The problem of the response of a porous elastic bed to water waves is treated analytically on the basis of the three-dimensional consolidation theory of Biot (1941). Exact solutions for the pore-water pressure and the displacements of the porous medium are obtained in closed form for the case of waves propagating over the poro-elastic bed. The theoretical results indicate that the bed response to waves is strongly dependent on the permeability k and the stiffness ratio G/K’, where G is the shear modulus of the porous medium and K’ is the apparent bulk modulus of elasticity of the pore fluid. The earlier solutions for pore-water pressure by various authors are given as the limiting cases of the present solution. For the limits G/K′ → 0 or k→ ∞, the present solution for pressure approaches the solution of the Laplace equation by Putnam (1949). For the limit G/K′→ ∞, the present solution approaches the solution of the heat conduction equation by Nakamura et al. (1973) and Moshagen & Torum (1975).The theoretical results are compared with wave tank experimental data on pore-water pressure in coarse and fine sand beds which contain small amounts of air. Good agreement between theory and experiment is obtained.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022112078003006

On the response of a poro-elastic bed to water waves

Water motion is a key determinant of marine macroalgal production, influencing directly or indirectly physiological rates and community structure. Our understanding of how marine macroalgae interact with their hydrodynamic environment has increased substantially over the past 20 years, due to the application of tools such as flow visualization to aquatic vegetation, and in situ measurements of seawater velocity and turbulence. This review considers how the hydrodynamic environment in which macroalgae grow influences their ability to acquire essential resources and how macroalgae might respond physiologically to fluctuations in their hydrodynamic regime with a focus on: (1) the biochemical processes occurring within the diffusion boundary layer (DBL) that might reduce rates of macroalgal production; (2) time scales over which measurements of velocity and DBL processes should be made, discussing the likelihood of in situ mass transfer limitation; (3) if and how macroalgal morphology influences resource acquisition in slow flows; and (4) ecobiomechanics and how hydrodynamic drag might influence resource acquisition and allocation. Finally, the concept that macroalgal production is enhanced in wave-exposed versus sheltered habitats is discussed.

Water motion, marine macroalgal physiology, and production.

An empirical model to estimate the propagation of random breaking and nonbreaking waves over vegetation fields

This review about the genus Laminaria sensu lato summarizes the extensive literature that has been published since the overview of the genus given by Kain in 1979. The recent proposal to divide the genus into the two genera Laminaria and Saccharina is acknowledged, but the published data are discussed under a 'sensu lato' concept, introduced here. This includes all species which have been considered to be 'Laminaria' before the division of the genus. In detail, after an introduction the review covers recent insights into phylogeny and taxonomy, and discusses morphotypes, ecotypes, population genetics and demography. It describes growth and photosynthetic performance of sporophytes with special paragraphs on the regulation of sporogenesis, regulation by endogenous rhythms, nutrient metabolism, storage products, and salinity tolerance. The biology of microstages is discussed separately. The ecology of these kelps is described with a focus on stress defence against abiotic and biotic factors and the role of Laminaria as habitat, its trophic interactions and its competition is discussed. Finally, recent developments in aquaculture are summarized. In conclusion to each section, as a perspective and guide to future research, we draw attention to the remaining gaps in the knowledge about the genus and kelps in general.

https://www.tandfonline.com/doi/pdf/10.1080/09670260701711376

The genus Laminaria sensu lato : recent insights and developments

Kelp forests along temperate and polar coastlines represent some of most diverse and productive habitats on the Earth. Here, we synthesize information from >60 years of research on the structure and functioning of kelp forest habitats in European waters, with particular emphasis on the coasts of UK and Ireland, which represents an important biogeographic transition zone that is subjected to multiple threats and stressors. We collated existing data on kelp distribution and abundance and reanalyzed these data to describe the structure of kelp forests along a spatial gradient spanning more than 10° of latitude. We then examined ecological goods and services provided by kelp forests, including elevated secondary production, nutrient cycling, energy capture and flow, coastal defense, direct applications, and biodiversity repositories, before discussing current and future threats posed to kelp forests and identifying key knowledge gaps. Recent evidence unequivocally demonstrates that the structure of kelp forests in the NE Atlantic is changing in response to climate- and non-climate-related stressors, which will have major implications for the structure and functioning of coastal ecosystems. However, kelp-dominated habitats along much of the NE Atlantic coastline have been chronically understudied over recent decades in comparison with other regions such as Australasia and North America. The paucity of field-based research currently impedes our ability to conserve and manage these important ecosystems. Targeted observational and experimental research conducted over large spatial and temporal scales is urgently needed to address these knowledge gaps.

/pdf/threats-and-knowledge-gaps-for-ecosystem-services-provided-e88azn0i2a.pdf

Threats and knowledge gaps for ecosystem services provided by kelp forests: a northeast Atlantic perspective.

Scour around coastal structures: a summary of recent research $

Effect of the kelp Laminaria hyperborea upon sand dune erosion and water particle velocities

Aquatic vegetation, like seagrasses, macroalgae and trees whether submerged or subaerial are an important feature of a coastal ecosystem. In addition to the structural and functional aspects to the environment, they are known to reduce wave and current energies propagating through them. The reduction of energy would then influence sediment motion and thus render an impact on coastal sediment transport. The dissipative character of large stands of kelp has been studied for instance by Jackson and Winant, (1983), Dalrymple et al. (1984) and for artificial seaweed as material for shore protection Price et al. (1968).

https://icce-ojs-tamu.tdl.org/icce/index.php/icce/article/download/4952/4632

Wave Damping by Kelp Vegetation

A theoretical investigation on the transmission of wave induced pressures into a permeable sea bottom has been performed. Assuming that the soil water is compressible, while the grain skeleton is assumed rigid, the resulting theoretical model describes an effective mechanism by which the soil permeability affects the pressure transmission.

Wave Induced Pressures in Permeable Seabeds

A laboratory experiment was carried out to investigate wave energy dissipation in a coastal kelp field of Laminaria hyperborea with a purpose of finding the damping rate. Parameters measured were wave heights at 8 locations along the direction of wave propagation, forces on artificial kelp plants, and velocities in between the plants in 4 different water depths. It was found that in 4, 6, 8 and 10 meter water depths, the damping coefficient was 0.0094, 0.0032, 0.0014 and 0.0005m"1 respectively. Results show that the damping rate varies with population density, size of plant, water 'depth and wave period.

https://icce-ojs-tamu.tdl.org/icce/index.php/icce/article/download/5417/5093

Alf Tørum

Papers

Scour around coastal structures: a summary of recent research $

Effect of the kelp Laminaria hyperborea upon sand dune erosion and water particle velocities

Wave Damping by Kelp Vegetation

Wave Induced Pressures in Permeable Seabeds

Wave energy dissipation in kelp vegetation