scholarly journals The sea urchin – the ultimate herbivore and biogeographic variability in its ability to deforest kelp ecosystems

2013 ◽  
Author(s):  
Jarrett E Byrnes ◽  
Ladd E. Johnson ◽  
Sean D. Connell ◽  
Nick T. Shears ◽  
Selena M McMillan ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Large Scale ◽  
Sea Urchins ◽  
Meta Analysis ◽  
Kelp Forest ◽  
Rocky Reef ◽  
Rocky Reefs ◽  
Iconic Images ◽  
Balance Of Forces ◽  
Almost All

Barren rocky seafloor landscapes, denuded of almost all life by ravenous sea urchins, liberated from their predators, stands as one of the iconic images of trophic cascades in Ecology. While this paradigm has been cited in nearly every temperate rocky reef ecosystem across the globe, there is widespread disagreement as to its generality. Given their biology, sea urchins are clearly one of the ocean’s strongest herbivores in many systems, but where will their impact be strongest? Here we perform a global meta-analysis of sea urchin-kelp relationships in the field. We find that sea urchins appear to be able to control kelp abundances in any system where they can achieve high densities. Furthermore, their ability to create large-scale long-lasting barrens appears to be limited to biogeographic regions where they can achieve high consumptive potential. Based on the literature, we outline a conceptual model that examines when and where sea urchins should be able to have a strong regulating impact on kelp forest ecosystems. We suggest that many elements of global change may shift the balance of forces regulating sea urchin consumptive potential in these ecosystems. Given their ability to have strong impacts on temperate rocky reefs, these drivers need to be considered in concert with their effect on sea urchins when attempting to predict future change to marine ecosystems.

scholarly journals The sea urchin – the ultimate herbivore and biogeographic variability in its ability to deforest kelp ecosystems

2013 ◽  
Author(s):  
Jarrett E Byrnes ◽  
Ladd E. Johnson ◽  
Sean D. Connell ◽  
Nick T. Shears ◽  
Selena M McMillan ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Large Scale ◽  
Sea Urchins ◽  
Meta Analysis ◽  
Kelp Forest ◽  
Rocky Reef ◽  
Rocky Reefs ◽  
Iconic Images ◽  
Balance Of Forces ◽  
Almost All

Barren rocky seafloor landscapes, denuded of almost all life by ravenous sea urchins, liberated from their predators, stands as one of the iconic images of trophic cascades in Ecology. While this paradigm has been cited in nearly every temperate rocky reef ecosystem across the globe, there is widespread disagreement as to its generality. Given their biology, sea urchins are clearly one of the ocean’s strongest herbivores in many systems, but where will their impact be strongest? Here we perform a global meta-analysis of sea urchin-kelp relationships in the field. We find that sea urchins appear to be able to control kelp abundances in any system where they can achieve high densities. Furthermore, their ability to create large-scale long-lasting barrens appears to be limited to biogeographic regions where they can achieve high consumptive potential. Based on the literature, we outline a conceptual model that examines when and where sea urchins should be able to have a strong regulating impact on kelp forest ecosystems. We suggest that many elements of global change may shift the balance of forces regulating sea urchin consumptive potential in these ecosystems. Given their ability to have strong impacts on temperate rocky reefs, these drivers need to be considered in concert with their effect on sea urchins when attempting to predict future change to marine ecosystems.

Survival and behaviour of juvenile red rock lobster, Jasus edwardsii, on rocky reefs with varying predation pressure and habitat complexity

2008 ◽  
Vol 59 (3) ◽  
pp. 246 ◽  
Author(s):  
K. A. S. Mislan ◽  
Russ C. Babcock
Keyword(s):  
New Zealand ◽  
Kelp Forest ◽  
Predatory Fish ◽  
Rocky Reef ◽  
Rocky Reefs ◽  
Jasus Edwardsii ◽  
Fish Predators ◽  
Two Factors ◽  
Direct And Indirect Impacts ◽  
Indirect Impacts

