist without these naturally-occurring microscopic plants. There are
hundreds of species of phytoplankton in the ocean, and the vast majority are
nontoxic. A small number of species are known to produce toxins that can
accumulate in filter-feeding organisms, especially bivalve shellfish like
mussels, oysters, clams, and scallops. These toxins can also accumulate in small
fish like anchovies and sardines, as well as in crustaceans like crab and
lobster that may feed on other species that contain these toxins. Humans, as
well as marine mammals and seabirds, can be harmed by these nerve toxins when
dangerous levels accumulate in these seafood items. There are many categories of
phytoplankton, of which dinoflagellates and diatoms are the most important with
respect to marine toxins along the California coast.
Dinoflagellates
Dinoflagellates are plants that can
swim via their two flagella. As a result they can actually migrate vertically in
the water column. When conditions are favorable, one or more populations of
dinoflagellate may begin growing exponentially, resulting in millions of cells
per liter of seawater. This 'bloom' can result in a phenomenon called a red tide. The vast majority of red tides along
the California coast are produced by nontoxic species of dinoflagellates.
One genus of dinoflagellate, Alexandrium,
is responsible for producing the PSP toxins. Alexandrium
rarely blooms, so it is not safe to assume that the absence of a red tide means
that shellfish in the area are safe to harvest and consume. Although
Alexandrium rarely forms visible blooms, the toxins it
produces are so potent that only a couple hundred cells per liter are required
to result in dangerous levels of paralytic shellfish poisoning toxins in
shellfish.
Diatoms
The group of phytoplankton called diatoms are
single-celled and chain-forming algal cells with silica cell walls. Diatoms were
not known to produce neurotoxins until a large-scale poisoning episode occurred
in 1987 in eastern Canada. Over two hundred persons were made ill and four died
as a result of mussel consumption in Prince Edward Island, a productive
commercial shellfish growing area. Others suffered permanent neurological damage
(for example, a permanent loss of short-term memory capabilities). The
investigation by Canadian researchers and government scientists discovered the
toxin, domoic acid, and the source of the toxin: a chain-forming diatom that is
a common member of the phytoplankton community in many parts of the world. The
syndrome caused by domoic acid was termed āAmnesic Shellfish Poisoningā
(ASP).
The diatom genus responsible for producing domoic acid is named Pseudo-nitzschia .
Unlike Alexandrium, Pseudo-nitzschia
is often observed in low numbers along the California coast. This diatom can
also increase in numbers rapidly, producing blooms of millions of cells per
liter and dominating the phytoplankton community for extended periods of time.
Program History
As mentioned previously, California has had a long-standing awareness
of the dangers of paralytic shellfish poisoning and has relied on an extensive
shellfish monitoring program to detect the presence of the potent toxins
responsible for this syndrome. In the fall of 1991 another natural toxin was
identified along the California coastline. An investigation into the deaths of
hundreds of seabirds in Monterey Bay led to the identification of domoic acid as
the cause. This neurotoxin was not previously known to exist anywhere along the
west coast of the U.S. Domoic acid was identified in the anchovies and sardines
on which the seabirds had been feeding. Further investigation discovered an
abundance of the diatom Pseudo-nitzschia in the stomachs
of the fish. Analysis of the fish gut contents revealed high concentrations of
domoic acid. Although this toxin is less potent than the PSP toxins, it has
become of increasing concern because the blooms of diatoms that produce this
toxin have been of greater frequency and longer duration than most PSP events
over the past 10 years. In addition, domoic acid has had dramatic impacts on
marine mammal and seabird populations along the coast. These wildlife impacts
have raised the publicās awareness of marine biotoxins in general and can
provide valuable information to government scientists and university
researchers.
Because of the threat of a new toxin, domoic acid, the presence of
multiple toxic species along the California coast, and the apparent global
increase in phytoplankton blooms in general and the increase in magnitude and
geographic distribution of toxic blooms in particular, CDPH developed a
volunteer-based phytoplankton monitoring program. This volunteer-based effort,
the first statewide effort in the U.S., is one of several elements of CDPHās
effort to protect the public from these potentially deadly
neurotoxins.
