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Consumption rates of a key marine herbivore: a review of the extrinsic and intrinsic control of feeding in the green sea urchin

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Thew Suskiewicz at Atlantic Sea Farms
Thew Suskiewicz
  • Atlantic Sea Farms
Ladd E. Johnson at Université Laval
Ladd E. Johnson
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Abstract and Figures

Herbivory fundamentally shapes ecosystem functioning by influencing the abundance and distribution of plants. Whereas a great deal of attention has been given to factors that influence rates of primary productivity (e.g., light, temperature and nutrients), considerably less attention has been given to factors governing herbivory rates. In the marine environment, urchins are a dominant herbivore on rocky shores, and their grazing often leads to overconsumption and the formation of “barren grounds” with few fleshy macroalgae. However, despite decades of laboratory experiments and field observations, there is still a high degree of uncertainty with regard to the factors that control sea urchin consumption rates. To synthesize current knowledge on this subject, we compiled and analyzed data from the peer-reviewed literature on consumption rates of the green urchin, Strongylocentrotus droebachiensis, to examine the effects of intrinsic (e.g., size) and extrinsic (e.g., temperature and algal type) factors. Generally, urchins consumed 1.3–4.1% of their body weight per day, though the range was much greater (0.1–18%) when all measurements were included. Not surprisingly, larger urchins ate more than smaller urchins, but this difference was almost entirely attributed to differences in body mass and when expressed as mass-specific rates, small urchins consumed food at the same rate as large urchins. A simple measure of total urchin biomass thus appears sufficient for estimating potential herbivory at a given location. More surprising, temperature had no discernible effect on feeding rates despite our expectations and assertions in the literature. Although consumption rates of different macroalgae varied, urchins consumed all 42 taxa presented to them. Generally kelps (excluding Agarum sp.) and green algae were eaten the fastest. However, species that were typically favored were occasionally ignored, and chemically defended species that were generally ignored (e.g., Agarum sp.) were occasionally eaten at very high rates, making predictions of consumption rates difficult. Our review provides estimates of the maximum amount of algae an urchin can consume and when coupled with the potential productivity of an area, may help identify ecological tipping points between productive kelp beds and urchin barrens.
a Consumption (g ind⁻¹) as a function of test diameter (i.e. not as a function of body weight). Solid line is exponential regression line. Dashed lines are 95% CI. R² = 0.54, p < 0.001, F1,73 = 85.81. b Mass-specific consumption (%body weight) as a function of test diameter. Values for kelp only (excluding Agarum sp.). Lines are non-significant linear regressions including and excluding outliers (closed circles; thin dotted and thick dashed lines, respectively)—see text for justification and regressions
a Consumption (g ind⁻¹) as a function of test diameter (i.e. not as a function of body weight). Solid line is exponential regression line. Dashed lines are 95% CI. R² = 0.54, p < 0.001, F1,73 = 85.81. b Mass-specific consumption (%body weight) as a function of test diameter. Values for kelp only (excluding Agarum sp.). Lines are non-significant linear regressions including and excluding outliers (closed circles; thin dotted and thick dashed lines, respectively)—see text for justification and regressions
… 
Consumption rates as a function of temperature in six different laboratory studies. Each line represents a different food type (see Table 1 and publications for details). Data from a Dagget et al. (2005); b Keats et al. (1984); c Knip and Scheibling (2007); d Miller and Mann (1973); e Lyons and Scheibling (2007) and f Larson et al. (1980). Temperature is plotted independently of time, but none of the studies manipulated temperature
Consumption rates as a function of temperature in six different laboratory studies. Each line represents a different food type (see Table 1 and publications for details). Data from a Dagget et al. (2005); b Keats et al. (1984); c Knip and Scheibling (2007); d Miller and Mann (1973); e Lyons and Scheibling (2007) and f Larson et al. (1980). Temperature is plotted independently of time, but none of the studies manipulated temperature
… 
Consumption rates of non-Agarum kelp as a function of temperature. Dashed line is non-significant linear regression (R² < 0.001, p = 0.46; n = 55)
