Intertidal Beach Research Articles

Rip Current Prediction: Development, Validation, and Evaluation of an Operational Tool

ABSTRACT Austin, M.J.; Scott, T.M.; Russell, P.E., and Masselink, G., 2013. Rip current prediction: development, validation, and evaluation of an operational tool. This contribution details the development, validation, and evaluation of an operational rip current prediction tool. Field measurements of rip current dynamics from a macrotidal beach in the southwest U.K. collected over 87 tidal cycles indicate that the rip currents are highly dynamic over a range of temporal and spatial scales. The morphology of the lower intertidal beach face provides the primary spatial control of the rip currents, whereas the variation in the pattern of wave dissipation due to the tidal translation of the surf zone at spring-neap and semidiurnal frequencies is the principle temporal control. The Lagrangian drift pattern associated with the rip currents displays three key behaviors: rotation, alongshore, and exit. Rotation and exit are observed under moderate conditions, whereas strong alongshore-directed currents prevail d...

The effects of beach nourishment on benthic invertebrates in eastern Australia: Impacts and variable recovery

Beach erosion is likely to accelerate, driven by predicted consequences of climate change and coastal development. Erosion is increasingly combated by beach nourishment, adding sand to eroding shores. Because a range of engineering techniques exists to nourish beaches, and because these techniques differ in their environmental effects, assessments of ecological impacts need to be tailored and specific. Here we report on impacts and recovery of benthic invertebrates impacted by beach nourishment operations undertaken at Palm Beach (SE Queensland, Australia). Assessments are made based on a beyond-BACI design, where samples were taken once before nourishment and twice afterwards at the impact and two control sites. Because almost all of the sand was deposited on the upper beach and later moved with bulldozers down-shore, we specifically examined whether the effects of nourishment varied at different heights of the beach—a little-studied question which has management implications. Impacts on the fauna were massive on the upper and middle levels of the beach: samples collected two days after the conclusion of nourishment were entirely devoid of all invertebrate life (‘azoic’), whereas weaker effects of nourishment were detectable on the lower shore. Recovery after five months also varied between shore levels. The sediment of the upper level near the dunes remained azoic, the fauna of the middle shore had recovered partially, and the lower level had recovered in most respects. These findings indicate that the height and position of sand placement are important. For example, rather than depositing fill sand on the intertidal beach, it could be placed in the shallow subtidal zone, followed by slow up-shore accretion driven by hydrodynamic forces. Alternatively, techniques that spread the fill sand in thin layers (to minimize mortality by burial) and leave unfilled intertidal refuge islands (to provide colonists) may minimize the ecological impacts of beach nourishment.

Short-term observation of beach dynamics using cross-shore profiles and foreshore sediment

Cross-shore beach profiles and textural characteristics of foreshore sediment were analyzed for understanding an annual cycle of intertidal beach dynamics at Devbag, an Island sheltered estuarine coast. This study is carried out as response to the shoreline management project proposed by Ministry of Earth Science, India. Cross-shore transects were monitored in a monthly interval during February 2008 to February 2010 along with collection of beach surface sediment samples. Change in beach volume over an annual cycle showed a slow rate of sediment accretion at the Devbag beach where the maximum accretion was found at dissipative zone. During the year 2008–09, the volume of sediment accretion was 24.23 m3/m with an average beach width and slope of 91 m and 3.3° respectively. During 2009–2010, the accreted beach volume was 33.54 m3/m with an average beach width and slope of 132 m and 2.6° respectively. The beach along the coast was varying from extremely gentle to a slightly steeper slope which showed dissipative to reflective nature. The Beach was dominated by both fine and medium sands. More quantity of unimodal and bimodal sediment was found with moderately well sorted and moderately sorted nature. No significant correlation in beach morpho-sedimentary characteristics was found due to the non-uniform trend in beach morphodynamics and textural characteristics. Present study emphasizes the need to observe the beach changes over inter-annual seasons before planning coastal protection measures. The results of the study will be helpful for formulating an effective coastal zone management plan at Devbag, Kali estuary, west coast of India.

