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Author: Arie J.P. Spyksma Publisher: ISBN: Category : Predation (Biology) Languages : en Pages : 180
Book Description
Predators have well documented density-mediated effects on sea urchin populations, which can indirectly influence sea urchin resources (predominantly macroalgae) via a trophic cascade. Less is known about how predators may affect sea urchin behaviour and morphology and the ecological implications of these interactions. Predators may directly affect sea urchin behaviour and morphology through trait-mediated interactions, or they may indirectly affect these characteristics via cascading trophic effects that increase sea urchin food availability, resulting in behaviours or morphologies similar to those expressed in direct response to predators. Using a range of field and laboratory experiments I aimed to determine the direct and indirect effects of predators on the behaviour and morphology of the habitatforming sea urchin Evechinus chloroticus. In two well-established north-eastern New Zealand marine reserves, where large snapper (Pagrus auratus) and rock lobster (Jasus edwardsii) have suppressed grazing by E. chloroticus with a resultant increase in kelp densities, E. chloroticus remained cryptic in crevices to significantly larger sizes than individuals on the adjacent overfished reefs. Crevice occupancy in sea urchins has previously been attributed to either predator avoidance or a response to plentiful food in the form of kelp detritus. E. chloroticus in the marine reserves had much greater access to kelp and other macroalgae than those in the barrens habitat on fished reefs, meaning predators could be responsible for cryptic behaviour via direct (predator avoidance) and/or indirect (trophic cascade) mechanisms. A mesocosm experiment, using adult sea urchins, found that the addition of predation cues (injured conspecifics) strongly increased cryptic behaviour, but food availability had no effect. Sea urchins within marine reserves were found to have thicker, more crush-resistant tests than those on the adjacent overfished reefs. This putative structural defence could be directly induced by predation cues, or indirectly induced in response to the greater food supply arising from the cascading effect that predation on sea urchins has on kelp abundance. In a six month-long mesocosm experiment, well-fed juvenile sea urchins developed less porous, more crush-resistant tests than those that were poorly fed. Predation cues alone had a relatively minor effect on crush-resistance. A number of field experiments were carried out to further examine the behavioural response of sea urchins to predation cues from injured conspecifics. Exposed E. chloroticus fled from cues released by injured conspecifics, but not those from an extraneous pilchard cue, alarm cues from an injured heterospecific, or the disturbance caused by fish attracted to the cues, indicating that E. chloroticus can distinguish between different cues. The response to injured conspecific cues was limited to within one meter of the cue. Exposed sea urchins avoided reentering an area containing cues throughout the night while in areas where sea urchins were predominantly cryptic an injured conspecific above the crevices restricted the number of sea urchins leaving during the night in order to find food on the reef. On barren reefs sea urchins densities recovered within several days following a 'predation event'. Overall, the results show that predators directly affect the behaviour of E. chloroticus by causing them to flee or increasing their use of crevices and indirectly affect their morphology by increasing their supply of food. Predator induced changes in behaviour and morphology are likely to enable sea urchin populations to persist in areas where predation pressure is high. Where sea urchins are able to shelter from their predators, predation cues are also likely to play an important role in facilitating behaviourally-mediated trophic cascades or maintaining areas of existing kelp forest.
