The world's eastern boundary upwelling systems (EBUSs) contribute disproportionately to global ocean productivity and provide critical ecosystem services to human society. The impact of climate change on EBUSs and the ecosystems they support is thus a subject of considerable interest. Here, we review hypotheses of climate-driven change in the physics, biogeochemistry, and ecology of EBUSs; describe observed changes over recent decades; and present projected changes over the twenty-first century. Similarities in historical and projected change among EBUSs include a trend toward upwelling intensification in poleward regions, mitigated warming in near-coastal regions where upwelling intensifies, and enhanced water-column stratification and a shoaling mixed layer. However, there remains significant uncertainty in how EBUSs will evolve with climate change, particularly in how the sometimes competing changes in upwelling intensity, source-water chemistry, and stratification will affect productivity and ecosystem structure. We summarize the commonalities and differences in historical and projected change in EBUSs and conclude with an assessment of key remaining uncertainties and questions. Future studies will need to address these questions to better understand, project, and adapt to climate-driven changes in EBUSs. Expected final online publication date for the Annual Review of Marine Science, Volume 15 is January 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
Urbanization, accompanied by the creation of roads, pavements, and sidewalks creates an environment where there is limited infiltration capacity, leaving metropolitan areas especially vulnerable during intense rain events. Furthermore, within an urban setting, there is spatial variability, as certain areas, owing to location, topography, land feature conditions, population and physical attributes or precipitation patterns, are more prone to flood damages. To detect neighborhoods with increased flood risk, crowdsourced data, which is the consolidation of eyewitness accounts, affords particular value. With an intent to understand how factors affect the spatial variability of street flooding, the Random Forest regression machine learning algorithm is employed, where the 311 street flooding reports of New York City (NYC) serve as the response, while the explanatory variables include topographic and land feature, physical and population dynamics, locational, infrastructural, and climatic influences. This study also analyzes socio-economic variables as predictors, as to allow for better insight into potential biases within the NYC 311 crowdsourced platform. It is found that catch basin complaints have overwhelmingly the greatest predictor importance, at 41%, almost sixfold higher than that of the second highest ranked predictor, slope, at 6.7%. Thus, NYC has an apparent issue with debris blocking the basins, and this may be remediated by increased cleaning efforts or public awareness to maintain clear streets, particularly during forecasted rain events. Furthermore, more than a third of the top predictors are land feature and topographical conditions, with building characteristics dominating the category. Often excluded in urban flood models, building effects, with a combined total importance of 11.7%, have greater significance than commonly considered flooding factors, such as percent impervious cover or elevation. Another major finding is the significance of the ‘commuters who drive alone’ variable, which alerts to the prospect of more reports being filed by those more affected by street flooding, as opposed to reflecting the actual occurrence of flooding (more reports being filed by those who drive on flooded roads versus those who do not). Overall, the leading contribution of this study is the identification of the top flooding factors in NYC, along with the presentation of their specific impacts towards street flooding variability among zip codes.
Dungeness crab (Metacarcinus magister) are the most valuable fishery on the U.S. West Coast and both larval and adult Dungeness crabs are important components of regional food webs. Previous experiments have shown decreased survival and a slower development rate for Dungeness crab zoea reared in water with high CO2, indicating a susceptibility to ocean acidification. In this study we reared late-stage megalopae and juvenile Dungeness crabs in both ambient and high CO2 conditions for over 300 days. Counter to expectations, crabs reared in high CO2 had a higher survival rate than those reared in ambient conditions and crabs in high CO2 transitioned more quickly in one of the stages (J5 to J6). However, crabs reared in high CO2 were generally smaller and had a higher resting metabolic rate than crabs in ambient CO2. We hypothesized that two separate mechanisms were in effect, with one process driving survival and a second process driving size and respiration rate. We further hypothesized that increased mortality in ambient CO2 could be caused by a CO2-sensitive microbial pathogen, but that size and respiration differences were caused by the direct effects of CO2 on the crabs themselves. Overall, the zoea stages seem more sensitive to CO2 than the megalopae and juvenile stages.
