Mean High Water Spring Research Articles

A National‐Scale Coastal Flood Hazard Assessment for the Atoll Nation of Tuvalu

AbstractAtoll nations such as Tuvalu are considered to be amongst those most vulnerable to the effects of climate change. Here we present a national‐scale coastal flood hazard assessment for Tuvalu based on high‐resolution Light Detection and Ranging (LiDAR) topography and bathymetry. We follow a fully probabilistic approach, considering sea level anomalies, tides, and extreme wave conditions from a mixed climate (i.e., from distant extra‐tropical storms and local tropical cyclones). Nearshore processes such as wave setup and runup are also accounted for. Hazard maps were calculated for the present sea level, as well as for sea level rise projections corresponding to different shared socioeconomic pathways (SSP2 4.5 and SSP5 8.5) and time horizons (2060 and 2100). With a mean elevation of 1.55 m above mean sea level (1.37 m above mean high water spring) >25% of land area is inundated once every 5 years and >50% of land area floods once every 100 years nationally. Results indicate that present day 1‐in‐50 years floods (>45% of land area flooded) will occur more than once every 5 years by 2060 (annual exceedance probability >20%), even under the moderate SSP2 4.5 sea level rise projections. Results of this study highlight the pressing need for ambitious and large‐scale adaptation solutions which are commensurate with projected sea level rise and marine hazard impacts. The methodologies presented in this paper can easily be applied to other low‐lying islands in the tropical Pacific, where mixed climates (i.e., regular and TC conditions) and non‐linear nearshore processes dominate extreme water levels and flooding.

An improved method for computing tidal datums

Tidal datums are reference water levels describing the characteristic periodic variations in sea surface elevation relative to a vertical datum at a particular location. There are two common approaches for computing tidal datums: 1) the harmonic constituent approach, and 2) the peaks approach. Using a new method based on the peaks approach, tidal datums were computed and compared with theoretically equivalent constituent-based datums for a global set of 206 coastal tide gauges. The peak-based method described herein identifies high and low water turning points and then systematically classifies each according to semidiurnal, diurnal, and spring tidal cycles. The classified peaks and troughs in both predicted (excluding non-astronomical influences) and observed water level time series were averaged over a 19-year period. Tidal datums, such as Mean High Water Springs and Mean Higher High Water, are relied upon by many coastal authorities to define the tidal component of coastal inundation thresholds. Differences of >20 cm were found across tidal regimes and continents, demonstrating that the peaks approach is preferable over the constituent approach where such differences are non-negligible. An open source Tide Peaks Toolbox for use in MATLAB is presented for computing peak-based datums from any high frequency water level observation record.

Field Investigation into Abrasion of Concrete at a Coastal Stepped Revetment: A U.K. Case Study

Although concrete abrasion damage is a major maintenance challenge for coastal structures fronted by beaches with hard coarse sediments, there are no readily available field studies that have measured abrasion damage of known concrete mixtures under defined exposure conditions. The objective of this investigation is to evaluate the abrasive exposure conditions of the concrete revetment armour units at Cleveleys on the Fylde coast of the U.K. and examine the feasibility of using terrestrial laser scanning (TLS) to measure concrete abrasion damage in field conditions. It was found that the concrete elements at Cleveleys are exposed to a macro-tidal environment, which experiences significant wave heights that vary from 0.42 to 1.92 m, whilst the peak wave periods range from 3.7 to 6.5 s. The beach sediments have a mean size of 26 mm and are moderately sorted. TLS provides a dense point cloud of abraded surfaces suitable for quantitative assessment of concrete abrasion in the field. Based on the measured abrasion depths and exposure durations, the peak concrete abrasion rates at the site varied from 3.5 to 4.5 mm/year, and severe abrasion was concentrated in the region between mean high-water springs and mean high-water neaps, wherein the highest beach levels were also found during the survey. Finally, the abraded surfaces exhibited a polished texture with no visible craters; thus, the mechanism of concrete material loss was by grinding/polishing due to rolling/sliding sediments.