Author: Arie J.P. Spyksma Publisher: ISBN: Category : Predation (Biology) Languages : en Pages : 180
Book Description
Predators have well documented density-mediated effects on sea urchin populations, which can indirectly influence sea urchin resources (predominantly macroalgae) via a trophic cascade. Less is known about how predators may affect sea urchin behaviour and morphology and the ecological implications of these interactions. Predators may directly affect sea urchin behaviour and morphology through trait-mediated interactions, or they may indirectly affect these characteristics via cascading trophic effects that increase sea urchin food availability, resulting in behaviours or morphologies similar to those expressed in direct response to predators. Using a range of field and laboratory experiments I aimed to determine the direct and indirect effects of predators on the behaviour and morphology of the habitatforming sea urchin Evechinus chloroticus. In two well-established north-eastern New Zealand marine reserves, where large snapper (Pagrus auratus) and rock lobster (Jasus edwardsii) have suppressed grazing by E. chloroticus with a resultant increase in kelp densities, E. chloroticus remained cryptic in crevices to significantly larger sizes than individuals on the adjacent overfished reefs. Crevice occupancy in sea urchins has previously been attributed to either predator avoidance or a response to plentiful food in the form of kelp detritus. E. chloroticus in the marine reserves had much greater access to kelp and other macroalgae than those in the barrens habitat on fished reefs, meaning predators could be responsible for cryptic behaviour via direct (predator avoidance) and/or indirect (trophic cascade) mechanisms. A mesocosm experiment, using adult sea urchins, found that the addition of predation cues (injured conspecifics) strongly increased cryptic behaviour, but food availability had no effect. Sea urchins within marine reserves were found to have thicker, more crush-resistant tests than those on the adjacent overfished reefs. This putative structural defence could be directly induced by predation cues, or indirectly induced in response to the greater food supply arising from the cascading effect that predation on sea urchins has on kelp abundance. In a six month-long mesocosm experiment, well-fed juvenile sea urchins developed less porous, more crush-resistant tests than those that were poorly fed. Predation cues alone had a relatively minor effect on crush-resistance. A number of field experiments were carried out to further examine the behavioural response of sea urchins to predation cues from injured conspecifics. Exposed E. chloroticus fled from cues released by injured conspecifics, but not those from an extraneous pilchard cue, alarm cues from an injured heterospecific, or the disturbance caused by fish attracted to the cues, indicating that E. chloroticus can distinguish between different cues. The response to injured conspecific cues was limited to within one meter of the cue. Exposed sea urchins avoided reentering an area containing cues throughout the night while in areas where sea urchins were predominantly cryptic an injured conspecific above the crevices restricted the number of sea urchins leaving during the night in order to find food on the reef. On barren reefs sea urchins densities recovered within several days following a 'predation event'. Overall, the results show that predators directly affect the behaviour of E. chloroticus by causing them to flee or increasing their use of crevices and indirectly affect their morphology by increasing their supply of food. Predator induced changes in behaviour and morphology are likely to enable sea urchin populations to persist in areas where predation pressure is high. Where sea urchins are able to shelter from their predators, predation cues are also likely to play an important role in facilitating behaviourally-mediated trophic cascades or maintaining areas of existing kelp forest.
Author: Publisher: ISBN: Category : Electronic books Languages : en Pages : 183
Book Description
The interactions between predators and their prey are key drivers of structure and functioning in many ecosystems. However, the ability of predators to effectively regulate prey abundance can be strongly modified by the context in which trophic interactions occur. My dissertation explores the effects of five factors which have the potential to mediate trophic interactions on nearshore reefs: prey density, organismal body size, habitat complexity, animal behavior, and fishery harvest. Working on both temperate rocky reefs and tropical coral reefs, I use field- and lab-based experiments as well as a numerical model to better understand the interactions among sea urchins, their finfish and invertebrate predators, and the nearshore reefassociated communities of which they are a part. Chapters 1 and 2 focus on the dynamics between sea urchins, spiny lobsters, and fish predators on the rocky reefs of southern California. Following the extirpation of the archetypal urchin predator, the sea otter (Enhydra lutris), top-down control of urchins in this system by spiny lobsters (Panulirus interruptus) and the labrid fish California sheephead (Semicossyphus pulcher), has been hypothesized, but rarely tested experimentally. Chapter 1 tests for densitydependent mortality of purple (Strongylocentrotus purpuratus) and red (Mesocentrotus franciscanus) urchins due to predation by finfish and lobsters. In laboratory feeding assays, spiny lobsters demonstrate a saturating functional response to urchin prey, whereby urchin proportional mortality is inversely density-dependent. In field experiments on rocky reefs near San Diego, CA, when purple urchins are offered alone, I find evidence of positive density-dependent urchin mortality at low densities, similar to those found within kelp forests. At higher prey densities, analogous to those