Bolstered physical defences under nutrient-enriched conditions may facilitate a secondary foundational algal species in the South Pacific

Humans have a long history of changing species\u27 ranges and habitat distributions, making studies of the ecological processes that may facilitate these changes of key importance, particularly in cases where a primary foundation species is replaced by another, less desirable species. We investigated the impact of nutrients and herbivory on Turbinaria ornata, a secondary foundational macroalga that depends on and likely competes with coral, the primary foundational community. T. ornata is also rapidly expanding in range and habitat across the South Pacific. We conducted (i) a mesocosm experiment assessing relative nutrient limitation, (ii) a field experiment comparing importance of nutrients (+/-) and herbivory (+/-) to biomass accumulation, and (iii) an herbivory assay and toughness test comparing enriched and ambient thalli to assess changes to anti-herbivory defences. We found no evidence of growth being nutrient limited in T. ornata; rather than stimulating growth, nutrient addition deterred herbivores. However, when physical toughness was removed, enriched algae were preferred, with consumption rates 25-fold those of unenriched algae. Additionally, enriched thalli were tougher than ambient thalli, suggesting physical defences were bolstered by nutrient enrichment. Synthesis. We found a unique interaction where nutrients inhibit herbivory and facilitate Turbinaria ornata biomass accumulation. While concern is often placed on degradation of foundation species via anthropogenic change, instead here we show that anthropogenic change can facilitate secondary foundation species. This facilitation may allow a secondary foundation species to better compete with primary foundation species. We found a unique interaction where nutrients inhibit herbivory and facilitate Turbinaria ornata biomass accumulation. While concern is often placed on degradation of foundation species via anthropogenic change, instead here we show that anthropogenic change can facilitate a secondary foundation species. This facilitation may allow a secondary foundation species to better compete with the primary foundation species

Informing Canada’s commitment to biodiversity conservation: A science-based framework to help guide protected areas designation through Target 1 and beyond

Biodiversity is intrinsically linked to the health of our planet—and its people. Yet, increasingly, human activities are causing the extinction of species, degrading ecosystems, and reducing nature’s resilience to climate change and other threats. As a signatory to the Convention on Biological Diversity, Canada has a legal responsibility to protect 17% of land and freshwater by 2020. Currently, Canada has protected ∼10% of its terrestrial lands, requiring a marked increase in the pace and focus of protection over the next three years. Given the distribution, extent, and geography of Canada’s current protected areas, systematic conservation planning would provide decision-makers with a ranking of the potential for new protected area sites to stem biodiversity loss and preserve functioning ecosystems. Here, we identify five key principles for identifying lands that are likely to make the greatest contribution to reversing biodiversity declines and ensuring biodiversity persistence into the future. We identify current gaps and integrate principles of protecting (i) species at risk, (ii) representative ecosystems, (iii) intact wilderness, (iv) connectivity, and (v) climate refugia. This spatially explicit assessment is intended as an ecological foundation that, when integrated with social, economic and governance considerations, would support evidence-based protected area decision-making in Canada

Effects of sediment depth on algal turf height are mediated by interactions with fish herbivory on a fringing reef

Closely cropped algal turfs support key ecosystem functions on healthy coraldominated reefs, yet how this important reef component is affected by sedimentation, a key stressor on reefs worldwide, is relatively unknown. We used a 2-factor caging experiment to evaluate the effects of varying sediment depth and presence of herbivorous fish on algal turf height on a fringing reef in Mo\u27orea, French Polynesia. Without herbivory, 2 mm of sediment reduced turf growth by ∼50% compared to sediment removal treatments; in contrast, growth with 4 mm of sediment was low or negligible regardless of herbivory treatment. Negative effects of sediment were linked to the development of black basal layers of sediment, indicating accumulation of hydrogen sulfide. Black sediment occurred in 60 to 70% of all 4 mm plots and in 43% of caged 2 mm plots but was not found in open 2 mm plots, implying that grazing ameliorated development of black sediment under 2 mm loads. Sediment levels of 2 mm did not deter herbivory, evidenced by the significant decrease in turf height in open compared to caged plots. Under 4 mm of sediment, black sediment inhibited both growth and herbivory where it occurred. Without black sediment, however, fish grazing balanced algal growth, resulting in negligible algal height changes across 4 mm plots but with differing underlying mechanisms. Field surveys on other sedimented reefs with healthy herbivore communities confirmed an increase in the presence of black sediment at depths over 3 mm. Thus, deeper sediment depths inhibit turf growth, yet under moderate levels of sedimentation, intact herbivorous fish communities may maintain closely cropped, healthy turf communities by preventing the negative effects of black sediment

A rapidly expanding alga acts as a secondary foundational species providing novel ecosystem functions in the South Pacific

