Bryozoan Membranipora Membranacea Research Articles

Wave exposure influences kelp morphological and biomechanical phenotypic plasticity

Despite global and local declines in kelp ecosystems, luxuriant kelp beds persist at the Eastern Shore Islands (ESI) in Nova Scotia, Canada. Kelp beds in other regions of Nova Scotia were defoliated as the invasive bryozoan Membranipora membranacea and warming temperatures weakened kelp tissues and enhanced erosion and dislodgment. We propose that the high wave exposure at the ESI causes morphological and biomechanical phenotypic plasticity of kelp tissues. We compared differences in morphology and mechanical properties of the kelps Laminaria digitata and Saccharina latissima across 3 sites with different wave exposures, and differences in mechanical properties across blade lengths. Both species showed morphological plasticity; higher wave exposure resulted in longer and thicker stipes and thicker blades with increased branching. The mechanical properties of L. digitata showed increased breaking stress (strength) and strain (extensibility) with higher wave exposure, whereas S. latissima did not show mechanical plasticity with increasing exposure. For both species, blades were weaker but more extensible at the meristem and stronger but less extensible near the distal end of the blade. Larger and stronger kelp from high-exposure areas may promote the persistence of kelp beds in the ESI despite local stressors.

A 3‐year plankton DNA metabarcoding survey reveals marine biodiversity patterns in Australian coastal waters

AbstractAimTo use a long‐term collection of bulk plankton samples to test the capacity of DNA metabarcoding to characterize the spatial and seasonal patterns found within a range of zooplankton communities, and investigate links with concurrent abiotic data collected as part of Australia's Integrated Marine Observing System (IMOS) programme.LocationSamples were sourced seasonally for 3 years from nine Pan‐Australian marine sites (n = 90).MethodsHere, we apply a multi‐assay metabarcoding approach to environmental DNA extracted from bulk plankton samples. Six assays (targeting 16SrRNA and COI genes) were used to target, amplify and sequence the zooplankton diversity found within each sample. The data generated from each assay were filtered and clustered into OTUs prior to analysis. Abiotic IMOS data collected contemporaneously enabled us to explore the physical and chemical drivers of community composition.ResultsFrom over 25 million sequences, we identified in excess of 500 distinct taxa and detected clear spatial differences. We found that site and sea surface temperature are the most consistent predictors of differences between zooplankton communities. We detected endangered and invasive species such as the bryozoan Membranipora membranacea and the mollusc Maoricolpus roseus, and seasonal occurrences of species such as humpback whales (Megaptera novaeangliae). We also estimated the number of samples required to detect any significant seasonal changes. For OTU richness, this was found to be assay dependent and for OTU assemblage, a minimum of nine samples per season would be required.Main ConclusionOur results demonstrate the ability of DNA to capture and map zooplankton community changes in response to seasonal and spatial stressors and provide vital evidence to environmental stakeholders. We confirm that a metabarcoding method offers a practical opportunity for an ecosystem‐wide approach to long‐term biomonitoring and understanding marine biomes where morphological analysis is not feasible.

Wave exposure affects the persistence of kelp beds amidst outbreaks of the invasive bryozoan Membranipora membranacea

In certain regions of the northwest Atlantic, rocky subtidal habitats have transitioned from luxuriant kelp beds to turf dominated ecosystems. Encrustation by the invasive epiphytic bryozoan Membranipora membranacea has accelerated the defoliation of macroalgal stands, particularly on the southwestern shore (SWS) of Nova Scotia. In contrast, at the Eastern Shore Islands (ESI) in Nova Scotia, a temperate island archipelago with relatively high wave exposure, kelp beds persist. We investigated how spatial and temporal dynamics of the dominant kelps (Saccharina latissima and Laminaria digitata) and M. membranacea relate to wave exposure. We examined canopy cover and density of kelps using video transects and quadrat sampling at 6 sites of different wave exposures at ESI and a highly wave exposed site on the SWS (Shag Rock), where kelp also persists, in summer and autumn 2018-2020. We measured percent cover of adult colonies of M. membranacea on kelps from autumn 2018 to autumn 2020, and density of settlers in 2019. Colony cover of M. membranacea was comparable across the range of wave exposures at ESI, whereas settler density peaked at intermediate wave exposure. Despite annual outbreaks of the bryozoan, kelp beds at ESI persisted over multiple years, in contrast to a declining trend at Shag Rock. Overwinter recovery of kelps at ESI following bryozoan-induced seasonal declines the preceding autumn indicate that, in contrast to sites on the SWS, these colder more wave exposed kelp beds may be resilient to defoliation.