found within urchin barrens, prey mortality is density-independent. When red and purple urchins are deployed to reefs simultaneously, urchin mortality is density-independent and fish do not aggregate to higher density patches. This shift in predation mortality is likely due to the increased biomass of the alternative red urchin prey rather than the increased structural complexity offered by their large spine canopy. Overall, results from Chapter 1 suggest that topdown control of urchins can occur only under limited circumstances, when predatory fish are abundant and large red urchins are absent. In Chapter 2, I develop a tri-trophic, size-structured numerical model of a southern California rocky reef. The model includes multiple ecological processes that can drive feedbacks across trophic levels leading to alternative stable states, including recruitment facilitation and size-structured predation. I find that fishery harvest for the predator (spiny lobster) and prey (red urchins) interacts to determine the level of ecological resilience exhibited by the system, i.e. the likelihood of shifting between alternative stable states. Specifically, I show that predator harvest can drive the system from a kelp forest to an urchin barren, but that prey harvest determines the likelihood of this shift. Size-structured predation on urchins is the feedback maintaining a given ecosystem state. This model suggests that ecosystem resilience depends on both predator and prey harvest in multi-trophic level harvest scenarios, which are common in marine ecosystems but are rarely accounted for by traditional single-species management. Collectively, my first two chapters demonstrate that predator regulation of urchins can occur only under limited circumstances which strongly depend on both predator and prey body size and species composition. These findings also have significant implications for the dynamics of alternative community states observed on rocky reefs, as harvesting predators and harvesting prey can interact to determine the ecological resilience of these important coastal habitats. In addition to density and organismal body size, habitat complexity can also play a vital role in shaping ecological communities. However, many coral reef ecosystems are shifting to alternative states with reduced structural complexity and altered community assemblages. Smallbodied herbivores, such as sea urchins, are common inhabitants of reefs, and their importance for controlling the distribution and abundance of algae in marine ecosystems is well understood. Less understood is the role of habitat complexity and species identity of foundational species in dictating the abundance of this increasingly-important group of herbivores. In Chapters 3 and 4, I explore the feedbacks between habitat complexity, herbivorous urchins, and their predators on fringing coral reefs of Bocas del Toro, located on the Caribbean coast of Panama. In Chapter 3, I use benthic surveys, tethering, and laboratory experiments to show that the structural complexity and species identity of three corals commonly observed on Caribbean reefs mediate the abundance, behavior, and demographic characteristics of an increasingly important herbivore, the reef urchin Echinometra viridis. Tethered urchins survive better on the more structurally complex coral Agaricia tenuifolia and hydrocoral Millepora alcicornis than on less complex branching Porites species. However, natural densities of urchins on these corals do not follow the same pattern, suggesting that coral identity, independent of complexity, also contributes to habitat associations. In habitat choice experiments, urchins prefer the structurally complex coral A. tenuifolia only when waterborne cues of predators are introduced. Despite minimal differences in the standing stock of algae associated with the different corals, urchins inhabiting Porites colonies have a marginally higher reproductive condition than those collected from the other corals, suggesting a fitness trade off to inhabiting the riskier coral. Understanding the drivers of herbivore habitat associations is vital for predicting the persistence of coral-dominated reefs due to feedbacks between changing coral reef communities (both species identity and habitat complexity) and shifts to algal dominance. In Chapter 4, I explore the potential for non-consumptive effects (NCEs) of predatory spiny lobsters on the grazing and movement behaviors of two urchins (E. viridis and Diadema antillarum) which contribute to Caribbean coral reef resilience. Non-consumptive effects of predators on their prey can be an important influence on ecosystems because predators can suppress the ecological function of far more prey than they can consume. However, herbivore responses to predatory risk cues can differ among species which otherwise could be functionally similar. Cues from a generalist predator, the Caribbean spiny lobster (Panulirus argus), strongly suppress grazing by Diadema but not Echinometra. Conversely, cues produced by simulated predation on conspecific urchins cause reduced grazing by Echinometra but not Diadema. In field tests for NCEs on movement behavior, Echinometra consistently move away from lobsters on coral colonies of a variety of structural complexity levels, but movement rates are reduced in response to lobster cues only when on highly rugose corals. Diadema movement is not affected by the presence of lobsters. The contrasting responses exhibited by these two urchins suggest that herbivore populations and their functional roles may respond in unexpected ways to anthropogenic changes to predator communities and reef structural complexity. Together, these chapters provide evidence of the importance of small-bodied herbivores to Caribbean coral reef resilience through feedbacks between herbivory and habitat complexity and improve our understanding of trophic interactions on degraded contemporary coral reefs.
