Mid Shore Research Articles

Kellie Lodging, 23 High Street, Pittenweem, Fife


 The widely held view that Kellie Lodging (23 High Street, Pittenweem) was built as a townhouse for the Earls of Kellie cannot be correct. The stability of burgage plots in this part of the street shows a reliable match with 16th-century archival data, allowing identification of the occupants of the house at the time it was built (c 1585). Drawings made by Reverend John Sime in 1829 reveal a close historical association between this house and its neighbour at 19–21 High Street, demolished soon after his survey. The occupants of both houses were burgesses, living at a time of acute tension in the town between members of the laird class and the merchants. The siting of the houses at the head of Water Wynd, leading directly to the mid shore, reflects a shift in the town’s focus from the defunct religious area in the Augustinian priory towards a trade-oriented zone around the harbour. Kellie Lodging was the first in the street to have a projecting stair-tower, built not just for display but also for protection in dangerous times. It was quickly followed (1590) by the building of 19–21 with its own stair-tower directly abutting that of Kellie Lodging. Sime’s side-by-side plans of the two houses show the simple L-plan house of Kellie Lodging to be a less ambitious structure than 19–21, which had space to incorporate an inner courtyard to the rear. The street frontage symmetry of the two gables, with an unusual abutment of projecting stair-towers, can be read as a display of solidarity and resolution, as the merchants emerged as the dominant force in the burgh.
 Canmore ID 34283

Biogeographic drivers of distribution and abundance in an alien ecosystem engineer: Transboundary range expansion, barriers to spread, and spatial structure

AbstractAimBiogeographic boundaries can act as either weak or strong barriers to the spread of species undergoing distributional change. Once a novel species spreads across a boundary, it can have a substantial impact on the ecosystem, for instance by competing with local species, and, over the long‐term, re‐engineer the ecosystem. Marine biogeographic regions are clearly defined on the coast of southern Africa and we tested the influence of their boundaries on the spread and spatial structure of an alien ecosystem engineer.LocationSouthern Africa.TaxonAn invasive mussel, Mytilus galloprovincialis.MethodsRecords of M. galloprovincialis were compiled into a database to determine its decadal patterns of spread across multiple bioregions. Distribution and abundance (estimated using density and semi‐quantitative abundance scale [ACFOR]) of this mussel were surveyed to determine patterns in spatial structure across bioregions. In addition, we compared the size structure of populations at the eastern margins of its range with those of larger populations nearer the range centre.ResultsInitial breaching of biogeographic boundaries was associated with rapid spread, but other boundaries encountered decades later acted as barriers to further spread. Across >2,800 km of coast, spatial autocorrelation was observed in densities (low and mid shore levels) and in ACFOR abundances. Repeating spatial patterns in densities and ACFOR abundance were detected at scales of 120–160 km and of 400–990 km. Considerable effort was required to detect populations at the absolute eastern limits of its distribution.Main conclusionDetection of spatial structures at multiple scales suggests that ecologically determined processes regulate abundance at both intra‐bioregional and inter‐bioregional scales, which may help tease apart the historic and contemporary consequences of interspecific interactions on the structure of rocky shore communities. This study demonstrates the influence of biogeography in driving temporal patterns of spread and spatial structure on the distribution and abundance of an invasive species.

Marine Biotechnology in Québec: Science and Innovation Highlights

The development of marine biotechnology in Québec relies on a network of several processing plants of marine seafoods and fishes, a fleet of a thousand coastal and mid shore boats, and many aquaculture companies. Québec's marine biotechnology industry is still very young, in existence just under 20 years. It is distinguished by a dozen small and medium-sized businesses and diverse companies and organizations. Already in the province, the interest of multinational companies in the sector and in the innovative products generated by the smallest biotech is increasing. This paper is an overview of science and innovation activities focusing on the industrial realizations in Québec and introducing some examples of marine by-product valorization, and exploitation of seaweed and microorganisms.

