scholarly journals Energetic context determines the effects of multiple upwelling-associated stressors on sea urchin performance

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kindall A. Murie ◽  
Paul E. Bourdeau
Keyword(s):  
Coastal Upwelling ◽  
Multiple Stressors ◽  
Sea Urchins ◽  
Strongylocentrotus Purpuratus ◽  
Kelp Forest ◽  
Low Ph ◽  
Kelp Forests ◽  
Distant Future ◽  
Urchin Barren ◽  
Insight Into

AbstractGlobally, kelp forests are threatened by multiple stressors, including increasing grazing by sea urchins. With coastal upwelling predicted to increase in intensity and duration in the future, understanding whether kelp forest and urchin barren urchins are differentially affected by upwelling-related stressors will give insight into how future conditions may affect the transition between kelp forests and barrens. We assessed how current and future-predicted changes in the duration and magnitude of upwelling-associated stressors (low pH, dissolved oxygen, and temperature) affected the performance of purple sea urchins (Strongylocentrotus purpuratus) sourced from rapidly-declining bull kelp (Nereocystis leutkeana) forests and nearby barrens and maintained on habitat-specific diets. Kelp forest urchins were of superior condition to barrens urchins, with ~ 6–9 times more gonad per body mass. Grazing and condition in kelp forest urchins were more negatively affected by distant-future and extreme upwelling conditions, whereas grazing and survival in urchins from barrens were sensitive to both current-day and all future-predicted upwelling, and to increases in acidity, hypoxia, and temperature regardless of upwelling. We conclude that urchin barren urchins are more susceptible to increases in the magnitude and duration of upwelling-related stressors than kelp forest urchins. These findings have important implications for urchin population dynamics and their interaction with kelp.

scholarly journals Sea urchins mediate the availability of kelp detritus to benthic consumers

2019 ◽  
Vol 286 (1906) ◽  
pp. 20190846 ◽  
Author(s):  
Christie E. Yorke ◽  
Henry M. Page ◽  
Robert J. Miller
Keyword(s):  
Food Webs ◽  
Sea Urchins ◽  
Strongylocentrotus Purpuratus ◽  
Kelp Forest ◽  
Macrocystis Pyrifera ◽  
Mesocosm Experiment ◽  
Kelp Forests ◽  
Giant Kelp ◽  
Trophic Role ◽  
Benthic Consumers

Detritus can fundamentally shape and sustain food webs, and shredders can facilitate its availability. Most of the biomass of the highly productive giant kelp, Macrocystis pyrifera , becomes detritus that is exported or falls to the seafloor as litter. We hypothesized that sea urchins process kelp litter through shredding, sloppy feeding and egestion, making kelp litter more available to benthic consumers. To test this, we conducted a mesocosm experiment in which an array of kelp forest benthic consumers were exposed to 13 C- and 15 N-labelled Macrocystis with or without the presence of sea urchins, Strongylocentrotus purpuratus . Our results showed that several detritivore species consumed significant amounts of kelp, but only when urchins were present. Although they are typically portrayed as antagonistic grazers in kelp forests, sea urchins can have a positive trophic role, capturing kelp litter before it is exported and making it available to a suite of benthic detritivores.

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

2020 ◽  
Author(s):  
Nathan B. Spindel ◽  
Lynn C. Lee ◽  
Daniel K. Okamoto
Keyword(s):  
Body Mass ◽  
Food Deprivation ◽  
Microbial Mats ◽  
Sea Urchins ◽  
Kelp Forest ◽  
Resource Limitation ◽  
Kelp Forests ◽  
Metabolic Rates ◽  
Energy Reserves ◽  
Study Sites

AbstractThe 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.

scholarly journals Long photoperiods sustain high pH in Arctic kelp forests

2016 ◽  
Vol 2 (12) ◽  
pp. e1501938 ◽  
Author(s):  
Dorte Krause-Jensen ◽  
Núria Marbà ◽  
Marina Sanz-Martin ◽  
Iris E. Hendriks ◽  
Jakob Thyrring ◽  
...  
Keyword(s):  
Gradual Increase ◽  
Sea Urchins ◽  
Kelp Forest ◽  
Kelp Forests ◽  
Arctic Vegetation ◽  
Seagrass Meadows ◽  
Potential Benefits ◽  
Ph Increase

