Details

This project was funded by Natural Environment Research Council parent and child grants NE/K011855/1 and NE/K013513/1, entitled 'Influence of population connectivity on depth-dependent diversity of deep-sea marine benthic biota', with the former, parent grant led by Dr Kerry Howell, University of Plymouth, and the latter child grant led by Professor Alex Rogers, University of Oxford. The project was also in partnership with the Joint Nature Conservation Committee (JNCC) and the British Geological Survey (BGS). The project was active between 16^th November 2015 and 31^st December 2019.

Data were collected on James Cook cruise JC136 between 14^th May and 23^rd June 2016. During the cruise, 5 sites in the North East Atlantic (Rockall Bank, George Bligh Bank, Anton Dohrn Seamount, Wyville-Thomson Ridge, and Rosemary Bank) were visited undertaking 27 ROV dives, 12 AUV missions, 43 CTD casts, 2 mooring deployments. 3630 biological samples were obtained from sufficient depth and site coverage for molecular analysis for 3 target species.

Species populations are connected to each other through both movement of adults (migration) and eggs, larvae and juveniles (dispersal). If populations become isolated from one another (i.e. are no longer connected), then through genetic mutation, drift and natural selection, they may become so different that they evolve into new biological species. Understanding how populations become isolated is critical to understanding the process of speciation. In the marine environment many species do not move as adults (e.g. corals) or move very slowly (sea urchins). This means that for different adult populations to remain connected they rely on dispersal of early life history stages. Most marine species have a larval stage that lives in the plankton for a period of time, moving with the currents, before settling in a new area. It is larval dispersal that keeps distant populations connected. So understanding patterns of larval dispersal is important to understanding connectivity.

In the deep-sea (>200m) the bathyal region of the continental slope has been identified as supporting high species richness and being an area where the rate of origination of new species may also be high. The reasons for this are not clear, but given the importance of connectivity to population isolation and speciation, it follows that the key to understanding patterns of species diversity in this region lies in understanding connectivity. New research has suggested that because the speed of the currents that carry larvae decreases as you go deeper, larvae might not be able to travel as far, leading to a greater tendency for populations at bathyal depths to become isolated over a given distance, and thus increasing the chances of speciation.

This study aims to test this theory by investigating how patterns of connectivity vary with depth. This will be done in 3 ways:

1. Using genetic analysis (similar to DNA fingerprinting) to compare how related distant populations are and if they become less closely related as you go deeper
2. Using a model of ocean currents to simulate the movement of larvae between sites
3. Io look at the range and abundance of species present at distant locations to see if those at shallower depths are more similar to each-other than those at bathyal depths.