A Pleistocene legacy structures variation in modern seagrass ecosystems

Distribution of Earth's biomes is structured by the match between climate and plant traits, which in turn shape associated communities and ecosystem processes and services. However, that climate-trait match can be disrupted by historical events, with lasting ecosystem impacts. As Earth's environment changes faster than at any time in human history, critical questions are whether and how organismal traits and ecosystems can adjust to altered conditions. We quantified the relative importance of current environmental forcing versus evolutionary history in shaping the growth form (stature and biomass) and associated community of eelgrass (Zostera marina), a widespread foundation plant of marine ecosystems along Northern Hemisphere coastlines, which experienced major shifts in distribution and genetic composition during the Pleistocene. We found that eelgrass stature and biomass retain a legacy of the Pleistocene colonization of the Atlantic from the ancestral Pacific range and of more recent within-basin bottlenecks and genetic differentiation. This evolutionary legacy in turn influences the biomass of associated algae and invertebrates that fuel coastal food webs, with effects comparable to or stronger than effects of current environmental forcing. Such historical lags in phenotypic acclimatization may constrain ecosystem adjustments to rapid anthropogenic climate change, thus altering predictions about the future functioning of ecosystems.This work was supported by the US NSF (OCE-1031061, OCE-1336206, OCE0-1336741, OCE-1336905) and the Smithsonian Institution. F.T. was supported by José Castillejo Award CAS14/00177. A.H.E. was supported by the FCT (Foundation for Science and Technology) through Project UIDB/04326/2020 and Contract CEECINST/00114/2018. This is Contribution 106 from the Smithsonian’s MarineGEO and Tennenbaum Marine Observatories Network and Contribution 4105 of the Virginia Institute of Marine Science, College of William & Mary

Specific niche requirements underpin multidecadal range edge stability, but may introduce barriers for climate change adaptation

Aim: To investigate some of the environmental variables underpinning the past and present distribution of an ecosystem engineer near its poleward range edge. Location: >500 locations spanning >7,400 km around Ireland. Methods: We collated past and present distribution records on a known climate change indicator, the reef-forming worm Sabellaria alveolata (Linnaeus, 1767) in a biogeographic boundary region over 182 years (1836–2018). This included repeat sampling of 60 locations in the cooler 1950s and again in the warmer 2000s and 2010s. Using species distribution modelling, we identified some of the environmental drivers that likely underpin S. alveolata distribution towards the leading edge of its biogeographical range in Ireland. Results: Through plotting 981 records of presence and absence, we revealed a discontinuous distribution with discretely bounded sub-populations, and edges that coincide with the locations of tidal fronts. Repeat surveys of 60 locations across three time periods showed evidence of population increases, declines, local extirpation and recolonization events within the range, but no evidence of extensions beyond the previously identified distribution limits, despite decades of warming. At a regional scale, populations were relatively stable through time, but local populations in the cold Irish Sea appear highly dynamic and vulnerable to local extirpation risk. Contemporary distribution data (2013–2018) computed with modelled environmental data identified specific niche requirements which can explain the many distribution gaps, namely wave height, tidal amplitude, stratification index, then substrate type. Main conclusions: In the face of climate warming, such specific niche requirements can create environmental barriers that may prevent species from extending beyond their leading edges. These boundaries may limit a species’ capacity to redistribute in response to global environmental change

Climate drives the geography of marine consumption by changing predator communities

Este artículo contiene 7 páginas, 3 figuras, 1 tabla.The global distribution of primary production and consumption by humans (fisheries) is well-documented, but we have no map linking the central ecological process of consumption within food webs to temperature and other ecological drivers. Using standardized assays that span 105° of latitude on four continents, we show that rates of bait consumption by generalist predators in shallow marine ecosystems are tightly linked to both temperature and the composition of consumer assemblages. Unexpectedly, rates of consumption peaked at midlatitudes (25 to 35°) in both Northern and Southern Hemispheres across both seagrass and unvegetated sediment habitats. This pattern contrasts with terrestrial systems, where biotic interactions reportedly weaken away from the equator, but it parallels an emerging pattern of a subtropical peak in marine biodiversity. The higher consumption at midlatitudes was closely related to the type of consumers present, which explained rates of consumption better than consumer density, biomass, species diversity, or habitat. Indeed, the apparent effect of temperature on consumption was mostly driven by temperature-associated turnover in consumer community composition. Our findings reinforce the key influence of climate warming on altered species composition and highlight its implications for the functioning of Earth’s ecosystems.We acknowledge funding from the Smithsonian Institution and the Tula Foundation.Peer reviewe

