Local-Scale Thermal History Influences Metabolic Response of Marine Invertebrates To Warming

As climate change continues, anticipating species’ responses to rising temperatures, requires an understanding of the relationship between metabolic rate and thermal sensitivity, which itself may vary over space and time. We measured metabolic rates of three representative marine invertebrate species (hermit crabs Pagurus hirsutiusculus, periwinkle snails Littorina sitkana, and mussels Mytilus trossulus) and evaluated the relationship between thermal sensitivity (Q10) and thermal history. We tested the hypothesis that thermal history drives thermal sensitivity and quantified how this relationship differs over time (short-term to seasonal time scales) and between species. Organisms were collected from tide pools in Sitka, Alaska where we also recorded temperatures to characterize thermal history prior to metabolic rate assays. Using respirometry, we estimated mass-specific oxygen consumption (MO2) at ambient and increased temperatures for one individual per species per tide pool across three seasons. We evaluated relationships between thermal sensitivity and pool temperatures for time periods ranging from 1 day to 3 months prior to collection. For all species, thermal sensitivity was related to thermal history for the shorter time periods (1 day to 1 week). However, the direction of the relationships and most important thermal parameters (i.e., maximum, mean, or range) differed between species and seasons. We found that on average, P. hirsutiusculus and L. sitkana were more thermally sensitive than M. trossulus. These findings show that variability in thermal history over small spatial scales influences individuals’ metabolic response to warming and may be indicative of these species’ ability to acclimate to future climate change.

Stress Resistance in an Extreme Environment: Lessons Learnt from a Temperate Symbiotic Sea Anemone

<p>Coral bleaching, the loss of symbiotic dinoflagellates (zooxanthellae) or their photosynthetic pigments in response to environmental stress, is of huge global concern. In contrast to tropical corals, which are highly sensitive to fluctuations in environmental parameters such as temperature, light and salinity, zooxanthellate invertebrates in temperate waters rarely bleach despite highly variable conditions. In this study, we tested the effects of salinity with combined effects of light and temperature stress on the photophysiology and stability of the temperate symbiotic sea anemone, Anthopleura aureoradiata, through chlorophyll fluorescence. In the field it was demonstrated that A. aureoradiata was resilient to abiotic fluctuations of considerable magnitude in the intertidal zone. Salinity was revealed to range naturally between a winter low of 30 and summer high of 40 ppt in an elevated tide pool with no measurable effects on the photophysiology of A. aureoradiata residing within. In a controlled environment, only extreme high and low salinities had an effect on the zooxanthellar photosystem, with a wide range of tolerance between 15-50 ppt dependent on the levels of temperature and light. Both high and low light, and temperature, also impacted upon photophysiology. Moreover, each of these variables independently, as well as combined, exacerbated the impact of salinity stress. In addition, the duration of exposure played an important role in the survival of this symbiosis, with only 48-96 h exposure to the extreme salinities of 5, 10, 55 and 60 ppt inducing irreversible photosynthetic failure, bleaching and death. Thus, the data supports the idea that this anemone-zooxanthellar symbiosis is highly resilient to considerable amounts of abiotic stress, a likely a function of the robust photophysiology of its zooxanthellae. This resilience to bleaching suggests that A. aureoradiata and its zooxanthallae have evolved a combination of powerful defensive mechanisms to help aid against the heterogenous environment from which they come. I will present an overview of these osmoregulatory mechanisms, photoacclimatory strategies and behaviours that this symbiosis likely deploys in order to combat environmentally realistic ranges in abiotic factors. Further studies would be necessary to deduce whether it is the host or zooxanthellae which are responsible for the breakdown of this symbiosis.</p>

Stress Resistance in an Extreme Environment: Lessons Learnt from a Temperate Symbiotic Sea Anemone

