New paper on the diversity of Pterasteridae

A new article by Quentin Jossart et al. has just been published in the Zoological Journal of the Linnean Society. Our paper uses an integrative approach in discriminating species, for taxa characterized by the difficulty to identify species based on morphological characters. In this study, we combine genetics and morphology to assess the diversity of Pterasteridae, a sea star family diversified in deep-sea and polar environments. Because of their derived anatomy and the frequent loss of characters during preservation, Pterasteridae are a suitable case for an integrative study. The molecular identification of 191 specimens (mostly from the Southern Ocean) suggests 26–33 species in three genera (Diplopteraster, Hymenaster and Pteraster), which match the morphological identification in 54–62% of cases. The mismatches are either different molecular units that are morphologically indistinguishable (e.g. Pteraster stellifer units 2 and 4) or, conversely, nominal species that are genetically identical (e.g. Hymenaster coccinatus/ densus/praecoquis). Several species are shared between the Northern and Southern Hemispheres (e.g. Pteraster jordani/affinis). In conclusion, the taxonomic status of some groups is confirmed, but for others we find the need to re-evaluate the taxonomy at both genus and species levels. This work significantly increases the DNA barcode library of the Southern Ocean species and merges taxonomic information into an identification key that could become a baseline for future studies (pterasteridae-so.identificationkey.org).

You can findout more about the paper here.

We’re hiring!

In the framework of the collaborative FED-tWIN research programme between Belgian federal institutes and universities by the Belgian Federal Science Policy Office (BELSPO), the Project SO-BOMP (Southern Ocean Biodiversity Observations, Models and Policy) is recruiting a post-doctoral candidate (for a period of minimum 10 years). The position is shared between our Lab and the Royal Belgian Institute of Natural Sciences.

You can find the details of the offer here.

Tracking paper published in Nature

The Marine Biology Lab (Bruno Danis) was involved in a publication of in Nature in March 2020. Bruno Danis was a member of the data processing and analyzing team and participated in the drafting of the manuscript.

The paper is the result of a large data analysis which has direct implications for the conservation of large predators from the Southern Ocean. We assembled tracking data for 17 species to model Areas of Ecological Significance. Simultaneously, the data has been published in Open Access in the journal Scientific Data.

Abstract: Southern Ocean ecosystems are under pressure from resource exploitation and climate change. Mitigation requires the identification and protection of Areas of Ecological Significance (AESs), which have so far not been determined at the ocean-basin scale. Here, using assemblage-level tracking of marine predators, we identify AESs for this globally important region and assess current threats and protection levels. Integration of more than 4,000 tracks from 17 bird and mammal species reveals AESs around sub-Antarctic islands in the Atlantic and Indian Oceans and over the Antarctic continental shelf. Fishing pressure is disproportionately concentrated inside AESs, and climate change over the next century is predicted to impose pressure on these areas, particularly around the Antarctic continent. At present, 7.1% of the ocean south of 40°S is under formal protection, including 29% of the total AESs. The establishment and regular revision of networks of protection that encompass AESs are needed to provide long-term mitigation of growing pressures on Southern Ocean ecosystems.

New ecoregionalization paper published

A new paper on benthic ecoregionalization of the Southern Ocean has just been published in Global Change Biology, by Salomé Fabri-Ruiz et al.

