Geology topics

Lea-Anne Henry

Publications and source records attributed to Lea-Anne Henry.

4 recordsLinked to original sources

USGS2024

Multidisciplinary characterisation of the biodiversity, geomorphology, oceanography and glacial history of Bowditch Seamount in the Sargasso Sea

The first multidisciplinary characterisation of Bowditch Seamount in the Sargasso Sea was conducted to provide new baseline knowledge of the biodiversity, geomorphology, oceanography and glacial history of this seamount. A dropframe camera transect 1483–1562 m deep on the seamount documented 77 megafaunal taxa including Vulnerable Marine Ecosystem indicator taxa such as sponges, cold-water corals, and stalked crinoids. Seabed terrain analysis of multibeam echosounder data showed species varied significantly along this transect in response to local geomorphological variability (R 2 adj = 31%, p < 0.0001), with changes in seafloor relief and substrata driving species composition over the seamount. 14 C-calibrated and 230 Th-ages of fossil corals ( Desmophyllum dianthus ) collected by Van Veen grabs 1517 m deep showed corals thrived on the seamount ∼24 ka BP and ∼17 ka BP. Abrupt excursions between higher and lower radiogenic ε Nd -composition values of the skeletons suggested that D. dianthus persisted on the seamount over times of southern source water input and detrital sediments from the melting Laurentide Ice Sheet, respectively. In agreement with other studies from the western North Atlantic, living D. dianthus were absent in the contemporary setting at these depths, and suggest a significant re-organisation of the seamount community since the deglacial when ice-rafted debris of carbonates likely resulted in a lower aragonite compensation depth allowing D. dianthus to proliferate at deeper depths. New conductivity-depth-temperature profiling revealed the seamount at these depths is now bathed by highly oxygenated Labrador Sea Water (LSW) formed at high latitudes. Co-analysis of a newly constructed 70-year long time series of temperature and salinity for the Labrador Sea and Bermuda regions revealed a 10-year transit time from high latitudes to Bowditch Seamount. This multidisciplinary approach shows how geomorphology drives local biodiversity patterns, but also how upstream climatic forcing in subpolar regions may influence Bermuda's subtropical seamount ecosystem.

Deep Sea Research Part I: Oceanographic Research P↗

USGS2022

Influence of offshore oil and gas structures on seascape ecological connectivity

Offshore platforms, subsea pipelines, wells and related fixed structures supporting the oil and gas (O&G) industry are prevalent in oceans across the globe, with many approaching the end of their operational life and requiring decommissioning. Although structures can possess high ecological diversity and productivity, information on how they interact with broader ecological processes remains unclear. Here, we review the current state of knowledge on the role of O&G infrastructure in maintaining, altering or enhancing ecological connectivity with natural marine habitats. There is a paucity of studies on the subject with only 33 papers specifically targeting connectivity and O&G structures, although other studies provide important related information. Evidence for O&G structures facilitating vertical and horizontal seascape connectivity exists for larvae and mobile adult invertebrates, fish and megafauna; including threatened and commercially important species. The degree to which these structures represent a beneficial or detrimental net impact remains unclear, is complex and ultimately needs more research to determine the extent to which natural connectivity networks are conserved, enhanced or disrupted. We discuss the potential impacts of different decommissioning approaches on seascape connectivity and identify, through expert elicitation, critical knowledge gaps that, if addressed, may further inform decision making for the life cycle of O&G infrastructure, with relevance for other industries (e.g. renewables). The most highly ranked critical knowledge gap was a need to understand how O&G structures modify and influence the movement patterns of mobile species and dispersal stages of sessile marine species. Understanding how different decommissioning options affect species survival and movement was also highly ranked, as was understanding the extent to which O&G structures contribute to extending species distributions by providing rest stops, foraging habitat, and stepping stones. These questions could be addressed with further dedicated studies of animal movement in relation to structures using telemetry, molecular techniques and movement models. Our review and these priority questions provide a roadmap for advancing research needed to support evidence-based decision making for decommissioning O&G infrastructure.

Global Change Biology↗

USGS2019

Global observational needs and resources for marine biodiversity

The diversity of life in the sea is critical to the health of ocean ecosystems that support living resources and therefore essential to the economic, nutritional, recreational, and health needs of billions of people. Yet there is evidence that the biodiversity of many marine habitats is being altered in response to a changing climate and human activity. Understanding this change, and forecasting where changes are likely to occur, requires monitoring of organism diversity, distribution, abundance, and health. It requires a minimum of measurements including productivity and ecosystem function, species composition, allelic diversity, and genetic expression. These observations need to be complemented with metrics of environmental change and socio-economic drivers. However, existing global ocean observing infrastructure and programs often do not explicitly consider observations of marine biodiversity and associated processes. Much effort has focused on physical, chemical and some biogeochemical measurements. Broad partnerships, shared approaches, and best practices are now being organized to implement an integrated observing system that serves information to resource managers and decision-makers, scientists and educators, from local to global scales. This integrated observing system of ocean life is now possible due to recent developments among satellite, airborne, and in situ sensors in conjunction with increases in information system capability and capacity, along with an improved understanding of marine processes represented in new physical, biogeochemical, and biological models.

Frontiers in Marine Science↗

USGS2014

Global ocean conveyor lowers extinction risk in the deep sea

General paradigms of species extinction risk are urgently needed as global habitat loss and rapid climate change threaten Earth with what could be its sixth mass extinction. Using the stony coral Lophelia pertusa as a model organism with the potential for wide larval dispersal, we investigated how the global ocean conveyor drove an unprecedented post-glacial range expansion in Earth׳s largest biome, the deep sea. We compiled a unique ocean-scale dataset of published radiocarbon and uranium-series dates of fossil corals, the sedimentary protactinium–thorium record of Atlantic meridional overturning circulation (AMOC) strength, authigenic neodymium and lead isotopic ratios of circulation pathways, and coral biogeography, and integrated new Bayesian estimates of historic gene flow. Our compilation shows how the export of Southern Ocean and Mediterranean waters after the Younger Dryas 11.6 kyr ago simultaneously triggered two dispersal events in the western and eastern Atlantic respectively. Each pathway injected larvae from refugia into ocean currents powered by a re-invigorated AMOC that led to the fastest postglacial range expansion ever recorded, covering 7500 km in under 400 years. In addition to its role in modulating global climate, our study illuminates how the ocean conveyor creates broad geographic ranges that lower extinction risk in the deep sea.

Deep Sea Research Part A, Oceanographic Research P↗