Wave Exposure

Artificial beaches behave as natural beaches, i.e. they adjust to the natural and man made conditions at the site. Good quality recreational beaches in the nature occur only when the beach is exposed to a minimum of waves and when the beach sand is of a good quality. The following main requirements shall be fulfilled to obtain a good quality artificial recreational beach: • Moderate wave exposure in the bathing season • The beach shall be stable in plan shape and in profile shape • Stabilizing structures must not generate dangerous rip currents • Good quality sand fill for construction of the artificial beach • Good bathing water quality (clear and clean water) Furthermore, the new beach scheme shall be well adjusted to the existing coastal environment in terms of social activities and urban development and in terms of landscape characteristics. These principles were utilized for the hydraulic design of a new beach park in the Copenhagen area, i.e. the Amager Beach Park. The site is...

Wave exposure can influence community structure and distribution of shallow coral reefs, by affect- ing organisms both directly and indirectly. To assess the current stony coral community condition under different degrees of wave exposure at a marine protected area of the Gulf of Cazones (SW Cuba), two expeditions were carried out in May 2010 and June 2012. Four sampling sites were sampled at reef crests (1.5 m deep), and twelve at fore-reefs, at 10, 15 and 20 m deep in four geographic locations. Live coral cover, species richness and composition, colony density, and maximum diameter were assessed using the AGRRA 2001 methodology. Multivariate and non-parametric statistics were applied to compare sites. The coral community structure within reef crests was not homogenous. The observed variability of indicators apparently was determined by great coral mortality events resulting from natural disturbances that occurred in the past (hurricanes, bleaching and diseases). Forereef coral communities displayed better condition and lower coral mortality than reef crests. Species richness and coral composition varied, while multivariate and statistical methods did not reveal site grouping with regard to wave exposure. The remaining biological condition indicators were similar among sites, except in the most exposed one, where coral cover and coral size were slightly lower. Wave exposure in the gulf of Cazones seemed not to have a significant influence on differences in condition and structure of the assessed coral communities. Rev. Biol. Trop. 64 (1): 78-93. Epub 2016 March 01.

Mangrove forests are disappearing at an alarming rate. Mangrove planting is the most common method of restoring these forests. However, this approach is not often successful, especially when the reasons for mangrove degradation were not removed prior to planting new seedlings or propagules. A successful mangrove restoration project may not necessarily include a planting phase. When the stressors are removed and suitable environmental conditions such as correct hydrology and calm area, particularly on exposed coasts, are provided, natural regeneration processes could recover mangroves from degradation. This paper describes an approach to mangrove restoration applied to an exposed shoreline on the west coast of Peninsular Malaysia. In this method a detached breakwater was erected seaward at the shoreline to shelter the restoration area from wave action, prevent the ongoing erosion and promote sediment deposition raising the elevation of the substrate to the target elevation. Survival of Avicennia marina seedlings transplanted in the sheltered area was significantly affected by sediment burial (P< 0.05). However, about eight months after construction of the breakwater, the sedimentation rate decreased and the substrate became stable. Subsequently, natural recruits appeared on the site. We postulate that waterborne seeds or propagules were available from adjacent stands in the study area but wave exposure reduced the possibility of natural recruitment. Thus the breakwater presence provided favourable conditions which could attract mangrove recruits, facilitating reestablishment and natural recovery of the mangrove ecosystem without planting. © 2010 Elsevier B.V.

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The results of a study on benthic marine algae from five localities of the Chiapas&#39; coast during summer, fall and spring of 1992 and 1993 are presented. The floristic list includes 47 species: 2 of Cyanophyceae, 17 of Rhodophyceae, 7 of Phaeophyceae, 9 of Bacillariophyceae and 12 of Chlorophyceae. Morphological description, drawings, distribution range, reproductive stage, tidal level, wave exposure, substrate and epiphytism of each species are included. Audouinella saviana (Meneghini) Woelkerling, Gracilaria bursa- pastoris (S. G. Gmelin) P. C. Silva, Hincksia rallsiae (Vickers) P. C. Silva, Cladophoropsis sundanensis Reinbold and Rhizoclonium africanum Kützing, are reported from the tropical region of Mexican Pacific shores for the first time. The species composition found in Chiapas is representative of the tropical flora as expected.

Patterns of selection on gastropod shell morphology are generally believed to be different on wave-exposed and wave-sheltered shores. The heavy surf on wave-exposed shores is thought to select for small size whereas the high risk of shell-breaking predation on wave-sheltered shores is thought to select for increased shell size and thickness. We compared the risk of shell-breaking predation to littorinid gastropods of different sizes and shell-thicknesses by tethering them on wave-exposed and wave-sheltered shores of the Northeastern Pacific. Over 2 years we found that the predation rate on the direct-developing gastropod Littorina sitkana was consistently much lower at two moderately wave-exposed sites (less than 0.01% d−1) than on the two wave-sheltered sites (8% d−1 and 2% d−1 respectively). At least 30% of the shell-breaking predation resulted in diagnostic “peeled” shell breakage patterns that could be directly attributed to predatory crabs. Observations with SCUBA at high tide suggested that most of the remainder of the shell-breaking predation was from the red rock crab, Cancer productus, and that only a small amount was from pile perch, Rhacochilus vacca. In contrast to our expectations, the smallest size-class of L. sitkana suffered significantly lower rates of predation than the largest size-class at one of the wave-sheltered sites. The effect of shell thickness on predation mortality was as predicted from previous laboratory experiments. The thin-shelled littorinid species, Littorina subrotundata, suffered significantly higher rates of predation than two thicker-shelled species, L. sitkana and L. scutulata s.l., at three of our four sites. We conclude that the higher rates of shell-breaking predation on wave-sheltered shores of the Northeastern Pacific selects for L. sitkana with thicker but not necessarily larger shells than those on wave-exposed shores.

The mapping of seabed environments is fundamental to successful fisheries management and environmental monitoring, however, there is an emerging need to better characterise habitats based upon appropriate physical parameters. In this study, relationships between seabed geomorphology and the distribution of benthic habitats were examined using multibeam sonar, underwater video, predicted wave energy, and sediment data for Esperance Bay, part of the Recherche Archipelago. This shallow (<50 m), high energy, biogenic sediment dominated environment is located in temperate southwestern Australia. Exposure to wave energy appears to determine the distribution of unconsolidated substrate, and is the most useful regional scale predictor of rhodolith and seagrass habitats. Although they are intermittently smothered by mobile sediments, limestone reefs provide habitat for a wide range of sessile organisms, even in very high wave exposure environments. The distribution of rhodolith beds is related to poorly sorted sediments that contain high gravel, mud, and CaCO3 percentages. Our results reveal that in the Recherche Archipelago, wave abrasion coupled with localised sediment transport and accumulation play a major role in increasing the diversity of inner shelf benthic habitats. This highlights the value of assessing geomorphic processes in order to better understand the distribution and structure of benthic habitats.

Marine protected areas play an important role in the conservation of marine resources and fisheries management. In the Basque Country (northern Spain), the small (158 ha) Gaztelu- gatxe Marine Reserve was established in 1998; after 5 years without exploitation, it is con- sidered likely that the goose barnacle Pollicipes pollicipes populations have recovered. This contribution provides information on the standing

Field surveys were conducted in Core and Back Sounds, North Carolina, USA, to relate the physical setting of seagrass beds, as measured by a wave exposure index (REI), tidal current speed and water depth, to various measures of the sedimentary environment, spatial heterogeneity of seagrass distribution and measures of seagrass abundance. Seagrass beds in this area form patterns ranging from