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The use of environmental DNA (eDNA) for studying the ecology and variability of life in the sea is reviewed here in the context of US interagency Marine Biodiversity Observation Network (MBON) projects. Much of the information in this paper comes from samples collected within US National Marine Sanctuaries. The field of eDNA is relatively new but growing rapidly, and it has the potential to disrupt current paradigms developed on the basis of existing measurement methods. After a general review of the field, we provide specific examples of the type of information that eDNA provides regarding the changing distribution of life in the sea over space (horizontally and vertically) and time. We conclude that eDNA analyses yield results that are similar to those obtained using traditional observation methods, are complementary to them, and because of the breadth of information provided, have the potential to improve conservation and management practices. Moreover, through technology development and standardization of methods, eDNA offers a means to scale biological observations globally to a level similar to those currently made for ocean physics and biogeochemistry. This scaling can ultimately result in a far better understanding of global marine biodiversity and contribute to better management and sustainable use of the world ocean. Improved information management systems that track methods and associated metadata, together with international coordination, will be needed to realize a global eDNA observation network. [ABSTRACT FROM AUTHOR]

Abstract Monterey Bay, California, has been sampled by ship at 2–3 week intervals during 1989–2011. Here we present the resulting time series of temperature, salinity, nitrate, chlorophyll and primary production over the 23-year record and correlate the nonseasonal anomalies and four Pacific Basin-scale climate indices. About half of Monterey Bay variability was captured by the seasonal cycle while half remained in the anomalies. Correlations revealed strong associations between temperature, salinity and nitrate, and weaker correlations between these anomalies and euphotic zone-integrated chlorophyll and primary production. Sub-euphotic zone physical and particularly nitrate anomalies were better predictors of the euphotic zone biological variables than were their surface anomalies. The strongest correlations between temperature, salinity and nitrate anomalies occurred in spring and summer (e.g. during upwelling). Conversely, spring and summer nitrate were less well correlated with the biological variables than during the remaining months due to nonlinearity in the biological response. Lagged cross-correlations generally showed decreasing correlation with increasing lag (0–12 months). The Monterey Bay anomalies were then correlated with four Pacific Basin-scale climate indices --- the Multivariate ENSO Index (MEI), the Pacific Decadal Oscillation (PDO), the El Niño Modoki Index (EMI), and the North Pacific Gyre Oscillation (NPGO). Temperature, salinity and nitrate were well-correlated to the indices (accounted for 20–25% of the variance) whereas chlorophyll and primary production were weakly- and often insignificantly-correlated with the indices (accounted for 4–10% of the variance). The MEI was most strongly and the EMI least strongly (usually insignificantly) correlated with the anomalies. Most indices were also significantly cross-correlated over the observation period. Seasonally, the MEI produced strong winter and weaker summer associations with temperature, salinity and nitrate, and weak negative correlations with the biological anomalies all year. The PDO showed similar but weaker associations. The EMI correlations were weak but revealed seasonal cycles similar in phasing to those of the MEI. The NPGO exhibited positive relationships with salinity, nitrate and the biological anomalies, all peaking in summer and fall, and a weak negative association with temperature. Index-leads-anomaly correlations did not generally strengthen with lag (0–12 months). All the anomalies exhibited trends, with temperature decreasing and salinity, nitrate and the biological anomalies increasing. Except for 200 m temperature, these trends were significant and substantial, with surface nitrate and euphotic-zone integrated chlorophyll and primary production increasing 1.69 uM, 7.27 mg m−2 and 510 mgC m−2 d−1 per decade, respectively. These Monterey Bay trends are consistent with other California Current results and Pacific Basin index trends over the same period, indicating that Monterey Bay fluctuates with the California Current and North Pacific Basin. [ABSTRACT FROM AUTHOR]

Abstract Sediment traps were deployed at two depths (300 m and 1200 m) off Monterey Bay (36°40′N and 122°25′W, Central California) for 7.3 years (1998–2005). The sediment trap data provided information about the quantity and quality of settling material, and allowed exploration of the relationship of the sinking material with the environmental conditions in this coastal upwelling region. The magnitude and composition of the settling material were highly variable over time. Organic carbon (C org) fluxes ranged between 4–296 mg C m−2 day−1 and 0.1–142 mg C m−2 day−1 for shallow and deep sediment traps, respectively. The time series of C org vertical flux was characterized by pulses of intense fluxes that were associated with peaks of primary production, generally during upwelling periods. Despite considerable variability, fluxes varied seasonally with highest values during the upwelling season and the lowest in winter. Attenuation of C org vertical fluxes with depth (300 m vs. 1200 m) varied between 31% and 24% except for the late upwelling period, when there was an increase with depth likely due to resuspension of material from Monterey Canyon. Calculation of a seasonal vertical budget of organic carbon off Monterey Bay resulted in a transfer between 4.0% and 4.9% of the primary production to the deep ocean, suggesting that coastal upwelling efficiently sequestered CO 2. [ABSTRACT FROM AUTHOR]

Abstract Anthropogenic input of carbon dioxide (CO 2) into the atmosphere and its uptake by the ocean with associated changes in ocean chemistry have created an urgent need to expand coverage of sea surface and atmospheric carbon dioxide observations. Conventional sampling platforms (e.g. ships and moorings) do not provide the spatial and temporal resolution needed to assess the effects of rapidly changing carbon dioxide conditions and are expensive to operate. Through a series of deployments beginning in March 2012, two versions of the Wave Glider autonomous surface vehicles from Liquid Robotics, Inc. have been instrumented with sensors to measure pH, partial pressure of CO 2 (p CO 2) of the atmosphere and sea surface, and wind speed and direction, from which instantaneous sea-air fluxes of CO 2 can be calculated. These deployments, most near Monterey Bay, California, were highly correlated with Δ p CO 2 measurements obtained from the Monterey Bay Aquarium Research Institute's (MBARI) long-term mooring station M1, as well as from shipboard observations. In the central California upwelling system with highly variable p CO 2 levels, the gliders captured large spatial gradients associated with upwelling fronts. Differences in sea surface p CO 2 as large as 470 μ atm over < 0.5 km were observed. Unlike traditional ship sampling methods, however, this new generation of sampling platforms is capable of continuous long-term (months) deployments at a fraction of the cost. The vehicles thus have the potential of filling important gaps in present understanding of the effects of global change on ocean chemistry. [ABSTRACT FROM AUTHOR]