Individual species provide multifaceted contributions to the stability of ecosystems

Abstract Exploration of the relationship between species diversity and ecological stability has occupied a prominent place in ecological research for decades. Yet, a key component of this puzzle—the contributions of individual species to the overall stability of ecosystems—remains largely unknown. Here, we show that individual species simultaneously stabilize and destabilize ecosystems along different dimensions of stability, and also that their contributions to functional (biomass) and compositional stability are largely independent. By simulating experimentally the extinction of consumer species from a coastal rocky shore, we found that the capacity to predict the combined contribution of species to stability from the sum of their individual contributions varied among stability dimensions. This implies that the nature of the diversity-stability relationship depends upon the dimension of stability under consideration, and may be additive, synergistic or antagonistic. We conclude that, though the profoundly multifaceted and context-dependent consequences of species loss pose a significant challenge, the predictability of cumulative species contributions to some dimensions of stability provide a way forward for ecologists trying to conserve ecosystems and manage their stability under global change. Methods This dataset contains species abundance matrices for monthly suveys of experimental plots at Glashagh bay, Fanad, Co. Donegal, Ireland (55°26’5’’N, 7°67’5’’W) over 15 months from May 2016. We measured the percent cover of macroalgae monthly using a 25 x 25 cm quadrat with 64 intersections, positioned centrally within cages to avoid sampling edge effects. Species present within the quadrat but not occurring underneath any of the intersections were assigned a cover value of 1%. We used the data set to quantify six components of ecological stability, separately for both total algal cover (as a proxy for total algal biomass) and assemblage structure as measures of, respectively, functional and compositional stability. Please see Table 1 and methods section in the associated manuscript for details on calculating stability measures. Usage Notes Please see readme in the datafile for explanations of experimental treatments, survey methods and species abreviations

The spatial separation of two distinct assemblages of dominant taxa.

<p>Spatial co-occurrence (positive correlations, bold) and separation (negative correlations) of taxa by abundance (n.b. presence/ absence for <i>L</i>. <i>nigrescens</i>), and taxa abundance associations with upwelling influence (^a<i>P</i>. <i>purpuratus</i> δ¹⁵N). All correlations are Spearman’s Rank with non-spatial p-values shown in brackets as</p><p>*** P < 0.001,</p><p>** P < 0.01,</p><p>*P < 0.05.</p><p>For clarity, only one half of the symmetrical correlation matrix has been included.</p><p>The spatial separation of two distinct assemblages of dominant taxa.</p

The distribution of sites (symbols) and macroalgal species (crosses) over environmental gradients (arrows), showing the separation of Antofagasta Bay from Mejillones Peninsula.

<p>A species-conditional triplot based on a canonical correspondence analysis, with <i>P</i>. <i>purpuratus</i> δ¹³C and δ¹⁵N included as environmental gradients. Eigenvalues of dimension 1 (horizontal) = 0.20 and dimension 2 (vertical) = 0.19; eigenvalue of the axis 3 (not displayed) = 0.09. Scale marks along the axes apply to the species and sites scores. Species crosses represent the weighted average of their ‘niche’ (by site), though labels were omitted to avoid cluttering the plot (listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130789#pone.0130789.s003" target="_blank">S2 Table</a>). Rare species which occurred at <2 sites were removed <i>a priori</i> to analysis, as recommended by Bocard et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130789#pone.0130789.ref058" target="_blank">58</a>]. Site symbols show Mejillones Peninsula (locations 2 & 3) and Bay (location 1) in black, and Antofagasta Bay (locations 4 & 5) and Coloso Point (location 6) in grey. 2D triplot displays 26.9% of total inertia (= weighted variance) in the observed occurrences and 65.3% of variance in the weighted averages and class totals of macroalgal species with respect to the environmental variables.</p

Geographical variation of standardised δ¹⁵N at sites along the coastline.

