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The neurotoxin domoic acid (DA) produced by the diatoms Pseudo-nitzschia has been responsible for deaths of marine mammals and birds in Monterey Bay, California, USA. In this study we examined links between DA-related strandings of the seasonally migratory California sea lion Zalophus californianus and regional occurrences of DA-producing diatoms using a decade-long time series. Results suggest a more complex pattern of stranding than anticipated, one not related simply to regional abundance of the toxin producers. Stranding patterns of sea lions exhibiting signs of acute DA toxicosis may be best explained by multiple causative factors including timing of toxic blooms with respect to the sea lion breeding cycle, adequacy of sea lion prey during the breeding season, as well as the geographic range of this pinniped outside of the breeding season. Three DA-related stranding events occurred in Monterey Bay in 1998, 2000 and 2007, when toxic DA blooms were pre- sent in the Bay and the California coast was experiencing El Nino/Southern Oscillation conditions. Foraging centers near the breeding site likely provided inadequate food for individuals, leading to northerly movement of these highly mobile predators to other geographic sites resulting in exposure to toxic DA-producing blooms. High toxic Pseudo-nitzschia and DA concentrations did not, however, result in DA-related stranding events in 2002, 2003 and 2004, when weaker than normal upwelling events were present in the Bay. Relative productivity of central versus southern California with respect to the breeding season thus appears to strongly influence the frequency of DA-related strand- ings in Monterey Bay, California.

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.

Harmful algal blooms (HABs) are common in Monterey Bay, CA, and have resulted in repeated closures of shellfish fisheries and the poisoning and death of marine mammals. In the majority of instances, HAB events in this region are first detected by the presence of sick or dying animals. The phrase “cryptic blooms” was adopted to denote the appearance of poisoning at higher trophic levels with no prior evidence of a large phytoplankton bloom. We hypothesize that the onset of many HAB events goes undetected because the bloom is initially concentrated in discrete thin subsurface layers in the water column that are easily missed by conventional sampling and monitoring methods. In this paper, we report on the detection and monitoring of a subsurface layer of phytoplankton in northern Monterey Bay, CA, using a high-resolution, autonomous profiler. This ‘thin layer,’ which measured from 10 cm to 3 m in thickness (85%

Within Monterey Bay, California, USA, the food web transfer of domoic acid (DA), a neurotoxin produced by diatoms of the genus Pseudo-nitzschia, has led to major mortality events of marine mammals and birds. Less visible, and less well known, is whether invertebrates and fish associated with the benthos are also affected by blooms of DA-producing Pseudo-nitzschia spp. This study examines the presence of DA in benthic flatfish offshore of Davenport, California, (37°0′36″N, 122°13′12″W) and within Monterey Bay, California (36°45′0″N, 122°1′48″W), including species that feed primarily in the sediment (benthic-feeding) and species that feed primarily in the water column (benthopelagic-feeding). Flatfish caught between 10 December 2002 and 17 November 2003 at depths of 30–180 m had concentrations of DA in the viscera ranging from 3 to 26 μg DA g−1 of viscera. Although the DA values reported are relatively low, benthic-feeding flatfish were frequently contaminated with DA, especially as compared with the frequency of contamination of flatfish species that feed in the water column. Furthermore, on days in which both benthic-feeding and benthopelagic-feeding flatfish were collected, the former had significantly higher concentrations of DA in the viscera. Curlfin turbot, Pleuronicthys decurrens, the flatfish with both the highest level and frequency of DA contamination, are reported to feed exclusively on polychaetes, suggesting that these invertebrates may be an important vector of the toxin in benthic communities and may pose a risk to other benthic-feeding organisms.

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.