Invasive marine species discovered on non\u2013native kelp rafts in the warmest Antarctic island

Antarctic shallow coastal marine communities were long thought to be isolated from their nearest neighbours by hundreds of kilometres of deep ocean and the Antarctic Circumpolar Current. The discovery of non–native kelp washed up on Antarctic beaches led us to question the permeability of these barriers to species dispersal. According to the literature, over 70 million kelp rafts are afloat in the Southern Ocean at any one time. These living, floating islands can play host to a range of passenger species from both their original coastal location and those picked in the open ocean. Driven by winds, currents and storms towards the coast of the continent, these rafts are often cited as theoretical vectors for the introduction of new species into Antarctica and the sub-Antarctic islands. We found non-native kelps, with a wide range of “hitchhiking” passenger organisms, on an Antarctic beach inside the flooded caldera of an active volcanic island. This is the first evidence of non-native species reaching the Antarctic continent alive on kelp rafts. One passenger species, the bryozoan Membranipora membranacea, is found to be an invasive and ecologically harmful species in some cold-water regions, and this is its first record from Antarctica. The caldera of Deception Island provides considerably milder conditions than the frigid surrounding waters and it could be an ideal location for newly introduced species to become established. These findings may help to explain many of the biogeographic patterns and connections we currently see in the Southern Ocean. However, with the impacts of climate change in the region we may see an increase in the range and number of organisms capable of surviving both the long journey and becoming successfully established.

Latitudinal, seasonal and depth-dependent variation in growth, chemical composition and biofouling of cultivated Saccharina latissima (Phaeophyceae) along the Norwegian coast

The Norwegian coastline covers more than 10° in latitude and provides a range in abiotic and biotic conditions for seaweed farming. In this study, we compared the effects of cultivation depth and season on the increase in biomass (frond length and biomass yield), chemical composition (protein, tissue nitrogen, intracellular nitrate and ash content) and biofouling (total cover and species composition) of cultivated Saccharina latissima at nine locations along a latitudinal gradient from 58 to 69° N. The effects of light and temperature on frond length and biofouling were evaluated along with their relevance for selecting optimal cultivation sites. Growth was greater at 1–2 m than at 8–9 m depth and showed large differences among locations, mainly in relation to local salinity levels. Maximum frond lengths varied between 15 and 100 cm, and maximum biomass yields between 0.2 and 14 kg m−2. Timing of maximum frond length and biomass yield varied with latitude, peaking 5 and 8 weeks later in the northern location (69° N) than in the central (63° N) and southern (58° N) locations, respectively. The nitrogen-to-protein conversion factor (averaged across all locations and depths) was 3.8, while protein content varied from 22 to 109 mg g−1 DW, with seasonality and latitude having the largest effect. The onset of biofouling also followed a latitudinal pattern, with a delayed onset in northern locations and at freshwater-influenced sites. The dominant epibiont was the bryozoan Membranipora membranacea. Our results demonstrate the feasibility of S. latissima cultivation along a wide latitudinal gradient in North Atlantic waters and underscore the importance of careful site selection for seaweed aquaculture.