Various types of floating macroalgae and other floating matters have been reported in the global oceans and inland waters, and their remote detection has relied primarily on passive optical sensors. These sensors provide multiple spectral bands and frequent revisits, yet they all suffer from clouds. Synthetic aperture radar (SAR) imagers are active sensors that overcome this obstacle, yet their capacity in detecting macroalgae and other floating matters is generally unknown. Here, through statistical analysis and comparison of the Sentinel-2/MultiSpectral Instrument (MSI) and Sentinel-1/SAR imagery, we attempt to fill this knowledge gap. The types of floating matters considered in this study include macroalgae (Ulva Prolifera in the Yellow Sea, Sargassum horneri in the East China Sea, and Sargassum fluitans/natans in the Caribbean Sea), cyanobacteria (Microcystis, Nodularia spumigena, and Trichodesmium), dinoflagellates (green and red Noctiluca), organic matters (sea snots and brine shrimp cysts), and marine debris (driftwood). Of these, the only floating matter that can be definitively detected in Sentinel-1/SAR imagery is U. prolifera, followed by the occasional detection of S. fluitans/natans and driftwood. In all detection cases, the macroalgae features always appear in Sentinel-1/SAR imagery with positive contrast from the surrounding waters. Because of the all-weather measurements, SAR observations can therefore complement those from the optical sensors in monitoring and tracking U. prolifera and S. fluitans/natans in their respective regions.
The Ecosystem Approach to Fisheries Management (EAFM) strives to balance multiple objectives of ecological wellbeing, social and economic wellbeing, and good governance. The Provincial Government of West Papua with technical support from the USAID Sustainable Ecosystems Advanced Project (SEA) has developed a fisheries management plan (FMP) for the anchovy fishery in Raja Ampat, West Papua Province of Indonesia. EAFM is the appropriate approach to manage the fishery because EAFM multiple objectives reflect the challenges and needs to ensure the sustainability of the fishery resources and to contribute to local communities. The FMP includes management issues, operational objectives, appropriate management measures, and action plans defined through a participatory process. The issues include overfishing as shown by declining anchovy catches, resource competition between local small-scale fishers and industrial fishers, limited livelihood opportunities, and an absence of a functional fishery governance institution. To address these challenges, the FMP has multiple operational objectives: to empower local livelihoods, strengthen institutional management mechanisms, and ensure anchovy resources sustainability. The integration of the socioeconomic aspect means there must be management decision trade-offs that weigh trade-offs of stock sustainability, local poverty, interests of the private sector, and addressing the horizontal conflict between locals and industrial fishers. Strengthening fisheries institutions is critical to ensure integration in resource investments and in detailing activities to implement the FMP because of the complementary roles, and lack of synergy of the multiple agencies. This holistic approach is expected to support the long-term use of the anchovy resources while partially alleviating local poverty.
Coral reefs worldwide are exposed to increased levels of thermal stress due to global warming. A coral reef at the remote island of Kapou (Lisianski) in Papahānaumokuākea experienced an unprecedented level of heat stress in 2014, which resulted in coral bleaching and subsequent mass mortality that resulted in nearly 100 % loss of live coral cover. Here, we describe successional changes in benthic communities occurring on the reef from 2014 to 2021 based on our surveys utilizing underwater photogrammetric techniques. Despite having > 85 % Montipora live coral cover before the bleaching event, the newly available substrata created by the loss of coral were quickly colonized by the green macroalga Halimeda, along with an ephemeral bloom of the green macroalga Boodlea in 2016. While Halimeda continued to increase in benthic cover, other algae (Neomeris, Asparagopsis and unidentified filamentous red and green algae) also started colonizing the reef between 2017 and 2021. Erosion of the reef substrata was evident in both in-situ and three-dimensional surveys in 2015 following the bleaching event and has continued to progress through time. The high abundance of Halimeda may indicate a slow process of coral recovery, but the overall benthic diversity increased in 2021 due to the presence of other algae and an increase in hard substrata and turf algal cover. New colonies of Montipora coral were also observed during annual surveys following the bleaching-induced mortality. Future monitoring efforts should continue to track coral and algal communities and survey herbivorous fish and reef binders that play important ecological roles in algal control, reef erosion and sediment binding. Such efforts should reveal interactions among these different ecological processes that enable reef succession following mass coral mortality.