In at least two mass mortality events in Monterey Bay, California, planktivorous fish were implicated as vectors of the neurotoxin domoic acid (DA) from diatoms to sea birds and marine mammals. Whereas the transfer of DA from planktivorous fish to piscivorous predators has been well established, the relationship between toxin levels in plankton-feeding fish and the regional abundance of DA-producing diatoms has not been documented. Here we present data from an extensive field study in which cell densities of toxic Pseudo-nitzschia species and DA levels in anchovies and sardines were measured from samples collected weekly throughout Monterey Bay from 8 October 1999 to 18 October 2000. Four distinct blooms were documented with cell densities ranging from 3.2×103 to 5.0×105 cells l–1. DA was detected in fish viscera samples whenever toxic diatom densities reached ≥103 cells l–1 in surface waters, suggesting that anchovies and sardines regularly consume toxic diatoms when present. Fish contained DA levels above the regulatory limit (20 µg DA g–1 whole fish) only when toxic cell densities exceeded 104 cells l–1. DA was only detected in fish when toxic diatom species were also present in the water, suggesting that the toxin is quickly depurated and that fish are only dangerous vectors during the bloom period. Anchovies appear to be more potent vectors than sardines as they consistently contained more DA than sardines collected simultaneously. Maximum DA levels detected in fish were 1,815 µg DA g–1 in anchovy and 728 µg DA g–1 in sardine viscera samples. In fish with high viscera levels of DA, corresponding body tissues contained 0.2–2.2 µg DA g–1 (0.2±0.1% of the viscera level), suggesting that DA is not accumulated in edible body tissues to levels that threaten human consumers. Results from this study suggest that anchovies may be a valuable indicator species for assessing the risk of DA intoxication to piscivorous sea birds and mammals during toxic Pseudo-nitzschia blooms in Monterey Bay.

Bacterioplankton abundance and metabolic characteristics were observed in northern San Francisco Bay, California, during spring and summer 1996 at three sites: Central Bay, Suisun Bay, and the Sacramento River. These sites spanned a salinity gradient from marine to freshwater, and sampling occurred during a period of seasonally declining river flow. The microbial measures included radio-labeled amino acid uptake ( L-leucine, L-proline, Lserine), ectoenzyme activity (aminopeptidase and b-D-glucosidase), and bacterial abundance using 1-mm filters to separate free from particle-associated bacteria. A seasonal decline in all bacterial metabolic measures was observed at all stations, suggesting that a system-wide variable may be important in controlling bacterial activity. One such variable is freshwater flow into the Bay (as a proxy for organic matter flux), which positively covaried with all metabolic measures. A sharp decline in particle-associated bacteria was also observed in Suisun Bay and the Sacramento River between July and August. This decline may have been due to combined effects of declining nutritive value of the aging particles and increasing grazing pressure by benthic filter feeders. Aminopeptidase activity was positively related with increasing salinity, and b-D-glucosidase was negatively correlated with increasing salinity, indicating a gradient in the relative quality of organic matter from carbohydrate-rich riverine to proteinrich oceanic material. Overall, Suisun Bay had the highest mean proportion of particle-associated bacteria (49%), followed by Sacramento River (36%) and Central Bay (11%). Particles were the sites of enhanced ectoenzyme activity but not amino acid incorporation. Bacteria may be actively dissolving the particulate organic matter, but their growth rates on particles are not significantly enhanced.

Aggregates >0.25 mm were collected over a 4-year period below the euphotic zone at depths between 40–251 m and at a 400–1000 m deep station in the Monterey Submarine Canyon system using a remotely operated vehicle (ROV). The aggregates were sized and characterized to determine their origins and possible association with local production cycles at a station regularly monitored by the Monterey Bay Aquarium Research Institute’s (MBARI’s) ocean monitoring program. We present a first-time inventory of particle types with their size distribution for Monterey Bay. Phytoplankton-containing aggregates number about half of the total aggregates in the upper, 40–251 m layer, but decline to 5% at 400 m, possibly due to offshore transport of sinking material, input of resuspended aggregates at depth, and/or intense biological recycling of aggregates in the midwater. In the upper layer, only the abundance of the phytoplankton containing aggregates was weakly correlated with local phytoplankton abundance as measured by in situ fluorescence on that day at a near-by mooring: correlations did not exist for total numbers of aggregates. Instead, aggregates were mostly of detrital origin, with organic matter of unrecognizable origin and sometimes with conspicuous lithogenic material. Particles of fecal origin were third in abundance, and their numbers are relatively low (25 l -1 ) compared with aggregates, likely because of their higher sinking rates. We suggest that many of the sub-euphotic aggregates in this system may be derived from additional sources or events not directly tied to production cycles. Because particles such as these are likely responsible for the observed mass flux at this site (see Pilskaln et al., 1998), the concept of a simple, surface-driven “biological pump” may not be applicable on short-time scales in predicting material flux in dynamic continental margin systems.

