Influence of population connectivity on depth-dependent diversity of deep-sea marine benthic biota

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, and 3) to 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.

This research has important implications for the sustainable management of the marine environment. Humans increasingly rely on the marine environment to supply us with food, building materials, fuel, and to soak up carbon slowing the progress of human induced climate change. However, our increasing use of this environment is starting to affect is 'normal' functioning, affecting the processes that allow it to provide us with food, fuel, etc. To try to help protect and sustain these 'ecosystem functions', Governments all over the world are setting up networks of Marine Protected Areas (MPAs) to ensure against serious ecosystem disturbance and cascade effects resulting from overexploitation that ultimately impair ecosystem function. There are many questions to be answered when trying to set up an MPA network, but one important question is where to put them to make sure that the populations that live within them are not isolated from each other but are connected. This research will help answer this question in the deep sea, and thus help managers, governments and society ensure the long term health of the ocean.

Who will benefit?
Beneficiaries of the proposed research include UK Government Departments (Defra and Marine Scotland), and their advisory body the Joint Nature Conservation Committee. At a European level beneficiaries include the Directorate-General for Maritime Affairs and Fisheries, the Environment Directorate-General, all contracting parties to the Oslo-Paris (OSPAR) Convention, and groups who provide advice to these bodies (International Council for the Exploration of the Sea), as well as fisheries regulatory groups such as the North East Atlantic Fisheries Commission and North Western Waters Regional Advisory Council. At a Global level beneficiaries include all contracting parties to the Convention on Biological Diversity, particularly those with extensive deep-sea areas within their exclusive economic zones. In addition to society a broad cross-section of the academic community will also benefit, from evolutionary biologists to demographers, macroecologists, biogeographers and oceanographers

How will they benefit?
One of the biggest challenges facing marine environmental managers the world over is how to implement an 'ecologically coherent' network of marine protected areas (MPAs). This task is a requirement of national (e.g. UK Marine Act), regional (European Marine Strategy Framework Directive, OSPAR Convention), and global (Convention on Biological Diversity) policy, and the UK has a legal obligation to implement a network. In order to be successful and acceptable to those people and livelihoods affected by the potential restrictions placed on human activities within these protected areas, it is vital that decisions about where to place them are based on the best scientific data available. Although there is a small but growing body of research on MPA selection criteria including representation of habitats, percentage of target area requirements, and size of MPAs, there is very limited directed research addressing MPA network design, and specifically the spacing of MPAs within a network in order to ensure connectivity of protected populations. This situation is even more extreme for the deep-sea where data are sparse and human impacts are difficult to quantify.

The proposed research aims to investigate population connectivity in the deep sea; specifically addressing potential variation in connectivity with depth, connectivity among spatially fragmented habitat (seamounts, banks, oceanic islands), and the potential for bio-oceanographic models to predict large scale connectivity patterns. The outputs of this research would provide the basis for robust scientific advice on the spacing of MPAs within a network and the importance of seamounts and banks to network coherence. In addition it would potentially provide a freely available scientifically validated tool (bio-oceanographic model) for modelling connectivity in other areas. The PIs positions on advisory bodies at European and Global levels will ensure this advice is fed straight into policy and environmental management decisions.

The drivers behind the policy to conserve biodiversity are not for the sake of conservation itself, but for the sustainability of the growing human populations in terms of food and resources. Ultimately providing science to support these policy decisions is to the benefit of society as a whole.