Phytoplankton Monitoring in California
The Phytoplankton Monitoring Program was officially launched in January
1993 when the first volunteer sample arrived at the CDPH laboratory. The first
volunteers were existing program participants in the Shellfish Monitoring
Program and local concerned citizens. Over the years the number and diversity of
program participants has increased and includes local public health agencies,
municipal utilities, K-12 school groups, university researchers and students,
local environmental groups, educational nonprofit organizations, marine animal
rescue centers, involved citizens, and many others. During 2014 there were 85
active volunteers collecting 1975 samples at 161 different locations. Over the
first 20 years of the program there have been over 29,000 samples collected!
This is a true testament to the dedication and importance of everyone who has
participated in this program over the years.
What Volunteers Do
A phytoplankton net and rope is provided to all program participants,
unless they happen to have access to one already. The net is made of a very fine
and fragile nylon mesh: the mesh size is 20 micrometers, which is small enough
to capture our toxin-producers and most other species present. The net is gently
lowered into the water via the attached rope and allowed to sink to a depth of
10 to 50 feet, depending on the sampling location. The loose end of the rope is
always secured to the pier or other structure to avoid losing it! The net is
slowly retrieved and, as it reaches the surface, allowed to descend to the
sampling depth again. We recommend three to five of these vertical net tows,
depending on the sampling depth and the density of cells present that day.
Following the final tow, the net is retrieved and the sampling bucket at the
bottom of the net is detached. The contents of the sampling bucket are poured
into the sampling bottle provided, which contains a small amount of
preservative. The sample is then placed in the mailing canister along with the
completed laboratory sample submission form, which contains the relevant
sampling information (date, time, location, depth, etc.). The canister can then
be sent to our laboratory via the U.S. Postal Service (postage is prepaid by
CDPH).
What We Do
All samples arriving at CDPH are examined with light microscopy for the
presence of the toxin-producing species. Additional information is recorded on
other common, non-toxic species to help evaluate long-term trends in species
composition and shifts in dominant groups (diatoms versus dinoflagellates). The
field and lab observations provide a valuable snapshot of current trends in the
phytoplankton community. This information is immediately used as necessary to
guide additional sample collection in areas of concern. Over the years there
have been numerous occasions in which the phytoplankton observations alerted
program scientists to the early stages of a toxic bloom. Subsequent focus on the
affected region revealed the presence of toxin and allowed CDPH to alert the
public via a health advisory press release or to close a commercial shellfish
growing area to prevent toxic seafood from entering the marketplace. In fact,
many of the certified shellfish growers in California voluntarily collect
phytoplankton samples and conduct the field observations because this valuable
information helps them manage their harvest activities to ensure the safety of
their product. Finally, the laboratory identifications and the volunteersā field
observations are recorded in the program database for subsequent reporting and
analysis. Each participant's contribution is essential to piecing together a
picture of the distribution of toxic and nontoxic phytoplankton along the
California coast.
How to Get Involved
Despite the wonderful efforts of all our program participants there are
still many areas of the California coast that do not have adequate sampling
effort. CDPH is always interested in having new volunteers join the
Phytoplankton Monitoring Program, especially if it is in an area that needs
additional coverage. CDPH provides the necessary training and equipment for
collecting and shipping samples at no cost to the volunteer. Some volunteers,
typically those with a science background or a keen interest in phytoplankton,
are trained to also conduct the microscopic observations of the samples they
collect. This information is emailed or faxed to the program and a portion of
the sample is also submitted. This allows CDPH biologists to check the
volunteerās accuracy in identifying the phytoplankton species present, which in
turn allows us to provide feedback to help improve their skills and knowledge.
The program also provides training materials to help in the identification
process. To learn more about this program and opportunities to volunteer you can
send an email to redtide@cdph.ca.gov or
call 510-412-4635.
Benefits of Volunteering
All of our program participants are added to an email distribution list
to receive periodic informal updates on observations, trends, and detection of
toxins along the California coast based on the volunteer monitoring effort. In
addition, a more formal monthly report is distributed to everyone once the data
has been compiled and validated. The monthly reports contain maps of toxigenic
phytoplankton distribution and toxin distribution at all sampling sites. In
addition, the monthly reports contain tables listing the program participants
that provided samples or field identifications during that month. An annual
report is also produced that summarizes the events and sampling effort of the
past year.
Of course the real benefits to volunteering are the intangible ones.
You will know that your efforts are important to a real-time public health
protection program. Phytoplankton sampling and field observations also provide a
way to get connected to your local ocean environment. The phytoplankton species
composition will change with changing environmental conditions (for example,
wind intensity and direction, water temperature), so each sample can bring
something new. And you can interact with program biologists to have questions
answered or to get advice on sources of additional information on a particular
related topic.