Coastal Aquaculture Extraction Using GF-3 Fully Polarimetric SAR Imagery: A Framework Integrating UNet++ with Marker-Controlled Watershed Segmentation

Coastal aquaculture monitoring is vital for sustainable offshore aquaculture management. However, the dense distribution and various sizes of aquacultures make it challenging to accurately extract the boundaries of aquaculture ponds. In this study, we develop a novel combined framework that integrates UNet++ with a marker-controlled watershed segmentation strategy to facilitate aquaculture boundary extraction from fully polarimetric GaoFen-3 SAR imagery. First, four polarimetric decomposition algorithms were applied to extract 13 polarimetric scattering features. Together with the nine other polarisation and texture features, a total of 22 polarimetric features were then extracted, among which four were optimised according to the separability index. Subsequently, to reduce the “adhesion” phenomenon and separate adjacent and even adhering ponds into individual aquaculture units, two UNet++ subnetworks were utilised to construct the marker and foreground functions, the results of which were then used in the marker-controlled watershed algorithm to obtain refined aquaculture results. A multiclass segmentation strategy that divides the intermediate markers into three categories (aquaculture, background and dikes) was applied to the marker function. In addition, a boundary patch refinement postprocessing strategy was applied to the two subnetworks to extract and repair the complex/error-prone boundaries of the aquaculture ponds, followed by a morphological operation that was conducted for label augmentation. An experimental investigation performed to extract individual aquacultures in the Yancheng Coastal Wetlands indicated that the crucial features for aquacultures are Shannon entropy (SE), the intensity component of SE (SE_I) and the corresponding mean texture features (Mean_SE and Mean_SE_I). When the optimal features were introduced, our proposed method performed better than standard UNet++ in aquaculture extraction, achieving improvements of 1.8%, 3.2%, 21.7% and 12.1% in F1, IoU, MR and insF1, respectively. The experimental results indicate that the proposed method can handle the adhesion of both adjacent objects and unclear boundaries effectively and capture clear and refined aquaculture boundaries

Remote Sensing of the Oceans

This book covers different topics in the framework of remote sensing of the oceans. Latest research advancements and brand-new studies are presented that address the exploitation of remote sensing instruments and simulation tools to improve the understanding of ocean processes and enable cutting-edge applications with the aim of preserving the ocean environment and supporting the blue economy. Hence, this book provides a reference framework for state-of-the-art remote sensing methods that deal with the generation of added-value products and the geophysical information retrieval in related fields, including: Oil spill detection and discrimination; Analysis of tropical cyclones and sea echoes; Shoreline and aquaculture area extraction; Monitoring coastal marine litter and moving vessels; Processing of SAR, HF radar and UAV measurements

Remote Sensing of the Aquatic Environments

The book highlights recent research efforts in the monitoring of aquatic districts with remote sensing observations and proximal sensing technology integrated with laboratory measurements. Optical satellite imagery gathered at spatial resolutions down to few meters has been used for quantitative estimations of harmful algal bloom extent and Chl-a mapping, as well as winds and currents from SAR acquisitions. The knowledge and understanding gained from this book can be used for the sustainable management of bodies of water across our planet

First results of phytoplankton spatial dynamics in two NW-Mediterranean bays from Chlorophyll-a estimates using Sentinel 2: potential implications for aquaculture

Shellfish aquaculture has a major socioeconomic impact on coastal areas, thus it is necessary to develop support tools for its management. In this sense, phytoplankton monitoring is crucial, as it is the main source of food for shellfish farming. The aim of this study was to assess the applicability of Sentinel 2 multispectral imagery (MSI) to monitor the phytoplankton biomass at Ebro Delta bays and to assess its potential as a tool for shellfish management. In situ chlorophyll-a data from Ebro Delta bays (NE Spain) were coupled with several band combination and band ratio spectral indices derived from Sentinel 2A levels 1C and 2A for time-series mapping. The best results (AIC = 72.17, APD < 10%, and MAE < 0.7 mg/m3) were obtained with a simple blue-to-green ratio applied over Rayleigh corrected images. Sentinel 2–derived maps provided coverage of the farm sites at both bays allowing relating the spatiotemporal distribution of phytoplankton with the environmental forcing under different states of the bays. The applied methodology will be further improved but the results show the potential of using Sentinel 2 MSI imagery as a tool for assessing phytoplankton spatiotemporal dynamics and to encourage better future practices in the management of the aquaculture in Ebro Delta bays.info:eu-repo/semantics/publishedVersio

Goods and Services of Marine Bivalves

The aim of this book is to review and analyse the goods and services of bivalve shellfish. How they are defined, what determines the ecological functions that are the basis for the goods and services, what controversies in the use of goods and services exist, and what is needed for sustainable exploitation of bivalves from the perspective of the various stakeholders. The book is focused on the goods and services, and not on impacts of shellfish aquaculture on the benthic environment, or on threats like biotoxins; neither is it a shellfish culture handbook although it can be used in evaluating shellfish culture. The reviews and analysis are based on case studies that exemplify the concept, and show the strengths and weaknesses of the current applications. The multi-authored reviews cover ecological, economic and social aspects of bivalve goods and services. The book provides new insights for scientists, students, shellfish producers, policy advisors, nature conservationists and decision makers. This book is open access under the CC BY license.publishedVersio