Development of A Novel Conceptual and Calculative Method for the Prediction of Tide within the Bay of Bengal

Ebb and flow of seawater at regular intervals under the influence of gravitational forces from outside the earth is called tides. This study sheds light on how to measure tides through a new kind of innovative method. This method can be used to measure tides at new locations based on a known tide station. Some parameters play an important role in measuring tides, such as datum information, mean sea level (MSL), mean high water springs (MHWS), mean low water springs (MLWS) and so on. This fancy method is a computational process that relies on observable data and other factors. This innovative method of measuring tides helps to get accurate information in less time and at less cost. From this study we find that the results obtained in our study are in good agreement with the results obtained by other methods and the observed data.

Wave‐ and Tide‐Induced Infragravity Dynamics at an Intermediate‐To‐Dissipative Microtidal Beach

AbstractNumerical simulations of a range of wave climates and tide conditions made with the model XBeach are exploited to study propagation, evolution, dissipation, and reflection patterns of infragravity waves (IGW) at the intermediate‐to‐dissipative beach of Sabaudia (Tyrrhenian sea, Italy). On the basis of a novel calibration process performed using field swash properties collected by a nearby monitoring station, the model reproduces average run‐up characteristics with good skill (Willmott index of agreement of 0.61 for R2%). IGW at Sabaudia beach evolves exclusively as bound long waves growing across the shoaling region for both mild and intense wave climates. Furthermore, values of the dimensionless bed slope βH at which transition from steep‐to mild‐slope behavior occurs are higher than the threshold commonly assumed in the literature. Finally, although the small tide (0.4 m between mean high water spring and mean high water spring; tide range/breaking wave amplitude ratios between 0.14 and 1.1) does not alter bulk IGW reflection significantly, low tide is effective in reducing onshore IGW fluxes and, ultimately, reflection coefficients R2 selectively for intermediate IG frequencies. Our study, for the first time, gives clear evidence that the tide has a role in determining frequency‐dependent IGW dynamics and altering the dissipative state of a mild sloping beach also in a microtidal environment.

Sea-level rise, coastal salinity and vegetation changes in Sri Lanka.

Sea-level rise is a key component of many climate change scenarios. Such increases are expected to cause greater coastal inundation by seawater, reduce the depth of the freshwater-saline water lens and have a range of consequences for coastal ecosystems. Soil salinity determines the distribution patterns of coastal vegetation across a sea-to-land gradient, and sea-level rise would be expected to alter these distributions. Our study done along the east coast of Sri Lanka shows that soil salinity decreases predictably from sea to land, varying between 21‰ and 30‰ over a distance of 50 m from the mean high water springs level. Soil salinity also showed declines with increasing soil depth (0, 10, 50 cm) although this was marginally non-significant. The emergence of terrestrial vegetation coincided with a cross-shore ecotone where the soil salinity approached 0‰. Our predictions suggest that if the mean sea-level were to increase by 1 m in the Batticaloa region (Sri Lanka), this would cause landward communities to be inundated with brackish water at various depths. The present permanent coastal vegetation front would likely shift landward by 30-45 m under scenarios involving a 1 m increase in sea level. Sea-level rise and its consequences could result in a variety of changes to coastal vegetation such as altered physiognomy and diversity, colonization of new territory, expansion of salt-tolerant species such as mangroves and saltmarsh and will therefore greatly influence adaptive management and future planning. This article is part of the theme issue 'Developing resilient energy systems'.

High-Efficiency Determination of Coastline by Combination of Tidal Level and Coastal Zone DEM from UAV Tilt Photogrammetry

To meet the needs of coastline efficient extraction and dynamic monitoring, this paper proposes a new method for coastline extraction by combining the tidal level and the digital elevation model (DEM) of the coastal zone from tilt photography. Firstly, the DEM of coastal zone was obtained by using unmanned aerial vehicle (UAV) tilt photography; at the same time, the accuracy of aerial triangulation(AT) is improved referencing to the constraint of water boundary points, and then the mean high water spring tide was obtained by combining tidal harmonic analysis and Global Navigation Satellite System (GNSS) tidal level. Finally, the coastline and the dynamic water-surface line are extracted from the DEM of the coastal zone by tracking the contour lines with the elevation of the mean high water springs (MHWS) and the instantaneous sea-surface elevation, respectively. The experiments carried out in the coastal zones of Liaoning Province, China, proved the proposed method and achieved better than 0.2 m of horizontal position accuracy and 0.1 m of the vertical accuracy.