DNA barcoding is critical to conservation and biodiversity research, yet public reference databases are incomplete. Existing barcode databases are biased toward cytochrome oxidase subunit I (COI) and frequently lack associated voucher specimens or geospatial metadata, which can hinder reliable species assignments. The emergence of metabarcoding approaches such as environmental DNA (eDNA) has necessitated multiple marker techniques combined with barcode reference databases backed by voucher specimens. Reference barcodes have traditionally been generated by Sanger sequencing, however sequencing multiple markers is costly for large numbers of specimens, requires multiple separate PCR reactions, and limits resulting sequences to targeted regions. High-throughput sequencing techniques such as genome skimming enable assembly of complete mitogenomes, which contain the most commonly used barcoding loci ( e.g., COI, 12S, 16S), as well as nuclear ribosomal repeat regions ( e.g., ITS1&2, 18S). We evaluated the feasibility of genome skimming to generate barcode references databases for marine fishes by assembling complete mitogenomes and nuclear ribosomal repeats. We tested genome skimming across a taxonomically diverse selection of 12 marine fish species from the collections of the National Museum of Natural History, Smithsonian Institution. We generated two sequencing libraries per species to test the impact of shearing method (enzymatic or mechanical), extraction method (kit-based or automated), and input DNA concentration. We produced complete mitogenomes for all non-chondrichthyans (11/12 species) and assembled nuclear ribosomal repeats (18S-ITS1-5.8S-ITS2-28S) for all taxa. The quality and completeness of mitogenome assemblies was not impacted by shearing method, extraction method or input DNA concentration. Our results reaffirm that genome skimming is an efficient and (at scale) cost-effective method to generate all mitochondrial and common nuclear DNA barcoding loci for multiple species simultaneously, which has great potential to scale for future projects and facilitate completing barcode reference databases for marine fishes.
Mobile weather radars at high frequencies (C, X, K and W-band) often collect data using staggered Pulse Repetition Time (PRT) or dual Pulse Repetition Frequency (PRF) modes to extend the effective Nyquist velocity and mitigate velocity aliasing while maintaining a useful maximum unambiguous range. These processing modes produce widely dispersed “processor” dealiasing errors in radial velocity estimates. The errors can also occur in clusters in high shear areas. Removing these errors prior to quantitative analysis requires tedious manual editing and often produces “holes” or regions of missing data in high signal-to-noise areas. Here, data from three mobile weather radars were used to show that the staggered PRT errors are related to a summation of the two Nyquist velocities associated with each of the PRTs. Using observations taken during a mature mesoscale convective system, a landfalling tropical cyclone, and a tornadic supercell storm, an algorithm to automatically identify and correct staggered PRT processor errors has been developed and tested. The algorithm creates a smooth profile of Doppler velocities using a Savitzky-Golay filter independently in radius and azimuth and then combined. Errors are easily identified by comparing the velocity at each range gate to its smoothed counterpart and corrected based on specific error characteristics. The method improves past dual PRF correction methods that were less successful at correcting “grouped” errors. Given the success of the technique across low, moderate, and high radial shear regimes, the new method should improve research radar analyses by affording the ability to retain as much data as possible rather than manually or objectively removing erroneous velocities.
Many animals have flexible morphological traits that allow them to succeed in differing circumstances with differing diets available to them. For brachyuran crabs, claw height and gut size are diet-specific and largely reflect foraging strategies, while abdomen width reflects relative levels of fecundity. However, the link between claw size and diet has largely been documented only for primarily carnivorous crabs, while the link between diet and fecundity is strong in herbivorous crabs. We sought to determine the nature of the intraspecific relationship between claw size, dietary habits, and fecundity for two primarily herbivorous crab species, Hemigrapsus sanguineus and Aratus pisonii . Specifically, we examined whether claw size and/or abdomen width can be used as reliable measures of individual diet strategy. To test these hypotheses, we collected crabs and measured the dimensions of their claws, abdomens, and guts. By comparing these dimensions for each individual, we found that strongly predictive relationships do not exist between these traits for the primarily herbivorous species in our study. Thus, identifying external morphological features that can be used to assess diets of primarily herbivorous crabs remains elusive.
