Measurements of static and dynamic mooring line damping and their importance for floating WEC devices

The dynamic response of the mooring line will be a dominant factor to consider in their use for the station keeping of a wave energy converter (WEC). Due to the relatively small size of WECs and their being moored in relatively shallow waters the effect of waves, tide and current can be of greater significance than for other floating offshore systems. Axial line stretching and high-frequency ‘top-end’ dynamics can importantly modify damping and top-end loading.If a ‘farm’ of devices is to be considered then limitations in sea space may necessitate that the devices be relatively densely packed. This will mean that the ‘footprint’ of the mooring should be constrained, to ensure that the moorings from each device do not interfere and this will have great significance for the loading experienced by the line. One must also consider how the mooring system might change the response of the WEC and so alter its ability to extract power from the waves. Unlike a typical offshore system, the design of moorings for a WEC device must consider reliability and survivability, and the need to ensure efficient energy conversion.The design and operation of a chain mooring for a WEC is considered here. Generic experimental measurements of mooring line damping were conducted in the Heriot-Watt University wave basin at a scale of 1:10. The measurements were conducted on a single mooring line for surge motions and include the study of axial stretching and high top-end dynamics. The laboratory procedures were designed to resemble tests undertaken earlier at ‘full’ scale in 24 m water depth. The measurements were also compared with numerical studies. The experimental findings for WEC devices, supports the conclusion that dynamic mooring line motion will be an important variable, needing to be considered carefully within the design.     

The infusion of sustainability into bilateral fisheries agreements with developing countries: The European Union example

The EU's bilateral fishing policy towards developing third countries has evolved over the years to increasingly emphasise sustainability, culminating in 2002 with the release of a ‘fisheries partnership approach’. The Community has begun to operationalise the policy in various West African coastal states, where its new fisheries partnership agreements are intended to function as ‘development vectors’. This paper introduces the EU's new policy, examines its potential implications for the role of sustainability in future bilateral fishing relations and highlights the impetus for it with reference to analysis of the EU's most recent agreement with Senegal based on empirical research.     

Marine archaeology in the UK: A pattern of development

Marine archaeology is a new discipline which seeks to increase knowledge of man's past activities on the sea, through the study of the remains of his ships and other relics on the ocean floor. The author argues that marine archaeology, through its combination of techniques taken from marine ecology, geology, sedimentology and other sciences, has evolved to the point in the UK where it may be classified as a science in its own right. He discusses legal and social problems of the field, and points out the need for a ‘systems approach’ in marine archaeological projects.     

Sustainable development and integrated coastal management

Agenda 21, the 40-chapter action plan, agreed to by all nations participating in the 1992 Earth Summit represents an ambitious effort to provide policy guidance across the entire spectrum of environment, development, and social issues confronting mankind. In the area of oceans and coasts (Chapter 17 of Agenda 21), the Earth Summit underscored that the management of oceans and coasts should be ‘integrated in content and anticipatory in ambit.’To assist those responsible for implementing the Earth Summit guidelines on ocean and coastal management, this article first reviews the fundamental shift in paradigm reflected in the Earth Summit agreements as well as the specific recommendations contained in Chapter 17. Next, the article examines the central concept of ‘integrated management,’ noting both its importance and its limits. A general or ‘synthesis’ model of ‘integrated coastal management’ is then presented, addressing such questions as management goals, what is being managed, where, how, and by whom.In a concluding section, methods are proposed whereby the general or ‘synthesis model’ can be tailored to diverse national contexts, involving varying physical, socio-economic, and political conditions.     