Individual and population level effects of ocean acidification on a predator-prey system with inducible defenses: bryozoan-nudibranch interactions in the Salish Sea

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 607:1-18 (2018) - DOI: https://doi.org/10.3354/meps12793 FEATURE ARTICLE Individual and population level effects of ocean acidification on a predator-prey system with inducible defenses: bryozoan-nudibranch interactions in the Salish Sea Sasha K. Seroy1,2,*, Daniel Grünbaum1,2 1School of Oceanography, University of Washington, Seattle, Washington 98105, USA 2Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington 98250, USA *Corresponding author: sseroy@uw.edu ABSTRACT: Ocean acidification (OA) from increased oceanic CO2 concentrations imposes significant physiological stresses on many calcifying organisms. OA effects on individual organisms may be synergistically amplified or reduced by inter- and intraspecies interactions as they propagate up to population and community levels, altering predictions by studies of calcifier responses in isolation. The calcifying colonial bryozoan Membranipora membranacea and the predatory nudibranch Corambe steinbergae comprise a trophic system strongly regulated by predator-induced defensive responses and space limitation, presenting a unique system to investigate OA effects on these regulatory mechanisms at individual and population levels. We experimentally quantified OA effects across a range of pH from 7.0 to 7.9 on growth, calcification, senescence and predator-induced spine formation in Membranipora, with or without waterborne predator cue, and on zooid consumption rates in Corambe at Friday Harbor Laboratories, San Juan Island, WA. Membranipora exhibited maximum growth and calcification at moderately low pH (7.6), and continued spine formation in all pH treatments. Spines reduced Corambe zooid consumption rates, with lower pH weakening this effect. Using a spatially explicit model of colony growth, where colony area serves as a proxy for colony fitness, we assessed the population-level impacts of these experimentally determined individual-level effects in the context of space limitation. The area-based fitness costs associated with defense measured at the individual level led to amplified effects predicted for the population level due to competition. Our coupled experimental and modeling results demonstrate the need to consider population-level processes when assessing ecological responses to stresses from changing environments. KEY WORDS: Predator-prey interactions · Ocean acidification · Inducible defenses · Space competition · Modeling · Membranipora membranacea · Corambe steinbergae Full text in pdf format Information about this Feature Article Supplementary material NextCite this article as: Seroy SK, Grünbaum D (2018) Individual and population level effects of ocean acidification on a predator-prey system with inducible defenses: bryozoan-nudibranch interactions in the Salish Sea. Mar Ecol Prog Ser 607:1-18. https://doi.org/10.3354/meps12793 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.

Low recruitment, high tissue loss, and juvenile mortality limit recovery of kelp following large-scale defoliation

Low recruitment due to limitations of propagule supply or post-settlement survival reinforces dominance of turf algal assemblages that replace canopy algae following large-scale losses. However, post-recruitment processes that hinder juvenile growth and survival (epiphytic overgrowth, grazing, physical stress) also could impede recovery. To evaluate the contribution of recruitment, growth, and survival of young sporophytes to recovery of degraded kelp populations and key factors driving post-recruitment tissue loss and mortality, we followed cohorts of juvenile kelp Saccharina latissima at two defoliated sites in Nova Scotia. We also monitored kelp recruitment, abundance, size structure, and macroalgal composition for 5.5 years. Recruit densities were an order of magnitude lower compared to previous studies in the region. Large decreases in blade area of juveniles were related to cover by the invasive bryozoan Membranipora membranacea, grazing by small snails Lacuna vincta, and warm seawater temperatures. Cohort survival was low (time to 50% mortality 2.5–5.5 months) and increased risk of death was directly related to bryozoan encrustation. Modest seasonal or interannual gains in kelp abundance were lost during periods of peak temperature, which showed a warming trend during the study, favouring persistence of widespread turf-forming, opportunistic and invasive algae. We conclude that low recruitment success, high rate of tissue loss relative to growth, and high mortality, inhibited kelp recovery. Impacts of epiphytic overgrowth, grazing, and warm temperatures on these processes highlight the need to protect intact kelp populations, growing in favourable conditions, to maintain positive interactions that increase resilience to undesirable regime shifts.