Foundation species facilitate associated communities and provide key ecosystem functions, making anthropogenically driven phase-shifts involving these species critically important. One well documented such phase-shift has been from coral to algal domination on tropical reefs. On South Pacific coral reefs, the macroalga Turbinaria ornata has expanded its range and habitat but, unlike algae that often dominate after phase-shifts, T. ornata is structurally complex and generally unpalatable to herbivores. Therefore, it may serve a foundational role on coral reefs, such as providing habitat structure to more palatable primary producers and corresponding trophic support to fishes. We predicted increasing T. ornata density would facilitate growth of associated algae, resulting in a positive trophic cascade to herbivorous fish. An experiment manipulating T. ornata densities showed a uni- modal relationship between T. ornata and growth of understory algae, with optimal growth occurring at the most frequent natural density. Epiphyte cover also increased with density until the same optimum, but remained high with greater T. ornata densities. Foraging by herbivorous fishes increased linearly with T. ornata density. An herbivore exclusion experiment confirmed T. ornata facilitated epiphytes, but resource use of epiphytes by herbivores, though significant, was not affected by T. ornata density. Therefore, T. ornata performs foundational roles because it provides novel habitat to understory and epiphytic macroalgae and trophic support to consumers, though likely this function is at the expense of the original foundational corals

A tale of two algal blooms: negative effects of two dominant genera on seagrass and its epiphytes

Recent evidence suggests macroalgal blooms may play a role in the worldwide decline in seagrass, but the shape of the functional relationship between seagrass health and dominant bloom-forming macroalgae is poorly characterized. We tested whether the impact of varying abundances of two cosmopolitan bloom-forming macroalgal genera caused linear/quasi-linear or sudden threshold changes in measures of eelgrass, Zostera marina, meadow health. We conducted two caging experiments in a shallow Z. marina bed (∼1 m depth) in Bodega Harbor, California, USA where we maintained six densities within the range of natural abundances of macroalgae, Ulva (0-4.0 kg m-2) and Gracilariopsis (0-2.0 kg m-2), as well as uncaged controls over a 10-week period. Shoot density, blade growth, and epiphyte load were measured every two weeks and algal treatments reset. We did not find support for threshold transitions between algal abundance and measures of seagrass bed health using sigmoidal and broken-stick regression analyses for each data set; these models are commonly used to identify threshold patterns in ecological shifts. Instead, final measurements of shoot density and epiphyte load were best modelled as linear or slightly non-linear declines with increasing Ulva abundance. A negative linear relationship also existed between shoot density and Gracilariopsis abundance and a trend towards linear negative effects on epiphyte load. The similar shape of these functional relationships across different types of algae suggests the relationship may be generalizable. At algal abundances that are commonly observed, we found smooth and predictable negative impacts to Z. marina by decline in shoot density and potential impacts to food webs by loss of epiphytes rather than sudden threshold shifts or ecological surprises . Our work contrasts with the growing body of literature suggesting highly non-linear shifts in response to human impact; thus, it is important to broaden understanding of shifts to more than just pattern but to the processes that drive different patterns of shifts

Nutrients induce and herbivores maintain thallus toughness, a structural antiherbivory defense in Turbinaria ornata

The loss of coral cover, frequently driven by anthropogenic disturbances, can result in a phase shift to dominance by fleshy macroalgae, many of which contain anti-herbivore defenses. Using field surveys, a mesocosm experiment, and field experiments, we evaluate whether 2 human impacts-nutrient enrichment and reduction in herbivory-affected production and maintenance of thallus toughness, a physical defense of the brown macroalgae Turbinari ornata that has recently expanded across the South Pacific. In contrast to our expectations, there was a weak negative relationship between herbivorous fish abundance and thallus toughness This relationship was driven by greater toughness in algae collected at the more eutrophic sites which also had lower herbivore abundances. A mesocosm experiment confirmed a positive relationship between nutrients and thallus toughness with no measurable cost to growth. Mechanica damage simulating herbivory maintained thallus toughness in cages, with a significant trade-of in growth. In addition, reduction of herbivory through caging in a transplant experiment resulted in a reduction in thallus toughness; however there was no measurable benefit to growth, possible due to a concurrent change in environmental context from the transplant. While reduction i herbivory via overfishing allows this alga to trade energy normally spent on defense for increase growth, nutrient enrichment provides T. ornata with additional resources to increase defenses. A anthropogenic impacts become increasingly prominent in coral reef systems, it is critical that w understand the processes that may facilitate the expansion and dominance of coral reef algae especially those with inducible anti-herbivore defenses

Simultaneous synergist, antagonistic, and additive interactions between multiple local stressors all degrade algal turf communities on coral reefs

