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Pollution of nearshore waters with disease-causing microorganisms impacts ecosystems health through illness and deaths in people and wildlife, as well as negative socioeconomic consequences of impaired marine resources. Insight on pathogen ecology in coastal habitats is crucial for accurately mitigating inputs and impacts of microbial pollution. Three objectives were addressed to (i) compare fecal pollution in proximity to (a) freshwater runoff, and (b) endemic marine wildlife; (ii) evaluate presence and magnitude of fecal microorganisms in marine snow and mussels and (iii) determine if pathogens in mussels and FIB levels in seawater or mussels are correlated. Sampling during the wet season, proximity to freshwater, and FIB levels in mussel homogenates (but not seawater) were associated with pathogen presence in mussels. Pathogens and FIB were enriched in aggregate-rich fractions, further supporting an important role of marine snow in pathogen transmission. The lack of association between FIB in surrounding waters and presence of pathogens in mussels calls into question current regulations for insuring safe seafood to consumers in the United States, and alternative monitoring approaches such as direct testing for select pathogens should be further evaluated.

Summary The parasite Toxoplasma gondii is an environmentally persistent pathogen that can cause fatal disease in humans, terrestrial warm-blooded animals and aquatic mammals. Although an association between T. gondii exposure and prey specialization on marine snails was identified in threatened California sea otters, the ability of kelp-dwelling snails to transmit terrestrially derived pathogens has not been previously investigated. The objective of this study was to measure concentration and retention of T. gondii by marine snails in laboratory aquaria, and to test for natural T. gondii contamination in field-collected snails. Following exposure to T. gondii-containing seawater, oocysts were detected by microscopy in snail faeces and tissues for 10 and 3 days respectively. Nested polymerase chain reaction was also applied as a method for confirming putative T. gondii oocysts detected in snail faeces and tissues by microscopy. Toxoplasma gondii was not detected in field-collected snails. Results suggest that turban snails are competent transport hosts for T. gondii. By concentrating oocysts in faecal pellets, snails may facilitate entry of T. gondii into the nearshore marine food web. This novel mechanism also represents a general pathway by which marine transmission of terrestrially derived microorganisms can be mediated via pathogen concentration and retention by benthic invertebrates.

© 2016, International Association for Ecology and Health. A pilot project was conducted to examine the health status and possible adverse health effects associated with seawater exposure (microbial water-quality indicators and phytoplankton abundance and their toxins) of surfers in Monterey Bay, Central California coastal waters. Forty-eight surfers enrolled in the study and completed an initial health background survey and weekly health surveys online using Survey Monkey. Descriptive statistics and generalized estimating equation, a regression technique, were used to identify longitudinal and correlated results. The surfers were predominately Caucasian, male, and physically active. They surfed approximately 4 h a week. Their average age was 34 years. The data indicated that the surfers were generally “healthy,” with a low prevalence of diabetes, high cholesterol, and hypertension. Their most common health problems were allergies and asthma. During the study, 10% of the surfers reported gastrointestinal symptoms and 29% reported upper respiratory symptoms. This study suggests surfers were significantly more likely to report upper respiratory symptoms when they had a history of allergies, housemates with upper respiratory symptoms, and/or a history of previous adverse health symptoms while surfing during a “red tide” (an event often associated with the presence of phytoplankton toxins). Additionally, female surfers reported upper respiratory symptoms more than males.

Aquatic macroaggregates (flocs ≥ 0.5 mm) provide an important mechanism for vertical flux of nutrients and organic matter in aquatic ecosystems, yet their role in the transport and fate of zoonotic pathogens is largely unknown. Terrestrial pathogens that enter coastal waters through contaminated freshwater runoff may be especially prone to flocculation due to fluid dynamics and electrochemical changes that occur where fresh and marine waters mix. In this study, laboratory experiments were conducted to evaluate whether zoonotic pathogens (Cryptosporidium, Giardia, Salmonella) and a virus surrogate (PP7) are associated with aquatic macroaggregates and whether pathogen aggregation is enhanced in saline waters. Targeted microorganisms showed increased association with macroaggregates in estuarine and marine waters, as compared with an ultrapure water control and natural freshwater. Enrichment factor estimations demonstrated that pathogens are 2-4 orders of magnitude more concentrated in aggregates than in the estuarine and marine water surrounding the aggregates. Pathogen incorporation into aquatic macroaggregates may influence their transmission to susceptible hosts through settling and subsequent accumulation in zones where aggregation is greatest, as well as via enhanced uptake by invertebrates that serve as prey for marine animals or as seafood for humans.