Spatial and temporal variability in the vertical distribution of gastropods on the rocky shores along the east coast of South Andaman Island, India

The present study was conducted for 2 years at six locations along the east coast of South Andaman to study the gastropod vertical zonation. The samples were collected at 3-month intervals between August 2013 and July 2015 (n = 574). The abundance, richness and diversity of high-, mid- and low-shore gastropods was examined to assess the zonal (shore height) variation at the spatial and temporal scales. The upper shore showed higher abundance and lower richness of gastropods in comparison to the mid and lower shores. While the mid shore showed higher diversity of gastropods, abundance was low compared to the upper shore. Differences in gastropod population were greater among locations relative to seasons. This study also reveals that there are significant differences in the gastropods distribution at different shore heights and this variation in the distribution of gastropod assemblage is greater than horizontal variation (i.e. at the spatial scale). Based on the gastropods abundance results, the rocky shore of Andaman may be divided as littorinid, neritid and muricid zones. The PERMANOVA test showed a significant difference of gastropod zonation at the spatial scale and not with time. Bray–Curtis similarity hierarchy and non-metric multi-dimensional scaling (nMDS) separated the study sites into three groups corresponding to shore heights and SIMPER (similarity percentage) analysis revealed the characterising taxa for each group.

Seasonal changes in community structure along a vertical gradient: patterns and processes in rocky intertidal sessile assemblages

AbstractHere we considered two fundamental questions in community ecology regarding the relationship between seasonal changes in community structure and environmental gradients: (i) How does the magnitude of seasonal changes in community structure vary along an environmental gradient? (ii) How do the processes driving seasonal changes in community structure vary along an environmental gradient? To examine these questions, we investigated intertidal sessile assemblages inhabiting a notable vertical environmental gradient and fitted a transition probability matrix model to decadal time series data gathered at 25 plots along the Pacific coast of eastern Hokkaido, Japan. We found that the magnitude of seasonal changes in community structure was the largest at mid shore. The major processes driving seasonal changes in community structure changed vertically, reflecting the indirect influence of vertical changes in the physical environment on the vertical distributions of species. An unexpected finding was that the magnitude of seasonal changes in community structure did not reflect the strength of seasonal variation in the physical environment. One explanation may be that sessile organisms living on the high shore have a broad tolerance to environmental stress and are thus less sensitive to the large seasonal variation in physical stress.

Linking macrobenthic communities structure and zonation patterns on sandy shores: Mapping tool toward management and conservation perspectives in Northern France

In a context of intensifying anthropogenic pressures on sandy shores, the mapping of benthic habitat appears as an essential first step and a fundamental baseline for marine spatial planning, ecosystem-based management and conservation efforts of soft-sediment intertidal areas. Mapping allows representing intertidal habitats that are basically characterised by abiotic (e.g sediments, exposure to waves…) and biotic factors such as macrobenthic communities. Macrobenthic communities are known to show zonation patterns across sandy beaches and many studies highlighted the existence of three biological zones. We tested this general model of a tripartite biological division of the shore at a geographical scale of policy, conservation and management decisions (i.e. Northern France coastline), using multivariate analyses combined with the Direct Field Observation (DFO) method. From the upper to the lower shores, the majority of the beaches exhibited three macrobenthic communities confirming the existence of the tripartite biological division of the shore. Nevertheless, in some cases, two or four zones were found: (1) two zones when the drying zone located on the upper shore was replaced by littoral rock or engineering constructions and (2) four zones on beaches and estuaries where a muddy-sand community occurred from the drift line to the mid shore. The correspondence between this zonation pattern of macrobenthic communities and the EUNIS habitat classification was investigated and the results were mapped to provide a reference state of intertidal soft-sediment beaches and estuaries. Our results showed evidence of the applicability of this EUNIS typology for the beaches and estuaries at a regional scale (Northern France coastline) with a macroecological approach. In order to fulfil the requirements of the European Directives (WFD and MFSD), this mapping appears as a practical tool for any functional study on these coastal ecosystems, for the monitoring of anthropogenic activities and for the implementation of management plans concerning effective conservation strategies.

