Integrative Oceanography Division

It is often assumed that future coastal cliff retreat rates will accelerate as global sea level rises, but few studies have investigated how SLR (sea level rise) might change cliff-front wave dynamics. Using a new simple numerical model, this study simulates the number and type (breaking, broken, or unbroken) of cliff-front waves under future SLR scenarios. Previous research shows breaking waves deliver more energy to cliffs than broken waves, and unbroken waves generate minimal impact. Here, we investigated six cliff-platform profiles from three regions (USA, New Zealand, and UK) with varied tidal ranges and wave climates. Model inputs included 2013-2100 hindcast/forecast incident wave height and tidal water level, and three future SLR scenarios. Results show the number of both cliff-front breaking and broken waves generally increase for a high-elevation (relative to tide) cliff-platform junction. In contrast, breaking/broken wave occurrence decrease by 38-92% for a near-horizontal shore platform with a low-elevation cliff-platform junction under a high SRL scenario, leading to high (96-97%) unbroken wave occurrence. Overall, results suggest the response of cliff-front waves to future SLR is complex and depends on shore platform geometries and SLR scenarios, indicating that future cliff retreat rates may not homogeneously accelerate under SLR.

In April and May of 2020, a large phytoplankton bloom composed primarily of the dinoflagellate Lingulodinium polyedra reached historic levels in geographic expanse, duration, and density along the coast of southern California, United States, and Baja California Norte, Mexico. Here, we report the water quality parameters of dissolved oxygen and pH over the course of the red tide, as measured by multiple sensors deployed in various locations along San Diego County, and document the extent of mass organism mortality using field surveys and community science observations. We found that dissolved oxygen and pH corresponded with bloom dynamics, with extreme hypoxic and hyperoxic conditions occurring at multiple locations along the coast, most notably within select estuaries where dissolved oxygen reached 0 mg L−1 and hypoxia occurred for up to 254 consecutive hours, as well as along the inner shelf of the open coast where dissolved oxygen dropped as low as 0.05 mg L−1. Similarly, pH ranged widely (6.90–8.79) across the bloom over both space and time, largely corresponding with dissolved oxygen level. Extreme changes in dissolved oxygen and pH, in addition to changes to other water parameters that affect organismal health, ultimately led to documented mortalities of thousands of demersal and benthic fishes and invertebrates (primarily within estuarine and inner-shelf environments), and long-term surveys within one lagoon showed protracted changes to benthic infaunal density and species composition. In addition to field observations, we also quantified water quality parameters and organism mortalities from four local aquarium facilities, with varying levels of filtration and artificial oxygenation, and documented the morphological changes in the gills of captive-held Pacific sardine in response to the red tide. We show that multiple factors contributed to organismal stress, with hypoxia likely being the most widespread, but not the only, cause of mortality.

American Samoa is experiencing rapid relative sea level rise due to increases in global sea level and significant post-2009 earthquake land subsidence, endangering homes and critical infrastructure. Wave and water-level observations collected over a fringing reef at Fagaitua Bay, American Samoa, in 2017 reveal depth-limited shoreline sea-swell wave heights over the range of conditions sampled. Using field data to calibrate a one-dimensional, phase-resolving nonhydrostatic wave model (SWASH), we examine the influence of water level on wave heights over the reef for a range of current and future sea levels. Assuming a fixed reef bathymetry, model results predict rising sea levels will escalate nearshore extreme water levels that are dominated by an increase in nearshore sea-swell wave heights. Model results provide insight into how and at what reef depths rising sea levels reduce reef capacity to dissipate wave energy, compounding shoreline threats. This study aims to bring increased attention to the immediate threats to American Samoas way of life, and to demonstrate the utility of SWASH for extrapolating wave transformation to future sea level.

The high ecological and economic value of seagrass has been long recognized, with these foundational habitats providing myriad ecosystem services. Yet through cumulative anthropogenic impacts, seagrasses are exhibiting extensive declines globally. A litany of studies and active restoration trials have demonstrated practical methodologies to restore seagrass habitats and effectively return critical habitat functions to degraded coastal zone systems worldwide. Seagrass loss along the U.S. West Coast has precipitated decades of seagrass protection, conservation, and restoration efforts. Yet, mitigation transplanting efforts have prioritized Zostera marina (narrow-leaved eelgrass) in shallow, protected environments, while a dearth of information is available on species inhabiting offshore islands and exposed mainland coasts. In this study, we conducted a novel transplant of Zostera pacifica, a wide-leaved species found in depths of 7 – 20 m along the offshore islands and mainland coast of California. Transplants were conducted at three geographically distinct sites in Santa Monica Bay, coupled with continuous monitoring of biophysical parameters providing insight into physical drivers at transplant and donor sites. Utilizing in situ data, and environmental thresholds adapted from the literature for Z. marina, we performed exposure analyses to evaluate factors influencing Z. pacifica transplant performance. Exceedances of threshold values for environmental parameters, specifically, wave exposure and near-bed flow speeds (Hrms > 0.59 m and Urms > 0.1 m s-1), photosynthetically active radiation (< 3 and > 5 mol m-2 day-1) and dissolved oxygen (< 3 mg O2 L-1) exposure impacted transplant survivorship. These results suggest Z. pacifica persist in biophysically dynamic conditions and are sensitive to exceedances of thresholds, underlining the importance of pre-transplant site-selection processes to this species. These data represent the first holistic study of Z. pacifica transplanting on an exposed mainland coast, which provides a view into the baseline environmental envelopes within existing Z. pacifica habitat, and further, may serve as a model for investigating scalable open coast seagrass restoration for temperate regions.