Abiotic and biotic interactions in the diffusive boundary layer of kelp blades create a potential refuge from ocean acidification

Abstract Seaweeds are able to modify the chemical environment at their surface, in a micro‐zone called the diffusive boundary layer (DBL), via their metabolic processes controlled by light intensity. Depending on the thickness of the DBL, sessile invertebrates such as calcifying bryozoans or tube‐forming polychaetes living on the surface of the blades can be affected by the chemical variations occurring in this microlayer. Especially in the context of ocean acidification (OA), these microhabitats might be considered as a refuge from lower pH, because during the day photosynthesis temporarily raises the pH to values higher than in the mainstream seawater. We assessed the thickness and the characteristics of the DBL at two pH levels (today's average surface ocean pH 8.1 and a reduced pH predicted for the end of the century, pH 7.7) and seawater flows (slow, 0.5 and fast, >8 cm/s) on Ecklonia radiata (kelp) blades. Oxygen and pH profiles from the blade surface to the mainstream seawater were measured with O2 and pH microsensors for both bare blades and blades colonized by the bryozoan Membranipora membranacea. The DBL was thicker in slow flow compared with fast flow and the presence of bryozoans increased the DBL thickness and shaped the DBL gradient in dark conditions. Net production was increased in the low pH condition, increasing the amount of oxygen in the DBL in both bare and epiphytized blades. This increase drove the daily pH fluctuations at the blade surface, shifting them towards higher values compared with today's pH. The presence of bryozoans led to lower oxygen concentrations in the DBL and more complex pH fluctuations at the blade surface, particularly at pH 7.7. Overall, this study, based on microprofiles, shows that, in slow flow, DBL microenvironments at the surface of the kelps may constitute a refuge from OA with pH values higher than those of the mainstream seawater. For calcifying organisms, it could also represent training ground for harsh conditions, with broad daily pH and oxygen fluctuations. These chemical microenvironments, biologically shaped by the macrophytes, are of great interest for the resilience of coastal ecosystems in the context of global change. A plain language summary is available for this article.

Persistent differences between coastal and offshore kelp forest communities in a warming Gulf of Maine.

Kelp forests provide important ecosystem services, yet coastal kelp communities are increasingly altered by anthropogenic impacts. Kelp forests in remote, offshore locations may provide an informative contrast due to reduced impacts from local stressors. We tested the hypothesis that shallow kelp assemblages (12–15 m depth) and associated fish and benthic communities in the coastal southwest Gulf of Maine (GOM) differed significantly from sites on Cashes Ledge, 145 km offshore by sampling five coastal and three offshore sites at 43.0 +/- 0.07° N latitude. Offshore sites on Cashes Ledge supported the greatest density (47.8 plants m2) and standing crop biomass (5.5 kg m2 fresh weight) of the foundation species Saccharina latissima kelp at this depth in the Western North Atlantic. Offshore densities of S. latissima were over 150 times greater than at coastal sites, with similar but lower magnitude trends for congeneric S. digitata. Despite these differences, S. latissima underwent a significant 36.2% decrease between 1987 and 2015 on Cashes Ledge, concurrent with a rapid warming of the GOM and invasion by the kelp-encrusting bryozoan Membranipora membranacea. In contrast to kelp, the invasive red alga Dasysiphonia japonica was significantly more abundant at coastal sites, suggesting light or dispersal limitation offshore. Spatial differences in fish abundance mirrored those of kelp, as the average biomass of all fish on Cashes Ledge was 305 times greater than at the coastal sites. Remote video censuses of cod (Gadus morhua), cunner (Tautaogolabrus adspersus), and pollock (Pollachius virens) corroborated these findings. Understory benthic communities also differed between regions, with greater abundance of sessile invertebrates offshore. Populations of kelp-consuming sea urchins Stronglyocentrotus droebachiensis, were virtually absent from Cashes Ledge while small urchins were abundant onshore, suggesting recruitment limitation offshore. Despite widespread warming of the GOM since 1987, extraordinary spatial differences in the abundance of primary producers (kelp), consumers (cod) and benthic communities between coastal and offshore sites have persisted. The shallow kelp forest communities offshore on Cashes Ledge represent an oasis of unusually high kelp and fish abundance in the region, and as such, comprise a persistent abundance hotspot that is functionally significant for sustained biological productivity of offshore regions of the Gulf of Maine.