Characterisation of Crassostrea gigas (Thunberg, 1793) farming environment, physiological performances and challenges in shallow Mediterranean lagoons

The Italian territory is covered of approximately 384,000 ha of coastal lagoons and these could represent potential location for Pacific oyster, Crassostrea gigas (Thunberg, 1793) farming. Approximately 10,000 ha of the coastal Italian lagoons are located in the Sardinian region, these are currently not utilized for shellfish farming, and present suitable environmental conditions that allow for good growth rates and optimal market quality for Pacific oysters farming. Therefore, these lagoons can become potential farming sites to increase this industry in the Italian territory, where the demand for this shellfish species cannot be met by domestic production alone. The aim of this PhD study was to enhance Pacific oyster farming in Mediterranean coastal lagoons taking into account local aquaculture industry’s ambitions and challenges, therefore different Pacific oyster culture aspects were investigated. To achieve the goals of this PhD study, novel farming tools and their benefits to Pacific oyster farming were investigated. Moreover, the validation of ShellSIM® growth model in a new environment was carried out, providing a new validated tool to farmers and stakeholders to monitor oysters’ performances and estimate productivity in local waters. Finally, a site selection methodology was developed to identify suitable sites for Pacific oyster farming, and potential risks to consumers linked to microplastics pollution in coastal areas and uptake in Pacific oyster were investigated. Taken together, the results of this PhD study provide new insight on ways to improve C. gigas sustainable aquaculture industry in Mediterranean coastal lagoons, with particular focus on the Italian territory

Phytoplankton dynamics and bio-optical variables associated with Harmful Algal Blooms in aquaculture zones

The surveillance of Harmful Algal Blooms (HABs) in aquaculture zones is a crucial component in monitoring and mitigation of adverse effects caused by accumulation of high biomass of algal cells and/or associated toxins. Integrated findings of this thesis strongly stress the significance of synoptic bio-optical and conventional measures for efficient surveillance of HABs and their environmental triggers over required spatio-temporal scales, here shown for a case study in the Ebro Delta, NW Mediterranean. In particular, the installation of an environmental observatory in the Ebro Delta aquaculture area, and the capability of a radiometric sensor system as key component are highly motivated by study results. Yet it was clearly shown that for the interpretation of bio-optical data, detailed knowledge on bloom characteristics is crucial. By such effective coverage of bloom dynamics, combined with insights on environmental scenarios that promote the proliferation of certain taxa, public and private responses can be optimised. In a future scenario, this knowledge can be transferred to predictive models of HABs. In this sense, these future steps may advance towards preventive measures rather than mitigation actions to deal with this environmental hazard

MOLECULAR ECOLOGY OF MARINE ALGAL VIRUSES

In this study phytoplankton viruses were investigated from a point of view of their genotypic richness, ecology and role in controlling two microalgae species: Emiliania huxleyi and Phaeocystis pouchetii. Host specificity determined for Emiliania huxleyi-virus (EhV) isolates revealed a highly variable host range suggesting a relation between virus specificity and genetic or phenotypic variations within E. huxleyi strains and EhVs. Subsequently the dynamics and genetic richness of Emiliania huxleyi and EhVs were monitored in mesocosm experiments and during the progression of a natural bloom in the sea. The results confirmed the role of virus infection in regulating the intraspecific succession of E. huxleyi in the ocean. Furthermore, they revealed significant differences in genotypic composition and dynamics among blooms. The mesocosm setup appeared to be a very robust experimental system, which allowed reproducibility. The most important factor determining the development of the blooms in the enclosures was the experimental manipulation (i.e. nutrient addition), whereas the effect of filling of the enclosures, delay in nutrient addition and position in the raft were of minor importance. Further laboratory experiments revealed differences in the genomic content of different EhVs. EhV isolates from the English Channel carry a putative phosphate permease gene (ehv117) while the only available EhV from a Norwegian fjord has replaced ehv117 with a putative endonuclease, suggesting different propagation strategies among closely related EhVs. Culture studies using one of the English Channel isolates and E. huxleyi CCMP 1516 showed that the lack of phosphate (P) reduced the growth rate of the host and inhibited the production of viral particles. Furthermore, P availability was shown to have an effect on the level of ehv117 expression. In addition, other mesocosm studies revealed that specific viruses (PpVs) play a significant role in the termination of induced Phaeocystis pouchetii blooms. However, the role of PpVs may be significant only for the flagellated stage of P. pouchetii. Phenotypic characteristics of PpVs isolated during these studies indicate that they are probably members of the Phycodnaviridae family.The Marine Biological Association (UK), Plymouth Marine Laboratory (UK) and University of Bergen (Norway