Cobble Beaches Research Articles

How does invasive Spartina densiflora respond to contrasting environmental conditions in its native region?

Coastal salt marshes are recognized worldwide as diverse and productive environments, providers of many ecosystem services, and as places where a wide variety of taxa live, nest, nurse, and/or feed. Along the Atlantic coast of South America, the austral cordgrass Spartina densiflora displays great phenotypic variations that may favor it to thrive on a wide range of substrates, inhabiting not only the typical soft bottom marshes, but also on cobble beaches and rocky shores. These Patagonian rocky salt marshes, unlike other salt marshes, develop predominantly on top of wave-cut platforms made of sedimentary rock, highly exposed to wave action, and with a dwarf Patagonian phenotype of S. densiflora commonly dominating the vegetation. In this work we evaluate experimentally the hypothesis that this phenotype is a plastic response that maximizes the survival of S. densiflora on rocky bottom environments exposed to wave action. Our results strongly suggest that the austral cordgrass S. densiflora is able to adjust its morphological characteristics in relation to contrasting environmental changes, allowing it to survive in a broad spectrum of coastal environments, including rocky shores with little accumulation of mud and high wave exposure. The typical plants transplanted from the muddy marsh to the rocky marsh exhibited lower height (80%) than the typical control in muddy marsh and than the Patagonian plants in rocky marsh (38%), additionally the typical transplants in the rocky marsh showed no visible damage to their leaves or stems. Our research provides new evidence to understand the success of this species across non-native regions worldwide where it is considered an aggressive invasive bioengineer.

Intertidal Green Crab Survey Over a Ten-Year Period on a Maine Cobble Beach

Here we report on the long-term monitoring of Carcinus maenas (European Green Crab) populations on an intertidal region of a cobble beach in Maine conducted from 2011 to 2021. The number of Green Crabs collected fluctuated between 129 and 474 individuals per sample event. We collected crabs twice each year, with a total number collected of 389 to 798 per year. In addition, we collected Hemigrapsus sanguineus (Asian Shore Crab) in 2 sample years (2019 and 2021), accounting for only 7 individuals. No compelling relationships between Green Crab densities and sea-water temperature, average carapace width, or year of the collection were revealed.

Spatial distribution of macro- and micro-litter items along rocky and sandy beaches of a Marine Protected Area in the western Mediterranean Sea

In this study, the spatial distribution and physical characteristics of beach macro- and micro-litter within the Cabrera Archipelago Maritime-Terrestrial National Park (Cabrera MPA), in the Balearic Islands have been analysed. For macro-litter items, a mean concentration of 1.9 ± 2.4 items/m2 weighing a total of 13 kg was quantified. In terms of beach composition, cobble beaches with deposited seagrass had almost twice as much marine litter as other beaches. For beach micro-litter items, white and transparent microplastics within the size class of 1–2 mm were the most abundant on all the beaches, and the most common polymer types were polyethylene (64%) and polypropylene (17.2%). Overall, for both macro- and micro-litter items, plastic was the most dominant material (90%) identified on all beaches surveyed within Cabrera MPA, indicating areas of low anthropogenic pressures are increasingly becoming sinks for marine litter.

Litter behaviour on Mediterranean cobble beaches, SE Spain

Despite the large research effort on reporting quantities of coastal litter, the dynamics of this litter is not yet sufficiently understood. Litter inputs in five cobble beaches located in the Mediterranean (Spain) were studied over three months during winter by biweekly litter tagging. Plastic represented the dominant material that reached the beaches (77%). In remote and narrow beaches, storms constituted the main driver in litter dynamics, favouring the accumulation of floating items such as plastic bottles and wood fragments as well as the largest but contrasting effects, increasing litter inputs and outputs from the beach, respectively. In rural beaches, beach users, mainly fisher people, but also tourists, contributed to a notable input of litter to the beach. Burial and exhumation of litter were reported as common occurring processes. Better management actions are required to improve beach environmental quality.

Resource partitioning is not coupled with assortative mating in sympatrically divergent ricefish in a Wallacean ancient lake.

