Deep-water Sites Research Articles

Application of systems safety principles for O&M of floating offshore wind

Abstract The offshore wind industry is growing rapidly and is also a high risk industry with unique safety challenges. As the industry grows, more research is needed to make sure it operates safely and provides a workplace in which all involved can go home free of injury. The adoption of floating wind turbines brings new hazards and increased complexity to offshore wind operations and maintenance. Floating wind operations will involve the development of new deepwater sites and require the adoption of new strategies such as floating to floating transfers and towing operations. As the complexity of offshore operations increases it is important that the understanding of the hazards involved are developed. Floating wind is a new branch of the offshore wind industry and as technologies and systems have yet to become established there is the opportunity to do things differently and embed safety improvements in the industry from the outset. This study has looked at the potential application of systems safety theories to floating wind operations and maintenance. The application of systems engineering to improve safety performance has been growing across many industries in recent years. Systems safety considers that safety is an emergent property of a complex system that is a result of many interacting factors. This study looks at how systems safety could be applied to the emerging floating wind industry to build safety into the industry at the earliest stages. This study reviewed the applications of systems safety across similar industries and the offshore wind industry. It then looks at existing hazards of floating wind that have already been identified in the literature and completed a systems theory hazard analysis of floating wind O&M activities. This involved the mapping of the safety control structure for floating wind operations and the identification of potential gaps between the safety controls and safety requirements. It then explores how systems safety processes could be applied to floating wind and makes recommendations for how these could be implemented to the emergent industry. The study found existing research of systems safety applied to the offshore wind industry is currently very limited. Its application has been successful in similar industries and there is potential for a systems safety approach to be used in the development of floating wind operations and maintenance. The systems theory hazard analysis can help identify potential systemic risks arising as a result of the interaction of multiple systems. It can be used to develop appropriate control structures to manage safety and could also be used for the identification of leading indicators to manage safety performance.

IEA Wind Task 49: Reference Site Conditions for Floating Wind Arrays

Abstract The commercial-scale deployment of floating offshore wind (FOW) projects is expected to take place in a diverse range of sites that may differ significantly from existing fixed-bottom projects. FOW farms are particularly sensitive to the water depth and the meteorological and oceanographic (metocean) and geotechnical conditions at the project site due to the wave-induced system motions and loads as well as the anchoring system constraints imposed by the seafloor conditions. Uncertainty around the site conditions will permeate through all aspects of project design, leading to suboptimal and overly conservative designs, increased costs, and adversely affected performance. As FOW expands into a global industry, metocean and geotechnical conditions will increasingly vary for projects located in different geographic regions or in far-from-shore, deep-water sites. This study represents the outputs of work package 1 of International Energy Agency Wind Task 49, which focuses on the integrated design of floating wind arrays. The primary goal of this study is to establish the type of parameters and constraints required to characterize FOW array reference sites; provide a realistic and publicly available set of reference site conditions to the FOW community as a baseline set of data for individual research projects; identify and categorize any critical gaps in the existing data or methodologies required to define reference site characteristics; and inform and support the design of reference FOW arrays. A building block concept was developed for synthesizing reference sites for the design of FOW arrays. The building blocks include three classes of site conditions focusing on the techno-economic design of FOW projects: metocean conditions, seabed conditions, and coastal infrastructure. All reference site data produced and collected in this study are publicly available.

Energy density source levels of underwater explosive charges

This paper presents experimental measurements of energy density source levels of small explosive charges for high frequencies to 18 kHz. The experiments were carried out using Signals Underwater Sound (SUS) charges deployed at a deep water site in a coastal fiord north of Vancouver BC. The waveform of an underwater explosion is characterized by a high intensity shock wave signal followed by a series of bubble pulses of decreasing intensity. The bubble pulses dominate the SUS energy density spectrum at frequencies below 1 kHz, but at higher frequencies the spectrum is dominated by the characteristics of the decay envelope of the shock wave signal. The explosive material in SUS charges is packed in a thin cylindrical cavity, resulting in a non-uniform decay envelope with secondary pulses when detonated, and a non-spherical distribution of the radiated sound. The impact of the cylindrical charge shape on energy density source level was investigated experimentally. Data were recorded for SUS deployments that generated in-line and broadside sound propagation to the receiver with respect to the axis of the cylindrical charge. Experimental measurements indicate significant differences in the high frequency SUS energy density spectrum depending upon the SUS and receiver geometry.