Consumption rates of non-Agarum kelp as a function of temperature. Dashed line is non-significant linear regression (R² < 0.001, p = 0.46; n = 55)
… 
Consumption rates as a function of algal taxa. Solid line median value. Vertical area within box represents 1st and 3rd quartile. Box width is proportional to sample size. Outliers (circles) are ±1.5 IQR. Consumption rates are grouped by taxonomic a division, b non-kelp genera, and c kelp genera. For the latter two, the number immediately after genus is the total number of species within the genus in which consumption rates were measured. Number in parenthesis is the total number of studies that tested the taxon in question. Different letters represent significantly different groups
Consumption rates as a function of algal taxa. Solid line median value. Vertical area within box represents 1st and 3rd quartile. Box width is proportional to sample size. Outliers (circles) are ±1.5 IQR. Consumption rates are grouped by taxonomic a division, b non-kelp genera, and c kelp genera. For the latter two, the number immediately after genus is the total number of species within the genus in which consumption rates were measured. Number in parenthesis is the total number of studies that tested the taxon in question. Different letters represent significantly different groups
… 
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Mar Biol (2017) 164:131
DOI 10.1007/s00227-017-3159-0
FEATURE ARTICLE
Consumption rates of a key marine herbivore: a review
of the extrinsic and intrinsic control of feeding in the
green sea urchin
T. S. Suskiewicz1 · L. E. Johnson1
Received: 28 November 2016 / Accepted: 3 May 2017 / Published online: 15 May 2017
© Springer-Verlag Berlin Heidelberg 2017
this difference was almost entirely attributed to differences in
body mass and when expressed as mass-specific rates, small
urchins consumed food at the same rate as large urchins. A
simple measure of total urchin biomass thus appears suffi-
cient for estimating potential herbivory at a given location.
More surprising, temperature had no discernible effect on
feeding rates despite our expectations and assertions in the
literature. Although consumption rates of different macroal-
gae varied, urchins consumed all 42 taxa presented to them.
Generally kelps (excluding Agarum sp.) and green algae
were eaten the fastest. However, species that were typically
favored were occasionally ignored, and chemically defended
species that were generally ignored (e.g., Agarum sp.) were
occasionally eaten at very high rates, making predictions of
consumption rates difficult. Our review provides estimates of
the maximum amount of algae an urchin can consume and
when coupled with the potential productivity of an area, may
help identify ecological tipping points between productive
kelp beds and urchin barrens.
Introduction
Primary productivity and herbivory are two fundamental
ecological processes that shape natural communities, but
both rates can be affected by the intrinsic properties of the
producers and consumers themselves, and the extrinsic prop-
erties of the environment in which they live. In the marine
environment, much attention has been paid to factors gov-
erning primary productivity (e.g., light, temperature, nutri-
ents; Druehl 1970; Chapman and Lindley 1980; Bokn et al.
2003; Kraufvelin et al. 2012), but in contrast, comparatively
little is known about the processes that control consumption
rates of herbivores. The balance between rates of herbivory
Abstract Herbivory fundamentally shapes ecosystem
functioning by influencing the abundance and distribution
of plants. Whereas a great deal of attention has been given
to factors that influence rates of primary productivity (e.g.,
light, temperature and nutrients), considerably less attention
has been given to factors governing herbivory rates. In the
marine environment, urchins are a dominant herbivore on
rocky shores, and their grazing often leads to overconsump-
tion and the formation of “barren grounds” with few fleshy
macroalgae. However, despite decades of laboratory experi-
ments and field observations, there is still a high degree of
uncertainty with regard to the factors that control sea urchin
consumption rates. To synthesize current knowledge on
this subject, we compiled and analyzed data from the peer-
reviewed literature on consumption rates of the green urchin,
Strongylocentrotus droebachiensis, to examine the effects of
intrinsic (e.g., size) and extrinsic (e.g., temperature and algal
type) factors. Generally, urchins consumed 1.3–4.1% of their
body weight per day, though the range was much greater
(0.1–18%) when all measurements were included. Not sur-
prisingly, larger urchins ate more than smaller urchins, but
Responsible Editor: P. Kraufvelin.