Turbulence dissipation under breaking waves and bores in a natural surf zone

Wave breaking is the primary driver of beach erosion, injecting breaking-induced turbulence at the sea surface and diffusing bed boundary layer turbulence at the sea bed. The limited understanding of the vertical turbulence structure under natural breaking waves, and hence sand entrainment, is one of the reasons that coastal-evolution models produce inadequate estimates of storm response. Here we use a recently collected field dataset to analyze turbulence dissipation under breaking waves and bores on the intertidal beach at Truc Vert, France. The vertical structure of the turbulent dissipation rate indicates that wave breaking is the dominant source of turbulence dissipation. The current-induced turbulence represents no more than 50% of the turbulent dissipation rate close to the bed (at 10% of the water column), even when alongshore currents reach 1m/s. The data further illustrate that the turbulent dissipation rate is almost depth-uniform under breaking waves, whereas it decreases profoundly toward the bed under bores. Moreover, we found that the fraction of wave energy flux decay dissipated below wave-trough level is about 1% under breaking waves and about 10% under bores. These results imply that the turbulent dissipation rate in the surf zone is severely underestimated by coastal-evolution models that do not consider breaking-induced turbulence as a surface boundary condition. Consequently, they will underestimate sand stirring and transport by mean currents during severe storms.

ECHINODERM REMAINS IN SHALLOW-WATER CARBONATES AT FERNANDEZ BAY, SAN SALVADOR ISLAND, BAHAMAS

Echinoderm remains in the sand-size fraction of tropical, shallow-water carbonates were investigated in order to correlate depositional environments, preservation potentials, distribution, and taphonomic signatures. Fifteen sediment bulk samples were collected from five different environments at Fernandez Bay, San Salvador Island, Bahamas. Studied environments include: (1) intertidal beach rock, (2) subtidal bedrock overgrown by algae, (3) a subtidal Sargassum meadow, (4) a subtidal patch reef, and (5) subtidal loose sands without vegetation. At least 50 echinoderm elements and or fragments were randomly sampled from the fractions of 125–250 µm, 250–500 µm, and 500–1000 µm, resulting in a total number of 2355 ossicles. The distribution and taphonomic signature of the remains were analyzed using exploratory data analyses. Echinoid remains decrease coincident with an increase in ophiuroid ossicles from shore to reef. Encrustation and bioerosion are rare in the sand-sized fraction, whereas fragmentation and abrasion are common traits observed in all environments. Within-environment variation is high, however, and only the analyses of further transects can assess the influence of variability along the shore. The combination of distribution patterns and taphonomic signatures, however, reveals trends to distinguish three depositional environments that are characterized by: (1) a high percentage of echinoid remains, and high fragmentation and abrasion levels; (2) high fragmentation and low abrasion values; and (3) a high percentage of ophiuroid remains, and intermediate values for both fragmentation and abrasion. These results can aid in future analyses and interpretation of ancient carbonate deposits.

An algorithm for the measurement of shoreline and intertidal beach profiles using video imagery: PSDM

A critical factor when undertaking proper coastline management is the availability of reliable data, allowing those responsible to make informed decisions about land use and its impact on natural resources. Marine resource data (bathymetry, time-series of waves, coastal use levels, etc.) have often been difficult for policy-makers to obtain and use, given the high costs involved and difficulties in their application and interpretation. In cases where a source of coastline data is available, it is important that it be sufficiently complete to compare habitat changes (in morphology and use) that are only observable over a period of years. Thus, it is necessary to look for alternative methods to obtain this long-term information. The availability of new data-gathering techniques for the study of coastlines and coastal processes, such as remote sensors and underwater photography and videography, has increased during the last decade. One of the principal research applications of these techniques is bathymetry. This paper presents state-of-the-art image-based models that allow the construction of topo-bathymetric shore data. The Physical and Statistical Detection Model (PSDM), which constitutes the core of this research, is discussed and validated. The PSDM is based on a combination of six different algorithms that describe the shoreline features, and it assigns physical and statistical criteria to the detection process. In conclusion, a numerical tool based on video systems is introduced which shows great potential for monitoring coastal issues and supplying data to aid technicians and shoreline managers.

