A Comparison of Beach Nourishment Methodology and Performance at Two Fringing Reef Beaches in Waikiki (Hawaii, USA) and Cadiz (SW Spain)

Fringing reefs have significant impacts on beach dynamics, yet there is little research on how they should be considered in beach nourishment design, monitoring, and conservation works. Thus, the behavior and characteristics of nourishment projects at two reef protected beaches, Royal Hawaiian Beach (RHB) in Hawaii, USA, and Victoria Beach (VB) in Cadiz, Spain, are compared to provide transferable information for future nourishment projects and monitoring in fringing reef environments. The nourishment cost at RHB was nine times higher than VB. This is partly due to lower total volume and a more complex placement and spreading method at RHB, despite the much closer borrow site at RHB. There was a significant difference in post-nourishment monitoring frequency and assessment of accuracy. RHB elevation was monitored quarterly for 2.7 years at 30 m-spaced profiles, compared to 5 years of biannual surveys of 50 m-spacing at VB. An additional problem related to the presence of reefs at both RHB and VB was estimating the beach volume increase after nourishment, due to variable definitions of the ‘beach’ area and high alongshore variability in reef topography. At sites where non-native sediment is used, it is imperative to understand how wave and current energy changes due to reefs will influence nourishment longevity. Thus, differences in erosion and accretion mechanisms at both beaches have been detected, though are still little understood. Moreover, discrepancies in sediment porosity between the two sites (which should be surveyed in future nourishments) have been found, probably due to differences in the nourishment sand transportation and distribution methods. In summary, more dialogue is needed to explicitly consider the influence of fringing reefs on coastal processes and beach nourishment projects.

Transport of enterococci and F+ coliphage through the saturated zone of the beach aquifer

Coastal groundwater has been implicated as a source of microbial pollution to recreational beaches. However, there is little work investigating the transport of fecal microbes through beach aquifers where waters of variable salinity are present. In this study, the potential for fecal indicator organisms enterococci (ENT) and F+ coliphage to be transported through marine beach aquifers was investigated. Native sediment and groundwaters were collected from the fresh and saline sections of the subterranean estuary at three beaches along the California coast where coastal communities utilize septic systems for wastewater treatment. Groundwaters were seeded with sewage and removal of F+ coliphage and ENT by the sediments during saturated flow was tested in laboratory column experiments. Removal varied significantly between beach and organism. F+ coliphage was removed to a greater extent than ENT, and removal was greater in saline sediments and groundwater than fresh. At one of the three beaches, a field experiment was conducted to investigate the attenuation of F+ coliphage and ENT down gradient of a septic leach field. ENT were detected up to 24 m from the leach field. The column study and field observations together suggest ENT can be mobile within native aquifer sediments and groundwater under certain conditions.

Factors affecting individual body weight in field populations of the mudsnail Hydrobia ulvae

Differences in average body size among allopatric and sympatric populations of hydrobiid mudsnails have been interpreted as the consequence of interspecific competitive interactions. Recently, however, doubts have been expressed concerning the certainty with which size differences can be ascribed simply to character displacement. Other environmental factors are known to influence body size in hydrobiids. In the present study one of these, sediment type, was investigated.Average body weight of Hydrobia ulvae (Pennant) living on fine mud was consistently higher than that of members of the same species living on adjacent muddy sand. Snails were transplanted from one sediment type to the other, confined within cages, and their growth rates compared with those of control animals caged on their native sediment. The results of this experiment suggested that substrate type is one factor controlling body size, but the inconclusive nature of the results indicate that others are also involved.

Sediment and Ecosystem Characteristics of a Detention Lake Receiving Urban Runoff

There is limited availability of data on long term impact of urban runoff on detention ponds used for pollutant removal or flood control. A small lake exclusively receiving urban runoff from a catchment that has been stable for over 20 years has been studied. A varied local ecosystem with regionally significant bird and other species has developed in the area. Fish sensitive to turbidity have survived in the lake. Core sediment samples were taken for analyses. The organic content and consolidation of deposited material have been characterized. Sediment is characteristic of actively decomposing material. Lead, copper and zinc were found in concentrations that were twice as high in recently deposited material compared to the native sediment, however, cadmium concentrations were not found to vary between layers.