Climate change is driving the redistribution of species throughout the oceans. However, the speed and magnitude of species responses, including shifts in their distribution, are variable and species specific. Quantifying the effect of environmental conditions on species distributions is crucial to informing management and conservation efforts. Blue marlin (Makaira nigricans) is a wide‐ranging top predator occurring circumglobally in tropical and subtropical waters and is heavily impacted by international longline fisheries. This study aimed to predict the global distribution of blue marlin and characterize the effects of climate variability thereon. Global. To conduct this study, pop‐up satellite archival tags (n = 144) deployed by recreational anglers through a global citizen science programme were used to generate a large tracking data set (14,928 days, 210,983 km from deployment to pop‐up locations) of blue marlin movement across three ocean basins. State‐space modelled tracking position estimates were used to create a species distribution model to represent global habitat suitability for blue marlin. Habitat suitability was determined by fitting a generalized additive mixed model (GAMM) as a function of environmental covariates which was used to predict monthly global blue marlin habitat from 2000 to 2016. Blue marlin habitat preference had the strongest association with sea surface temperature. Seasonal variation in blue marlin habitat occurs primarily at the latitudinal edges of the distribution range. Over the duration of the study, 96% of core habitat declined in suitability, with a concurrent poleward increase in suitability of marginal habitat. This study highlights the successful application of citizen‐based science to develop a long‐term global telemetry dataset. The present‐day loss of highly suitable habitat suggests ocean warming may be making equatorial waters less suitable even to highly mobile species. Blue marlin is likely to respond by following preferred habitat as it shifts poleward.
Increases in the magnitude, frequency, and duration of warm seawater temperatures are causing mass coral mortality events across the globe. Although, even during the most extensive bleaching events, some reefs escape exposure to severe stress, constituting potential refugia. Here, we identify present‐day climate refugia on the Great Barrier Reef (GBR) and project their persistence into the future. To do this, we apply semi‐dynamic downscaling to an ensemble of climate projections released for the IPCC's recent sixth Assessment Report. We find that GBR locations experiencing the least thermal stress over the past 20 years have done so because of their oceanographic circumstance, which implies that longer‐term persistence of climate refugia is feasible. Specifically, tidal and wind mixing of warm water away from the sea surface appears to provide relief from warming. However, on average this relative advantage only persists until global warming exceeds ~3°C. Increasing global average temperatures are driving mass coral mortality events around the world. Although, there are some reefs that escape the warm exposure, deemed as a potential refugia. We apply a unique method to improve coarse resolution climate projections over the Great Barrier Reef, isolating the locations that have experienced the least amount of thermal stress over the past 20 years. Wind and tidal mixing enabled the persistence of climate refugia in these locations. However, this advantage only persists until global average warming exceeds ~3°C.
Western U.S. (WUS) rainfall and snowpack vary greatly on interannual and decadal timescales. This combined with their importance to water resources makes future projections of these variables highly societally relevant. Previous studies have shown that precipitation events in the WUS are influenced by the timing, positioning, and duration of extreme integrated water vapor transport (IVT) events (e.g., atmospheric rivers) along the coast. We investigate end-of-21st-century projections of WUS precipitation and IVT in a collection of regional climate models (RCMs) from the North American Coordinated Regional Downscaling Experiment (NA-CORDEX). Several of the NA-CORDEX RCMs project a decrease in cool season precipitation at high elevation (e.g., across the Sierra Nevada) with a corresponding increase in the Great Basin of the U.S. We explore the larger-scale controls on this terrain-related precipitation change in a subset of the NA-CORDEX RCMs through an examination of IVT-events. Projected changes in frequency and duration of IVT-events depend on the event’s extremity: by the end of the century extreme IVT-events increase in frequency whereas moderate IVT-events decrease in frequency. Furthermore, in the future, total precipitation across the WUS generally increases during extreme IVT-events, whereas total precipitation from moderate IVT-events decreases across higher elevations. Thus, we argue that the mean cool season precipitation decreases at high elevations and increases in the Great Basin are largely determined by changes in moderate IVT-events which are projected to be less frequent and bring less high-elevation precipitation.