Recovery of a subtropical rocky shore is not yet complete, four years after a moderate sized oil spill

Little is known about the recovery trajectory from small to moderate spills (<1000t), particularly in the sub-tropics. On 11 March 2009 the MV Pacific Adventurer spilt 270t of bunker fuel oil 13km off Moreton Island, Australia, impacting wetlands, sandy beaches and rocky shores. This study examines the recovery of the rocky shore community four years after the spill. Results indicate that recovery on Moreton Island is taking longer than the 3–4years suggested by the literature. The upper shore is recovering faster than the mid shore and is nearly recovered while the mid shore is still in the recovery process. These results indicate that small to moderate sized spills can have environmental impacts on par with much larger spills and emphasizes the need for a clear definition of a recovery endpoint. Long term studies are required to gain a full understanding of trajectories of recovery after oil spill impacts.

Structure of intertidal sessile communities before and after the invasion of Isognomon bicolor (C.B. Adams, 1845) (Bivalvia, Isognomonidae) in southeastern Brazil

Scientists recognize the importance of ecological data prior to invasion by non-native species in order to evaluate changes in the recipient community. Here we assess the potential impact of the invasion of the bivalve Isognomon bicolor (C.B. Adams, 1845) on Brazilian rocky shores through the use of surveys both before and after the arrival of this non–native species. The invader was mostly distributed across the mid and low shore levels of the intertidal zone with relative abundance ranging from 9.0 to 36.7 percent cover. The mid shore, previously dominated by the native barnacle Tetraclita stalactifera (Lamarck, 1818), was co-dominated by this barnacle species and I. bicolor after invasion. The relative abundance of these species, and presumably the interaction strength between them, differed between sites. At the site where I. bicolor reached the highest abundance (around 30% on average), the abundance of T. stalactifera decreased on average 70% compared to baseline values obtained before the I. bicolor invasion. Finally, conspicuous and extensive I. bicolor beds such as those observed in this study have not been reported in its original distribution range. Beds of I. bicolor may create a much more intricate biogenic matrix than the extents of bare rock and barnacle clumps it replaced. This bivalve may act as an ecosystem engineer and, thus a functionally different component of the intertidal community in its invaded range compared to its native distribution.

Abundance and Spatio-Temporal Distributional Pattern of Dotilla Myctiroides (Milne-Edwards) on Exposed Sandy Beach of Aksa, Mumbai

The abundance and distributional pattern of Ocypodid crab, Dotilla myctiroides (Milne-Edwards) was studied on a sandy beach of Mumbai from January 2005 to December 2006. The area experiences semidiurnal tides. The beach is intermediate dissipative type and consists of medium to fine grade sand. The data were collected after fixing a transect line from high to low shore zone based on tidal heights. A mean abundance of 40 ± 4.55 ind.m−2 was found during 2005, while it was 37.82 ± 7.31 ind.m−2 during 2006. Although no significant difference (p > 0.05) in abundance was observed on seasonal scale, there was a marked variation (p < 0.05) in the vertical distribution with an obvious increasing trend in abundance from high to low shore zone. The zonal variation in the abundance was distinct in different seasons and it increased from pre- to post-monsoon with decreasing tidal heights during both the years. A significant difference (p < 0.05) in the abundance was recorded between high and mid shore zone during all the seasons while mid shore zone showed significantly higher (p < 0.05) abundance during post-monsoon season. Data on distributional pattern of different maturity stages (juvenile, immature, young adult and adult) based on carapace width were also collected. The juveniles were mostly observed in mid and low shore zone, while adults dominated mostly the high shore areas. The factors like morphodynamic state of beach and behavioural ecology of this species seemed to play important role in its high abundance and vertical distribution on the sandy beach of Aksa, Mumbai.

Living in warmer, more acidic oceans retards physiological recovery from tidal emersion in the velvet swimming crab, Necora puber.

