Shore Height Research Articles

Life in the margins: the effect of immersion/emersion and tidal cycle on the North Atlantic limpet Patella vulgata protein synthesis rates.

Biological processes in intertidal species follow tidal rhythms that enhance survival and fitness. Whereas tidal effects on behaviour and metabolic rates have been widely studied, impacts on other key process such as protein synthesis are still poorly understood. To date, no studies have examined the effect of immersion/emersion and tidal cycles on protein synthesis rates (ks). Patella vulgata is an intertidal limpet present in North-Eastern Atlantic rocky shores from high to low shore. Previously reported P. vulgata respiration and heart rate measurements suggest aerobic metabolism is maintained during emersion and growth rates increase from high to low shore, but whether these patterns are reflected in ks is currently unclear. Here, we measured for the first time in any intertidal organism, ks, RNA to protein ratios and RNA translational efficiency (kRNA) in P. vulgata over a full tidal cycle, at three different shore heights. ks increased during emersion (p < 0.001) and was significantly higher in low shore animals compared to the other shore heights (p < 0.001), additionally ks was negatively correlated to body mass (p = 0.002). RNA to protein ratios remained unchanged over the tidal cycle (p = 0.659) and did not vary with shore height (p = 0.591). kRNA was significantly higher during emersion and was also higher in low shore limpets (p < 0.001). This study demonstrates that P. vulgata increases ks during emersion, an important adaptation in a species that spends a considerable amount of its lifecycle emersed. Intertidal species are highly exposed to increasing air temperatures, making knowledge of physiological responses during emersion critical in understanding and forecasting climate warming impacts.

Relative predation intensity of an intertidal gastropod on artificial coastal defense structures.

Despite seawalls becoming ubiquitous coastal features, and having some physical similarities to natural rocky shores, it remains unclear how these urban habitats influence predator-prey interactions. Predators can affect intertidal mobile prey densities through two pathways: (1) successful predation directly influences prey mortality rates, and (2) direct and indirect effects of predation can scare and induce motile prey to seek safer areas. In this study, we investigated whether intertidal predators affect the density of the marine gastropod, Nerita undata, at four seawall sites in Singapore. Using a tethering method that we developed, we monitored the mortality and other evidence of predation (shell state) of tethered N. undata. Field experiments revealed high (22.5%-82.5%) predation potential of N. undata across the four sites, with significantly higher predation risk at lower shore heights and for snails with mixed shell coloration. Observations and analysis of the shell state after 3 days showed that predation on seawalls was primarily by crushing predators such as fish. Other predators of N. undata include predatory snails, with various feeding methods that left behind different predator signatures. Our results add substantially to the limited knowledge on predator-prey interactions on seawalls, particularly for Nerita undata, and suggest that seawall systems are more dynamic than previously thought. This further highlights the role of these artificial structures as important habitats and feeding grounds in urban coastal ecosystems.

Demography across latitudinal and elevational gradients for range-expanding whelks

Marine species worldwide are responding to ocean warming by shifting their ranges to new latitudes and, for intertidal species, elevations. Demographic traits can vary across populations spanning latitudinal and elevational ranges, with impacts on population growth. Understanding how demography varies across gradients from range center to edge could help us predict future shifts, species assemblages, and extinction risks. We investigated demographic traits for 2 range-expanding whelk species: Acanthinucella spirata and Mexacanthina lugubris. We measured reproductive output across environmental (latitudinal and shore elevation) gradients along the coast of California, USA. We also conducted intensive measurements of offspring condition (survival and thermal tolerance) across shore elevation for M. lugubris at one site. We found no difference in reproductive output, body size, or larval survival across shore heights for M. lugubris, suggesting that egg-laying behavior buffers developing stages from the relatively high level of thermal variation experienced due to daily tidal emersion. However, across latitudes, reproductive output increased toward the leading range edge for A. spirata, and body size increased for both species. Increased vital rates at the leading range edge could increase whelk population growth and expansion, allowing species to persist under climate change even if contractions occur at trailing edges.