The 1997–1998 oceanic El Niño signal along the southeast and northeast Pacific boundaries—an altimetric view

Changes in the sea surface heights (SSH) and geostrophic currents along the eastern boundaries of the Pacific (North, Central and South America) are examined during the 1997–1998 El Niño using altimeter data and proxy winds. These show that ‘symmetric’ SSH signals left the equator and propagated into both Hemispheres in two episodes, with primary periods of high equatorial SSH during May–July and October–December 1997. These are the ‘distant signals’ from the mid-latitude perspective. As the signals spread poleward in each Hemisphere, their loss of symmetry demonstrates the degree to which they were altered by topographic features, local winds, and/or local currents. The first four EOFs are calculated for 2-D SSH fields in 10° wide strips along the eastern margins (60°N–60°S) and extending out along the equator from the coast to 110°W. These account for approximately 40% of the overall variability and represent the main features of the seasonal cycles and El Niño interannual variability. Snapshots of the 2-D SSH fields depict the structure of the El Niño signal at different phases of its evolution.     

A model of the upper branch of the meridional overturning of the southern ocean

A zonal-average model of the upper branch of the meridional overturning circulation of the southern ocean is constructed and used to discuss the processes – wind, buoyancy, eddy forcing and boundary conditions – that control its strength and sense of circulation. The geometry of the thermocline ‘wedge’, set by the mapping between the vertical spacing of buoyancy surfaces (the stratification) on the equatorial flank of the Antarctic Circumpolar Current and their outcrop at the sea surface, is seen to play a central role by setting the interior large-scale potential vorticity distribution. It is shown that the action of eddies mixing this potential vorticity field induces a residual flow in the meridional plane much as is observed, with upwelling of fluid around Antarctica, northward surface flow and subduction to form intermediate water. Along with this overturning circulation there is a concomitant air-sea buoyancy flux directed in to the ocean.     

Figuring fish and measuring men: the individual transferable quota system in the Icelandic cod fishery

This article discusses inequality in the Icelandic cod fishery, focusing on changes in the actual distribution of fishing quotas and the ways in which Icelanders currently talk about equity and ownership. The individual transferable quota (ITQ) system, introduced in 1984, divided access to an important resource among those who happened to be boat owners at that time. Statistical findings with respect to the cod fishery - based on a database (the ‘Quotabase’) constructed using detailed information on all vessels that have been allotted ITQs from the onset of the system - show that ITQs have been increasingly concentrated in the hands of the biggest companies. Many of the small-scale boat owners that still hold ITQs are increasingly compelled to enter into contracts that involve fishing for larger ITQ holders. It is suggested that the distribution of ITQs, as well as their evaluation in social discourse, represents an important field of research. In Iceland, public discontent with the concentration of fishing rights and the ensuing social repercussions is increasingly articulated in terms of loaded metaphors, including ‘profiteering’, ‘tenancy’ and ‘lords of the sea’. It is argued that the ultimate efficiency of management programs may be jeopardized if managers ignore the history and culture of the fisheries involved and the likely social and ecological consequences of their programs.     

The characterization of iron sulfide minerals in anoxic marine sediments

The performance of extractants commonly used in the determination of acid volatile sulfide minerals (e.g., ‘amorphous-FeS’, mackinawite and greigite) and pyrite has been evaluated using pure mineral phases and anoxic sediments. ‘Amorphous-FeS’ and mackinawite are quantitatively recovered by most cold acid extractions, but greigite recovery is incomplete. Harsher extractants with reducing agents are necessary for the complete recovery of greigite, but dissolution of fine-grained synthetic pyrite occurs under such conditions. A quantitative separation between greigite and pyrite is not possible using these techniques, but the use of ‘acid volatile sulfide’ and ‘pyrite’ as operational categories is adequate for most field studies.     