The protozoan parasite Toxoplasma gondii infects a large proportion of threatened California sea otters (Enhydra lutris nereis), and is an important waterborne pathogen in humans. Contamination of coastal waters with T. gondii is thought to occur through delivery of environmentally resistant oocysts to nearshore regions via overland runoff. The objectives of this study were to evaluate whether T. gondii oocysts and surrogate microspheres attach to aggregates ($ 0.5 mm), and whether the magnitude of aggregation depends on water type, specifically salinity. Laboratory aggregation studies were conducted by adding T. gondii oocysts and surrogate microspheres to riverine, estuarine, and marine waters, and quantifying the proportion of oocysts and surrogates in aggregate-rich and aggregate-free water fractions. Attachment of oocysts and surrogates to aggregates occurred in all water types, but was greater in estuarine and marine waters, with concentrations of T. gondii in aggregates enriched 3–4 orders of magnitude. Aquatic aggregates may, thus, significantly influence waterborne transport of terrestrially derived pathogens, both through enhanced settling and subsequent concentration in the benthos, as well as by facilitating ingestion by invertebrate vectors that can transmit pathogens to susceptible hosts, including sea otters and humans.

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.

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.

Domoic acid is a glutaminergic neurotoxin produced by marine algae such as Pseudo-nitzschia australis. California sea lions (Zalophus californianus) ingest the toxin when foraging on planktivorous fish. Adult females comprise 60% of stranded animals admitted for rehabilitation due to acute domoic acid toxicosis and commonly suffer from reproductive failure, including abortions and premature live births. Domoic acid has been shown to cross the placenta exposing the fetus to the toxin. To determine whether domoic acid was playing a role in reproductive failure in sea lion rookeries, 67 aborted and live-born premature pups were sampled on San Miguel Island in 2005 and 2006 to investigate the causes for reproductive failure. Analyses included domoic acid, contaminant and infectious disease testing, and histologic examination. Pseudo-nitzschia spp. were present both in the environment and in sea lion feces, and domoic acid was detected in the sea lion feces and in 17% of pup samples tested. Histopathologic findings included systemic and localized inflammation and bacterial infections of amniotic origin, placental abruption, and brain edema. The primary lesion in five animals with measurable domoic acid concentrations was brain edema, a common finding and, in some cases, the only lesion observed in aborted premature pups born to domoic acid-intoxicated females in rehabilitation. Blubber organochlorine concentrations were lower than those measured previously in premature sea lion pups collected in the 1970s. While the etiology of abortion and premature parturition was varied in this study, these results suggest that domoic acid contributes to reproductive failure on California sea lion rookeries.

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.

Benthic food webs often derive a significant fraction of their nutrient inputs from phyto- plankton in the overlying waters. If the phytoplankton include harmful algal species like Pseudo- nitzschia australis, a diatom capable of producing the neurotoxin domoic acid (DA), the benthic food web can become a depository for phycotoxins. We tested the general hypothesis that DA contami- nates benthic organisms during local blooms of P. australis, a widespread toxin producer along the US west coast. To test for trophic transfer and uptake of DA into the benthic food web, we sampled 8 benthic species comprising 4 feeding groups: filter feeders (Emerita analoga and Urechis caupo); a predator (Citharichthys sordidus); scavengers (Nassarius fossatus and Pagurus samuelis) and deposit feeders (Neotrypaea californiensis, Dendraster excentricus and Olivella biplicata). Sampling occurred before, during and after blooms of P. australis in Monterey Bay, CA, USA during 2000 and 2001. DA was detected in all 8 species, with contamination persisting over variable time scales. Max- imum DA levels in N. fossatus (674 ppm), E. analoga (278 ppm), C. sordidus (515 ppm), N. californien- sis (145 ppm), P. samuelis (56 ppm), D. excentricus (15 ppm) and O. biplicata (3 ppm) coincided with P. australis blooms, while DA levels in U. caupo remained above 200 ppm (max. = 751 ppm) through- out the study period. DA in 6 species exceeded levels thought to be safe for higher level consumers (i.e. ≥20 ppm) and thus is likely to have deleterious effects on marine birds, sea lions and the endan- gered California sea otter, known to prey upon these benthic 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.

The VERtical Transport In the Global Ocean (VERTIGO) study examined particle sources and fluxes through the ocean’s ‘‘twilight zone’’ (defined here as depths below the euphotic zone to 1000 m). Interdisciplinary process studies were conducted at contrasting sites off Hawaii (ALOHA) and in the NW Pacific (K2) during 3-week occupations in 2004 and 2005, respectively. We examine in this overview paper the contrasting physical, chemical and biological settings and how these conditions impact the source characteristics of the sinking material and the transport efficiency through the twilight zone. A major finding in VERTIGO is the considerably lower transfer efficiency (Teff) of particulate organic carbon (POC), POC flux 500/150 m, at ALOHA (20%) vs. K2 (50%). This efficiency is higher in the diatomdominated setting at K2 where silica-rich particles dominate the flux at the end of a diatom bloom, and where zooplankton and their pellets are larger. At K2, the drawdown of macronutrients is used to assess export and suggests that shallow remineralization above our 150-m trap is significant, especially for N relative to Si. We explore here also surface export ratios (POC flux/primary production) and possible reasons why this ratio is higher at K2, especially during the first trap deployment. When we compare the 500-m fluxes to deep moored traps, both sites lose about half of the sinking POC by 44000 m, but this comparison is limited in that fluxes at depth may have both a local and distant component. Certainly, the greatest difference in particle flux attenuation is in the mesopelagic, and we highlight other VERTIGO papers that provide a more detailed examination of the particle sources, flux and processes that attenuate the flux of sinking particles. Ultimately, we contend that at least three types of processes need to be considered: heterotrophic degradation of sinking particles, zooplankton migration and surface feeding, and lateral sources of suspended and sinking materials. We have evidence that all of these processes impacted the net attenuation of particle flux vs. depth measured in VERTIGO and would therefore need to be considered and quantified in order to understand the magnitude and efficiency of the ocean’s biological pump.