Biological Zonation and Bedrock Strength on a High Energy Granite Shore Platform

Burningham, H. and Knight, J. 2020. Biological zonation and bedrock strength on a high energy granite shore platform. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 23-28. Coconut Creek (Florida), ISSN 0749-0208.Many studies have shown that downwearing of rock shore platforms results from interactions between biological and geomorphological processes, but the relative roles of biological, lithological and external (wave hydraulic action) in shaping rock shore platforms have not been examined in detail. This is important, however, because surface organisms can both increase and decrease rates of platform downwearing by biological weathering and bioprotection, respectively. This study presents biological and geomorphological results from a high energy shoreline in northwest Ireland. Here, the 50-100 m wide granite shore platform has a slope of ∼1:6 and extends from 7-9 m above the level of mean high water springs to ∼2 m below mean low water. Organisms attached to the bedrock surface were surveyed by the quadrat method along two shore-normal topographic transects. At each quadrat site, bedrock hardness was measured using an Equotip instrument. Results show clear ecological zonation that can be directly related to the tidal frame. There is very little evidence for cross-shore changes in bedrock hardness. Elevation is the most significant driving factor for the presence of different species, but bedrock hardness is only associated with the abundance of specific species such as barnacles, demonstrating complexity in biogeomorphological relationships at local scales.

Mapping New Zealand 2025 – A National Perspective

Mapping New Zealand 2025 – A National Perspective

Improving the Definition and Algorithms of China’s Coastline Considering the Diversity of Tidal Characteristics

Two commonly used definitions of coastline are compared and analyzed in this article. To build a more perfect digital tide-coordinated coastline model in China, we should first solve the problems of the existing definition and unclear algorithms of China’s coastline. On the basis of defining the coastline in China as the intersection of coastal land and the mean high water spring (MHWS), it should be further revised, and defined either as an intersection of coastal land and the MHWS or as a mean higher high water level (MHHWL) considering the diversity of tidal characteristics in China Sea areas. Since MHWS is related to the extreme of the lunar phase and MHHWL is related to the extreme of the angle of the lunar declination elevation, the algorithms to obtain them are more complicated than that of mean high water (MHW) used in the United States. We should consider the specific law of tidal movement in different tide types of the predominantly semidiurnal or diurnal sea areas in China when studying the precise algorithms for MHWS and MHHWL. Several experiments show that the difference between the two types of calculations of coastal height, such as water level observations and tidal predictions, is within centimeter level. The research results of this article have a certain reference value for countries with similar coastline features as in China.

Benthic foraminifers as a proxy of the range of the tidal wave in the Oyambre Estuary (Cantabria, Spain)

