A comprehensive study involving 52 microtidal beaches spanning from reflective to dissipative states and located in tropical, subtropical and temperate regions in the Atlantic, Pacific and Indian oceans was carried out to unravel the relative roles of latitude and beach morphodynamics in determining beach macrobenthic species richness, abundance, biomass and mean individual body sizes. Since beach slope is one of the most important factors controlling beach fauna, a model based on beach geometry was applied to the sub-aerial beach deposit to understand the role of physical factors in predicting equilibrium beach slopes. Additionally, it was tested if the occurrence of beach types is related to latitude, and how physical factors change with morphodynamics and latitude. The beach morphometric model makes three assumptions: 1) that the cross-section of a beach deposit is equivalent to a right-angled triangle, 2) that the physical hydrodynamic factors (wave height and spring tide amplitude) and the beach deposit characteristics (sand grain size, beach slope and width) are interchangeable with their geometric counterparts producing an equation to explain beach geometry, and 3) that the predicted beach slope is in equilibrium with the hydrodynamic and sedimentological forces. The equation for predicting beach slope was derived and then tested against field data collected over 52 beaches. The predicted slopes were not significantly different from the observed slopes of the studied natural beaches. However some estimated slopes were different than observed ones. Possible sources of deviation between calculated and observed slopes may be the systematic sampling errors associated with field data. Alternatively, observed slopes could be the result of past hydrodynamic conditions, explaining the differences with the slopes calculated by the beach morphometric model, which assumes a state of equilibrium between beach slope and hydrodynamic conditions. A higher correlation of beach faunal structure with observed slopes rather than with present hydrodynamic conditions could then be indicative of faunal responses to previous hydrodynamic conditions in the same way was the observed slopes. The beach morphometric model could therefore be also useful in predicting faunal responses to changing hydrodynamic conditions. Since the model does not consider wave period, it is concluded that further tests should be done using laboratory and time-series field data and incorporating the role of wave period and beach permeability to ascertain its predictive value. Tropical regions had significantly more beaches in a reflective state than temperate and subtropical regions. Some tropical beaches were fronted by coral reefs, which not only provided coarse carbonate particles, but also additionally dissipated the low wave energy present in these climatic areas. Only one dissipative beach with high energy was found in the tropics, in southeast Madagascar. Temperate and subtropical regions, on the other hand, were dominated by dissipative beaches with medium to fine sands. Open oceanic reflective beaches were non-existent in the subtropics and rare in temperate regions, only occurring in estuaries, enclosed bays or on islands facing the continent. Intermediate beaches were more common in the subtropics but also occurred frequently in the other two regions, having higher energy in temperate regions. Reflective beaches had significantly steeper slopes, coarser sands, smaller waves and shorter swash lengths when compared to dissipative beaches. Additionally, reflective beaches were narrower, had deeper water tables and in consequence shorter saturation zones. Wave periods and surfzone widths were on average larger on dissipative than on reflective beaches. The frequency of occurrence of beach types is therefore related to the climatic signature of each latitude. Mid latitudes would be predicted to have more dissipative beaches with large and long waves because of their proximity to the storm generating belt around 50-60° S - these beaches will have a predominantly finer sands because of the input by rivers in rainy areas. Lower latitudes will have more reflective beaches due to a modal low energy wave climate and also because of the presence of inshore and offshore biotic structures such as coral reefs that dissipate even more the energy from the waves. Tropical and subtropical regions had larger marine species pools than temperate regions. After controlling for biogeographical differences in total species pool, dissipative beaches were on average significantly richer than intermediate and reflective beaches. Crustaceans were also more diverse on dissipative beaches, this difference being not significant for either molluscs or polychaetes. Significant relationships were found between