Determining restoration potential by transplanting mussels of different size classes over a range of aerial exposures

Restoration of mussels typically focuses on either subtidal or intertidal habitats, although it is important to consider the full historical range of a species. However, it remains unclear how environmental changes can impact the ability of mussels to survive in tidal heights where they occurred historically. Additionally, there is limited research on the viability of reducing mussel stock size for restoration purposes. In this study, green-lipped mussels Perna canaliculus of 2 size classes (80 and 60 mm) were assessed when transplanted as a single size class or as mixed cohorts in 9 m2 plots at 3 shore heights (i.e. neap low tide, spring low tide, and subtidal). The mussels were sampled over a 1 yr period to understand the effect that shore height and size class had on mussel metrics, such as survival, growth, and condition. The results revealed that shore height had a greater effect than size class on mussel survival, with a total loss of mussels transplanted into areas that were exposed at neap tides in contrast to 39% mussel survival transplanted into areas that were only exposed on spring low tides. Further, mussels transplanted in the adjacent subtidal had higher overall survival (74%). This suggests that aerial exposure time determines the upper vertical limit for restoration by transplantation of mussels sourced from aquaculture, despite their historical distribution. The results of this study also support the use of smaller mussels (~60 mm) for transplantation for mussel reef restoration, as a 25% reduction in size resulted in 50% more mussels being deployed.

Channelling of basal resources and use of allochthonous marine carbon by soil arthropods of the Wadden Sea salt marsh

Salt marshes are located between the marine and terrestrial systems. Because they form as sediment accumulates, they comprise a gradient of shore height with differing inundation frequencies and associated abiotic soil conditions. Along this gradient, both autochthonous vascular plant resources and allochthonous marine algal or detrital resources are available, with the availability of both varying with season and salt marsh zone. However, little is known about the importance of either resource for the soil-animal food web. We investigated both spatial and temporal resource use of soil macro- and mesofauna in a salt marsh using neutral lipid fatty acid (NLFA) analysis. Generally, irrespective of season and zone, the soil-animal food web relied on carbon originating from autochthonous vascular plants and associated bacteria and fungi, with the role of bacteria generally exceeding that of fungi. However, the channelling of fungal resources consistently peaked in October, whereas seasonal changes in the channelling of plant and bacterial resources varied among salt marsh zones. Further, variations in the channelling of resources with season and zone varied among salt marsh animal species. Allochthonous resources of marine origin provided only a minor contribution to soil food web nutrition across salt marsh zones and seasons. The contribution of algae to soil food web nutrition depended on inundation frequency and season, i.e. algal productivity. Overall, the results demonstrate that the salt marsh soil fauna predominantly relies on autochthonous vascular plant resources, with the contribution of allochthonous marine resources being minor and restricted to a few taxa.

Trophic structure and origin of resources of soil macrofauna in the salt marsh of the Wadden Sea: a stable isotope (15N, 13C) study

Salt marshes exist along the gradient of the marine mudflat to the terrestrial dunes, with a gradient of shore height and associated plant zonation. The lower salt marsh (LSM) extends from the mean high tidal level to 35 cm above that level and is followed by the upper salt marsh (USM). Despite changes in the amount of allochthonous marine input and in abiotic conditions, little is known about changes in the trophic structure and used of basal resources by the soil macrofauna along marine—terrestrial boundaries. Natural variations in carbon stable isotope ratios (δ13C signatures) allow insight into basal resources of consumers such as marine algae, terrestrial C3 and C4 photosynthesising plants. Furthermore, variations in nitrogen stable isotope ratios (δ15N signatures) allow insight into the trophic position of consumers. We investigated spatial and temporal changes in stable isotope signatures in salt marsh soil macrofauna of the island of Spiekeroog, German Wadden Sea. The range of δ15N signatures indicated no changes in food chain length across salt marsh zones with consumers in both zones comprising primary decomposers, secondary decomposers and first order predators. However, the trophic position of individual species changed between zones, but in particular with season. Contrasting δ15N signatures, the range in δ13C signatures in the LSM was twice that in the USM indicating a wider range of resources consumed. Bayesian mixing models indicated predominant autochthonous resource use in both the LSM and USM, with the use of marine allochthonous resources never exceeding 29.6%. However, the models also indicate an increase in the use of marine resources in certain species in the LSM with no use in the USM. Overall, the results indicate that the resource use of salt marsh macrofauna varies more in space than in time, with the food web being generally based on autochthonous rather than allochthonous resources. However, there also is trophic plasticity in certain species across both temporal and spatial scales including variations in the use of allochthonous resources. Generally, however, marine input contributes little to the nutrition of salt marsh soil macroinvertebrates.

