Bureau of Ocean Energy Management

Sperm whales Physeter macrocephalus resident in the Gulf of Mexico are geographically isolated from other populations, making them vulnerable to the impacts of oil and gas exploration prevalent in the region. Despite long-standing research focused on sperm whales in the Gulf of Mexico, genetic structure within this population has not yet been investigated, nor has there been an assessment of the impacts of the 2010 Deepwater Horizon oil spill on population structure. Here, we investigated the spatial structure and temporal variation in mitochondrial DNA haplotype frequencies from 619 genetic samples collected from 377 individual sperm whales identified by microsatellite genotyping. This study uses samples collected over nearly 2 decades from 2000-2017 to support previous findings of genetic isolation of the Gulf of Mexico population from those in the Western North Atlantic (FST = 0.242, p < 0.001) and Caribbean (FST = 0.423, p < 0.001). In addition, we demonstrate significant changes in population structure within the Gulf of Mexico across both space and time. Most notably, the Central subregion, where the 2010 Deepwater Horizon oil spill originated, underwent a significant change in haplotype frequencies across time (FST = 0.141, p < 0.001), with implications for disruption of matrilineal population structure. Our findings of spatial and temporal structure within Gulf of Mexico sperm whales highlight the importance of regular monitoring and the establishment of baseline population data in the face of anthropogenic and environmental impacts.

Impact and vibratory pile driving for increasingly large offshore monopiles generate low frequency substrate-borne vibrations that radiate from the pile. These waves contain compression and shear wave components that propagate in sediments with poroelastic properties, potentially impacting benthic fauna around the monopile installation site. Additionally, these waves are coupled to the water column and can propagate along the interface between the water and seafloor, exciting additional acoustic waves and contributing to increased sound levels in the water column. Currently, no methods exist to mitigate the effects of these interface waves on marine ecosystems, so understanding how they are generated and the extent to which they propagate is imperative for assessing noise impacts on all marine species. The generation of these vibroacoustic waves is investigated for both vibratory and impact pile driving in a simulated 3D marine environment using numerical modelling. Near field models developed using the SPECFEM3D-Cartesian package are coupled to a Parabolic Equation model adapted to include poroelastic wave motion for far field propagation. Sediment properties are derived from data collected during recent benthic surveys. Predictions of particle motion for simulated ground waves are compared to measurements of ground vibration taken at recent or ongoing offshore windfarm installation sites.

The Peoples of the Arctic and Arctic health and sustainability are highly interconnected and essentially one and the same. An appropriate path to a sustainable Arctic involves a shift away from individual learning and achieving toward community leadership and the betterment of society. This article draws upon mindset theory from Western psychology and Indigenous relational accountability to propose and outline a model for achieving sustainability in the Arctic. The geographic focus is the North American Arctic. The principles of the argument and the foundations of the model may apply across the Circumpolar North. The paper is a call to action for social scientists and policy makers in the Arctic to implement an Indigenous-led and self-determined social science. Empowering and supporting Indigenous leaders and scholars to direct and conduct autonomous social science research would inherently produce well-being and sustainability for Indigenous communities and regions. The arguments are supported by an inductive analysis of peer-reviewed literature, and the model is organized and illustrated using a schematic of concentric circles. The foundational elements of the model include: Indigenous sovereignty, Indigenous ontology, Indigenous models of sustainability, and Indigenous scholarship. Environmental scientists, resource managers, and policy makers are directed to better understand, accept, and support Indigenous science as a comprehensive and valid knowledge system; change how they use key terminology in research; rethink research roles; and amend processes and timelines for research development and funding. To achieve the desired outcomes for community well-being and Arctic sustainability, Arctic social scientists should seriously consider centering Indigenous science, especially in Indigenous communities.

There have been substantially increased interest in effects of particle motion and substrate-borne vibration on fishes and aquatic invertebrates over the past decade. This is because these signals, unlike sound pressure, are the basis of hearing in most fishes and in all aquatic invertebrates. However, studies to address these issues continue to face challenges due to the diversity of species, the broad range of hearing mechanism, and the complexity of the physical acoustic environment in conducting studies. Additionally, we do not yet have a good understanding of, and mechanisms for, source generation, calibration, and measurements to be able to examine effects properly. Related to this is the critical issue is how research questions are applicable to regulatory agencies. In October 2023, the US Bureau of Ocean Energy Management held a workshop to address different research methodologies and their pros and cons as the basis for study of the behavioral and physiological responses to particle motion and substrate-borne vibration. Subsequently, a review was conducted linking research priorities previously identified concerning anthropogenic noise effects on animals with appropriate research methodologies. The review also provides recommendations on experimental settings that are most appropriate to address specific research questions for regulatory concerns.

