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Amoebophrya is a marine parasite recently found to infect and kill bloom-forming dinoflagellates in the California Current System (CCS). However, it is unknown whether parasitism by Amoebophrya can control dinoflagellate blooms in major eastern boundary upwelling systems, such as the CCS. We quantified the abundance of a common bloom-forming species Akashiwo sanguinea and prevalence of its parasite (i.e., % infected cells) in surface water samples collected weekly from August 2005 to December 2008 at the Santa Cruz Wharf (SCW), Monterey Bay, CA. Additionally, we measured physical and chemical properties at the SCW and examined regional patterns of wind forcing and sea surface temperature. Relative abundance of the net phytoplankton species was also analyzed to discern whether or not parasitism influences net phytoplankton community composition. Epidemic infection outbreaks (>20% parasite prevalence in the host species) may have contributed to the end or prevented the occurrence of A. sanguinea blooms, whereas low parasite prevalence was associated with short-term (≤2 weeks) A. sanguinea blooms. The complete absence of parasitism in 2007 was associated with an extreme A. sanguinea bloom. Anomalously strong upwelling conditions were detected in 2007, suggesting that A. sanguinea was able to outgrow Amoebophrya and ‘escape’ parasitism. We conclude that parasitism can strongly influence dinoflagellate bloom dynamics in upwelling systems. Moreover, Amoebophrya may indirectly influence net phytoplankton species composition, as species that dominated the net phytoplankton and developed algal blooms never appeared to be infected.

In California, the toxic algal species of primary concern are the dinoflagellate Alexandrium catenella and members of the pennate diatom genus Pseudo-nitzschia, both producers of potent neurotoxins that are capable of sickening and killing marine life and humans. During the summer of 2004 in Monterey Bay, we observed a change in the taxonomic structure of the phytoplankton community—the typically diatom-dominated community shifted to a red tide, dinoflagellate-dominated community. Here we use a 6-year time series (2000–2006) to show how the abundance of the dominant harmful algal bloom (HAB) species in the Bay up to that point, Pseudo-nitzschia, significantly declined during the dinoflagellate-dominated interval, while two genera of toxic dinoflagellates, Alexandrium and Dinophysis, became the predominant toxin producers. This change represents a shift from a genus of toxin producers that typically dominates the community during a toxic bloom, to HAB taxa that are generally only minor components of the community in a toxic event. This change in the local HAB species was also reflected in the toxins present in higher trophic levels. Despite the small contribution of A. catenella to the overall phytoplankton community, the increase in the presence of this species in Monterey Bay was associated with an increase in the presence of paralytic shellfish poisoning (PSP) toxins in sentinel shellfish and clupeoid fish. This report provides the first evidence that PSP toxins are present in California's pelagic food web, as PSP toxins were detected in both northern anchovies (Engraulis mordax) and Pacific sardines (Sardinops sagax). Another interesting observation from our data is the co-occurrence of DA and PSP toxins in both planktivorous fish and sentinel shellfish. We also provide evidence, based on the statewide biotoxin monitoring program, that this increase in the frequency and abundance of PSP events related to A. catenella occurred not just in Monterey Bay, but also in other coastal regions of California. Our results demonstrate that changes in the taxonomic structure of the phytoplankton community influences the nature of the algal toxins that move through local food webs and also emphasizes the importance of monitoring for the full suite of toxic algae, rather than just one genus or species.

Yessotoxin (YTX) was detected in an algal sample and two mussel samples (0.07–0.10 μg g −1 ) collected from Scripps Pier in La Jolla, California during a bloom of Lingulodinium polyedrum . Mussel samples collected from Monterey Bay, California also contained measurable YTX (levels up to 0.06 μg g −1 ) in samples obtained during a 6-month (weekly) sampling period. Gonyaulax spinifera and L. polyedrum were identified in background concentrations in Monterey Bay during the time of contamination. An algal sample from Washington coastal waters collected during non-bloom conditions also contained YTX, possibly originating from Protoceratium reticulatum . Three strains of L. polyedrum (CCMP1931, CCMP1936, 104A) isolated from southern California coastal waters and one strain of G. spinifera (CCMP409) isolated from Maine were tested for YTX production using two methods, competitive ELISA and liquid chromatography–mass spectrometry (LC–MS). The ELISA method detected YTX in the particulate phase in two of three L. polyedrum strains. The LC–MS method did not detect YTX in the particulate or dissolved phase of any of the strains. To our knowledge, this is the first study to test and confirm YTX in environmental samples from California and Washington coastal waters. It is highly likely that L. polyedrum was responsible for the YTX contamination in the southern California samples. Future research needs to conclusively determine the biological origin(s) of YTX contamination in central California and Washington coastal waters.

