ECOMAR; Ecosystem of the Mid-Atlantic Ridge at the Sub-Polar Front and Charlie Gibbs Fracture Zone.

Lead Research Organisation: Durham University
Department Name: Biological and Biomedical Sciences

Abstract

ECOMAR is a £2 million project aimed at understanding how physical and biogeochemical factors influence the distributions and structure of deep-sea communities, focusing on the fauna of the Mid-Atlantic Ridge at 4 sites in different environmental settings. The four sites are located on either side of the MAR and to the north and south of the Charlie Gibbs Fracture Zone (CGFZ), which coincides with the Sub-Polar Front. Using these localities we will investigate the effects of topography and currents on the distribution of the fauna, and the effects of varying organic input in two different biogeochemical settings. The work will focus on rocky slope fauna and sediment pockets in mixed bottoms rather than hydrothermal vents, which are relatively well known. In addition the MAR fauna will be compared with similar rocky slope fauna on the European and American continental margins to determine broad principals on the influence of physical and biogeochemical factors on the composition of the benthic fauna. The MAR is frontier territory and will lead to many new exciting discoveries. We will study the physical, chemical and biological environment of the MAR in terms of circulation, production, biomass and biodiversity. The MAR is a topographically difficult place to sample, which has no doubt contributed to the current lack of knowledge of this region. Therefore ECOMAR will employ the latest technologies to overcome this problem including precision acoustic sensors, instrumented moorings, autonomous lander vehicles, suspended camera systems and the new 6,500m rated research ROV Isis. The first of three proposed cruises to the region will produce detailed bathymetric maps of the study sites to aid deployment of instrument moorings and sampling equipment. In addition intensive CTD sampling will be employed to characterise the circulation in the vicinity of the Sub-Polar Front and provide calibration data for ongoing remote sensing research. The subsequent cruises will contine sampling programmes for pelagic biology using modern acoustic techniques as well as nets. In addition targeted benthic sampling and experimentation will take place using towed cameras and lander vehicles. Finally the ROV Isis will provide the only means of documenting and sampling the fauna of the MAR in addition to taking precision samples for geochemical analysis. The presence of the Sub-Polar Front and influence of the North Atlantic Current (NAC) provide for contrasting production regimes with cold, fresh and well stratified waters creating a biologically productive region to the north of the CGFZ. In contrast the waters to the south are warm, saline and less productive. The strength and position of the NAC will be monitored during the ECOMAR project to allow accurate estimates of export production to the benthos of the MAR. The use of remote sensing technologies, coupled with shipboard biological and physical measurements, will allow patterns of primary production over the MAR to be studied at higher spatial and temporal resolutions. By integrating satellite estimations of primary production with shipboard measurements estimates of export flux can be made and then compared with data from an array of four sediment trap moorings. The supply of food to the deep-sea floor plays a major role in structuring benthic communities and driving rate processes such as reproduction, metabolism and activity. By measuring the composition and quantity of this material both as phytoplankton, zooplankton and sedimenting aggregates the ECOMAR project will be able to identify the driving forces behind observed patterns of abundance, biomass and diversity in the fauna of the MAR.

Publications

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(Monty) Priede I (2013) Editorial note in Deep Sea Research Part II: Topical Studies in Oceanography

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Abell R (2013) Variability of particulate flux over the Mid-Atlantic Ridge in Deep Sea Research Part II: Topical Studies in Oceanography

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Alt C (2013) Trawled megafaunal invertebrate assemblages from bathyal depth of the Mid-Atlantic Ridge (48°-54°N) in Deep Sea Research Part II: Topical Studies in Oceanography

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Bell J (2013) Lebensspuren of the Bathyal Mid-Atlantic Ridge in Deep Sea Research Part II: Topical Studies in Oceanography

 
Description The aim of ECOMAR was to investigate the functioning of the Mid-Atlantic Ridge (MAR) ecosystem in the vicinity of the Charlie Gibbs Fracture Zone (CGFZ) and the sub-polar front (SPF) in particular to determine whether production, biomass and biodiversity over the ridge are enhanced compared with adjacent open ocean areas.

The MAR, extending to 3,704,404 sq.km was found to account for 44.7% of lower bathyal habitat (800-3500 m depth) in the North Atlantic dominated by fine soft sediment substrate (95% of area) on a series of flat terraces with intervening slopes either side of the ridge axis. Sediment trap and current meter moorings were placed at 2500 m depth on either side of the ridge axis at latitude 54N and 49N. The areas around these MAR stations were studied in detail.

Remote sensing and ship-board measurements showed that the eastward flowing North Atlantic Current tends across the MAR at the CGFZ. Current meters showed near-bottom flow to be strongly constrained to follow the north-south orientation of the topography. Frequent thermal fronts delineate the northern edge of the SPF with a continuous succession of energetic, long-lasting, slow moving eddies to the south.

