Rocky Intertidal Communities Research Articles

Setting conservation management thresholds using a novel participatory modeling approach.

We devised a participatory modeling approach for setting management thresholds that show when management intervention is required to address undesirable ecosystem changes. This approach was designed to be used when management thresholds: must be set for environmental indicators in the face of multiple competing objectives; need to incorporate scientific understanding and value judgments; and will be set by participants with limited modeling experience. We applied our approach to a case study where management thresholds were set for a mat-forming brown alga, Hormosira banksii, in a protected area management context. Participants, including management staff and scientists, were involved in a workshop to test the approach, and set management thresholds to address the threat of trampling by visitors to an intertidal rocky reef. The approach involved trading off the environmental objective, to maintain the condition of intertidal reef communities, with social and economic objectives to ensure management intervention was cost-effective. Ecological scenarios, developed using scenario planning, were a key feature that provided the foundation for where to set management thresholds. The scenarios developed represented declines in percent cover of H. banksii that may occur under increased threatening processes. Participants defined 4 discrete management alternatives to address the threat of trampling and estimated the effect of these alternatives on the objectives under each ecological scenario. A weighted additive model was used to aggregate participants' consequence estimates. Model outputs (decision scores) clearly expressed uncertainty, which can be considered by decision makers and used to inform where to set management thresholds. This approach encourages a proactive form of conservation, where management thresholds and associated actions are defined a priori for ecological indicators, rather than reacting to unexpected ecosystem changes in the future.

Are meta‐ecosystems organized hierarchically? A model and test in rocky intertidal habitats

Ecosystems are shaped by processes occurring and interacting over multiple temporal and spatial scales. Theory suggests such complexity can be simplified by focusing on processes sharing the same scale as the pattern of interest. This scale‐dependent approach to studying communities has been challenged by multiscale meta‐ecosystem theory, which recognizes that systems are interconnected by the movement of “ecological subsidies” and suggests that cross‐scale feedbacks between local and regional processes can be equally important for understanding community structure. We reconcile these two perspectives by developing and testing a hierarchical meta‐ecosystem model. The model predicts local community responses to connectivity over multiple oceanographic spatial scales, defined as macro‐ (100s of km), meso‐ (10s of km), and local scale (100s of m). It assumes that local communities occur in distinct regions and that connectivity effects are strongest among local sites. Predictions are that if macroscale processes dominate, then regardless of mesoscale differences, (1) local communities will be similar, and (2) will be even more so with increased connectivity. With dominance of mesoscale (i.e., regional) processes, (3) local structure will be similar within but distinct between regions, and (4) with increased connectivity similar both within and among regions. With dominance of local‐scale processes, (5) local communities will differ both within and among regions, and (6) with increased connectivity be similar within but not between regions. We tested the model by evaluating rocky intertidal community structure patterns with variation in ecological subsidies and environmental conditions at 13 sites spanning 725 km of the northern California Current system. External factors operating at meso‐ and local scales had strong effects, explaining 52% and 27% of the variance, respectively, in community structure. Sessile invertebrate and predator dominance was associated with weaker upwelling, higher phytoplankton abundance, and higher recruitment, and the opposite was true for macrophyte dominance. Overall, our results support the theory that meta‐ecosystems are organized hierarchically, with environmental processes dominating at meso‐ to macroscales and ecological processes playing a more important role at local scales, but with important bidirectional cross‐scale interactions.

Phylogeographic structure and northward range expansion in the barnacle Chthamalus fragilis.

The barnacle Chthamalus fragilis is found along the US Atlantic seaboard historically from the Chesapeake Bay southward, and in the Gulf of Mexico. It appeared in New England circa 1900 coincident with warming temperatures, and is now a conspicuous member of rocky intertidal communities extending through the northern shore of Cape Cod, Massachusetts. The origin of northern C. fragilis is debated. It may have spread to New England from the northern end of its historic range through larval transport by ocean currents, possibly mediated by the construction of piers, marinas, and other anthropogenic structures that provided new hard substrate habitat. Alternatively, it may have been introduced by fouling on ships originating farther south in its historic distribution. Here we examine mitochondrial cytochrome c oxidase I sequence diversity and the distribution of mitochondrial haplotypes of C. fragilis from 11 localities ranging from Cape Cod, to Tampa Bay, Florida. We found significant genetic structure between northern and southern populations. Phylogenetic analysis revealed three well-supported reciprocally monophyletic haplogroups, including one haplogroup that is restricted to New England and Virginia populations. While the distances between clades do not suggest cryptic speciation, selection and dispersal barriers may be driving the observed structure. Our data are consistent with an expansion of C. fragilis from the northern end of its mid-19th century range into Massachusetts.