The role of large predatory fish in coastal communities is generally unknown because of overfishing. In order to understand the direct and indirect impacts of these increased population sizes on coastal food chains, the effect of areas with more fish predators on the survival and behaviour of potential prey was assessed. Juvenile lobsters, Jasus edwardsii (10–20 mm carapace length), were tethered on rocky reefs inside and outside marine reserves in northeastern New Zealand to assess survival under differing predator densities. Since rocky reef habitats in northeastern New Zealand include zones of kelp forest and barren reef, a two-way factorial design was used to determine the effects of predators, habitat, and the interaction of these two factors on juvenile lobster survival. Overall, the results indicated that neither varying large fish density nor varying kelp density had direct impacts on the survival rate of juvenile lobsters. Laboratory manipulations demonstrated behavioural changes by juvenile lobsters such that when a large predatory fish was present, juvenile lobsters spent significantly less time moving, even when separated from the predator by a porous barrier. Thus areas with more fish predators may increase juvenile lobster survival but potentially at the cost of reduced feeding opportunities.

Spatiotemporal variation in the structure of reef fish and macroalgal assemblages in a north-east Atlantic kelp forest ecosystem: implications for the management of temperate rocky reefs

2018 ◽  
Vol 69 (4) ◽  
pp. 525 ◽  
Author(s):  
Pablo Pita ◽  
Diana Fernández-Márquez ◽  
Juan Freire
Keyword(s):  
Reef Fish ◽  
Fish Assemblages ◽  
Kelp Forest ◽  
Habitat Destruction ◽  
Kelp Forests ◽  
Rocky Reef ◽  
Laminaria Hyperborea ◽  
East Atlantic ◽  
North East ◽  
Rocky Reefs

Temperate rocky reefs and kelp forest ecosystems have been severely affected by overfishing, pollution and habitat destruction, and climate change is a major driver of kelp decline in many regions. Although necessary for management, ecological interactions between kelp and fish remain largely unknown in the north-east Atlantic. In the present study, underwater visual censuses (UVC) and univariate and multivariate multiple regression models were used to analyse the spatiotemporal variations in the abundance and habitat use of the rocky reef fish and macroalgae assemblages of Galicia (north-west Spain). The underwater seascape was dominated by large rocks and kelp forests of Laminaria hyperborea, L. ochroleuca and Saccorhiza polyschides. Fish assemblages were ruled by gadids, labrids and sparids. The most frequent fish species were Labrus bergylta (counted in 90% of UVC) and Pollachius pollachius (in 100% of UVC), whereas the most abundant were Boops boops (mean±s.d., 556.4±39.7 individuals ha–1) and L. bergylta (432.10±440.05 individuals ha–1). Fish and macroalgal assemblages showed different spatial preferences and responded strongly to seasonality, wave exposure and depth. To a lesser degree, fish and macroalgal assemblages showed preferences for habitat structure. Moreover, because the findings of the present study indicate that L. bergylta is a good indicator species of the health of rocky reef and kelp forests ecosystems, monitoring of this fish can be helpful for management and conservation actions.

scholarly journals Going back into the wild: the behavioural effects of raising sea urchins in captivity

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
G Brundu ◽  
S Farina ◽  
P Domenici
Keyword(s):  
Sea Urchin ◽  
Natural Environment ◽  
Large Scale ◽  
Sea Urchins ◽  
Benthic Communities ◽  
Paracentrotus Lividus ◽  
Growth Efficiency ◽  
Behavioural Effects ◽  
External Cues ◽  
In Captivity