The mean primary production calculated from satellite remote sensing over the MAR stations was 202 gC/sq.m/y compared with 228 gC/sq.m/y over a reference station above the Porcupine Abyssal Plain (PAP). Sediment traps on the MAR recorded a mean flux of 0.658 gC/sq.m/y compared with 0.905 gC/sq.m/y at PAP. There was no evidence of enhanced production or export flux over the MAR.

The mean biomass of benthic macrofauna in sediment core samples from the MAR was 56.10 mg C/sq.m and megafauna biomass from trawls was 9.29 mg C/sq.m; neither significantly different from 57.88 mg C/sq.m and 11.02 mg C/sq.m respectively predicted from the global CoML Fresh Biomass Database.

`The benthic biomass over the entire lower bathyal north MAR was estimated to be 258.9 kt C. A hypothetical flat plain at 3500 m depth in place of the MAR would contain 85.6 kt C, implying an increase of 173.3 kt C attributable to the presence of the Ridge. This is approximately equal to 167 kt C of estimated pelagic biomass displaced by the volume of the MAR.

Demersal and benthic species populating the MAR were found to be mainly typical North Atlantic lower-bathyal species known from the ocean margins. For most taxa, endemicity was not high; zero for fishes, cephalopods and benthic meiofaunal foraminifera and ~10% for benthic megafauna. Holothurians apparently exhibit higher endemism (~ 18%). Comparison of species lists from the MAR with published records for North Atlantic margins showed stronger similarities with the eastern rather than the western Atlantic. Demersal fish species richness was 9.5 per trawl at the MAR stations and 3.8 at 4800 m depth at PAP, indicating that mid-ocean elevation of the sea floor does increase benthic biodiversity compared with an abyssal plain but that species richness was equal to, or less than, values on the ocean margins at the same depths.

New species were discovered, notably the first Atlantic free-living deep sea Torquaratorid acorn worms (Hemichordata, Enteropneusta). Such discoveries cannot be taken as evidence of endemism since these species are likely to be found living elsewhere. Population genetic studies on some deep demersal fish species suggest that the MAR is not a barrier to gene flow; roundnose grenadier (Coryphaenoides rupestris) showed only slight intra-specific differentiation from the ocean margins and in blue hake (Antimora rostrata) there was no differentiation.

We conclude there is no enhancement of biological productivity over the MAR. Sea floor elevation provides habitat for benthic fauna otherwise unable to survive in mid ocean, possibly increasing biodiversity by virtue of the species area effect. Increase in benthic biomass is at the expense of pelagic biomass so total biomass remains constant.
URL http://www.oceanlab.abdn.ac.uk/ecomar/index.php
 
Description The findings from the published papers are being used as international policy develops for management of sensitive areas on the high seas. Former PIs from ECOMAR are engaged in this process.
First Year Of Impact 2010
Sector Environment
Impact Types Policy & public services

 
Description Regional Environmental Management Plan for the Mid Atlantic Ridge
Geographic Reach Australia 
Policy Influence Type Membership of a guideline committee
Impact The results from ECOMAR are being used in discussions of proposals for a Regional Environmental Management Plan for the Mid Atlantic Ridge especially as any management of the ridge must take into account connectivity to continental margins. Former PIs from ECOMAR e.g Dr DAVID BILLETT of NOCS are engaged in this process.
 
Description Strategic Environmental Management Plan for the Mid-Atlantic Ridge in the North Atlantic Ocean" (SEMPIA)
Geographic Reach Australia 
Policy Influence Type Participation in a advisory committee
Impact SEMPIA The results from ECOMAR are being used in a series of workshops convened from 2015 onwards with the aim of developing a Strategic Environmental Management Plan for the Mid-Atlantic Ridge in the North Atlantic Ocean" (SEMPIA). https://webgate.ec.europa.eu/maritimeforum/en/node/3972 ECOMAR results have been important in developing the concept of "Areas of Particular Environmental Interest "(APEIs) These workshops are being conducted under the auspices of International Seabed Authority (ISA) reporting to the Legal and Technical Commission (LTC) of the ISA in accordance with a following timetable that will lead to implementation of a Mid Atlantic Ridge Management Plan in 2020. 2015 SEMPIA I 2016 SEMPIA II 2017 LTC February 2017 LTC July and Council of ISA] 2018 spring SEMPIA III 2019 Draft MAR-EMP 2020 MAR-EMP The MAR EMP will provide a framework for management of exploitation of mineral and other resources of the Mid Atlantic Ridge.
URL http://webgate.ec.europa.eu/maritimeforum/en/node/3972