Concern on the impacts of ocean acidification on calcifiers, such as bivalves, sea urchins, and foraminifers, has led to efforts to understand the controls on pH in their habitats, which include kelp forests and seagrass meadows. The metabolism of these habitats can lead to diel fluctuation in pH with increases during the day and declines at night, suggesting no net effect on pH at time scales longer than daily. We examined the capacity of subarctic and Arctic kelps to up-regulate pH in situ and experimentally tested the role of photoperiod in determining the capacity of Arctic macrophytes to up-regulate pH. Field observations at photoperiods of 15 and 24 hours in Greenland combined with experimental manipulations of photoperiod show that photoperiods longer than 21 hours, characteristic of Arctic summers, are conducive to sustained up-regulation of pH by kelp photosynthesis. We report a gradual increase in pH of 0.15 units and a parallel decline in pCO2of 100 parts per million over a 10-day period in an Arctic kelp forest over midsummer, with ample scope for continued pH increase during the months of continuous daylight. Experimental increase in CO2concentration further stimulated the capacity of macrophytes to deplete CO2and increase pH. We conclude that long photoperiods in Arctic summers support sustained up-regulation of pH in kelp forests, with potential benefits for calcifiers, and propose that this mechanism may increase with the projected expansion of Arctic vegetation in response to warming and loss of sea ice.

scholarly journals Coastal fish assemblages and predation pressure in northern-central Chilean Lessonia trabeculata kelp forests and barren grounds

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e6964 ◽  
Author(s):  
Nicolás Riquelme-Pérez ◽  
Catalina A. Musrri ◽  
Wolfgang B. Stotz ◽  
Osvaldo Cerda ◽  
Oscar Pino-Olivares ◽  
...  
Keyword(s):  
Fish Assemblages ◽  
Sea Urchins ◽  
Kelp Forest ◽  
Predation Pressure ◽  
Predatory Fish ◽  
The Black Sea ◽  
Kelp Forests ◽  
Fishing Activity ◽  
Rocky Habitats ◽  
Barren Grounds

Kelp forests are declining in many parts of the globe, which can lead to the spreading of barren grounds. Increased abundances of grazers, mainly due to reduction of their predators, are among the causes of this development. Here, we compared the species richness (SR), frequency of occurrence (FO), and maximum abundance (MaxN) of predatory fish and their predation pressure between kelp forest and barren ground habitats of northern-central Chile. Sampling was done using baited underwater cameras with vertical and horizontal orientation. Two prey organisms were used as tethered baits, the black sea urchin Tetrapygus niger and the porcelanid crab Petrolisthes laevigatus. SR did not show major differences between habitats, while FO and MaxN were higher on barren grounds in vertical videos, with no major differences between habitats in horizontal videos. Predation pressure did not differ between habitats, but after 24 h consumption of porcelanid crabs was significantly higher than that of sea urchins. Scartichthys viridis/gigas was the main predator, accounting for 82% of the observed predation events on Petrolisthes laevigatus. Most of these attacks occurred on barren grounds. Scartichthys viridis/gigas was the only fish observed attacking (but not consuming) tethered sea urchins. High abundances of opportunistic predators (Scartichthys viridis/gigas) are probably related to low abundances of large predatory fishes. These results suggest that intense fishing activity on large predators, and their resulting low abundances, could result in low predation pressure on sea urchins, thereby contributing to the increase of T. niger abundances in subtidal rocky habitats.

scholarly journals The zombification and reanimation of purple urchins (Strongylocentrotus purpuratus) in response to food availability

2021 ◽  
Author(s):  
Dillon Dolinar ◽  
Mathew Edwards
Keyword(s):  
Metabolic Activity ◽  
Sea Urchins ◽  
Strongylocentrotus Purpuratus ◽  
Energy Allocation ◽  
Poor Quality ◽  
Kelp Forests ◽  
Gonad Mass ◽  
Rocky Reefs ◽  
Access To Food ◽  
Primary Strategy

Abstract To survive periods of starvation, organisms can reduce their metabolism and/or decrease energy allocation to reproduction. This is especially important for coastal rocky reefs where widespread kelp deforestation has become increasingly common in recent decades. This deforestation often results in the formation of urchin barrens that have high densities of herbivorous sea urchins and little macroalgae for them to consume. While it is clear that these barrens can persist for years to decades, it is unclear how the urchins within them survive such prolonged periods without regular access to macroalgae. Here, we show that urchin metabolism and gonad mass both decrease significantly when the urchins are starved, and that these urchins regain normal metabolic activity and gonad masses when access to food is restored. However, if urchins occur in barren areas that receive drift algae from nearby kelp forests, it appears they can maintain normal metabolic activity and gonad mass. Together, our results provide experimental evidence that reducing metabolism may be a primary strategy for avoiding starvation in urchins occurring within barrens. Our results can be especially important to researchers looking to restore kelp forests and to urchin fishers who seek to harvest these urchins for their gonads but currently cannot because their gonads are of poor quality. Additionally, this has important implications for consumers in other ecosystems where access to energetic resources is spatially or temporally variable and can point to new avenues of research to explain how organisms adjust their energetic needs to survive extended periods of starvation.