Reviewed by undisclosed experts.
Electronic supplementary material The online version of this
article (doi:10.1007/s00227-017-3159-0) contains supplementary
material, which is available to authorized users.
* T. S. Suskiewicz
bluedepth@aol.com
1 Department of Biology and Québec-Océan, Université Laval,
Québec, QC G1W3B4, Canada
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Under oligotrophic or light-limiting conditions, decreased primary production and compensatory grazing by sea urchins (among other behavioural changes) both alter the production-consumption relationship, making macroalgal systems much more prone to catastrophic collapses than regions with higher nutrient availability (Dayton, 1985;Boada et al., 2017;Nikolaou et al., 2023). Non-lethal temperature increases can enhance primary production, but may also modify herbivore metabolic requirements, which affects the balance of these interactions (O'Connor, 2009;Pagès et al., 2018 Central to overgrazing vulnerability is the fundamental relationship between habitat productivity and herbivore consumption (Suskiewicz & Johnson, 2017). While many factors may shape the vulnerability of vegetated ecosystems to collapse (Hereu et al., 2008;Conversi et al., 2015), this production-consumption ratio most clearly describes how close a system is to overconsumption. ...
... While many factors may shape the vulnerability of vegetated ecosystems to collapse (Hereu et al., 2008;Conversi et al., 2015), this production-consumption ratio most clearly describes how close a system is to overconsumption. While several studies have explored how the production-consumption relationship is modified by endogenous or exogenous factors, most have tested these factors individually or in laboratory conditions (Suskiewicz & Johnson 2017;Kriegisch et al., 2019). Scaling these studies up to whole ecosystems is critical to determine context-specific vulnerabilities of macroalgal communities (Conversi et al., 2015;Wood et al., 2017). ...
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... Compared with previous estimates of Macrocystis consumption across a size range of E. chloroticus by Barker et al. (1998), we measured similar feeding rates in individuals 30-50 mm TD (0.49 vs. 0.58 g/day), but much higher rates in individuals >60 mm TD (2.48 vs. 1.08 g/day). Our measurements of nonlinear relationships between kelp consumption rates and E. chloroticus body size match descriptions in other urchin species (Roma et al., 2021;Stevenson et al., 2016;Suskiewicz & Johnson, 2017), likely underpinned by similar patterns in metabolic processes (Spindel et al., 2021). Notably, we detected a breakpoint in the relationship of bulk kelp consumption and urchin size at 49 mm TD (Figure 3a), which aligns neatly with the observed inflection point in our urchin length-weight relationships (Appendix S1: Figure S1) as well as the approximate size of emergence from a cryptic lifestyle and onset of gonadal development in E. chloroticus (Lamare & Mladenov, 2000;Shears & Babcock, 2002;Wing, 2009). ...
... In the presence of conspecifics, urchin feeding activity can be enhanced through the formation of feeding aggregations (Scheibling & Hamm, 1991), though the scaling of kelp consumption with density in the range used in our experiment (1-4 individuals/arena) may also be linear (Rennick et al., 2022). It is therefore plausible that density-driven inflation of kelp consumption rates measured in smaller urchin size classes caused the expression of an inverse-power curve between mass-specific feeding rates and TD, which has been measured as linear-decreasing or flat in other urchin species (Roma et al., 2021;Suskiewicz & Johnson, 2017). Predator-induced reductions in feeding activity of multiple urchins have also been shown to be smaller than in solitary individuals, either due to the formation of defensive aggregations on the surface of macroalgae or a general weakening of perceived risk (Knight et al., 2022;Scheibling & Hamm, 1991). ...