Thermal stress is expected to compromise the persistence of tropical corals throughout their biogeographic ranges, making many reefs inhospitable to corals by the end of the century. We integrated models of local predictions of thermal stress throughout the coming century, coral larval dispersal, and the persistence of a coral’s metapopulation(s) in the Caribbean to investigate broad trends in metapopulation fragmentation and decline. As coral reef patches become inhospitable throughout the next century, the metapopulation of Orbicella annularis is predicted to fragment, with sub-networks centered around highly connected patches and thermal refuges. Some of these are predicted to include the reefs of Colombia, Panama, Honduras, Guatemala, Belize, Southern and Northern Cuba, Haiti, and the Bahamas. Unknown coral population demographic parameters, such as lifetime egg production and stock-recruitment rates, limit the model’s predictions; however, a sensitivity analysis demonstrates that broadscale patterns of fragmentation and metapopulation collapse before the end of the century are consistent across a range of potential parameterizations. Despite dire predictions, the model highlights the potential value in protecting and restoring coral populations at strategic locations that are highly connected and/or influential to persistence. Coordinated conservation activities that support local resilience at low coral cover have the potential to stave off metapopulation collapse for decades, buying valuable time. Thermal refuges are linchpins of metapopulation persistence during moderate thermal stress, and targeted conservation or restoration that supports connectivity between these refuges by enhancing local population growth or sexual propagation may be critically important to species conservation on coral reefs.
To support and illustrate the revised view that “weather possesses chaos and order; it includes emerging organized systems (such as tornadoes) and recurrent seasons”, this short report presents the following major features: (1) Continuous vs. Sensitive Dependence on Initial Conditions (CDIC vs. SDIC); (2) single-types of attractors and monostability within the Lorenz 1963 model; (3) coexisting attractors and multistability within the Generalized Lorenz model; (4) Skiing vs. Kayaking: an analogy for monostability and multistability.
Eutrophication of the eastern plain lake (EPL) region has a significant impact on the sustainable economic development and is closely related to the shortage of water resources in China. Remote sensing provides an effective tool for quantifying the trophic state of inland waters by associating the trophic state index (TSI) with optically active water quality parameters. However, limited by the satellite coverage range and operation time, the long-term changes in the trophic state of the EPL region have not been thoroughly investigated. This study aims to fill this gap by generating a 35-year (1986–2020) TSI dataset of lakes in the eastern plain based on Landsat images. The TSI inversion algorithm based on the algal biomass index (ABI) was designed for Landsat series after consistency analysis. The seasonal variations of the TSI showed the highest TSI (62.0 ± 11.4) in summer and the lowest TSI (51.6 ± 8.0) in winter, with uncertainties caused by the limitation of ABI for extremely turbid waters and the number of Landsat seasonal images. The TSI of the EPLs increased over the past 35 years by about 8.2%. Four change patterns were defined for the long-term interannual TSI variations: increasing trend less than 50% (Mode 1) or more than 50% (Mode 2), breaking points that show a surge trend (Mode 3), and decreasing trend (Mode 4). The contribution of meteorological and anthropogenic factors was calculated using a generalized linear model, which revealed that the eutrophication of inland lakes in the EPL region is mainly affected by industrial wastewater discharge and urban expansion. The influence of these explanatory variables becomes more complex with an increase in lake area. Our research provides an estimation of the TSI for the first 35-year basin-scale in the EPL region and a comprehensive evaluation of the driving factors of inland water eutrophication. The results can be used for the effective management and restoration of lakes.