Monterey Bay and contiguous waters of the California Current System have been observed repeatedly since 1929, most intensively since 1989 with ships, moorings, and autonomous vehicles. Here, seasonal, interannual, and multidecadal variations are linked to regional weather and large-scale climate ocean-atmosphere dynamics. In the springtime, the Northeast Pacific subtropical high-pressure system strengthens, intensifying northwesterly alongshore winds. These winds drive coastal upwelling that fertilizes nearshore surface water with phytoplankton nutrients, resulting in a dramatic increase in biological productivity. Upwelling weakens over summer into fall, allowing nutrient-depleted offshore water to move toward the coast. Southerly winter storm winds deepen the mixed layer and further enhance onshore flow. El Niño interrupts these seasonal cycles with varying intensity every three to eight years, but typically peaks during the low-productivity winter season, lessening its biological impact. Over the 1989-2016 period of observation, a negative phase of the multidecadal Pacific Decadal Oscillation is observed as a 15-year cool period following the strong 1997-1998 El Niño. Two recently identified basin-scale phenomena, the central Pacific El Niño Modoki and the North Pacific Gyre Oscillation, increased in strength during this period. In Monterey Bay, primary productivity increased substantially during the cool period, at about 3% per year. This shift also marked the beginning of a monotonic decline in subsurface oxygen, which decreased by 3% annually in the 300-400 m depth horizon, above the oxygen minimum zone. Anthropogenically driven increases in surface pCO2 and acidity (pH) are notable in Monterey Bay in spite of high near-surface variability. Recently, over 2014-2016, Monterey Bay has warmed, interrupting the 1988-2012 cooling trend. Even with the warm years included, however, there is no overall increasing trend in temperature at any depth from 1988 to the present. A recompilation of historical temperature data back to 1929 indicates that over this longer period, average and cool years have not been significantly different, but warm episodes have been hotter over the last few decades, leading to a trend of increasing temperature over the past 89 years. The 2014-2016 warm period included "the Blob" and an El Niño, and is reminiscent of similar conditions in the early 1940s. It is not known if the warm conditions will continue, or we will return to a cooler and drier than average period. Our observations highlight the value of long-term data. Such data collections will need to be automated to increase their value and sustainability. [ABSTRACT FROM AUTHOR]

A simple combination of wind-driven nutrient upwelling, surface currents, and plankton growth/grazing equations generates zooplankton patchiness and hotspots in coastal upwelling regions. Starting with an initial input of nitrate from coastal upwelling, growth and grazing equations evolve phytoplankton and zooplankton over time and space following surface currents. The model simulates the transition from coastal (large phytoplankton, e.g., diatoms) to offshore (picophytoplankton and microzooplankton) communities, and in between generates a large zooplankton maximum. The method was applied to four major upwelling systems (California, Peru, Northwest Africa, and Benguela) using latitudinal estimates of wind-driven nitrate supply and satellite-based surface currents. The resulting zooplankton simulations are patchy in nature; areas of high concentrations coincide with previously documented copepod and krill hotspots. The exercise highlights the importance of the upwelling process and surface currents in shaping plankton communities. [ABSTRACT FROM AUTHOR]

Photosynthesis in the surface ocean converts atmospheric CO2 into organic particles, with the fraction sinking to depth representing a major part of the ocean's biological pump. Although sinking particles are known to be altered by attached‐bacteria during transit, most prior organic geochemical data indicated only minor replacement of plankton‐derived particles by bacterial material. We exploit bacteria‐specific biomarkers (d‐amino acids) in a multi‐year sediment trap in the Pacific Ocean (1,200 m) and suggest a different view. Major d‐amino acids were consistently measured at abundance demonstrating widespread accumulation of bacterial material in sinking particles. Bacterial detritus was estimated to account for up to 19% of particulate organic carbon and up to 36% of particulate nitrogen, much higher than cell count‐based values. The bacterial relative contribution increased with decreasing export production. Our results indicate that bacterial material constitutes an underappreciated component of the biological pump, a role expected to rise as the ocean warms. Plain Language Summary: Phytoplankton photosynthesis in the surface ocean plays a critical role in stabilizing atmospheric CO2. It converts CO2 into organic particles that sink and are reworked by colonizing bacteria. Bacteria respire most particles back to CO2 while also transforming some into their cell components. Although the involvement of bacteria can replace the plankton‐derived particles to bacterial material, most past organic geochemical data have suggested that the deep‐sea particles are still comprised mainly of plankton remnants. This renders the contribution of bacterial material to total particle export an unresolved and yet important question, because the source and composition of particles are important to their fate in the ocean. Here, we analyzed bacteria‐specific molecules in deep‐sea sinking particles and found that bacterial organic matter actually made up a large fraction of the particles. In addition, the relative contribution of bacterial material to the sinking particles increased as the total carbon export decreased. This has important implications for the future ocean carbon cycle, because modeling work predicts a scenario of lower carbon export to the deep sea as the ocean warms. In this context, our findings imply a greater importance of bacteria in marine organic matter export and sequestration in a warming ocean. Key Points: We exploit d‐amino acid biomarkers in multi‐year deep‐sea sediment trap time series to evaluate bacterial contribution to total exportBacterial detritus accounts for up to 19 ± 8% of sinking POC and up to 36 ± 14% of PN, making up a large unrecognized part of biological pumpThe relative contribution of bacterial detritus to sinking particles increases with decreased export production [ABSTRACT FROM AUTHOR]

The regulation of seasonal satellite-derived primary production (PP) was investigated within a 150 km coastal box in four eastern boundary upwelling systems (EBUS): California, Peru, Northwest Africa and Benguela. The following regulating factors were considered: (1) wind-driven nitrate supply; (2) iron supply inferred from proxies (shelf mud belt width, modeled atmospheric iron deposition, river discharge); (3) temperature; (4) light and (5) physical export consisting of offshore export, eddy-driven and wind-driven subduction. The ratio of potential new production (carbon-equivalent of nitrate supply) to primary production, termed the N-ratio, is shown to be an indicator of PP limitation by nitrate supply (low N-ratios) vs. inhibition by other factors (high N-ratios). The factors regulating PP were assessed by analyzing the N-ratios and computing spatial correlations between PP and each factor each month. The regulation of primary production was found to vary spatially, seasonally and from one EBUS to another. Macronutrient supply is shown to be the dominant regulating factor off Northwest Africa and during some seasons and locations in other systems. Light regulation within the mixed layer occurs in all EBUS in winter but may only inhibit PP (high N-ratios) off Peru and Benguela. Evidence for iron limitation was found in each EBUS (except Northwest Africa) at varying levels and was greatest off Peru during austral winter when iron demand by phytoplankton increases due to low light levels. Rapid offshore advection combined with wind-driven and/or eddy-driven subduction may inhibit PP off California. A simple generalization regarding the regulation of primary production in EBUS is not forthcoming. [ABSTRACT FROM AUTHOR]

