Biogeographical patterns of endolithic infestation in an invasive and an indigenous intertidal marine ecosystem engineer

By altering the phenotypic properties of their hosts, endolithic parasites can modulate the engineering processes of marine ecosystem engineers. Here, we assessed the biogeographical patterns of species assemblages, prevalence and impact of endolithic parasitism in two mussel species that act as important ecosystem engineers in the southern African intertidal habitat, Perna perna and Mytilus galloprovincialis. We conducted large-scale surveys across three biogeographic regions along the South African coast: the subtropical east coast, dominated by the indigenous mussel, P. perna, the warm temperate south coast, where this species coexists with the invasive Mediterranean mussel, M. galloprovincialis, and the cool temperate west coast dominated by M. galloprovincialis. Infestation increased with mussel size, and in the case of M. galloprovincialis we found a significantly higher infestation in the cool temperate bioregion than the warm temperate region. For P. perna, the prevalence of infestation was higher on the warm temperate than the subtropical region, though the difference was marginally non-significant. On the south coast, there was no significant difference in infestation prevalence between species. Endolith-induced mortality rates through shell collapse mirrored the patterns for prevalence. For P. perna, endolith species assemblages revealed clear grouping by bioregions. Our findings indicate that biogeography affects cyanobacteria species composition, but differences between biogeographic regions in their effects are driven by environmental conditions.Agência financiadora Número do subsídio Fundacao para a Ciencia e Tecnologia (FCT-MEC, Portugal) UID/Multi/04326/2019 IF/01413/2014/CP1217/CT0004 South African Research Chairs Initiative (SARChI) of the Department of Science and Technology National Research Foundationinfo:eu-repo/semantics/publishedVersio

Applicability of Dynamic Energy Budget (DEB) models across steep environmental gradients

Abstract Robust ecological forecasting requires accurate predictions of physiological responses to environmental drivers. Energy budget models facilitate this by mechanistically linking biology to abiotic drivers, but are usually ground-truthed under relatively stable physical conditions, omitting temporal/spatial environmental variability. Dynamic Energy Budget (DEB) theory is a powerful framework capable of linking individual fitness to environmental drivers and we tested its ability to accommodate variability by examining model predictions across the rocky shore, a steep ecotone characterized by wide fluctuations in temperature and food availability. We parameterized DEB models for co-existing mid/high-shore (Mytilus galloprovincialis) and mid/low-shore (Perna perna) mussels on the south coast of South Africa. First, we assumed permanently submerged conditions, and then incorporated metabolic depression under low tide conditions, using detailed data of tidal cycles, body temperature and variability in food over 12 months at three sites. Models provided good estimates of shell length for both species across the shore, but predictions of gonadosomatic index were consistently lower than observed. Model disagreement could reflect the effects of details of biology and/or difficulties in capturing environmental variability, emphasising the need to incorporate both. Our approach provides guidelines for incorporating environmental variability and long-term change into mechanistic models to improve ecological predictions

Conservation of thermal physiology in tropical intertidal snails following an evolutionary transition to a cooler ecosystem: climate change implications

Predictions for animal responses to climate warming usually assume that thermal physiology is adapted to present-day environments, and seldom consider the influence of evolutionary background. Little is known about the conservation of warm-adapted physiology following an evolutionary transition to a cooler environment. We used cardiac thermal performance curves (cTPCs) of six neritid gastropod species to study physiological thermal trait variation associated with a lineage transition from warmer rocky shores to cooler mangroves. We distinguished between functional thermal performance traits, related to energy homeostasis (slope gradient, slope curvature, HRmax, maximum cardiac activity and T-opt, the temperature that maximizes cardiac activity) and a trait that limits performance (ULT, the upper lethal temperature). Considering the theory of optimal thermal performance, we predicted that the functional traits should be under greater selective pressure to change directionally and in magnitude than the thermal limit, which is redundant in the cooler environment. We found little variation in all traits across species, habitats and ecosystems, despite a similar to 20 degrees C reduction in maximum habitat temperature in the mangrove species over 50 million years. While slope gradient was significantly lowered in the mangrove species, the effect difference was negated by greater thermal plasticity in the rocky shore species. ULT showed the least variation and suggested thermal specialization in the warmest habitat studied. The observed muted variation of the functional traits among the species may be explained by their limited role in energy acquisition and rather their association with heat tolerance adaptation, which is redundant in the mangrove species. These findings have implications for the conservation of habitat of intertidal gastropods that transition to cooler environments. Furthermore, they highlight the significance of evolutionary history and physiological conservation when predicting species responses to climate change