Abstract Sea urchin harvesting has rapidly expanded in the last decades. Since many sea urchin species play important ecological role, large-scale commercial sea urchin fisheries can have complex effects on benthic communities. In many temperate regions, overharvesting has compromised marine ecosystems to such an extent that reintroduction of sea urchins raised in captivity may be a valid solution for the enhancement of depleted marine wild populations. In some regions of the Mediterranean Sea, improving the growth efficiency of captive sea urchin Paracentrotus lividus to be reintroduced has become a widespread practice. However, no study has yet considered the potential behavioural effects of raising sea urchins in captivity when they are introduced in the natural environment. This study provides information about the behavioural effects of captivity on P. lividus in terms of locomotion performance, a trait that can be fundamental for responding to predators and for relocation after environmental disturbances such as currents and waves. Movements of captive-born and wild sea urchins were video-recorded and compared in (i) total exposure to external cues, (ii) partial exposure to external cues and (iii) absence of external cues. Latency of locomotion, average speed and average velocity of sea urchins showed significant differences with respect to the level of exposure and their origin (i.e. wild vs. captive-born). Our results demonstrate that captive-born sea urchins in the wild showed long latency and slower locomotor performance when compared to wild sea urchins. Conversely, the straightness-of-path and locomotion direction of captive-born and wild sea urchins were similar in natural settings. Our results therefore suggest that captive-born sea urchins suffer the negative effects of captivity when introduced in a natural environment. Understanding the factors that decrease the performance of sea urchin will be important for developing procedures aimed at minimizing the negative effect of captivity before release into the wild.

Determination and morphogenesis in the sea urchin embryo

Development ◽  
1987 ◽  
Vol 100 (4) ◽  
pp. 559-576 ◽  
Author(s):  
F.H. Wilt
Keyword(s):  
Sea Urchin ◽  
Sea Urchins ◽  
Secondary Phase ◽  
Animal Cells ◽  
Sea Urchin Embryo ◽  
Defect Isolation ◽  
Normal Larva ◽  
Mesenchyme Cells ◽  
The Stability ◽  
Almost All

The study of the sea urchin embryo has contributed importantly to our ideas about embryogenesis. This essay re-examines some issues where the concerns of classical experimental embryology and cell and molecular biology converge. The sea urchin egg has an inherent animal-vegetal polarity. An egg fragment that contains both animal and vegetal material will produce a fairly normal larva. However, it is not clear to what extent the oral-aboral axis is specified in embryos developing from meridional fragments. Newly available markers of the oral-aboral axis allow this issue to be settled. When equatorial halves, in which animal and vegetal hemispheres are separated, are allowed to develop, the animal half forms a ciliated hollow ball. The vegetal half, however, often forms a complete embryo. This result is not in accord with the double gradient model of animal and vegetal characteristics that has been used to interpret almost all defect, isolation and transplantation experiments using sea urchin embryos. The effects of agents used to animalize and vegetalize embryos are also due for re-examination. The classical animalizing agent, Zn2+, causes developmental arrest, not expression of animal characters. On the other hand, Li+, a vegetalizing agent, probably changes the determination of animal cells. The stability of these early determinative steps may be examined in dissociation-reaggregation experiments, but this technique has not been exploited extensively. The morphogenetic movements of primary mesenchyme are complex and involve a number of interactions. It is curious that primary mesenchyme is dispensable in skeleton formation since in embryos devoid of primary mesenchyme, the secondary mesenchyme cells will form skeletal elements. It is likely that during its differentiation the primary mesenchyme provides some of its own extracellular microenvironment in the form of collagen and proteoglycans. The detailed form of spicules made by primary mesenchyme is determined by cooperation between the epithelial body wall, the extracellular material and the inherent properties of primary mesenchyme cells. Gastrulation in sea urchins is a two-step process. The first invagination is a buckling, the mechanism of which is not understood. The secondary phase in which the archenteron elongates across the blastocoel is probably driven primarily by active cell repacking. The extracellular matrix is important for this repacking to occur, but the basis of the cellular-environmental interaction is not understood.(ABSTRACT TRUNCATED AT 400 WORDS)

Injured conspecifics as an alarm cue for the sea urchin Evechinus chloroticus

2020 ◽  
Vol 641 ◽  
pp. 135-144 ◽  
Author(s):  
AJP Spyksma ◽  
NT Shears ◽  
RB Taylor
Keyword(s):  
New Zealand ◽  
Sea Urchin ◽  
Trophic Cascade ◽  
Sea Urchins ◽  
Grazing Pressure ◽  
Alarm Cues ◽  
Large Fish ◽  
Lethal Effects ◽  
Rocky Reefs ◽  
Urchin Grazing

