Organismal defenses versus environmentally mediated protection from herbivores: Unraveling the puzzling case of Desmarestia viridis (Phaeophyta)

Abstract The role of anti-herbivore organismal defenses in algae-herbivore interaction is frequently investigated without taking into account the potential role of environmental factors in mediating the interaction. Here we reexamine the interaction between the highly acidic, brown alga Desmarestia viridis and the green sea urchin, Strongylocentrotus droebachiensis, by incorporating a previously overlooked facet, the effect of changes in the wave environment on the ability of the urchin to establish contact with the alga. Factorial experiments in a wave tank (presence versus absence of waves; real versus mimic algae) showed that the aggregation of urchins on D. viridis was more than 2-fold greater in the absence than in the presence of waves. Similar numbers of urchins made contact with natural and mimic D. viridis plants, both with and without waves, indicating that any external release of chemicals (acid) from the alga had no perceptible repulsive effect on the urchin. The ability of the urchins to climb onto D. viridis increased markedly when urchin density attained a critical level. These results were consistent with field observations that urchins readily attack D. viridis under conditions of low wave action but do not under conditions of moderate wave action. We conclude (1) that the chemical makeup of D. viridis alone is neither necessary nor sufficient to limit contacts by the urchins and that (2) wave action is a major factor explaining the survival of D. viridis on urchin barrens, because waves limit the movements of the urchins towards the alga. We recommend that studies addressing marine algal defenses against herbivores be more comprehensive and examine interactions between algal traits, the physical environment, and the abundance and behavioral repertoire of herbivores

Kelp in the Eastern Canadian Arctic: current and future predictions of habitat suitability and cover

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Goldsmit, J., Schlegel, R. W., Filbee-Dexter, K., MacGregor, K. A., Johnson, L. E., Mundy, C. J., Savoie, A. M., McKindsey, C. W., Howland, K. L., & Archambault, P. Kelp in the Eastern Canadian Arctic: current and future predictions of habitat suitability and cover. Frontiers in Marine Science, 18, (2021): 742209. https://doi.org/10.3389/fmars.2021.742209Climate change is transforming marine ecosystems through the expansion and contraction of species’ ranges. Sea ice loss and warming temperatures are expected to expand habitat availability for macroalgae along long stretches of Arctic coastlines. To better understand the current distribution of kelp forests in the Eastern Canadian Arctic, kelps were sampled along the coasts for species identifications and percent cover. The sampling effort was supplemented with occurrence records from global biodiversity databases, searches in the literature, and museum records. Environmental information and occurrence records were used to develop ensemble models for predicting habitat suitability and a Random Forest model to predict kelp cover for the dominant kelp species in the region – Agarum clathratum, Alaria esculenta, and Laminariaceae species (Laminaria solidungula and Saccharina latissima). Ice thickness, sea temperature and salinity explained the highest percentage of kelp distribution. Both modeling approaches showed that the current extent of arctic kelps is potentially much greater than the available records suggest. These modeling approaches were projected into the future using predicted environmental data for 2050 and 2100 based on the most extreme emission scenario (RCP 8.5). The models agreed that predicted distribution of kelp in the Eastern Canadian Arctic is likely to expand to more northern locations under future emissions scenarios, with the exception of the endemic arctic kelp L. solidungula, which is more likely to lose a significant proportion of suitable habitat. However, there were differences among species regarding predicted cover for both current and future projections. Notwithstanding model-specific variation, it is evident that kelps are widespread throughout the area and likely contribute significantly to the functioning of current Arctic ecosystems. Our results emphasize the importance of kelp in Arctic ecosystems and the underestimation of their potential distribution there.This work was supported by ArcticNet (P101 ArcticKelp), Fisheries and Oceans Canada Arctic Climate Change Adaptation Strategy, Arctic Science and Aquatic Invasive Species Monitoring and Research Funds, the Natural Sciences and Engineering Research Council (NSERC), NRCan Polar Continental Shelf Program Support, Canadian Aquatic Invasive Species Network (CAISN), the Nunavut Marine Region Wildlife Management Board (NWMB), Quebec-Ocean, and the Ocean Frontier Institute through an award from the Canada First Research Excellence Fund, the Marine Environmental Observation, Prediction and Response Network of Centres of Excellence’s (MEOPAR-NCE) Southampton Island Marine Ecosystem Project, and the Belmont Forum–BiodivERsA’s De-icing of Arctic Coasts: critical or new opportunities for marine biodiversity and Ecosystem Services (ACCES). KF-D was supported by the Australian Research Council (DE190100692)