IBLUECULTURE: A NOVEL SYSTEM OF REAL-TIME UNDERWATER IMAGE TRANSMISSION IN A VIRTUAL REALITY ENVIRONMENT, AS A NEW MANAGERIAL APPROACH FOR UNDERWATER CULTURAL HERITAGE

Abstract. The Mediterranean is rich in ancient and modern shipwrecks and submerged sites of great archaeological, historical, and cultural value. Most of those sites tend to be relatively unknown, even to people living in the area, mostly due to the inherent limitation in physical approach. As a result, these sites are left unknown and unprotected. The aim of the iblueCulture project was to create a system that can make Underwater Cultural Heritage sites broadly accessible and raise public awareness on their location, content, and value. This approach is also meant to provide an effective management strategy for the constant, real-time monitoring and, therefore, protection of such sites, while in accordance with the sustainable tourism development goals for islands and coastal areas. This project, as implemented, can offer an immersive dry dive experience to the public, while providing management bodies and stakeholders with the capability of remotely monitoring the UCH sites in real-time, through live-streaming video. This ability can be vital in some cases, especially when involving sites in greater depths or in remote areas with little maritime traffic. The system is also expected to assist in underwater research, especially in deep water sites, and other educational activities or possible scientific research.

Occurrence and Sources of Polycyclic Aromatic Hydrocarbons and Factors Influencing Their Accumulation in Surface Sediment of a Deep-Sea Depression, Namely, the Tatar Trough (Tatar Strait, the Sea of Japan)

The concentrations of 14 polycyclic aromatic hydrocarbons (PAHs) in the sediment of the Tatar Trough were studied. Despite the increase in PAH concentrations over recent decades, which is likely the result of the handling and transportation of fossil fuels, PAH levels and ecological risk were found to be low. The spatial pattern revealed that higher PAH concentrations were mainly in the deeper water sites, suggesting that trough slope failure transported the PAHs to the deeper part of the basin. There was no correlation between the PAHs and grain size or the PAHs and organic carbon that is related to the PAH input from a variety of sources and the heterogeneity of organic matter. The PAH composition, isomer ratio, and PCA identified two areas with different PAH sources. The most northern part of the Tatar Trough received petrogenic PAHs that are probably transported downslope from the northern Tatar Strait where fossil fuels are handled in some ports. Another trough part was polluted by the PAHs from the combustion of coal and biomass and the exhaust of marine vehicles. The minor presence of genes responsible for aerobic PAH destruction can be explained by the anaerobic degradation of PAHs or the spontaneous creation of favorable conditions that promote bacterial PAH oxidation.

Escape gaps in wire lobster traps reduce bycatch of coral reef fish while maintaining catch of harvestable lobsters in Florida’s Caribbean spiny lobster (Panulirus argus), fishery