Species fluctuations sustained by a cyclic succession at the edge of chaos

Although mathematical models and laboratory experiments have shown that species interactions can generate chaos, field evidence of chaos in natural ecosystems is rare. We report on a pristine rocky intertidal community located in one of the world's oldest marine reserves that has displayed a complex cyclic succession for more than 20 y. Bare rock was colonized by barnacles and crustose algae, they were overgrown by mussels, and the subsequent detachment of the mussels returned bare rock again. These processes generated irregular species fluctuations, such that the species coexisted over many generations without ever approaching a stable equilibrium state. Analysis of the species fluctuations revealed a dominant periodicity of about 2 y, a global Lyapunov exponent statistically indistinguishable from zero, and local Lyapunov exponents that alternated systematically between negative and positive values. This pattern indicates that the community moved back and forth between stabilizing and chaotic dynamics during the cyclic succession. The results are supported by a patch-occupancy model predicting similar patterns when the species interactions were exposed to seasonal variation. Our findings show that natural ecosystems can sustain continued changes in species abundances and that seasonal forcing may push these nonequilibrium dynamics to the edge of chaos.

Saxitoxin and the Ochre Sea Star: Molecule of Keystone Significance and a Classic Keystone Species.

Saxitoxins (STXs) are paralytic alkaloids produced by marine dinoflagellates in response to biotic and abiotic stressors yielding harmful algal blooms. Because STX impacts coastal, near-shore communities to a greater extent than would be predicted by its relative abundance, it has been referred to as a "molecule of keystone significance" in reference to Robert Paine's Keystone Species Concept. Pisaster ochraceus, the predator upon which Paine's concept was founded, inhabits waters regularly plagued by harmful algal blooms, but the effects of STX on Pisaster have not yet been investigated. Here, we used laboratory and field experiments to examine the potential consequences of exposure to STX on sea stars' feeding, attachment to the substrate, and success in fertilization. Pisaster exhibited similar feeding behaviors when offered non-toxic prey, STX-containing prey, or a combination of the two. Although feeding behavior is unaffected, consumption of STX poses a physiological tradeoff. Sea stars in the laboratory and field had significantly lower thresholds of the force needed to detach them from their substrates after either being exposed to, or consuming, STX. High pressure (or high performance) liquid chromatography analysis indicated an accumulation of STX (and structural analogues) in sea stars' viscera, likely due to trophic transfer from toxic prey. Incidence of fertilization tended to decrease when gametes were exposed to high, yet ecologically relevant, STX concentrations of STX. These findings suggest that the molecule of keystone significance, STX, produced during harmful algal blooms extends its impacts to rocky intertidal communities by way of the keystone predator P. ochraceus.

Biogeographical patterns of rocky shore community structure in south‐east Australia: effects of oceanographic conditions and heat stress