The influence of intertidal location and temperature on the metabolic cost of emersion in Pisaster ochraceus

International audienceVertical zonation within the intertidal results from an interaction between the physical environment and an organism's physiological limits. Bioenergetic costs of emersion are likely to vary based on an organism's vertical location in the intertidal. The present study quantified the metabolic costs of microhabitat choice in the important intertidal predator Pisaster ochraceus. Rates of oxygen consumption (VO2) were measured at a range of ecologically relevant temperatures in both water and air. In both media, rates increased with increasing temperature but, at any given temperature, aerial VO2 was approximately 50% that of aquatic VO2. These rates, along with biomimetic body temperature data from two field sites in Bodega Bay, California, were used to estimate the metabolism of sea stars at different vertical locations over a 10-day period in the summers of 2006, 2007, and 2010. Results suggest that vertical location would have a much smaller effect on sea star VO2 than would inter-annual temperature differences. The influence of higher body temperatures experienced by sea stars at low tide in the mid-high intertidal, as compared to the low intertidal, was almost negligible because aerial VO2 was lower than aquatic VO2. By contrast, the higher average water temperature experienced by sea stars in 2006 yielded a 50% higher metabolic cost relative to sea stars in 2007 and 2010. These results suggest that energetic demands of intertidal organisms can vary markedly according to global environmental fluctuations such as El Niño and Pacific Decadal Oscillations

Bioeconomic MPA network design - R toolkit v0.1.1

<p>The second alpha release of our toolkit to assess costs and benefits related to marine protected area network design.<br>Includes minor changes to the plotting of the publication figures and corrected some errors in the readme.</p

Bioeconomic MPA network design - Cod case study output

<p>Model data from the case study on MPA design for Atlantic Cod generated by:</p> <p>http://dx.doi.org/10.6084/m9.figshare.1556143</p> <p>Please unzip shapefiles folder before trying to reproduce analysis</p

<i>Pisaster ochraceus</i> DEB parameter values, and results of sensitivity analysis.

1<p>Estimated directly from data.</p>2<p>Estimated using covariation method (DEBtool).</p>3<p>Estimated using grid-search.</p>4<p>Kept fixed.</p><p>Sensitivity is the percent change in arm length at age 2 y divided by the percent change in a single parameter value (10%). Analyses were carried out using <i>ad libitum</i> food, at a temperature of 13°C. Parameters with a negative relation to growth are printed in bold type. Sensitivity of parameters not estimated is NaN.</p><p><i>Pisaster ochraceus</i> DEB parameter values, and results of sensitivity analysis.</p

Schematic representation of standard Dynamic Energy Budget model.

<p>Arrows represent energy fluxes (J d⁻¹) that drive the dynamics of the four state variables, depicted in boxes (Reserve, Structure, Maturation, and Reproductive Buffer). Energy enters the animal as food, and then assimilated at a rate into Reserves. Mobilization rate, , regulates energy fluxes to cover the demands from somatic maintenance, , structural growth, , maturity maintenance, , maturation, (immature individuals), and reproduction, (mature individuals). The parameter kappa () is the proportion of mobilized energy diverted to and , while the rest (1−) is used for and . Formulations explaining these fluxes are given in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104658#pone.0104658.s001" target="_blank">Appendix S1</a>. Overheads associated to assimilation, growth and reproduction arise due to thermodynamic inefficiencies when transforming between substrates.</p

Larval growth from 0 to 27 d after birth.

<p>Birth is considered as the day when larvae begin feeding. Laboratory data (from citation <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0104658#pone.0104658-Richmond1" target="_blank">[29]</a>) are shown as dots. The line comes from a Dynamic Energy Budget model simulation, assuming <i>ad libitum</i> food and 12°C water temperature. Root Mean Square (RMS) error, Mean Absolute Error (MAE), and Mean Absolute Percent Error (MAPE) are shown.</p

Temperature sensitivity.

<p>Observed values (circles) represent relative values of oxygen consumption and feeding rate (coldest temperature treatment) determined at a range of water temperatures from 278 to 299 K. The line of best fit was obtained by first estimating Arrhenius temperature, , and then running a grid-search to find the combination of parameter values for (lower limit of tolerance range), (higher limit of tolerance range), (Arrhenius temperature at lower limit), and (Arrhenius temperature at higher limit) that minimized the RMSE between observed and simulated data.</p