The Northeast US Continental Shelf (NES) is a highly productive marine ecosystem that has experienced wide swings in phytoplankton chlorophyll concentration (CHL). To better understand this variability, we examined changes in CHL over the period 1998-2022, while also considering three indicators of the potential supply of nutrient source waters including cross-shelf advection via deep channels, transport from beyond the shelf edge via Gulf Stream warm core rings (WCR), and input from river and estuarine discharge. Traditionally, deep channel advection of water across the NES was assumed to be derived from Labrador Slope Water (LSW) and Warm Slope Water (WSW). These designations do not fully capture the range of water types contributing to cross-shelf advection. The contribution of LSW and WSW was reciprocal over time, with the presence of WSW at an increased level in recent years. There has been an increase in the number of WCRs off the NES represented by indices of ring occupancy. Precipitation increased over the study period as well, generally over the NES region and in particular in the Mid-Atlantic Bight drainage. We see evidence of the effect of increased precipitation on the NES proper through a change in the area of the ocean surface having 555 nm reflectance with sr-1 > 0.004. Using a canonical analysis, CHL correlated positively with the proportion of LSW and negatively with WSW. These correlations suggest there are aspects of the nutrient content associated with these water masses that are key to phytoplankton growth. WCR frequency negatively correlated with CHL, which was expected since the nutrient loadings of WCRs tends to be low. Finally, CHL negatively correlated with precipitation rate, which suggests terrestrial origin nutrient inputs to the NES are minor. We suggest that in order to understand future CHL dynamics in the NES, careful consideration of advective sources of nutrients in the Northwest Atlantic is necessary.

Enhancement of shellfish populations has long been discussed as a potential nutrient reduction tool, and eastern oyster aquaculture was recently approved as a nutrient reduction best management practice (BMP) in Chesapeake Bay, USA. This study addressed BMP-identified data gaps involving variation in nutrient concentration related to ploidy, effects of reproductive development, and a paucity of phosphorus concentration data. Diploid and triploid oysters were collected from farms in Maryland and Virginia across the typical local reproductive cycle. The nutrient concentration of tissue and shell was consistent with the currently implemented BMP. Minor variation observed in nitrogen and phosphorus concentration was within the previously reported range, for farm location, ploidy, and reproductive cycle timing. Ploidy-based differences in tissue dry weight were not observed at either farm, which contrasts with current nutrient reduction estimates. These results suggest separate crediting values for diploids and triploids may need further investigation and potential re-evaluation.

Shellfish aquaculture can provide important ecosystem services to coastal communities, yet these benefits are not typically considered within the aquaculture permit review process. Resource managers have expressed interest in easy-to-use tools, based on robust science, that produce location and operation-appropriate values for beneficial services. These values need to be produced in a format that aligns with existing regulatory processes to facilitate seamless integration with permit review. The removal of excess nitrogen from coastal waters by shellfish farms is well documented in the literature and has been incorporated into nutrient management in the USA. Shellfish assimilate nitrogen into their tissue and shell as they grow, and this nitrogen is removed from the environment upon harvest. We have assembled a dataset of nitrogen concentration and morphometric measurements from farmed eastern oysters across the US Northeast, and adapted methodology used by existing nutrient management programs to quantify harvest-associated removal of nitrogen. Variability in oyster tissue and shell nutrient concentration was low within the dataset, and an assessment of farm location, ploidy, and three common cultivation practices (floating gear, bottom gear, no gear) suggested that a simple regression-based calculation could be applied across all farms within the region. We designed the new, publicly available online Aquaculture Nutrient Removal Calculator tool https://connect.fisheries.noaa.gov/ANRC/ based on this analysis, which uses inputs related to oyster size and harvest number to predict harvest-based nitrogen removal from an eastern oyster farm located within the geographic range of North Carolina to Maine, USA. The tool also produces a report that has been designed to integrate with the US Army Corps of Engineers public interest review process, and similar state-level permitting processes, and provides a succinct summary of the ecological services associated with nutrient removal in eutrophic locations, project-specific values, and citations supporting the calculation of those values.