Nitrification, the microbial oxidation of ammonium to nitrate, is a central part of the nitrogen cycle. In the ocean’s surface layer, the process alters the distribution of inorganic nitrogen species available to phytoplankton and produces nitrous oxide. A widely held idea among oceanographers is that nitrification is inhibited by light in the ocean. However, recent evidence that the primary organisms involved in nitrification, the ammonia-oxidizing archaea (AOA), are present and active throughout the surface ocean has challenged this idea. Here we show, through field experiments coupling molecular genetic and biogeochemical approaches, that competition for ammonium with phytoplankton is the strongest regulator of nitrification in the photic zone. During multiday experiments at high irradiance a single ecotype of AOA remained active in the presence of rapidly growing phytoplankton. Over the course of this three day experiment, variability in the intensity of competition with phytoplankton caused nitrification rates to decline from those typical of the lower photic zone (60 nmol L−1 d−1) to those in well-lit layers (<1 nmol L−1 d−1). During another set of experiments, nitrification rates exhibited a diel periodicity throughout much of the photic zone, with the highest rates occurring at night when competition with phytoplankton is lowest. Together, the results of our experiments indicate that nitrification rates in the photic zone are more strongly regulated by competition with phytoplankton for ammonium than they are by light itself. This finding advances our ability to model the impact of nitrification on estimates of new primary production, and emphasizes the need to more strongly consider the effects of organismal interactions on nutrient standing stocks and biogeochemical cycling in the surface of the ocean. [ABSTRACT FROM AUTHOR]

Abstract: Coastal upwelling along eastern boundaries has fascinated oceanographers for decades. The strong coupling between atmospheric forcing, ocean circulation, biogeochemical cycling, and food web dynamics encouraged oceanographers to conduct multidisciplinary scientific studies that have since become common. Following that tradition, an interdisciplinary approach is taken to highlight differences between the major Eastern Boundary Upwelling Ecosystems (EBUE’s). Ocean basin-scale settings are important determinants of EBUE characteristics. First, trade winds accumulate heat and mass in the western side of the basins, deepening the thermocline in the west and raising it in the east. Second, and especially prominent in the Pacific, these properties are redistributed eastwards on interannual and multidecadal time scales, reducing the characteristically high biological productivity found in the eastern basin margins. Thirdly, north–south patterns of thermocline doming on the equator and deepening in the subtropical gyres, and high latitude weather-driven mixing makes latitude an important characteristic of each EBUE. As such each EBUE has 3–4 well-defined latitudinally distributed biomes. Many enigmas remain regarding EBUE’s including: (1) Why do EBUE’s differ dramatically in fish but not in primary production? (2) What nutrients or other physical properties limit EBUE primary production? (3) What roles do subsurface oxygen minimum zones play in EBUE ecosystems? (4) What role do euphausiids play in the transfer of energy through EBUE food webs? (5) What are the roles of EBUE food webs in the biogeochemical cycling of elements? (6) How inter-connected are biomes of EBUE ecosystems? and (7) Most importantly for society, how will EBUE’s respond to climate and global change. [Copyright &y& Elsevier]

Abstract: The introduction of the SeaWiFS ocean-color instrument in the autumn of 1997 coincided with the onset of perhaps the largest El Niño event of the century, providing us with the opportunity to monitor the impact of such events on biological and bio-optical properties in central California. The increased importance of coastal runoff (both sediments and fresh water) during the winter of 1998 have been striking. Here we evaluate the effects of riverine input to central California immediately following the largest El Niño-influenced winter storm event in central California of February 1998 using shipboard, mooring, and satellite observations from the sea-viewing wide field-of-view sensor (SeaWiFS). Two models were employed to estimate colored dissolved organic matter, (CDOM), which provided similar spatial and temporal patterns of CDOM, but differing absolute concentrations. We observed a 5-fold increase in SeaWiFS-derived chlorophyll concentrations, with a corresponding CDOM signal (estimated absorption at 300nm greater than 0.30m−1) extending to approximately 300km offshore. This event, while anomalous, demonstrates the potential influence of riverine input on the bio-optical properties of the coastal environment extending to several hundred kilometers offshore. [Copyright &y& Elsevier]

Changes in phytoplankton concentration, mixed layer depth, and incident radiation strongly modify the upper- ocean heat budget. An extreme example occurred during the 1997/98 El Niño–La Niña. In the central equatorial Pacific, biological heating of the mixed layer increased from ∼0.1°C month[sup -1] in December 1997 (El Niño) to ∼1.0°C month[sup -1] in July 1998 (La Niña). This change was due to 1) shoaling of the mixed layer from ∼100 to ∼20 m (∼56% of the 0.9°C month[sup -1] increase); 2) a twentyfold increase in surface chlorophyll concentrations (∼29% of the increase), coincident with a shoaling of the subsurface chlorophyll maximum from ∼100 to ∼50 m; and 3) an increase in incident shortwave radiation from ∼175 to 275 W m[sup -2] (∼15% of the increase). The observed range of heating rates (0.1°–1.0°C month[sup -1] ) corresponds closely to the mean condition of the western (oligotrophic) and eastern (mesotrophic) equatorial Pacific, respectively. Increased phytoplankton concentrations act to retain heat near the surface and should result in shallower mixed layer depths. The influence of decadal changes in chlorophyll concentrations on heat storage was also quantified. The observed chlorophyll variability leads to interannual changes in penetrative heat flux (E[sub d,SW,PEN] , the irradiance flux out of the bottom of the mixed layer) of the order of 5 W m[sup -2] , or from 65% to 170% of the mean. This variability is significant when compared with recent work that describes couplings between tropical and global ocean temperature dynamics. The analyses presented here show that satellite and buoy data can be used to accurately and simply estimate the biological contribution to heating for basin-scale studies, and possibly for future improvement of ocean circulation models. [ABSTRACT FROM AUTHOR]

In the Pacific Ocean, air and ocean temperatures, atmospheric carbon dioxide, landings of anchovies and sardines, and the productivity of coastal and open ocean ecosystems have varied over periods of about 50 years. In the mid-1970s, the Pacific changed from a cool “anchovy regime” to a warm “sardine regime.” A shift back to an anchovy regime occurred in the middle to late 1990s. These large-scale, naturally occurring variations must be taken into account when considering human-induced climate change and the management of ocean living resources. [ABSTRACT FROM AUTHOR]

Provides information on a study which applied a modified plankton model to the coastal upwelling ecosystem of Monterey Bay, California. Environmental setting; Details on the model; Results of the study.

Provides information on a study which estimated primary production using phytoplankton utilization of nitrate for the Monterey Bay, California region. Model description; Results and discussion.

