Geschiktheid zeewindparken voor maricultuur en passieve visserij : een kwantitatieve beoordeling van de kansrijkheid van de gebieden voor de potentiële productiviteit van een selectie aan commercieel interessante soorten

In de Nederlandse Exclusieve Economische Zone (EEZ) zijn windparken gepland op diverse locaties. Door de windparken ontstaan nieuwe kansen voor multifunctioneel gebruik zoals maricultuur en niet-bodemberoerende visserij met passieve vistuigen. Deze studie brengt de potentiële - kwantitatieve - productiviteit van het kweken of vissen (passief vistuig) binnen bestaande, geplande en mogelijke toekomstige windparklocaties op de Noordzee in kaart voor een aantal vormen van medegebruik; kweek van bepaalde soorten zeewier en schelpdieren en de niet-bodemberoerende vangst van bepaalde soorten vissen, schaaldieren en inktvissen. Dit project is een vervolg op een voorgaand project waarbij een kwalitatieve beoordeling gegeven is van de kansrijkheid van de gebieden. In de huidige studie is voor een selectie van kansrijke soorten een berekening voor oogst of productie uitgevoerd. Daarnaast is dit rapport bedoeld om op basis van de huidige stand van kennis een inschatting te geven van de orde van grootte van het ruimtebeslag van zeewierproductie binnen toekomstige windparken. Met een aantal berekeningen wordt inzicht gegeven in de orde van grootte van opbrengsten, beschikbare/benodigde oppervlakten en benodigde nutriënten in de Noordzee. Op basis van deze analyse lijkt een areaal van enkele honderden km2 zeewierproductie realistisch, hierbij is uitgegaan van een grove indicatieve berekening, met diverse aannames. Op basis van de beschikbare voedingsstoffen voor mosselen zou tussen ca. 50 en 100 ton drooggewicht mosselen per km2 per jaar kunnen worden geproduceerd, waarbij de bronnen van onzekerheid in acht genomen dienen te worden. Om een indruk te krijgen van het (relatieve) voorkomen van vissen, weekdieren en schaaldieren is gebruik gemaakt van VMS- en logboekgegevens samen met gegevens van twee jaarlijkse surveys (BTS en IBTS). Het is echter niet mogelijk gebleken om voor alle geselecteerde soorten een kwantitatieve inschatting te maken, aangezien er nog weinig bekend is over ruimtelijke verdeling van deze soorten. Daarom is voor deze soorten een overzicht gegeven van wat er in de literatuur over bekend is

Geschiktheid zeewindparken voor maricultuur en passieve visserij : Een kwalitatieve beoordeling van geschiktheid van windparklocaties voor voedselproductie

In de Nederlandse Exclusieve Economische Zone (EEZ) zijn windparken gepland op diverse locaties. Door de windparken ontstaan nieuwe kansen voor multifunctioneel gebruik zoals maricultuur en nietbodemberoerende visserij met passieve vistuigen. Deze studie heeft de relatieve geschiktheid van bestaande, geplande en mogelijke toekomstige windparklocaties op de Noordzee in beeld gebracht voor een aantal vormen van medegebruik met betrekking tot een kweek van een aantal soorten schelpdieren en zeewier en niet-bodemberoerende vangst van een aantal soorten vissen, schaaldieren en weekdieren. Om de relatieve geschiktheid te beoordelen is eerst inzicht nodig waar de verschillende soorten voorkomen en welke condities voor een optimale leefsituatie zorgen. Dit leidt tot een kwalitatieve beoordeling van geschiktheid van (potentiële) windparklocaties voor voedselproductie (i.e. kweek of vangst van de betreffende soorten). De resultaten zijn weergegeven in kaarten per soort waardoor een inschatting gemaakt is van de geschiktheid van de verschillende locaties