Climate change can alter marine ecosystems through changes in ocean temperature, acidification, circulation, and productivity. Over the last decade, the United States northeast continental shelf (U.S. NES) has warmed faster than any other marine ecosystem in the country and is among the fastest warming regions of the global ocean. Many living marine resources in the U.S. NES ranging from recreational and commercial fish stocks to protected species have shifted their distribution in response to ocean warming. The National Oceanic and Atmospheric Administration’s National Marine Fisheries Service (NOAA Fisheries) is responsible for the assessment, protection, and sustainable use of the nation’s living marine resources. In the U.S. NES, NOAA Fisheries has made substantial progress on climate research related to fish, fisheries, and protected species. However, more research is needed to help inform tactical management decisions with the goal of climate-ready living marine resource management. This is a major challenge because the observed physical and biological changes are unprecedented, and the majority of marine species assessments and management decisions do not utilize environmental data. Here we review the research accomplishments and key needs for NOAA Fisheries in the U.S. NES in the context of climate change and living marine resource management. Key research needs and products are: 1) Infrastructure with continued and enhanced ocean surveys that includes cooperative research with the fishing industry and other NOAA line offices and partners; 2) Tracking and projecting change, and understanding mechanisms including state of the ecosystem reporting, improved regional ocean and ecosystem hindcasts, forecasts, and projections, and continued process-based laboratory and field studies, 3) climate-informed management, including stock assessments that account for climate where possible, translation of changing species distributions into spatial management, climate vulnerability assessment and scenario planning, ecosystem-based management, management strategy evaluations, and increased multidisciplinary science that includes economic and social indicators.

The development of wind energy on the US Northeast Continental Shelf (NES) may preclude resource-monitoring programmes from continuing in their original study designs. We considered the spatial requirements of energy developers and the spatial autocorrelation of resident species as a means to inform survey mitigation. The spatial requirements of the NES wind industry were considered in respect to the delineation of settled lease areas. We suggest access metrics ranging from 8 to 21 km representing the interquartile range of chord distances across the settled lease areas. Using survey data and concentrating on commercial species with stock assessment requirements, we computed indices of spatial autocorrelation. Tests of spatial autocorrelation using Moran's I and join counts statistics were significant (p < 0.05) for most species, suggesting a high level of spatial correlation in their distributions. To characterize a scalar extent of spatial correlation, variograms were fit to estimate the physical range of correlated catches. These data suggest most species were spatially correlated well beyond the distance metrics derived from the lease area shapes. Sampling by a range of gears has the potential of producing spatially accurate depictions of species distributions and abundance despite the restrictions wind lease areas may place on sampling designs.

Climate change is profoundly affecting the physical environment and biota of the Northeast U.S. Continental Shelf ecosystem. To understand adaptations to climate change, in particular warming temperatures, we used bottom trawl survey data to describe the size of individual fish and macroinvertebrates. Using species distribution models to estimate abundance and biomass, we determined body size in weight for all modeled species. We demonstrate a tendency for increased abundance and biomass and a concomitant decline in body size over time. An analysis of length frequency data supports this assertion. There was no trend in the combined anthropogenic removals from the ecosystem, i.e. catches, suggesting a limited role of fisheries in influencing these changes. The changes in the fish and macroinvertebrate communities are consistent with the hypothesis of a tropicalization of this ecosystem, where the ecosystem experiences a change in diversity, abundance, biomass, and the size of individuals consistent with lower latitudes. The changes in how productivity is expressed in the ecosystem factors into how human populations relate to it; in a practical sense, change in body size will likely influence the strategies and efficiencies of harvest procedures and the industries built to support them.

The northeast United States Atlantis model (NEUSv2) is an end-to-end ecosystem model that can simulate biogeochemical, ecological, fishery, management, and socio-economic processes within marine ecosystems. As a major update to the original model, NEUSv2 includes changes to the model's functional group definitions and forcing data. NEUSv2 is the first Atlantis model to use a satellite-ocean-color-derived phytoplankton size class model that was tuned specifically for the region to force marine primary production. Additionally, physical ocean variables (currents, temperature, and salinity) were updated using a high-resolution global ocean reanalysis. Despite its coarse resolution, NEUSv2 was capable of reproducing the broad spatial patterns seen in the physical and biological forcing sources, with the exception of some circulation features. NEUSv2 produced plausible zooplankton and planktivore biomass, a stable lower trophic food web, and recent trends in zooplankton biomass. NEUSv2 meets calibration criteria for the persistence and long-term stability of functional group biomass. Given the success of this new Atlantis forcing approach, we detail the observations and challenges regarding spatial scale-related processes, data assimilation, and biological calibration. We also discuss possible tradeoffs with model scope, calibration, and the availability of feedback mechanisms. This NEUSv2 hindcast is well suited for exploring ecosystem-level sensitivity to lower trophic processes and for testing alternative biogeochemical forcing. Further developments will improve model performance for higher trophic levels.