Escape gaps are a tool commonly used to reduce the catch of sublegal-size animals and bycatch in crustacean trap fisheries. In Florida’s Caribbean spiny lobster (Panulirus argus) commercial trap fishery, traps are baited with live, sublegal-size lobsters, which precludes the use of escape gaps sized to exclude capture of undersize lobsters. Both wood and wire traps are used in the fishery, but wire traps capture more fish as bycatch than do wood traps. This project was developed and executed cooperatively with commercial fishers to evaluate, for wire lobster traps, the effect of escape gaps on catch rates of bycatch and harvestable lobsters. We tested five wire-trap configurations that included a control trap without escape gaps (i.e., an unmodified commercial trap) and four configurations consisting of a narrow (3.81 cm) or wide (5.40 cm) escape gap, oriented either vertically or horizontally. All traps were fished in the Atlantic Ocean at a deepwater site (ca. 30 m) and a shallow-water (ca. 10 m) site. Control traps and traps with a narrow escape-gap configuration were baited with a live, sublegal-size lobster; traps with a wide escape-gap configuration were baited with a live, legal-size lobster. We compared the number of lobsters caught and coral reef fish bycatch, as well as size frequency distributions of lobster and compressiform fish species, which include fish in the snapper and grouper families, in each trap configuration. Escape-gap traps caught statistically similar numbers of legal-size lobsters in all configurations except the wide horizontal configuration at the deep site. The catch of sublegal-size lobsters was significantly reduced in the wide horizontal and wide vertical escape-gap trap configurations at both sites. Fish bycatch was dominated by compressiform fish of the Haemulidae family and fish bycatch was significantly reduced in all escape-gap trap configurations. Our results suggest that the wide vertical escape-gap configuration maximized both the retention of harvestable lobsters and the escape of sublegal-size lobsters and fish bycatch. Inclusion of any of the escape-gap configurations tested could reduce discard mortality of fish and undersize lobsters, but baiting and trap fishing methods may need to be adjusted to maximize lobster harvest.

Design and costs benefits of shared anchors and shared mooring lines of floating wind turbines at farm level

This paper focuses on innovative mooring layouts using shared anchors and shared mooring lines. Three studies with the ActiveFloat semi-submersible floater supporting a 15MW wind turbine are presented. Those include two studies of shared anchors layouts, with a semi-taut mooring system at a deep-water site subjected to extreme conditions (Morro Bay) and a catenary mooring at a moderate water depth with gentle environment (Gran Canaria). The third study focuses on shared mooring layout at Morro Bay. The mooring system at this site is semi-taut, made of polyester, with chain close to the sea surface and the anchors. At Gran Canaria, ActiveFloat is featured with a catenary mooring system made of chain lines. Both sites are subjected to irregular sea states and turbulent wind. Time domain simulations in ULS are performed using OrcaFlex models that combine potential flow theory and Morison drag coefficients. Aerodynamic load time series are applied at the tower top. Results show that shared anchor layouts are technically feasible but do not improve the mooring system procurement costs due to the spacing constraint between each turbine. Sharing mooring lines at farm level seems more promising and could help reduce costs, due to the decrease in amount of material use.

Quantifying the surge-induced response of a floating tidal stream turbine under wave-current flows

Understanding the impact of dynamic effects induced by wave-current conditions on the hydrodynamic performance of a floating horizontal axis tidal turbine (HATT) is crucial toward developing floating tidal turbines to harness tidal energy in deep water sites. The complicated of the wake of a HATT has not yet been fully understood. In this paper, a Computational Fluid Dynamics (CFD) model used to study the performance of a turbine supported by a moored floating platform, due to surge only and in wave-current flows. The CFD model is compared against piled turbine tests, providing an error of 1.36% in power coefficients at the studied TSR = 3.9. It was shown that surge motion caused by even a small wave height or wavelength has a significant effect on the thrust and torque of the rotor. The wave height and period have a remarkable effect on the fluctuation of the hydrodynamic performance due to the induced rotor velocity. The surge motion affects the wake velocity recovery and vortex structure development. For a fuller understanding, future work could explore the negative effects such as induced blade fatigue and platform instability arising from surge motion, as to design cost-efficient turbines, supports and arrangements.

An expanded database of Southern Hemisphere surface sediment dinoflagellate cyst assemblages and their oceanographic affinities