Provides information on a study which described time series of temperature, salinity, nitrate, primary production and chlorophyll in a station in Monterey Bay, California. Methods of the study; Results and discussion.

A shutter mechanism for reducing the effects of biofouling on bio-optical instruments deployed on oceanographic moorings has been designed, built, and tested. The initial development was carried out on a spectro-radiometer. The optics of the spectroradiometer are protected by copper shutters that rotate out of the field of view prior to a measurement and rotate back after the measurement is completed. The shutter system can sense an obstruction and, if one is detected, attempt to rotate in the opposite direction. The controlling software stores the home position in the memory so the shutter can return to cover the optics, irrespective of direction of rotation. The system has been tested in the equatorial Pacific, where it has provided five months of data that are unaffected by biofouling. [ABSTRACT FROM AUTHOR]

Presents research which measured dissolvable iron in transects across the California Current System (CCS) in March, 1997 and March, 1998. Role of iron availability in phytoplankton primary productivity; Results of upwelling in the CCS; Results of iron addition to CCS samples; Effects of the 1998 El Nino on iron levels; Primary source of iron in the CCS.

Editorial. Introduces a series of articles which dealt with the California Current System (CCS).

Biodiversity is changing at an accelerating rate at both local and regional scales. Beta diversity, which quantifies species turnover between these two scales, is emerging as a key driver of ecosystem function that can inform spatial conservation. Yet measuring biodiversity remains a major challenge, especially in aquatic ecosystems. Decoding environmental DNA (eDNA) left behind by organisms offers the possibility of detecting species sans direct observation, a Rosetta Stone for biodiversity. While eDNA has proven useful to illuminate diversity in aquatic ecosystems, its utility for measuring beta diversity over spatial scales small enough to be relevant to conservation purposes is poorly known. Here we tested how eDNA performs relative to underwater visual census (UVC) to evaluate beta diversity of marine communities. We paired UVC with 12S eDNA metabarcoding and used a spatially structured hierarchical sampling design to assess key spatial metrics of fish communities on temperate rocky reefs in southern California. eDNA provided a more-detailed picture of the main sources of spatial variation in both taxonomic richness and community turnover, which primarily arose due to strong species filtering within and among rocky reefs. As expected, eDNA detected more taxa at the regional scale (69 vs. 38) which accumulated quickly with space and plateaued at only ~ 11 samples. Conversely, the discovery rate of new taxa was slower with no sign of saturation for UVC. Based on historical records in the region (2000–2018) we found that 6.9 times more UVC samples would be required to detect 50 taxa compared to eDNA. Our results show that eDNA metabarcoding can outperform diver counts to capture the spatial patterns in biodiversity at fine scales with less field effort and more power than traditional methods, supporting the notion that eDNA is a critical scientific tool for detecting biodiversity changes in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Small pelagic fisheries management is difficult because they exhibit large natural abundance fluctuations and are considered forage fish. We discuss the challenges faced by these fisheries within the Marine Stewardship Council (MSC) sustainability certification framework, which evaluates the sustainability of fish stocks, the environmental impact, and effective fisheries management. Certification suspension is frequently linked to the sustainability of stocks. For MSC certification, scientific research will need to play a major role in filling key knowledge gaps, particularly on the nature and causes of ecosystem productivity changes (including climate change), and the role of small pelagics in the ecosystem. Different from other cases where MSC certification creates a direct market incentive through price premiums, in these fisheries, the incentive is related to fisher's public image and improves the bases for negotiation with authorities and the conservation sector. In this context, strategic cooperation between fisheries under the certification process may provide them more benefits than competition. [ABSTRACT FROM AUTHOR]

The author offers information on the interrelation of changing climate and marine ecosystem. He mentions that the marine ecosystems get affected by the climate-driven phenomena as it leads to huge changes in marine ecosystem. He also discusses biological pump of global carbon cycle which has the major role in changing marine ecosystems and habitats.

Long-term biological time series that monitor ecosystems across the ocean’s full water column are extremely rare. As a result, classic paradigms are yet to be tested. One such paradigm is that variations in coastal upwelling drive changes in marine ecosystems throughout the water column. We examine this hypothesis by using data from three multidecadal time series spanning surface (0 m), midwater (200 to 1,000 m), and benthic (~4,000 m) habitats in the central California Current Upwelling System. Data include microscopic counts of surface plankton, video quantification of midwater animals, and imaging of benthic seafloor invertebrates. Taxon-specific plankton biomass and midwater and benthic animal densities were separately analyzed with principal component analysis. Within each community, the first mode of variability corresponds to most taxa increasing and decreasing over time, capturing seasonal surface blooms and lower-frequency midwater and benthic variability. When compared to local wind-driven upwelling variability, each community correlates to changes in upwelling damped over distinct timescales. This suggests that periods of high upwelling favor increase in organism biomass or density from the surface ocean through the midwater down to the abyssal seafloor. These connections most likely occur directly via changes in primary production and vertical carbon flux, and to a lesser extent indirectly via other oceanic changes. The timescales over which species respond to upwelling are taxon-specific and are likely linked to the longevity of phytoplankton blooms (surface) and of animal life (midwater and benthos), which dictate how long upwelling-driven changes persist within each community. [ABSTRACT FROM AUTHOR]

Molecular analysis of environmental DNA (eDNA) can be used to assess vertebrate biodiversity in aquatic systems, but limited work has applied eDNA technologies to marine waters. Further, there is limited understanding of the spatial distribution of vertebrate eDNA in marine waters. Here, we use an eDNA metabarcoding approach to target and amplify a hypervariable region of the mitochondrial 12S rRNA gene to characterize vertebrate communities at 10 oceanographic stations spanning 45 km within the Monterey Bay National Marine Sanctuary (MBNMS). In this study, we collected three biological replicates of small volume water samples (1 L) at 2 depths at each of the 10 stations. We amplified fish mitochondrial DNA using a universal primer set. We obtained 5,644,299 high quality Illumina sequence reads from the environmental samples. The sequence reads were annotated to the lowest taxonomic assignment using a bioinformatics pipeline. The eDNA survey identified, to the lowest taxonomic rank, 7 families, 3 subfamilies, 10 genera, and 72 species of vertebrates at the study sites. These 92 distinct taxa come from 33 unique marine vertebrate families. We observed significantly different vertebrate community composition between sampling depths (0 m and 20/40 m deep) across all stations and significantly different communities at stations located on the continental shelf (<200 m bottom depth) versus in the deeper waters of the canyons of Monterey Bay (>200 m bottom depth). All but 1 family identified using eDNA metabarcoding is known to occur in MBNMS. The study informs the implementation of eDNA metabarcoding for vertebrate biomonitoring. [ABSTRACT FROM AUTHOR]