The size structure of phytoplankton communities influences important ecological and biogeochemical processes, including the transfer of energy through marine food webs. A variety of algorithms have been developed to estimate phytoplankton size classes (PSCs) from satellite ocean color data. However, many of these algorithms were developed for application to the global ocean, and their performance in more productive, optically complex coastal and continental shelf regions warrants evaluation. In this study, several existing PSC models were applied in the Northeast U.S. continental shelf (NES) region and compared with in situ PSC estimates derived from a local HPLC pigment data set. The effect of regional re-parameterization and incorporation of sea surface temperature (SST) into existing abundance-based model frameworks was investigated and model performance was assessed using an independent data set. Abundance-based model re-parameterization alone did not result in significant improvement in model performance compared with other models. However, the inclusion of SST led to a consistent reduction in model error for all size classes. Of two absorption-based algorithms tested, the best performing approach displayed similar performance metrics to the regional SST-dependent abundance-based model. The SST-dependent model and the absorption-based method were applied to monthly composites of the NES region for April and September 2019 and qualitatively compared. The results highlight the benefit of considering SST in abundance-based models and the applicability of absorption-based PSC methods in optically complex regions.

Species distribution models for marine organisms are increasingly used for a range of applications, including spatial planning, conservation, and fisheries management. These models have been constructed using a variety of mathematical forms and drawing on both physical and biological independent variables; however, what might be called first-generation models have mainly followed the form of linear models, or smoothing splines, informed by data collected in the context of fish surveys. The performance of different classes of variables were tested in a series of species occurrence models built with machine learning methods, specifically evaluating the potential contribution of lower trophic level data. Random forest models were fitted based on the classification of the absence/presence for fish and macroinvertebrates surveyed on the US Northeast Continental Shelf. The potential variables included physical, primary production, secondary production, and terrain variables. For accepted model fits, six variable importance measures were computed, which collectively showed that physical and secondary production variables make the greatest contribution across all models. In contrast, terrain variables made the least contribution to these models. Multivariable analyses that account for all performance measures reinforce the role of water depth and temperature in defining species presence and absence; however, chlorophyll concentration and some specific zooplankton taxa, such as Metridia lucens and Paracalanus parvus, also make important contributions with strong seasonal variations. Our results suggest that lower trophic level variables, if available, are valuable in the creation of species distribution models for marine organisms.

Temperature is an important factor in defining the habitats of marine resource species. While satellite sensors operationally measure ocean surface temperatures, we depend on in situ measurements to characterize benthic habitats. Ship-based measurements were interpolated to develop a time series of gridded spring and fall, surface and bottom temperature fields for the US Northeast Shelf. Surface and bottom temperatures have increased over the study period (1968-2018) at rates between 0.18-0.31 degrees C per decade and over a shorter time period (2004-2018) at rates between 0.26-1.49 degrees C per decade. A change point analysis suggests that a warming regime began in the surface waters in 2011 centered on Georges Bank and the Nantucket Shoals; in following years, most of the Northeast Shelf had experienced a shift in surface temperature. A similar analysis of bottom temperature suggests a warming regime began in 2008 in the eastern Gulf of Maine; in following years, change points in temperature occurred further to the west in the Gulf of Maine, finally reaching the Middle Atlantic Bight by 2010. The spatial pattern in bottom water warming is consistent with well-known oceanographic patterns that advect warming North Atlantic waters into the Gulf of Maine. The varying spatial and temporal progression of warming in the two layers suggests they were actuated by different sets of forcing factors. We then compared these trends and change points to responses of lower and higher trophic level organisms and identified a number of coincident shifts in distribution and biomass of key forage and fisheries species.

Sea surface temperature (SST), salinity, and chlorophyll concentration (CHL) have changed in the US Northeast Shelf ecosystem over recent decades. The changes in these parameters were distinctly marked by change points around the year 2012 resulting in a 0.83 degrees C increase in SST, a 0.3 PSU increase in salinity, and decrease in CHL in excess of 0.4 mg m(-3). Where temperature and salinity shifted in mean level around their respective change points, CHL declined in a more monotonic fashion. Modeled data suggest that the shift in CHL resulted in a greater contribution of pico- and nanophytoplankton and a decreased contribution of microphytoplankton to overall CHL. Complementary estimates of the contribution of different phytoplankton functional types suggest a diminished contribution of diatoms to the phytoplankton community. Hence, not only is there evidence of a decline in the overall primary production capacity of the ecosystem, but also evidence of a fundamental change in the size and quality of phytoplankton supporting food webs. Two ecosystem responses to the observed changes in SST, salinity, and CHL were analyzed. Both length and weight at age have declined for a number of species, and both measures of growth appear to be negatively associated with temperature and positively associated with CHL. Biomass of fish and macroinvertebrates has declined in recent years, with a decrease in pelagic species associated with a decrease in CHL, while the decline in demersal species was associated with an increase in temperature. Collectively, these ecosystem changes appear to be the result of the complex interactions of both thermal effects and changes at the base of the food web.