AbstractAimEnvironmental variability can be a major driver of large‐scale patterns of distribution and abundance and, within the marine environment, benthic community structure is usually thought to reflect several oceanographic processes and coastal morphological features. The aim of this study was to quantify spatial and temporal variability in large‐scale rocky intertidal community structure along the south‐east coast of Australia and ask whether these are associated with variation in sea‐surface temperatures, chlorophyll‐a concentration, heat stress and coastal geomorphology.LocationRocky intertidal shores of south‐east Australia spanning > 1750 km, 13° of latitude (26°24′23″ S to 39°07′47″ S) and known biogeographical barriers.MethodsFrom 2009 to 2011 one‐thousand and twenty photoquadrats located within the midshore region of 17 rocky shores (20 quadrats site−1 year−1) were used to estimate spatial and temporal variability in the percentage cover of dominant benthic invertebrates and macroalgae. We used satellite data to generate annual estimates of nearshore sea‐surface temperatures (SST) and chlorophyll‐a concentrations ([Chl‐a]) and a meteorological model to estimate heat stress during summer low‐tides.ResultsNon‐metric multidimensional scaling and cluster analysis revealed a strong and consistent biogeographical break in rocky intertidal community structure between southern and eastern sites. Nearshore oceanographic conditions and summer heat stress did not appear to influence this discontinuity as abundances of functional groups (filter‐feeders, grazers and macroalgae) generally did not vary in response to geographical patterns of SST, [Chl‐a] or mean daily maximum air temperatures during low‐tide. At the species level, however, the distribution and abundance of several species varied with nearshore SST and [Chl‐a] including the barnacle Tesseropora rosea and limpets within the genus Patelloida, respectively.Main conclusionsWe found no evidence of strong bottom‐up effects on rocky intertidal functional group abundance. This was somewhat expected because bottom‐up effects in regions characterized by persistent downwelling are generally weak or non‐existent. Instead, broad‐scale patterns of community composition were best explained by coastal geomorphology. This study provides an important and necessary comparison for the role of broad‐scale environmental variability in structuring marine benthic communities within downwelling rather the more commonly reported upwelling systems.

Network structure beyond food webs: mapping non-trophic and trophic interactions on Chilean rocky shores.

How multiple types of non-trophic interactions map onto trophic networks in real communities remains largely unknown. We present the first effort, to our knowledge, describing a comprehensive ecological network that includes all known trophic and diverse non-trophic links among >100 coexisting species for the marine rocky intertidal community of the central Chilean coast. Our results suggest that non-trophic interactions exhibit highly nonrandom structures both alone and with respect to food web structure. The occurrence of different types of interactions, relative to all possible links, was well predicted by trophic structure and simple traits of the source and target species. In this community, competition for space and positive interactions related to habitat/refuge provisioning by sessile and/or basal species were by far the most abundant non-trophic interactions. If these patterns are orroborated in other ecosystems, they may suggest potentially important dynamic constraints on the combined architecture of trophic and non-trophic interactions. The nonrandom patterning of non-trophic interactions suggests a path forward for developing a more comprehensive ecological network theory to predict the functioning and resilience of ecological communities.

Broad‐scale geographic variation in the organization of rocky intertidal communities in the Gulf of Maine

A major challenge facing ecology is to better understand how large‐scale processes modify local‐scale processes to shape the organization of ecological communities. Although the results of ecological experiments are repeatable on local scales, different results often emerge across broad scales, which can hinder the development of general predictions that apply across the geographical range of a community. Numerous studies in the southern Gulf of Maine have shaped our understanding of community organization and dynamics on New England rocky intertidal shores, where consumers strongly control recovery from disturbance on sheltered shores, and high invertebrate recruitment and competition for space dictate recovery on wave‐exposed shores. It is unclear, however, whether the effects of consumers and recruitment variation on resulting community organization in this region apply more broadly to rocky intertidal habitats throughout the Gulf.We characterized variation in rocky intertidal community structure at 34 sites throughout the Gulf of Maine and experimentally examined the influence of consumers (present, absent) and wave energy (wave‐exposed, sheltered) on community recovery from disturbance in the northern and southern Gulf. Our results reinforced previous work in the southern Gulf, because consumers dictated the recovery of fucoid algae and mussels on sheltered shores, whereas high barnacle and mussel recruitment and competition for space shaped recovery on wave‐exposed shores. However, on sheltered shores in the northern Gulf, neither consumers nor barnacle and mussel recruitment impacted recovery, which was dominated by fucoid algae. Moreover, recovery on wave‐exposed shores in the northern Gulf was quite distinct from that observed in the southern Gulf; barnacle and mussel recruitment was negligible and fucoid algae dominated recovery, including the long‐term establishment of Ascophyllum nodosum, which is largely absent from wave‐exposed shores in the southern Gulf. Thus, distinct community types emerged in the northern and southern Gulf despite their sharing of many of the same species. These patterns likely emerged because of regional differences in coastal oceanography that modulate the recruitment of barnacles and mussels. Hence, increased attention to regional factors should provide key insight into how rocky‐shore communities are organized in the Gulf of Maine and elsewhere.