To evaluate the impacts of ontogenetically (seasonally) migrating copepods on carbon transport to the mesopelagic zone, we investigated depth distribution, population structure, and feeding activity of the ontogentic copepod community in the western subarctic Pacific Ocean from day–night pairs of zooplankton samples down to 1000 m during the VERtical Transport In the Global Ocean (VERTIGO) program. Over the 31 July–16 August 2005 study period, the biomass of Neocalanus cristatus and Neocalanus plumchrus predominated in the near surface waters, while Neocalanus flemingeri was already dormant at depth. We observed a strong diel migration for Metridia pacifica, and a seasonal downward migration for Eucalanus bungii. Based on gut pigment analysis, ingestion rate of the copepod community was 214–375 mg C m−2 day−1, which was equal to 26–37% of the concurrent primary production. However, comparison of grazing estimated from gut pigments to calculated carbon demand of the copepod community indicates that phytoplankton comprised 37–59% of the ingested carbon. Thus, the copepod community appears to have also relied on detritus and microzooplankton for their nutrition, likely because primary production during this time was dominated by picophytoplankton too small to be grazed by these large copepods. Fecal pellet flux by the copepod community was estimated to account for 141–223% of the sedimentary particulate organic carbon (POC) flux at 150 m, suggesting considerable fragmentation and consumption of pellets in the upper layers. Fecal pellets alone were adequate to meet copepod carbon demand in the surface 0–150 m layer. Active carbon flux by diel migration of M. pacifica (respiration, egestion, and mortality) was 4–17 mg C m−2 day−1, equal to 6–44% of sedimentary POC flux at 150 m. Active carbon flux by N. flemingeri ontogenetic migration (i.e., respiration and mortality at depth) contributed 246 mg C m−2 year−1, equal to 9% of sedimentary POC flux at 1000 m. The imminent downward migration of N. cristatus and N. plumchrus would lead to an additional ontogenetic carbon flux on the order of 1719 mg C m−2 year−1. Copepod fecal pellet transport and active transport by diel and ontogenetic migration are thus important carbon fluxes during a season dominated by small phytoplankton, and ontogenetic migrants in the subarctic Pacific Ocean play a relatively more important role in active carbon flux compared with other open-ocean regions.

A central question addressed by the VERtical Transport In the Global Ocean (VERTIGO) study was ‘What controls the efficiency of particle export between the surface and subsurface ocean’? Here, we present data from sites at ALOHA (N Central Pacific Gyre) and K2 (NW subarctic Pacific) on phytoplankton processes, and relate them via a simple planktonic foodweb model, to subsurface particle export (150–500 m). Three key factors enable quantification of the surface–subsurface coupling: a sampling design to overcome the temporal lag and spatial displacement between surface and subsurface processes; data on the size partitioning of net primary production (NPP) and subsequent transformations prior to export; estimates of the ratio of algal- to faecal-mediated vertical export flux. At ALOHA, phytoplankton were characterized by low stocks, NPP, Fv/Fm (N-limited), and were dominated by picoplankton. The HNLC waters at K2 were characterized by both two-fold changes in NPP and floristic shifts (high to low proportion of diatoms) between deployment 1 and 2. Prediction of export exiting the euphotic zone was based on size partitioning of NPP, a copepod-dominated foodweb and a ratio of 0.2 (ALOHA) and 0.1 (K2) for algal:faecal particle flux. Predicted export was 20–22 mg POC m−2 d−1 at ALOHA (i.e. 10–11% NPP (0–125 m); 1.1–1.2×export flux at 150 m (E150). At K2, export was 111 mg C m−2 d−1 (21% NPP (0–50 m); 1.8×E150) and 33 mg POC m−2 d−1 (11% NPP, 0–55 m); 1.4×E150) for deployments 1 and 2, respectively. This decrease in predicted export at K2 matches the observed trend for E150. Also, the low attenuation of export flux from 60 to 150 m is consistent with that between 150 and 500 m. This strong surface–subsurface coupling suggests that phytoplankton productivity and floristics play a key role at K2 in setting export flux, and moreover that pelagic particle transformations by grazers strongly influence to what extent sinking particles are further broken down in the underlying waters of the Twilight Zone.