Site fidelity of fish on a rocky intertidal in the south of Portugal

The short-term site fidelity of intertidal fish species was studied in a rocky intertidal zone in southern Portugal using visible implant elastomer tagging. Eleven fish species were caught, tagged and released, seven of which were recaptured. The larger tide pool with the highest complexity level and located at a lower position in the shore level did not have recaptures, while in others the individual fish species recaptured rate ranged from 11.1 to 38.9%, suggesting that the shore height is a dominant factor influencing site fidelity. Although the breeding season seems not to be the only explanation for the recapture rate, the higher mean recapture rates of Parablennius sanguinolentus, Lipophrys pholis and Gobius cobitis may be related to the parental behaviour of these species during that period. Site fidelity of juveniles of Scorpaena porcus in tidepools is reported for the first time, showing the importance of this habitat as a nursery ground.

Spatial and temporal variations in salt marsh microorganisms of the Wadden Sea.

Salt marshes exist at the interface of the marine and the terrestrial system. Shore height differences and associated variations in inundation frequency result in altered abiotic conditions, plant communities, and resource input into the belowground system. These factors result in three unique zones, the upper salt marsh (USM), the lower salt marsh (LSM), and the pioneer zone (PZ). Marine detritus, such as micro‐ and macroalgae, is typically flushed into the PZ daily, with storm surges moving both salt marsh detritus and marine detritus into higher salt marsh zones. Microbial assemblages are essential for the decomposition of organic matter and have been shown to sensitively respond to changes in abiotic conditions such as oxygen supply and salinity. However, temporal and spatial dynamics of microbial communities of Wadden Sea salt marshes received little attention. We investigated the dynamics of soil microbial communities across horizontal (USM, LSM, and PZ), vertical (0–5 and 5–10‐cm sediment depth), and temporal (spring, summer, and autumn) scales in the Wadden Sea salt marsh of the European North Atlantic coast using phospholipid fatty acid (PLFA) analysis. Our results show strong spatial dynamics both among salt marsh zones and between sediment depths, but temporal dynamics to be only minor. Despite varying in space and time, PLFA markers indicated that bacteria generally were the dominant microbial group across salt marsh zones and seasons, however, their dominance was most pronounced in the USM, whereas fungal biomass peaked in the LSM and algal biomass in the PZ. Only algal markers and the stress marker monounsaturated to saturated fatty acid ratio responded to seasonality. Overall, therefore, the results indicate remarkable temporal stability of salt marsh microbial communities despite strong variability in abiotic factors.

Divergence in Thermal Physiology Could Contribute to Vertical Segregation in Intertidal Ecotypes of Littorina saxatilis.