Seasonal profiles of marine aggregate abundance and in situ sinking rate experiments were carried out using a uniquely instrumented ROV platform in the midwater column of Monterey Bay California between 1991 and 1994. Variations of an order of magnitude in the midwater 100–500 m abundance of aggregates within the 0.5 to >5 mm size range were observed on an inter- and intra-annual basis at the study site. Maximum midwater aggregate abundances of 15–40 aggregates l -1 were common during the 1991 spring/summer upwelling season, with values of less than 5 aggregates l -1 being more typical of the non-upwelling winter months and the 1992 El Nino period. Midwater aggregate peaks represented the temporal signal of sinking aggregate material produced in the overlying waters, with no correlation observed between the vertical distribution of aggregates and the density structure, or the relative suspended particle abundence measured as c p . Additionally, significant injection of aggregate material to the midwater profiles via lateral advection was not evidenced by the combined aggregate, hydrographic, and physical flow data sets obtained simultaneously at the study site. In situ aggregate sinking rates were measured using an ROV-mounted settling chamber. Mean rates ranged from 16.3 to 25.5 m day -1 with a trend of increasing sinking rate with aggregate diameter observed. An analysis of aggregate shape showed a decrease in spherical shape with increasing aggregate diameter and sinking rate. Seasonal aggregate POC fluxes at 450 m for 1991–1992 were calculated from the in situ aggregate property data sets to compare with coincident, 450 m trap-measured POC fluxes. The calculated aggregate POC fluxes ranged from 26.3 to 481.2 mgC m -2 d -1 and were at least 1.5–2 times greater than the trap POC fluxes, with the exception of the non-upwelling winter months where values are similar. Trapping efficiency and interannual variations in aggregate sinking rates are believed to explain the differences between the aggregate and trap-based POC fluxes.

By using a remotely operated vehicle (ROV), we studied large mucous aggregates produced by the larvacean Bathochordaeus in Monterey Bay, California. These fragile structures or “houses,” cannot be sampled by typical water or net collecting devices, and likely represent a class of cosmopolitan, widely spaced aggregates in subsurface waters. ROV samples allowed us to determine the contribution of the aggregate-associated communities to populations of microorganisms at depths of 100–500 m. Because the giant houses only average ˜1 per 100 m3, they harbor

The mucus feeding structures or “houses” of the giant larvacean Bathochordaeus provide abundant material for the study of deep-sea detrital communities, particularly their poorly known zooplankton associates. We sampled houses between 100 and 500 m in Monterey Bay with a submersible ROV (remotely operated vehicle) and surveyed houses for metazoans by database search of video footage taken from the ROV. Up to an order of magnitude more metazoans were found on houses than in surrounding waters. On average, copepods constituted as much as 96% of the assemblage on houses, and many of the species possess benthiclike morphology and feeding strategies. Poecilostomatoid copepods (genus Oncaea) averaged as many as 64.6 house-‘, and scarcely known calanoid copepods (genus Scopalatum) occurred in 56% of the samples. Higher numbers of metazoans occurred on shallower houses (lo&300 m), likely due to a difference in the species of larvacean present and (or) to reduce oxygen levels at greater depths. At least one copepod species, Scopalatum vorax, occurred on houses more frequently during the nonupwelling season, possibly due to the lack of other food. Our results suggest that midwater detritus contains a unique invertebrate community that has been largely undetected, mostly due to sampling difficulties. The houses also provide benthiclike habitats for midwater zooplankton and serve as feeding centers. These particle-associated zooplankton may therefore contribute to remineralization of particulate organic carbon at depth.