The Northeast US Continental Shelf Large Marine Ecosystem is experiencing warming at a rate exceeding that of many other large marine ecosystems and has undergone significant climate-related changes. We examined the effect of thermal events and shifting patterns of primary and secondary productivity on the distribution of fish and macroinvertebrate species during the period 1968-2016. Though subject to inter-annual change, the along-shelf centre of gravity of chlorophyll concentration lacked a trend. Similarly, zooplankton bio-volume and total abundance along-shelf distance were also found to be without trend. However, the trend in the centre of gravity of copepod taxa diverged from the trends in bio-volume and non-copepod zooplankton abundance, suggesting most of these taxa had shifted in distribution to the northeast. The centres of gravity of fish and macroinvertebrate species have trended significantly to the northeast, suggesting copepods may play a key role in the distribution of higher trophic levels. Analysis of thermal events suggest that abrupt change in temperature can actuate persistent change in the distribution of fish and macroinvertebrate species. In aggregate, these broad trophic level patterns imply that distributional changes affecting upper trophic levels were dominated by thermal mechanisms, whereas lower trophic productivity, although subject to the same thermal conditions, exhibited less of a response. We hypothesize this lack of distributional response at lower trophic levels is due to their higher rates of production and turnover, and hence reflect a capacity to better integrate seasonal thermal changes. Furthermore, distributional changes of upper trophic levels may also be significantly impacted by feeding interactions at specific life history stages, where temperature affects both predator and prey.

The North Atlantic right whale (NARW), Eubalaena glacialis, feeds on zooplankton, particularly copepods of the genus Calanus. We quantified interannual variation in anomalies of abundance and biomass of Calanus spp. and near-surface and near-bottom ocean temperature and salinity from 19 subregions spanning the Gulf of Maine–Georges Bank (GoM–GBK), Scotian Shelf (SS), Gulf of St. Lawrence (GSL) and Newfoundland and Labrador Shelves. We analyzed time series from 1977 to 2016 in GoM–GBK, 1982 to 2016 in southwest GSL and 1999 to 2016 in remaining areas. Calanus finmarchicus dominated abundance and biomass, except in the GSL where Calanus hyperboreus was abundant. The biomass of Calanus spp. declined in many subregions over years 1999–2016 and was negatively correlated with sea surface temperature in GoM–GBK and on the SS. We detected ``regime shifts” to lower biomass of Calanus spp. in the GoM–GBK in 2010 and on the SS in 2011. In the GoM–GBK, shifts to lower biomass of C. finmarchicus coincided with shifts to warmer ocean temperature and with published reports of changes in spatial distribution and reduced calving rate of NARW. We hypothesize that warming has negatively impacted population levels of Calanus spp. near their southern range limit, reducing the availability of prey to NARW.

Aim: This study examined phytoplankton blooms on a global scale, with the intention of describing patterns of bloom timing and size, the effect of bloom timing on the size of blooms, and time series trends in bloom characteristics. Location: Global. Methods: We used a change-point statistics algorithm to detect phytoplankton blooms in time series (1998-2015) of chlorophyll concentration data over a global grid. At each study location, the bloom statistics for the dominant bloom, based on the search time period that resulted in the most blooms detected, were used to describe the spatial distribution of bloom characteristics over the globe. Time series of bloom characteristics were also subjected to trend analysis to describe regional and global changes in bloom timing and size. Results: The characteristics of the dominant bloom were found to vary with latitude and in localized patterns associated with specific oceanographic features. Bloom timing had the most profound effect on bloom duration, with early blooms tending to last longer than later-starting blooms. Time series of bloom timing and duration were trended, suggesting that blooms have been starting earlier and lasting longer, respectively, on a global scale. Blooms have also increased in size at high latitudes and decreased in equatorial areas based on multiple size metrics. Main conclusions: Phytoplankton blooms have changed on both regional and global scales, which has ramifications for the function of food webs providing ecosystem services. A tendency for blooms to start earlier and last longer will have an impact on energy flow pathways in ecosystems, differentially favouring the productivity of different species groups. These changes may also affect the sequestration of carbon in ocean ecosystems. A shift to earlier bloom timing is consistent with the expected effect of warming ocean climate conditions observed in recent decades.