The Atlantic surfclam (Spisula solidissima) is a promising candidate for species diversification in the United States Northeast because it is native, grows rapidly, and is relatively recognizable to the public. However, gaps in the surfclam husbandry literature have left aquaculture practitioners without a complete understanding of how to best cultivate this species on commercial scales. In particular, relatively few studies have examined which culture conditions are necessary for rearing juvenile surfclams during the nursery phase. To fill this gap, controlled experiments were conducted to evaluate the efficacy of various gear types that are commonly used to rear other juvenile bivalve species. Specifically, growth and survival of early juvenile surfclams (0.4–2.7 mm) were compared when reared in different gear combinations, including downwellers, upwellers, and bell siphon systems. Similarly, growth and survival of late juvenile surfclams (1.1–18.0 mm) were compared when reared in upwellers and shallow raceways, with and without sand. Sediment accumulation, a proxy for culture cleanliness and system maintenance, was also monitored during the late nursery experiment. Results indicate that multiple rearing methods can effectively produce commercial-scale quantities of surfclams, but flow rate, food availability, and temperature are important factors that can limit gear efficiency. All early nursery gear systems performed similarly, while the late nursery upweller system performed significantly better than both types of shallow raceway systems. This study reinforces the feasibility of surfclams as a culture species that aligns well with the Northeast’s established shellfish farming framework.
Remote sensing technologies offer a consistent, spatiotemporal approach to assess water quality, which includes the detection, monitoring, and forecasting of cyanobacteria harmful algal blooms. In this study, a series of ex-situ mesoscale experiments were conducted to first develop and then monitor a Microcystis sp. bloom using a hyperspectral sensor mounted on an unmanned aircraft system (UAS) along with coincident ground sampling efforts including laboratory analyses and in-situ field probes. This approach allowed for the simultaneous evaluation of both bloom physiology (algal growth stages/life cycle) and data collection method on the performance of a suite of 41 spectrally-derived water quality algorithms across three water quality indicators (chlorophyll a, phycocyanin and turbidity) in a controlled environment. Results indicated a strong agreement between Lab and Field-based methods for all water quality indicators independent of growth phase, with regression R 2-values above 0.73 for mean absolute percentage error (MAPE) and 0.87 for algorithm R 2 values. Three of the 41 algorithms evaluated met predetermined performance criteria (MAPE and algorithm R 2 values); however, in general, algal growth phase had a substantial impact on algorithm performance, especially those with blue and violet wave bands. This study highlights the importance of co-validating sensor technologies with appropriate ground monitoring methods to gain foundational knowledge before deploying new technologies in large-scale field efforts.
Chaotic dynamics are thought to be rare in natural populations but this may be due to methodological and data limitations, rather than the inherent stability of ecosystems. Following extensive simulation testing, we applied multiple chaos detection methods to a global database of 172 population time series and found evidence for chaos in >30%. In contrast, fitting traditional one-dimensional models identified <10% as chaotic. Chaos was most prevalent among plankton and insects and least among birds and mammals. Lyapunov exponents declined with generation time and scaled as the −1/6 power of body mass among chaotic populations. These results demonstrate that chaos is not rare in natural populations, indicating that there may be intrinsic limits to ecological forecasting and cautioning against the use of steady-state approaches to conservation and management.
The extension of seasonal to interannual prediction of the physical climate system to include the marine ecosystem has a great potential to inform marine resource management strategies. Along the east coast of Africa, recent findings suggest that skillful Earth system model (ESM)-based chlorophyll predictions may enable anticipation of fisheries fluctuations. The mechanisms underlying skillful chlorophyll predictions, however, were not identified, eroding confidence in potential adaptive management steps. This study demonstrates that skillful chlorophyll predictions up to two years in advance arise from the successful simulation of westward-propagating off-equatorial Rossby waves in the Indian ocean. Upwelling associated with these waves supplies nutrients to the surface layer for the large coastal areas by generating north- and southward propagating waves at the east African coast. Further analysis shows that the off-equatorial Rossby wave is initially excited by wind stress forcing caused by El Niño/Southern Oscillation (ENSO)-Indian Ocean teleconnections.
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