Climate change in the deep sea: assessing the resilience of deep-sea communities

Deep-sea habitats cover ~60% of the Earth's surface and are the largest and least explored environment on the planet. Deep-sea communities are sustained by primary production from the surface ocean and are sensitive to changes in its supply. Climate change is reducing food supply to the deep seafloor, with a substantial decline in biomass. This PhD will use a 30-year abyssal time series to explore how communities respond to changes in food supply, and combine empirical measurements, theory, and modeling to better understand energy flow and ecosystem function.
Objectives
This PhD will focus on three main questions:
1) How do deep-sea food webs respond to climate-induced changes in food supply? You will document changes in diet using the stable isotopic composition of fauna collected from the Porcupine Abyssal Plain (PAP); and use those data in numerical/model frameworks to link trophic ecology to ecosystem energy flows.
2) Do changes in food supply affect biological and ecological traits? You will include an examination of how body size, trophic indices, fecundity, species richness, are related to food supply.
3) The data generated will be used to further develop existing biodiversity indicators and targets to assess the impact of changing climate on deep-sea biodiversity and food webs, a key knowledge gap identified in the UK's assessment of progress towards Good Environmental Status (2019).
Novelty
This PhD is an exciting chance to explore how deep-sea ecosystems respond to climate-induced changes in food supply. You will gain experience in:
1. deep-sea sampling and time series analyses (research cruise to PAP Sustained Observatory);
2. invertebrate identification, stable isotope analysis and modelling;
3. translating research into policy-based tools to assess the impacts of climate change on UK deep-sea environments (JNCC placement).
Timeliness
The outcomes of the project have important implications for deep-sea benthic ecosystem monitoring and conservation.

Deep sea-floor habitats cover about 60% of the Earth's surface, and their ecosystems are intimately connected to upper-water processes. Abyssal (~3000m - 6000m) benthic communities are sustained by surface water primary production and are therefore sensitive to changes in this food supply. However, the impacts of climate change are reducing the quantity of food that reaches these communities. The Porcupine Abyssal Plain Sustained Observatory in the NE Atlantic Ocean is a time-series site with over 30 years of data, focusing on the connections between the surface and deep ocean. The current PhD project will use this data to explore how communities at this location respond to climate-induced changes in food supply, and it will have important implications for deep-sea benthic ecosystem monitoring and conservation. Benthic macrofauna will be collected from the Porcupine Abyssal Plain and analysed alongside previously collected specimens to calculate their stable isotopic compositions. These will be used to determine any changes in the organism's diets. Stable isotope ratios will be examined to determine how they change with body size, and used in numerical models to link trophic ecology to ecosystem energy flows. Ecological traits, such as fecundity and species richness, will also be examined to determine how they are related to food supply. The data generated will be used to determine how reduced food supply impacts benthic biomass at the abyssal seafloor, thus assessing the impacts of a changing climate on deep-sea biodiversity and food webs. Ultimately, the research will develop existing biodiversity indicators and targets, and will be translated into policy tools to assess the impacts of climate change on UK deep-sea environments.