Sabah Al-Ahmad Sea City Kuwait: development of a sustainable man-made coastal ecosystem in a saline desert

The coastal ecosystems of the northwestern Arabian Gulf mostly consist of low lying tidal flats backed by hyper saline marsh (sabkha) and desert. As populations increased, much of this coast has been subject to infill and seaward extension for housing, recreation and industrial development. This has led to degradation of the highly productive intertidal and shallow subtidal marine ecosystems upon which fisheries depend. Further degradation can be expected with future sea level rise, as high evaporation rates will induce hyper saline conditions. Rather than building out into the sea using dredging and infill, an alternative approach is to construct cities on land, safely above future high water levels, by excavating saline desert of low productivity to create marine waterways. Sabah Al-Ahmad Sea City in Kuwait was first connected to the sea in 2004 and, with 3 phases completed, now has 84 km of shoreline in the desert. The waterway system was modeled before excavation and relies solely upon tides and wind for seawater circulation. To date seawater quality has been excellent, meeting all criteria demanded by the Environment Public Authority. Within the waterways, a full range of man-made marine habitats have been created. These include intertidal beaches, tidal flats, mangrove and salt marshes on islands, together with subtidal sand and rock benthic habitats. These have been monitored with daily physical and annual biological surveys. Importantly, this data provides new information on the natural colonization rates and development of Gulf soft substrate intertidal and subtidal marine communities. Within 5 years of opening to the sea, all artificially created marine habitats have a species richness and abundance close to, or exceeding, that of similar open sea natural habitats in Kuwait. Over 1000 species of macrobiota now exist within the desert waterways including 100 species of fish and shellfish. Present work describes the development of these marine communities and provides a baseline for recruitment rates of Gulf marine fauna into non-polluted habitats.

Analysis of the effects of different storm events on shoreline dynamics of an artificially embayed beach

ABSTRACTA five‐year dataset of Argus‐derived mean intertidal positions has been analysed to characterize the shoreface variability in a beach protected by a system of groynes and a parallel low crested structure (Lido di Dante Ravenna, Italy). For the period 2004–2009, 84 intertidal beach bathymetries and shorelines at the zero sea level were used as indicators to assess beach changes in between a number of selected surveys and to determine characteristic patterns of the beach response to storm events from different directions. Variations in the shoreline at the zero sea levels have been quantified and analysed in conjunction with nearshore wave conditions and provenance linked to storm events. These fall into two categories: (1) storm events occurring during Bora (north‐eastern) wind conditions and (2) storm events occurring during Scirocco (south‐eastern) wind conditions. The results show that, apart from main beach advances of the whole protected beach due to nourishments periodically carried out, a marked variability is observed among the four sub‐cells into which the shoreface behaviour has been separately analysed. In particular, a dependence of beach rotation in the ‘artificially embayed’ area on the substantially bi‐directional wave climate has been shown: Bora and Scirocco storm events produce shoreline rotation in counterclockwise and clockwise directions, respectively, due to the occurrence of longshore currents in the opposite direction in the nearshore. An attempt was made to correlate the shoreface dynamics for the main rotation events (14 selected ones) to the wave attack intensity (as the total energy flux due to storm events). A relationship seems to occur (for each storm category) between the shoreline displacements estimated for each sub‐cell and the total energy flux computed for inter‐survey periods, supporting the occurrence of a link between the observed morphological changes and the hydrodynamic forcing associated with storm events in the five‐year monitoring period. Copyright © 2011 John Wiley & Sons, Ltd.

Dynamics of bacterial community exposed to hydrocarbons and oleophilic fertilizer in high-Arctic intertidal beach

Exposure of pristine microbial environments to hydrocarbon contamination stimulates growth of the initially small fraction of indigenous hydrocarbon-degrading bacteria. Custom-made oleophilic fertilizers have been demonstrated to promote oil bioremediation by boosting this proliferation. In the present study, the temporal dynamics of the bacterial community structure and the individual influences of hydrocarbons and an oleophilic fertilizer in shaping the community structure was explored during a 78 days bioremediation experiment in a high-Arctic intertidal beach environment. A combination of cultivation-independent 16S rRNA gene length-heterogeneity polymerase chain reaction (LH-PCR) profiling and identification of hydrocarbon-degrading isolates based on partial 16S rRNA gene sequences was employed. LH-PCR community profiles in the fertilizer alone and fertilized kerosene plots were largely indistinguishable throughout the experimental period, while kerosene alone plots showed a markedly different composition of dominant groups. This pointed to the fertilizer as the more decisive factor in shaping the community structure. Most prominent LH-PCR fragments which emerged after kerosene or fertilizer addition could be provisionally assigned to bacterial taxa through coinciding LH-PCR fragment lengths with hydrocarbon-degrading isolates obtained from the same type of experimental units. However, a few quantitatively significant LH-PCR groups had no counterparts among the cultivated bacteria. One of these was affiliated to a hitherto unspeciated subgroup within the Alkanindiges/Acinetobacter clade of Moraxellaceae by a 16S rRNA gene cloning approach.