Effects of intrinsic and extrinsic factors on reproduction of an ecologically significant invasive bryozoan: implications for invasion success

The capacity to predict changes in the distribution and abundance of sessile marine invertebrates depends on quantifying factors that affect spatial and temporal variation in propagule production. This is particularly important for invasive species, since both the timing and abundance of introduced propagules can determine invasion success. This study examines the role of reproductive dynamics in contributing to the invasion success of the highly invasive bryozoan Membranipora membranacea by quantifying temporal patterns in the sexual stage and potential fecundity of colonies and examining the effects of intrinsic (colony size) and extrinsic (temperature, host substrate) factors on the reproductive potential of invasive populations. Colonies were collected on the 4 most abundant algal substrates in Nova Scotia at 2–3 sites approximately monthly from 2012 to 2015. Individual zooids within each collected colony were classified by sexual stage (immature, producing sperm only, producing sperm and oocytes, producing oocytes only), and the number of oocytes per colony was counted as a measure of potential colony fecundity (reproductive potential). There were significant seasonal patterns in colony fecundity; however, temperature and colony size accounted for only 12 and 7% of the observed variation, respectively. Instead, consistent differences in reproductive potential were observed among colonies on different algal substrates. Our results indicate how critical demographic processes can differ for invasive species outside of their native range. Our study underscores the need to quantify population dynamics of non-indigenous species within the invaded community to more accurately predict the long-term consequences for invaded ecosystems.

Cleavage modification did not alter blastomere fates during bryozoan evolution

BackgroundStereotypic cleavage patterns play a crucial role in cell fate determination by precisely positioning early embryonic blastomeres. Although misplaced cell divisions can alter blastomere fates and cause embryonic defects, cleavage patterns have been modified several times during animal evolution. However, it remains unclear how evolutionary changes in cleavage impact the specification of blastomere fates. Here, we analyze the transition from spiral cleavage – a stereotypic pattern remarkably conserved in many protostomes – to a biradial cleavage pattern, which occurred during the evolution of bryozoans.ResultsUsing 3D-live imaging time-lapse microscopy (4D-microscopy), we characterize the cell lineage, MAPK signaling, and the expression of 16 developmental genes in the bryozoan Membranipora membranacea. We found that the molecular identity and the fates of early bryozoan blastomeres are similar to the putative homologous blastomeres in spiral-cleaving embryos.ConclusionsOur work suggests that bryozoans have retained traits of spiral development, such as the early embryonic fate map, despite the evolution of a novel cleavage geometry. These findings provide additional support that stereotypic cleavage patterns can be modified during evolution without major changes to the molecular identity and fate of embryonic blastomeres.

Embryonic chirality and the evolution of spiralian left-right asymmetries.