scholarly journals Trophic downgrading reduces spatial variability on rocky reefs

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Matthew S. Edwards ◽  
Brenda Konar
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Kelp Forest ◽  
Small Scale ◽  
Kelp Forests ◽  
Forest Communities ◽  
Opposite Pattern ◽  
Rocky Reefs ◽  
Urchin Barren ◽  
Sea Urchin Barrens

Abstract Trophic downgrading in coastal waters has occurred globally during recent decades. On temperate rocky reefs, this has resulted in widespread kelp deforestation and the formation of sea urchin barrens. We hypothesize that the intact kelp forest communities are more spatially variable than the downgraded urchin barren communities, and that these differences are greatest at small spatial scales where the influence of competitive and trophic interactions is strongest. To address this, benthic community surveys were done in kelp forests and urchin barrens at nine islands spanning 1230 km of the Aleutian Archipelago where the loss of predatory sea otters has resulted in the trophic downgrading of the region’s kelp forests. We found more species and greater total spatial variation in community composition within the kelp forests than in the urchin barrens. Further, the kelp forest communities were most variable at small spatial scales (within each forest) and least variable at large spatial scales (among forests on different islands), while the urchin barren communities followed the opposite pattern. This trend was consistent for different trophic guilds (primary producers, grazers, filter feeders, predators). Together, this suggests that Aleutian kelp forests create variable habitats within their boundaries, but that the communities within these forests are generally similar across the archipelago. In contrast, urchin barrens exhibit relatively low variability within their boundaries, but these communities vary substantially among different barrens across the archipelago. We propose this represents a shift from small-scale biological control to large-scale oceanographic control of these communities.

scholarly journals Large-scale shift in the structure of a kelp forest ecosystem co-occurs with an epizootic and marine heatwave

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Meredith L. McPherson ◽  
Dennis J. I. Finger ◽  
Henry F. Houskeeper ◽  
Tom W. Bell ◽  
Mark H. Carr ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Large Scale ◽  
Nutrient Dynamics ◽  
Sea Urchins ◽  
Management Strategies ◽  
Kelp Forest ◽  
Kelp Forests ◽  
Predator Population ◽  
Northern California ◽  
Boundary Current

AbstractClimate change is responsible for increased frequency, intensity, and duration of extreme events, such as marine heatwaves (MHWs). Within eastern boundary current systems, MHWs have profound impacts on temperature-nutrient dynamics that drive primary productivity. Bull kelp (Nereocystis luetkeana) forests, a vital nearshore habitat, experienced unprecedented losses along 350 km of coastline in northern California beginning in 2014 and continuing through 2019. These losses have had devastating consequences to northern California communities, economies, and fisheries. Using a suite of in situ and satellite-derived data, we demonstrate that the abrupt ecosystem shift initiated by a multi-year MHW was preceded by declines in keystone predator population densities. We show strong evidence that northern California kelp forests, while temporally dynamic, were historically resilient to fluctuating environmental conditions, even in the absence of key top predators, but that a series of coupled environmental and biological shifts between 2014 and 2016 resulted in the formation of a persistent, altered ecosystem state with low primary productivity. Based on our findings, we recommend the implementation of ecosystem-based and adaptive management strategies, such as (1) monitoring the status of key ecosystem attributes: kelp distribution and abundance, and densities of sea urchins and their predators, (2) developing management responses to threshold levels of these attributes, and (3) creating quantitative restoration suitability indices for informing kelp restoration efforts.

Skeletal elements of crinoid echinoderms: High-resolution structural and microanalytical results

1983 ◽  
Vol 41 ◽  
pp. 194-195
Author(s):  
D. F. Blake ◽  
L. F. Allard ◽  
D. R. Peacor
Keyword(s):  
High Resolution ◽  
Marine Invertebrates ◽  
Sea Urchins ◽  
Structural Features ◽  
Sea Stars ◽  
High Resolution Tem ◽  
Relationship Of ◽  
The Relationship ◽  
Insight Into