Predator mediation of sea urchin grazing pressure may occur via lethal removal of individual sea urchins or non-lethal modification of sea urchin behaviour. Several studies have shown that predation-related cues can affect sea urchin movement and grazing rates, but generalisations about the types of cues that prompt responses and the magnitude of those responses will require further research on a wider variety of species. We examined the effects of potential alarm cues on behaviour of the habitat-forming sea urchin Evechinus chloroticus (Echinometridae) on fished rocky reefs in northeastern New Zealand, where predators are uncommon and the sea urchins form barrens. Exposed E. chloroticus (i.e. those not in crevices) rapidly fled from injured conspecifics within a 1 m radius of the cue, but showed no apparent reaction to injured sea urchins belonging to another family (Centrostephanus rodgersii, Diadematidae), diced pilchards or the disturbance caused by fish attracted to the cues. Densities of exposed sea urchins in an area containing injured conspecifics did not return to control values for at least 20 h, while cryptic individuals remained crevice-bound when injured conspecifics were nearby. Injured conspecifics thus provide a strong, albeit localised, cue for E. chloroticus. By restricting sea urchins to crevices where they have a reduced impact on living kelp, this non-consumptive effect may complement the lethal effects of predation in marine reserves where populations of predators such as rock lobsters and large fish are allowed to recover from overharvesting by humans, thereby reinforcing the trophic cascade initiated by those predators.

Variation in abundances of herbivorous invertebrates in temperate subtidal rocky reef habitats

2004 ◽  
Vol 55 (1) ◽  
pp. 93 ◽  
Author(s):  
Mathew A. Vanderklift ◽  
Gary A. Kendrick
Keyword(s):  
Sea Urchin ◽  
Western Australia ◽  
Sea Urchins ◽  
Habitat Partitioning ◽  
Rocky Reef ◽  
Heliocidaris Erythrogramma ◽  
A Minor ◽  
Different Parts ◽  
Over Time ◽  
Rock Faces

The present study assessed variation in the abundances of large herbivorous invertebrates in south-western Australia. There was some habitat partitioning between different parts of the reef: of the most frequently recorded species, the sea urchins Phyllacanthus irregularis and Centrostephanus tenuispinus were found primarily at the base of steep rock faces, whereas the gastropods Turbo torquatus and Australium squamifera were found primarily on open sections of reef. The sea urchin Heliocidaris erythrogramma was evenly distributed between these two habitats. For C. tenuispinus and H. erythrogramma, differences among locations (separated by tens to hundreds of kilometers) were the main source of variation in abundances. Phyllacanthus irregularis was more evenly distributed among locations. Abundances of sea urchins at each reef varied little over 26 months, suggesting low mortality and low recruitment. Turbo torquatus and A. squamifera varied significantly in abundance among reefs separated by < 10 km, although these differences were influenced by fluctuations over time. Broad patterns in abundances were evident: overall, abundances of herbivorous invertebrates were low, but certain areas supported high abundances. This suggests that herbivory may be a minor process in this region; however, the importance of herbivory at reefs with and without high abundances of herbivores deserves further attention.

scholarly journals Predators indirectly induce stronger prey through a trophic cascade

2017 ◽  
Vol 284 (1866) ◽  
pp. 20171440 ◽  
Author(s):  
Arie J. P. Spyksma ◽  
Nick T. Shears ◽  
Richard B. Taylor
Keyword(s):  
Sea Urchin ◽  
Resource Availability ◽  
Food Supply ◽  
Trophic Cascade ◽  
Prey Species ◽  
Sea Urchins ◽  
Rocky Reefs ◽  
Effect Of Food ◽  
Positive Effect ◽  
Predator Effects

