Ross Whippo

Human‐caused global change produces biotic and abiotic conditions that increase the uncertainty and risk of failure of restoration efforts. A focus of managing for resiliency, that is, the ability of the system to respond to disturbance, has the potential to reduce this uncertainty and risk. However, identifying what drives resiliency might depend on how one measures it. An example of a system where identifying how the drivers of different aspects of resiliency can inform restoration under climate change is the northern coast of California, where kelp experienced a decline in coverage of over 95% due to the combination of an intense marine heat wave and the functional extinction of the primary predator of the kelp‐grazing purple sea urchin, the sunflower sea star. Although restoration efforts focused on urchin removal and kelp reintroduction in this system are ongoing, the question of how to increase the resiliency of this system to future marine heat waves remains open. In this paper, we introduce a dynamical model that describes a tritrophic food chain of kelp, purple urchins, and a purple urchin predator such as the sunflower sea star. We run a global sensitivity analysis of three different resiliency metrics (recovery likelihood, recovery rate, and resistance to disturbance) of the kelp forest to identify their ecological drivers. We find that each metric depends the most on a unique set of drivers: Recovery likelihood depends the most on live and drift kelp production, recovery rate depends the most on urchin production and feedbacks that determine urchin grazing on live kelp, and resistance depends the most on feedbacks that determine predator consumption of urchins. Therefore, an understanding of the potential role of predator reintroduction or recovery in kelp systems relies on a comprehensive approach to measuring resiliency.

Ecosystem function is maintained in part by direct species interactions, but indirect interactions and non‐consumptive effects may be of equal ecological importance. Along the west coast of North America, the recent population collapse of the predatory sunflower sea star Pycnopodia helianthoides has been implicated in the proliferation of the purple sea urchin Strongylocentrotus purpuratus, and a concurrent decline in kelp canopy cover in several locales. Recent work began to quantify the predation rates effects (i.e., direct consumptive effects) of Pycnopodia on sea urchins that may lead to density‐mediated indirect effects on kelp. However, the importance of non‐consumptive effects on urchin behavior and the possible trait‐mediated indirect effects of Pycnopodia on kelp are not well understood. This leaves a critical gap in our knowledge about how these predators may be controlling grazer populations and, indirectly, primary production by macroalgae in nearshore habitats. We measured the non‐consumptive behavioral effects of Pycnopodia on S. purpuratus in the laboratory including grazing rates, feeding behavior, and movement of starved versus fed urchins, the latter simulating urchin metabolic conditions within urchin barrens. We found that the presence of a waterborne Pycnopodia cue reduced the grazing rate of fed urchins by 50% over short (~24 h) time scales. In contrast, starved urchins consumed kelp and did not exhibit an escape response in the presence of a Pycnopodia cue. This study highlights a trait‐mediated indirect interaction between Pycnopodia, S. purpuratus, and kelp, showing how the urchin response to a predator cue may differ based on urchin metabolic conditions or ecosystem state, and helps clarify the positive role of Pycnopodia on kelp forest health.

The Western Antarctic Peninsula supports a diverse assemblage of > 100 described macroalgal species that contribute to the base of coastal food webs, but their contribution to local nearshore food webs is still uncertain across larger spatial scales. The analysis of biomarkers, specifically fatty acids and stable isotopes, offers a tool to clarify the trophic role of Antarctic macroalgae. The aim of this study was to describe the fatty acid profiles and stable isotope values of 31 algal species from three divisions (Chlorophyta—1, Ochrophyta—8, Rhodophyta—22) collected at the same sites for both biomarkers. Of these, 13 species had no previously published fatty acid profiles. Most species were rich in polyunsaturated fatty acids (PUFAs), suggesting they are highly nutritious and could be a resource of essential fatty acids for consumers. This was specifically noticeable in the overall low PUFA ratio (∑ω6/∑ω3 ratio), with low ratios being an indicator of high nutritional quality for consumers. Fatty acid profiles of macroalgae grouped strongly by phylogeny (at the levels of division, order, and family), while stable isotope groupings were more driven by the physiological properties of the species. Specifically, some closely related red algal species exhibited very different stable isotope values based on their carbon concentrating mechanisms, with highly ¹³C-depleted values in several Rhodophyta species. The fact that the two biomarker approaches created different groupings of Antarctic macroalgae collected at the same locations emphasizes that their combined application can be a powerful tool in Antarctic coastal food web studies.

The recent collapse of predatory sunflower sea stars ( Pycnopodia helianthoides ) owing to sea star wasting disease (SSWD) is hypothesized to have contributed to proliferation of sea urchin barrens and losses of kelp forests on the North American west coast. We used experiments and a model to test whether restored Pycnopodia populations may help recover kelp forests through their consumption of nutritionally poor purple sea urchins ( Strongylocentrotus purpuratus ) typical of barrens. Pycnopodia consumed 0.68 S. purpuratus d ⁻¹ , and our model and sensitivity analysis shows that the magnitude of recent Pycnopodia declines is consistent with urchin proliferation after modest sea urchin recruitment, and even small Pycnopodia recoveries could generally lead to lower densities of sea urchins that are consistent with kelp-urchin coexistence. Pycnopodia seem unable to chemically distinguish starved from fed urchins and indeed have higher predation rates on starved urchins owing to shorter handling times. These results highlight the importance of Pycnopodia in regulating purple sea urchin populations and maintaining healthy kelp forests through top-down control. The recovery of this important predator to densities commonly found prior to SSWD, whether through natural means or human-assisted reintroductions, may therefore be a key step in kelp forest restoration at ecologically significant scales.