The distribution patterns of many species in the intertidal zone are partly determined by their ability to survive and recover from tidal emersion. During emersion, most crustaceans experience gill collapse, impairing gas exchange. Such collapse generates a state of hypoxemia and a hypercapnia-induced respiratory acidosis, leading to hyperlactaemia and metabolic acidosis. However, how such physiological responses to emersion are modified by prior exposure to elevated CO2 and temperature combinations, indicative of future climate change scenarios, is not known. We therefore investigated key physiological responses of velvet swimming crabs, Necora puber, kept for 14 days at one of four pCO2/temperature treatments (400 μatm/10°C, 1000 μatm/10°C, 400 μatm/15°C or 1000 μatm/15°C) to experimental emersion and recovery. Pre-exposure to elevated pCO2 and temperature increased pre-emersion bicarbonate ion concentrations [HCO3(-)], increasing resistance to short periods of emersion (90 min). However, there was still a significant acidosis following 180 min emersion in all treatments. The recovery of extracellular acid-base via the removal of extracellular pCO2 and lactate after emersion was significantly retarded by exposure to both elevated temperature and pCO2. If elevated environmental pCO2 and temperature lead to slower recovery after emersion, then some predominantly subtidal species that also inhabit the low to mid shore, such as N. puber, may have a reduced physiological capacity to retain their presence in the low intertidal zone, ultimately affecting their bathymetric range of distribution, as well as the structure and diversity of intertidal assemblages.

Larval carry‐over effects from ocean acidification persist in the natural environment

An extensive body of work suggests that altered marine carbonate chemistry can negatively influence marine invertebrates, but few studies have examined how effects are moderated and persist in the natural environment. A particularly important question is whether impacts initiated in early life might be exacerbated or attenuated over time in the presence or absence of other stressors in the field. We reared Olympia oyster (Ostrea lurida) larvae in laboratory cultures under control and elevated seawater pCO2 concentrations, quantified settlement success and size at metamorphosis, then outplanted juveniles to Tomales Bay, California, in the mid intertidal zone where emersion and temperature stress were higher, and in the low intertidal zone where conditions were more benign. We tracked survival and growth of outplanted juveniles for 4months, halfway to reproductive age. Survival to metamorphosis in the laboratory was strongly affected by larval exposure to elevated pCO2 conditions. Survival of juvenile outplants was reduced dramatically at mid shore compared to low shore levels regardless of the pCO2 level that oysters experienced as larvae. However, juveniles that were exposed to elevated pCO2 as larvae grew less than control individuals, representing a larval carry-over effect. Although juveniles grew less at mid shore than low shore levels, there was no evidence of an interaction between the larval carry-over effect and shore level, suggesting little modulation of acidification impacts by emersion or temperature stress. Importantly, the carry-over effects of larval exposure to ocean acidification remained unabated 4months later with no evidence of compensatory growth, even under benign conditions. This latter result points to the potential for extended consequences of brief exposures to altered seawater chemistry with potential consequences for population dynamics.

한국 태안군 진산리 저서미세조류의 계절별 종조성 및 생물량 변화

Seasonal species composition and biomass of microphytobenthos were examined at the intertidal flats of Jinsanri, Taean, Korea, from April to December 2011. In total, 121 species were identified, including 109 diatoms, 5 blue-green algae, and 5 dinoflagellates. Seasonal variation in species number ranged from 49 to 56 species (minimum in October and maximal in April), while vertical variation across three different shore levels ranged from 64 to 77 species with maximum at high and minimum at low shore. Species diversity ranged from 3.22 to 3.42 seasonally and from 3.50 to 3.17 across vertical shore levels. Seasonal average values of the normalized difference vegetation index and the vegetation index were 0.06 and 1.14, respectively. Chlorophyll a concentrations were <TEX>$66.00-120.73mg/m^2$</TEX>, with a seasonal minimum and maximum in July and October, respectively, and a vertical shore maximum of <TEX>$137.35mg/m^2$</TEX> at mid shore. Phaeopigment concentrations peaked in October (<TEX>$50.78mg/m^2$</TEX>) and at high shore (<TEX>$61.58mg/m^2$</TEX>) and were lowest in December (<TEX>$22.53mg/m^2$</TEX>) and at low shore (<TEX>$15.28mg/m^2$</TEX>). The number of microphytobenthos ranged from 78,556 to 287,898 cells/<TEX>$cm^2$</TEX>, reaching a maximum in April and a minimum in July. The diatoms Paralia sulcata, Navicula sp., and Delphines surirella were dominant at all tidal levels over the study period. Dinoflagellates were dominant in July at low shore, and blue-green algae were abundant between July and October at mid shore. In conclusion, species composition and primary production of microphytobenthos exhibited clear seasonal and vertical patterns.