The need and practice of monitoring, evaluating and adapting marine planning and management—lessons from the Great Barrier Reef

An increasing number of scientists and resource managers recognise that successful marine management approaches, including marine spatial planning (MSP), cannot occur without effective monitoring, evaluation and adaptation. These basic components are necessary to ensure that any marine planning or marine management measures are both effective and efficient. While a number of fundamental principles for marine monitoring, evaluation and adaptive management exist, there are varying levels of understanding about how these should be undertaken and what they may achieve. Challenges include the development of realistic and measurable objectives and indicators against which effectiveness can be practically measured. The matter becomes even more complicated as the focus of marine planning and management strategies changes from ‘single species’ to ‘habitats’ and ‘ecosystems’ that may enable a diversity of permitted uses consistent with a variety of overall objectives. Over the last 30 years, the Great Barrier Reef Marine Park (GBRMP) has successfully established a multiple-use spatial management approach that allows both high levels of environmental protection and a wide range of human activities. Drawing on this unique long-term experience in the GBRMP, this article discusses key aspects of effective monitoring and evaluation, and summarises lessons learned from over two decades of adaptive management.     

What is good for the fishermen, is good for the nation: co-management in the Norwegian fishing industry in the 1990s

This paper analyses the concept of ‘co-management’ and tries to explain why co-management has recently become important to different types of fisheries administration. A preliminary analytical framework is sketched, before going on to describe the Norwegian co-management system, known as ‘centrally directed consultation’, where fishermen's representatives are established on a wide range of organisations that exert a direct influence on fisheries policy, including not only quota management but grant aid, sales, research and education. The final section is devoted to the lessons that may be learned from the Norwegian experience, bearing in mind the particular background of Norway and its historical setting.     

Decision-support Systems: Do they have a Future in Estuarine Management?

Estuaries are highly complex ecosystems. Consequently they present daunting challenges to planners and regulators responsible for devising ‘ sustainable development ’ strategies or for taking rapid decisions with respect to ‘ crisis management ’. Over the lifetime of the Estuarine and Coastal Sciences Association, there have been significant developments in both the range and sophistication of the tools available to assist with these tasks. Indeed, managers are now faced with a confusing plethora of possibilities that may, or may not, help in achieving the optimum solution to a given problem.Typical problems confronting managers and the systems available to resolve the issues are considered. By way of illustration, we present some examples based on our experience over the last 25 years in the Mersey Estuary (which has seen dramatic improvements in water quality and a number of major proposed developments), from the Ribble Estuary and from along the north-west coast of the U.K.     

Seakeeping assessment of fishing vessels in conceptual design stage

The main idea of this paper is to identify functional relations between seakeeping characteristics and hull form parameters of Mediterranean fishing vessels. Multiple regression analysis is used for quantitative assessment through a computer software that is based on the SQL Server Database. The seakeeping attributes under investigation are the transfer functions of heave and pitch motions and of absolute vertical acceleration at stern, while the ship parameters influencing motion dynamics have been classified into two groups: displacement (Δ) and main dimensions (L, B, T), coefficients that define the details of the hull form (C_WP, C_VP, LCB, LCF, etc.).Four multiple regression models having different parameter combinations are here investigated and discussed, giving way to the so-called ‘Simple Model’, ‘Intermediate Model’, ‘Enhanced 1 Model’ and ‘Enhanced 2 Model’. The obtained results are more than satisfactory for seakeeping predictions during the conceptual design stage.     

Approach to the geostrategy of the oceans: The case of the mediterranean

It is known that by the general ‘geostrategy’ for the oceans we mean the behaviour of countries of the world in defending their own vital economic interests as projected on different oceans. The means for protecting national interests can be economic, political, diplomatic or military. This paper dwells in particular on these last aspects, offering in the first part some useful reflections on the analysis of regional seas. The second part gives elements for the understanding of the complex Mediterranean situation where the East-West confrontation is accentuated by widespread economic, political, ideological and ethnic contrasts between coastal states. For these reasons this sea can be defined as one of the most unstable and belligerent regions in the world.     

