Sedimentology of a subtidal,tide-dominated sand body in the Yellow Sea,southwest Korea

Odanam Satoe, a subtidal, tide-dominated sand body in the Yellow Sea, Korea, is linear in plan and asymmetrical in cross-section. It consists of fine- to medium-grained, well-sorted subangular sand. Bedforms consist of high-amplitude (1–2 m) sandwaves on the lower flanks of the gentler-sloping bar surface, and medium-amplitude (0.5-1 m) sandwaves on the sand body trough adjoining the steeper face, the bar crest and shallower parts of the gently sloping bar surface. Bedforms are absent on the relatively steeper bar surface, which is characterized by 2° slopes. Bedform orientation on the gentler slope is oblique by 30° to the bar crest, parallel to the sand-body crest on the crest itself, and opposite to the steeper sand-body face in the trough below the steeper slope of the bar.Bottom current velocity data show that tidal currents are semi-rotary with a flood time—velocity asymmetry over the gentler slope, and ebb time—velocity asymmetry over the steeper slope during most of the tidal cycle. Tidal-current flow parallels bar elongation over the steeper slope, whereas over the gentler slope, tidal-current flow is directed at 30° to the bar crest and changes to normal to the crest one hour prior to low tide. Bedform orientation mapped with side-scan sonar shows agreement with these flow directions.Sand dispersal around the sand body is controlled by time—velocity asymmetry and partial rotary flow directions of tidal currents. This circulation causes not only a trapezoidal mode of grain dispersal, but also westerly migration of the sand body documented from comparative bathymetric surveys in 1964 and 1980.     

Depth Zonation, Micro habitat, and Morphology of Three Species of Acanthemblemaria (Pisces: Blennioidea) in the Guif of California, Mexico

Abstract. The utilization of the spatial resources of refuge type, size and depth placement is investigated in the three sympatric species of Acanthemblemaria at the cape region of Baja California, Mexico. A. balanorum occupies barnacle testes (Balanus tintinnabulum), A. macrospilus occupies barnacles and mollusk tubes (vermetid gastropods and pholadids), and A. crockeri occupies only mollusk tubes (pholadids). Refuge diameter overlap is higher than overlap in depth. A. crockeri consistently occupies depths below 5m. Competition experiments for barnacle refuges among the three species indicate that A. balanorum is a superior competitor for such refuges. Prior residency of a less superior species changes the outcome of refuge competition in its favor. The morphological specialization of A. balanorum and A. macrospilus is evident in a high correlation between head size and standard length. A. balanorum selects refuges with entrance diameters highly correlated to standard length.     

Breaking wave impact on vertical and sloping coastal structures

The results of laboratory experiments on the maximum and bottom impact pressures from waves breaking directly on vertical and sloping faced coastal structures are presented. Direct wave breaking on a wall is classified as early, late, and perfect breaking. Although the present study is aimed at dealing with the type of impact resulting from the perfect breaking, to some extent the occurrence of early and late breaking are unavoidable. The wave impact pressures, therefore, have a random nature of variation from impact-to-impact under the same conditions. The maximum and bottom impact pressures on walls are treated statistically. The effects of the wall angle and foreshore slope on these two quantities are examined. The results show that for practical applications, the still-water level can be taken as the acting place for the maximum impact pressure on the wall. Simultaneous impact pressure distribution below and above still-water level may be approximated as parabolic and linear, respectively. Finally, using a wall deflection criterion, a water depth region in front of the wall is defined, where the breaking wave forces may reach a critical level.     

Harpacticoida taxocen diversity in the silty-sandy littoral zone of Kandalaksha Bay of the White Sea

The fauna composition, ecological groups, and life forms of Harpacticoids of soft littoral grounds from 15 sites off the Karelian coast in Kandalaksha Bay of the White Sea were studied. Six types of harpacticoid taxocens with different sets of dominating species are described. On silty sands with clear signs of desalination, the Stenchelia palustris taxocen is common; medium-grained sands are characterized by the Heterolaophonte minuta, Paraleptastacus kliei — Huntemannia jadensis, and Amphiascoides nanus — Scottopsyllus minor taxocens; while on coarse sands, the Ameira parvula and Ameira scotti — Mesochra lilljeborgi taxocens have developed. The diversity of the taxocens is partly explained by the differences in the grain-size composition and salinity at different sites. In addition, groups of various taxocens dwelling on the same type of the sediments were found in different minor bights of the coastline.     

Interstitial water chemistry of villefranche bay sediments: Trace metal diagenesis

Pore water aliquots were taken with an in situ close interval sampler: the “Peeper”.We report here the pore water concentration profiles of TCO₂, SO₄, TH₂S, Ca and the trace metals Mn, Cu, Pb, Cd and Cr from sediments of a relatively polluted area, the Villefranche Bay, on the French Riviera (close to Nice).We investigated the major ion concentrations in order to establish geochemical mass balances of organic matter oxidation. ΔTCO₂/ΔSO₄ was <−2.0, reflecting the precipitation of calcite as confirmed by the calcium profile. Reduction of sulfate led to increasing sulfide concentrations with depth.Trace metal interstitial water concentrations decreased from 63 to 5 nM, 18 to 4 nM and 6.6 to less than 2 nM for Cu, Pb and Cr, respectively. Cd showed a different pattern with top and deep values of 0.7 nM and a minimum of 0.27 nM.Thermodynamic calculations were performed which suggest the potential formation of mineral phases such as sulfides.     

Power from the people: a documentation of non-governmental organizations' experience in community-based coastal resource management in the Philippines

Community-based coastal resource management projects facilitated by non-governmental organizations (NGOs) in the Philippines have explored approaches to decrease poverty-driven over-exploitation of coastal resources. There has been little reporting and analysis of such activities until recently. Nine case studies have recently been published and this paper presents a brief summary of these, along with an analysis of the trends and themes identified. Though diverse and covering the Philippines from Mindanao to Luzon, the case studies highlight the value of community commitment and participation in decisions regarding, and in the implementation of, resource management in ways that consider not only the bio-physical aspects of resource management but the social, economic and legal implications. Experience in working with local government has been both successful and limited. Successful projects raise hopes for further progress through education and organization of communities to improve livelihoods and protect coastal resources.     

An inexpensive instrument for measuring benthic current velocity and direction at sea

An instrument which measures the velocity and direction of benthic water currents at depths of up to 80 m is described. Characteristics of this meter include: (i) readings are not affected by water flow during sinking or retrieval; (ii) it is portable; (iii) it operates unattended; (iv) it is inexpensive; and (v) it requires only simple maintenance. A timing circuit which operates two time periods in succession is used to activate and de-activate a revolution counter and a fluidfilled compass which are mounted on a special frame and vane system. In the field, the instrument accurately measured average current velocities of up to 6 m s⁻¹. Data are presented which illustrate the usefulness of this instrument in describing the velocity and direction of benthic currents along the east coast of Australia and demonstrate a positive correlation between benthic current velocity and catch rates of the commercially-exploited spanner crab Ranina ranina.