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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.

Species distribution models (SDMs) are important tools for predicting the occurrence and abundance of organisms in space and time, with numerous applications in ecology. However, the accuracy and utility of SDMs can be compromised when predictor variables are selected without careful consideration of their ecophysiological relevance to the focal organism. We conducted an in-depth examination of the variable selection process by evaluating predictors to be used in SDMs for Membranipora membranacea, an ecologically significant marine invasive species with a complex lifecycle, as a case study. Using an information-theoretic and multi-model inference approach based on generalized linear mixed models, we assessed multiple environmental variables (depth, kelp density, kelp substrate, temperature, and wave exposure) as predictors of the abundance of multiple life stages of M. membranacea, investigating species-environment relationships and relative and absolute variable importance. We found that the relative importance of a predictor, the metric calculated to represent a predictor, and whether a predictor was proximal or distal were important considerations in the variable selection process. Data constraints (e.g. sample size, characteristics of available predictor data) may inhibit accurate assessment of predictor variables during variable selection. Importantly, our results suggest that species-environment relationships derived from small-scale studies can inform variable selection for SDMs at larger spatiotemporal scales. We developed a conceptual framework for variable selection for SDMs which can be applied to most contexts of species distribution modelling, but particularly those with several candidate predictors and a large dataset.

The two commonest kelp-encrusting bryozoans, and , are difficult to distinguish morphologically. Molecular studies of should thus be helpful for the identification of both species because the mitogenome of was already sequenced. The complete mitogenome of collected from Sinjido was determined in this study through Illumina NovaSeq sequencing. Maximum-likelihood (ML) analysis was based on concatenated 13 protein-coding genes dataset from nine bryozoan species. The mitogenome length was 15,407 bp, and its gene arrangement was similar to those of the mitogenome of other membraniporids, having 13 PCGs, two ribosomal RNAs, and 22 tRNAs. It had an overall A + T content of 63.7% (29.7% A, 16.7% C, 19.6% G, and 34.0% T). and showed sequence differences of 20% for the total length of mitogenome and 16.1.% for 13 PCGs. Molecular data definitely consider them to be separate species. Phylogenetic analyses based on the amino acids of 13 PCGs indicated that has the closest relationship with another kelp-encrusting bryozoan, of membraniporids. The phylogenetic position of genera and families within the suborder Membraniporina coincides with the Bayesian phylogenetic analysis of the mixed concatenated alignment consisting of three partitions.

Connectivity via the transport of detrital material from areas of high to low productivity may be an important determinant of secondary productivity and biodiversity in receiving communities. On the Atlantic coast of Nova Scotia, detritus exported from subtidal kelp beds contributes to food webs in communities inhabiting deeper waters offshore. To estimate the amount of energy available via this pathway, we measured rates of detrital production via erosion of kelp blades in kelp beds at 5 sites varying in wave exposure. Specifically, we measured productivity and erosion of the 2 dominant species of kelp,Laminaria digitataandSaccharina longicruris, over 16 mo. We also examined the effect of environmental and biological factors on erosion rates, including temperature, wave exposure, grazing by snails and cover by the invasive bryozoanMembranipora membranacea. We observed clear seasonal and spatial patterns in productivity, with the highest production in spring. Erosion rate was highly variable across sites and seasons, and was strongly related to the cover ofM. membranaceaand the intensity of snail grazing at the distal end of kelp blades. Both factors cause tissue degradation, abrasions and perforations that weaken blades. Erosion rate was also positively related to water temperature and site exposure. Annual detrital production from the erosion of kelp blades increased linearly with kelp bed biomass, and ranged from 0.5 to 1.71 kg dry weight m–2(150–513 g C m–2) across sites. These rates equal or exceed annual phytoplankton production off the Atlantic coast of Nova Scotia and estimates of detrital production in seagrass beds in North America.