The use of artificial neural networks to analyze and predict alongshore sediment transport

Abstract. An artificial neural network (ANN) was developed to predict the depth-integrated alongshore suspended sediment transport rate using 4 input variables (water depth, wave height and period, and alongshore velocity). The ANN was trained and validated using a dataset obtained on the intertidal beach of Egmond aan Zee, the Netherlands. Root-mean-square deviation between observations and predictions was calculated to show that, for this specific dataset, the ANN (εrms=0.43) outperforms the commonly used Bailard (1981) formula (εrms=1.63), even when this formula is calibrated (εrms=0.66). Because of correlations between input variables, the predictive quality of the ANN can be improved further by considering only 3 out of the 4 available input variables (εrms=0.39). Finally, we use the partial derivatives method to "open and lighten" the generated ANNs with the purpose of showing that, although specific to the dataset in question, they are not "black-box" type models and can be used to analyze the physical processes associated with alongshore sediment transport. In this case, the alongshore component of the velocity, by itself or in combination with other input variables, has the largest explanatory power. Moreover, the behaviour of the ANN indicates that predictions can be unphysical and therefore unreliable when the input lies outside the parameter space over which the ANN has been developed. Our approach of combining the strong predictive power of ANNs with "lightening" the black box and testing its sensitivity, demonstrates that the use of an ANN approach can result in the development of generalized models of suspended sediment transport.

Efficiency of an integrated habitat stabilisation approach to coastal erosion management

The present paper describes the technical solution adopted for habitat stabilisation as an integrated approach to erosion mitigation aimed at improving ecological and environmental aspects of the tropical and subtropical shorelines. Any man-made structure on the beach could have an environmental impact on the habitat and the associated biota. However, when the habitat is considered in the design process, a coastal erosion management plan can provide an effective means of coastline stabilisation and habitat enhancement. Therefore, in this study a combination of low crested breakwaters and a mangrove restoration plan was applied to an intertidal beach on the west coast of the state of Selangor, Malaysia. The study was aimed at protecting the beach and enhancing the habitat. The presence of the breakwater resulted in sediment deposition on the beach and the substrate elevation increased to a height appropriate for mangrove establishment. The calm area protected by the breakwater was also conducive to restoration work on the exposed coast. The approach provided suitable conditions for coastal rehabilitation, facilitating the natural recovery process of the coastal ecosystem.

Bioecology of the Ghost CrabOcypode quadrata(Fabricius, 1787) (Crustacea: Brachyura) Compared with Other Intertidal Crabs in the Southwestern Atlantic

Data sets on the natural dynamics of beach ecosystems arc scarce and fragmentary. Such data arc necessary for implementing more efficient monitoring programs that quantify the dynamics of key ecological attributes on sandy beaches. This article contributes to the bioecology of ghost crabs from subtropical Praia Brava, Itajaí, Santa Catarina. Ocypode quadrata occurs in sandy beaches along the tropical-temperate western Atlantic, from Rhode Island (US) to Rio Grande do Sul (Brazil). During 14 consecutive months, a total of 649 specimens were captured: 255 females (39%), 241 males (37%), and 153 juveniles of undetermined sex (24%). Highest densities were recorded in June and November, with a total of 1,900 burrows distributed along the beach (56.95%) and dunes (43.05%). Sixteen natural diet items were identified for this crab, with a larger participation of Apis spp. (38.97% of relative volume). In the local food web, the ground-burrowing owl Speotyto cunicularia was the main crab predator. This article indicates that the ghost crab represented the second most consumed food item of the owl (29.24%), only surpassed by rodent remains, which occupied 50.32% of its stomach volume. The natural diet and the main predator of the ghost crab had not been observed along the coast of Brazil. Knowledge of natural diet is fundamental for understanding distribution patterns, migrations, and molting cycles. Further information on population structure (abundance peaks in spring and summer; a negative allometric growth pattern), spatial distribution (predominance of females in August and May, and of males in July; size of specimens increases toward higher intertidal levels), sexual proportion throughout the year (reproduction is continuous), form and disposition of burrows (reduced abundance toward the higher tidal levels), and relative importance for the diet of the main predator (both predator and prey arc nocturnal) may be used as instruments for evaluating the occupational impact and for conserving natural dune and beach environments along sandy beach ecosystems. In conclusion, ghost crabs provide an alternative source of food for the ground-burrowing owl, a predator that may represent an important population controlling factor, other than the human-induced impacts on sandy beaches. Although burrowing crabs are the most conspicuous and ecologically important invertebrates of intertidal beaches along tropical and temperate regions, factors that regulate abundance arc still controversial, whereas the biotic community interactions in sandy beaches remain barely known.