Omic BON is a thematic Biodiversity Observation Network under the Group on Earth Observations Biodiversity Observation Network (GEO BON), focused on coordinating the observation of biomolecules in organisms and the environment. Our founding partners include representatives from national, regional, and global observing systems; standards organizations; and data and sample management infrastructures. By coordinating observing strategies, methods, and data flows, Omic BON will facilitate the co-creation of a global omics meta-observatory to generate actionable knowledge. Here, we present key elements of Omic BON's founding charter and first activities. [ABSTRACT FROM AUTHOR]

For terrestrial and marine benthic ecologists, landscape ecology provides a framework to address issues of complexity, patchiness, and scale—providing theory and context for ecosystem based management in a changing climate. Marine pelagic ecosystems are likewise changing in response to warming, changing chemistry, and resource exploitation. However, unlike spatial landscapes that migrate slowly with time, pelagic seascapes are embedded in a turbulent, advective ocean. Adaptations from landscape ecology to marine pelagic ecosystem management must consider the nature and scale of biophysical interactions associated with organisms ranging from microbes to whales, a hierarchical organization shaped by physical processes, and our limited capacity to observe and monitor these phenomena across global oceans. High frequency, multiscale, and synoptic characterization of the 4-D variability of seascapes are now available through improved classification methods, a maturing array of satellite remote sensing products, advances in autonomous sampling of multiple levels of biological complexity, and emergence of observational networks. Merging of oceanographic and ecological paradigms will be necessary to observe, manage, and conserve species embedded in a dynamic seascape mosaic, where the boundaries, extent, and location of features change with time. [ABSTRACT FROM AUTHOR]

Pelagic marine Thaumarchaea play a primary role in ammonia oxidation, an integral part of nitrification and the nitrogen cycle. This study examines how physicochemical and biological variables influence rates of nitrification and the distribution, abundance and activity of ammonia oxidizers throughout the dark northeast Pacific Ocean. Nitrification rates are highest near the epipelagic-upper mesopelagic transition and decrease with depth according to a Martin-like power function, suggestive of a coupling to the organic matter flux. In contrast, archaeal and bacterial ammonia monooxygenase ( amoA) gene abundance remains fairly constant throughout the upper mesopelagic. Density-based composites reveal nitrification to be highest in the upper pycnocline, within the nitrate:silica and ammonium maxima, while ammonia-oxidizing archaea (AOA) abundances are highest in the lower pycnocline. Water column group A (WCA) and B (WCB) AOA amoA genes are present throughout the dark ocean but have no relationship to nitrification rates. WCA comprise the majority of the AOA community above 200 m and WCB comprise the majority of it below 500 m, largely because WCA abundances decrease precipitously from 200 m to 500 m. WCA and WCB amoA genes are actively transcribed throughout the dark ocean, irrespective of conditions. Thaumarchaeal urease ( ureC) genes are also present throughout, implying a widespread capacity for mixotrophy; however, unlike amoA, their expression is not detectable. Together, the results support a strong linkage between organic matter flux and nitrification rates, identify density as an important control over AOA distributions, and suggest that WCA and WCB distributions are influenced by the availability of their preferred substrates in the dark ocean. [ABSTRACT FROM AUTHOR]

The occurrence of nitrification in the oceanic water column has implications extending from local effects on the structure and activity of phytoplankton communities to broader impacts on the speciation of nitrogenous nutrients and production of nitrous oxide. The ammonia-oxidizing archaea, responsible for carrying out the majority of nitrification in the sea, are present in the marine water column as two taxonomically distinct groups. Water column group A (WCA) organisms are detected at all depths, whereas Water column group B (WCB) are present primarily below the photic zone. An open question in marine biogeochemistry is whether the taxonomic definition of WCA and WCB organisms and their observed distributions correspond to distinct ecological and biogeochemical niches. We used the natural gradients in physicochemical and biological properties that upwelling establishes in surface waters to study their roles in nitrification, and how their activity-ascertained from quantification of ecotype-specific ammonia monooxygenase (amoA) genes and transcripts-varies in response to environmental fluctuations. Our results indicate a role for both ecotypes in nitrification in Monterey Bay surface waters. However, their respective contributions vary, due to their different sensitivities to surface water conditions. WCA organisms exhibited a remarkably consistent level of activity and their contribution to nitrification appears to be related to community size. WCB activity was less consistent and primarily constrained to colder, high nutrient and low chlorophyll waters. Overall, the results of our characterization yielded a strong, potentially predictive, relationship between archaeal amoA gene abundance and the rate of nitrification. [ABSTRACT FROM AUTHOR]

Abstract: This work quantifies the role of tropical instability waves (TIWs) in modulating nutrient and chlorophyll distributions in the equatorial Pacific through an analysis of satellite data and a case study of in situ observations. A TIW index is constructed to differentiate periods of strong and weak TIW activity. TIW impacts are first examined in monthly averaged satellite SST and chlorophyll data for three distinct regions north of the equator where TIWs are most active. The chlorophyll data are high-pass filtered to preserve the seasonal cycle and remove long-term trends. Although SST follows a predictable relationship with the TIW index, chlorophyll concentrations do not. Periods of high TIW activity are characterized by cooler SSTs but consistently low chlorophyll. A case study of individual TIW vortices demonstrates that their impact on nutrients and chlorophyll is a function of intensity. Strong TIWs drive reductions in nutrients and chlorophyll due to the subduction of nutrient-replete water north of the equator and the advection of nutrient-poor water toward the equator from adjacent to the upwelling zone. Weak TIWs do not drive these advective processes to the same degree, so retain elevated nutrients that fuel chlorophyll increases. The most positive effect on nutrients and chlorophyll by TIWs was observed during boreal winter, likely owing to thermocline topography. A shallower thermocline in combination with weak TIWs results in elevated nutrients and chlorophyll north of the equator. Given the variability associated with TIW intensity and season, generalizing TIW effects has proven difficult, but targeted Lagrangian studies will better characterize these dynamic features and their impact on elemental fluxes. [Copyright &y& Elsevier]

