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Vessel biofouling is the putative vector for many marine invasions. Biofouling communities are often dominated by organisms with sessile life history strategies that cannot themselves exit a transport vector, thereby requiring another means of dispersal such as reproduction, which releases mobile propagules. For many sessile organisms, reproduction and associated propagule delivery is tightly coupled with environmental conditions, which frequently vary along vessel transit routes or in ports. However, there are still major gaps in our understanding of specific environmental effects on the reproductive biology of most marine non-indigenous species (NIS), limiting our ability to predict when and where introductions by reproduction will occur. Here, we conducted a manipulative laboratory experiment to explore how variation in temperature and food availability – two conditions that vary among vessel transit routes and ports – affect reproductive output of a common marine biofouling species, the barnacle Amphibalanus improvisus. The experiment had two phases: (1) a simulated “route” portion where temperature and food availability were manipulated independently followed by (2) a simulated “port” portion where temperature and food co-varied. We found that temperature and food availability during both phases affected barnacle fecundity, with reproductive output varying by an order of magnitude between some treatments. Barnacles tended to produce more propagules when temperatures were moderate and food was more plentiful as well as when entering relatively warm ports with greater food availability. Our results show how reproduction by marine biofouling species can be regulated by environmental conditions, which vary predictably with transit route, such that some routes and ports may be especially susceptible to introduction via reproduction. Identifying triggers for reproduction in common marine NIS is therefore key to evaluating the risk of marine invasions. [ABSTRACT FROM AUTHOR]

The spread of marine non-indigenous species (NIS) is driven largely by shipping and global trade. Biofouling on vessel hulls is a major source of invasions, but many biofouling organisms are sessile (non-motile) and require reproduction, which often produces mobile, waterborne propagules (e.g., larvae) that can colonize new regions. The ability of biofouling organisms to reproduce, however, can depend strongly on abiotic conditions at the time of reproduction but also potentially prior to any reproductive event. For many organisms, past environments can influence performance later in life via within-generation carryover effects, but how carryover effects influence potential NIS introductions is unclear. We conducted a laboratory experiment to explore within-generation carryover effects of salinity and how they operate across different environments in the barnacle Amphibalanus improvisus, a common biofouling organism. We exposed newly settled barnacles to two different salinities (15 and 28 psu) for three weeks, maintained them in a common salinity for five weeks, then re-exposed them to the two initial salinities in a fully-factorial design prior to measuring their reproductive output. We found that barnacles that switched salinities between the initial and final exposures tended to produce more nauplii larvae (up to 50%) than those that remained in the same salinity conditions, possibly because of a stress response induced by physiological acclimation to early life environments. Because adult biofouling species are likely to be exposed to variable environmental conditions during vessel transits, carryover effects and their impact on propagule output may be important to consider when evaluating potential NIS introductions via biofouling. [ABSTRACT FROM AUTHOR]

The bay barnacle Amphibalanus improvisus (Darwin, 1854) has been found in Northern Germany in brackish marine sediments of the Holsteinian interglacial. Whereas the cause of the contemporary distribution of this species is anthropogenic and there is evidence that it has resulted mainly from shipping, the fossil findings demonstrate that A. improvisus had also already reached Europe naturally during the Pleistocene in Europe, probably via the Gulf Stream system of the Atlantic. Today, A. improvisus is considered one of the most successful aquatic invasive species worldwide and it is characterized by a high environmental tolerance. The ingression of the Holsteinian Sea, during the Pleistocene, took place during the climate optimum from the North Sea into the 'Elbe Estuary' through the Hamburg region and far to the south‐east into Brandenburg. It has been possible to reconstruct the palaeo‐ecological conditions based in particular on molluscs. Accordingly, environmental conditions ranged from normal marine in the north, via brackish in the transitional area to limnic–fluviatile in the Berlin region. The morphological features of the bay barnacles and their ecological parameters are described here in detail. In addition, we provide a general review of the known Pleistocene Balanidae in northern central Europe. [ABSTRACT FROM AUTHOR]

The sponge derived 2,5-diketopiperazine metabolite barettin is a potent antifouling compound effective against the settlement and metamorphosis of barnacles. Simplified derivatives of barettin have previously been shown to display similar inhibitory properties. The synthetic derivative benzo[g]dipodazine has been reported to display significantly improved antifouling properties in comparison with the native barettin with inhibitory activities as low a 0.034 µM reported against barnacle cyprid settlement. In the current study we report the antifouling activity of 29 synthetic analogs designed and inspired by the potent antifouling effect seen for benzo[g]dipodazine. The library contains mainly not only dipodazine derivatives but also disubstituted diketopiperazines and compounds incorporating alternative heterocyclic cores such as hydantoin, creatinine, and rhodanine. Several of the prepared compounds inhibit the settlement of Amphibalanus improvisus cyprids at low micromolar concentrations, in parity with the natural barettin. While several highly active compounds were prepared by incorporating the benzo[g]indole as hydrophobic substituent, the remarkable antifouling effect reported for benzo[g]dipodazine was not observed when evaluated in our study. [ABSTRACT FROM AUTHOR]