Winter processes on northern salt marshes: Evaluating the impact of in-situ peat compaction due to ice loading, Wells, ME

New England salt marshes are dominated by the supratidal high marsh grass, Spartina patens. This grass forms a nearly planar surface, which makes it highly vulnerable to the predicted regime of accelerated sea-level rise (SLR). If the high marsh cannot keep pace with rising sea level it will be transformed to intertidal environments, leading to unusually rapid coastal evolution. Winter processes such as ice-loading of surface peat may degrade the marsh surface. Large volumes of snow and ice compress peat, resulting in shallow compaction and a net loss of elevation in some areas.On the Webhannet marsh in Maine, a simulated ice compaction experiment indicates that thick ice can compress marsh peat (46 cm simulated ‘ice’ produced 6.9 ± 0.3 mm of compaction; 24 cm ‘ice’ produced 3.0 ± 0.8 mm). Experimental data suggest that ice thicknesses greater than 10 cm depress the marsh surface by 2 mm for each cm of total ice thickness. However, surface elevations rebounded to near-control levels within 2 weeks of the removal of simulated ‘ice’ from the surface of the marsh. Normal winter ice accumulations on New England marshes, therefore, do not appear to be sufficient to permanently compact marsh surface peat and lead to loss in marsh surface elevation.     

Theoretical, numerical and experimental study on the problem of ergodicity and ‘practical ergodicity’ with an application to parametric roll in longitudinal long crested irregular sea

This paper addresses the problem of ergodicity of stochastic processes starting from a theoretical point of view, with the aim of obtaining a deeper understanding for practical applications. The problem is tackled bearing in mind the concept of ‘practical ergodicity’, that is, the possibility of obtaining reliable information about ensemble averages by using temporal averages. Some general analytical tools are given to address the problem of accuracy of temporal averages and an example of their use in a possible design of experiments is given. A series of Monte Carlo numerical simulations are performed by means of an analytical non-linear 1.5-DOF model of parametrically excited roll motion. The outcomes of such simulations are analysed to show the effect of ship speed and sea spectrum shape. The effect of wave grouping phenomenon is discussed with particular attention to the Doppler effect. Qualitative indications given by the numerical simulations are then compared with experimental tests showing a good agreement. Practical ergodicity of generated sea in towing tank is also briefly addressed.     

Zooplankton and forage fish species off Peru: Large-scale bottom-up forcing and local-scale depletion

The Humboldt Current System, like all upwelling systems, has dramatic quantities of plankton-feeding fish, which suggested that their population dynamics may ‘drive’ or ‘control’ ecosystem dynamics. With this in mind we analysed the relationship between forage fish populations and their main prey, zooplankton populations. Our study combined a zooplankton sampling program (1961–2005) with simultaneous acoustic observations on fish from 40 pelagic surveys (1983–2005) conducted by the Peruvian Marine Research Institute (IMARPE) and landing statistics for anchoveta (Engraulis ringens) and sardine (Sardinops sagax) along the Peruvian coast from 1961 to 2005. The multi-year trend of anchoveta population abundance varied consistently with zooplankton biovolume trend, suggesting bottom-up control on anchovy at the population scale (since oceanographic conditions and phytoplankton production support the changes in zooplankton abundance). For a finer-scale analysis (km) we statistically modelled zooplankton biovolume as a function of geographical (latitude and distance from the 200-m isobath), environmental (sea surface temperature), temporal (year, month and time-of-day) and biological (acoustic anchovy and sardine biomass within 5 km of each zooplankton sample) covariates over all survey using both classification and regression trees (CART) and generalized additive models (GAM). CART showed local anchoveta density to have the strongest effect on zooplankton biovolume, with significantly reduced levels of biovolume for higher neighbourhood anchoveta biomass. Additionally, zooplankton biovolume was higher offshore than on the shelf. GAM results corroborated the CART findings, also showing a clear diel effect on zooplankton biovolume, probably due to diel migration or daytime net avoidance. Apparently, the observed multi-year population scale bottom-up control is not inconsistent with local depletion of zooplankton when anchoveta are locally abundant, since the latter effect was observed over a wide range of overall anchoveta abundance.     