Aim: Conservation efforts have traditionally addressed the threat of biodiversity loss by prioritizing regions and habitats with high endemic species richness. However, species‐poor habitats often harbour distinct, valuable and/or functionally unique species that contribute to regional diversity. In the tropical marine realm, the ‘mangrove‐seagrass‐coral reef continuum’ has dominated both the scientific literature and marine spatial planning. Bare sediment habitats are also part of this continuum and often comprise the majority of bottom area, as they do in most regions worldwide, but are understudied and rarely considered in conservation. To address this information gap, we partition the relative contributions of five habitats in the coastal mosaic (forereefs, patch reefs, seagrass, mangroves and bare sand) to fish diversity across a tropical seascape.Location: Carrie Bow Cay, Belize Barrier Reef.Methods: Using diver visual censuses, we assessed fish community composition at three replicate sites from each of the five habitats annually for 5 years. We then partitioned diversity into within (α) and between (β) habitat contributions, and further partitioned β‐diversity into components attributed to species replacement and richness difference. Finally, we determined the local contributions to β‐diversity (LCBD) by each habitat and identified the key individual species behind these contributions.Main Results: Tropical sand flats contributed uniquely and disproportionately to regional fish species diversity, despite having the fewest species overall. Sand flats also had higher‐than‐expected local contributions to β‐diversity (LCBD) and had the highest percentage of species not found in other habitats.Main Conclusions: Our results demonstrate that previously understudied sand habitats harbour a relatively unique assemblage of species compared with other nearby habitats. Marine spatial planning aimed at maximizing the preservation of total biodiversity (including unique species) in the tropics should consider sand habitats.

To better understand the decline of one of earth’s most biodiverse habitats, coral reefs, many survey programs employ regular photographs of the benthos. An emerging challenge is the time required to annotate the large volume of digital imagery generated by these surveys. Here, we leverage existing machine-learning tools (CoralNet) and develop new fit-to-purpose programs to process and score benthic photoquadrats using five years of data from the Smithsonian MarineGEO Network’s biodiversity monitoring program at Carrie Bow Cay, Belize. Our analysis shows that scleractinian coral cover on forereef sites (at depths of 3–10 m) along our surveyed transects increased significantly from 6 to 13% during this period. More modest changes in macroalgae, turf algae, and sponge cover were also observed. Community-wide analysis confirmed a significant shift in benthic structure, and follow-up in situ surveys of coral demographics in 2019 revealed that the emerging coral communities are dominated by fast-recruiting and growing coral species belonging to the generaAgariciaandPorites. While the positive trajectory reported here is promising, Belizean reefs face persistent challenges related to overfishing and climate change. Open-source computational toolkits offer promise for increasing the efficiency of reef monitoring, and therefore our ability to assess the future of coral reefs in the face of rapid environmental change.

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.

Coastal seascapes can support high animal diversity and secondary productivity that attracts conservation interest and provides ecosystem services. Though the importance of spatial structure in marine habitats is well known, determining the dominant spatial scale for biodiversity patterns is an often‐overlooked dimension of the ecological and conservation value of seagrass meadows. We estimated biodiversity patterns at fine (0.28 m ² ), meadow and seascape scales to explore whether seagrass‐associated biodiversity patterns are consistent with spatial processes such as abiotic habitat filtering or metacommunity dynamics in a northeast Pacific seascape. In Barkley Sound, British Columbia, we quantified epifaunal biodiversity on eelgrass ( Zostera marina ) to test three hypotheses: Taxonomic diversity and composition (1) vary randomly within meadows but (2) vary systematically among meadows reflecting meadow location or environmental conditions, and (3) spatial patterns are stable over time. We sampled epifaunal invertebrates in a systematic spatial grid within nine eelgrass meadows. We found that epifaunal community composition varied as much over a few meters within the same meadow as among meadows separated by kilometers and of different sizes and wave exposures. In each meadow, we observed less than three‐quarters of the species in the regional species pool, and we observed non‐random spatial aggregation within many species. Even with spatial turnover, assemblages were more similar than predicted by null models based on random species distributions, suggesting that some species tend to co‐occur in high abundance. These spatial biodiversity patterns were not clearly explained by meadow location, area, or abiotic conditions, except that there were differences in clusters of meadows distinguished by their salinity (more marine vs. more fresh). Our results indicate that effective conservation and understanding of how seagrass can support high biodiversity and ecosystem function may require consideration of spatial connections among meadows, and not just the condition of the meadows themselves.

Sea urchins are important ecosystem engineers in subtidal ecosystems worldwide, providing biogenic structure and altering nutrient dynamics through intensive grazing and drift algal capture. The current work evaluates red urchin (Strongylocentrotus franciscanus) density on fixed transects through time, individual displacement, and urchin‐associated benthic community composition using a field‐based approach at multiple depths (in and outside of the macroalgal zone) and replicated across sites in the San Juan Archipelago, Washington. Urchins exhibited no large‐scale, temporal or directional changes in density among depths. Furthermore, 87% of individual urchins observed in repeated small‐scale surveys over 3 weeks exhibited no change in position. Individual displacement was negatively correlated to drift algal capture. Evidence of sedentary behavior from the displacement surveys was supported by the sessile and mobile community composition in areas directly under versus adjacent to (control) urchins. The benthos under urchins had a higher percentage of bare space, crustose coralline algae, and increased density of snails, crabs and shrimp relative to associated control plots. Abundance of mobile organisms associating with urchins increased relative to control plots at the deepest survey depth (30 m), indicating a greater strength of interaction with distance from macroalgal production. This work presents evidence of food availability‐related behavior in red urchins and indicates that even when sedentary, urchins have a strong influence on ecosystem structure through increasing availability of shelter and macroalgal detritus to the benthos.