Abstract. Dinoflagellate cyst assemblages present a valuable proxy to infer paleoceanographic conditions, yet factors influencing geographic distributions of species remain largely unknown, especially in the Southern Ocean. Strong lateral transport, sea-ice dynamics, and a sparse and uneven geographic distribution of surface sediment samples have limited the use of dinocyst assemblages as a quantitative proxy for paleo-environmental conditions such as sea surface temperature (SST), nutrient concentrations, salinity, and sea ice (presence). In this study we present a new set of surface sediment samples (n=66) from around Antarctica, doubling the number of Antarctic-proximal samples to 100 (dataset wsi_100) and increasing the total number of Southern Hemisphere samples to 655 (dataset sh_655). Additionally, we use modelled ocean conditions and apply Lagrangian techniques to all Southern Hemisphere sample stations to quantify and evaluate the influence of lateral transport on the sinking trajectory of microplankton and, with that, to the inferred ocean conditions. k-means cluster analysis on the wsi_100 dataset demonstrates the strong affinity of Selenopemphix antarctica with sea-ice presence and of Islandinium spp. with low-salinity conditions. For the entire Southern Hemisphere, the k-means cluster analysis identifies nine clusters with a characteristic assemblage. In most clusters a single dinocyst species dominates the assemblage. These clusters correspond to well-defined oceanic conditions in specific Southern Ocean zones or along the ocean fronts. We find that, when lateral transport is predominantly zonal, the environmental parameters inferred from the sea floor assemblages mostly correspond to those of the overlying ocean surface. In this case, the transport factor can thus be neglected and will not represent a bias in the reconstructions. Yet, for some individual sites, e.g. deep-water sites or sites under strong-current regimes, lateral transport can play a large role. The results of our study further constrain environmental conditions represented by dinocyst assemblages and the location of Southern Ocean frontal systems.

Ecological Basis of Ecosystem Services and Management of Wetlands Dominated by Common Reed (Phragmites australis): European Perspective

The common reed (Phragmites australis) is a frequent dominant species in European wetlands. Yet, its performance can vary in response to different combinations of environmental factors. This accounts for P. australis decline on deep-water sites, its stable performance in constructed wetlands with subsurface horizontal flow and its expansion in wet meadows. Reed stands provide habitats for nesting, feeding or roosting of vulnerable bird species. Conservation measures aim at preventing or stopping the decline of P. australis stands, increasing their micro-habitat heterogeneity and reducing the reed penetration into wet meadows. Service-oriented measures aim at providing suitable conditions for direct use of reed stalks for roof thatching or as a renewable energy crop or the use of the reed-dominated habitats for waterfowl hunting, cattle grazing or fishing. The compatibility between nature conservation and different socioeconomic uses can be promoted by collective agreements, agri-environmental contracts or payments for ecosystem services of the reedbeds. In situations with multiple uses, a modelling approach considering the participation of all the stakeholders concerned can be a useful tool for resolving conflicts and developing a shared vision of the respective socio-ecosystem.

HYDROCHEMICAL STUDIES OF THE TROUT FARMING AREA IN KONDOPOGA BAY OF LAKE ONEGO IN THE WINTER OF 2022

Hydrochemical studies of the trout farming area in Kondopoga Bay of Lake Onego were carried out in the winter of 2022. Surveys at the deep-water site near the cages revealed dissolved oxygen starvation (0.8 mg/l) and a high content of ammonium (0.410 mg N/l) and mineral phosphorus (787 μg P/l, or 97 % of total phosphorus) in the near bottom level, which is comparable to wastewater from the Kondopoga pulp-and-paper mill. At other sites located in the trout farming area and at K50 located in the zone affected by Kondopoga PPM wastewater, which spreads over the bottom of the bay in winter, the dissolved oxygen content varied from 6.8 to 13.1 mg/l, the concentrations of NH4 + (up to 0.068 mg N/l) and Pmin (up to 51 μg P/l) were significantly lower than near the cages. Our data indicate the trout farms have a significant effect on the water chemical composition, confirmed by a previously detected long-term trend for an increase in TP content and intensive growth of phytoplankton in the central part of Kondopoga Bay.