AbstractThermal stress is a potentially important selective agent in intertidal marine habitats, but the role that thermal tolerance might play in local adaptation across shore height has been underexplored. Northwest Spain is home to two morphologically distinct ecotypes of the periwinkle Littorina saxatilis, separated by shore height and subject to substantial differences in thermal stress exposure. However, despite other biotic and abiotic drivers of ecotype segregation being well studied, their thermal tolerance has not been previously characterized. We investigated thermal tolerance across multiple life history stages by employing the thermal death time (TDT) approach to determine (i) whether the two ecotypes differ in thermal tolerance and (ii) how any differences vary with life history stage. Adults of the two ecotypes differed in their thermal tolerance in line with their shore position: the upper-shore ecotype, which experiences more extreme temperatures, exhibited greater endurance of thermal stress compared with the lower-shore ecotype. This difference was most pronounced at the highest temperatures tested. The proximate physiological basis for these differences is unknown but likely due to a multifarious interaction of traits affecting different parts of the TDT curve. Differences in tolerance between ecotypes were less pronounced in early life history stages but increased with ontogeny, suggesting partial divergence of this trait during development. Thermal tolerance could potentially play an important role in maintaining population divergence and genetic segregation between the two ecotypes, since the increased thermal sensitivity of the lower-shore ecotype may limit its dispersal onto the upper shore and so restrict gene flow.

Three‐dimensional mapping reveals scale‐dependent dynamics in biogenic reef habitat structure

AbstractHabitat structure influences a broad range of ecological interactions and ecosystem functions across biomes. To understand and effectively manage dynamic ecosystems, we need detailed information about habitat properties and how they vary across spatial and temporal scales. Measuring and monitoring variation in three‐dimensional (3D) habitat structure has traditionally been challenging, despite recognition of its importance to ecological processes. Modern 3D mapping technologies present opportunities to characterize spatial and temporal variation in habitat structure at a range of ecologically relevant scales. Biogenic reefs are structurally complex and dynamic habitats, in which structure has a pivotal influence on ecosystem biodiversity, function and resilience. For the first time, we characterized spatial and temporal dynamics in the 3D structure of intertidal Sabellaria alveolata biogenic reef across scales. We used drone‐derived structure‐from‐motion photogrammetry and terrestrial laser scanning to characterize reef structural variation at mm‐to‐cm resolutions at a habitat scale (~35 000 m2) over 1 year, and at a plot scale (2500 m2) over 5 years (2014–2019, 6‐month intervals). We found that most of the variation in reef emergence above the substrate, accretion rate and erosion rate was explained by a combination of systematic trends with shore height and positive spatial autocorrelation up to the scale of colonies (1.5 m) or small patches (up to 4 m). We identified previously undocumented temporal patterns in intertidal S. alveolata reef accretion and erosion, specifically groups of rapidly accreting, short‐lived colonies and slow‐accreting, long‐lived colonies. We showed that these highly dynamic colony‐scale structural changes compensate for each other, resulting in seemingly stable reef habitat structure over larger spatial and temporal scales. These patterns could only be detected with the use of modern 3D mapping technologies, demonstrating their potential to enhance our understanding of ecosystem dynamics across scales.

Quantifying seasonal variations in microphytobenthos biomass on estuarine tidal flats using Sentinel-1/2 data.

Quantifying temporal and spatial changes in microphytobenthos (MPB) biomass is critical for understanding its ecological function in estuarine food web networks and carbon flows. However, tidal fluctuations and the complex composition of coastal sediment limit remote sensing applications for estimating MPB biomass seasonal variations in estuarine tidal flats. We integrated radar Sentinel-1 (S1) and optical Sentinel-2 (S2) remote sensing data to quantify the temporal and spatial variability in MPB biomass in the Changjiang estuary, China. Pixels of water bodies on the tidal flats were removed by dynamic threshold segmentation of the water index with the combined S1 and S2 data, and salt marsh pixels were masked with the first red-edge band in the S2 data. We used the continuum-removed spectral absorption depth feature to construct a regression model for estimating MPB biomass with a regression coefficient of 0.81. The results showed that spectral absorption continuum removal methods using broadband multispectral data for MPB estimation are a promising alternative to hyperspectral narrowband ratio operation. Compared with the widely used normalized difference vegetation index (NDVI), the scaled absorption depth feature was more stable for MPB estimation under a changeable sediment background. The produced seasonal map showed that the high biomass levels of the MPB in the study area are not limited to one season and one site, with an annual mean biomass of 14.39mg chlorophyll a (Chl-a)·m-2 and 71% confirmed accuracy. The highest biomass levels occurred in summer in the supratidal zone (19.51mg Chl-a·m-2) and in spring in the intertidal zone (17.10mg Chl-a·m-2) in the Changjiang estuary. The relative shore height, derived from the tidal range here, is an important variable that shapes the MPB spatial distribution. This study demonstrates the potential of integrating high-spatial-resolution (10m) S1 and S2 data for future large-scale estimation of intertidal MPB.