A sudden and nearly synchronous emergence of the red tide forming dinoflagellate Cochlodinium along more than 800 km of California coastline was initially observed in late summer 2004. Thereafter high cell concentrations have been detected on an annual basis. Here, we present quantitative and semi-quantitative data indicating that Cochlodinium was uncommon in the phytoplankton community in California prior to 2004 and is now persisting as a more regular component and one that seasonally can cause red tides. The quantitative portion of this study was primarily conducted in Monterey Bay, where cell densities reached at least 6 × 10 4 cells L −1 during the initial outbreak. A semi-quantitative comparison of California coastal counties by the California Department of Health Services (CDHS) was also made: of the 15 counties surveyed (most with multiple sites per county), cells were detected only from Los Angeles County in the south to San Mateo County in the central region (seven counties), but not in the northern part of the state (six counties). Two counties in the central region of the state, San Luis Obispo and Santa Cruz, displayed intense and frequent periods of elevated Cochlodinium cell abundances. Although not observed in the state-wide CDHS survey, we occasionally found cells in San Diego County with densities up to 2.7 × 10 4 cells L −1 . Though these colonial dinoflagellates have been recognized in California for over 80 years, with several “blooms” recorded prior to 2004, the species’ geographic range and abundance in recent years suggest significant shifts in the nearshore phytoplankton community of this region of the eastern Pacific.

Over the past decade diatom blooms of domoic acid (DA)-producing Pseudo-nitzschia spp. have been responsible for numerous marine mammal and bird mortalities in Monterey Bay, CA. One possible toxin vector is the market squid, Loligo opalescens , a small pelagic mollusk that plays an important role in the near-shore food web of the California Current ecosystem as a favored vertebrate prey species. This study examined the trophic link between toxic Pseudo-nitzschia and L. opalescens using toxin and stomach content analyses of animals collected from Monterey Bay, CA in 2000. Receptor binding assay data (confirmed by tandem mass spectrometry), demonstrated the presence of DA in squid during a toxic Pseudo-nitzschia event, with P. australis frustules observed in stomach samples. Though DA levels were low ( −1 tissue) in L. opalescens during the study period, it is now clear that this potent neurotoxin can occur in squid and is likely delivered through its krill prey species, which are known to retain DA after feeding on toxic Pseudo-nitzschia . Our findings suggest that further study of the relationship between Pseudo-nitzschia blooms and DA contamination of squid is warranted to better evaluate the potential health risk to humans and wildlife associated with this major commercial seafood species and important prey item.

Heterosigma akashiwo (Hada) gives rise to red tides along the Atlantic and Pacific coasts and is known to produce brevetoxins. This investigation establishes baseline information showing the presence of H. akashiwo along the central California coast based on water samples collected from the Santa Cruz pier in Monterey Bay (on the open coast) and the Berkeley pier in San Francisco Bay. Light and electron microscopy as well as two species-specific DNA probe methods based on cell homogenates preparations were employed to detect H. akashiwo during the 2001–2002 field study. The DNA probe methods consisted of a sandwich hybridization assay (SHA), which targets ribosomal RNA (rRNA), and an end-point polymerase chain reaction (PCR) assay, which targets internal transcribed spacer (ITS) sequences of rRNA genes. The SHA was used to provide semi-quantitative data showing the intermittent presence of the species during a 13-month period in Monterey Bay. Samples that showed a variety of responses in the SHA (negative as well as the highest) were then subjected to the PCR assay in an attempt to confirm species identification using an independent DNA probe method that employs cell homogenates; samples included those from Monterey Bay and one from a red tide event in San Francisco Bay. SHA and PCR assays agreed on the presence or absence of H. akashiwo. Gene products from two field samples positive for H. akashiwo by PCR were cloned and sequenced and found to be identical to those of that species in GenBank. When the same samples were viewed by light microscopy, however, H. akashiwo cells were only seen in the sample with the highest abundance of that species, as evidenced by SHA. It was extremely difficult to recognize naturally occurring H. akashiwo using light microscopy in field samples that had been preserved with Lugol's iodine, including samples that gave positive results by cell homogenate methods. Results of this study indicate that H. akashiwo is present along the open California coast and could easily be missed in routine phytoplankton surveys. Despite its presence, H. akashiwo does not appear to routinely bloom with sufficient densities to cause harmful outbreaks of the frequency and severity documented in some other coastal environments. Molecular identification techniques may be the preferred approach over light microscopy when there is a need to rapidly screen many samples for fragile, harmful species and those that are otherwise problematic to identify based on their gross morphology alone.