The invasion of alien species in the Black Sea began about 200 years ago and is ongoing. Although the invasive alien species have caused significant changes in the Black Sea ecosystem, the knowledge about their distribution, population status and impact along the Black Sea coast of Georgia is still scarce. The aim of the present study was to assess the distribution and quantitative composition of four of the most common alien marine species in Georgia: the ctenophores Mnemiopsis leidyi and Beroe ovata, the crustacean Amphibalanus improvisus and the bivalve Anadara kagoshimensis. In May 2018, the two ctenophore species were recorded at the same depths, being most abundant and with the highest biomass at 40-50 m. Mnemiopsis leidyi occurred more frequently than B. ovata. Amphibalanus improvisus was present at all stations sampled in 2018, with the highest abundance registered in autumn and the lowest in spring. Anadara kagoshimensis was also recorded at all studied stations. Its quantitative parameters had the highest values at stations with higher salinity. Our results confirm that the four invasive alien species studied have established stable populations off the Black Sea coast of Georgia and may play a key role as factors which influence the native biodiversity. [ABSTRACT FROM AUTHOR]

Barnacles are most important macro benthic population of Rocky shores that Amphibalanusimprovisus is a dominant invasive species of this group. Present study aims to define the number, biomass, coverage rate and to study the factors affecting on the distribution of this species in various parts of rocky shores of south Caspian Sea. Ten sampling stations were selected in the natural and artificial rocky shores from Astara to Babolsar and during two years and every 2 months, once from September 2013 to July2014. In general, the mean number of individuals in this species in the coasts was 404.75 271.165, coverage rate was 36.83 19.657, and weight was 17.81 11.825g in unit surface. While relatively even distribution results are displayed in 10 Stations. But in one-way ANOSIM grouping it was noted that most similarity of habitat was related to the stations 3, 4,5,6,9 and results of One-way ANOVA in various months indicated that temporal changes do not dramatically effect on the frequency of Amphibalanusimprovisus. In addition, it was defined that salinity of southern coasts have not effect for growth of barnacles and temperature was an important and positive factor in frequency.

Levels of pollution, including contamination by toxic metals, in the Thames estuary reduced over the last four decades of the 20th century. This 2014 study investigates whether the declines in the bioavailabilities of trace metals (Ag, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V, Zn) have continued in the 21st century, using a suite of littoral biomonitors also employed in 2001 - the brown seaweed Fucus vesiculosus, the strandline, talitrid amphipod Orchestia gammarellus and the estuarine barnacle Amphibalanus improvisus. Bioaccumulated concentrations represent relative measures of the total bioavailabilities of each metal to the biomonitor over a previous time period, and can be compared over space and over time. Trace metal bioavailabilities varied along the estuary, and, in general, fell between 2001 and 2014, a reflection of the continuing remediation of the Thames estuary from its severely polluted state in the middle of the 20th century. [ABSTRACT FROM AUTHOR]

Macroalgae, especially perennial species, are exposed to a seasonally variable fouling pressure. It was hypothesized that macroalgae regulate their antifouling defense to fouling pressure. Over one year, the macrofouling pressure and the chemical anti-macrofouling defense strength of the brown algaeFucus vesiculosusandFucus serratuswere assessed with monthly evaluation. The anti-macrofouling defense was assessed by means of surface-extractedFucusmetabolites tested at near-natural concentrations in a novelin situbioassay. Additionally, the mannitol content of bothFucusspecies was determined to assess resource availability for defense production. The surface chemistry of bothFucusspecies exhibited seasonal variability in attractiveness toAmphibalanus improvisusandMytilus edulis. Of this variability, 50–60% is explained by a sinusoidal model. OnlyF. vesiculosusextracts originating from the spring and summer significantly deterred settlement ofA. improvisus. The strength of macroalgal antifouling defense did not correlate either within situmacrofouling pressure or with measured mannitol content, which, however, were never depleted. [ABSTRACT FROM AUTHOR]