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.

Krill are important grazers on diatoms and critical prey items for many high level carnivores in Monterey Bay and elsewhere along the California coast. Here, some of the higher level consumers have recently been shown to be severely affected by the toxin, domoic acid (DA), a secondary metabolite of some species of the diatom Pseudo-nitzschia. To understand the potential role of krill in vectoring DA from diatoms to large predators, several grazing experiments were conducted. Field-collected Euphausia pacifica and Thysanoessa spinifera were fed on a diet of toxic and non-toxic Pseudo-nitzschia species. Gut evacuation rates of krill and CHN analysis of the algae were obtained concurrently to determine gut residence time and nutritional value of the food. Our results from a short-term (6 h) grazing experiment demonstrated that both E. pacifica and T. spinifera consumed toxic Pseudo-nitzschia multiseries but the responses of the two krill species differed to a degree, with E. pacifica having the higher weight-specific feeding rate. Results from a longer-term (24 h) grazing experiment showed that E. pacifica had a different, interrupted grazing pattern and showed no immediate ill effects when consuming toxic P. multiseries as contrasted with its more constant feeding pattern on non-toxic Pseudo-nitzschia pungens. We show that toxin loads in krill digestive tracts, estimated from feeding rates and gut residence time measured here, match the observed body burdens of DA measured in field-collected krill during toxic blooms. Such data are important for predicting toxin transfer from krill to higher trophic levels during blooms of toxic algae. As an example of this transfer, we show the vulnerability of a krill-feeding seabird, Cassin's Auklet (Ptychoramphus aleuticus) to DA likely vectored by krill during toxic Pseudo-nitzschia blooms.

Blooms of domoic acid (DA) synthesizing diatoms (Pseudo-nitzschia spp.) have been associated with the death and injury of hundreds of marine shorebirds and mammals, exposed humans to potentially serious health risks, and threatened to significantly impact coastal fisheries and commerce dependent on marine resources. While indicator organisms are widely utilized to monitor for marine biotoxins like paralytic shellfish poisoning toxins, a reliable intertidal indicator species to monitor DA remains to be identified. Here we evaluate and confirm the utility of the common sand crab (Emerita analoga) as an indicator for DA in comparison with sea mussels (Mytilus californianus). Mussels and sand crabs, collected from natural populations in Santa Cruz, California (April 1999-February 2000), were tested for DA using the HPLC-UV method. Toxin loads in sand crabs ranged from below detectable limits to 13.4 micro g DA g(-1) and coincided with the abundance of DA producing Pseudo-nitzschia species nearshore. Toxin levels in mussels collected during the study period were below HPLC-UV detectable limits. The rise and fall of DA in sand crabs in synchrony with Pseudo-nitzschia abundance, combined with this common intertidal species' accessibility and ease of DA extraction, clearly indicate the utility of sand crabs as a reliable, cost-effective monitoring tool for DA in the nearshore coastal environment.

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.

Over the past decade, blooms of the domoic acid (DA) producing diatom Pseudo- nitzschia have been responsible for numerous deaths of marine mammals and birds in Monterey Bay, California. Euphausiids (krill) are important members of the local zooplankton grazer community and comprise the primary diet of squid, baleen whales, and many seabirds. Krill are thus a key potential vector for the transfer of DA to higher trophic level organisms in Monterey Bay. A better understand- ing of the quantitative trophic interactions and body burden of DA in krill is required to predict whether they can act as an effective vector for this neurotoxin. Here we report results of toxin analy- ses and gut content examinations of krill Euphausia pacifica collected from Monterey Bay in 2000. Corresponding counts of toxic Pseudo-nitzschia species in the water and their cellular DA concen- trations were also obtained at the collection sites. Toxin analysis by receptor binding assay demon- strated that DA in krill tissue varied between 0.1 to 44 µg DA equiv. g -1 tissue (confirmed by tandem mass spectrometry), with levels corresponding to the abundance of toxic Pseudo-nitzschia species present in the water. The occurrence of Pseudo-nitzschia australis frustules in the digestive tract of E. pacifica verified that a toxic species of this diatom was an important part of their diet and thus impli- cated this phytoplankter as the source of DA. These findings provide compelling evidence for the role of krill as a potential transfer agent of the phycotoxin DA to higher trophic levels in marine food web.