Sympatric speciation is considered to be difficult without the coupling between ecological traits that allow resource partitioning and reproductive traits that allow assortative mating. Such "magic traits" are known to be involved in most of the compelling examples of sympatric speciation. In this study, we report a possible case of sympatric speciation without magic traits. Three species of ricefish (genus Oryzias) are suggested to have diverged sympatrically within Lake Poso, an ancient lake in Sulawesi. An analysis of genome-wide single-nucleotide polymorphisms showed that these three species are reproductively isolated from each other throughout the lake. Stable isotope analyses revealed that the three species use different food resources, which reflect differences in their feeding morphologies (gill rakers and digestive tracts) and feeding sites. Field and laboratory observations showed that O.nebulosus and O.orthognathus share a mating habitat of cobbles, where they scatter fertilized eggs, whereas this site is never used by O.nigrimas, indicating that assortative mating is partly achieved by spatial isolation. The small, less-adhesive eggs of O.nebulosus and O.orthognathus probably reflect their adaptation to spawning on cobble beaches. Laboratory mating experiments showed strong prezygotic isolation between O.nebulosus and O.orthognathus, which is achieved by strong species recognition presumably by both sexes based on species-specific mating dances and nuptial coloration. In summary, the assortative mating of O.nebulosus and O.orthognathus is probably not coupled to resource partitioning. We discussed how sympatric speciation among these species might have been achieved even without magic traits.

First observations of the Atlantic beach cricket, Pseudomogoplistes vicentae (Grylloidea: Mogoplistidae), in the Basque autonomous community, Spain

The Atlantic beach cricket Pseudomogoplistes vicentae Gorochov, 1996 (Orthoptera: Grylloidea: Mogoplistidae) is among the rare Orthoptera species that live exclusively in coastal habitats. It inhabits cobble beaches from North Africa to Great Britain, with populations known in Morocco, Portugal, Spain, France, Channel Islands, Wales and England. P. vicentae was found on the Spanish continental coast for the first time in 2018, in Asturias. The discovery of three populations in the Basque autonomous community (Northern Spain) is reported here, and useful information for increasing its detection and monitoring its populations is provided.

Optical dating of cobble surfaces determines the chronology of Holocene beach ridges in Greenland

We constrain the age of a cobble beach ridge system in Greenland using Optically Stimulated Luminescence (OSL) dating of buried cobble surfaces. Luminescence signals from six cobbles are measured using infrared (IR) stimulation at 50 °C (IR50) and 180 °C (pIRIR180); these cobbles represent four progressively younger beach ridges lying between ~35 and ~6 m above present sea level. Luminescence–depth profiles show that the IR50 signals in all the samples and pIRIR180 signals in four out of six samples are well bleached to depths >1.2 mm into the cobble surfaces. Equivalent doses in well‐bleached cobble surface slices (i.e. <1.2 mm) are measured and divided by the effective environmental dose rate to the cobble surfaces in order to derive burial ages. Both IR signals are corrected for anomalous fading using the sample‐specific ratio of the field to the laboratory saturation levels. Our results are consistent with a depositional model predicting that the investigated portion of the beach ridge system built out continuously during relative sea level fall between ~5.3 and ~1.9 ka ago. The optical ages suggest that the rate of construction varied considerably, with the highest rates ~3.4 ka ago. Additionally, the lowest‐elevation beach ridge investigated here provides the first evidence for a higher‐than‐present relative sea level, between 1.5 and 2 ka ago, in the Disko coastal region.

Calcareous meiofauna associated with the calcareous algaCorallina officinalison bedrock and boulder-field shores of Ceredigion, Wales, UK

AbstractThe intertidal coastline of Ceredigion, Wales, comprises a patchwork of unstable sand and cobble beaches, and stable bedrock areas and boulder-fields. The last two shoreline types support rock-pools with growths of the red algaCorallina officinalis, the thalli of which are a popular substrate for calcareous epiphytes. Replicate samples ofC. officinalis(four per site) were taken from (a) three bedrock sites (Ceinewydd, Aberystwyth Victoria Rocks and Castle Rocks) and (b) three boulder-fields (Llanon, Aberaeron lower shore (Aberaeron LS), Llanina) on the lower shore. The middle shore boulder field at Aberaeron (Aberaeron MS) was also sampled. These replicates were examined for calcareous meiofauna (63–2000 μm) not previously examined as a community: spirorbids, foraminifera, gastropods, bryozoans, ostracods and ophiuroids. These were assigned to sessile and vagile modes of life. The sessile association overwhelmingly dominated bedrock coastlines and the Aberaeron MS, while the vagile association was at its most abundant on theCorallinafrom lower shore, stable boulder-fields. Gastropods were almost entirely limited toCorallinaon boulder-fields. We hypothesize that the boulders induce low-energy turbulence among breaking waves, allowing the less firmly attached vagile meiofauna to dominate onC. officinalisin rock-pools in lower shore boulder-fields. The small attachment area of sessile organisms allows them to settle bedrock sites in greater densities than do vagile organisms at boulder-field sites, which are presumed to require larger foraging areas.