During the autumn of 1991, numerous seabird fatalities in Monterey Bay, California, led to the discovery of a new domoic acid-producing diatom, Pseudonitzschia australis. Since this initial event, sizable populations of P. australis, as well as other likely toxin producers, P. pungens f. multiseries and P. pseudodelicatissima, have occurred biannually in Monterey Bay. Using the highly sensitive FMOC-HPLC method, we detected domoic acid whenever Fseudonitzschia australis was found in the plankton, even at densities as low as 4.0 × 103 cells/L. Based on correlations of domoic acid and P. australis abundances and the overwhelming biovolume dominance of P. australis, we conclude that P. australis has been the major domoic acid producer during the period of our study. Our study suggests that P. australis cells may always be toxic in natural populations and that toxin concentrations on a per-cell basis have no statistically significant relationship to population density or to nutrient concentrations other than silicate. Cellular levels of domoic acid were positively correlated with silicate concentrations, which is at variance with reports from prior culture experiments. These conclusions must be tentative because of the limited extent of our sampling. Nevertheless, these preliminary data indicate that further investigations of environmental conditions affiliated with cell growth and toxin production in P. australis are warranted. As a practical matter, domoic acid in the pelagic environment cannot be reliably or consistently detected by monitoring domoic acid levels in intertidal mussels. Direct measurement of domoic acid using sensitive HPLC methods is probably the most cost-effective and accurate approach for an ongoing phycotoxin monitoring program. © 1994 wiley-Liss, Inc.

15 páginas, 5 figuras, 4 tablas, In the mesopelagic zone, at depths of 200–1000m in the Monterey Submarine Canyon, CA, medusae in three genera of scyphozoa, Atolla, Periphylla and Poralia, were observed, videotaped and collected over a 9-year period (1990–1998). Environmental data were obtained simultaneously using a remotely operated vehicle (ROV) with sensors for depth, temperature, salinity and dissolved oxygen. Shipboard measurements of these same properties at two reference stations in the region defined the local water masses and helped identify species niches using the metric of spiciness and oxygen levels of the waters in which medusae were visually ‘‘captured’’. The most abundant genus of mesopelagic scyphomedusae was Atolla, found associated most strongly with the spicy (warm, salty) waters of the California Undercurrent, usually above the core of the oxygen minimum zone (OMZ; O240.5 ml/l). The least abundant mesopelagic scyphomedusa was Periphylla, which occurred in more variable waters, including those with a greater contribution of fresher, colder (less spicy), subarctic water and, hence, most like those at the offshore California Current station in the most depleted oxygen zone (averaging O2o0.3 ml/l). Poralia was mostly confined to the densest, coldest water, with peak abundance at the lower boundary of the OMZ (i.e., 0.3o O2o0.5 ml/l). These spiciness measures on local isopycnal surfaces within the mesopelagic zone, supported by data on dissolved oxygen concentrations, indicate highly significant but fine-scale habitat differences in species habitats in Central California waters. This in situ investigation appears to be one of only a few studies to document fine-scale, water mass affinities of mesopelagic zooplankton., This project was supported by the David and Lucile Packard foundation through MBARI, grants to D.A. Osborn from the Myers Marine Biology Trust, Friends of Long Marine Lab and the University of California Santa Cruz Ocean Science Department.

Over 400 California sea lions (Zalophus californianus) died and many others displayed signs of neurological dysfunction along the central California coast during May and June 1998. A bloom of Pseudo-nitzschia australis (diatom) was observed in the Monterey Bay region during the same period. This bloom was associated with production of domoic acid (DA), a neurotoxin1 that was also detected in planktivorous fish, including the northern anchovy (Engraulis mordax), and in sea lion body fluids. These and other concurrent observations demonstrate the trophic transfer of DA resulting in marine mammal mortality. In contrast to fish, blue mussels (Mytilus edulus) collected during the DA outbreak contained no DA or only trace amounts. Such findings reveal that monitoring of mussel toxicity alone does not necessarily provide adequate warning of DA entering the food web at levels sufficient to harm marine wildlife and perhaps humans.