Macroalgae provide surfaces where other organisms live. Unlike organisms on rigid substrata, epibionts on host macroalgae sit on flexible surfaces that bend, stretch, and move in turbulent water currents and waves. We used blade-like red algae, Mazzaella splendens , and encrusting bryozoans, Membranipora membranacea , to investigate the biomechanical and hydrodynamic effects of encrusting epibionts on macroalgae, and of flexible hosts on epibiotic bryozoans. Passive flapping by algae in wave-driven ambient flow enhanced renewal of water near hosts and epibionts. Wave exposure and the presence of a surrounding canopy of flexible algae altered the locations along algal blades where bryozoans encountered the highest time-averaged boundary shear velocities. Hydrodynamic forces on flexible algae moving back-and-forth with the water were lower in waves than in unidirectional flow. Bryozoan epibionts increased hydrodynamic forces on host algae by affecting their reconfiguration in moving water. Encrusting bryozoans increased the flexural stiffness of algal blades, but the elastic modulus, extensibility, and strength of blade tissue was unaffected by bryozoan epibionts. Algal blades were more extensible and stronger than bryozoans, so bryozoans fractured or popped off stretched algae. Algae in rapid-flow habitats had few epibionts, and encrusted algae transplanted from a protected to a wave-exposed habitat lost their epibionts.

Predicting the effect of climate change on communities requires an understanding of the effects of environmental conditions on species and their interactions. We investigated the potential for warming seawater temperature to modify the interactions of the gastropod mesograzer Lacuna vincta and the invasive bryozoan Membranipora membranacea with kelps in Nova Scotia. The nutritional content (C/N) of the kelps Saccharina latissima, Laminaria digitata and Agarum 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 phlorotannin content increased over the season in S. latissima collected monthly in summer 2013 and 2014. The effect of temperature-induced changes in kelp on the grazing of L. vincta was assessed using feeding experiments with S. latissima pretreated at 11 or 21°C. Snails consumed more kelp pretreated at 21°C only when grazing rate was high. The quality of S. latissima as a food source for L. vincta was not affected by temperature, as diets of kelp pretreated at 11 and 21°C supported similar growth, reproduction, and survival of snails. Temperature also did not affect the quality of kelp as a substrate for M. membranacea, since settlement rates were not different between S. 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 act additively with the direct effects of temperature and cause increased biomass loss from kelp beds.

Biofouling on cultivated kelp in open sea conditions is a challenge when fouling species such as the encrusting bryozoans Membranipora membranacea and Electra pilosa develop colonies that cover the surface of the kelp lamina. The bryozoan colonies make the flexible lamina brittle and susceptible to breakage and reduce the commercial value of the biomass for both human consumption and industrial applications. The development of the bryozoan fouling on cultivated Saccharina latissima in temperate coastal waters was studied at two locations in Norway from April to September. The time of settling and development of colonies of M. membranacea and E. pilosa were characterized. Sampling of bryozoan larvae abundance at the cultivation locations showed that the bryozoan colonies settled on the cultivated kelp in mid-June at both locations, followed by a rapid colony growth during late June and July. In August and September, the kelp was highly degraded by the bryozoan coverage and highly subjected to breakage of the lamina. Membranipora membranacea was the most prevailing of the two species. Although abundant at all cultivation depths, the results showed a decrease in bryozoan coverage with increasing depth. From a commercial point of view, S. latissima deployed in temperate Norwegian coastal waters in winter should be harvested in early June to avoid the negative impact from bryozoan fouling.

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.

Colonial animals can grow in a wide variety of shapes and sizes, but certain forms have apparently evolved several times in different taxa. Using adaptive arguments to explain the evolution of colony form is tempting, but when testing the functional advantage of different colony forms, controlling for species differences is difficult. In this study, 1 species of bryozoan, Membranipora membranacea (Linnaeus, 1767), was grown into different colony shapes and sizes to test how colony form affected feeding performance. Clearance rate was measured for 3 colony forms (encrusting sheet, erect sheet, erect tree), and zooid ingestion rate was measured for 5 colony sizes (comprising of 1, 8, 16, 125, or 975 zooids). The 2 erect forms had higher clearance rates than did the encrusting sheet form at a freestream velocity of 3 cm s super(-1). At this velocity, erect colonies experienced less refiltration and yet benefited from feeding in a downstream wake. For encrusting colonies the change in ingestion rate per zooid with colony size was non-linear. Overall, zooid ingestion rate increased from 1 to 16 zooids, decreased for small colonies (with ~125 zooids), and then increased again for medium colonies (with ~975 zooids). Colonies with 8 or more zooids had higher feeding success than single zooids, suggesting a feeding advantage to zooids in a colony. Conversely, small and medium colonies had lower mean ingestion rates than colonies with 8 or 16 zooids, suggesting a feeding cost for increasing beyond a relatively small size.

Ocean acidification (OA) from in creased 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 water-borne predator cue, and on zooid consumption rates in Corambe at Friday Harbor Laboratories, San Juan Is land, 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.