A multi-year study was conducted in the eutrophic Lafayette River, a sub-tributary of the lower Chesapeake Bay during which uptake of inorganic and organic nitrogen (N) and C compounds was measured during multiple seasons and years when different dinoflagellate species were dominant. Seasonal dinoflagellate blooms included a variety of mixotrophic dinoflagellates including Heterocapsa triquetra in the late winter, Prorocentrum minimum in the spring, Akashiwo sanguinea in the early summer, and Scrippsiella trochoidea and Cochlodinium polykrikoides in late summer and fall. Results showed that no single N source fueled algal growth, rather rates of N and C uptake varied on seasonal and diurnal timescales, and within blooms as they initiated and developed. Rates of photosynthetic C uptake were low yielding low assimilation numbers during much of the study period and the ability to assimilate dissolved organic carbon augmented photosynthetic C uptake during bloom and non-bloom periods. The ability to use dissolved organic C during the day and night may allow mixotrophic bloom organisms a competitive advantage over co-occurring phytoplankton that are restricted to photoautotrophic growth, obtaining N and C during the day and in well-lit surface waters.

Marine ecosystems worldwide experience rapid, persistent reorganization of biological and physical characteristics, known as 'regime shifts.' Here we provide a multivariate analysis of the ichthyoplankton assemblage in southern California (USA) from 1951 to 2017 in both spring and summer. We found unequivocal support for compositional regime shifts in 1965 and 1976 across both seasons, and additional strong evidence for shifts in 1983 and 1990 in the spring assemblage. The 1965 regime shift was associated with increases from low to moderate abundance of several offshore taxa, as well as peaks in the abundance of Sebastes spp. The impacts of the 1976 regime shift have been widely documented elsewhere across the North Pacific; here we demonstrate that the 1976 regime shift in the southern Californian ichthyoplankton assemblage coincided with increases in a large group of taxa characteristic of southern and offshore environments. By contrast, shifts in 1983 and 1989 in the spring assemblage appear to have been driven by variations in just a few highly abundant taxa. Finally, despite speculation that there was a climate regime shift from a 'warm' to a 'cool' period in the late 1990s, we found no support for a shift in the larval fish assemblage during these years. Our analyses provide context for understanding the countervailing effects on fish of natural environmental variability from annual through multi-decadal scales, with important implications for how marine assemblages will respond to secular, global changes in climate.

There is accumulating evidence for decadal-scale regime shifts at the base of the food web on the Northeast US Continental Shelf. However, less evidence exists for regime shifts in fish recruitment success, particularly for synchronized regimes across multiple species. Here, we analyzed stock assessment output and survey data to test for regimes in the recruitment success of 18 commercially important marine species over a 29 yr timespan. We then tested whether recruitment regimes coincide with regimes in the zooplankton community, and whether the abundance of large spawners could explain the patterns in recruitment. We found evidence for 3 decadal-scale recruitment regimes: low recruitment success in the 1980s, high success in the 1990s, and a return to low recruitment success in the 2000s. This general pattern was found in all datasets of recruitment. The abundance of large spawners did not appear to be a broad-scale driver of recruitment success; however, recruitment regimes coincided with regimes in copepod abundance and size structure.

The North Atlantic Ocean contains diverse patterns of seasonal phytoplankton blooms with distinct internal dynamics. We analyzed blooms using remotely-sensed chlorophyll a concentration data and change point statistics. The first bloom of the year began during spring at low latitudes and later in summer at higher latitudes. In regions where spring blooms occurred at high frequency (i. e., proportion of years that a bloom was detected), there was a negative correlation between bloom timing and duration, indicating that early blooms last longer. In much of the Northeast Atlantic, bloom development extended over multiple seasons resulting in peak chlorophyll concentrations in summer. Spring bloom start day was found to be positively correlated with a spring phenology index and showed both positive and negative correlations to sea surface temperature and the North Atlantic Oscillation in different regions. Based on the characteristics of spring and summer blooms, the North Atlantic can be classified into two regions: a seasonal bloom region, with a well-defined bloom limited to a single season; and a multi-seasonal bloom region, with blooms extending over multiple seasons. These regions differed in the correlation between bloom start and duration with only the seasonal bloom region showing a significant, negative correlation. We tested the hypothesis that the near-surface springtime distribution of copepods that undergo diapause (Calanus finmarchicus, C. helgolandicus, C. glacialis, and C. hyperboreus) may contribute to the contrast in bloom development between the two regions. Peak near-surface spring abundance of the late stages of these Calanoid copepods was generally associated with areas having a well-defined seasonal bloom, implying a link between bloom shape and their abundance. We suggest that either grazing is a factor in shaping the seasonal bloom or bloom shape determines whether a habitat is conducive to diapause, while recognizing that both factors can re-enforce each other.