Recent benthic foraminifers from the Oyambre estuary (north of Spain) have been studied in order to learn their biological response to drastic anthropic environmental changes that this estuary has undergone within the last centuries. Up to 41 species have been identified and 24 of them showed live specimens during the sampling period. The most abundant species are Ammonia tepida, Balticammina pseudomacrescens, Cribroelphidium williamsoni, Entzia macrescens, Haynesina germanica, Cibicidoides lobatulus, Miliammina fusca and Trochammina inflata. The statistical analysis (cluster and correspondence analysis) has allowed the differentiation of four groups of samples that are characterized by three assemblages that define the following environments: sandy outer estuary with marine influence (C. lobatulus), mid and inner estuary that comprises an euryhaline subtidal environment with silty sediment (A. tepida and H. germanica), intertidal channels with the lowest salinity levels (C. williamsoni), and marshes (B. pseudomacrescens, E. macrescens, M. fusca and T. inflata).The great number of species with agglutinated shells reveals the ongoing draining in mud-flat areas, as well as the establishment of the vegetated high marsh, where the invasive exotic plant Baccharis halimifolia is removing the reed bed ecosystem and filling, blocking and reducing main and secondary channels. As a result, there is hardly any sandy low marsh left, which in other nearby estuaries of Cantabria is delimited by the species M. fusca. Thus, areas with tidal levels between MHWNT (Mean High Water Neap Tide) and MHW (Mean High Waters) are scarce. However, foraminifer species that live in the high marsh above MHW are dominant. Entzia macrescens and T. inflata mark the interval between MHW and MHWST (Mean High Water Spring Tide), while B. pseudomacrescens the one from MHSWST to the barren zone (vegetated high marshes, closest to land).A comparison between the biocoenosis and thanatocoenosis assemblages generally shows a good similarity (Sanders’ index > 60%). The few samples with a low similarity reveal the effect of post-mortem processes, specially decantation, and, to a lesser extent, suspended transport, which once again points to the lack of hydrodynamism in the estuary. The percentage of exotic or allochthonous species that are deposited in this estuary is very low (the average ranges from 13.4% in the mouth to 0.7% in the inner area), which reveals that the Oyambre estuary has a mesotidal character in its mouth, while in the mid and inner area it can be considered a microtidal estuary. All these data expose that the works conducted in order to recover the Oyambre estuary between years 2009 and 2010 seem not to have been successful in restoring the marshes to their original hydrodynamic conditions.

Evolution of a salt marsh in the southeastern North Sea region – Anthropogenic and natural forcing

Salt-marsh sediments of the southeastern North Sea provide an archive to unravel the influences of coastal management and natural processes such as storm-tide deposition on salt-marsh development. We present a record of salt-marsh evolution during the past century from the Bay of Tümlau (northwestern Germany) based on fossil foraminiferal assemblages and sedimentological data. After diking the hinterland of the Bay of Tümlau in 1935 CE and commencing marsh management, the environment at the study site changed from a tidal flat to a salt marsh. Salt-marsh sediment accretion is influenced by recurrent dredging events, as indicated by layers rich in calcareous tidal-flat foraminifera, and redeposition of siliciclastic particles from the surrounding tidal flats during storm tides. The latter fostered the establishment of a typical salt-marsh foraminiferal fauna dominated by the agglutinating species Entzia macrescens. Storm-tide layers have a lighter sediment color and commonly a more negatively skewed grain-size distribution with variable sorting. The observed long-term coarsening of the salt-marsh sediment likely reflects the landward progression of the vertical erosional cliff and the depletion of fine-grained sediment particles in the tidal flats under the influence of sea-level rise. Supra-tidal conditions, resulting from natural protection measures and abandonment of dredging, are indicated by the occurrence of Balticammina pseudomacrescens around 2001 CE. This species is adapted to only occasional submergence during storm tides. The recent increase in elevation is accompanied by establishment of high-marsh vegetation and characterized by a present height of the marsh surface 50 cm above mean high water springs. During the past sixty years, average sediment accretion rates decreased from 18 to 11 mm yr−1 reflecting the maturing of the salt marsh. These rates clearly outpace the recent mean sea-level rise in the southern North Sea demonstrating that the regional salt marshes are still resilient to sea-level rise.

Impact of Tidal Level Variations on Wave Energy Absorption at Wave Hub

The energy absorption of the wave energy converters (WEC) characterized by a limited stroke length —like the point absorbers developed at Uppsala University—depends on the sea level variation at the deployment site. In coastal areas characterized by high tidal ranges, the daily energy production of the generators is not optimal. The study presented in this paper quantifies the effects of the changing sea level at the Wave Hub test site, located at the south-west coast of England. This area is strongly affected by tides: the tidal height calculated as the difference between the Mean High Water Spring and the Mean Low Water Spring in 2014 was about 6.6 m. The results are obtained from a hydro-mechanic model that analyzes the behaviour of the point absorber at the Wave Hub, taking into account the sea state occurrence scatter diagram and the tidal time series at the site. It turns out that the impact of the tide decreases the energy absorption by 53%. For this reason, the need for a tidal compensation system to be included in the design of the WEC becomes compelling. The economic advantages are evaluated for different scenarios: the economic analysis proposed within the paper allows an educated guess to be made on the profits. The alternative of extending the stroke length of the WEC is investigated, and the gain in energy absorption is estimated.