The planktivorous northern anchovy is a prominent vector of the phycotoxin domoic acid (DA) to organisms at higher trophic levels, including fish-eating seabirds and mammals. Although there are abundant data reporting DA-induced excitotoxic symptoms in higher vertebrates, to date there has been no reported evidence of neurotoxic effects in lower vertebrate vectors such as fish. To explain this apparent lack of toxicity, it has been suggested that DA may not reach the brain in anchovies and/or that fish are not as sensitive neurologically to DA. In the present study, intracoelomic (IC) injection of DA, at doses ranging from 1 to 14 μg DA g−1 total fish weight, resulted in severe neurotoxic symptoms such as spinning, disorientation, inability to school, and mortality, indicating that anchovies are neurologically susceptible and that DA crosses the blood–brain barrier in fish. An ED50 of 3.2 μg DA g−1 total body weight was determined via IC injection of DA in 83 anchovies. Comparable intraperitoneal injection studies with mice, rats, and monkeys report similar DA-induced neurotoxic symptoms at doses near 3.2 μg DA g−1, suggesting a similar neurologic sensitivity and mechanism of toxicity between anchovies and mammals. DA tissue distribution measurements from freshly collected field-exposed anchovies and orally gavaged anchovies indicate that DA uptake from the gastrointestinal tract does occur. Levels as high as 1,175 μg DA g−1 were measured in anchovy viscera, while muscle and brain tissue DA levels were 3 orders of magnitude lower, indicating low but measurable DA uptake. Further evidence is needed to confirm that uptake is sufficient during field events to induce symptoms in anchovies. Our work provides the first reported evidence of neurotoxic symptoms in fish and suggests that anchovies may be affected by DA during toxic diatom blooms. If sufficient uptake occurs, DA-induced neurotoxic symptoms and mortality may make fish easier prey targets, thereby selecting for the highest toxin levels transferred, as well as providing a possible pathway for the transfer of DA to benthic communities.

The occurrence of an unusual mortality event involving California sea lions (Zalophus californianus) along the central California coast in May 1998 was recently reported. The potent neurotoxin domoic acid (DA), produced naturally by the diatom Pseudo-nitzschia australis and transmitted to the sea lions via planktivorous northern anchovies (Engraulis mordax), was identified as the probable causative agent. Details of DA analyses for anchovy tissues and sea lion feces are described. Domoic acid levels were estimated in anchovy samples by HPLC-UV, and in sea lion feces using the same method as well as a microplate receptor binding assay, with absolute confirmation by tandem mass spectrometry. The highest DA concentrations in anchovies occurred in the viscera (223 +/- 5 microg DA g(-1)), exceeding values in the body tissues by seven-fold and suggesting minimal bioaccumulation of DA in anchovy tissue. HPLC values for DA in sea lion fecal material (ranging from 152 to 136.5 microg DA g(-1)) required correction for interference from an unidentified compound. Inter-laboratory comparisons of HPLC data showed close quantitative agreement. Fecal DA activity determined using the receptor binding assay corresponded with HPLC values to within a factor of two. Finally, our detection of P. australis frustules, via scanning electron microscopy, in both anchovy viscera and fecal material from sea lions exhibiting seizures provides corroborating evidence that this toxic algal species was involved in this unusual sea lion mortality event.

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

Gelatinous polymers including extracellular polymeric substances (EPSs) are fundamental to biophysical processes in aquatic habitats, including mediating aggregation processes and functioning as the matrix of biofilms. Yet insight into the impact of these sticky molecules on the environmental transmission of pathogens in the ocean is limited. We used the zoonotic parasite Toxoplasma gondii as a model to evaluate polymer-mediated mechanisms that promote transmission of terrestrially derived pathogens to marine fauna and humans. We show that transparent exopolymer particles, a particulate form of EPS, enhance T. gondii association with marine aggregates, material consumed by organisms otherwise unable to access micrometre-sized particles. Adhesion to EPS biofilms on macroalgae also captures T. gondii from the water, enabling uptake of pathogens by invertebrates that feed on kelp surfaces. We demonstrate the acquisition, concentration and retention of T. gondii by kelp-grazing snails, which can transmit T. gondii to threatened California sea otters. Results highlight novel mechanisms whereby aquatic polymers facilitate incorporation of pathogens into food webs via association with particle aggregates and biofilms. Identifying the critical role of invisible polymers in transmission of pathogens in the ocean represents a fundamental advance in understanding and mitigating the health impacts of coastal habitat pollution with contaminated runoff.

Toxoplasma gondii is a land-derived parasite that infects humans and marine mammals. Infections are a significant cause of mortality for endangered southern sea otters (Enhydra lutris nereis), but the transmission mechanism is poorly understood. Otter exposure to T. gondii has been linked to the consumption of marine turban snails in kelp (Macrocystis pyrifera) forests. It is unknown how turban snails acquire oocysts, as snails scrape food particles attached to surfaces, whereas T. gondii oocysts enter kelp beds as suspended particles via runoff. We hypothesized that waterborne T. gondii oocysts attach to kelp surfaces when encountering exopolymer substances (EPS) forming the sticky matrix of biofilms on kelp, and thus become available to snails. Results of a dietary composition analysis of field-collected snails and of kelp biofilm indicate that snails graze the dense kelp-biofilm assemblage composed of pennate diatoms and bacteria inserted within the EPS gel-like matrix. To test whether oocysts attach to kelp blades via EPS, we designed a laboratory experiment simulating the kelp forest canopy in tanks spiked with T. gondii surrogate microspheres and controlled for EPS and transparent exopolymer particles (TEP - the particulate form of EPS). On average, 19% and 31% of surrogates were detected attached to kelp surfaces covered with EPS in unfiltered and filtered seawater treatments, respectively. The presence of TEP in the seawater did not increase surrogate attachment. These findings support a novel transport mechanism of T. gondii oocysts: as oocysts enter the kelp forest canopy, a portion adheres to the sticky kelp biofilms. Snails grazing this biofilm encounter oocysts as 'bycatch' and thereby deliver the parasite to sea otters that prey upon snails. This novel mechanism can have health implications beyond T. gondii and otters, as a similar route of pathogen transmission may be implicated with other waterborne pathogens to marine wildlife and humans consuming biofilm-feeding invertebrates.

