Biology subjects

Spindel, N. B.

Publications and source records attributed to Spindel, N. B..

3 recordsLinked to original sources

bioRxiv2025

Consumer resilience suppresses the recovery of overgrazed ecosystems

O_LIMany heterotroph species perish when faced with severe food limitation, others can persist, adapt, and thrive. Sea urchins are emblematic of this paradox: they can overgraze kelp forests to form barren habitats, but can then survive for decades in these nutritionally depauperate seascapes. Understanding the mechanisms enabling persistence under starvation, and rapid recovery when food returns, provides insight into how consumer resilience shapes ecosystem dynamics. C_LIO_LIWe quantified how food abundance, quality, deprivation, and reintroduction influence bioenergetic performance in the red sea urchin (Mesocentrotus franciscanus), integrating field observations of kelp forest and barren populations with a controlled feeding experiment. We measured respiration, feeding rates, gonadal growth, and fatty acid biomarkers to test how habitat history and diet jointly govern metabolic plasticity and nutrient assimilation. C_LIO_LIResting metabolic rates (RMR) were nearly twofold higher in kelp forest urchins than barrens conspecifics, yet feeding rates were equivalent across habitats, indicating that metabolic depression does not constrain food intake. Reciprocal shifts emerged in the experiment: starvation reduced RMR and lipid reserves in kelp forest urchins, while feeding elevated both traits in barrens urchins to levels comparable with kelp forest conspecifics. These results demonstrate rapid physiological compensation in response to both food deprivation and reintroduction. C_LIO_LIDiet quality strongly modulated performance. Urchins fed nutritionally poor monospecific diets consumed more biomass and calories than those on diverse, polyunsaturated fatty acid (PUFA)-rich diets, but did so with markedly lower efficiency of conversion to gonadal tissue. Fatty acid assimilation revealed that starvation elevated bacterial and biofilm biomarkers in tissues, whereas algal diets enriched essential PUFA profiles, particularly when diets were diverse. These results highlight that both quantity and quality of food influence consumer recovery trajectories, with nutritional geometry shaping efficiency of energy and nutrient use. C_LIO_LITogether, our findings show that M. franciscanus exhibits pronounced metabolic resilience, allowing persistence in barren habitats and rapid reactivation of grazing and reproduction when food becomes available. This work links nutritional ecology to ecosystem feedbacks by showing how compensatory feeding and metabolic flexibility enable consumers to maintain pressure on primary producers, thereby influencing the stability, hysteresis, and recovery of degraded ecosystems. C_LI

ecology↗

bioRxiv2024

Biomarkers of recovery: characterizing trophic flow following ecological restoration

Coastal kelp forests are important sources of primary productivity and provide essential habitat and ecosystem services. In many areas around the world, the formation and persistence of urchin barrens threatens kelp forest ecosystems. Over the past several decades, restoration efforts have emerged aiming to increase the abundance of foundation species like kelp in such systems. However, we lack a comprehensive understanding of how successful kelp restoration affects the nutritional landscape and the fitness of kelp forest herbivores. We bridge this knowledge gap with a Before-After-Control-Impact Paired Series (BACIPS) focused on kelp forest restoration where reductions of herbivorous sea urchins in Haida Gwaii resulted in substantial increases in kelp abundance in habitat previously characterized as barrens. Specifically, we document body size specific shifts in the fatty acid (FA) profiles of red sea urchins (Mesocentrotus franciscanus) and northern abalone (Haliotis kamtschatkana). FAs associated with bacteria and diatoms were elevated in tissues of urchins and abalone in barrens habitat while kelp biomarkers were elevated in restored kelp forest habitat. For urchins, these shifts tracked the increase in gonad mass following kelp forest recovery. For abalone, these results varied depending on animal body size. Specifically, abalone exhibited a continuous size-specific shift from biofilm-associated markers at small sizes to kelp-associated markers as animals increased in size. For both species, a marked increase in essential fatty acids was observed following kelp restoration. Our results demonstrate kelp restoration via sea urchin reduction enhances not only the quantity but also the quality and diversity of food in previously degraded habitats, and subsequently enhances the amount and nutritional quality of roe (i.e., gonads) in sea urchins therein.

ecology↗

bioRxiv2020

Zombies of the nearshore: Metabolic depression in sea urchin barrens associated with food deprivation

The proliferation of sea urchins can decimate macroalgal forests in coastal ecosystems, leading to persistent barren seascapes. While kelp forests are among the most productive ecosystems on the planet, productivity in these urchin barrens is dramatically reduced. Moreover, urchins inhabiting these food-depauperate barrens face starvation and many survive in these barrens for years or decades. Urchins in barrens can persist by eating food subsidies from drift algae, pelagic salps, tubeworms, as well as encrusting and filamentous algae, microbial mats, and slow-growing species resistant to herbivory. Despite both food from endogenous production and exogenous subsidies, many urchins in barrens likely experience prolonged food deprivation. This resource limitation may create a trade-off between reproduction and survival; for example, fecundity of purple sea urchins (Strongylocentrotus purpuratus) is 99.9% lower in barrens. Despite food constraints, red sea urchins (Mesocentrotus franciscanus), the dominant urchin species at our study sites, can live in excess of 100 years and barrens in Haida Gwaii, British Columbia (BC), Canada, have persisted for at least 143 years. While these phenomena are widespread and well documented, the bioenergetic adaptations that allow urchins to persist in these food-depauperate barrens remain poorly understood. To quantify habitat-specific differences in metabolic rates and energy reserves (as measured by gonadal mass), we conducted respirometry on and measured gonadal mass in M. franciscanus at three locations in BC inside and outside of adjacent kelp forest and barrens habitat. Here we demonstrate that M. franciscanus in barrens versus kelp forests have substantially lower energy reserves and, importantly, also exhibit dramatic reductions in size-specific resting metabolic rates (RMR), even after standardizing by metabolically active body mass. On average, gonadal mass was 44.6% lower and RMR scaled to metabolically active body mass was 40% lower in barrens urchins than in kelp forest urchins. Such a shift in metabolic rate may provide a mechanism that facilitates barren state stability over long time scales as M. franciscanus can lower energetic demands while they wait for small pulses of food, scrape by on low-productivity resources, and suppress recruitment of macroalgae for months, years, or decades.

ecology↗