Eco-engineered rock pools: a concrete solution to biodiversity loss and urban sprawl in the marine environment

In coastal habitats artificial structures typically support lower biodiversity and can support greater numbers of non-native and opportunistic species than natural rocky reefs. Eco-engineering experiments are typically trialed to succeed; but arguably as much is learnt from failure than from success. Our goal was to trial a generic, cost effective, eco-engineering technique that could be incorporated into rock armouring anywhere in the world. Artificial rock pools were created from manipulated concrete between boulders on the exposed and sheltered sides of a causeway. Experimental treatments were installed in locations where they were expected to fail and compared to controls installed in locations in which they were expected to succeed. Control pools were created lower on the structure where they were immersed on every tidal cycle; experimental pools were created above mean high water spring tide which were only immersed on spring tides. We hypothesised that lower and exposed pools would support significantly higher taxon and functional diversity than upper and sheltered pools. The concrete pools survived the severe winter storms of 2013/14. After 12 months, non-destructive sampling revealed significantly higher mean taxon and functional richness in lower pools than upper pools on the exposed side only. After 24 months the sheltered pools had become inundated with sediments, thus failing to function as rock pools as intended. Destructive sampling on the exposed side revealed significantly higher mean functional richness in lower than upper pools. However, a surprisingly high number of taxa colonised the upper pools leading to no significant difference in mean taxon richness among shore heights. A high number of rare taxa in the lower pools led to total taxon richness being almost twice that of upper pools. These findings highlight that even when expected to fail concrete pools supported diverse assemblages, thus representing an affordable, replicable means of enhancing biodiversity on a variety of artificial structures.

Assessment of beach and dune erosion and accretion using LiDAR: Impact of the stormy 2013–14 winter and longer term trends on the Sefton Coast, UK

An important question for coastal management concerns the importance of individual storms and clusters of storms on longer term beach sediment budgets, beach and dune erosion, and coastal flood risk. Between October 2013 and March 2014 a series of deep Atlantic low pressure systems crossed the Northeast Atlantic, and strong winds, high waves and high water levels affected many coastal areas in the UK and other parts of western Europe. Net dune recession of up to 12.1m occurred around Formby Point. On 5 December 2013 the highest water level ever recorded at Liverpool (6.22m ODN) coincided with waves of Hs of 4.55m and Tp of 9.3s in Liverpool Bay. Wave trimming of the dune toe occurred along the entire length of the Sefton coast, but significant dune erosion occurred only where the upper beach (between the mean high water spring tide level and the dune toe) was <25m wide. Sediment budget calculations based on LiDAR surveys in October 2013 and May 2014 indicated a net loss of 127×103m3 of sediment from the beach (above 0m ODN) and a loss of 268×103m3 from the frontal dune system, mostly at Formby Point. However, some parts of the beach to the south of Formby Point gained sediment, indicating net north to south transport over the winter. When considered in a longer term context, the 2013–14 winter represents only a small perturbation on the longer-term coast trend of erosion at Formby Point and progradation to the north and south. Analysis of LiDAR data over a longer time period 1999–2014 indicated upper beach and dune sediment loss of 780×103m3 from the north-central part of Formby Point, with net gains of 806×103m3 and 2116×103m3 in areas to the north and south, respectively. This indicates a net onshore transport of 2142×103m3 from Liverpool Bay towards the coast between Birkdale and Altcar, with a further net total of 210×103m3 transported towards the shore between Altcar and Crosby. In view of the demonstrated value of airborne LiDAR surveys for the quantification of storm impacts and longer term coastal changes, it is recommended that such surveys should be undertaken before and after each winter storm period, covering the area between mean low water spring tide level and a line 200m landward of the dune toe, of as a part of the regional coastal monitoring programme.