Harmful algal blooms and their effects in coastal seas of Northern Europe

Highlights • Fish mortalities due to harmful algae cause substantial economic and social costs for the fish farming industry in the northeastern Atlantic, North Sea and adjacent European waters • Toxin syndromes associated with Diarrhetic Shellfish Toxins and Paralytic Shellfish Toxins and their regulation have the most profound effect on the bivalve aquaculture industry in the northeastern Atlantic region • Cyanobacteria and cyanotoxins are mainly problems in brackish water areas, particularly in the Baltic Sea • Emerging threats to the shellfish and finfish industries include the known presence of the phycotoxins azaspiracids and goniodomins • The IOC-ICES-PICESHAEDAT contains time-series baseline information on harmful algal events in EuropeHarmful algal blooms (HAB) are recurrent phenomena in northern Europe along the coasts of the Baltic Sea, Kattegat-Skagerrak, eastern North Sea, Norwegian Sea and the Barents Sea. These HABs have caused occasional massive losses for the aquaculture industry and have chronically affected socioeconomic interests in several ways. This status review gives an overview of historical HAB events and summarises reports to the Harmful Algae Event Database from 1986 to the end of year 2019 and observations made in long term monitoring programmes of potentially harmful phytoplankton and of phycotoxins in bivalve shellfish. Major HAB taxa causing fish mortalities in the region include blooms of the prymnesiophyte Chrysochromulina leadbeateri in northern Norway in 1991 and 2019, resulting in huge economic losses for fish farmers. A bloom of the prymesiophyte Prymnesium polylepis (syn. Chrysochromulina polylepis) in the Kattegat-Skagerrak in 1988 was ecosystem disruptive. Blooms of the prymnesiophyte Phaeocystis spp. have caused accumulations of foam on beaches in the southwestern North Sea and Wadden Sea coasts and shellfish mortality has been linked to their occurrence. Mortality of shellfish linked to HAB events has been observed in estuarine waters associated with influx of water from the southern North Sea. The first bloom of the dictyochophyte genus Pseudochattonella was observed in 1998, and since then such blooms have been observed in high cell densities in spring causing fish mortalities some years. Dinoflagellates, primarily Dinophysis spp., intermittently yield concentrations of Diarrhetic Shellfish Toxins (DST) in blue mussels, Mytilus edulis, above regulatory limits along the coasts of Norway, Denmark and the Swedish west coast. On average, DST levels in shellfish have decreased along the Swedish and Norwegian Skagerrak coasts since approximately 2006, coinciding with a decrease in the cell abundance of D. acuta. Among dinoflagellates, Alexandrium species are the major source of Paralytic Shellfish Toxins (PST) in the region. PST concentrations above regulatory levels were rare in the Skagerrak-Kattegat during the three decadal review period, but frequent and often abundant findings of Alexandrium resting cysts in surface sediments indicate a high potential risk for blooms. PST levels often above regulatory limits along the west coast of Norway are associated with A. catenella (ribotype Group 1) as the main toxin producer. Other Alexandrium species, such as A. ostenfeldii and A. minutum, are capable of producing PST among some populations but are usually not associated with PSP events in the region. The cell abundance of A. pseudogonyaulax, a producer of the ichthyotoxin goniodomin (GD), has increased in the Skagerrak-Kattegat since 2010, and may constitute an emerging threat. The dinoflagellate Azadinium spp. have been unequivocally linked to the presence of azaspiracid toxins (AZT) responsible for Azaspiracid Shellfish Poisoning (AZP) in northern Europe. These toxins were detected in bivalve shellfish at concentrations above regulatory limits for the first time in Norway in blue mussels in 2005 and in Sweden in blue mussels and oysters (Ostrea edulis and Crassostrea gigas) in 2018. Certain members of the diatom genus Pseudo-nitzschia produce the neurotoxin domoic acid and analogs known as Amnesic Shellfish Toxins (AST). Blooms of Pseudo-nitzschia were common in the North Sea and the Skagerrak-Kattegat, but levels of AST in bivalve shellfish were rarely above regulatory limits during the review period. Summer cyanobacteria blooms in the Baltic Sea are a concern mainly for tourism by causing massive fouling of bathing water and beaches. Some of the cyanobacteria produce toxins, e.g. Nodularia spumigena, producer of nodularin, which may be a human health problem and cause occasional dog mortalities. Coastal and shelf sea regions in northern Europe provide a key supply of seafood, socioeconomic well-being and ecosystem services. Increasing anthropogenic influence and climate change create environmental stressors causing shifts in the biogeography and intensity of HABs. Continued monitoring of HAB and phycotoxins and the operation of historical databases such as HAEDAT provide not only an ongoing status report but also provide a way to interpret causes and mechanisms of HABs

