Topographic Analysis of Intertidal Polychaete Reefs (Sabellaria alveolata) at a Very High Spatial Resolution

In temperate coastal regions of Western Europe, the polychaete Sabellaria alveolata (Linné) builds large intertidal reefs of several hectares on soft-bottom substrates. These reefs are protected by the European Habitat Directive EEC/92/43 under the status of biogenic structures hosting a high biodiversity and providing ecological functions such as protection against coastal erosion. As an alternative to time-consuming field campaigns, a UAV-based Structure-from-Motion photogrammetric survey was carried out in October 2020 over Noirmoutier Island (France) where the second-largest known European reef is located in a tidal delta. A DJI Phantom 4 Multispectral UAV provided a topographic dataset at very high resolutions of 5 cm/pixel for the Digital Surface Model (DSM) and 2.63 cm/pixel for the multispectral orthomosaic images. The reef footprint was mapped using a combination of two topographic indices: the Topographic Openness Index and the Topographic Position Index. The reef structures covered an area of 8.15 ha, with 89% corresponding to the main reef composed of connected and continuous biogenic structures, 7.6% of large isolated structures (<60 m2), and 4.4% of small isolated reef clumps (<2 m2). To further describe the topographic complexity of the reef, the Geomorphon landform classification was used. The spatial distribution of tabular platforms considered as a healthy stage of the reef in contrast to a degraded stage was mapped with a proxy that consists in comparing the reef volume to a theoretical tabular-shaped reef volume. Epibionts colonizing the reef (macroalgae, mussels, and oysters) were also mapped by combining multispectral indices such as the Normalised Difference Vegetation Index and simple band ratios with topographic indices. A confusion matrix showed that macroalgae and mussels were satisfactorily identified but that oysters could not be detected by an automated procedure due to their spectral complexity. The topographic indices used in this work should now be further exploited to propose a health index for these large intertidal reefs

Decadal increase in the ecological status of a North-Atlantic intertidal seagrass meadow observed with multi-mission satellite time-series

International audienceSeagrass meadows are monitored in the frame of several environmental programs worldwide, including the Water Framework Directive (WFD), to evaluate the ecological status of European coastal and transitional water bodies. The large size, spatial complexity, and interannual variability of seagrass ecosystems significantly challenge field monitoring. In this study, a multi-mission satellite time-series was used to estimate long-term changes in seagrass status in a macrotidal system dominated by Zostera noltei, at Bourgneuf Bay (French Atlantic coast). Metrics of seagrass extent and density were obtained from Earth Observation (EO) using validated and inter-calibrated Landsat, SPOT and Sentinel2 data from 1985 to 2020. The information provided by satellite data made it possible to compute and compare several seagrass indicators currently in use in several European countries (France, Portugal and UK) within the WFD. Both the seagrass extent and meadow-averaged density displayed increasing trends since 1985. A time-series of merged observations from various satellites revealed a high degree of interannual variability in seagrass extent, with abrupt losses (up to 50% within one year) alternating with periods of slow recovery (typically 4-6 years). The seagrass meadow which was in a moderate status (sensu the WFD) in the 1980s, achieved an overall recurrent good or high status since the mid-1990s. Altogether, the methods and results presented here demonstrated that EO is a reliable source of information for mapping and assessing the status of intertidal seagrass, complementing in situ measurements by providing long-term, spatial view and standardized observation framework. We recommend the systematic use of EO time-series in complement to traditional field measurements in seagrass monitoring programs such as the WFD

Mapping intertidal oyster farms using unmanned aerial vehicles (UAV) high-resolution multispectral data

In France, oyster aquaculture has been historically developed in intertidal zones, with shellfish farming areas covering much of the Atlantic coast. Monitoring these off-bottom cultures where oysters are grown in plastic mesh-bags set on trestle tables is mandatory for the maritime administration to check compliance with a Structural Plan Document (SPD), while also being important for stock assessment in relation to carrying capacity issues. However, traditional monitoring methods are time-consuming, labor-intensive, and inefficient in covering large intertidal areas. In this study, we used a new GIS-based analytical method to assess the potential of high-resolution Unmanned Aerial Vehicle (UAV) multispectral data to retrieve spatial information on oyster-farming structures using Bourgneuf Bay (France) as a case-study. A non-parametric machine learning algorithm was applied to four UAV flight orthomosaics collected at different altitudes (12, 30, 50, and 120 m) to identify oyster mesh-bags. These supervised classifications achieved overall accuracies above 95% for all tested altitudes. In addition, an accurate distinction of oyster-bag mesh sizes (4, 9 and 14 mm) was obtained for 12–50 m flights, but there was a lower accuracy at 120 m. Across all flights, the 4 mm mesh size was the least well detected (72.14% Producer Accuracy). This information can be used to identify bags with specific mesh-sizes used for spat or adult grow out. Finally, we accurately measured oyster table heights using a high-resolution Digital Surface Model (DSM) derived from Structure from Motion (SfM) photogrammetry. The 50 m flight was suggested as the best compromise to obtain precise measurements of the oyster table heights while covering larger areas than lower altitude flights. This demonstrates that UAV technology can provide a set of spatial variables relevant for shellfish farmers and coastal managers in an efficient, rapid, and non-destructive way to monitor the extent and characteristics of oyster-farming areas regularly.This research was funded by grants PY20-00244 SAT4ALGAE by Junta de Andalucía. A.R. is supported by grant FPU19/04557 funded by Ministry of Universities of the Spanish Government. H.P. was supported by the Erasmus+: Key Action 1 – Erasmus Mundus Joint Master Degrees (EMJMD) (Grant No. 599111-EPP-1-2018-1-EL-EPPKA1-JMD-MOB) for the EMJMD in Aquaculture, Environment and Society PLUS (ACES+). This work represents a contribution to CSIC Thematic Interdisciplinary Platform PTI TELEDETECT.Peer reviewe