Swash zone sediment transport, step dynamics and morphological response on a gravel beach

State-of-the-art morphodynamic field data were collected from Slapton Sands (UK), a fine-gravel beach ( D 50 = 2–10 mm), over a 10-day period under a range of wave–tide conditions, comprising a mixture of southerly swell and easterly wind waves ( H s = 0.5–1 m; T s = 4–8 s; tide range = 3–4 m). Over the field period, the upper beach experienced accretion and berm formation during tides with low steepness, swell-dominated wave conditions ( H/ L < 0.01), and underwent erosion during tides dominated by high steepness wind waves ( H/ L > 0.01). Surprisingly, the intertidal beach showed an opposite trend with sediment losses under swell conditions and an increase in sediment volume due to wind waves, and suggests that upper beach morphological change can be decoupled from the overall sediment budget. A submerged accretionary feature (the beach step) grew and migrated onshore on the rising tide, typically reaching a maximum relief of around 0.5 m, then gradually decreased in prominence while migrating offshore as the tide fell, resulting in little net morphological change. The step was better developed during the falling tide than the rising tide and, through its control on the swash hydro- and sediment dynamics, the step had a significant effect on the development of the berm. Swash flow velocities under the conditions measured were often in excess of 2 m s − 1 for both the uprush and the backwash. Onshore mean flows occurred in the upper swash region (< 40% inundation), while the lower swash region (> 40% inundation) was characterised by offshore mean flows. Swash infiltration losses in the swash zone increased from 40% in the lower swash region to 100% in the upper swash region. The most energetic swash flows and the strongest offshore mean flows occurred at the transition between swash zone and surf zone (90–100% inundation).

Automated mapping of the intertidal beach bathymetry from video images

This paper presents a fully automated procedure to derive the intertidal beach bathymetry on a daily basis from video images of low-sloping beaches that are characterised by the intermittent emergence of intertidal bars. Bathymetry data are obtained by automated and repeated mapping of shorelines from video time exposure images for different (tidal) water levels (Aarninkhof, S.G.J., Turner, I.L., Dronkers, T.D.T., Caljouw, M., Nipius, L., 2003. A video-based technique for mapping intertidal beach bathymetry. Coastal Engineering 49, 275–289; Plant, N.G. and Holman, R.A., 1997. Intertidal beach profile estimation using video images. Marine Geology 140, 1–24.). The developed procedure handles intelligent selection of a shoreline search area and unsupervised quality control of the obtained bathymetry data. The automatically retrieved beach bathymetries compare very well to bathymetries derived from the original manual mapping procedure and to ground truth data points (DGPS).

Characterization of methicillin-resistant Staphylococcus aureus and methicillin-resistant coagulase-negative Staphylococcus spp. isolated from US West Coast public marine beaches

The aim of this study was to isolate and characterize methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative Staphylococcus spp. (MRCoNS) from marine water and intertidal beach sand from public beaches in Washington State, USA. Fifty-one staphylococci from Washington State beaches were characterized using antimicrobial susceptibility testing, carriage of acquired tetracycline and/or macrolide resistance genes, staphylococcal cassette chromosome mec (SCCmec) typing, the BBL Crystal Gram-Positive ID System and/or 16S rRNA sequencing, coagulase test and multilocus sequence typing (MLST) for MRSA. Five multidrug-resistant MRSA SCCmec type I, of which three were MLST type ST45, one ST59 and one a new MLST type, ST1405, plus one susceptible non-typeable (NT) MRSA ST30 were characterized. Thirty-three MRCoNS isolates, representing 21 strains from 9 Staphylococcus spp., carried a range of SCCmec types [I (2), II (6), III (3), V (2), I/II (1) and NT (7)] and varied in their antibiotic susceptibility to other antibiotic classes and carriage of acquired tetracycline/macrolide resistance gene(s). MRSA and MRCoNS donors co-transferred tet(M) and erm(A) genes to an Enterococcus faecalis recipient at a frequency of 10(-8). This is the first report of MRSA and MRCoNS isolated from marine water and intertidal beach sand. The MLST types and antibiotic carriage of five MRSA isolates were similar to hospital MRSA isolates rather than US community-acquired MRSA isolates. Our results suggest that public marine beaches may be a reservoir for transmission of MRSA to beach visitors as well as an ecosystem for exchange of antibiotic resistance genes among staphylococci and related genera.