Author: Maria Agnello Publisher: BoD – Books on Demand ISBN: 9535135252 Category : Technology & Engineering Languages : en Pages : 156
Book Description
This book is addressed to the readers operating in the sea urchin field of research, as well as to the lovers of this fascinating organism. Sea urchin, among the most known marine invertebrates belonging to the deuterostomes, is more closely related to humans than other invertebrates, thus representing a suitable model system not only for developmental biology and ecotoxicology but also for biomedicine. The topics described highlight the validity and versatility of this organism for different kinds of investigations. A collection of interesting chapters contributes to this volume and clearly shows the reason of the high interest manifested by a huge number of scientists around the world for this organism over time. Each contribution is a separate and comprehensive chapter but within the book's aim.
Author: John M. Lawrence Publisher: Elsevier ISBN: 0080530702 Category : Technology & Engineering Languages : en Pages : 429
Book Description
Sea urchins are a major component of marine environments found throughout the world's oceans. A major model for research in developmental biology, they are also of major economic importance in many regions and interest in their management and aquaculture has increased greatly in recent years. This book provides a synthesis of biological and ecological characteristics of sea urchins that are of basic scientific interest and also essential for effective fisheries management and aquaculture. General chapters consider characteristics of sea urchins as a whole. In addition, specific chapters are devoted to the ecology of 17 species that are of major commercial interest and ecological importance.Features include: • A synthesis of what is known about the basic biological characteristics of the sea urchin, useful for the direction of future research. • Case histories of 17 species that illustrate their ecological role in a variety of environments. • With the catastrophic decline in fisheries resulting primarily from over-fishing, it is essential that the populations be managed effectively and that aquaculture be developed. This book provides knowledge of the biology and ecology of the commercially important sea urchins that will contribute to these goals. • The only book available in present literature devoted to sea urchins.With this new title experts provide a broad synthetic treatment and in depth analysis of the biology and ecology of sea urchins from around the world, designed to provide an understanding of the group and the basis for fisheries management and aquaculture.
Author: John M. Lawrence Publisher: Academic Press ISBN: 0128195703 Category : Science Languages : en Pages : 734
Book Description
Sea Urchins: Biology and Ecology, Fourth Edition, Volume 43 expands its coverage to include the entire class of Echinoidea, making this new edition an authoritative reference of the entire class of species. This is a valuable resource that will help readers gain a deep understanding of the basic characteristics of sea urchins, the basis of the great variation that exists in sea urchins, and how sea urchins are important components of marine ecosystems. Updated coverage includes sections on reproduction, metabolism, endocrinology, larval ecology, growth, digestion, carotenoids and disease. Includes pertinent tables and graphs within chapters to visually summarize information Provides case studies with research applications to provide potential solutions Includes the entire class of Echinoidea and the effect of climate change on the biology and ecology of the species
Author: Edgar Raymond Banks Publisher: Nova Science Pub Incorporated ISBN: 9781633215177 Category : Science Languages : en Pages : 116
Book Description
Sea urchins play a key role in marine ecosystems, controlling through its grazing activity the dynamic, structure and composition of seaweed and sea grasses. Moreover, it is a crucial component of the food web, as prey for fishes and other marine animals. Due to its sedentary habits and sensitivity to pollutants, adult sea urchin has been used in several studies as a biological-biochemical indicator of local pollution. This book provides several topics on sea urchins. It discusses the phenotypic variation and resilience in sea urchin morphogenesis; response of sea urchins to environmental stress; nonparametric regression applied to sea urchin growth; and sea urchin immune systems.