Effects of Intertidal Position on Metabolism and Behavior in the Acorn Barnacle, Balanus glandula.

The intertidal zone is characterized by persistent, tidally-driven fluctuations in both abiotic (e.g., temperature, oxygen, and salinity) and biotic (e.g., food availability and predation) factors, which make this a physiologically challenging habitat for resident organisms. The relative magnitude and degree of variability of environmental stress differ between intertidal zones, with the most extreme physiological stress often being experienced by organisms in the high intertidal. Given that so many of the constantly shifting parameters in this habitat are primary drivers of metabolic rate (e.g., temperature, [O2], and food availability), we hypothesized that sessile conspecifics residing in different tidal zones would exhibit distinct “metabolic phenotypes,” a term we use to collectively describe the organisms’ baseline metabolic performance and capacity. To investigate this hypothesis, we collected acorn barnacles (Balanus glandula) from low, mid, and high intertidal positions in San Luis Obispo Bay, CA, and measured a suite of biochemical (whole-animal citrate synthase (CS) and lactate dehydrogenase (LDH) activity, and aerial [D-lactate]), physiological (O2 consumption rates), morphological (body size), and behavioral (e.g., cirri beat frequency and percentage of time operculum open) indices of metabolism. We found tidal zone-dependent differences in B. glandula metabolism that primarily related to anaerobic capacity, cirral activity patterns, and body size. Barnacles from the low intertidal tended to have a greater capacity for anaerobic metabolism (i.e., increased LDH activity and increased baseline [D-lactate]), have reduced cirral beating activity—and presumably reduced feeding—when submerged, and be smaller in size compared to conspecifics in the high intertidal. We did not, however, see any D-lactate accumulation in barnacles from any tidal height throughout 96 h of air exposure. This trend indicates that the enhanced capacity of low intertidal barnacles for anaerobic metabolism may have evolved to support metabolism during more prolonged episodes of emersion or during events other than emersion (e.g., coastal hypoxia and predation). There were also no significant differences in CS activity or baseline O2 consumption rates (in air or seawater at 14°C) across tidal heights, which imply that aerobic metabolic capacity may not be as sensitive to tidal position as anaerobic processes. Understanding how individuals occupying different shore heights differ in their metabolic capacity becomes increasingly interesting in the context of global climate change, given that the intertidal zone is predicted to experience even greater extremes in abiotic stress.

Two observations of acorn barnacles attached to GLS loggers on seabirds in the North Atlantic

Two observations of acorn barnacles attached to GLS loggers on seabirds in the North Atlantic

Functional diversity of habitat formers declines scale-dependently across an environmental stress gradient

Marine habitat formers such as seaweeds and corals are lynchpins of coastal ecosystems, but their functional diversity and how it varies with scale and context remains poorly studied. Here, we investigate the functional diversity of seaweed assemblages across the rocky intertidal stress gradient at large (zones) and small (quadrat) scales. We quantified complementary metrics of emergent group richness, functional richness (functional space occupied) and functional dispersion (trait complementarity of dominant species). With increasing shore height, under species loss and turnover, responses of functional diversity were scale- and metric-dependent. At the large scale, functional richness contracted while—notwithstanding a decline in redundancy—emergent group richness and functional dispersion were both invariant. At the small scale, all measures declined, with the strongest responses evident for functional and emergent group richness. Comparisons of observed versus expected values based on null models revealed that functional richness and dispersion were greater than expected in the low shore but converged with expected values higher on the shore. These results show that functional diversity of assemblages of marine habitat formers can be especially responsive to environmental stress gradients at small scales and for richness measures. Furthermore, niche-based processes at the small—neighbourhood—scale can favour co-occurrence of functionally distinctive species under low, but not high, stress, magnifying differences in functional diversity across environmental gradients. As assemblages of marine habitat formers face accelerating environmental change, further studies examining multiple aspects of functional diversity are needed to elucidate patterns, processes, and ecosystem consequences of community (dis-)assembly across diverse groups.