First account of apochlorotic diatoms from intertidal sand of a south Florida beach

During the period January to December 2004, monthly intertidal sand samples were collected from John U. Lloyd State Park beach, Florida. This study is the first to report on spatial and temporal distributions of heterotrophic (apochlorotic) diatoms in a sub-tropical beach, or indeed any sandy beach. Two non-pigmented, apochlorotic diatom morphotypes (strains III and IV) were consistently isolated from two intertidal beach sites and neither conformed to the morphologies of described species. Apochlorotic diatoms were found throughout the year and formed significant peaks in April, attaining total diatom counts of 71.1 and 94.9 cells g −1 wet sand, for the upper tidal zone and lower tidal zone, respectively. Valve morphology is described in detail for the two diatom morphotypes isolated from the beach sites (strains III and IV). Growth responses to changes in salinity (reflecting those of the intertidal zone) were examined in the laboratory for these diatoms. Both morphotypes were euryhaline, tolerating salinities between 10 and 50, and maximum growth rates were achieved at salinities between 20 and 40. Diatoms grew equally well whether grown in the light or the dark and showed no evidence of pigments when viewed by epifluorescence microscopy. The ability of diatoms to burrow into agar and carrageenan at different concentrations was tested. Both morphotypes were observed to develop burrows through non-nutrient agar up to twice the standard concentration (30 g agar l −1). The ease with which these heterotrophic diatoms formed burrows suggests that they were digesting these complex carbohydrates (i.e. phycocolloids) as a nutrient source. Strain IV, however, failed to burrow in a different phycocolloid, carrageenan. Similar degradative actions in the field might have implications for the breakdown of recalcitrant materials or allow diatoms to effectively compete with bacteria for carbon and nutrients.

Photochemical production of hydrogen peroxide in size-fractionated Southern California coastal waters

Hydrogen peroxide (H 2O 2) photochemical production was measured in bulk and size-fractionated surf zone and source waters (Orange County, California, USA). Post-irradiation (60 min; 300 W ozone-free xenon lamp), maximum H 2O 2 concentrations were ∼10 000 nM (source) and ∼1500 nM (surf zone). Average initial hydrogen peroxide production rates (HPPR) were higher in bulk source waters (11 ± 7.0 nM s −1) than the surf zone (2.5 ± 1 nM s −1). A linear relationship was observed between non-purgeable dissolved organic carbon and absorbance coefficient (m −1 (300 nm)). HPPR increased with increasing absorbance coefficient for bulk and size-fractionated source waters, consistent with photochemical production from CDOM. However, HPPR varied significantly (5×) for surf zone samples with the same absorbance coefficients, even though optical properties suggested CDOM from salt marsh source waters dominates the surf zone. To compare samples with varying CDOM levels, apparent quantum yields ( Φ) for H 2O 2 photochemical production were calculated. Source waters showed no significant difference in Φ between bulk, large (>1000 Da (>1 kDa)) and small (<1 kDa) size fractions, suggesting H 2O 2 production efficiency is homogeneously distributed across CDOM size. However, surf zone waters had significantly higher Φ than source (bulk 0.086 ± 0.04 vs. 0.034 ± 0.013; <1 kDa 0.183 ± 0.012 vs. 0.027 ± 0.018; >1 kDa 0.151 ± 0.090 vs. 0.016 ± 0.009), suggesting additional production from non-CDOM sources. H 2O 2 photochemical production was significant for intertidal beach sand and senescent kelp (sunlight; ∼42 nM h −1 vs. ∼5 nM h −1), on the order of CDOM production rates previously measured in coastal and oceanic waters. This is the first study of H 2O 2 photochemical production in size-fractionated coastal waters showing significant production from non-CDOM sources in the surf zone.