<p>Coral bleaching, the loss of symbiotic dinoflagellates (zooxanthellae) or their photosynthetic pigments in response to environmental stress, is of huge global concern. In contrast to tropical corals, which are highly sensitive to fluctuations in environmental parameters such as temperature, light and salinity, zooxanthellate invertebrates in temperate waters rarely bleach despite highly variable conditions. In this study, we tested the effects of salinity with combined effects of light and temperature stress on the photophysiology and stability of the temperate symbiotic sea anemone, Anthopleura aureoradiata, through chlorophyll fluorescence. In the field it was demonstrated that A. aureoradiata was resilient to abiotic fluctuations of considerable magnitude in the intertidal zone. Salinity was revealed to range naturally between a winter low of 30 and summer high of 40 ppt in an elevated tide pool with no measurable effects on the photophysiology of A. aureoradiata residing within. In a controlled environment, only extreme high and low salinities had an effect on the zooxanthellar photosystem, with a wide range of tolerance between 15-50 ppt dependent on the levels of temperature and light. Both high and low light, and temperature, also impacted upon photophysiology. Moreover, each of these variables independently, as well as combined, exacerbated the impact of salinity stress. In addition, the duration of exposure played an important role in the survival of this symbiosis, with only 48-96 h exposure to the extreme salinities of 5, 10, 55 and 60 ppt inducing irreversible photosynthetic failure, bleaching and death. Thus, the data supports the idea that this anemone-zooxanthellar symbiosis is highly resilient to considerable amounts of abiotic stress, a likely a function of the robust photophysiology of its zooxanthellae. This resilience to bleaching suggests that A. aureoradiata and its zooxanthallae have evolved a combination of powerful defensive mechanisms to help aid against the heterogenous environment from which they come. I will present an overview of these osmoregulatory mechanisms, photoacclimatory strategies and behaviours that this symbiosis likely deploys in order to combat environmentally realistic ranges in abiotic factors. Further studies would be necessary to deduce whether it is the host or zooxanthellae which are responsible for the breakdown of this symbiosis.</p>

The Purple Sea Urchin Strongylocentrotus purpuratus Demonstrates a Compartmentalization of Gut Bacterial Microbiota, Predictive Functional Attributes, and Taxonomic Co-Occurrence

The sea urchin Strongylocentrotus purpuratus (order Camarodonta, family Strongylocentrotidae) can be found dominating low intertidal pool biomass on the southern coast of Oregon, USA. In this case study, three adult sea urchins were collected from their shared intertidal pool, and the bacteriome of their pharynx, gut tissue, and gut digesta, including their tide pool water and algae, was determined using targeted high-throughput sequencing (HTS) of the 16S rRNA genes and bioinformatics tools. Overall, the gut tissue demonstrated Arcobacter and Sulfurimonas (Epsilonproteobacteria) to be abundant, whereas the gut digesta was dominated by Psychromonas (Gammaproteobacteria), Propionigenium (Fusobacteria), and Flavobacteriales (Bacteroidetes). Alpha and beta diversity analyses indicated low species richness and distinct microbial communities comprising the gut tissue and digesta, while the pharynx tissue had higher richness, more closely resembling the water microbiota. Predicted functional profiles showed Kyoto Encyclopedia of Genes and Genomes (KEGG) Level-2 categories of energy metabolism, membrane transport, cell motility, and signal transduction in the gut tissue, and the gut digesta represented amino acid, carbohydrate, vitamin and cofactor metabolisms, and replication and repair. Co-occurrence network analysis showed the potential relationships and key taxa, such as the highly abundant Arcobacter and Propionigenium, influencing population patterns and taxonomic organization between the gut tissue and digesta. These results demonstrate a trend of microbial community integration, allocation, predicted metabolic roles, and taxonomic co-occurrence patterns in the S. purpuratus gut ecosystem.

Integrative taxonomy widens our knowledge of the diversity, distribution and biology of the genus Plakina (Homosclerophorida: Plakinidae)

Despite the evolutionary significance of Homoscleromorpha, their diversity and biology are largely unknown. Here we integrate data of morphology, cytology, microbiology, ecology, reproduction, and mitochondrial cox-1 and cob gene sequences to resolve a complex of sympatric species of Plakina in South-eastern Brazil. All datasets congruently supported the delimitation of three species, two of which are new to science. Plakina coerulea has its distribution extended from one locality to over 2360 km wide. Plakina cabofriense, sp. nov. also occurs in North-eastern Brazil. Plakina cyanorosea, sp. nov. occurs only in a single, small tide pool and may be critically endangered. Plakina cyanorosea, sp. nov. produces conspicuous, abundant larvae useful for laboratory investigations. A thin, bright orange organic coat covers some spicules of P. cabofriense, sp. nov. and P. cyanorosea, sp. nov. The three Plakina species harbour diverse microbial symbiont communities, including previously unknown morphologies. Molecular phylogenies and barcoding gaps based on cox-1 and cob sequences supported that each species is monophyletic and distinct from other congeners. The genus Plakina is paraphyletic and strongly needs redefinition. The integrative approach provides new data that widens our knowledge of Homoscleromorpha diversity, distribution and biology.