The Southern Ocean (SO) is among the regions on Earth that are undergoing regionally the fastest environmental changes. The unique ecological features of its marine life make it particularly vulnerable to the multiple effects of climate change. A network of Marine Protected Areas (MPAs) has started to be implemented in the SO to protect marine ecosystems. However, considering future predictions of the Intergovernmental Panel on Climate Change (IPCC), the relevance of current, static, MPAs may be questioned under future scenarios. In this context, the ecoregionaliza- tion approach can prove promising in identifying well-delimited regions of common species composition and environmental settings. These so-called ecoregions are ex- pected to show similar biotic responses to environmental changes and can be used to define priority areas for the designation of new MPAs and the update of their current delimitation. In the present work, a benthic ecoregionalization of the entire SO is proposed for the first time based on abiotic environmental parameters and the distribution of echinoid fauna, a diversified and common member of Antarctic benthic ecosystems. A novel two-step approach was developed combining species distribution modeling with Random Forest and Gaussian Mixture modeling from spe- cies probabilities to define current ecoregions and predict future ecoregions under IPCC scenarios RCP 4.5 and 8.5. The ecological representativity of current and pro- posed MPAs of the SO is discussed with regard to the modeled benthic ecoregions. In all, 12 benthic ecoregions were determined under present conditions, they are representative of major biogeographic patterns already described. Our results show that the most dramatic changes can be expected along the Antarctic Peninsula, in East Antarctica and the sub-Antarctic islands under both IPCC scenarios. Our results advocate for a dynamic definition of MPAs, they also argue for improving the repre- sentativity of Antarctic ecoregions in proposed MPAs and support current proposals of Conservation of Antarctic Marine Living Resources for the creation of Antarctic MPAs.

You can access the paper online: https://authorservices.wiley.com/api/pdf/fullArticle/16657978

Black corals from the mesophotic waters of French Polynesia – or – How to be working hard when everyone thinks you’re taking holidays?

Let me ask you: what does first come to your mind when thinking about French Polynesia? Pristine white sandy beaches, luxurious island landscapes, turquoise waters, tropical fruits and fancy colourful cocktails?

The island of Moorea, French Polynesia

Well, it is! But this time, I travelled to French Polynesia to discover a completely different environment that is just starting to be explored thanks to novel technologies. This environment is called “mesophotic coral ecosystem” and has been receiving more and more attention in the recent years. Mesophotic coral ecosystems are found in tropical and subtropical regions at depths ranging from 30-40 meters and extending to over 150 meters. They are populated by a diversity of organisms such as corals, sponges, algae and fishes. 

From September to December 2019, a special collaboration between the scientists from the CRIOBE (Centre de Recherches Insulaires et Observatoire de l’Environnement) and the team of technical divers and explorers of Under The Pole allowed the exploration of a specific site on the outer reef of the island of Moorea from the surface to 120 meters depth. This project, led by Dr Laetitia Hédouin, gathered scientists from different field of research and with different expertise, allowing the complete characterization of the site from the environmental conditions (light, temperature) to the organismal biodiversity and abundance. 

The Under The Pole family (left) ; a diver at mesophotic depth (right)

Collecting samples and applying scientific diving techniques at such depth is challenging and requires a lot of preparation to ensure the security of the divers but also, to be able to do everything planned in the timeframe available. At 120 meters depth, the divers were able to stay for a maximum of 20 minutes, so every gesture has to be thought in advance to make the best out of that time. As part of my PhD research, I got the chance to participate in this special project and I focused on studying the antipatharians encountered by the divers on the site.

Antipatharians, also known as black corals, are anthozoans hexacorallians of distinct morphologies. They can be found from the tropics to the poles and studies have revealed their presence up to 8600 km deep. Despite this large distribution, they remain very poorly studied, mainly due to the logistical constraints associated with their study. Black corals can form dense “beds/forests” in several parts of the world and have been shown to play an important ecological role, in part due to their interactions with many organisms. In French Polynesia, the presence of black corals is known by local populations, in part because they have been fished for the jewellery industry in the past. Nonetheless, no scientific description of the assemblage of black coral species and distribution has ever been made in French Polynesia, and this represented one of my objective during this field trip (Results coming soon …).

A black coral in Tahiti (left) ; Map of the distribution of black corals in the world (right)

Another main aspect of my mission in the CRIOBE implied the maintenance of mesophotic antipatharians in aquaria to get a first insight into the metabolism of these organisms. We submitted them to different temperature treatments and evaluated their responses to heat stress through a combination of approaches, from a physiological to a subcellular biological organization level. Our preliminary results are already quite exciting… but this shall be for a latter post!