Nesting populations of leatherback turtles (Dermochelys coriacea) in the Atlantic and western Indian Oceans are increasing or stable while those in the Pacific are declining. It has been suggested that leatherbacks in the eastern Pacific may be resource limited due to environmental variability derived from the El Niño Southern Oscillation (ENSO), but this has yet to be tested. Here we explored bottom-up forcing and the responding reproductive output of nesting leatherbacks worldwide. We achieved this through an extensive review of leatherback nesting and migration data and by analyzing the spatial, temporal, and quantitative nature of resources as indicated by net primary production at post-nesting female migration and foraging areas. Leatherbacks in the eastern Pacific were the smallest in body size and had the lowest reproductive output due to less productive and inconsistent resources within their migration and foraging areas. This derived from natural interannual and multidecadal climate variability together with an influence of anthropogenic climate warming that is possibly affecting these natural cycles. The reproductive output of leatherbacks in the Atlantic and western Indian Oceans was nearly twice that of turtles in the eastern Pacific. The inconsistent nature of the Pacific Ocean may also render western Pacific leatherbacks susceptible to a more variable reproductive output; however, it appears that egg harvesting on nesting beaches is their major threat. We suggest that the eastern Pacific leatherback population is more sensitive to anthropogenic mortality due to recruitment rates that are lower and more variable, thus accounting for much of the population differences compared to Atlantic and western Indian turtles. [ABSTRACT FROM AUTHOR]

Abstract: We report on a direct and autonomous measure of new production based on time series observations with ISUS nitrate sensors deployed for several years on oceanographic moorings offshore of Monterey Bay, California. The amplitude of diel cycles of surface nitrate is correlated with rates of primary production measured by 14C uptake. The drawdown of nitrate averaged over a year is about 70% of the fixed nitrogen needed for biomass production. Phytoplankton biomass predicted from the diel nitrate uptake and a fixed rate constant for nitrate loss (grazing and export) matched observations over the annual cycle. New production rates determined with the moored sensors are highly correlated with nitrate concentration and the intensity of upwelling. The implication is that arrays of moorings with chemical sensors can now be used to estimate new production of biomass and ecosystem processes over multiple temporal and spatial scales. [Copyright &y& Elsevier]

The availability of iron is known to exert a controlling influence on biological productivity in surface waters over large areas of the ocean and may have been an important factor in the variation of the concentration of atmospheric carbon dioxide over glacial cycles. The effect of iron in the Southern Ocean is particularly important because of its large area and abundant nitrate, yet iron-enhanced growth of phytoplankton may be differentially expressed between waters with high silicic acid in the south and low silicic acid in the north, where diatom growth may be limited by both silicic acid and iron. Two mesoscale experiments, designed to investigate the effects of iron enrichment in regions with high and low concentrations of silicic acid, were performed in the Southern Ocean. These experiments demonstrate iron's pivotal role in controlling carbon uptake and regulating atmospheric partial pressure of carbon dioxide. [ABSTRACT FROM AUTHOR]

The utility of alkenone abundance and U37K′ ratios as proxies for haptophyte productivity and temperature variations, respectively, was examined in an upwelling setting by comparison of alkenones with other environmental variables including carbon concentrations, plankton populations, productivity, and temperature. Suspended particulate organic material (SPOM) was collected from surface waters (1–5 m) in Monterey Bay, California during the 1992 El Nin˜o. Haptophyte algae comprise a small but significant fraction of the plankton assemblage (0.5–30%). In this upwelling environment either the haptophytes contain low cellular abundances of alkenones (0.4–5% Corg) and/or alkenone producers are weakly represented among their populations. The U37K′-temperature relationship for SPOM exhibits a better correlation (r2=0.870; n=8) during periods of active upwelling and in the winter than throughout the entire annual cycle (r2=0.308; n=18). The alkenone-based temperatures also suggest, as observed elsewhere, that these compounds originated in colder waters at depth and were subsequently transferred to surface waters. [Copyright &y& Elsevier]

Examines the turbid underflows from a coastal river into the deep sea in Monterey Bay, California. Inferences from the structure of coastal sedimentary deposits; Observations of turbidity in deep water during high river flows; Causes of driving hyperpycnal flows of turbid freshwater into depth.

Species and habitats are the subjects of legislation that mandates reporting of information on ecosystem conditions. Improvements in sensors, sampling platforms, information systems, and collaborations among experts and information users now enables more effective and up-to-date information to meet regional and national needs. Specifically, advances in environmental DNA (eDNA)-based assessments of biodiversity, community science data, various underwater imaging devices, and environmental, behavioral, and physiology observations from animal telemetry provide new opportunities to address multiple requirements for reporting status and trends, including insights into life in the deep ocean. Passive and active acoustic sensors help monitor marine life, boat traffic, and noise pollution. Satellites provide repeated, frequent, and long-term records of many relevant variables from global to local scales and, when combined with numerical computer simulations, allow planning for future scenarios. Metadata standards facilitate the transfer of data from machine to machine, thus streamlining assessments and forecasting and providing knowledge directly to the public. The Marine Biodiversity Observation Network (MBON) facilitates this exchange of information on life in the sea. The collaborative efforts of the Central and Northern California Ocean Observing System (CeNCOOS) of the US Integrated Ocean Observing System and its partners provide an example of a regional MBON process for information delivery. This includes linking policy and management needs, prioritizing observing data from various platforms and methods, streamlining data handling practices, and delivering information for management such as for the Monterey Bay National Marine Sanctuary and the California Current Large Marine Ecosystem, with iterative process adaptation. [ABSTRACT FROM AUTHOR]

Our synthesis combines inferences from a long-term fisheries monitoring survey and principles of ecosystem oceanography to inform and benefit biodiversity monitoring and modeling studies within the California Current Large Marine Ecosystem. We review the history, research, and application of the Rockfish Recruitment and Ecosystem Assessment Survey, highlighting how one survey of life can illuminate understanding of pelagic biodiversity patterns and ecosystem function (from micronekton to upper trophic level predators to ecosystem services) that may be easily extended to other surveys to strengthen observation networks. Biodiversity is often used as the standard for understanding ecosystem resilience to climate or anthropogenic disturbances. This concept is central to our review, and we examine it in relation to complex impacts resulting from a recent climate event (a marine heatwave) on biodiversity, ecosystem function, and socioeconomic services. We present a system of interconnected modules that summarize and illustrate patterns of pelagic biodiversity using a phylogenetic approach, known modulations and environmental drivers of variability (i.e., source waters, habitat compression, and ecosystem shifts), remote sensing and modeling tools for monitoring biodiversity (i.e., seascapes and krill hotspot models), and the status of top predator diversity. We use these modules to summarize connections between biodiversity and ecosystem services provided. Following each module, a brief discussion of questions raised and recommendations for future studies and partnerships is provided to improve future integrative biodiversity monitoring. Additionally, we invested in promoting data accessibility and outreach, resulting in several data visualization and ecosystem context tools for biodiversity monitoring and fisheries management. We advocate that a diverse integrated ecosystem approach should result in fewer ecological surprises by putting past events and surprises into context, and thus better anticipating those yet to arrive. Building partnerships among researchers and coastal communities will result in increased capacity of analytical tools and perspectives to ensure sustainable use of fishery resources, while strengthening the resilience of fishing communities. [ABSTRACT FROM AUTHOR]