Fish Larvae Abundance and Distribution in the Coastal Zone off Terminos Lagoon, Campeche (Southern Gulf of Mexico)

Fish larvae abundance and distribution in the coastal zone off Terminos Lagoon and their relation to the environmental features of the Lagoon inlets were analysed (1986–87). The sampling grid consisted of 24 stations extending between 0·5 and 10 km off the Lagoon, including both Terminos Lagoon Inlets; El Carmen and Puerto Real. A total of 23 families and 43 species were identified. Highest larval abundance was registered during the rainy period (July and September) when the fluvial discharges favoured the planktonic development. The lowest larval abundance was recorded in the period of northern cold wind (January–March) when the fluvial discharges decreased. Bray-Curtis index defined two groups of stations, corresponding to each of the lagoon inlets, persisting throughout the year. The first one, ‘ El Carmen ’, was characterized by larvae of Engraulidae and Gobiidae; estuarine-dependent inhabitants. This group could be considered as a functional extension of the Lagoon to the sea. The second group, ‘ Puerto Real ’, was characterized by highest larval abundance of marine dwellers (e.g.Opisthonema oglinumandHarengula jaguana). This situation suggests that the Puerto Real Inlet could be the main entrance of marine fishes into the Lagoon. These results indicate that the coastal zone off Terminos Lagoon constitutes an important nursery area both for species spending part of their life cycle linked to this estuarine system, and for marine species that migrate towards the Lagoon, carried by local currents.     

Nutrient processing and the development of tidal creek ecosystems

The North Inlet marsh-estuarine system encompasses the spectrum of interaction between the ocean and the uplands typical of the southeastern United States. The system is an ebb-dominated, bar-built estuary with good flow connection to the sea and some freshwater input.The North Inlet basin has evolved from a forested, relic, beach-ridge terrain under a regime of slowly rising sea level (2 mm year⁻¹). This mode of development is supported by historic tide gage data. ²¹⁰Pb dating of sediment cores, the presence of spodic soil horizons and tree roots at shallow depths beneath the marsh surface, and the presence of relic ‘cat eye’ ponds at the edge of the salt marsh. As sea level rises, the boundary between forest and salt marsh recedes upslope and forest spodosols are gradually transformed into marsh soils by salinization, the deposition and mixing of marine mud into the upper horizons of the forest soil and the accumulation of reduced sulfur via sulfate reduction. As a forest watershed is transformed into a salt-marsh basin, the hydraulic geometry of the original, black-water (fresh) stream increases to accommodate the increasing volumes of tidal discharge. Forest sands move seaward while marine muds are transported into the basin.As water moves between the forest and the sea, it passes through creeks in different developmental stages. Large mature creeks interact with the ocean while young, ephemeral creeks drain the uplands and intertidal marsh zones. Intermediate stage creeks connect these two and are characterized by the presence of oyster reefs. Net nutrient fluxes appear to be different in each developmental stage.The ‘Bly Creek’ study of Dame and coworkers addressed the flux of materials between a creek at the intermediate stage of development and the adjacent mature system. Material fluxes from a freshwater stream draining into Bly Creek from the adjacent uplands were also observed. The role of the salt marsh and the oyster reefs in determining material fluxes was examined. The Bly Creek basin imports particulate nutrients and exports dissolved forms.The ‘Outwelling’ study of Dame and coworkers at North Inlet focused on the flux of materials between the mature creeks and the Atlantic Ocean. All constituents were exported seasonally and annually from the estuary, except total sediments (imported during fall and winter) and chlorophyll a (imported in the summer and fall). The export of carbon, nitrogen and phosphorus was high compared with other estuarine systems.On a unit area basis, primary productivity is higher and nutrient fluxes are lower in Bly Creek (intermediate stage of development) as compared with the mature North Inlet system. These observations support the general ecosystem development hypothesis that nutrient storage and retention are higher in younger systems than more mature systems where growth is lower and fewer nutrients are needed.