Marine Toxins: Chemistry, Toxicity, Occurrence and Detection, with Special Reference to the Dutch Situation

Various species of algae can produce marine toxins under certain circumstances. These toxins can then accumulate in shellfish such as mussels, oysters and scallops. When these contaminated shellfish species are consumed severe intoxication can occur. The different types of syndromes that can occur after consumption of contaminated shellfish, the corresponding toxins and relevant legislation are discussed in this review. Amnesic Shellfish Poisoning (ASP), Paralytic Shellfish Poisoning (PSP), Diarrheic Shellfish Poisoning (DSP) and Azaspiracid Shellfish Poisoning (AZP) occur worldwide, Neurologic Shellfish Poisoning (NSP) is mainly limited to the USA and New Zealand while the toxins causing DSP and AZP occur most frequently in Europe. The latter two toxin groups are fat-soluble and can therefore also be classified as lipophilic marine toxins. A detailed overview of the official analytical methods used in the EU (mouse or rat bioassay) and the recently developed alternative methods for the lipophilic marine toxins is given. These alternative methods are based on functional assays, biochemical assays and chemical methods. From the literature it is clear that chemical methods offer the best potential to replace the animal tests that are still legislated worldwide. Finally, an overview is given of the situation of marine toxins in The Netherlands. The rat bioassay has been used for monitoring DSP and AZP toxins in The Netherlands since the 1970s. Nowadays, a combination of a chemical method and the rat bioassay is often used. In The Netherlands toxic events are mainly caused by DSP toxins, which have been found in Dutch shellfish for the first time in 1961, and have reoccurred at irregular intervals and in varying concentrations. From this review it is clear that considerable effort is being undertaken by various research groups to phase out the animal tests that are still used for the official routine monitoring programs

Sonar 2021-2022 field experiment method development : a case-study of seaweed cultivation and biomass estimation using different sonar techniques and image recognizing networks

Seaweed is increasingly becoming a crop of interest in aquaculture. Seaweed has potential as a low trophic food source as no fresh water or fertiliser is needed for its growth. However, to start a profitable business in seaweed farming in the North Sea, space is required. Besides that, offshore seaweed farming is met with numerous technical challenges in this sometimes-turbulent environment. To monitor the crop farmers can make use of the latest technology in remote sensing. Potential remote sensing technologies, which could be used in seaweed farming, were identified in 2020. The use of the DIDSON sonar was thought in advance to make the most useful underwater images of the seaweed Saccharina latissima in a test farm in the Oosterschelde. Were in 2020 the first preliminary images were made with the DIDSON. In 2021 the DIDSON was used to make images in the seaweed test farm, in combination with using Humminbird sonar (Helix 12, MSI/GPS G3N). In situ, it was found that handling the DIDSON while in a small boat was a difficult task. Because of movement of the sonar, it was difficult to make sharp images. The DIDSON again did not yield a lot of useful images. However fully convolutional neural network models for image recognition were tested using images from both years. The Humminbird fish finder was not successful in taking any images of seaweed in 2021, though the mussel lines in the same farm could be detected. In 2022 the last sampling was done again using both sonars. This time using different settings, the Humminbird was able to detect the seaweed in the lines in the farm. The images that the Humminbird yielded had a better resolution and quality than those of the DIDSON from the previous years. This data could be used on further expanded neural networks. The images of the Humminbird were used in a classical approach for segmenting in the neural network and showed promise for future use. However the data had a lot of limitation and in follow up studies multiple lines should be measured using the Humminbird sonar. For the deep learning architecture, to further expand the neural network a larger test dataset is needed. Besides the neural network, the biomass of the seaweed was also measured and samples were taken to the institute to measure length and surface area. However there didn’t seem to be a clear correlation between seaweed length and biomass. To be able to estimate biomass from sonar images sufficient biomass measurements need to be made to determine the correlation, before accurate biomass predictions can be made using the segmentation in the neural network