Recent work using compound-specific stable isotopes of amino acids (CSI-AA) in proteinaceous deep-sea corals opens a new realm of high-fidelity reconstruction for biogeochemical and ecological changes in the ocean. However, underlying these CSI-AA paleoceanographic applications are a series of fundamental assumptions, which hold first that baseline-proxy AA isotope values fixed at the base of food webs represent integrated δ13C and δ15N values of primary production, and second they are unaltered during subsequent export and incorporation from particles into corals. We explored long-term δ13C and δ15N CSI-AA data on a sediment trap time series together with contemporaneous, geographically close deep-sea bamboo corals (Isidella sp.) in the California margin, directly testing these assumptions for the first time. Our data show that isotope values of essential (δ13C EAA) and source AAs (δ15N Phe) in sinking particles quantitatively track bulk δ13C and δ15N values of export production. These CSI-AA baseline proxies varied independently of carbon flux, trophic position (TP CSI-AA) and microbial alteration, suggesting that they were well preserved in the sinking particles consumed by corals. Paired comparisons between sinking particles and corals revealed minor elevations of δ13C EAA (by ∼2‰) and δ15N Phe (by ∼1‰) in available coral specimens. We hypothesize that the difference in δ13C EAA is due to the geographic offset in δ13C values of primary production expected between the (more offshore) sediment trap site and (more onshore) coral specimens, whereas the δ15N Phe offset is likely related to expected minor trophic fractionation. Using empirical models derived from the sediment trap time series, we demonstrate for the first time that CSI-AA in proteinaceous deep-sea corals can reconstruct known bulk δ15N values of export production, source nitrogen δ15N values, and exported TP CSI-AA values with very good fidelity. Together, these findings represent a major advance in our understanding of AA isotope behavior in modern and paleoarchives, and can be used to underpin the rapidly evolving use of CSI-AA-based tools in multiple paleoceanographic studies and archives. [ABSTRACT FROM AUTHOR]

The California Current System is thought to be particularly vulnerable to ocean acidification, yet pH remains chronically undersampled along this coast, limiting our ability to assess the impacts of ocean acidification. To address this observational gap, we integrated the Deep-Sea-DuraFET, a solid-state pH sensor, onto a Spray underwater glider. Over the course of a year starting in April 2019, we conducted seven missions in central California that spanned 161 glider days and >1600 dives to a maximum depth of 1000 m. The sensor accuracy was estimated to be ± 0.01 based on comparisons to discrete samples taken alongside the glider (n = 105), and the precision was ± 0.0016. CO2 partial pressure, dissolved inorganic carbon, and aragonite saturation state could be estimated from the pH data with uncertainty better than ± 2.5%, ± 8 μmol kg-1, and ± 2%, respectively. The sensor was stable to ± 0.01 for the first 9 months but exhibited a drift of 0.015 during the last mission. The drift was correctable using a piecewise linear regression based on a reference pH field at 450 m estimated from published global empirical algorithms. These algorithms require accurate O2 as inputs; thus, protocols for a simple predeployment air calibration that achieved accuracy of better than 1% were implemented. The glider observations revealed upwelling of undersaturated waters with respect to aragonite to within 5 m below the surface near Monterey Bay. These observations highlight the importance of persistent observations through autonomous platforms in highly dynamic coastal environments. [ABSTRACT FROM AUTHOR]

Nitrification plays a key role in marine ecosystems where Thaumarchaeota are thought to be responsible for most of the ammonia oxidation in the water column. Over a 2‐yr, near‐monthly time series at two sites in Monterey Bay we observed repeatable seasonal and depth‐based patterns of Thaumarchaeota ecotype abundance that highlighted a clear delineation between populations in shallow euphotic (< 50 m) vs. deeper mesopelagic (60–500 m) depths. Euphotic depths show greater seasonality and influence from light, while mesopelagic waters have trends based on water mass and other covarying features with depth. Three major ecotypes were recovered: a Nitrosopumilus‐like (NP) group, a Nitrosopelagicus‐like ecotype containing "shallow" water column A (WCA) members, and an ecotype affiliated with the "deep" water column B (WCB) Thaumarchaeota. These ecotypes show a strong depth distribution, with WCB dominant at ≥ 200 m depth and WCA most abundant in surface (5–100 m) waters. The NP ecotype was found throughout the water column with the highest abundance in summer, and was the only ecotype showing a correlation with measured nitrification rates. We also found three abundant taxa related to Nitrospina—the major nitrite‐oxidizing bacteria in the ocean; these showed clear connections to each of the three Thaumarchaeota ecotypes, suggesting a specific relationship between both steps of nitrification. Our results support the importance of ecotype‐based analysis of Thaumarchaeota and show that their abundance and distribution are controlled based on their water column position, with a distinct shift at 50 m between euphotic and mesopelagic depths. [ABSTRACT FROM AUTHOR]

Within the southern California Current ecosystem there are two well-documented breaks in marine community structure at Point Conception and Punta Eugenia. We explored the presence of similar breaks in a diverse zooplankton community through metabarcoding of mixed net tow tissue samples collected during an expedition from Monterey to Baja California in February of 2012. We recovered a high diversity of species as well as patterns of species presence that align with their previously documented ranges in this region. We found a clear break at Punta Eugenia in overall zooplankton community structure, while Point Conception was weakly linked to changes in community structure. We analyzed this dataset through two parallel bioinformatic pipelines to examine the robustness of these results. Our overall conclusions were consistent across both pipelines, however there were differences in species detection. This study illustrates the utility of metabarcoding analysis on mixed tissue samples for recovering known patterns of diversity, as well as allowing elucidation of broad patterns of community differentiation across many groups of organisms. [ABSTRACT FROM AUTHOR]

Summary: Ammonia‐oxidizing archaea (AOA) of the phylum Thaumarchaeota are key players in nutrient cycling, yet large gaps remain in our understanding of their ecology and metabolism. Despite multiple lines of evidence pointing to a central role for copper‐containing nitrite reductase (NirK) in AOA metabolism, the thaumarchaeal nirK gene is rarely studied in the environment. In this study, we examine the diversity of nirK in the marine pelagic environment, in light of previously described ecological patterns of pelagic thaumarchaeal populations. Phylogenetic analyses show that nirK better resolves diversification patterns of marine Thaumarchaeota, compared to the conventionally used marker gene amoA. Specifically, we demonstrate that the three major phylogenetic clusters of marine nirK correspond to the three 'ecotype' populations of pelagic Thaumarchaeota. In this context, we further examine the relative distributions of the three variant groups in metagenomes and metatranscriptomes representing two depth profiles in coastal Monterey Bay. Our results reveal that nirK effectively tracks the dynamics of thaumarchaeal ecotype populations, particularly finer‐scale diversification patterns within major lineages. We also find evidence for multiple copies of nirK per genome in a fraction of thaumarchaeal cells in the water column, which must be taken into account when using it as a molecular marker. [ABSTRACT FROM AUTHOR]