Patterns of distribution and abundance of the stalked barnacle (Pollicipes pollicipes) in the central and southwest coast of continental Portugal

The stalked barnacle Pollicipes pollicipes is a cirriped crustacean that lives on very exposed rocky shores. This barnacle is the most important economical resource on intertidal rocky shores of continental Portugal. It is highly prized as food and heavily exploited (professional and recreational fishery), but fishery data are scarce and do not estimate the real pressure upon this resource.Despite its socio-economic interest, specific regulations on this fishery are recent and different along the Portuguese coast. Four regions with different regulation can be identified: the marine reserve “Reserva Natural das Berlengas” (RNB) and the marine park “Parque Marinho Prof. Luiz Saldanha” (PMLS) (both in central Portugal); the natural park located in SW Portugal (“Parque Natural do Sudoeste Alentejano e Costa Vicentina”, PNSACV); and the rest of the coast.The main objective of the present study was to study the spatial patterns of percentage cover, biomass, density and size structure of P. pollicipes in areas with different exploitation regimes, including harvested areas and no-take areas. Additionally, variability between mid shore and low shore barnacles was also analysed.Seven areas were sampled with a variable number of sites (a total of 24) randomly sampled in each area during 2011. Photographs and image analysis (percentage cover) and destructive sampling (density, biomass and size) were used.In general, percentage cover, biomass and density were higher in mid shore when compared to low shore, namely in harvested areas. Low shore barnacles had a higher proportion of adults with moderate and high commercial value, while juveniles were relatively more abundant at mid shore.There were no consistent differences in the patterns of distribution and abundance of P. pollicipes among areas subject to different exploitation regimes. The most different area was the harvested area by professional fishers in RNB, where the highest biomass within the study was registered (mid shore, 7.7kg·m−2). Barnacles within this area presented a higher proportion of adults with commercial value, while recruits and juveniles were relatively more abundant in other areas.The hypothesis of a highest percentage cover, density and biomass in the low shore of no-take sites was not supported.

Interacción entre defensas costeras artificiales en playas arenosas y perturbaciones naturales de gran escala: el terremoto del 27F de 2010 en la costa del centro-sur de Chile

During 2010 and 2011, we studied the effects of the continental uplift that resulted from the earthquake of 27F on the physical landscape and the macrofauna of sandy beaches located in front of coastal armoring along Peninsula de Arauco and nearby areas. The mean width of uplifted beaches during the period following 27F was up to 12,5 times higher than beach widths observed before the earthquake and the beach face slope of uplifted beaches decreased. At those beaches that had coastal armoring located closer to high tides before the earthquake, the restored upper and mid shore beach levels (previously occupied by seawalls and rocky revetments) were rapidly colonized by crustacean species, which typically inhabit at similar intertidal levels of unarmored beaches of Chile. Field samplings carried out promptly after large scale disturbances have occurred, are relevant to increase knowledge on the interaction between that natural phenomenon’s and coastal artifi cial infrastructure.

Detecting spatial heterogeneity in intertidal algal functional groups, grazers and their co-variation among shore levels and sites

Few studies have examined the nature of spatial structure in intertidal systems, especially that of macroalgae and grazers, and it is not clear how consistent spatial heterogeneity is among sites and levels on the shore. Here we studied the consistency of spatial heterogeneity in several algal functional groups and in grazer biomass between two sites and across the shore using a combination of semivariograms and fractal analysis of data collected from transects. Additionally, we tested for consistency in spatial co-variation between algae and grazers using cross-semivariograms. The study was conducted at two sites in South Africa and across a gradient of physiological stress at three levels on the shore (low, mid and high shore). We observed spatial heterogeneity in macroalgal functional groups and in the biomass of grazers at one of the sites and at different levels of environmental harshness (i.e. heights on the shore), while the other site showed consistently random patterns. In terms of alga–grazer co-variation, most transects showed significant co-variation, but with more differences in the sign and the number of lags between sites than among levels on the same shore, suggesting stronger differences in spatial patterns between sites. Also we observed differences in co-variation between macro and mesograzers on the midshore. Variability in spatial patterns among levels on the shore and between sites is not explained by topographic complexity, but may be a product of several biotic factors interacting at small scales (cm–m). Differences in spatial patterns among shore levels and between shores also appear to reflect the indirect effects of an upshore reduction in algal biomass (due to heat and desiccation stress) and human harvesting of grazers at one of the sites, respectively. The results show that spatial heterogeneity of particular organisms (algal groups and grazers) and co-variation between them can emerge at small spatial lags, and reduction in spatial heterogeneity in the intertidal can be induced by a cascading effect driven by disturbance.

