• Energy Research

AbstractNutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous experiments. But because experiments rarely incorporate natural variation in environmental factors and biodiversity, conditions determining the relative strength of bottom–up and top–down forcing remain unresolved. We factorially added nutrients and reduced grazing at 15 sites across the range of the marine foundation species eelgrass (Zostera marina) to quantify how top–down and bottom–up control interact with natural gradients in biodiversity and environmental forcing. Experiments confirmed modest top–down control of algae, whereas fertilisation had no general effect. Unexpectedly, grazer and algal biomass were better predicted by cross‐site variation in grazer and eelgrass diversity than by global environmental gradients. Moreover, these large‐scale patterns corresponded strikingly with prior small‐scale experiments. Our results link global and local evidence that biodiversity and top–down control strongly influence functioning of threatened seagrass ecosystems, and suggest that biodiversity is comparably important to global change stressors.

The influence of topographic heterogeneity (boulders of different sizes: 0.75, 1.5, 2.25 m) on intertidal soft-bottom community characteristics [diversity(H') richness, and biomass] was examined in the St. Lawrence Estuary, Canada. The macrofauna, sediment characteristics, and flow regime in the zones surrounding boulders were examined in 6 orientations (directions) and at 3 distances from boulders. Flow around boulders and control sites (no boulders) was estimated by the rate of plaster dissolution of standard plaster cylinders. Control sites (no boulders) showed the highest species diversity (H'a: based on density) and richness. These parameters decreased significantly with boulder size and increased significantly with distance from boulders. For both small and large boulder sizes, highest and lowest diversities were generally observed in opposite orientations. Overall, biomass was not influenced by boulder size. Plaster dissolution explained more variability in diversity, richness and biomass (up to 35, 30 and 25%, respectively) than did sediment characteristics (8, 6 and 27%, respectively). Species dominance was strong and probably explained the relative constancy of diversity among treatments.

We evaluated single and interactive effects of density reduction of Zostera marina L., a habitat-forming species, shading, and sediment nutrient enrichment on the response of Z. marina and its associated epifauna over a 10-week experiment during the summer of 2015. Before the experiment was started (Period T0), above-ground eelgrass shoot biomass was evaluated using the shoots collected from 10 cells of 10 x 10 cm while applying the Z. marina density reduction.

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.

Significance Consumption transfers energy and materials through food chains and fundamentally influences ecosystem productivity. Therefore, mapping the distribution of consumer feeding intensity is key to understanding how environmental changes influence biodiversity, with consequent effects on trophic transfer and top–down impacts through food webs. Our global comparison of standardized bait consumption in shallow coastal habitats finds a peak in feeding intensity away from the equator that is better explained by the presence of particular consumer families than by latitude or temperature. This study complements recent demonstrations that changes in biodiversity can have similar or larger impacts on ecological processes than those of climate.

AbstractBenthic fauna refers to all fauna that live in or on the seafloor, which researchers typically divide into size classes meiobenthos (32/64 µm–0.5/1 mm), macrobenthos (250 µm–1 cm), and megabenthos (>1 cm). Benthic fauna play important roles in bioturbation activity, mineralization of organic matter, and in marine food webs. Evaluating their role in these ecosystem functions requires knowledge of their global distribution and biomass. We therefore established the BenBioDen database, the largest open-access database for marine benthic biomass and density data compiled so far. In total, it includes 11,792 georeferenced benthic biomass and 51,559 benthic density records from 384 and 600 studies, respectively. We selected all references following the procedure for systematic reviews and meta-analyses, and report biomass records as grams of wet mass, dry mass, or ash-free dry mass, or carbon per m2 and as abundance records as individuals per m2. This database provides a point of reference for future studies on the distribution and biomass of benthic fauna.