The impact of personality, morphotype and shore height on temperature-mediated behavioural responses in the beadlet anemone Actinia equina.

Between-individual variation in behavioural phenotype, termed personality, is an important determinant of how populations cope with acute environmental fluctuation related to climate change. Personality in the beadlet sea anemone Actinia equina is linked to genetically distinct morphotypes, which are associated with different heights on the shore. In the intertidal zone, high-shore environments experience more environmental fluctuation due to longer periods of exposure, and animals adapted to live in these environments are predicted to deal more effectively with environmental perturbation than their low-shore counterparts. We collected beadlet anemones of two different morphotypes from three different shore heights. We investigated variation in two behaviours at three different temperatures and in a temporal control treatment where the temperature was not changed: startle response time, the time it took an anemone to re-extend its tentacles after a threatening stimulus, and immersion response time, the time to re-extend tentacles after simulated tidal immersion. These behaviours reflect risk-taking and allow individuals to be categorized as bold, shy or intermediate based upon response times. Both behaviours showed significant changes as the temperature increased. For immersion response, the morphotype associated with the low-shore-lengthened response times at high temperatures. For startle response, all animals lengthened their response times at high temperatures but animals collected from the low-shore lengthened theirs to the greatest degree. At the individual level, although control individuals exhibited temporal changes in their response times, a clear effect of temperature was present in both behaviours. Shy and bold individuals became more intermediate at higher temperatures in immersion response (this effect was present to a lesser degree in control individuals), while intermediate individuals raised their response times at higher temperatures for startle response. Given that prolonged tentacle retraction reduces foraging opportunities and can negatively impact respiratory efficiency, our data suggest that some individuals within a single population of A.equina, particularly those associated with the lower shore, may exhibit less effective behavioural responses to temperature shifts than others. These findings demonstrate that acute temperature changes influence risk-taking, and could have profound short and long-term implications for survival in the face of climate change.

Facilitation of an invader by a native habitat-former increases along interacting gradients of environmental stress.

Native habitat-forming species can facilitate invasion by reducing environmental stress or consumer pressure. However, the intensity of one stressor along a local gradient may differ when expanding the scale of observation to encompass major variations in background environmental conditions. In this study, we determined how facilitation of the invasive porcelain crab, Petrolisthes elongatus, by the native tube-forming serpulid, Galeolaria caespitosa, varied with environmental gradients at local (tidal height) and larger (wave exposure) spatial scales. G.caespitosa constructs a complex calcareous matrix on the underside of intertidal boulders and we predicted that its positive effects on P.elongatus density would increase in intensity with shore height and be stronger at wave-sheltered than wave-exposed locations. To test these predictions, we conducted two experiments. First, we determined the effects of serpulid presence (boulders with live or dead serpulid matrix vs. bare boulders) at six shore heights that covered the intertidal distribution of P.elongatus. Second, we determined the effects of serpulid presence (present vs. absent), shore height (high vs. low) and wave exposure (sheltered vs. exposed) on crabs across six locations within the invaded range in northern Tasmania, Australia. In Experiment 1, the presence of serpulids (either dead or alive) enhanced P.elongatus densities at all shore heights, with facilitation intensity (as determined by a relative interaction index; RII) tending to increase with shore height. In Experiment 2, serpulids facilitated P.elongatus across shore heights and wave exposures, although crab densities were lower at high shore levels of wave-sheltered locations. However, the intensity of crab facilitation by serpulids was greater on wave-sheltered than on wave-exposed shores, but only at the high shore level. This study demonstrates that local effects of native habitat-formers on invasive species are dependent on prevailing environmental conditions at larger spatial scales and that, under more stressful conditions, invaders become increasingly reliant on positive interactions with native habitat-formers. Increased strength of local-scale facilitation by native species, dampening broader scale variations in environmental stressors, could enhance the ability of invasive species to establish self-sustaining populations in the invaded range.