total beach species richness (with or without terrestrial species), crustacean and mollusc species richness with beach morphodynamics as represented by the Dean’s index. Indices incorporating the role of tide, such as BSI, were less important in predicting species richness on the microtidal beaches studied here. Several other physical factors were also significantly correlated with species richness, the most important being the Beach Deposit Index, i.e. BDI, a composite index of beach slope and grain size. The highest correlation was between BDI and relative species richness, i.e. local beach species richness / regional species richness. Total regional marine species richness was higher in Madagascar and North Brazil (tropical beaches) than in Southeast Brazil (subtropical), or the West Coast of South Africa and South-Central Chile (temperate beaches). Not only was the pool of species capable of colonizing beaches richer in tropical and subtropical regions, but also local diversity of each morphodynamic beach type was higher among tropical beaches than their temperate counterparts. Although the results of this study agree with the predictions of the swash exclusion hypotheses, several reflective and intermediate beaches had higher species richness than predicted before and this seems to be linked to the presence of finer sediments and a less turbulent flow for larvae to settle. It is concluded that beach species richness is not necessarily controlled by one major morphodynamic parameter; this control is complex and probably involves multiple interacting biotic (biological interactions) and abiotic (e.g. grain size, wave height, beach slope and width, water table) factors. Species richness seems to be controlled on two different scales: on an evolutionary one where tropical and subtropical regions have higher regional and local diversity due to higher speciation rates; and on an ecological scale, where fine grained sand beaches have their carrying capacity enhanced by higher larval settlement rates and survival of recruits towards adulthood. On average dissipative beaches had higher total densities and macrofaunal abundances than reflective ones. Crustaceans, terrestrial species and cirolanid isopods such as Excirolana spp. were also more abundant on dissipative beaches. The difference was not significant for molluscs and polychaetes. Significant relationships were found between total abundance, crustacean species richness and beach morphodynamics as represented by the Dean’s index. Again, BSI was less important than individual physical factors in determining faunal abundance on the studied microtidal beaches. Several other physical factors were also significantly correlated with abundance, the most important being the Beach Deposit Index (BDI). The highest correlation was between BDI and total macrofaunal abundance. Factors related to surf zone processes, and possibly productivity, were highly correlated with total community, crustaceans, Excirolana spp. and terrestrial species abundances. The abundances of polychaetes and molluscs were better correlated with factors related to the beach deposit (BDI, slope, grain size and water table depth). Significant differences were observed between latitudinal regions for the average beach and also for each beach type. In general temperate beaches harboured larger community densities and abundances, and also crustacean, Excirolana spp. and terrestrial abundances. Mollusc and polychaete abundances were larger on subtropical and tropical beaches. The control of abundance on a sandy beach is complex and involves multifactorial processes at evolutionary and ecological scales. At evolutionary scales animals seem to attain higher abundances in the region where they first evolved, e.g. amphipods and isopods in temperate regions. At ecological scales they attain higher abundances where productivity is higher (total macrofaunal, crustaceans, Excirolana spp., terrestrial spp.) or where the settlement environment is more benign (molluscs and polychaetes). Dissipative beaches supported larger average and total community biomass than reflective beaches. Crustaceans, terrestrial species and cirolanid isopods such as Excirolana spp. also had larger biomass on dissipative beaches. The difference was not significant for molluscs and polychaetes. Significant relationships were found between the biomass of community and taxonomic groups with beach morphodynamics as represented by the Dean’s morphodynamic index. On the microtidal beaches studied here, BSI was less important than other morphodynamic indices and single physical factors in determining faunal biomass and mean individual body size. Surf zone characteristics such as wave height, period and surf zone width had the highest correlations with community, crustacean.