Remote sensing in seagrass ecology: coupled dynamics between migratory herbivorous birds and intertidal meadows observed by satellite during four decades.

International audienc

Chicoric acid is an antioxidant molecule that stimulates AMP kinase pathway in L6 myotubes and extends lifespan in Caenorhabditis elegans.

Chicoric acid (CA) is a caffeoyl derivative previously described as having potential anti-diabetic properties. As similarities in cellular mechanism similarities between diabetes and aging have been shown, we explored on L6 myotubes the effect of CA on the modulation of intracellular pathways involved in diabetes and aging. We also determined its influence on lifespan of Caenorhabditis elegans worm (C. elegans). In L6 myotubes, CA was a potent reactive oxygen species (ROS) scavenger, reducing ROS accumulation under basal as well as oxidative stress conditions. CA also stimulated the AMP-activated kinase (AMPK) pathway and displayed various features associated with AMPK activation: CA (a) enhanced oxidative enzymatic defences through increase in glutathion peroxidase (GPx) and superoxide dismutase (SOD) activities, (b) favoured mitochondria protection against oxidative damage through up-regulation of MnSOD protein expression, (c) increased mitochondrial biogenesis as suggested by increases in complex II and citrate synthase activities, along with up-regulation of PGC-1α mRNA expression and (d) inhibited the insulin/Akt/mTOR pathway. As AMPK stimulators (e.g. the anti-diabetic agent meformin or polyphenols such as epigallocatechingallate or quercetin) were shown to extend lifespan in C. elegans, we also determined the effect of CA on the same model. A concentration-dependant lifespan extension was observed with CA (5-100 μM). These data indicate that CA is a potent antioxidant compound activating the AMPK pathway in L6 myotubes. Similarly to other AMPK stimulators, CA is able to extend C. elegans lifespan, an effect measurable even at the micromolar range. Future studies will explore CA molecular targets and give new insights about its possible effects on metabolic and aging-related diseases

Biodiversity from Remote Sensing of Coastal Areas for Science and Societal Applications: User Requirements Synthesis and Preliminary Results

The Convention on Biological Diversity and the UN Decade of the Ocean have set targets to reaching ocean sustainability by 2050. To assess if these targets have been met, each target is linked to a set of indicators measuring Essential Biodiversity Variables (EBV). Marine and coastal habitats are under threat through numerous anthropogenic stressors. At the same time, measuring indicators in the marine and coastal environment is costly, time consuming and unreliable due to weather conditions leading to a dearth of data in these areas. Satellite remote sensing is proposed as a tool to complement in-situ observations. It can measure some EBVs in a more consistent and reliable manner and increase the area covered as well as spatial and temporal resolution. However, due to the need for specific training and infrastructure to analyse raw remote sensing data, there is a need to understand the end users’ requirements to use such data for biodiversity monitoring. The European Space Agency funded Bi-COME project (Biodiversity of the Coastal Ocean: Monitoring with Earth Observation) aims to develop products that help measuring more EBVs more effectively and to involve stakeholders in the development process. To this end, we are collecting the user requirements of seven case study partners using semi-structured interviews. We aim to compare their current approaches with new Earth Observation products by learning about their current methods to measure EBVs, ask what they would like to achieve by the use of improved Earth Observation products and how they are able to access such data. The case study partners consist of managers and data providers to local environmental managers of intertidal, subtidal and pelagic marine habitats. The case study sites consist of sandy intertidal habitat in France, seagrass habitats in Mozambique and pelagic floating vegetation in India and the Caribbean Sea. We plan to interview the case study partners after they have tested the products created so that they can help shape the development according to their needs. This presentation will discuss results from the first set of interviews

Influence of chicoric acid on antioxidant enzymes in L6 myotubes.

<p>Cells were cultured in the presence or absence of CA (50 µM) for 10 days before measurements of the enzymatic activities of GPx (<b>A</b>) or SOD (<b>B</b>), or analysis of MnSOD protein expression (<b>C</b>). Enzymatic activities are expressed as mU/mg protein and indicated as means ± SEM (n = 5); significantly different from control at * p<0.05. Representative immunoblot is shown.</p

Influence of chicoric acid on PGC-1α mRNA expression in L6 myotubes.

<p>Cells were treated with 5 µM or 50 µM CA for the indicated times. PGC-1α mRNA levels were measured by quantitative RT PCR and normalized relatively to RPS9 mRNA expression. Values are means ± SEM (n = 5); significantly different from control of the same time at * p<0.05.</p