Ocean acidification is expected to decrease calcification rates of bivalves. Nevertheless, in many coastal areas high p CO2 variability is encountered already today. Kiel Fjord ( Western Baltic Sea) is a brackish (12-20 g kg−1) and CO2 enriched habitat, but the blue mussel Mytilus edulis dominates the benthic community. In a coupled field and laboratory study we examined the annual p CO2 variability in this habitat and the combined effects of elevated p CO2 and food availability on juvenile M. edulis growth and calcification. In the laboratory experiment, mussel growth and calcification were found to chiefly depend on food supply, with only minor impacts of p CO2 up to 3350 μatm. Kiel Fjord was characterized by strong seasonal p CO2 variability. During summer, maximal p CO2 values of 2500 μatm were observed at the surface and >3000 μatm at the bottom. However, the field growth experiment revealed seven times higher growth and calcification rates of M. edulis at a high p CO2 inner fjord field station (mean p CO2 ca. 1000 μatm) in comparison to a low p CO2 outer fjord station (ca. 600 μatm). In addition, mussels were able to out-compete the barnacle Amphibalanus improvisus at the high p CO2 site. High mussel productivity at the inner fjord site was enabled by higher particulate organic carbon concentrations. Kiel Fjord is highly impacted by eutrophication, which causes bottom water hypoxia and consequently high seawater p CO2. At the same time, elevated nutrient concentrations increase the energy availability for filter feeding organisms such as mussels. Thus, M. edulis can dominate over a seemingly more acidification resistant species such as A. improvisus. We conclude that benthic stages of M. edulis tolerate high ambient p CO2 when food supply is abundant and that important habitat characteristics such as species interactions and energy availability need to be considered to predict species vulnerability to ocean acidification. [ABSTRACT FROM AUTHOR]

Effects of epibiotic bacteria associated with macroalgae on barnacle larval attachment were investigated. Eight bacterial isolates obtained from samples of three macroalga species were cultured as monospecies bacterial films and tested for their activity against barnacle ( Amphibalanus improvisus) attachment in field experiments ( Western Baltic Sea). Furthermore, natural biofilm communities associated with the surface of the local brown alga, Fucus vesiculosus, which were exposed to different temperatures (5, 15 and 20 °C), were harvested and subsequently tested. Generally, monospecies bacterial biofilms, as well as natural microbial assemblages, inhibited barnacle attachment by 20-67%. denaturing gradient gel electrophoresis fingerprints showed that temperature treatment shifted the bacterial community composition and weakened the repellent effects at 20 °C. Repellent effects were absent when settlement pressure of cyprids was high. Nonviable bacteria tended to repel cyprids when compared to the unfilmed surfaces. We conclude that biofilms can have a repellent effect benefiting the host by preventing heavy fouling on its surface. However, severe settlement pressure, as well as stressful temperature, may reduce the protective effects of the alga's biofilm. Our results add to the notion that the performance of F. vesiculosus may be reduced by multiple stressors in the course of global warming. [ABSTRACT FROM AUTHOR]

Abstract: The world''s oceans are warming and becoming more acidic. Both stressors, singly or in combination, impact marine species, and ensuing effects might be particularly serious for early life stages. To date most studies have focused on ocean acidification (OA) effects in fully marine environments, while little attention has been devoted to more variable coastal ecosystems, such as the Western Baltic Sea. Since natural spatial and temporal variability of environmental conditions such as salinity, temperature or pCO2 impose more complex stresses upon organisms inhabiting these habitats, species can be expected to be more tolerant to OA (or warming) than fully marine taxa. We present data on the variability of salinity, temperature and pH within the Kiel Fjord and on the responses of the barnacle Amphibalanus improvisus from this habitat to simulated warming and OA during its early development. Nauplii and cyprids were exposed to different temperature (12, 20 and 27°C) and pCO2 (nominally 400, 1250 and 3250μatm) treatments for 8 and 4weeks, respectively. Survival, larval duration and settlement success were monitored. Warming affected larval responses more strongly than OA. Increased temperatures favored survival and development of nauplii but decreased survival of cyprids. OA had no effect upon survival of nauplii but enhanced their development at low (12°C) and high (27°C) temperatures. In contrast, at the intermediate temperature (20°C), nauplii were not affected even by 3250μatm pCO2. None of the treatments significantly affected settlement success of cyprids. These experiments show a remarkable tolerance of A. improvisus larvae to 1250μatm pCO2, the level of OA predicted for the end of the century. [Copyright &y& Elsevier]

The study presents dry mass and body measurements of the larval stages of five common barnacle species occurring in mesozooplankton catches of Southampton Water and the central Solent area of the south coast of the UK. Quantitative samples were collected with conventional 120-μm mesh plankton nets. Species-specific regression equations relating carapace width and total length with dry mass were obtained for stage II to stage VI nauplii and cyprids of Austrominius modestus, Amphibalanus improvisus, Balanus crenatus, Semibalanus balanoides and Verruca stroemia. Width–dry mass and length–dry mass regressions obtained in the present study accounted for more than 98% of the variability for naupliar stages, and length–dry mass for 80% of the variability for cyprids. The dry mass of barnacle larvae predicted from carapace width equations determined here differed by only –6% from the measured dry masses of an independent data set, suggesting these first-reported equations of barnacle larvae are useful additions to zooplankton production studies. [ABSTRACT FROM PUBLISHER]