Until recently most sandy beach studies have made use of snapshot samples but the validity of this approach has been widely questioned. In this study we attempt to resolve this issue by repeatedly sampling two beaches using a stratified random design. Three sampling sessions took place, each approximately six months apart. The three sites on the first beach were selected according to the type of beach (reflective, intermediate and dissipative) with each morphological type duplicated on the second beach. Many of the physical variables measured had significant differences between the sampling sessions but only a few were significantly different between the Sites. Very few of the individual physical variables had significant relationships with the sandy beach macrofaunal abundance and density. However, composite indices had a greater number of significant relationships with the macrofaunal abundance and density. Also very few significant relationships were seen between the species richness and the physical variables of the beaches studied. Effluent line crossing frequency was the only physical variable that could predict species richness but it was considered a weak predictor. Changes in the zonation patterns within and between beaches were also investigated. The highest concentration of taxa and individuals was found near the low-water mark with a gradual reduction of both towards the high-water mark. Some of the sandy beach community variables (abundance, density and species richness) showed significant difference between the sampling sessions but no significant differences were seen between the two beaches. The presence of three zones was noted using MDS plots and Cluster diagrams. However, using a SIMPER analyses, four zones with the possibility of a fifth was noted.

Abstract Not Provided / Thesis / Bachelor of Science (BSc)

The intertidal flora and fauna of S.E. Australia (Robe, South Australia to S. New South Wales, including Tasmania) is described in terms of its horizontal and vertical distribution. A detailed account of intertidal zonation, on the central Victorian coast and Bass Strait islands, is included. Environmental features are discussed and sea temperature data for Pt. Lonsdale is presented. / Analysis of the marine flora in S.E. Australia suggests that the concept of separate biogeographic provinces in this region is invalid and the flora is best interpreted as a continuum.

Thesis (Ph. D.)--University of Melbourne, 1972. / Includes bibliographical references.

The objective of this research was to improve our understanding of how changes in the environment affect ecological processes. Change detection is often confounded by the large variation found in ecological data due to the difficulty of finding replicates in nature. Intertidal communities were chosen for studies of biophysical interactions because the physical gradients are very strong, thus creating complex systems within spatial scales that are easily sampled. The selection of replicate beach habitats was the first step in designing a sampling protocol for comparative analyses of nearshore community structure. A high resolution shoreline partitioning model was developed to quantify the physical attributes of homogeneous shoreline segments and to statistically cluster replicate segments. This model was applied at 3 locations in Washington State. A portion of the south shore of San Juan Island was partitioned and the physical attributes quantified. Three groups of rocky segments differing only in slope angle were selected for biological sampling. The objective was to test the fidelity of macroalgal and invertebrate populations to replicate bedrock shore segments. The results showed that community structure and population abundances were more similar within groups of replicate segments (similar slopes) than among groups (different slopes). In South Puget Sound, community structure was compared to test for a deterministic organization of communities among replicate soft sediment beaches in an estuary. The results showed that replicate beach segments support similar communities, that communities become less similar as the distance between replicates increases, and that replicates within or among nearshore cells with similar temperature and salinity support communities that are more similar than replicates among cells with different water properties regardless of distance. On the outer Olympic coast, community comparisons were made among 9 sand beaches over a shoreline distance of 250 km. The results show that these communities are similar within segments and within nearshore cells, but because of population abundance fluctuations, the communities were different among cells and among years. This study shows that processes determining patterns in nearshore habitats can be quantified, which is a significant contribution to studies of habitat distribution and the siting of marine preserves. / Graduation date: 2000

Field experiments and observations were used to define the functional roles and relationships of species in the rocky mid-intertidal community at Pelican Point in the northern Gulf of California. This approach provided resolution of the influences of grazing, predation, competition, and abiotic factors on community structure, and of the direct and indirect effects involved in species interactions. Competition for space, apparently via space pre-emption, between the barnacle Chthamalus anisopoma and encrusting algae of the genus Ralfsia was consistently evident. Grazing by the limpet Collisella strongiana was shown to limit algal abundance and bring about the replacement of Ralfsia by Chthamalus. Chthamalus also excluded Collisella from the rock surface. Predation on Chthamalus by the thaidid gastropod Acanthina angelica increased the abundances of both Ralfsia and Collisella. Some of the temporal variations in community structure observed during this study were clearly linked to variations in the abundances of Acanthina and Collisella and the above interactions. This relatively simple community, existing in what seems a rigorous physical environment, was characterized by strong, highly interdependent biological interactions. Indirect effects were consistently important in species interactions. An intriguing result of this study was the emergence of indirect mutualism between Acanthina and Collisella; this interaction appears to contribute to the persistence and continuing influences of both consumer species, and hence may be of major importance in the organization of this community. The zonation of the barnacles Chthamalus anisopoma and Tetraclita stalactifera at Pelican Point and elsewhere in the Gulf was examined in a test of recent ideas relating ecological and evolutionary patterns in barnacles to morphology and competition for space. Experiments and observations indicated the restriction of Tetraclita to the upper part of the shore by competition from Chthamalus, with Tetraclita able to survive above Chthamalus by virtue of greater tolerance to exposure. These results were in direct opposition to the presumed competitive dominance of large, rapidly-growing, tubiferous barnacles like Tetraclita. Comparisons with results from other shores suggested that numerical dominance goes hand-in-hand with competitive dominance in acorn barnacles. Morphological differences appear to be of minor importance.

