Jamieson
Alan J.
Jamieson
Alan J.
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ArticleThe distribution of benthic biomass in hadal trenches : a modelling approach to investigate the effect of vertical and lateral organic matter transport to the seafloor(Elsevier, 2015-02-19) Ichino, Matteo C. ; Clark, Malcolm R. ; Drazen, Jeffrey C. ; Jamieson, Alan ; Jones, Daniel O. B. ; Martin, Adrian P. ; Rowden, Ashley A. ; Shank, Timothy M. ; Yancey, Paul H. ; Ruhl, Henry A.Most of our knowledge about deep-sea habitats is limited to bathyal (200–3000 m) and abyssal depths (3000–6000 m), while relatively little is known about the hadal zone (6000–11,000 m). The basic paradigm for the distribution of deep seafloor biomass suggests that the reduction in biomass and average body size of benthic animals along depth gradients is mainly related to surface productivity and remineralisation of sinking particulate organic carbon with depth. However, there is evidence that this pattern is somewhat reversed in hadal trenches by the funnelling of organic sediments, which would result in increased food availability along the axis of the trenches and towards their deeper regions. Therefore, despite the extreme hydrostatic pressure and remoteness from the pelagic food supply, it is hypothesized that biomass can increase with depth in hadal trenches. We developed a numerical model of gravitational lateral sediment transport along the seafloor as a function of slope, using the Kermadec Trench, near New Zealand, as a test environment. We propose that local topography (at a scale of tens of kilometres) and trench shape can be used to provide useful estimates of local accumulation of food and, therefore, patterns of benthic biomass. Orientation and steepness of local slopes are the drivers of organic sediment accumulation in the model, which result in higher biomass along the axis of the trench, especially in the deepest spots, and lower biomass on the slopes, from which most sediment is removed. The model outputs for the Kermadec Trench are in agreement with observations suggesting the occurrence of a funnelling effect and substantial spatial variability in biomass inside a trench. Further trench surveys will be needed to determine the degree to which seafloor currents are important compared with the gravity-driven transport modelled here. These outputs can also benefit future hadal investigations by highlighting areas of potential biological interest, on which to focus sampling effort. Comprehensive exploration of hadal trenches will, in turn, provide datasets for improving the model parameters and increasing predictive power.
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ArticleBarriers to gene flow in the deepest ocean ecosystems: Evidence from global population genomics of a cosmopolitan amphipod(American Association for the Advancement of Science, 2022-10-26) Weston, Johanna N. J. ; Jensen, Evelyn L. ; Hasoon, Megan S. R. ; Kitson, James J. N. ; Stewart, Heather A. ; Jamieson, Alan J.The deepest marine ecosystem, the hadal zone, hosts endemic biodiversity resulting from geographic isolation and environmental selection pressures. However, the pan-ocean distribution of some fauna challenges the concept that the hadal zone is a series of isolated island-like habitats. Whether this remains true at the population genomic level is untested. We investigated phylogeographic patterns of the amphipod, Bathycallisoma schellenbergi, from 12 hadal features across the Pacific, Atlantic, Indian, and Southern oceans and analyzed genome-wide single-nucleotide polymorphism markers and two mitochondrial regions. Despite a cosmopolitan distribution, populations were highly restricted to individual features with only limited gene flow between topographically connected features. This lack of connectivity suggests that populations are on separate evolutionary trajectories, with evidence of potential cryptic speciation at the Atacama Trench. Together, this global study demonstrates that the shallower ocean floor separating hadal features poses strong barriers to dispersal, driving genetic isolation and creating pockets of diversity to conserve.
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ArticleAmphipoda from depths exceeding 6,000 meters revisited 60 years on(Oxford University Press, 2023-05-15) Jamieson, Alan J. ; Weston, Johanna N. J.In the 1950s, the Danish Galathea Expedition undertook one of the first and most comprehensive explorations of our ocean’s hadal zone, depths extending from 6,000 to nearly 11,000 m, and presented a rich collection of the diversity of Amphipoda. The subsequent papers, however, concluded that these established ‘nothing essentially new’ to the existing knowledge of amphipod biology. Since Dahl’s foundational paper in 1959, amphipods, primarily from the superfamilies Lysianassoidea and Alicelloidea, emerged as one of the best-sampled hadal fauna, as these mobile invertebrates are readily recovered by different sampling techniques. Importantly, amphipods have become the model taxon, helping us to unlock knowledge about life in the hadal zone. In this review, we collate the knowledge gained since the Galathea Expedition and summarise the current understanding of how amphipods that appear during hadal exploration survive the trench environments. We discuss population structures across depth, inter-trench distribution and connectivity, applications in hadal microbiology, and, critically, how the hadal zone is being impacted by anthropogenic activity.