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Mesopelagic Southern Ocean Prey and Predators

Periodic Reporting for period 2 - MESOPP (Mesopelagic Southern Ocean Prey and Predators)

Reporting period: 2017-12-01 to 2019-05-31

Antarctica and the Southern Ocean (SO) are critically important parts of the Earth system and climate. Observations and modelling indicate that the SO contributes to one third of the atmospheric CO2 absorption by the global Ocean. A large part of it is stored through biological mechanisms including photosynthesis and vertical transport in the food web by zooplankton and mesopelagic micronekton organisms. Quantifying this “biological pump” is a prerequisite for developing accurate global carbon models and reliable impacts of climate change on ocean ecosystems. In addition, micronekton are prey organisms of all larger predator species, including fish, whales and other marine mammals and seabirds. Finally, the potential huge biomass of mesopelagic fishes at global scale has raised some interest for the exploitation of this resource presented as a potential for “blue growth”. In all cases, better understanding of Earth climate system, conservation of biodiversity and improved management of oceanic ecosystems require to assess quantitatively and qualitatively the different groups of micronekton organisms. Therefore, there is a great need to establish in situ measurements along with methods for tuning models to these measurements and thus provide accurate estimates of micronekton biomass organisms and species communities and better knowledge of the dynamics of these ecosystem components. MESOPP aims to connect the marine ecosystem community across the fields of climate, oceanography and biology with a focus on the mesopelagic ocean system. First, the project provides an inventory of existing data and methods and develop capacity building with a network of collaboration between European and Australian research teams sharing similar interest on these key issues. Then, MESOPP is implementing a data infrastructure accessible publicly through its website ( to demonstrate the interest of providing standardised acoustic data to calibrate and validate micronekton and ecosystem models. Collaborations are encouraged to develop applications for the conservation and the management of marine resources and its biodiversity, as well as to understand the role of mesopelagics in the biologcial pump.MESOPP consortium is based on solid, skilled and complementary partners from Australia (AAD; CSIRO; UTas), United Kingdom (BAS); Norway (IMR) and France (CLS; UPMC). It is coordinated by CLS (P. Lehodey) in Toulouse, France.
The project started in June 2016 and has been active now for its first 18 months. During this period, the cooperation and collaboration between Australian and European partners was reinforced with the recruitment of 3 young scientists, the organisation of two workshops and the release of a project website on which are regularly published news related to the project (,as well as dedicated Facebook and Researchgate pages. A first workshop was organised in CSIRO, Hobart, Tasmania, following the kick-off meeting in Sep 2016. It focused on the standards and methods for acoustic data and micronekton models. The second workshop was organised by University of St Andrews, Scotland, in Jun 2017. It was devoted to the user requirements for the CIS (Central Information System) to be implemented with the project website to demonstrate the coupled acoustic-based observation-modelling system.

During the first half of the project, project partners have been working on the production of standardized reference datasets of 38 kHz acoustic data in three different regions of the Southern Ocean (Indian, Pacific and Atlantic). A common methodology and processing of data is developed for facilitating the use of these data in the modeling, based on international standards for acoustic data (ICES) and metadata formats (CF). These reference datasets are used to validate different modeling approaches and help to provide biomass estimates. The first version of the CIS has been released as planned ( Nov 2017). It provides publicly the series of bio-acoustic transects from the reference datasets using the same resolution and format. Each transect is detailed by its metadata. One additional dataset of collocated profiles of oceanographic variables and acoustic data provide precious information to analyse and model the vertical structure of the mesopelagic ocean. Selected data can be downloaded by registered user from a ftp data store.

A series of models was selected (SEAPODYM, ATLANTIS, SIZE-BASED, ECOPATH) for the SO domain. To assist in evaluation and intercomparison, a documentation of each model was prepared that included the approaches for standardisation and protocols to be used. From this documentation it was possible to define metadata and format needed to feed the CIS catalogue. As a first demonstration, outputs from a simulation with one model (SEAPODYM) was uploaded in the CIS. It provides micronekton biomass estimate for the SO at a resolution of ¼° x week for the period 2011-2016. It is expected to deliver a new simulation with a revised parameterisation achieved thanks to the assimilation of acoustic data in the model. Good progresses have been achieved in the methodology proposed to convert acoustic signal in biomass.
Acquisition of active acoustic data is the only synoptic approach to monitor the mesopelagic layer of the ocean. Such technology is becoming mature and is still not enough deployed despite its high scientific value potential. The institutes from Australia and Europe that are involved in MESOPP collect acoustic data in the SO and have developed first initiatives to integrate these key data in web databases (IMOS; SOOS, SONA). Based on these developments, common international standard methodology and format have been discussed and adopted. There are still some differences in the methods used to process data during the acquisition and in the subsequent processing. This includes the use of different software. Nevertheless, three reference datasets have been prepared on the same resolution and format and can be now easily downloaded through the MESOPP web site and used for inter-comparison and for development of observation model converting acoustic signal into biomass. Many issues complicate the biomass estimate using acoustic and net trawling. One promising approach developed with MESOPP is to consider large ecological provinces characterised by species communities associated to environmental conditions prevailing in these regions. In that case, mean conversion factors could be applied for the concerned ecoregions to reach regional and then global biomass estimates. Other key developments concern ecosystem and micronekton models for the SO. The first simulation output is described with metadata and can be downloaded from the MESOPP CIS. Key results here include original developments for the assimilation of data in one model allowing to estimate the parameters of the model, including those converting acoustic signal into biomass, with robust statistical methods. These model outputs provide new essential variables for the study of behaviour and population dynamics of large predators, e.g. whales and other marine mammals, fish or seabirds. They open the way to the first assessment of mesopelagic biomass of the SO based on a combination of network of observations, models and quantitative methods. The approach can be extended to the global Ocean.