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... It is likely that the decline of overall grazing we see here is attributable to larger proportion of smaller size class and likely juvenile L. vincta in our second-year trials. In other marine herbivores, total kelp consumption is attributable to body size (Suskiewicz and Johnson 2017). Future research should make L. vincta size class a factor within each trial of each experiment, to quantify differences in snail preference that are directly attributable to size and age. ...
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... Feed consumption rates, particularly when broken down into constituents such as total carbon, ash-free dry weight (AFDW), and chlorophyll a (chl-a), can provide insights into biofilm biomass and composition required to sustain grazers. Consumption rates are influenced by a range of factors, including taxonomic grouping, grazer size, temperature, substrate type, feed source (biofilm, macroalgae, seagrass, periphyton), habitat (marine, fresh water, estuarine), sedimentation, intraspecific and interspecific competition, and current flow rate (Yee and Murray 2004; Cox and Murray 2006;Suskiewicz and Johnson 2017). Thus, feed consumption rates will only provide a general indication of nutritional requirements in terms of biofilm biomass and composition for grazer gastropods. ...
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... Sea urchins demonstrate physiological and dietary flexibility, whereby individuals can make metabolic and behavioral adjustments, or switch to alternative foods (e.g., drift algae, turfing algae, invertebrates, detritus) when preferred food is scarce (Ling andJohnson 2009, Suskiewicz andJohnson 2017). Temnopleurus toreumatics Caulerapa peltate mostly feeds on green seaweed and C.serulata Cymodocea serrulata Syringodium and seagrasses and isoetifolium (Saravanan 2022). ...
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... Conversely, Cárcamo (2015) showed the opposite, which emphasises the benefits of measuring both the size and mass of urchins. Urchin mass can be used to estimate diameter, and similarly, diameter can be used to estimate mass, with species-and possibly condition-specific equations derived from regression models (Balisco, 2015;Kawamata, 1997;Stuart, 1981;Suskiewicz & Johnson, 2017). ...
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... Differences in body size and body mass among macrograzers are important factors that influence their food consumption due to corresponding differences in energetic requirements and metabolic demands [42][43][44]. The mean diameter and wet weight of M. nudus and T. sazae did not significantly differ before and after the feeding assay or among temperatures before the assay. ...
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... Due to the importance of echinoderms in the coral communities (Uthicke et al., 2009;Suskiewicz and Johnson 2017) and the increased frequency of ENSO extremes under climate change, characterizing changes in their assemblages over space and time will be important.; the resulting assemblage changes could have widespread effects throughout the entire coral reef ecosystem. ...
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Knowledge of urchin age structure is crucial for understanding their ecosystem impacts and improving their management. In sclerochronology, translucent and opaque growth bands (TGB, OGB) in urchin ossicles are used to estimate age. An essential premise for using this technique is that one TGB and one OGB are formed every year, independent of urchin size or ossicle type. TGB and OGB addition are associated with slow and fast growth, respectively, and assumed to be added seasonally due to changes in water temperature. However, these assumptions are not unanimously supported by experiments, and validation attempts have not generated consensus. We conducted an experiment on Strongylocentrotus droebachiensis to test the validity of these assumptions and ed the literature to assess the use and validation of sclerochronology in urchins. The experiment demonstrated that the addition of TGB and OGB was not strictly related to temperature and was not consistent across urchin size-classes or ossicle types. TGB were added in response to temporary stress, and no distinction on the basis of band width or pigmentation could be made between natural TGB and stress-induced TGB. Only 52% of articles that used sclerochronology for aging urchins attempted any validation, and when the methodology was put under scrutiny, it was usually found to be wanting. More detailed studies are needed to address variability in growth bands deposition and endogenous and exogenous factors affecting this process. Sclerochronology in urchins should not be used until standardized procedures are able to provide accurate and precise interpretation of growth band addition. © 2016 Association for the Sciences of Limnology and Oceanography.