Combining offshore wind farms, nature conservation and seafood : Lessons from a Dutch community of practice

Large-scale development of offshore wind farms implies an increase in marine resource use conflicts. Managing potential impacts on marine ecosystems and on resource access for traditional and prospective users is key. Multi-use scenarios are a solution but are often approached as a 'design question' that can be settled through Marine Spatial Planning. In practice, regulatory, technical and socio-economic factors often hinder multi-use. Overcoming such barriers requires active collaboration between all stakeholders, yet meaningful participation in MSP processes often is a challenge. This paper explores the role of Communities of Practice as a participatory tool for developing multi-use. The Netherlands set up a ‘Community of Practice North Sea’ to stimulate the development of multi-use pilots by bringing interested parties together, sharing experiences and learning from each other in a context of existing and developing spatial and social claims. This development is part of the government's strategy aimed at finding a balance between offshore wind energy development, nature conservation and seafood production. The paper shows that by (partly) decoupling policy from practice and creating a positive learning environment, Communities of Practice have potential as a participatory tool for encouraging cooperation between stakeholders in an informal setting and facilitating a transition towards multi-use of marine resources. The paper proposes ten guidelines for using Communities of Practices as an action-oriented tool for salient multi-use practices.</p

Capturing complex ecosystem services evaluation with rubrics : A case-study of seaweed cultivation