Baseline levels and characterization of hydrocarbons in surface marine sediments along the transportation corridor in Hudson Bay: A multivariate analysis of n-alkanes, PAHs and biomarkers

Hudson Bay is a small arctic inland shelf sea which receives large amounts of freshwater from riverine discharges, with marine flow from the north and the Atlantic. A warming climate has resulted in an expanded open water season which will result in an increase in shipping of fuel oil and petroleum to communities and mines on the western shore, increasing the risk of hydrocarbon releases. To evaluate the status of hydrocarbons, surface sediments were collected at 34 locations in the transportation route and offshore and analysed for several types of hydrocarbons. Total hydrocarbons varied by over 25 times between sites, reaching a maximum of 1116 μg/g OC (organic carbon basis) in Hudson Strait due to low molecular weight n-alkanes from marine primary production. The gross mean for all sites was 344 μg/g OC (GSD = 173–682), roughly equivalent to other remote sites in the Canadian Arctic with no known local hydrocarbon source. n-alkanes accounted for >90 % of residues. Diagnostic ratios (e.g., Carbon Preference Index (CPI), Odd-Even Predominance (OEP)) indicated mixed sources of n-alkanes, likely due to the input from vascular plants and ombrotrophic peat in northern and western watersheds, and primary production within the Bay. The elevated proportion of high molecular weight n-alkanes at deep water sites is consistent with lotic particulate organic matter deposited in the nearshore environment and redeposited offshore. Ʃ36PAHs were a small fraction (1.9 %) of hydrocarbons, with a gross mean of 5.68 μg/g OC (GSD = 3.30–9.79). PCA separated deep water sediments from nearshore and community samples due to 4 alkylated naphthalenes which usually indicate a petrogenic source but probably indicates a natural source due to the lack of other petrogenic markers. Priority PAHs (i.e., Ʃ16PAH) varied from 31.5 % to 56.6 % of the Ʃ36PAH residues. The concentrations of individual PAHs were well below the Interim Sediment Quality Guidelines recommended by the Canadian Council of Ministers of the Environment.

Seasonal Movements and Spatial Overlap of Juvenile and Adult Lake Sturgeon in Lake Champlain

AbstractThe lake sturgeon Acipenser fulvescens is a large, long‐lived, potamodromous species that is widely distributed throughout freshwater systems in the central part of North America. In this study, we used acoustic telemetry to examine seasonal distribution and movement patterns of endangered Lake Sturgeon in Lake Champlain, Vermont. Acoustic tags were implanted in 29 juvenile Lake Sturgeon (453–874 mm TL) and 19 adults (1,215–1,615 mm TL) from the Winooski River and nearby areas of Lake Champlain between 2015 and 2019; tags were detected with 23 passive acoustic receivers deployed in the river and delta area and an additional 34 receivers deployed throughout Lake Champlain. Home range analysis using a lattice‐based density estimator indicated that juvenile home range sizes were the same as adult home range sizes in spring and summer but were statistically larger than adult home ranges in winter. Cumulative home range analysis showed that juvenile and adult home ranges overlapped in shallow (<10‐m) water in the summer and fall. In winter and spring, cumulative home ranges from juveniles included deepwater sites (>25 m), while adults remained in shallow water near the mouth of their spawning river. Seven juveniles made long‐range movements (18–34 km) during the winter and spring months, and 13 juveniles moved back into the lower section of their natal river after overwintering in Lake Champlain. This study is the first to directly compare adult and juvenile Lake Sturgeon distribution, home range size, movements, and habitat use in a large lake system and provides a baseline for further research on the movement ecology of Lake Sturgeon in Lake Champlain.

Dynamics of two floating wind turbines with shared anchor and mooring lines

Floating wind farms present the opportunity to harvest wind resources located in deep water sites. Shared mooring designs can contribute in making floating wind energy more cost-competitive, and it is important to understand the new system dynamics that arise. We are presenting here HAWC2Farm, an extension of HAWC2 that can model multiple wind turbines with shared mooring lines. We apply the new modeling capabilities to simulate two 15 MW floating wind turbines on spar floaters with shared mooring lines. We consider two different sites and we identify and compare the natural frequencies and mode shapes of the shared mooring designs with those of an individual moored turbine. Furthermore, we investigate the influence of design parameters on the systems’ natural frequencies and we show that it is possible for a shared mooring design to achieve similar characteristics as a single turbine design. Finally, we test the response of the shared mooring design in steady wind and regular waves and find that the surge displacement of the upstream turbine and its mooring line loads are considerably larger compared to the single turbine case.