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.

Near-surface waters ranging from the Pacific subarctic (58°N) to the Southern Ocean (66°S) contain the neurotoxin domoic acid (DA), associated with the diatom Pseudo-nitzschia . Of the 35 stations sampled, including ones from historic iron fertilization experiments (SOFeX, IronEx II), we found Pseudo-nitzschia at 34 stations and DA measurable at 14 of the 26 stations analyzed for DA. Toxin ranged from 0.3 fg·cell −1 to 2 pg·cell −1 , comparable with levels found in similar-sized cells from coastal waters. In the western subarctic, descent of intact Pseudo-nitzschia likely delivered significant amounts of toxin (up to 4 μg of DA·m −2 ·d −1 ) to underlying mesopelagic waters (150–500 m). By reexamining phytoplankton samples from SOFeX and IronEx II, we found substantial amounts of DA associated with Pseudo-nitzschia . Indeed, at SOFeX in the Antarctic Pacific, DA reached 220 ng·L −1 , levels at which animal mortalities have occurred on continental shelves. Iron ocean fertilization also occurs naturally and may have promoted blooms of these ubiquitous algae over previous glacial cycles during deposition of iron-rich aerosols. Thus, the neurotoxin DA occurs both in coastal and oceanic waters, and its concentration, associated with changes in Pseudo-nitzschia abundance, likely varies naturally with climate cycles, as well as with artificial iron fertilization. Given that iron fertilization in iron-depleted regions of the sea has been proposed to enhance phytoplankton growth and, thereby, both reduce atmospheric CO 2 and moderate ocean acidification in surface waters, consideration of the potentially serious ecosystem impacts associated with DA is prudent.

Domoic acid (DA) is a neurotoxin that causes amnesic shellfish poisoning, and fish are recog- nized vectors of DA to marine fauna. However, the exposure of anglers through consumption of DA- contaminated fish is unknown. We measured DA in 11 fish species targeted by Santa Cruz Wharf (SCW) anglers in Monterey Bay, California, USA, and sur- veyed anglers regarding their fish consumption pat- terns. In addition, we used California mussel Mytilus californianus DA data provided by the state of Califor- nia and our measurements of DA in seawater to exam- ine the associations between DA in fish viscera versus in mussels and seawater. DA was detected in the vis- cera of 7 fish species commonly consumed by anglers, and toxin uptake in fishes varied according to their diet. DA was almost entirely in the viscera, with low DA concentrations detected in muscle tissue. The majority of anglers (58% of 565) reported consuming their catch, with a small fraction ingesting the viscera. Total DA concentrations in fish decreased significantly after 11 mo storage at -20°C. DA concentration in sea- water and California mussels was correlated with DA in the viscera of some but not all fish groups. We con- clude that SCW anglers who consume their catch are exposed to asymptomatic DA doses, and that exposure is a function of the species and parts consumed, as well as storage methods and DA levels in the seawater when the fish are caught.