With the growing ambitions of implementing low trophic aquaculture, a framework for cohesive and balanced assessment of effects resulting from seaweed cultivation was performed for a hypothetical case study in 2021. As, traditionally, such assessments tend to focus on the negative impacts, it was recommended to also assess the benefits from seaweed cultivation. The concept of ‘Ecosystem services’ (ES) is a sensible construct to express such benefits, as it focuses on the benefits supplied by the ecosystem. The goal of the present study is investigating how these ecosystem services can be included in the comprehensive framework developed last year for a seaweed cultivation case. In order to achieve this, we specifically looked at the project design process, how to map the project needs and how to select or develop the instruments to meet those needs. Roughly, three phases can be distinguished in the study design process: the ideal design phase, where the project specifications required to fulfil the goal of an assessment are defined to ensure the most comprehensive assessment; the realistic design phase, where one performs a reality check on the ideal design, where practical issues, technical issues and resource availability are considered; and finally an adaptive phase: the phase where modifications are made resulting from new insights. In order to facilitate the study design process we developed and applied a so-called ‘rubric’ tool. This rubric is a questionnaire that scores a wide range of elements that are relevant when evaluating ecosystem services for one or more activities (such as seaweed cultivation). This questionnaire considers and addresses elements of ecosystem services impact assessments grouped in the following three aspects: - Which elements are relevant and considered for the study? -What level of detail is required (for these elements)? -How to quantify ES and process the data?. Each sub-question in the rubric is answered with a score between 0 and 5 (where the scale is arbitrary). In the present study, the questionnaire is applied to the case-study goals. But also two contrasting strategies (i.e. application of top-down versus bottom-up methodologies) are included as examples and are evaluated with the rubric for suitability. The top-down strategy uses an existing framework from the EU project Aquacross, which was also used last year to address seaweed cultivation impacts. This framework uses linear cause-effect chains where effects on the ecosystem components are linked to the capacity to supply ecosystem services. The bottom-up methodology is formulated from scratch. It focuses more on the desired outcome, and more attention is paid to benefits resulting from the activities (rather than impacts). Feedback mechanisms are also considered. It should be noted that both methodologies are only available as concepts and are not yet operational. By applying the rubric to both set case-study goals (including ecosystem services in an assessment of the effects from seaweed cultivation) and the proposed methodologies, both results could be compared. It is shown that neither of the two strategies have a 100% match with the case-study goals. This means that neither methodology is preferable at the moment. Also, this means that the methodologies need to be adjusted or the case-study goals need to be revised. In order to make informed decisions on how to proceed in this process a final piece of the puzzle is still missing, which unfortunately is beyond the scope of the present study. - The missing puzzle piece is ‘consequences’. The rubric approach had helped in structuring the project design phase and support underpinning discussions. It made insightful what the study intentions are, and what the proposed methodologies can and cannot offer. It also shows that there is a mismatch between the ideal design and the realistic design. In order to decide which changes (in either case- study goals or strategies to include ecosystem services) are necessary, it is required to know the consequences of these decisions. Several recommendations are made to generalize the assessment of these consequences by linking case-study goals to requirements and their feasibility. This is not further developed in the present study. In conclusion, the rubric approach can be used to score the capacity and limitations of methodological strategy (such as the top-down and bottom-up strategy evaluated here) on one hand and the improve specifications of requirements for a specific case or project on the other hand. As such the approach can be used to evaluate different methodologies, to determine which strategy is most suitable for a specific research question. The approach can also be used to refine research questions or identifying knowledge and data gaps in an early stage of a project. In addition, the approach can be used iteratively during a project execution to manage and adjust the project requirements (and indirectly stakeholder expectations of the project). As such the approach is suitable in each of the three identified study design phases (targeted design, realistic design, adaptive design). In its current form the rubric approach shows promise, but is not yet able to fully support study design choices for evaluating ecosystem services from the seaweed cultivation case from Tonk et al. (2021). For that purpose the approach needs to be extended such that it addresses consequences of design choices, for which recommendations are made

First Report on the Occurrence of Tetrodotoxins in Bivalve Mollusks in The Netherlands

Tetrodotoxin (TTX) is traditionally associated with seafood from tropical regions, but recently TTX was detected in bivalve mollusks in more temperate European waters. In The Netherlands it was therefore decided to monitor TTX in shellfish harvested from Dutch production areas. All shellfish production areas were monitored in 2015, 2016 and 2017. Samples were analyzed using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). In total 1063 samples were investigated, and the highest concentrations were observed in 2016, i.e., 253 g TTX/kg in oysters and 101 g TTX/kg in mussels. No TTX analogues, with the exception of 4-epi-TTX in one single sample, were found and contaminated samples also showed positive results in the neuro-2a bioassay. The occurrence of TTX seems to be consistent over the last three years with the highest concentrations observed annually in late June. The causative organism and the reasons why specific Dutch production areas are affected while others are not, are still unclear. Initially in The Netherlands an action limit of 20 g TTX/kg was used to ensure the safety of consumers (2016), but recentlyThe European Food Safety Authority (EFSA) established an acute reference dose, and based on a high portion size of consuming 400 g mussels, this dose was translated into a safe concentration of 44 g TTX per kg for shellfish. This concentration is now used as an action limit and TTX is formally included in the Dutch shellfish monitoring program

Immunomodulatory Effects of Dietary Seaweeds in LPS Challenged Atlantic Salmon Salmo salar as Determined by Deep RNA Sequencing of the Head Kidney Transcriptome

