The Submarine Volcano Eruption off El Hierro Island: Effects on the Scattering Migrant Biota and the Evolution of the Pelagic Communities

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Coastal vulnerability assessment based on video wave run-up observations at a mesotidal, steep-sloped beach

Coastal imagery obtained from a coastal video monitoring station installed at Faro Beach, S. Portugal, was combined with topographic data from 40 surveys to generate a total of 456 timestack images. The timestack images were processed in an open-access, freely available graphical user interface (GUI) software, developed to extract and process time series of the cross-shore position of the swash extrema. The generated dataset of 2% wave run-up exceedence values R 2 was used to form empirical formulas, using as input typical hydrodynamic and coastal morphological parameters, generating a best-fit case RMS error of 0.39 m. The R 2 prediction capacity was improved when the shore-normal wind speed component and/or the tidal elevation η tide were included in the parameterizations, further reducing the RMS errors to 0.364 m. Introducing the tidal level appeared to allow a more accurate representation of the increased wave energy dissipation during low tides, while the negative trend between R 2 and the shore-normal wind speed component is probably related to the wind effect on wave breaking. The ratio of the infragravity-to-incident frequency energy contributions to the total swash spectra was in general lower than the ones reported in the literature E infra/E inci > 0.8, since low-frequency contributions at the steep, reflective Faro Beach become more significant mainly during storm conditions. An additional parameterization for the total run-up elevation was derived considering only 222 measurements for which η total,2 exceeded 2 m above MSL and the best-fit case resulted in RMS error of 0.41 m. The equation was applied to predict overwash along Faro Beach for four extreme storm scenarios and the predicted overwash beach sections, corresponded to a percentage of the total length ranging from 36% to 75%.info:eu-repo/semantics/publishedVersio

Diel Vertical Movements and Feeding Activity of Zooplankton in St. Georges Bay, N.S., Using Net Tows and a Newly Developed Passive Trap

Newly developed plankton traps, designed to passively collect vertically mobile plankters, sampled ascending plankton but failed to collect many species during descent. This discrepancy may be behavioral with passively sinking organisms reacting to the trap surface with an upward avoidance reaction. Simultaneous use of conventional net tows and semiautomated traps allowed us to interpret the vertical movements of plankton more fully than by either method alone. Asynchronous vertical movement of the Pseudocalanus population is suspected because the percentage of trapped animals with food in their guts was usually higher in the downward moving fraction of the population. Migratory behaviors ranged from dusk and dawn ascent with midnight sinking to reverse migrations where the night level inhabited is deeper than the day depth. Noctural dispersal of herbivore and omnivore populations over depth probably reflects predator avoidance by presenting less dense aggregations to vertically mobile predators. Sightless predators reside in deeper waters than their prey during daylight presumably because they are larger and more vulnerable themselves to visual predation. Visual predators descend to greater depths than their prey at night. All the migration patterns observed can be explained in evolutionary terms simply by competition for food and avoidance of predators. </jats:p