The cost of emersion for the barnacle Balanus glandula

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 627:95-107 (2019) - DOI: https://doi.org/10.3354/meps13058 The cost of emersion for the barnacle Balanus glandula Gordon T. Ober1,2,*, Rhiannon L. Rognstad2,3, Sarah E. Gilman2 1Environmental Science Department, Endicott College, 376 Hale St, Beverly, MA 01915, USA 2The W. M. Keck Science Department of Claremont McKenna, Scripps, and Pitzer Colleges, 925 N. Mills Ave, Claremont, CA 91711, USA 3Present address: Marine Science Institute, University of California at Santa Barbara, Santa Barbara, CA 93117, USA *Corresponding author: gober@kecksci.claremont.edu ABSTRACT: Temperate intertidal species frequently experience broad temperature fluctuations during emersion. However, the metabolic cost of exposure to a particular emersion temperature is not known for most species. We quantified oxygen (O2) consumption by the intertidal barnacle Balanus glandula over a combined 5 h emersion and a 6 h immersion period. Barnacles were exposed to air temperatures of 10, 15, 20, 25, 30, 35, or 38°C followed by a 10°C immersion. Respiration was monitored using a fluorometric O2 system. Total O2 consumption over the 11 h period by B. glandula increased with increasing emersion temperatures, reaching a maximum between 20 and 30°C, where consumption was significantly greater than that at 10°C. Aerial and aquatic phases showed similar patterns with temperature, but significant differences among temperatures were only detected in the aerial phase. We also found that respiration rates peaked during the first hour at temperature during emersion and the second hour of immersion. A separate analysis of barnacle behavior over a longer immersion period suggested that stressful emersion temperatures require recovery periods longer than 6 h; thus, our results may underestimate the full cost of thermal stress. When compared to previously published measurements of barnacle body temperatures in the field, our results suggest a large vertical gradient in thermal exposure costs, nearly doubling with a 1 m increase in shore height. We highlight both the difficulty and importance of generating accurate estimates of emersion costs. Such costs are likely to be critical in determining organismal and population responses to changing climate. KEY WORDS: Intertidal barnacle · Respiration · Temperature · Emersion stress · Energetic cost Full text in pdf format Supplementary material PreviousNextCite this article as: Ober GT, Rognstad RL, Gilman SE (2019) The cost of emersion for the barnacle Balanus glandula. Mar Ecol Prog Ser 627:95-107. https://doi.org/10.3354/meps13058 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 627. Online publication date: September 26, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Mapping the consequences of artificial light at night for intertidal ecosystems.

Widespread coastal urbanization has resulted in artificial light pollution encroaching into intertidal habitats, which are highly valued by society for ecosystem services including coastal protection, climate regulation and recreation. While the impacts of artificial light at night in terrestrial and riparian ecosystems are increasingly well documented, those on organisms that reside in coastal intertidal habitats are less well explored. The distribution of artificial light at night from seaside promenade lighting was mapped across a sandy shore, and its consequences for macroinvertebrate community structure quantified accounting for other collinear environmental variables known to shape biodiversity in intertidal ecosystems (shore height, wave exposure and organic matter content). Macroinvertebrate community composition significantly changed along artificial light gradients. Greater numbers of species and total community biomass were observed with increasing illumination, a relationship that was more pronounced (increased effects size) with increasing organic matter availability. Individual taxa exhibited different relationships with artificial light illuminance; the abundances of 27% of non-rare taxa [including amphipods (Amphipoda), catworms (Nephtys spp.), and sand mason worms (Lanice conchilega)] decreased with increasing illumination, while 20% [including tellins (Tellinidae spp.), lugworms (Arenicola marina) and ragworms (Nereididae spp.)] increased. Possible causes of these relationships are discussed, including direct effects of artificial light on macroinvertebrate behaviour and indirect effects via trophic interactions. With increasing light pollution in coastal zones around the world, larger scale changes in intertidal ecosystems could be occurring.