Will a rising sea sink some estuarine wetland ecosystems?

Sea-level rise associated with climate change presents a major challenge to plant diversity and ecosystem service provision in coastal wetlands. In this study, we investigate the effect of sea-level rise on benthos, vegetation, and ecosystem diversity in a tidal wetland in west Wales, the UK. Present relationships between plant communities and environmental variables were investigated through 50 plots at which vegetation (species and coverage), hydrological (surface or groundwater depth, conductivity) and soil (matrix chroma, presence or absence of mottles, organic content, particle size) data were collected. Benthic communities were sampled at intervals along a continuum from saline to freshwater. To ascertain future changes to the wetlands' hydrology, a GIS-based empirical model was developed. Using a LiDAR derived land surface, the relative effect of peat accumulation and rising sea levels were modelled over 200years to determine how frequently portions of the wetland will be inundated by mean sea level, mean high water spring and mean high water neap conditions. The model takes into account changing extents of peat accumulation as hydrological conditions alter.Model results show that changes to the wetland hydrology will initially be slow. However, changes in frequency and extent of inundation reach a tipping point 125 to 175years from 2010 due to the extremely low slope of the wetland. From then onwards, large portions of the wetland become flooded at every flood tide and saltwater intrusion becomes more common. This will result in a reduction in marsh biodiversity with plant communities switching toward less diverse and occasionally monospecific communities that are more salt tolerant.While the loss of tidal freshwater wetland is in line with global predictions, simulations suggest that in the Teifi marshes the loss will be slow at first, but then rapid. While there will be a decrease in biodiversity, the model indicated that at least for one ecosystem service, carbon storage, there is potential for an increase in the near future.

Multi-year life spans of high salt marsh agglutinated foraminifera from New Zealand

Abstract The depth-related density profiles of live and dead foraminiferal tests were studied in eleven cores (four with replicate cores) from above mean high water spring level in four high salt marshes in the temperate South Island of New Zealand. The species most tolerant of high elevation and low salinity in New Zealand, Trochamminita salsa, was strongly dominant in most cores but two other species, Haplophragmoides wilberti and Trochammina inflata, occurred in sufficient numbers in several cores to allow analysis. We found that the highest salt marsh foraminifera live at variable depths, sometimes in low numbers down to 30 cm at least. T. salsa appears to occur at greater depths (maximum densities between 5 and 13 cm) than H. wilberti and T. inflata (maximum densities in upper 5 cm). No strong evidence was observed for significant seasonal blooms of these agglutinated species in these highest marsh cores that are only inundated by the tide for a matter of hours a few times per year. Using the size of the total live stock in each core, the downcore density profile of dead tests and the relatively constant sediment accumulation rates we calculated estimates for the mean life spans of these high marsh foraminiferal species by two slightly different methods. Before accepting these life span estimates we compared the actual depth profiles of dead test density in each core with modelled downcore test density profiles based on ideal conditions of constant sedimentation rates, constant livestock numbers, constant live depth distributions and no taphonomic loss. Estimates from three of our cores are rejected because their dead test profiles suggest significant taphonomic loss in the intervals of interest. Estimates from the remaining eight cores indicate that the highest salt marsh foraminifera in temperate New Zealand have mean life spans of 1.3–13 years, with means of 5.5 years for T. salsa, 4.5 years for T. inflata and 3 years for H. wilberti – showing progressively shorter life spans at lower elevations in less stressful environments. These life span estimates are considerably longer than the majority reported for foraminifera from less harsh conditions but help explain how highest marsh foraminifera survive and grow in this extreme environment.