Annual, seasonal, and diel patterns in blue whale call occurrence off eastern Canada

Little is known about the year-round occurrence of blue whales in Atlantic Canadian waters. We used passive acoustic monitoring to investigate blue whale call presence and increase our understanding of year-round blue whale occurrence along the eastern edge of the Scotian Shelf, Nova Scotia, Canada. Blue whale calls were recorded at 3 deep water sites within and near the Gully Marine Protected Area from October 2012 to September 2014 using bottom-mounted passive acoustic recorders. Calls were categorized as either tonal or downsweeping. At all 3 sites, tonal calls occurred most often from November through January in both years and in August 2014, while the majority of downsweeping calls occurred during May through September 2014. There was no discernible diel pattern in the occurrence of tonal calls. Downsweeping calls occurred most often during evening twilight, with a dramatic peak in occurrence during the hour of 19:00 Atlantic Standard Time at all 3 sites. The peak in downsweeping call occurrence during evening twilight may have been related to blue whale foraging ecology. This study sheds light on the poorly understood year-round occurrence of blue whales off Atlantic Canada. Understanding when and where blue whales occur will help to inform management decisions for the protection and conservation of this endangered population.

Development of jacket substructure systems supporting 3MW offshore wind turbine for deep water sites in South Korea

This study aims to develop jacket substructures supporting a 3MW Offshore Wind Turbine (OWT) in water depth ranges of 25–40 m. A simplified structural design process is introduced and influences of jacket topological forms and brace systems on their dynamic performances are assessed. The results conclude that the topological configuration of the jacket substructure has a significant influence on the dynamic characteristics of the whole system, indicating a high priority when designing a jacket substructure for OWTs. Furthermore, two jacket substructures having the lowest material costs and the best performances under the Korean ocean environmental conditions are suggested. Additionally investigated in this study is a sensitivity of environmental loading directions on the structural performances of the jacket substructures. All the findings in this study might be very useful to assist the structural engineers when they design the support structures for large-scaled OWTs in the near future in South Korea.

Reconstruction of the Long-Term Dynamics of Particulate Concentrations and Solid–Liquid Distribution of Radiocesium in Three Severely Contaminated Water Bodies of the Chernobyl Exclusion Zone Based on Current Depth Distribution in Bottom Sediments

Given the importance of understanding long-term dynamics of radionuclides in the environment in general, and major gaps in the knowledge of 137Cs particulate forms in Chernobyl exclusion zone water bodies, three heavily contaminated water bodies (Lakes Glubokoe, Azbuchin, and Chernobyl NPP Cooling Pond) were studied to reconstruct time changes in particulate concentrations of 137Cs and its apparent distribution coefficient Kd, based on 137Cs depth distributions in bottom sediments. Bottom sediment cores collected from deep-water sites of the above water bodies were sliced into 2 cm layers to obtain 137Cs vertical profile. Assuming negligible sediment mixing and allowing for 137Cs strong binding to sediment, each layer of the core was attributed to a specific year of profile formation. Using this method, temporal trends for particulate 137Cs concentrations in the studied water bodies were derived for the first time and they were generally consistent with the semiempirical diffusional model. Based on the back-calculated particulate 137Cs concentrations, and the available long-term monitoring data for dissolved 137Cs, the dynamics of 137Cs solid–liquid distribution were reconstructed. Importantly, just a single sediment core collected from a lake or pond many years after a nuclear accident seems to be sufficient to retrieve long-term dynamics of contamination.

Bottom-supported tension leg towers with inclined tethers for offshore wind turbines

Offshore wind with high energy density and low turbulence has attracted the global scientific community towards the development of the Offshore Wind Turbines (OWTs). Today, most of the shallow water sites are already occupied, and the industry is looking to install turbines at the deep water sites (water depth > 50m). However, an OWT support structure designed with the conventional concepts becomes massive and expensive in deeper waters. In contrast, floating OWTs are more expansive than the bottom supported ones, and considered suitable for a water depth of 60 m or more. A novel support structure concept termed a ‘bottom supported tension leg tower’ (BSTLT) has been proposed recently and the possibility of using bottom supported structures in deeper waters is shown. In this paper, an extension of the BSTLT concept has been achieved using inclined tethers with a monopile. The preliminary technical feasibility including the sensitivity of the natural frequencies and dynamic analyses considering the in-place operating and the extreme design conditions has been studied for 50 m water depth. The results show that the proposed concept can be utilized to make the monopile based support structures more cost-efficient for the water depth stated above.