The group Spiralia includes species with one of the most significant cases of left–right asymmetries in animals: the coiling of the shell of gastropod molluscs (snails). In this animal group, an early event of embryonic chirality controlled by cytoskeleton dynamics and the subsequent differential activation of the genes nodal and Pitx determine the left–right axis of snails, and thus the direction of coiling of the shell. Despite progressive advances in our understanding of left–right axis specification in molluscs, little is known about left–right development in other spiralian taxa. Here, we identify and characterize the expression of nodal and Pitx orthologues in three different spiralian animals—the brachiopod Novocrania anomala, the annelid Owenia fusiformis and the nemertean Lineus ruber—and demonstrate embryonic chirality in the biradial-cleaving spiralian embryo of the bryozoan Membranipora membranacea. We show asymmetric expression of nodal and Pitx in the brachiopod and annelid, respectively, and symmetric expression of Pitx in the nemertean. Our findings indicate that early embryonic chirality is widespread and independent of the cleavage programme in the Spiralia. Additionally, our study illuminates the evolution of nodal and Pitx signalling by demonstrating embryonic asymmetric expression in lineages without obvious adult left–right asymmetries.This article is part of the themed issue ‘Provocative questions in left–right asymmetry’.

Quantifying mortality of modular organisms: a comparison of partial and whole‐colony mortality in a colonial bryozoan

AbstractComprehensive studies on the population dynamics of colonial organisms require estimates of mortality from the level of the individual module (partial mortality) to the entire colony (whole‐colony mortality), as well as determining the factors that affect mortality at each level of organization. However, accurate measurements of whole‐colony and partial mortality of modular organisms can be difficult to obtain, and few studies involve concurrent measurements of modular and colony mortality. We implemented multiple approaches to measure whole‐colony and partial mortality of modular species using the colonial bryozoan Membranipora membranacea as a model organism. M. membranacea is a cosmopolitan species and of particular ecological significance in the northwest Atlantic, where it is the dominant epiphyte on laminarian kelps and the main driver for the defoliation of kelp beds. Rates of whole‐colony mortality were measured in the field (1) indirectly through repeated subsampling cohort analyses and (2) directly by tagging colonies in situ. Partial mortality of colonies was measured (1) in the field by quantifying the proportion of degenerated zooids per colony and (2) in the laboratory by monitoring loss of colony surface area during seasonal senescence of colonies over winter. Temporal patterns differed substantially between partial and whole‐colony mortality, suggesting that factors affecting mortality of individual modules differ from those affecting whole colonies. Our study indicated that the accuracy of common methods for measuring mortality of modular organisms depends on the species‐specific life‐history characteristics. However, we suggest that rates and mechanisms of whole‐colony and partial mortality can be most accurately quantified by revisiting tagged individuals in situ and recording loss of entire colonies (whole‐colony mortality) and loss of living colony area (partial mortality) between successive sampling times. For M. membranacea, measuring whole‐colony or partial mortality in isolation would overestimate important demographic rates and underestimate the influence of temperature on mortality, respectively. This study demonstrates the need to include mortality measurements from the level of the individual module to the entire colony when quantifying population dynamics of colonial organisms.

Growth and Reproduction of the Dorid NudibranchOnchidoris muricataFed Native and Invasive Bryozoan Prey

Abstract: Invasion of the bryozoan Membranipora membranacea to the Gulf of Maine provided an additional prey resource to the dorid nudibranch Onchidoris muricata (Muller, 1776). We examined prey choice based on past diet history and compared growth and reproductive output among laboratory-reared O. muricata on exclusive bryozoan diets of M. membranacea and the native, historically preferred prey, Electra pilosa. Adult nudibranchs were collected from Cape Neddick, York, Maine for the prey choice experiment and post-metamorphic juveniles were collected from Jaffery Point, Newcastle, New Hampshire for the growth and reproduction experiments. Nudibranchs were laboratory reared under controlled conditions for up to 10 months until completion of spawning. Growth was monitored biweekly, and reproductive performance was assessed with a weight-adjusted dimensionless reproductive index (ΣRI) of each individual's spawn summed over the reproductive period. Prey choice experiments showed nudibranchs tended to select p...