Selected studies of sediment tracking in mixed and gravel beaches using RFID technology – A review

Coastal erosion is one of the key environment issues which affects living space for human beings as well as it had greater impact on the tourism industry. Several studies have been carried out to protect the sea shores and beaches from heavy storms and high energy waves. One of the possible ways to prevent coastal erosion is to have gravel beaches or cobble beaches which provides better stability and protection against high energy events. Even though they are providing good protection, best solution can be arrived by understanding morphodynamics of the beach. Sediment tracking is one of the possible methods to analyse the morphodynamics of the beach concerned. There are several methods exists for sediment tracking. Of them, most reliable and cost effective technique is, to track the sediment by using Radio Frequency Identification (RFID) technology. Natural or Artificial pebbles are tagged with RFID tags and they were released on the several regions of the beach under study. After certain period of time, pebbles were tracked with the help of RFID reader along with laptop or palmtop. From the displacement of the pebbles in the study region, it is possible to understand the coastal dynamics of the shoreline concerned. This paper reviews the several scientific studies undertaken with regard to sediment tracking with the help of RFID technology.

Morphodynamics of an Artificial Cobble Beach in Tianquan Bay, Xiamen, China

By tracking and monitoring the profile configuration, topography, and hydrodynamic factors of an artificial cobble beach in Tianquan Bay, Xiamen, China over three consecutive years after its completion, we analyzed the evolution of its profile configuration and plane morphology, and its storm response characteristics. The evolution of the profile configuration of the artificial cobble beach in Tianquan Bay can be divided into four stages. The beach was unstable during the initial stage after the beach nourishment the profile configuration changed obviously, and an upper concave composite cobble beach formed gradually, which was characterized by a steep upper part and a gentle lower part. In the second stage, the cobble beach approached dynamic equilibrium with minor changes in the profile configuration. At the third stage the beach was in a high-energy state under the influence of Typhoon Meranti, and the response of the artificial cobble beach differed significantly from that of the low-tide terrace sandy beach. Within a short time, there was net onshore transport of cobbles in the cross-shore direction. The beach face was eroded, the beach berm was accumulated, and the slope of the beach was steepened considerably. In the alongshore direction, there was notable transport of cobbles on the beach from east to west along the shore, and the total volume of the beach decreased by 4.5×103 m3, which accounted for 50% of the total amount of beach volume lost within three years. The fourth stage was the restoration stage after the typhoon, characterized by a little gentler profile slope and the increase in width and the decrease in height of beach berm. Because of the action of waves and the wave-driven longshore current caused by the specific terrain and landform conditions along the coast (e.g., coastal headlands, near-shore artificial structures, and reefs), the coastline of the artificial cobble beach gradually evolved from being essentially parallel to the artificial coast upon completion to a slightly curved parabolic shape, and three distinct erosion hotspots were formed on the west side of the cape and the artificial drainpipe, and the reefs. Generally, the adoption of cobbles for beach nourishment on this macro-tidal coast beach with severe erosion has yielded excellent stability and adaptability.

The Foundation for Building the Conservation Capacity of Community Ecology

Ecology is a young discipline that needs to develop into a predictive science to confront the challenges of human population pressure and habitat degradation. Basic ecology has disproportionately focused on undisturbed, charismatic ecosystems, species and academic questions, leaving gaps in its ability to inform the conservation and management of degraded, threatened ecosystems. Foundation species-dependent organisms have been studied at the expense of the habitat-forming species that build and maintain communities. We use cobble beaches as a model system to discuss the consequences of this disparity on translational ecology. We suggest that the historic development of ecology has led to an academic discipline ill suited for proactive conservation. We propose that the incorporation of foundation species and hierarchical organization theory into the conceptual framework of ecology will improve its predictive ability and successful application to conservation and the restoration of degraded ecosystems.

Semiautomatic Digital Clast Sizing of a Cobble Beach, Nantian, Taiwan

ABSTRACT Bujan, N.; Cox, R.; Lin, L.-C.; Ducrocq, C., and Hwung, H.-H., 2018. Semiautomatic digital clast sizing of a cobble beach, Nantian, Taiwan. Surface sediment data is scarce for beaches that are made of material close to the cobble size range, partly because of the difficulty of direct sampling for sediment size analysis. An object-detection tool for semiautomatic analysis of clast geometry, originally developed for riverbeds, was applied to the coarse-clastic beach of Nantian, Taiwan. Comparison of the software with digital point counts for the common size percentiles D5, D16, D30, D50, D70, D84, and D95 indicated an average coefficient of determination of 0.990 over 10 test pictures. The surface sediment was digitally sampled at three cross-shore locations along the beach: near the shoreline, on the steep part of the beach face, and on the beach crest. Clast-size distributions, including clast area and elongation ratio, were computed from the geometry of 1000 clasts for each location and the cros...