No description available.

The <i>Jaera albifrons </i>species group of intertidal isopods is characterised by strong sexual isolation mediated by female discrimination against heterospecific male tactile-stimulatory courtship behaviour.  This is the first study to examine the genetic basis of traits involved in tactile mediated sexual isolation.  To determine the genetic architecture of male secondary sexual characters (species-specific hair traits carried on the legs of males and a carpus leg-segment shape difference) associated with sexual isolation, experimental hybrid populations of <i>J. albifrons </i>and <i>J. ischiosetosa </i>were used to construct AFLP-based genetic linkage maps.  A number of chromosomal differences (Robertsonian fusions) between the parental species were shown to be associated with reduced hybrid fertility.  A quantitative trait locus (QTL) mapping study revealed that the number of hairs and carpus shape have a complex genetic basis, involving a number of QTL showing dominance, epistasis and possible pleiotropic effects.  These QTL mapped largely to putative regions of restricted recombination, especially chromosomal rearrangements. The qualitative difference, however, was shown to be controlled by a single (or several closely linked ) QTL that did not map to a region of restricted recombination.  These findings suggest that introgressive hybridisation played an important role in speciation in the <i>J. albifrons </i>species group and that chromosomal rearrangements allowed incipient species to persist in the face of ongoing gene flow.  The extensive sharing of a single 16S rDNA mitochondrial haplotype supports the assertion that gene flow has been important.  The reinforcement of premating isolating by natural selection against costly hybridisation is suggested as the mechanism of speciation between these species.  The complete dominance of the <i>J. albifrons </i>allele at the QTL controlling the qualitative difference between the species supports this model of speciation.

As an important technique for corrosion control in marine environment, Cathodic Protection (CP) should be applied with a full understanding of environmental conditions and a good consideration of current requirements. Early studies on different kinds of steel specimens in the intertidal zone show severe corrosion losses. Nevertheless, there is evidence that CP can work in these regions of a steel structure because electrolyte pathway can remain some time on thin wetted surfaces when tides recede. This research aims to study corrosion activities and their behaviour under the influence of CP in a thin layer of electrolyte as a simulation of the inter-tidal zone. By means of a mechanical vibrating probe, Scanning Vibrating Electrode Technique (SVET) may be used to study local activities at coating defects in a thin electrolyte layer. The effect of CP on the local currents at the defect site was confirmed by SVET and, significantly, the development of calcareous films under these conditions in seawater was also observed. Such films are found to be effective in the absence of cathodic polarisation and only failed after damage. In order to explore the performance of applying CP, a Finite Element (FE) model of electrically connected zinc and steel samples beneath a specific thickness of electrolyte has been created, with full polarisation curves implemented for each metal based on experimental results obtained. The influence of the electrolyte conductivity and the geometry of the electrodes has also been considered. A comparison can then be made between experimental investigation and computational modelling of this corrosion cell. Epoxy-coated and uncoated mild steel samples obtained in the simulated tidal facility were also investigated. The formation of calcareous films was confirmed. Calcareous films were protective under these intermittent wetting conditions. Techniques used to understand the performance include optical observation, Scanning Electron Microscopy (SEM) together with Energy Dispersive X-ray (EDX) and X-ray Diffraction (XRD) analysis.