This study examines the occurrence of humpback whale (Megaptera novaeangliae) song in the northeast Pacific from three years of continuous recordings off central California (36.713°N, 122.186°W). Song is prevalent in this feeding and migratory habitat, spanning nine months of the year (September–May), peaking in winter (November–January), and reaching a maximum of 86% temporal coverage (during November 2017). From the rise of song in fall through the end of peak occurrence in winter, song length increases significantly from month to month. The seasonal peak in song coincides with the seasonal trough in day length and sighting-based evidence of whales leaving Monterey Bay, consistent with seasonal migration. During the seasonal song peak, diel variation shows maximum occurrence at night (69% of the time), decreasing during dawn and dusk (52%), and further decreasing with increasing solar elevation during the day, reaching a minimum near solar noon (30%). Song occurrence increased 44% and 55% between successive years. Sighting data within the acoustic detection range of the hydrophone indicate that variation in local population density was an unlikely cause of this large interannual variation. Hydrographic data and modeling of acoustic transmission indicate that changes in neither habitat occupancy nor acoustic transmission were probable causes. Conversely, the positive interannual trend in song paralleled major ecosystem variations, including similarly large positive trends in wind-driven upwelling, primary productivity, and krill abundance. Further, the lowest song occurrence during the first year coincided with anomalously warm ocean temperatures and an extremely toxic harmful algal bloom that affected whales and other marine mammals in the region. These major ecosystem variations may have influenced the health and behavior of humpback whales during the study period. [ABSTRACT FROM AUTHOR]

Managing natural resources under large-scale environmental fluctuations like the El Niño Southern Oscillation (ENSO) is likely to become increasingly important under climate change. Forecasts of environmental conditions are improving, but the best response to an unfavorable forecast remains unclear; many practitioners advocate reducing harvest as a more precautionary approach, while prior economic theory favors increasing harvest. Using logistic and age-structured fisheries models, we show that informational constraints — uncertain stock estimates and restrictions on harvest policies — play a central role in choosing how to respond to a forecasted shock. With perfect knowledge and no policy constraints, risk-neutral managers should increase harvest when a negative shock is forecast. However, informational constraints may drive the optimal response to a forecast of a negative shock toward or away from precaution. Precautionary forecast responses arise when informational constraints make the harvest policy insufficiently sensitive to the true resource status. In contrast, uncertainty about the stock size can lead to more aggressive forecast responses when stock dynamics are nonlinear and not all fish are susceptible to fishing. [ABSTRACT FROM AUTHOR]

Greatly enhanced atmospheric carbon dioxide (CO2) levels relative to well-mixed marine air are observed during periods of offshore winds at coastal sensor platforms in Monterey Bay, California, USA. The highest concentrations originate from urban and agricultural areas, are driven by diurnal winds, and peak in the early morning. These enhanced atmospheric levels can be detected across a ~100km wide nearshore area and represent a significant addition to total oceanic CO2 uptake. A global estimate puts the added sea-air flux of CO2 from these greatly enhanced atmospheric CO2 levels at 25 million tonnes, roughly 1% of the ocean’s annual CO2 uptake. The increased uptake over the 100 km coastal swath is of order 20%, indicating a potentially large impact on ocean acidification in productive coastal waters. [ABSTRACT FROM AUTHOR]

• We analyze potential drivers of domoic acid HABs in California waters from 20 years of data. • Silicic acid deficit correlates with increased domoic acid HABs ocurrence in California. • Upwelling drives Chl-a concentrations and more intense domoic acid HABs. • Climate modes affect subregional domoic acid HABs frequencies differently. • Riverine and wastewater discharges are positively associated with domoic acid HABs in the south. Pseudo-nitzschia species with the ability to produce the neurotoxin domoic acid (DA) are the main cause of harmful algal blooms (HABs) along the U.S. West Coast, with major impacts on ecosystems, fisheries, and human health. While most Pseudo-nitzschia (PN) HAB studies to date have focused on their characteristics at specific sites, few cross-regional comparisons exist, and mechanistic understanding of large-scale HAB drivers remains incomplete. To close these gaps, we compiled a nearly 20-year time series of in situ particulate DA and environmental observations to characterize similarities and differences in PN HAB drivers along the California coast. We focus on three DA hotspots with the greatest data density: Monterey Bay, the Santa Barbara Channel, and the San Pedro Channel. Coastwise, DA outbreaks are strongly correlated with upwelling, chlorophyll-a, and silicic acid limitation relative to other nutrients. Clear differences also exist across the three regions, with contrasting responses to climate regimes across a north to south gradient. In Monterey Bay, PN HAB frequency and intensity increase under relatively nutrient-poor conditions during anomalously low upwelling intensities. In contrast, in the Santa Barbara and San Pedro Channels, PN HABs are favored under cold, nitrogen-rich conditions during more intense upwelling. These emerging patterns provide insights on ecological drivers of PN HABs that are consistent across regions and support the development of predictive capabilities for DA outbreaks along the California coast and beyond. [Display omitted] [ABSTRACT FROM AUTHOR]

Chemical sensor development has been a focus for the Monterey Bay Aquarium Research Institute (MBARI) from its inception. Progress in chemical analyzers benefited from technological advances in many fields. MBARI's development of a low power, reagent-free, in situ ultraviolet spectrophotometer (ISUS) for measuring dissolved nitrate has been transformative. These ultraviolet optical nitrate sensors have been deployed on remotely operated vehicles, autonomous underwater vehicles, benthic flux chambers, profiling floats, and moorings. This paper focuses on a 15+ year time series of nitrate observations on MBARI's M1 mooring in Monterey Bay, California. The resulting data set captures seasonal and interannual variability from El Niño and La Niña, and water mass anomalies on the eastern boundary of the Pacific Ocean. The high temporal resolution (hourly) nitrate measurements additionally quantify diel cycles of nitrate uptake as a proxy for new production. The calculated f-ratio varies seasonally with relatively higher values during the lower productivity winter season. The physical supply and uptake of nitrate are dominated by upwelling in this coastal environment. An expanding number of ultraviolet optical nitrate sensor deployments on moorings and autonomous platforms such as profiling floats will provide everbroadening coverage of the world ocean, resulting in enhanced spatial and temporal resolution of nitrate measurements and, ultimately, improved insight into the dynamics of nitrogen cycling and phytoplankton ecology throughout a changing global ocean. [ABSTRACT FROM AUTHOR]