Echinodermata is a phylum of marine invertebrates which has been extant since Cambrian time (c.a. 500 m.y. before the present). Modern examples of echinoderms include sea urchins, sea stars, and sea lilies (crinoids). The endoskeletons of echinoderms are composed of plates or ossicles (Fig. 1) which are with few exceptions, porous, single crystals of high-magnesian calcite. Despite their single crystal nature, fracture surfaces do not exhibit the near-perfect {10.4} cleavage characteristic of inorganic calcite. This paradoxical mix of biogenic and inorganic features has prompted much recent work on echinoderm skeletal crystallography. Furthermore, fossil echinoderm hard parts comprise a volumetrically significant portion of some marine limestones sequences. The ultrastructural and microchemical characterization of modern skeletal material should lend insight into: 1). The nature of the biogenic processes involved, for example, the relationship of Mg heterogeneity to morphological and structural features in modern echinoderm material, and 2). The nature of the diagenetic changes undergone by their ancient, fossilized counterparts. In this study, high resolution TEM (HRTEM), high voltage TEM (HVTEM), and STEM microanalysis are used to characterize tha ultrastructural and microchemical composition of skeletal elements of the modern crinoid Neocrinus blakei.

Mechanisms leading to recruitment inhibition of giant kelp Macrocystis pyrifera by an understory alga

2021 ◽  
Vol 657 ◽  
pp. 59-71
Author(s):  
BA Beckley ◽  
MS Edwards
Keyword(s):  
Field Experiments ◽  
Local Community ◽  
Kelp Forest ◽  
Macrocystis Pyrifera ◽  
Forest Recovery ◽  
Kelp Forests ◽  
Giant Kelp ◽  
Combined Effects ◽  
Life Stages ◽  
Survival And Growth

The forest-forming giant kelp Macrocystis pyrifera and the communities it supports have been decreasing across their native ranges in many parts of the world. The sudden removal of giant kelp canopies by storms increases space and light for the colonization by understory macroalgae, such as Desmarestia herbacea, which can inhibit M. pyrifera recovery and alter local community composition. Understanding the mechanisms by which algae such as D. herbacea interact with M. pyrifera can provide insight into patterns of kelp forest recovery following these disturbances and can aid in predicting future community structure. This study experimentally tested the independent and combined effects of two likely competitive mechanisms by which D. herbacea might inhibit recovery of M. pyrifera in the Point Loma kelp forest in San Diego, California (USA). Specifically, we conducted field experiments to study the individual and combined effects of shade and scour by D. herbacea on the survival of M. pyrifera microscopic life stages, and the recruitment, survival, and growth of its young sporophytes. Our results show that scour had the strongest negative effect on the survival of M. pyrifera microscopic life stages and recruitment, but shade and scour both adversely affected survival and growth of these sporophytes as they grew larger. Canopy-removing storms are increasing in frequency and intensity, and this change could facilitate the rise of understory species, like D. herbacea, which might alter community succession and recovery of kelp forests.

scholarly journals Effect of environmental history on the habitat-forming kelp Macrocystis pyrifera responses to ocean acidification and warming: a physiological and molecular approach

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Pamela A. Fernández ◽  
Jorge M. Navarro ◽  
Carolina Camus ◽  
Rodrigo Torres ◽  
Alejandro H. Buschmann
Keyword(s):  
Climate Change ◽  
Ocean Acidification ◽  
Environmental History ◽  
Coastal Upwelling ◽  
Macrocystis Pyrifera ◽  
Natural Variability ◽  
Kelp Forests ◽  
Species Response ◽  
Enhanced Expression ◽  
Mesocosm Experiments

AbstractThe capacity of marine organisms to adapt and/or acclimate to climate change might differ among distinct populations, depending on their local environmental history and phenotypic plasticity. Kelp forests create some of the most productive habitats in the world, but globally, many populations have been negatively impacted by multiple anthropogenic stressors. Here, we compare the physiological and molecular responses to ocean acidification (OA) and warming (OW) of two populations of the giant kelp Macrocystis pyrifera from distinct upwelling conditions (weak vs strong). Using laboratory mesocosm experiments, we found that juvenile Macrocystis sporophyte responses to OW and OA did not differ among populations: elevated temperature reduced growth while OA had no effect on growth and photosynthesis. However, we observed higher growth rates and NO3− assimilation, and enhanced expression of metabolic-genes involved in the NO3− and CO2 assimilation in individuals from the strong upwelling site. Our results suggest that despite no inter-population differences in response to OA and OW, intrinsic differences among populations might be related to their natural variability in CO2, NO3− and seawater temperatures driven by coastal upwelling. Further work including additional populations and fluctuating climate change conditions rather than static values are needed to precisely determine how natural variability in environmental conditions might influence a species’ response to climate change.

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