Pustular mats from Shark Bay, Western Australia, host complex microbial communities bound within an organic matrix. These mats harbour many poorly characterized organisms with low relative abundances (<1%), such as candidate phyla Hydrogenedentota and Sumerlaeota. Here, we aim to constrain the metabolism and physiology of these candidate phyla by analyzing two representative metagenome-assembled genomes (MAGs) from a pustular mat. Metabolic reconstructions of these MAGs suggest facultatively anaerobic, chemoorganotrophic lifestyles of both organisms and predict that both MAGs can metabolize a diversity of carbohydrate substrates. Ca. Sumerlaeota possesses genes involved in degrading chitin, cellulose and other polysaccharides, while Ca. Hydrogenedentota can metabolize cellulose derivatives in addition to glycerol, fatty acids and phosphonates. Both Ca. phyla can respond to nitrosative stress and participate in nitrogen metabolism. Metabolic comparisons of MAGs from Shark Bay and those from various polyextreme environments (i.e., hot springs, hydrothermal vents, subsurface waters, anaerobic digesters, etc.) reveal similar metabolic capabilities and adaptations to hypersalinity, oxidative stress, antibiotics, UV radiation, nitrosative stress, heavy metal toxicity and life in surface-attached communities. These adaptations and capabilities may account for the widespread nature of these organisms and their contributions to biofilm communities in a range of extreme surface and subsurface environments.

The ability to anticipate marine habitat shifts responding to climate variability has high scientific and socioeconomic value. Here we quantify interannual-to-decadal predictability of habitat shifts by combining trait-based aerobic habitat constraints with a suite of initialized retrospective Earth System Model forecasts, for diverse marine ecotypes in the North American Large Marine Ecosystems. We find that aerobic habitat viability, defined by joint constraints of temperature and oxygen on organismal energy balance, is potentially predictable in the upper-600 m ocean, showing a substantial improvement over a simple persistence forecast. The skillful multiyear predictability is dominated by the oxygen component in most ecosystems, yielding higher predictability than previously estimated based on temperature alone. Notable predictability differences exist among ecotypes differing in temperature sensitivity of hypoxia vulnerability, especially along the northeast coast with predictability timescale ranging from 2 to 10 years. This tool will be critical in predicting marine habitat shifts in face of a changing climate.

Trait-based frameworks are increasingly used for predicting how ecological communities respond to ongoing global change. As species range shifts result in novel encounters between predators and prey, identifying prey guilds, based on a suite of shared traits, can distill complex species interactions, and aid in predicting food web dynamics. To support advances in trait-based research in open-ocean systems, we present the Pelagic Species Trait Database, an extensive resource documenting functional traits of 529 pelagic fish and invertebrate species in a single, open-source repository. We synthesized literature sources and online resources, conducted morphometric analysis of species images, as well as laboratory analyses of trawl-captured specimens to collate traits describing 1) habitat use and behavior, 2) morphology, 3) nutritional quality, and 4) population status information. Species in the dataset primarily inhabit the California Current system and broader NE Pacific Ocean, but also includes pelagic species known to be consumed by top ocean predators from other ocean basins. The aim of this dataset is to enhance the use of trait-based approaches in marine ecosystems and for predator populations worldwide.

As global climate change reorganizes marine ecosystems, understanding how predators will respond to variable prey resources is critical to forecasting future community dynamics. Prey traits that affect the foraging process and recur across unrelated taxa offer a means to better anticipate predator resource use by simplifying complex foraging dynamics. Here we compare taxonomic and trait-based indicators of resource use and selection for albacore tuna (Thunnus alalunga), a commercially valuable pelagic predator undergoing climate-driven range shifts. We synthesized datasets from 2005 to 2019 to evaluate diets of albacore tuna in relation to prey availability estimates from shipboard surveys in the California Current Large Marine Ecosystem. Analyses with these data reveal that albacore and trawl surveys sample different aspects of the pelagic system, with albacore consuming a subset of taxa identified within trawls. Albacore consistently selected coastal prey that are schooling, undefended, silvered and countershaded, and have high energy density — suggesting that ecological mechanisms driving albacore foraging outcomes may be conserved across time and space. Ecological traits mediating predator-prey interactions consistently distinguished albacore diets from assemblages sampled by trawls across years and regions. We demonstrate that a traits-based approach simplifies taxonomically diverse predator-prey interactions and may be a valuable tool to facilitate predictions of prey resource use in changing environments.