<p>The solid line shows size-corrected <i>P</i>. <i>purpuratus</i> δ¹⁵N, whilst the dashed line shows the mean (± SD) across standardised δ¹⁵N of all consumers (<i>P</i>. <i>purpuratus</i>, <i>E</i>. <i>peruviana</i>, <i>S</i>. <i>viridula</i>, <i>T</i>. <i>atra</i>) and putative resources (POM, epilithic biofilm, <i>Ulva</i> sp.). Site labels are presented below the graph in sequence around the coast, with the main geographical features summarised at the base of the graph (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130789#pone.0130789.g001" target="_blank">Fig 1</a> for more detail).</p

The anomalous warmth of Antofagasta Bay and upwelling context of the Mejillones Peninsula (arrow in map B) along the wider coastline of Northern Chile.

<p>(A) Coastal primary productivity (chlorophyll a concentration, logarithmic colour scale) and (B) cool upwelled water (sea surface temperature, SST) parallel to the coastline. (C) A ‘zoomed-in’ view of the Mejillones Peninsula with SST (note different temperature scale to ‘B’) shows ‘locations’ (10 km scale, black lines), ‘sites’ (1 km scale, small black points) and the city of Antofagasta (black diamond). All SST and chlorophyll a concentrations are mean values from estimated daily aqua MODIS satellite data [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130789#pone.0130789.ref036" target="_blank">36</a>] collected between December 2011 and February 2012 at a scale of 4.6 km. Euclidean distance from most northern to most southern sites was approximately 83 km. Where mentioned in the text, sites are numbered from ‘1’ to ‘3’ from north to south, nested within each location.</p

The geographical switching in importance of POM and brown macroalgae to the diets of intertidal consumers.

<p>Dietary contributions by resources to (<b>A</b>) the mussel <i>P</i>. <i>purpuratus</i> and (<b>B</b>) grazer species together, estimated by SIAR mixing models run separately for Mejillones Peninsula and Bay (locations 1–3), and Antofagasta Bay with Coloso Point (locations 4–6). Plotted are the 95, 75 and 50% Bayesian credibility intervals, with significance of differences between peninsula and bay estimates. ‘Brown macroalgae’ represents <i>L</i>. <i>nigrescens</i> and <i>D</i>. <i>kunthii</i>, which were combined due to isotopic similarity (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0130789#pone.0130789.g002" target="_blank">Fig 2</a>). The food webs of (<b>C</b>) Antofagasta Bay and (<b>D</b>) Mejillones Peninsula plotted figuratively. Arrow weight represents dietary importance by SIAR proportion estimates (mode).</p

Joint effects of patch edges and habitat degradation on faunal predation risk in a widespread marine foundation species

Human activities degrade and fragment coastal marine habitats, reducing their structural complexity and making habitat edges a prevalent seascape feature. Though habitat edges frequently are implicated in reduced faunal survival and biodiversity, results of experiments on edge effects have been inconsistent, calling for a mechanistic approach to the study of edges that explicitly includes indirect and interactive effects of habitat alteration at multiple scales across biogeographic gradients. We used an experimental network spanning 17 eelgrass (Zostera marina) sites across the Atlantic and Pacific oceans and the Mediterranean Sea to determine (1) if eelgrass edges consistently increase faunal predation risk, (2) whether edge effects on predation risk are altered by habitat degradation (shoot thinning), and (3) whether variation in the strength of edge effects among sites can be explained by biogeographical variability in covarying eelgrass habitat features. Contrary to expectations, at most sites, predation risk for tethered crustaceans (crabs or shrimps) was lower along patch edges than in patch interiors, regardless of the extent of habitat degradation. However, the extent to which edges reduced predation risk, compared to the patch interior, was correlated with the extent to which edges supported higher eelgrass structural complexity and prey biomass compared to patch interiors. This suggests an indirect component to edge effects in which the impact of edge proximity on predation risk is mediated by the effect of edges on other key biotic factors. Our results suggest that studies on edge effects should consider structural characteristics of patch edges, which may vary geographically, and multiple ways that humans degrade habitats.This research was funded by National Science Foundation grants to JED, JJS, and KAH (NSF-OCE 1336206, OCE 1336905, and OCE 1336741). CB was funded by the Åbo Akademi University Foundation