Assessment of spatial and temporal variations of high water mark indicators

The high water mark (HWM) is commonly used as a boundary for coastal management and planning. Due to the dynamic nature of the coastal environment, the determination of HWM can be difficult and may vary based on the indicators unique to the location.Using remote-sensing image analysis techniques, this study evaluates the spatial and temporal variation of HWM based on several indicators. These include vegetation lines, frontal dune toe, mean high water spring (MHWS)/mean higher high water (MHHW), and high water lines (HWL). Other linear boundaries defined by agencies for various applications are also used as indicators.For improved coastal property management, this study also uses an enhanced Spatial Continuity of the Swash Probability (SCSP) model as a HWM indicator by excluding the runup parameter regarding the Spatial Continuity of Tide Probability (SCTP). In order to better account for sudden shape changes, the extended instead of the simple Hausdorff distance has been used to measure the seasonal variation of HWM position. Monte Carlo simulation of DEM data and Fractal Dimension (FD) techniques were used to examine spatial uncertainties due to both the precision of input data and the processing techniques used.Two case study areas in Western Australia with varying coastal conditions have been selected to evaluate the approach. These are Coogee Beach in South Fremantle and Cooke Point in Port Hedland. Results for both study areas indicate that spatial variations of HWM due to seasonal changes are about one order of magnitude larger than variations due to uncertainties in the input data. This behaviour, while present at both study areas, is more significant at Coogee Beach having a sandy beach with high wave energy.

Screening of oomycete fungi for their potential role in reducing the biting midge (Diptera: Ceratopogonidae) larval populations in Hervey Bay, Queensland, Australia.

Biting midges are globally distributed pests causing significant economic losses and transmitting arbovirus diseases to both animals and humans. Current biological and chemical control strategies for biting midge target destruction of adult forms, but strategies directed at immature stages of the insect have yet to be explored in Australia. In the present study, coastal waters of Hervey Bay region in Queensland, Australia were screened to detect the habitats of biting midge at immature stages. These results were then correlated to local environmental conditions and naturally occurring entomopathogenic fungal flora, in particular the Oomycete fungi, to determine their reducing effect on insect immature stages in the search for biological control agents in the region. The dominant species of biting midge found within this study was Culicoides subimmaculatus occuring between mean high water neaps and mean high water spring tide levels. Within this intertidal zone, the presence of C. subimmaculatus larvae was found to be influenced by both sediment size and distance from shore. Halophytophthora isolates colonized both dead and alive pupae. However, the association was found to be surface colonization rather than invasion causing the death of the host. Lack of aggressive oomycete fungal antagonists towards midge larvae might correlate with increased incidences of biting midge infestations in the region.

Subaerial weathering versus wave processes in shore platform development: reappraising the Old Hat Island evidence

AbstractOne of the longest standing debates in rocky coast geomorphology is whether subaerial weathering or wave processes dominate shore platform evolution. The origins of this debate date to the mid‐nineteenth century when the first descriptions of Old Hat Islands were provided from northern New Zealand. Old Hat Islands are surrounded by a broad near‐horizontal shore platform. Their formation was inferred to relate to subaerial weathering of bedrock to a level of permanent saturation with wave processes acting only to remove the weathered debris. To date, no detailed topographic surveys have been conducted on the Old Hat Islands in New Zealand that initiated this debate; in this study we provide the first quantitative data on the original field sites. Topographical surveying and Schmidt Hammer hardness testing were conducted on &gt;25 profiles of varying wave exposure. In contrast to the classic descriptions, platform elevation varies from just above mean high water spring (MHWS) at the most exposed sites, to mean high water neap (MHWN) at the most protected sites or mean sea level (MSL) where beaches occur on the platform surface. There is no significant difference between the hardness of the cliffs and the platforms fronting them and no clear relationship between wave exposure and platform width. Rather than being exclusively dominated by subaerial process, the formation of microtidal, sheltered, Old Hat Island platforms is considered to be a function of (i) the rate of weathering, (ii) exposure to wave energy, (iii) nearshore water depth and (iv) rock resistance. Shore platform elevation in the study area is thought to be a function of the level at which waves erode cliff rock, and the action of weathering which lowers platform surfaces. The width of platforms is strongly influenced by the ability of waves to dissect the platform edge along vertical joint lines. Copyright © 2010 John Wiley &amp; Sons, Ltd.