Morphological and Behavioral Evidence for Adaptive Diversification of Sympatric Hawaiian Limpets (Cellana spp.)

The endemic Hawaiian limpets (Cellana exarata, Cellana sandwicensis, and Cellana talcosa), reside at different elevations on wave-exposed rocky shores and comprise a monophyletic lineage that diversified within Hawai'i. Here, I report phenotypic differences in shell, soft tissue, and behavioral characters among these limpets and discuss their potential utility in exploiting their respective niches. The high-shore limpet, C. exarata, is characterized by a tall round shell, short mantle tentacles, and long evasion distance when confronted by a predatory gastropod. The mid-shore limpet, C. sandwicensis, is characterized by a shorter oblong shell, long mantle tentacles, and a short evasion distance when confronted by a predatory snail. The low-shore, shallow-subtidal limpet, C. talcosa, is characterized by a flat shell that is thin in juveniles and disproportionately massive in large adults (relative to the other two species), and mantle tentacles of varying lengths (some individuals exhibit short tentacles, some long). These species-specific suites of characters are likely to confer specific fitness advantages on the high shore (C. exarata) where thermal and desiccation stress is severe, on the mid shore (C. sandwicensis) where hydrodynamic forces are severe, and on the low-shallow subtidal shore (C. talcosa) where pelagic predators have free access to the limpets. These data add to the growing body of evidence for adaptive diversification and speciation in the Hawaiian Cellana, and in marine species in general.

A spatially explicit approach to trophic interactions and landscape formation: patchiness in small‐scale variability of grazing effects along an intertidal stress gradient

Summary1. It is well known that grazing contributes to spatial and temporal patterns of algal cover on rocky shores, but this effect has traditionally been studied through grazer exclusion experiments using randomly positioned treatments at particular levels on the shore. Additionally, the effects of grazing on algal composition and biomass are expected to vary across gradients of physical stress and according to grazer size classes.2. We examine two possible sources of spatial variability on rocky shores: (i) across‐shore variability and (ii) size class of grazers. We combined this approach with an across‐shore experiment, with experimental blocks running continuously from low to high shore, to examine the spatial structure of the effect strength of grazing for different size classes of grazers.3. The results indicate that grazing effects vary among zones, habitats and grazer size classes. Micrograzers played a weak role in structuring the algal community and composition. Both macrograzers and mesograzers were important structuring agents on the upper low shore to the mid shore, but only mesograzers were important in tidal pools. Patterns across the shore of grazing effects were dynamic and patchy, acting simultaneously at different scales. The spatial pattern of grazing effects across the shore was also variable in time and was explained by the interactions among physical and biotic factors, often at the longer (10‐m scale) spatial intervals (or lags); mesograzers influenced almost the whole range of lags.4. We conclude, based on cross‐semivariograms, that abiotic factors set variability at large scales, while the effects of biotic factors (in this case grazing) operate simultaneously at scales ranging from small to large.5.Synthesis. Combining zonation and across‐shore experiments indicates that grazing effects do not follow a continuous gradient, but instead have a patchy distribution. This approach provides information about spatial variability that is not available using only the traditional approach, contributing to our understanding of zonation models.

Spatial and Temporal Variability of Intertidal Rocky Shore Bivalves and Gastropods in Sichang Island, East Coast of Thailand