Many Mississippi River Delta studies have shown recent declines in fluvial sediment load from the river and associated land loss. In contrast, recent sedimentary processes on the subaqueous delta are less documented. To help address this knowledge gap, multicores were collected offshore from the three main river outlets at water depths of 25–280 m in June 2017 just after the peak river discharge period, with locations selected based on 2017 U.S. Geological Survey seabed mapping. The coring locations included the undisturbed upper foreset, mudflow lobes, gullies, and the undisturbed prodelta. Nine multicores were analyzed for Beryllium-7 activity, and four cores were analyzed for excess Thorium-234 activity via gamma spectrometry, granulometry and X-radiography. Our results indicate a general trend of declining 7Be and 234Th activities and inventories with increasing distance from sources and in deeper water. The core X-radiographs are graded from the predominantly physically stratified nearshore to the more bioturbated offshore, consistent with the sedimentation patterns. Sediment focusing assessed via the 7Be and 234Th sediment inventories shows preferential sedimentation in gully and lobe environments, whereas the upper foreset and prodelta focusing factors are relatively depleted. Overall, short-term sediment deposition from the main fluvial source remains active offshore from all three major river outlets, despite the overall declining river load.

Initiated through Presidential direction and now codified, the National Ocean Mapping, Exploration, and Characterization (NOMEC) Council comprises leaders from U.S. federal agencies with a shared goal of mapping all waters of the United States and exploring and characterizing priority areas. The NOMEC Council’s two Interagency Working Groups, Ocean and Coastal Mapping (IWG-OCM) and Ocean Exploration and Characterization (IWG-OEC), both achieved major milestones recently with the 2023 release of the Draft Standard Ocean Mapping Protocols (SOMP) and the 2022 publication of the National Priorities for Ocean Exploration and Characterization. Building on this groundwork, the IWG-OEC is now looking to define and share best practices, guidelines, and resources for ocean exploration and characterization with the long-term goal of increasing community wide standardization to help achieve consistent common practices. First, the IWG-OEC plans to compile federal agency resources and share them in a newly developed online resource repository. The next phase is for the IWG-OEC to create opportunities for non-federal sectors to provide input on developing and populating this repository with additional content (existing standards and protocols, best practice and guidelines documents, etc.). After experts representing multiple sectors are identified, a series of results-oriented workshops are planned to provide input on all aspects of the data, products, and services from exploration and characterization. Finally, the IWG-OEC plans to widely share the online repository of best practices and standard operating procedures. A systematic, transparent, and collaborative process to share standards and protocols can help to enhance the interoperability of data and inform new lines of inquiry, discovery, research, and innovation.

Sound generated by pile installation using a down-the-hole (DTH) hammer is not well documented and differs in character from sound generated by conventional impact and vibratory pile driving. This paper describes underwater acoustic characteristics from DTH pile drilling during the installation of 0.84-m shafts within 1.22-m steel piles in Ketchikan, Alaska. The median single-strike sound exposure levels were 138 and 142 dB re 1 μPa2s at 10 m for each of the two piles, with cumulative sound exposure levels of 185 and 193 dB re 1 μPa2s at 10 m, respectively. The sound levels measured at Ketchikan were significantly lower than previous studies, and the sound was determined to be non-impulsive in this study as compared to impulsive in previous studies. These differences likely result from the DTH hammer not making direct contact with the pile, as had been the case in previous studies. Therefore, we suggest using the term DTH pile drilling to distinguish from DTH pile driving when the hammer strikes the pile. Further research is needed to investigate DTH piling techniques and associated sound-generating mechanisms and to differentiate the various types of sound emitted, which has important implications for the underwater sound regulatory community.

In assessing auditory effects on marine mammals from sound exposure, regulators currently estimate noise-induced threshold shifts (NITSs) based on classifying anthropogenic sound in two mutually exclusive categories: impulsive or non-impulsive. However, in real-world situations, marine mammals are often exposed to complex sound fields containing both impulsive and non-impulsive components, making it difficult or even impossible to accurately assess NITSs from sound exposure. One example of complex sound originates from down-the-hole (DTH) pile installation, which generates both impulsive sound from percussive drilling/striking and non-impulsive sound from simultaneous debris removal. This study employed a relatively simple approach of using kurtosis values to quantify the impulsiveness of two DTH pile installation datasets for six different marine mammal functional hearing groups. A kurtosis adjustment approach was then used—one that has been suggested to be able to predict human hearing loss from sound exposure—to calculate the correction factors for estimating NITSs of marine mammals exposed to DTH piling sound. Fur-ther research on marine mammal NITSs from complex sound exposure is needed to validate and improve this model.