Kelp in hot water: II. Effects of warming seawater temperature on kelp quality as a food source and settlement substrate

ABSTRACT: Predicting the effect of climate change on communities requires an understanding ofthe effects of environmental conditions on species and their interactions. We investigated thepotential for warming seawater temperature to modify the interactions of the gastropod meso-grazer Lacuna vincta and the invasive bryozoan Membranipora membranacea with kelps in NovaScotia. The nutritional content (C/N) of the kelps Saccharina latissima, Laminaria digitata andAgarum clathratum were unaffected by temperature (11, 18 and 21°C), and chemical defenses(phlorotannins) were reduced only in A. clathratum after 1 wk exposure to 21°C. C/N and phloro-tannin content increased over the season in S. latissima collected monthly in summer 2013 and2014. The effect of temperature-induced changes in kelp on the grazing of L. vincta was assessedusing feeding experiments with S. latissima pretreated at 11 or 21°C. Snails consumed more kelppretreated at 21°C only when grazing rate was high. The quality of S. latissima as a food sourcefor L. vincta was not affected by temperature, as diets of kelp pretreated at 11 and 21°C supportedsimilar growth, reproduction, and survival of snails. Temperature also did not affect the quality ofkelp as a substrate for M. membranacea, since settlement rates were not different betweenS. latissima pretreated at ambient temperature (9 to 14) and 21°C. The absence of temperature-induced changes in kelp quality suggests that the effects of L. vincta and M. membranacea will actadditively with the direct effects of temperature and cause increased biomass loss from kelp beds.KEY WORDS: Kelp · Climate change · Temperature · Saccharina latissima · Lacuna vincta ·Herbivory · Membranipora membranacea · Bryozoans

Recovery capacity of the invasive colonial bryozoan Membranipora membranacea from damage: effects of temperature, location, and magnitude of damage

The survival and reproduction of individual or small groups of modules affords colonial organisms a great regenerative capacity. Consequently, modular loss due to fragmentation or senescence may not necessarily lead to colony mortality. This study (1) examines in situ partial mortality for colonies of the invasive bryozoan Membranipora membranacea in Nova Scotia by quantifying the location, magnitude, and timing of partial mortality for colonies growing on kelp (Saccharina latissima) in the field, and (2) estimates the effects of temperature (5–20 °C), and location and magnitude of modular loss on the recovery capacity of experimentally damaged colonies in the laboratory. In situ zooid mortality was substantial, with 50–100 % of colonies experiencing some level of partial mortality by the end of the growing season. Colonies with damage to older centrally located zooids maintained their capacity for growth and recovery, while colonies where younger peripheral zooids were removed showed no sign of recovery, and often experienced further loss of zooids. The effect of temperature depended on the location of colony damage, with increasing temperature resulting in increased loss of zooids for peripherally damaged colonies, but having no effect on the recovery of colonies with damage to central zooids. Variation in colony recovery may be related to the age distribution and reproductive maturity of zooids within a colony. Alteration of resource allocation between sexual and asexual reproduction may be adaptive in that it maximizes lifetime fitness in response to localized partial mortality.

Does bryozoan colonization alter the biochemical composition of Saccharina japonica affecting food safety and quality?

Abstract The encrusting bryozoan Membranipora membranacea frequently colonizes late-harvested blades of the cultured Saccharina japonica. We measured the proximate compositions, amino acid and fatty acid profiles and metal contents of bryozoans, colonized blades and healthy blades. Bryozoans contained high levels of crude ash (657 g kg-1 dry weight) and arsenic (As; 49 mg kg-1 dry weight) contents, exceeding the recommended range for human food, and had relatively low levels of essential amino acids. The content of inorganic As in bryozoans was 31% of the provisional tolerable weekly intake for inorganic As established by the World Health Organization. Hence, bryozoans decrease the food and fodder quality of the seaweed product. After removing the bryozoans, we found that the seaweed blade tissues beneath the colonies had elevated levels of potassium, iodine and docosahexaenoic acid and reduced levels of copper, chromium and cadmium compared to healthy tissues. Thus, lacy crust bryozoans must be removed from the surface of seaweed prior to its use as food or fodder.