Many prey species induce defences in direct response to predation cues. However, prey defences could also be enhanced by predators indirectly via mechanisms that increase resource availability to prey, e.g. trophic cascades. We evaluated the relative impacts of these direct and indirect effects on the mechanical strength of the New Zealand sea urchin Evechinus chloroticus . We measured crush-resistance of sea urchin tests (skeletons) in (i) two marine reserves, where predators of sea urchins are relatively common and have initiated a trophic cascade resulting in abundant food for surviving urchins in the form of kelp, and (ii) two adjacent fished areas where predators and kelps are rare. Sea urchins inhabiting protected rocky reefs with abundant predators and food had more crush-resistant tests than individuals on nearby fished reefs where predators and food were relatively rare. A six-month long mesocosm experiment showed that while both food supply and predator cues increased crush-resistance, the positive effect of food supply on crush-resistance was greater. Our results demonstrate a novel mechanism whereby a putative morphological defence in a prey species is indirectly strengthened by predators via cascading predator effects on resource availability. This potentially represents an important mechanism that promotes prey persistence in the presence of predators.

scholarly journals Marine heat wave and multiple stressors tip bull kelp forest to sea urchin barrens

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
L. Rogers-Bennett ◽  
C. A. Catton
Keyword(s):  
Sea Urchin ◽  
Large Scale ◽  
Multiple Stressors ◽  
Kelp Forest ◽  
Ocean Warming ◽  
Forest Recovery ◽  
Population Increase ◽  
North Coast ◽  
Sea Stars ◽  
Sea Urchin Barrens

Abstract Extreme climatic events have recently impacted marine ecosystems around the world, including foundation species such as corals and kelps. Here, we describe the rapid climate-driven catastrophic shift in 2014 from a previously robust kelp forest to unproductive large scale urchin barrens in northern California. Bull kelp canopy was reduced by >90% along more than 350 km of coastline. Twenty years of kelp ecosystem surveys reveal the timing and magnitude of events, including mass mortalities of sea stars (2013-), intense ocean warming (2014–2017), and sea urchin barrens (2015-). Multiple stressors led to the unprecedented and long-lasting decline of the kelp forest. Kelp deforestation triggered mass (80%) abalone mortality (2017) resulting in the closure in 2018 of the recreational abalone fishery worth an estimated $44 M and the collapse of the north coast commercial red sea urchin fishery (2015-) worth $3 M. Key questions remain such as the relative roles of ocean warming and sea star disease in the massive purple sea urchin population increase. Science and policy will need to partner to better understand drivers, build climate-resilient fisheries and kelp forest recovery strategies in order to restore essential kelp forest ecosystem services.

scholarly journals Global regime shift dynamics of catastrophic sea urchin overgrazing

2015 ◽  
Vol 370 (1659) ◽  
pp. 20130269 ◽  
Author(s):  
S. D. Ling ◽  
R. E. Scheibling ◽  
A. Rassweiler ◽  
C. R. Johnson ◽  
N. Shears ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Regime Shift ◽  
Marine Ecosystems ◽  
Rocky Reef ◽  
Rocky Reefs ◽  
Alternative State ◽  
Order Of Magnitude ◽  
Global Regime ◽  
Shift Dynamics

A pronounced, widespread and persistent regime shift among marine ecosystems is observable on temperate rocky reefs as a result of sea urchin overgrazing. Here, we empirically define regime-shift dynamics for this grazing system which transitions between productive macroalgal beds and impoverished urchin barrens. Catastrophic in nature, urchin overgrazing in a well-studied Australian system demonstrates a discontinuous regime shift, which is of particular management concern as recovery of desirable macroalgal beds requires reducing grazers to well below the initial threshold of overgrazing. Generality of this regime-shift dynamic is explored across 13 rocky reef systems (spanning 11 different regions from both hemispheres) by compiling available survey data (totalling 10 901 quadrats surveyed in situ ) plus experimental regime-shift responses (observed during a total of 57 in situ manipulations). The emergent and globally coherent pattern shows urchin grazing to cause a discontinuous ‘catastrophic’ regime shift, with hysteresis effect of approximately one order of magnitude in urchin biomass between critical thresholds of overgrazing and recovery. Different life-history traits appear to create asymmetry in the pace of overgrazing versus recovery. Once shifted, strong feedback mechanisms provide resilience for each alternative state thus defining the catastrophic nature of this regime shift. Importantly, human-derived stressors can act to erode resilience of desirable macroalgal beds while strengthening resilience of urchin barrens, thus exacerbating the risk, spatial extent and irreversibility of an unwanted regime shift for marine ecosystems.

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