I would like to thank the Fonds Léopold III pour l’Exploration de la Nature for their financial support in this project. I also thank all the team from Under The Pole, all my colleagues and friends from the CRIOBE and all the wonderful persons I had the chance to meet and share moments with during this mission: Laetitia, Gonzalo, Yann, Alex, Caro, Anne, Fred, Benoit, Frank, Yannick, Françoise, Fabio, Lorenzo and his pastas, Kim, Ian, José, Alex and their cute baby black tips, Adeline, Julien, Camille, Will, Rohan, Zara (the Australian team), Elénonore and Aude, Pascal, Gilles, Cécile, Elina, Annaïg, Minouche & Minette. I hope to see you all very soon, either sharing a cold beer with fries in Belgium, or a pineapple juice with “poisson cru au lait de coco” in Moorea…

Mathilde Godefroid

New SDM paper out!

A new research paper by Charlène Guillaumot et al. “Broad-scale species distribution models applied to data-poor areas” has just been published in Progress in Oceanography. The paper specifically addresses Species Distribution Models, as they have been increasingly used over the past decades to characterise the spatial distribution and the ecological niche of various taxa. Validating predicted species distribution is important, especially when producing broad-scale models (i.e. at continental or oceanic scale) based on limited and spatially aggregated presence-only records. In the present study, several model calibration methods are compared and guidelines are provided to perform relevant SDMs using a Southern Ocean marine species, the starfish Odontaster validus Koehler, 1906, as a case study. The effect of the spatial aggregation of presence-only records on modelling performance is evaluated and the relevance of a target-background sampling procedure to correct for this effect is assessed. The accuracy of model validation is estimated using k-fold random and spatial cross- validation procedures. Finally, we evaluate the relevance of the Multivariate Environmental Similarity Surface (MESS) index to identify areas in which SDMs accurately interpolate and conversely, areas in which models extrapolate outside the environmental range of occurrence records. Results show that the random cross-validation procedure (i.e. a widely applied method, for which training
and test records are randomly selected in space) tends to over-estimate model performance when applied to spatially aggregated datasets. Spatial cross-validation procedures can compensate for this over-estimation effect but different spatial cross-validation procedures must be tested for their ability to reduce over-fitting while providing relevant validation scores. Model predictions show that SDM generalisation is limited when working with aggregated datasets at broad spatial scale. The MESS index calculated in our case study show that over half of the predicted area is highly uncertain due to extrapolation. Our work provides methodological guidelines to generate accurate model assessments at broad spatial scale when using limited and aggregated presence-only datasets. We highlight the importance of taking into account the presence of spatial aggregation in species records and using non-random cross-validation procedures. Evaluating the best calibration procedures and correcting for spatial biases should be considered ahead the modelling exercise to improve modelling relevance.

The full paper can be found here.

Hot off the press: new paper by Antonio Agüera

A new paper was published in MEPS by Antonio Agüera. the article focuses on the crown-of-thorns sea star. The paper is available in open access.

Here’s the abstract:

The crown-of-thorns starfish (COTS), Acanthaster cf. solaris, is an iconic keystone predator whose population outbreaks have devastating consequences for Indo-Pacific coral reefs. We tested the effects of algal food supply and larval density on the frequency of larval cloning by culturing the early bipinnaria larvae of COTS under variable conditions. Here we show that larval COTS are able to clone themselves in both low and high food conditions, and that the frequency of larval cloning increases with levels of food, but is unaffected by larval density. Across all density treatments (0.3, 1.0 and 3.0 larvae ml−1), the per-capita rate of cloning increased from 4.3% in low, oligotrophic conditions (0.17 μg chl a l−1) to 7.9% in high food conditions (1.7 μg chl a l−1). Larval cloning has the potential to increase both COTS larval supply and the dispersal distance of plank- tonic larval stages, both of which are critical factors in predicting the timing and location of out- breaks of this species. In addition, the relationship between algal food supply and larval cloning frequency lends support to bottom-up hypotheses (e.g. nutrient enrichment) as predictors of COTS outbreaks. Howe

New GBIF dataset published

In the framework of the marine biology field work organised by the lab, we will be publishing raw biodiversity data on a yearly basis on the Global Biodiversity Information Facility (GBIF). This dataset is the result of census exercises made by the participating students. The data includes occurrence from the intertidal zone, taken on a yearly basis (by different batches of students), for which identifications are systematically checked by the supervisors. The field work focuses on transects chosen in the the Bay of Wimereux (Pas-de-Calais, France) which are oriented towards contrasted ecological gradients.