Several Cases of Disseminated Neoplasia in Mussels Mytilus edulis (L.) in Western Long Island Sound

Eight cases of disseminated neoplasia were found among 540 specimens of Mytilus edulis collected from an intertidal beach in Connecticut in western Long Island Sound. This was unusual, because disseminated neoplasia is very rare in M. edulis but causes epizootic mortalities in another mussel species, M. trossulus. According to histology, mussels showed a continuum of disease progression, from early stages with a few anaplastic cells around the stomach epithelium to more advanced cases with multiple foci of neoplastic cells in the tissues, finally to terminal cases with profuse infiltration of neoplastic cells in all tissues. Flowcytometric hemocyte analyses were performed to compare immune functions between neoplastic and healthy mussels. Circulating hemocytes from the neoplastic mussels showed significantly less phagocytosis and significantly more apo- ptosis than hemocytes from the healthy mussels. Hemocyte cell density measured by flow cytometry increased in the hemolymph with progression of the disease on histological sections. In situ hybridization was performed to detect apoptosis also on paraffin sections. There were more apoptotic neoplastic cells in the early stages of the disease than in the later stages. These observations suggest the need for further studies on apoptosis-regulating genes to explain differences in susceptibility to neoplasia of different Mytilus species, and the role of apoptosis in the progression of disseminated neoplasia.

An evaluation of two alongshore transport equations with field measurements

The performance of two well-known equations to predict the depth-averaged alongshore suspended sediment flux [Van Rijn, L.C., 1984. Sediment transport, part II: suspended load transport. Journal of Hydraulic Engineering 110, 1613–1641; and Bailard, J.A., 1981. An energetics total load sediment transport model for a plane sloping beach. Journal of Geophysical Research 86, 10938–10954] was assessed by comparing predictions with 2306 field estimates based on a vertical stack of three optical backscatter sensors and a single electromagnetic flow meter. The observations were collected at four cross-shore positions on the intertidal beach of Egmond aan Zee, the Netherlands, during calm to storm conditions, with the offshore significant wave height peaking at 3.7 m. Measured hydrodynamics were employed in the computations of both models. Also, default parameter values were used without calibration to the data. We found that both models underpredicted the observations. Overall, the Van Rijn model outperformed the Bailard model, with about 70% of the model prediction lying between 1/5 to 5 of the observations under energetic conditions. For the Bailard model this was only about 20%. The performance of the Van Rijn model is, however, sensitive to the wave-related roughness, one of its highly uncertain free parameters. This may allow for an easy calibration when estimates of the depth-averaged alongshore sediment flux are available but may lead to serious errors in situations without data to constrain the predictions. We suspect that the discrepancy between the observations and model predictions is due to an overestimation of the observed fluxes (high turbidity, air bubbles) and an underestimation of the modeled fluxes because of missing physics related primarily to breaking waves.

MORPHOLOGIAL PLASTICITY OF HALODULE SPECIES IN RESPONSE TO DIFFERENT ENVIRONMENTS

Halodule species is widely distributed along the south and east coasts of Peninsular Malaysia, Sabah and Sarawak. Five locations were selected for the study based on different habitat characteristics; sub-tidal shoal (Merambong-2 sites; Tg. Adang Laut-2 sites), coastal lagoon (Merchang-2 sites), inter-tidal beach front (Lawas-l site) and reef atoll lagoon (Pulau Layang-Layang-l site). Samplings and collections of Halodule plants were conducted from August 2002 until May 2004. The result of the study found that Halodule species are found at depth.of -1.5 to-2.7 m in various habitats with substrates from sandy, coralline sand, calcareous sandy-mud, sandy-mud to muddy substrates and can survive in a wide range of salinity, 18-34 psu. They adapt in th,e different environmental conditions through changes in morphology. Water depth (associated with ambient light), sediment type and sediment depth have an influence on the morphology of vegetative components e.g. leaf length, leaf width, erect stem length and rhizome growth pattern. Leaf tip morphology was not affected by habitat types and the environmental characteristics. Leaf tips for H. uninervis are similar in morphology between young and mature leaves. Leaf tips for H. pinifolia varied with an obvious differences between young and mature leaf tips.