Ice, Ice, Babies! The role of periodic and catastrophic ice loss on species connectivity in polar systems.

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Using ice-ocean models to predict changes in larval dispersal under future warming scenarios. The discovery of a sponge assemblage on a boulder beneath the Filchner-Ronne Ice Shelf (FRIS), 260km from open water, by Griffiths et al. (2021) marked the first ever observation of hard substrate sessile life within an ice shelf cavity. No species level identification for the organisms present on the FRIS boulder has been possible, nor do we know the age or origin of this assemblage. My previous research into this topic was solely based upon identifying whether connectivity existed between the sponge assemblage beneath the FRIS and those sponge populations present on the Weddell Sea continental shelf, and sponge populations further afield at the Eckström Shelf. This was carried out following the development of a biologically-accurate sponge life cycle model, which includes both the planktonic larval stage and the adult sessile stage - other dispersal modelling publications focus solely on the larval stage.The initial stages of this research will be composed of a subject review focused on reproductive dynamics of cold-water and deep-sea sponges, and the underlying oceanographic conditions within the Weddell Sea and FRIS region. Further refinement of the existing dispersal model will also occur, to introduce tides and more accurate reproduction, growth and mortality timescales for the sponges within the model. The Weddell Sea is a changing ecosystem in which seasonal sea ice variations directly impact oceanographic conditions both beneath the FRIS and on the Weddell Sea continental shelf. Changes in ice cover as a result of anthropogenic climate change will lead to further oceanographic variation, and this project will utilise a hydrodynamic dispersal model to assess how this variation will impact larval connectivity under the following climatic scenarios:i) Seasons of low sea ice coverii) Polynya presence in the Weddell Seaiii) Iceberg calving eventsiv) Ice shelf collapse The results of these dispersal simulations may be utilised when considering management strategies for sessile, benthic populations within the Weddell Sea however in addition to this, this modelling framework has potential applications for larval dispersal modelling for other organisms such as cold-water corals or icefish. Alternatively, changing the oceanographic data on which the model is built means that the operating domain may be transferred to the Ross Sea or areas within the Arctic, for modelling applications in those regions under future warming scenarios.