Amino acid racemisation and uranium-series dating of a last interglacial raised beach, Kingscote, Kangaroo Island, southern Australia

ABSTRACTThe extent to which scleractinian coral inhabited southern Australia during the warm intervals of the Quaternary is poorly understood because identifiable corals from interglacial sedimentary records are scarce. Here we document the presence of a sub-tropical coral, Goniopora lobata, recovered together with warm water mollusc species from a raised cobble and boulder beach conglomerate at Kingscote, Kangaroo Island, dated by uranium-series and amino acid racemisation methods respectively to the last interglacial (MIS 5e). The presence of this assemblage preserved within the Glanville Formation at Kingscote suggests a 2–3° C higher than present last interglacial coastal water temperature for northern Kangaroo Island. The height of the last interglacial shoreline deposit was measured by theodolite, and points to a mean last interglacial sea level 3.1 ± 0.4 m higher than present.

Comparative population biology and reproduction of two sympatric crabs (Grapsidae) on Azores cobble beaches

ABSTRACTPopulation biology of the intertidal crabs Pachygrapsus marmoratus Fabricius, 1787 and P. maurus (Lucas 1846) was investigated at cobble beaches with different levels of wave exposure. Surveys were taken monthly over 1.5 years at three intertidal levels. The growth rate of both species was similar, although P. marmoratus reached larger sizes. This species was more abundant on the mid-littoral zone of sheltered beaches, whereas P. maurus was more abundant on more exposed ones. The sex ratio was male biased in both species, particularly for the smaller and larger size classes. Both species showed an extended reproductive season, coinciding with the rising temperatures of spring and summer, with ovigerous females being found from June to September for P. marmoratus and from May to August for P. maurus. The present study indicates that both could develop adaptive strategies allowing them to coexist in the Azores littoral. The greater size of P. marmoratus seems to be an advantage on the competition for refuges with P. maurus, which results in its higher abundance and general dominance in the higher shore levels and in less exposed shores. However, P. maurus seems to be more fitted to live in the higher hydrodynamic habitats.

Refugio Incident SCAT Operations for Santa Barbara and Ventura Counties Case Study

The Refugio Incident occurred May 19, 2015 along the Gaviota coastline in Santa Barbara County, California. The spill impacted many miles of shoreline and a variety of habitat types. Habitats impacted included exposed wave-cut platforms, man-made structures, cobble, fine-grained sand and boulder beaches. Because of the large scale response, Shoreline Clean-up Assessment Technique (SCAT) surveys were utilized to provide a more systematic assessment of impacted shorelines following a standardized approach. SCAT packets were created to document the progression of clean-up and to direct the Operations Section on where, what, and how to clean the shoreline. One difficulty with this response was that the spill occurred along a dynamic shoreline that constantly changed; and the response was in an area with known significant natural oil seepage. Photographic monitoring points were established throughout the impact area which showed dramatic changes along the coastline throughout the response. A few months into the response, sand and kelp accumulated along the shoreline covering up the incident oil making it difficult to complete the clean-up. SCAT maps were created to make sure that impacted areas that had been previously documented as needing to be cleaned were eventually addressed once the sand eroded from these areas. There was about a two month long time frame where the beach appeared to be clean because of the natural buildup of sand and kelp that covered some of the contamination. The SCAT maps helped to direct the Operations Section by visually identifying specific areas within each segment that still needed cleaning. During a large scale oil spill response when many miles of coastline are impacted in a dynamic environment, it is important to document in a systematic way all field observations so all areas impacted are eventually addressed. This provides the response and the Unified Command with direction and guidance to remediate the spill while taking into account a Net Environmental Benefit Analysis to ensure the established clean-up endpoints are met.

Ballasting the Hanse: Baltoscandian Erratic Cobbles in the Later Medieval Port Landscape of Bruges

The discovery of a remarkable group of vividly coloured rounded cobbles in the fields and monuments of the later medieval outports of Bruges has initiated a multi-disciplinary investigation into their function, provenance, and wider economic meaning. Geological analyses demonstrate that the stones are ballast of exotic lithological nature. A substantial number consist of glacial erratics collected from cobble beaches in the Baltoscandian area. Another group can be traced to north-eastern British coasts. The clustering of stones at Hoeke has drawn particular attention to the Hanseatic connection with Bruges and to the small harbour town of Hoeke, which hosted the staple of stockfish and various other Hanseatic activities. This article contributes to the discussion of ballast stones as a meaningful archaeological object category, especially when studied in a broader methodological context including archaeological, geological, and historical research.