Preliminary survey of pests and diseases of eucheumatoid seaweed farms in the Philippines

Farmed eucheumatoids are the top aquaculture commodity in the Philippines, contributing more than 60% of total national aquaculture production by volume. Despite significant production losses observed in recent years due to pests and diseases, data relating to the temporal and spatial geographic distribution, seasonality, prevalence, and etiology of these critical problems at the farm level are lacking. Here, we assessed the prevalence of pests and diseases at 16 farm sites within several major seaweed growing areas, including Luzon (Palawan), Visayas (Bohol), and Mindanao (Zamboanga City, Davao del Norte, and Tawi-Tawi). Prevalence of pests and diseases were recorded by assessment of individual seaweed plants in situ, comprising ≥5% of the total number of seaweed plants on each farm. Results from this survey revealed “ice-ice” disease (IID) at all sites, albeit at low prevalence rates of below 25%, the exception being one site where prevalence was 100%. No significant difference in the prevalence of IID was found between farms in shallow (≈0.5 m during low tide) and deep water sites (depths exceeding 4 m during the lowest tide) (p>0.05). Moderate prevalence (26–50%) of the macro-epiphyte pests Sargassum and Ulva was reported in Luzon. Further, epiphytic filamentous algae (EFA), black spots, and evidence of grazing were recorded in several farms with low prevalence (0.2–11.2%). The three farms with the highest prevalence of IID and EFA were evaluated to determine the severity of cover on the thallus of infected plants. A very high severity of IID (76–100% coverage) was observed on the secondary and primary branches, while for EFA, low severity (≤25%) was found in all regions of the thallus. Our results suggest the widespread occurrence of yield-limiting diseases and pests affecting eucheumatoid farms in the Philippines. Strategies for the diagnosis, surveillance, and management of yield-limiting pests and diseases are needed to ensure maintenance and sustainable expansion of this important aquaculture sector in the Philippines.

Making the Invisible Visible: Underwater Malta—A Virtual Museum for Submerged Cultural Heritage

The seabed can be considered as the world’s largest museum, and underwater sites explored and studied so far provide priceless information on human interaction with the sea. In recognition of the importance of this cultural resource, UNESCO, in its 2001 Convention on the Protection of the Underwater Cultural Heritage, determined that objects/sites should be preserved in situ, whilst also advocating for public access and sharing. The implementation of these principles is not without difficulties. Some states have opened up underwater sites to the public—mainly through diving, yet the vast majority of the world’s population does not dive. In Malta, 7000 years of human occupation is reflected in and on the landscape, and recent offshore surveys show that the islands’ long and complex history has also left an indelible mark on the seabed. Besides difficulties related to their protection and management, these sites also present a challenge with regard to sharing and communicating. Recent advances in underwater imaging and processing software have accelerated the development of 3D photogrammetry of submerged sites and the idea for a virtual museum was born. The virtual museum, UnderwaterMalta, was created out of a need to share the plethora of underwater sites located on the seabed of the Maltese Islands. A multitude of digital tools are used to share and communicate these sites, offering visitors a dry dive into submerged sites that would otherwise remain invisible to the vast majority of the public. This paper discusses the basic principle of the sharing of underwater cultural heritage and the difficulties that beset the implementation of such a principle. A detailed explanation and evaluation of the methods used to gather the raw data needed is set in the context of the particular and unique working conditions related to deep water sites. The workings of this paper are based on first-hand experiences garnered through the recording of numerous wrecks over the years and the creation and launch of The Virtual Museum-Underwater Malta—a comprehensive virtual museum specifically built for “displaying” underwater archaeological sites that are otherwise invisible to the general public.