Spatial and temporal variability of intertidal rocky shore bivalves and gastropods in Sichang Island, east coast of Thailand were studied over 12 months (March 2008 to February 2009). The study area experiences mixed tides with the largest tidal range of 3.6 m above MTL during spring tides. Shores are exposed to the prevailing northeast monsoon in the winter (November to February), resulting in stronger wave action during this season than in summer (March to May) and rainy season (June to October). Transects were positioned at five different heights from mid shore to high shore (2.5 to 3.5m above MTL) dominated by rock oysters in the mid shore. At each height, abundance of bivalves and gastropods were recorded within fifteen replicate quadrats (25 x 25 cm) on a monthly basis. A total of 2 bivalves and 10 species of gastropods were identified. In the high shore, the littorinid Echinolittorina malaccana dominated. Dense beds of the bivalve Isognomon nucleus were abundant in crevices at 2.5 and 2.75 m above MTL, whilst a large number of snails (Planaxis sulcatus) were found near the midshore. Below this, the rock oyster Saccostrea cucculata was dominant, with a variety of mobile gastropods (Cellana grata, C. toreuma, Patelloidea saccharina and Siphonaria japonica). The general sequence of zonation patterns were clear over time, but the vertical extent of some mobile species varied in accordance with the monsoon effect and increasing tidal range in winter, especially on the more exposed of the two sites. The high shore littorinids, E. malaccana moved up shore and were more abundant near the supralittoral line in winter suggesting that the seasonal monsoon effect and tidal range were important factors determining the distribution of some species of mobile gastropods, allowing them to exploit higher tidal levels.

Fluctuating asymmetry of Amphibalanus (Balanus) amphitrite (Cirripedia: Thoracica) in association with shore height and metal pollution

The level of fluctuating asymmetry (FA), which is defined as random deviations from perfect bilateral symmetry in the morphological traits of an organism, increases with increasing developmental instability, and it may be used as an indicator of environmental and/or genetic stresses. This study attempted to relate FA levels in the opercular plates of the barnacle Amphibalanus (Balanus) amphitrite with shore height and body trace metal concentrations. Barnacles were collected from both low and mid shores at six coastal locations with various degrees of marine pollution in Hong Kong. Four opercular traits, namely scutum length, tergum length, scutum width, tergum width were measured in the specimen while concentrations of five common trace metals (Cd, Cu, Cr, Mn and Zn) were determined in their body tissues using inductively coupled plasma-atomic emission spectrophotometry. Among the four traits, only tergum length and scutum width fulfilled the assumption of FA while their measurement errors were low. Across all sites, mid-shore A. amphitrite consistently exhibited a significantly higher FA level in scutum width than that in low-shore barnacles, but FA levels in tergum length were similar between the two shore heights. These results suggested that FA was trait-dependent, and mid-shore barnacles were possibly under high physical stress, such as desiccation and high temperature, leading to high developmental instability. Although no positive association was observed between FA and metal contamination in low-shore A. amphitrite, FA level in tergum length significantly increased with decreasing body concentration of manganese (Mn) in these barnacles. Such a negative relationship may be explained by the mechanism of bioaccumulation and physiological role of Mn in A. amphitrite with respect to the formation of barnacle shell plates.

Revealing the mechanisms of sexual isolation in a case of sympatric and parallel ecological divergence

Two ecotypes of a marine intertidal snail (Littorina saxatilis), living at different microhabitats and shore levels, have evolved in sympatry and in parallel across the Galician rocky shore. These ecotypes differ in many traits (including size) due to differential adaptation. They meet, mate assortatively, and partially hybridize at the mid shore where the two microhabitats overlap. The partial sexual isolation observed is claimed to be a side-effect of the size differences between ecotypes combined with a size assortative mating found in most populations of this species. We investigated this hypothesis using three complementary experimental approaches. First, we investigated which of the different shell variables contributed most to the variation in individual sexual isolation in the field by using two new statistics developed for that purpose: (1) pair sexual isolation and (2) ri, which is based on the Pearson correlation coefficient. We found that size is the most important trait explaining the sexual isolation and, in particular, the males appear to be the key sex contributing to sexual isolation. Second, we compared the size assortative mating between regions: exposed rocky shore populations from north-westwern Spain (showing incomplete reproductive isolation due to size assortative mating) and protected Spanish and Swedish populations (showing size assortative mating but not reproductive isolation between ecomorphs). Most of the variation in size assortative mating between localities was significantly explained by the within-population level of variation on size. Third, we performed a laboratory male choice experiment, which further suggested that the choice is made predominantly on the basis of size. These results confirm the mechanism proposed to explain the sexual isolation in the Galician hybrid zone and thus support this case as a putative example of parallel incipient speciation. (Less)