Seaweeds may represent immuno-stimulants that could be used as health-promoting fish feed components. This study was performed to gain insights into the immunomodulatory effects of dietary seaweeds in Atlantic salmon. Specifically tested were 10% inclusion levels of Laminaria digitata (SW1) and a commercial blend of seaweeds (Oceanfeed®) (SW2) against a fishmeal based control diet (FMC). Differences between groups were assessed in growth, feed conversion ratio and blood parameters hematocrit and hemoglobin. After a LPS challenge of fish representing each of the three groups, RNAseq was performed on the head kidney as major immune organ to determine transcriptomic differences in response to the immune activation. Atlantic salmon fed with dietary seaweeds did not show major differences in performance in comparison with fishmeal fed fish. RNAseq resulted in ∼154 million reads which were mapped against a NCBI Salmo salar reference and against a de novo assembled S. salar reference for analyses of expression of immune genes and ontology of immune processes among the 87,600 cDNA contigs. The dietary seaweeds provoked a more efficient immune response which involved more efficient identification of the infection site, and processing and presentation of antigens. More specifically, chemotaxis and the chemokine-mediated signaling were improved and therewith the defense response to Gram-positive bacterium reduced. Specific Laminaria digitata effects included reduction of the interferon-gamma-mediated signaling. Highly upregulated and specific for this diet was the expression of major histocompatibility complex class I-related gene protein. The commercial blend of seaweeds caused more differential expression than Laminaria digitata and improved immune processes such as receptor-mediated endocytosis and cell adhesion, and increased the expression of genes involved in response to lipopolysaccharide and inflammatory response. Particularly, expression of many important immune receptors was up-regulated illustrating increased responsiveness. NF-kappa-B inhibitor alpha is an important gene that marked the difference between both seaweed diets as Laminaria digitata inhibits the expression for this cytokine while the blend of seaweeds stimulates it. It can be concluded that the inclusion of seaweeds such as Laminaria digitata can have important modulatory effects on the immune capacity of Atlantic salmon resulting in a more efficient immune response

Immunomodulatory Effects of Dietary Seaweeds in LPS Challenged Atlantic Salmon Salmo salar as Determined by Deep RNA Sequencing of the Head Kidney Transcriptome

Seaweeds may represent immuno-stimulants that could be used as health-promoting fish feed components. This study was performed to gain insights into the immunomodulatory effects of dietary seaweeds in Atlantic salmon. Specifically tested were 10% inclusion levels of Laminaria digitata (SW1) and a commercial blend of seaweeds (Oceanfeed®) (SW2) against a fishmeal based control diet (FMC). Differences between groups were assessed in growth, feed conversion ratio and blood parameters hematocrit and hemoglobin. After a LPS challenge of fish representing each of the three groups, RNAseq was performed on the head kidney as major immune organ to determine transcriptomic differences in response to the immune activation. Atlantic salmon fed with dietary seaweeds did not show major differences in performance in comparison with fishmeal fed fish. RNAseq resulted in ∼154 million reads which were mapped against a NCBI Salmo salar reference and against a de novo assembled S. salar reference for analyses of expression of immune genes and ontology of immune processes among the 87,600 cDNA contigs. The dietary seaweeds provoked a more efficient immune response which involved more efficient identification of the infection site, and processing and presentation of antigens. More specifically, chemotaxis and the chemokine-mediated signaling were improved and therewith the defense response to Gram-positive bacterium reduced. Specific Laminaria digitata effects included reduction of the interferon-gamma-mediated signaling. Highly upregulated and specific for this diet was the expression of major histocompatibility complex class I-related gene protein. The commercial blend of seaweeds caused more differential expression than Laminaria digitata and improved immune processes such as receptor-mediated endocytosis and cell adhesion, and increased the expression of genes involved in response to lipopolysaccharide and inflammatory response. Particularly, expression of many important immune receptors was up-regulated illustrating increased responsiveness. NF-kappa-B inhibitor alpha is an important gene that marked the difference between both seaweed diets as Laminaria digitata inhibits the expression for this cytokine while the blend of seaweeds stimulates it. It can be concluded that the inclusion of seaweeds such as Laminaria digitata can have important modulatory effects on the immune capacity of Atlantic salmon resulting in a more efficient immune response