Trophic niche separation in sympatric rocky shore crabs

AbstractWhere two species occupy the same habitat and similar niches, competition is likely to drive small-scale spatial niche separation or resource partitioning that may not be immediately apparent. A stable isotope approach was used to investigate potential trophic niche separation between co-existing rocky shore crabs in the North-West (NW) Arabian Gulf. Leptodius exaratus and Pilumnopeus convexus which occupy similar shore height on the same rocky intertidal habitats. We also investigated conspecific differences between males vs females and adults vs juveniles. δ15N results indicated that adults of both species occupy a high trophic level in the rocky shore community, suggesting similar functional roles and potential for competition for food resources, while significant differences in δ13C values indicated differences in dietary sources between the two species, and also changes in diet between juveniles and adults in both species. MixSIAR analysis of δ15N and δ13C data confirmed field observations that both species are generalist omnivores, with potential for direct competition including adult predation on juveniles, including conspecifics. Differentiation in isotopic niches (SIBER analysis) was mainly driven by the significant differences in δ13C values, suggesting that co-existence of the two crab species is at least in part mediated by trophic niche separation or dietary resource partitioning, with some (unquantified) potential for spatial resource partitioning at the microhabitat level.

Comparisons of life-history traits of the alien invasive Semimytilus algosus and three other mytilid mussels on the West Coast of South Africa

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 607:113-127 (2018) - DOI: https://doi.org/10.3354/meps12794 Comparisons of life-history traits of the alien invasive Semimytilus algosus and three other mytilid mussels on the West Coast of South Africa Zannè Zeeman*, George M Branch, Deena Pillay Department of Biological Sciences and Marine Research Institute, University of Cape Town, Rondebosch 7700, South Africa *Corresponding author: zannezeeman@gmail.com ABSTRACT: The invasive mytilid mussel Semimytilus algosus was first recorded on South African shores in 2009 and rapidly spread to occupy 500 km of the West Coast, where it dominates lower portions of the rocky shore. To identify mechanisms underlying the invasive success of S. algosus, the life-history parameters survivorship, reproductive output, recruitment, growth rate and shell and byssus strength were compared among S. algosus and another alien, Mytilus galloprovincialis, and the indigenous mussels Aulacomya atra and Choromytilus meridionalis. To standardise the effects of wave exposure and shore height on life history patterns, all observations and sampling were limited to the low shore at the research site, Bloubergstrand. The 4 mussel species employed very different means of maximising survival and/or space occupancy. S. algosus proved to be a typical r-selected species, with low survival due to its weak shell and byssal strength. Unexpectedly, it grew relatively slowly but had a high reproductive output and exceptionally high recruitment rate that largely account for its invasive success. This study therefore demonstrates how life-history traits influence the invasive success of alien species and allows predictions about their relative impacts on intertidal rocky shores. KEY WORDS: Invasive species · Competition · Rocky shores · Recruitment · Growth · Reproduction Full text in pdf format Supplementary material PreviousNextCite this article as: Zeeman Z, Branch GM, Pillay D (2018) Comparisons of life-history traits of the alien invasive Semimytilus algosus and three other mytilid mussels on the West Coast of South Africa. Mar Ecol Prog Ser 607:113-127. https://doi.org/10.3354/meps12794 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 607. Online publication date: December 06, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.