Author: Stephen J. Hawkins Publisher: Cambridge University Press ISBN: 110841608X Category : Nature Languages : en Pages : 535
Book Description
A comprehensive account of how abiotic and biotic interactions shape patterns of coastal marine biodiversity and ecosystem processes globally.
Author: Kathleen Anne MacGregor Publisher: ISBN: Category : Languages : en Pages : 126
Book Description
Feeding and the search for food are one of the most important activities of all mobile animals, providing individuals with the energy and resources to grow and reproduce. Foraging is fundamentally concerned with movement through an explicit landscape. Marine environments present a set of unique opportunities and challenges for mobile foragers because water is much denser than air and exerts significant drag and lift forces on benthic organisms moving across the bottom. Substratum type, therefore, functions as a key determinant of movement in subtidal marine environments. Urchins (Phylum Echinodermata, Class Echinoidea) are one of the most important marine grazers worldwide. When urchin populations are large, they can overgraze brown macroalgal (kelp) beds and form urchin barren grounds, characterized by a complete lack of kelp and high densities of urchins. Under such conditions, the foraging of adult urchins largely determines the state of subtidal benthic habitats by limiting the recolonization of macroalgae. Urchins in barren grounds thus exist in a resource-limited state, and the rapid detection and consumption of resource patches, particularly pieces of macroalgae from adjacent algal beds, is therefore key in determining individual growth and reproduction. However, there are very few detailed examinations of urchin movement and none which explicitly take both seascape and the presence of food into account, making predictions about community responses to environmental changes difficult. My objective in this thesis was to evaluate the environmental factors modifying the movement behaviour of urchins in barren grounds, including the role of environment in determining the response of these communities to perturbations such as a fishery or disease outbreak which entail a reduction in urchin numbers and biomass. First, I combined a global literature review of previous experimental manipulations of urchin abundances with my own replicated urchin removal experiment in order to examine the causal link between grazing pressure exerted by urchins and macroalgal colonization and growth. In the published literature, urchin removals result in kelp colonization in only two thirds of cases worldwide. In my own manipulations in the Gulf of St. Lawrence, site was the most important determinant of successful reduction of urchin densities. Spatial variability, possibly related to the strength of indirect interactions such as competition between large and small urchins, was essential in determining the outcomes of perturbation experiments. In order to examine the movement behaviour that could explain the spatial variability in community response in detail, I then experimentally manipulated substrata composition in the field to examine the interacting effects of substrata and the presence of drift kelp on urchin movement behaviour. Unstable substrata (sand) did not function as absolute barriers to urchin movement in barren grounds, but urchin densities were lower on sand relative to adjacent rocky substrata, and sand barriers slowed cumulative consumption of drift kelp. Once again, however, there were clear and consistent site-to-site differences in movement behaviour, possibly related to the size-structure of urchin populations. Sand patches v appear to reduce movement of very large urchins (test diameter > 50 mm) but not of medium-sized urchins (test diameter of 20-50 mm). Finally, I used time-lapse photography to describe the movements of individual urchins in relation to the presence of kelp and differences in seascape substratum composition. Green sea urchins were able to detect the presence of drift kelp in barren ground habitats and alter their movement behaviour in response but did not move directly towards the kelp. Seascapes with increased proportions of rocky substrata facilitated increased urchin movement in response to the presence of drift, but only in the summer and not in spring. The intriguing relationships between movement behaviour and urchin size at specific sites combined with the observed seasonal variability indicate that the role of seascape in determining the movement behaviour of urchins is complex and modified by important intrinsic and extrinsic factors. My results are the first detailed observations of urchin movement in a spatially explicit context and clearly demonstrate that a mechanistic understanding of the responses of barren ground systems to future perturbations must include detailed information on environmental modification of behaviour.
Author: Arie J.P. Spyksma
Author: Arie J.P. Spyksma
Author: Kathryn D. Nichols
Author: 
Author: Tori Miller
Author: Maria Agnello
Author: John M. Lawrence
Author: John M. Lawrence
Author: Edgar Raymond Banks
Author: Stephen J. Hawkins
Author: Kathleen Anne MacGregor