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Thermal and Hydrodynamic Environments Mediate Individual and Aggregative Feeding of a Functionally Important Omnivore in Reef Communities
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In eastern Canada, the destruction of kelp beds by dense aggregations (fronts) of the omnivorous green sea urchin, Strongylocentrotus droebachiensis, is a key determinant of the structure and dynamics of shallow reef communities. Recent studies suggest that hydrodynamic forces, but not sea temperature, determine the strength of urchin-kelp interactions, which deviates from the tenets of the metabolic theory of ecology (MTE). We tested the hypothesis that water temperature can predict short-term kelp bed destruction by S. droebachiensis in calm hydrodynamic environments. Specifically, we experimentally determined relationships among water temperature, body size, and individual feeding in the absence of waves, as well as among wave velocity, season, and aggregative feeding. We quantified variation in kelp-bed boundary dynamics, sea temperature, and wave height over three months at one subtidal site in Newfoundland to test the validity of thermal tipping ranges and regression equations derived from laboratory results. Consistent with the MTE, individual feeding during early summer (June-July) obeyed a non-linear, size- and temperature-dependent relationship: feeding in large urchins was consistently highest and positively correlated with temperature
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Herbivore impacts on two morphologically similar bloom-forming Ulva species in a eutrophic bay
Article
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  • Jul 2015
Herbivore impacts on macrophyte growth vary with the identity of the herbivores and macrophytes, as well as under different abiotic conditions. This interaction is further complicated by anthropogenic alterations to the environment, such as eutrophication. In this study, we utilized in situ herbivore exclusion experiments and mesocosm feeding preference assays to examine the impacts of different herbivores on the growth of two morphologically similar, co-occurring macroalgal bloom Ulva species in a nutrient-rich environment. We found that herbivory had a measurable impact on Ulva biomass, though the rate of consumption rarely surpassed growth for either Ulva species. We determined that the primary herbivores within the blooms were amphipods and mud crabs, and that their effects varied among study sites and months. Our results also confirmed that, even with a diverse suite of consumers, Ulva blooms are capable of escaping herbivore control, particularly early in the growing season when growth rates peak and herbivore activity is limited. Furthermore, our experiments revealed species-specific feeding preferences among herbivores, as well as differences in growth rates and chemistry between the two Ulva species, which likely influence bloom dynamics.
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Feeding Rates of Seals and Whales
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  • Feb 1987
(1) The hypothesis that rates of food consumption by marine mammals are similar to those of terrestrial mammals was tested by comparing rates of food consumption of non-growing and growing, juvenile and adult pinnipeds (Carnivora: Caniformia) and whales (Cetacea) to terrestrial Carnivora of known mass. (2) Daily maintenance rates of energy ingestion for adult pinnipeds were not significantly different from those of adult terrestrial carnivores but were about 28% lower than those of terrestrial carnivores with the mustelids excluded. Apparent differences in energy requirements of phocid and otariid seals appeared to result from differences in activity among the experimental animals available for comparison. Data on energy required by cetaceans for maintenance were not available. (3) Among pinnipeds, there was no significant difference in the rates of energy ingested by growing juvenile phocid seals and growing juvenile otariids. Growing juvenile phocids ingested about 1.38 times more energy than juvenile phocid seals at maintenance. The latter required about 1.40 times more energy for maintenance than adult phocids of similar size. (4) The rate of energy ingestion by growing juvenile pinnipeds was relatively higher than for the juvenile terrestrial carnivores sampled. This result appears to arise from differences in body masses and growth rates represented by the two samples rather than from any fundamental differences between juvenile pinnipeds and terrestrial carnivores. (5) Rate of biomass consumption, although frequently used as a measure of food consumption, is not particularly appropriate in comparative studies because it neglects differences in the energy content of food. Nonetheless, the 95% confidence region for rates of biomass ingestion in relation to body mass in marine mammals (seals and whales) included most of the estimates for biomass ingestion rates of terrestrial carnivores held in zoos, or estimated for mammals in the wild. Mean biomass ingestion rates for marine mammals were also similar to published relationships for terrestrial mammals. (6) The available data thus suggest that rates of food consumption by marine and terrestrial mammals are not significantly different when comparisons are made under appropriately standardized conditions.