Sedimentation of organic matter from the ocean's surface layers is intimately tied to biological events within the euphotic zone. Although the sedimentation rate is usually found to be positively correlated with primary production, the biological basis for the correlation is not well understood. In eutrophic environments, algal populations or large fecal pellets can account for high mass fluxes. The types of particles leaving oligotrophic systems, in contrast, are less clear. Similarly, various mechanisms have been invoked to explain the loss of particles with depth, but little direct evidence is available to distinguish among the possibilities. The fundamental causes of differences in export rates and of the rapid loss of particles at depth, however, will be reflected in the changing composition of particles across a productivity gradient and down through the water column. We have attempted to investigate the biological processes leading to the productivity-flux relationship and the depth-related losses, using Vertex samples from particle interceptor traps deployed in the Northeastern Pacific between 1980 and 1984. We found the previously reported correlation between production and flux in the Vertex data set ( Pace, Knauer, Karl and Martin , 1987) to result from related changes in intact and presumably living organisms in trap samples, not from non-living particles. The production-flux correlation depended, however, entirely on results from an upwelling station: when data from this station were excluded, no pattern was observed among the remaining 6 stations. Phytoplankton flux at the base of the euphotic zone was likewise significantly correlated with primary production, and the relationship persisted even after data from the upwelling station were removed. Important live contributors to traps also included sarcodine protozoans (foraminiferans and radiolarians), eggs of invertebrates, and invertebrate larvae too small to be removed as “swimmers”. (The present study focuses on smaller or unicellular organisms; another study considers also the role of larger, but also cryptic, “swimmers”: Michaels, Silver, Gowing and Knauer , in press). The flux of non-living materials, including fecal pellets and amorphous aggregates, was not related to primary production, nor was there a correlation between obvious parameters of fecal pellets (i.e. average size or numbers) and production. These results raise questions about the meaning of the term “particle flux”. An average of at least 35%, with a range of 11–80% (minimal values, because larger organisms were not included), of the carbon flux leaving the euphotic zone consisted of algae, protozoans, and small metazoans that may have been executing vertical movements as part of a life history strategy. Furthermore, these organisms continued to be important in the mesopelagic zone, where the sarcodines were sometimes substantive contributors (average of 12%, range up to 49%) to the carbon flux. The declining contribution of these living organisms within traps at depth can account for some of the decreases in carbon flux that have been interpreted as “regeneration”. Clearly, reasonable inferences from traps require a better understanding of the nature of the “particles”, and particularly, the contribution of living organisms to trap collections.

The planktonic ciliateStrombidium capitatum (Leegaard, 1915) Kahl, 1932 retains functional chloroplasts derived from ingested algal cells. Chloroplast replacement and aging were experimentally investigated in cultured ciliates provided with a cryptophyte (Pyrenomonas salina), a prymnesiophyte (Isochrysis galbana) and a prasinophyte (Pyramimonas sp.) as sources of plastids. All three algae were ingested and chloroplasts from all were retained by the ciliate. Within 15 min of exposure to the cryptophyte, this alga was taken up by the ciliates. Initially, most of the cryptophyte chloroplasts were in intact algal cells in ciliate vacuoles. By 2 h, cryptophyte plastids were commonly found free in the ciliate cytoplasm. WhenS. capitatum was switched from a diet containing cryptophytes to a non-cryptophyte diet, most cryptophyte chloroplasts were diluted out of the ciliates by cell division and/or replaced by non-cryptophyte chloroplasts within 9 h. When the ciliates are not provided with algae, they decrease in size and number. However, the starving ciliate cells contain some chloroplasts for as long as they live (40 h or more). Under these conditions, cryptophyte chloroplasts persist longer than the other chloroplast types. Our observations suggest that chloroplast retention times inS. capitatum depend on the type of chloroplast as well as the availability of phytoplankton containing suitable new chloroplasts, and probably also on the physiological states of the ingested algae and the ciliates. It is interesting that we were not able to grow this ciliate when we provided it only with prey that lacked chloroplasts.

Sediment traps are the major oceanographic tool for collecting passively sinking particulate material (the “particle flux”) in the ocean. Sediment traps in the upper ocean also collect actively sinking zooplankton that are usually manually removed prior to analysis. Microscospic analysis of sediment trap samples collected over a 19-month period in the eastern North Pacific reveals that zooplankton “swimmers” are a larger problem than previously recognized. Zooplankton that are cryptic (i.e. difficult to see or distinguish from the detrital material) and difficult to remove (principally gelatinous zooplankton) may have contributed up to 20 mg C m −2 day −1 to the “particulate flux”, with the highest values in the upper 150 m. This swimmer problem is in addition to the previously recognized presence of crustaceans and other large metazoans in traps. Additionally, the detritus-laden, mucous-feeding structures (houses)of larvaceans probably enter the traps with the larvaceans and would be impossible to remove. We estimate that the contribution of the cryptic swimmers and larvacean houses could be as much as 96% of the measured carbon flux. The contribution is greatest in the euphotic zone and drops sharply below 200 m. Subtracting out this potential artifact at the VERTEX station results in vertical profiles of organic carbon flux that differ dramatically from the standard flux profile for carbon in the upper ocean: specifically, the implied “regeneration” rate is greatly reduced. Screened traps (300 μm screens below the baffles) contained numerous metazoans smaller than the screen mesh size. These traps also contained lower levels of other types of sinking particles, and it is unclear to what extent the screens reduced the relative contribution of swimmers to the trap-collected carbon. Although the expanded swimmer problem presented here is now documented at just the VERTEX site, we expect it exists elsewhere. The extent of this swimmer problem requires resolution before sediment traps, especially those deployed in the upper few 100 m, can be used to measure the “flux of particulate material.”