1. Ecological communities are subjected to multiple anthropogenic stressors at both global and local scales that are increasing in number and magnitude. Stressors can interact in complex ways and are classified as additive, synergistic or antagonistic; the nature of the interaction is key to predicting changes and understanding community resilience. Coral reefs are among the most impacted communities and have shifted from coral to algal-dominated states, and overfishing, nutrient enrichment and sedimentation are local stressors that often cooccur and may support degraded algal states. Short algal turfs are abundant benthic space holders on healthy reefs that may be pushed by local stressors to long algal turfs, a more degraded state that may prevent recovery to coral dominance. 2. We conducted a fully crossed three-factor field experimenton short algalturf communities manipulating herbivory pressure (+/−cages), nutrients (+/−fertilizer) and sediments (natural accumulation/removal). We applied stressors for 16 days, removed them and monitored turf height during and after manipulations. 3. We found that significant pair-wise interactions between all stressors pushed the community towards a degraded state with longer algal turfs. All three types of interactions (additive, synergistic and antagonistic) were common and occurred in equal frequency, suggesting more investigations into all types are needed to accurately predict community responses to multiple stressors. For example, when herbivores were present, nutrients and sediments interacted additively, while in the absence of herbivores, nutrients and sediments interacted synergistically. All inter-actions broke down following termination of experimental manipulations and all effects were undetectable after 49 days, indicating that this reef may be resilient, at least when stressors are applied on a short time-scale. 4. Synthesis. Because management of local stressors is often more tractable than global stressors, local management has been proposed as a means to offset global stressors. However, ecological communities often experience multiple local stressors simultaneously, and interactions between stressors, including synergisms and antagonisms, may be the source of nonlinear shifts in communities or “ecological surprises.” The majority of interactions in our study were both strong and nonlinear, and we suggest that, if pervasive across systems, nonlinear interactions may drive the recent global increase in “ecological surprises.

From coast to coast to coast: Ecology and management of eelgrass systems across Canada

Seagrass meadows are among the most productive and diverse marine ecosystems, providing essential structure, functions, and services. They are also among the most impacted by human activities and in urgent need of better management and protection. In Canada, eelgrass (Zostera marina) meadows are found along the Atlantic, Pacific, and Arctic coasts, and thus occur across a wide range of biogeographic conditions. Here, we synthesize knowledge of eelgrass ecosystems across Canada’s coasts, highlighting commonalities and differences in environmental conditions, plant, habitat, and community structure, as well as current trends and human impacts. Across regions, eelgrass life history, phenology, and general species assemblages are similar. However, distinct regional differences occur in environmental conditions, particularly with water temperature and nutrient availability. There is considerable variation in the types and strengths of human activities among regions. The impacts of coastal development are prevalent in all regions, while other impacts are of concern for specific regions, e.g., nutrient loading in the Atlantic and impacts from the logging industry in the Pacific. In addition, climate change represents a growing threat to eelgrass meadows. We review current management and conservation efforts and discuss the implications of observed differences from coast to coast to coast

Patterns of uncertainty in life-history and extinction risk for Arctic vertebrates

Conserving Arctic wildlife will be challenging given the ongoing environmental changes in the region. In addition, there is a lack of fundamental biological information for many Arctic species, including a dearth of knowledge surrounding conservation threats and the risk of extinction. In this study, we gather all available data on research effort and life-history traits to assess the current state of scientific knowledge surrounding 389 Arctic vertebrate species. We also quantify patterns of species evaluation by the IUCN Red List, a global database of conservation risk used to measure success and prioritize resources in many conservation programs. We find that 10% of Arctic vertebrates have been the subject of no peer-reviewed studies during the last 30 years, and that we have little life history knowledge for many species. Arctic marine fishes are especially poorly known with an average of 3.5 (out of six) key life-history traits unknown. In a multivariate analysis, whether an Arctic species had been evaluated by the IUCN Red List was most strongly predicted by research effort and varied among taxonomic groups. In addition, we found that species that have been evaluated by the IUCN Red List continue to receive more research attention than species which have not been evaluated. Protecting all Arctic species may, therefore, require research programs and methods to halt research inertia and shift more attention onto species that are poorly known

Inaccurate and Biased Global Media Coverage Underlies Public Misunderstanding of Shark Conservation Threats and Solutions

Sharks are a taxon of significant conservation concern and associated public interest. The scientific community largely supports management policies focusing on sustainable fisheries exploitation of sharks, but many concerned members of the public and some environmental advocates believe that sustainable shark fisheries cannot and do not exist and therefore support total bans on all shark fisheries and/or trade in shark products. The belief that sustainable shark fisheries cannot and do not exist persists despite scientific evidence showing that they can and do, and are important to livelihoods. Additionally, many concerned members of the public are only aware of one threat to sharks and are unaware of other threats—or of most available policy solutions. Here we assess whether the popular press plays a role in spreading misinformation and misunderstanding about these issues via the agenda-setting, priming, and cultivation roles of the media, with the goal of better understanding the causes and consequences of public confusion