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Global regime shift dynamics of catastrophic sea urchin overgrazing
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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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Experimental Investigations of Disturbance and Ecological Succession in a Rocky Intertidal Algal Community
Article
  • Sep 1979
Mechanisms of ecological succession were investigated by field experiments in a rocky intertidal algal community in southern California. The study site was algal-dominated boulder field in the low intertidal zone. The major form of natural disturbance which clears space in this system is the overturning of boulders by wave action. Algal populations recolonize cleared surfaces either through vegetative regrowth of surviving individuals or by recruitment from spores. Boulders which are experimentally cleared and concrete blocks are colonized within the first month by a mat of the green alga, Ulva. In the fall and winter of the first year after clearing, several species of perennial red algae including Gelidium coulteri, Gigartina leptorhynchos, Rhodoglossum affine, and Gigartina canaliculata colonize the surface. If there is no intervening disturbance, Gigartina canaliculata gradually dominates the community holding 60-90% of the cover after a period of 2 to 3 years. If undisturbed, this monoculture persists through vegetative reproduction, resisting invasion by all other species. During succession diversity increases initially as species colonize a bare surface but declines later as one species monopolizes the space. Several contemporary theories concerning the mechanisms of ecological succession were tested. The early successional alga, Ulva, was found to inhibit the recruitment of perennial red algae. This competition for settling space is an important feature of the successional process. Ulva is the best competitor for this space; it reproduces throughout the year and quickly becomes established on newly cleared substrates. As long as these early colonists remain healthy and undamaged, they preempt colonization by perennial red algae which have highly seasonal recruitment and slower growth. Selective grazing on Ulva by the crab, Pachygrapsus crassipes, breaks this inhibition and accelerates succession to a community of long-lived red algae. Grazing by small molluscs, especially limpets, has no long-term effect on the successional sequence. Their grazing temporarily enhances the recruitment of the barnacle, Chthamalus fissus, by clearing space in the mat of algal sporelings and diatoms which develops on recently denuded rock surfaces. Where locally abundant, middle successional red algae also slow the invasion and growth of the late successional dominant, Gigartina canaliculata. This alga replaces middle successional species because it is less susceptible to damage by desiccation and overgrowth by epiphytes. The results of this study do not support either the classical facilitation model or the tolerance (competitive) model of ecological succession. Once early colonists secure the available space/light, they resist rather than facilitate the invasion of subsequent colonists. Early colonists are not killed by direct interference competition with late successional species which grow up through their canopy; rather, early colonists can successfully inhibit the recruitment and growth of these species. Successional sequences occur because species which dominate early in a succession are more susceptible to the rigors of the physical environment and to attacks by natural enemies than late successional species. Late species colonize and grow to maturity when early species are killed and space is opened. Only late in a successional sequence, when large clearings become a mosaic of small openings, does direct competition with surrounding adult plants of late successional species contribute to the decline in cover of the remaining early species. Studies of succession in a number of terrestrial and marine communities lend support to this inhibition model.
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The pattern of Laminariales distribution in the northeast Pacific
Article
  • Dec 1970
The distribution of 40 species of Laminariales is described for the northeast Pacific coast from Santa Margarita Island, Baja California, Mexico to Attu Island, Alaska, U. S. A. In general this coast can be described as an area of gradual floristic change which can, however, be divided into seven broad transitional regions separated by regions of no floristic change. The relative distribution of Lessoniaceae, Alariaceae, and Laminariacea along the northeast pacific coast defines three distinct coastal floras: a southern segment from Santa Margarita Island to the Strait of Juan de Fuca; a northern segment from Hope Island, British Columbia, Canada, to Yakutat, Alaska; and a western segment from Kodiak Island, Alaska to Attu Island, Alaska.
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