Sea Ice and Substratum Shape Extensive Kelp Forests in the Canadian Arctic

The coastal zone of the Canadian Arctic represents 10% of the world’s coastline and is one of the most rapidly changing marine regions on the planet. To predict the consequences of these environmental changes, a better understanding of how environmental gradients shape coastal habitat structure in this area is required. We quantified the abundance and diversity of canopy forming seaweeds throughout the nearshore zone (5–15 m) of the Eastern Canadian Arctic using diving surveys and benthic collections at 55 sites distributed over 3,000 km of coastline. Kelp forests were found throughout, covering on average 40.4% (±29.9 SD) of the seafloor across all sites and depths, despite thick sea ice and scarce hard substrata in some areas. Total standing macroalgal biomass ranged from 0 to 32 kg m–2 wet weight and averaged 3.7 kg m–2 (±0.6 SD) across all sites and depths. Kelps were less abundant at depths of 5 m compared to 10 or 15 m and distinct regional assemblages were related to sea ice cover, substratum type, and nutrient availability. The most common community configuration was a mixed assemblage of four species: Agarum clathratum (14.9% benthic cover ± 12.0 SD), Saccharina latissima (13% ± 14.7 SD), Alaria esculenta (5.4% ± 1.2 SD), and Laminaria solidungula (3.7% ± 4.9 SD). A. clathratum dominated northernmost regions and S. latissima and L. solidungula occurred at high abundance in regions with more open water days. In southeastern areas along the coast of northern Labrador, the coastal zone was mainly sea urchin barrens, with little vegetation. We found positive relationships between open water days (days without sea ice) and kelp biomass and seaweed diversity, suggesting kelp biomass could increase, and the species composition of kelp forests could shift, as sea ice diminishes in some areas of the Eastern Canadian Arctic. Our findings demonstrate the high potential productivity of this extensive coastal zone and highlight the need to better understand the ecology of this system and the services it provides.publishedVersio

Oralism: a sign of the times? The contest for deaf communication in education provision in late nineteenth-century Scotland

Disability history is a diverse field. In focussing upon children within deaf education in late nineteenth-century Scotland, this essay reflects some of that diversity. In 1880, the International Congress on the Education of the Deaf in Milan stipulated that speech should have ‘preference’ over signs in the education of deaf children. The mode of achieving this, however, effectively banned sign language. Endeavours to teach deaf children to articulate were not new, but this decision placed pressures on deaf institutions to favour the oral system of deaf communication over other methods. In Scotland efforts were made to adopt oralism, and yet educators were faced with the reality that this was not good educational practice for most pupils. This article will consider responses of Scottish educators of deaf children from the 1870s until the beginning of the twentieth century

Large introns in relation to alternative splicing and gene evolution: a case study of Drosophila bruno-3

Background: Alternative splicing (AS) of maturing mRNA can generate structurally and functionally distinct transcripts from the same gene. Recent bioinformatic analyses of available genome databases inferred a positive correlation between intron length and AS. To study the interplay between intron length and AS empirically and in more detail, we analyzed the diversity of alternatively spliced transcripts (ASTs) in the Drosophila RNA-binding Bruno-3 (Bru-3) gene. This gene was known to encode thirteen exons separated by introns of diverse sizes, ranging from 71 to 41,973 nucleotides in D. melanogaster. Although Bru-3's structure is expected to be conducive to AS, only two ASTs of this gene were previously described. Results: Cloning of RT-PCR products of the entire ORF from four species representing three diverged Drosophila lineages provided an evolutionary perspective, high sensitivity, and long-range contiguity of splice choices currently unattainable by high-throughput methods. Consequently, we identified three new exons, a new exon fragment and thirty-three previously unknown ASTs of Bru-3. All exon-skipping events in the gene were mapped to the exons surrounded by introns of at least 800 nucleotides, whereas exons split by introns of less than 250 nucleotides were always spliced contiguously in mRNA. Cases of exon loss and creation during Bru-3 evolution in Drosophila were also localized within large introns. Notably, we identified a true de novo exon gain: exon 8 was created along the lineage of the obscura group from intronic sequence between cryptic splice sites conserved among all Drosophila species surveyed. Exon 8 was included in mature mRNA by the species representing all the major branches of the obscura group. To our knowledge, the origin of exon 8 is the first documented case of exonization of intronic sequence outside vertebrates. Conclusion: We found that large introns can promote AS via exon-skipping and exon turnover during evolution likely due to frequent errors in their removal from maturing mRNA. Large introns could be a reservoir of genetic diversity, because they have a greater number of mutable sites than short introns. Taken together, gene structure can constrain and/or promote gene evolution

Kelp carbon sink potential decreases with warming due to accelerating decomposition

Cycling of organic carbon in the ocean has the potential to mitigate or exacerbate global climate change, but major questions remain about the environmental controls on organic carbon flux in the coastal zone. Here, we used a field experiment distributed across 28° of latitude, and the entire range of 2 dominant kelp species in the northern hemisphere, to measure decomposition rates of kelp detritus on the seafloor in relation to local environmental factors. Detritus decomposition in both species were strongly related to ocean temperature and initial carbon content, with higher rates of biomass loss at lower latitudes with warmer temperatures. Our experiment showed slow overall decomposition and turnover of kelp detritus and modeling of coastal residence times at our study sites revealed that a significant portion of this production can remain intact long enough to reach deep marine sinks. The results suggest that decomposition of these kelp species could accelerate with ocean warming and that low-latitude kelp forests could experience the greatest increase in remineralization with a 9% to 42% reduced potential for transport to long-term ocean sinks under short-term (RCP4.5) and long-term (RCP8.5) warming scenarios. However, slow decomposition at high latitudes, where kelp abundance is predicted to expand, indicates potential for increasing kelp-carbon sinks in cooler (northern) regions. Our findings reveal an important latitudinal gradient in coastal ecosystem function that provides an improved capacity to predict the implications of ocean warming on carbon cycling. Broad-scale patterns in organic carbon decomposition revealed here can be used to identify hotspots of carbon sequestration potential and resolve relationships between carbon cycling processes and ocean climate at a global scale.publishedVersio