Positive interactions expand habitat use and the realized niches of sympatric species.

Niche theory, the oldest, most established community assembly model, predicts that in sympatry, the realized niche will contract due to negative interspecific interactions, but fails to recognize the effects of positive interactions on community assembly. The stress gradient hypothesis predicts that positive interactions expand realized niches in stressful habitats. We tested the predictions of the stress gradient hypothesis in a cobble beach model system across both physical and biological stress gradients. We transplanted seven common littoral species within, adjacent to, and below Spartina alterniflora cordgrass stands in control, cage control, predator exclusion cage, shade, and shaded predator exclusion cage treatments to test the hypothesis that cordgrass expands intertidal organism habitats. On cobble beaches, cordgrass ameliorates physical and predation stresses, expanding the distribution and realized niches of species to habitats in which they cannot live without facilitation, suggesting that niche theory and species distribution models should be amended to accommodate the role of positive interactions in community assembly.

Long-distance interactions regulate the structure and resilience of coastal ecosystems.

Mounting evidence indicates that spatial interactions are important in structuring coastal ecosystems. Until recently, however, most of this work has been focused on seemingly exceptional systems that are characterized by regular, self-organized patterns. In this review, we document that interactions that operate at long distances, beyond the direct neighborhood of individual organisms, are more common and have much more far-reaching implications for coastal ecosystems than was previously realized. We review studies from a variety of ecosystem types-including cobble beaches, mussel beds, coral reefs, seagrass meadows, and mangrove forests-that reveal a startling interplay of positive and negative interactions between habitats across distances of up to a kilometer. In addition to classical feeding relations, alterations of physical conditions constitute an important part of these long-distance interactions. This entanglement of habitats has crucial implications for how humans manage coastal ecosystems, and evaluations of anthropogenic impact should explicitly address long-distance and system-wide effects before we deem these human activities to be causing little harm.

Should I Stay or Should I Go: Influences on Roseate Terns' (Sterna dougallii) Decisions to Move the Chicks

In this study, we investigated the relative influence of habitat variables on the decision by Sterna dougallii (Roseate Tern) parents to move from (movers) or to stay at (stayers) the nest after chick hatch. At Country Island, NS, Canada, 75% of the 21 Roseate Tern breeding pairs in this study were movers. Using a model-selection approach, we found that the chicks were more likely to be moved from nest sites in cobble beach habitat with low vegetation height and high nest densities of congener terns. However, differences in reproductive parameters among movers and stayers were not statistically significant. Though we could not establish whether moving the chicks or staying were adaptive strategies, we provide firm evidence that Roseate Tern chicks are moved to areas of lower tern densities. Chicks move further away from other terns as they age, perhaps as a mechanism to avoid kleptoparasitism as their nutritional requirements increase. Based on our findings, Roseate Terns appear more likely to rear their chicks to fledging at the original nest site when nest densities of other tern species are low (≤0.02 nests/m2) in highly vegetated areas. Thus, to enhance Roseate Tern productivity in places where they are endangered, such as Atlantic Canada, we suggest that species recovery programs place artificial nest cover, e.g., next boxes and wooden logs, in areas with potential for taller vegetation growth that are suboptimal nesting habitat for S. paradisaea (Arctic Tern)and S. hirundo (Common Tern).

Sediment dynamics on a steep, megatidal, mixed sand–gravel–cobble beach

Abstract. Results are presented from a pilot study of shore-face sediment dynamics on a steep, poorly sorted, coarse-grained, megatidal beach at the head of the Bay of Fundy, Nova Scotia, Canada. The experiment involved the first field deployment of a prototype wideband, pulse-coherent, bistatic acoustic Doppler profiling system. Measurements of the vertical structure of flow and turbulence above a sloping bed, as well as bed material velocity, demonstrate the capabilities of this instrument vis-à-vis studies of nearshore sediment dynamics at the field scale. The second focus of the paper is the unexpected observation that the surficial sediment median diameter, across the lower two-thirds of the intertidal zone, underwent a pronounced decrease when wave forcing was more energetic, compared to values observed during calmer conditions. The explanation for this result appears to involve the formation – in wave-dominated conditions – of metre-scale wavelength, 20 cm high ripples on the rising tide, which are then planed flat by the swash and/or the shore break on the subsequent ebb.