Harmful algal blooms are increasing worldwide, including those of Pseudo-nitzschia spp. producing domoic acid off the California coast. This neurotoxin was first shown to cause mortality of marine mammals in 1998. A decade of monitoring California sea lion ( Zalophus californianus ) health since then has indicated that changes in the symptomatology and epidemiology of domoic acid toxicosis in this species are associated with the increase in toxigenic blooms. Two separate clinical syndromes now exist: acute domoic acid toxicosis as has been previously documented, and a second novel neurological syndrome characterized by epilepsy described here associated with chronic consequences of previous sub-lethal exposure to the toxin. This study indicates that domoic acid causes chronic damage to California sea lions and that these health effects are increasing.

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.

Domoic acid (DA) is a potent food web transferred algal toxin that has caused dramatic mortality events involving sea birds and sea lions. Although no confirmed DA toxicity events have been reported in whales, here we present data demonstrating that humpback and blue whales are exposed to the toxin and consume DA contaminated prey. Whale fecal samples were found to contain DA at levels ranging from 10 to 207microg DA g(-1) feces via HPLC-UV methods. SEM analysis of whale feces containing DA, collected from krill-feeding whales, revealed the presence of diatom frustules identified as Pseudo-nitzschia australis, a known DA producer. Humpback whales were observed feeding on anchovies and sardines that contained DA at levels ranging from 75 to 444microg DA g(-1) viscera. DA contamination of whale feces and fish occurred only during blooms of toxic Pseudo-nitzschia. Additionally, several novel fish species collected during a toxic diatom bloom were tested for DA. Fish as diverse as benthic sanddabs and pelagic albacore were found to contain the neurotoxin, suggesting that DA permeates benthic as well as pelagic communities.

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.

The neurotoxin domoic acid (DA) was identified as the probable cause of death and neurological illness for approximately 70 California sea lions, Zalophus californianus, along the central California coast in May 1998. The apparent vector for sea lion intoxication was the filter-feeding northern anchovy, Engraulis mordax, via transfer of DA from the diatom, Pseudo-nitzschia australis, a natural source of this toxin. Both DA and siliceous frustules of P. australis were found in anchovy gut contents and in fecal material collected from sea lions exhibiting seizures. Anchovies contained 200.29±3.34 μg DA/g in viscera samples, 49.69±0.79 μg DA/g in whole body samples and 35.14±0.47 μg DA/g in body tissue samples. DA concentrations in sea lion fecal material ranged from 1.31 to 182.01 μg DA/g. This is the first documented case of DA toxicity in a marine mammal species.

The fecal pellets of zooplankton are thought to be major carriers of organic matter from surface to deeper waters of the oceans. As the pellets descend, they release soluble components, partially due to breakdown by associated microorganisms. Previous laboratory work of other investigators has suggested that the surface of a fecal pellet rapidly acquires bacteria, which increase in abundance until they and their protozoan consumers disrupt the pellet membrane, spilling contents into the water. In contrast, our field collections of fecal pellets from free-floating particle interceptor traps (from the “Vertex” project off Central California in 1980 and off Mexico in 1981), suggest that microbial decomposition probably is initiated in the sea from inside the fecal pellets. Transmission and scanning electron microscopy indicate that bacterial populations are most abundant in the interior of fecal pellets obtained from the sea, but that the same pellets will acquire the surface bacterial lawn typically observed in laboratory studies if maintained aboard ship. If the fecal pellets are decomposed from the inside, then the principal agents are enteric bacteria or ingested, digestion-resistant bacteria, or both. Such bacteria may differ metabolically from those that colonize the fecal pellet surfaces. Further-more, the abundance of healthy-appearing bacteria inside the pellets suggests that their metabolic activities may produce microhabitats of reduced oxygen tension that could differ considerably from that of the pellet exteriors. Decomposition in these semi-enclosed microenvironments may proceed in a manner not yet predicted by models that attribute decomposition to well-aerated, surface-dwelling bacterial populations on fecal pellets in the sea.

Macroscopic aggregates of detritus, living organisms and inorganic matter known as marine snow, have significance in the ocean both as unique, partially isolated microenvironments and as transport agents: much of surface-derived matter in the ocean fluxes to the ocean interior and the sea floor as marine snow. As microhabitats, marine snow aggregates contain enriched microbial communities and chemical gradients within which processes of photosynthesis, decomposition, and nutrient regeneration occur at highly elevated levels. Microbial communities associated with marine snow undergo complex successional changes on time scales of hours to days which significantly alter the chemical and biological properties of the particles. Marine snow can be produced either de novo by living plants and animals especially as mucus feeding webs of zooplankton, or by the biologically-enhanced physical aggregation of smaller particles. By the latter pathway, microaggregates, phytoplankton, fecal pellets, organic debris and clay-mineral particles collide by differential settlement or physical shear and adhere by the action of various, biologically-generated, organic compounds. Diatom flocculation is a poorly understood source of marine snow of potential global significance. Rates of snow production and breakdown are not known but are critical to predicting flux and to understanding biological community structure and transformations of matter and energy in the water column. The greatest challenge to the study of marine snow at present is the development of appropriate technology to measure abundances and characteristics of aggregates in situ.