You can find more about the dataset here.

 

Launch of the Belgica 121 crowdfunding campaign!

Marking the 121st anniversary since the first Antarctic expedition in human history, an international team of nine scientists embarks on a journey to the frozen continent. Our choice of transport: a small sail boat.

We are launching a crowdfunding campaign to support the  preparation of a documentary about this extraordinary adventure. This documentary is an intimate account of a small group of ambitious individuals, who are passionate about introducing a more sustainable way of conducting Polar research to the science community. The harsh beauty of the Antarctic landscape is reflected in the rawness of the footage, which will be captured by the scientists themselves – above and below water. Some of the most deeply poetic and profoundly personal texts have been produced by the original explorers during what we today refer to as the “Heroic Age of Antarctic Exploration”. While the old diaries speak of the struggle for survival, this documentary rather resembles a first-hand video journal about the fervour that comes with realising ones aspirations, the hope for making a change, the strains of the sea, and the intensifying pressure of no escape.

More information on our kickstarter project page…

New Publication: A Dynamic Energy Budget (DEB) model to describe Laternula elliptica (King, 1832) seasonal feeding and metabolism

A new research work from vERSO and RECTO projects has just been published at PlosOne. This work is part of the effort at BIOMAR (biomar.ulb.ac.be) to gain insight and understanding in the physiological performance of Antarctic invertebrates in a changing environment through the application of Dynamic Energy Budget theory and models (BIOMAR-DEB). This publication results from a collaboration with the Korean Polar Research Institute (KOPRI). Published in Open access, the full article can be read and downloaded from here.

Specimen of Laternula elliptica, research object of the published article © oikonos.org

 

A Dynamic Energy Budget (DEB) model to describe Laternula elliptica (King, 1832) seasonal feeding and metabolism

by Antonio Agüera, In-Young Ahn, Charlène Guillaumot & Bruno Danis

Abstract

Antarctic marine organisms are adapted to an extreme environment, characterized by a very low but stable temperature and a strong seasonality in food availability arousing from variations in day length. Ocean organisms are particularly vulnerable to global climate change with some regions being impacted by temperature increase and changes in primary production. Climate change also affects the biotic components of marine ecosystems and has an impact on the distribution and seasonal physiology of Antarctic marine organisms. Knowledge on the impact of climate change in key species is highly important because their performance affects ecosystem functioning. To predict the effects of climate change on marine ecosystems, a holistic understanding of the life history and physiology of Antarctic key species is urgently needed. DEB (Dynamic Energy Budget) theory captures the metabolic processes of an organism through its entire life cycle as a function of temperature and food availability. The DEB model is a tool that can be used to model lifetime feeding, growth, reproduction, and their responses to changes in biotic and abiotic conditions. In this study, we estimate the DEB model parameters for the bivalve Laternula elliptica using literature-extracted and field data. The DEB model we present here aims at better understanding the biology of L. elliptica and its levels of adaptation to its habitat with a special focus on food seasonality. The model parameters describe a metabolism specifically adapted to low temperatures, with a low maintenance cost and a high capacity to uptake and mobilise energy, providing this organism with a level of energetic performance matching that of related species from temperate regions. It was also found that L. elliptica has a large energy reserve that allows enduring long periods of starvation. Additionally, we applied DEB parameters to time-series data on biological traits (organism condition, gonad growth) to describe the effect of a varying environment in food and temperature on the organism condition and energy use. The DEB model developed here for L. elliptica allowed us to improve benchmark knowledge on the ecophysiology of this key species, providing new insights in the role of food availability and temperature on its life cycle and reproduction strategy.