Induced changes in the proteomic profile of the phaeophyte Saccharina japonica upon colonization by the bryozoan Membranipora membranacea

The lacy crust bryozoan Membranipora membranacea frequently colonizes the late harvested blades of aquacultured Saccharina japonica. From proteomic profiles of S. japonica, 145 and 91 protein spots were detected from colonized and healthy tissues, respectively. Among them, 69 and 32 spots were significantly up- and downregulated, respectively, in expression level upon colonization. In M. membranacea colonized tissue, tripartite motif protein 2-like, microcompartments protein, carboxysome peptide shell peptide, trypsin precursor-like, transmembrane protein, two-component response regulator PilR, spermine/spermidine synthase, vanadium-dependent bromoperoxidase, peptide chain release factor 1, interaptin, 50S ribosomal protein L1P, plus agglutinin and leucine-rich repeat protein were upregulated, whereas protoporphyrinogen oxidase, PIH1 domain-containing protein 2, GTPase-activating protein alpha, cytoplasmic threonyl-tRNA synthetase, flavanone 3-hydroxylase, and eukaryotic translation initiation factor 3 proteins were downregulated. Moreover, DEAD/DEAH box helicase, glutamyl-tRNA reductase, and chaperone DnaJ protein were newly expressed in the colonized tissue. Most of the up- and downregulated proteins are known to be related to stress control, defense mechanisms, signal transduction, photosynthesis, protein metabolism, and the cytoskeleton.

Invasive bryozoan alters interaction between a native grazer and its algal food

The epiphytic bryozoan Membranipora membranacea encrusts the surface of kelp blades, causing recurrent large-scale defoliation events in kelp beds off the Atlantic coast of Nova Scotia, Canada. The gastropod Lacuna vincta grazes kelp, creating perforations that weaken blade tissues and increase the fragmentation rate. We assess the interaction between M. membranacea and L. vincta by measuring the grazing rate of snails on bryozoan-encrusted and non-encrusted kelp (Saccharina latissima) in no-choice and choice experiments in the laboratory conducted in November and December 2010. There was no effect of diet on grazing rate in no-choice experiments. In choice experiments, however, L. vincta grazed significantly more non-encrusted than encrusted kelp (7.1 versus 1.1 mg snail−1 d−1), and grazing rate of non-encrusted kelp was almost twice that in the no-choice experiment (3.8 mg snail−1 d−1), indicating that snails may avoid colonies of M. membranacea on partially encrusted kelp blades. We found no effect of diet on growth, reproduction and survival of snails maintained for four weeks on encrusted or non-encrusted kelp. By concentrating grazing damage on non-encrusted areas of blades, L. vincta may act synergistically with M. membranacea to increase the likelihood of blade breakage and canopy loss. This indirect effect of the invasive bryozoan could augment its direct effect on the standing biomass of native kelp beds and detrital export to adjacent communities.

Population Biology of an Intertidal Dorid Nudibranch (Onchidoris muricata) in the Southern Gulf of Maine, U.S.A.: Changes in Phenology Due to an Invasive Prey?

Abstract. The invasion of the bryozoan Membranipora membranacea to the Gulf of Maine in 1987 eventually provided an additional prey resource to the dorid nudibranch Onchidoris muricata (Muller, 1776). The impact of this novel prey on the population and reproductive biology of O. muricata was investigated at an intertidal site in the southern Gulf of Maine from January 2005 to October 2009. Nudibranchs were found associated with a variety of bryozoans, with a seasonal shift from Electra pilosa (December to May) to M. membranacea (June to November). Juveniles (< 3 mm) were found in all months except May, June, and July and mature nudibranchs were present in all months. Copulating pairs were observed between lanuary and July and spawn masses were found between March and September on the undersides of rocks usually attached to the surface of bryozoans. The population structure and reproductive phenology of O. muricata at this intertidal site shows changes from historical reports. Whether adaptive change of th...