Not all space is created equal: Distribution of free space and its influence on heat-stress and the limpet Patelloida latistrigata

For most marine benthic communities unoccupied primary substrata, or free space, is considered the principle limiting resource. Substratum temperatures, desiccation rates and hydrodynamic characteristics of free space, however, may vary depending on patch size and isolation and therefore potentially influence biotic processes. This paper investigates the relationship between small-scale changes in the availability and configuration of free space, heat stress and abundance of the small rocky intertidal gastropod Patelloida latistrigata within southeastern Australia. Using infrared thermography I show that heat stress of rocky intertidal communities increased linearly with increasing amounts of free space on three neighbouring shores during four separate sampling intervals from October 2009 to January 2010. Abundances of P. latistrigata generally declined with increasing availability of free space and the associated increases in heat stress. An experimental manipulation that altered the configuration but not the availability of free space demonstrated that both heat stress and P. latistrigata abundance are not affected by small-scale changes in the configuration of free space. The small-scale distribution of P. latistrigata, however, was significantly influenced by differences in the configuration of free space with limpets displaying bimodal distributions within areas characterised by unevenly distributed free space. Since the distribution of Patelloida varies depending on the configuration of free space but thermal properties at the scale of individual limpets do not then we might expect Patelloida to be responding to changes in other abiotic factors, such as hydrodynamic forces and desiccation rates, which may change with the configuration of free space. This study highlights the dynamic and usually unexamined relationship between abiotic stress and the availability and acquisition of resources by marine benthic invertebrates.

Oceanographic and climatic variation drive top‐down/bottom‐up coupling in the Galápagos intertidal meta‐ecosystem

The impact of herbivores on primary producers in differing oceanographic regimes is a matter of intense ecological interest due to ongoing changes in their abundance, that of their predators, and anthropomorphic alteration of nutrient cycles and climatic patterns. Interactions between productivity and herbivory in marine habitats have been studied on temperate rocky shores, coral reefs, mangroves, and salt marshes, but less so at tropical latitudes. To determine how herbivore–alga dynamics varied with oceanographic regime, we used the comparative‐experimental approach in rocky intertidal communities on the Galápagos Islands from January 2006 to January 2009. This setting was selected because strongly contrasting oceanographic conditions occurred within a range of ∼181 km, with significant differences in temperature, nutrients, phytoplankton productivity, and intertidal communities, and in abundance of macro‐herbivores, including marine iguanas. Experiments and measurements were conducted at two sites in each of three oceanographic regimes characterized by low, intermediate, and high bottom‐up inputs. At sites of low inputs, macro‐herbivores (fish, crabs, iguanas) had a consistent top‐down effect, reducing algal abundance, and leaving a few grazer‐resistant varieties. At sites of intermediate and high inputs, consumer impacts were stronger during La Niña (cool phase) than during El Niño (warm phase). At sites of high inputs, algal biomass was naturally relatively high and was dominated by the edible algae Ulva spp. Macro‐grazers reduced algal biomass, but their primary effect was indirect, as articulated corallines displaced other species of algae in their absence. Prior results from the tropics had revealed dominant effects of top‐down interactions and recruitment in structuring intertidal communities. Our results suggest that, when a broader oceanographic scenario is taken into account, the relative importance of top‐down and bottom‐up forces are context dependent, varying with oceanographic regime and climatic variability.

Visual record of intertidal disturbance caused by drift ice in the spring on the Atlantic coast of Nova Scotia.

In the early spring of 2014, an unusually large amount of sea ice drifted from the Gulf of St. Lawrence, where it had been produced, towards the open Atlantic Ocean through the Cabot Strait, between Nova Scotia and Newfoundland, Canada. In early April, significant amounts of drift ice reached the Atlantic coast of mainland Nova Scotia. The ice floes persisted in those coastal waters for up to 16 days, depending on the location. During that time, the ice fragments caused extensive physical disturbance in rocky intertidal communities, removing high quantities of seaweeds and invertebrates. For example, at a location where the ice stayed for 9 days, the loss of macroalgal and invertebrate biomass was almost total. At a location where the ice stayed for 4 days, losses were lower, albeit still high overall. Such a magnitude of disturbance is not common on this coast, as sea ice had not reached the surveyed locations in the previous 4-5 years. We suggest that the frequency of ice scour events may help to predict intertidal community structure. This notion could be tested through multiannual surveys of ice conditions and biological communities along the Atlantic coast of Nova Scotia.

Visual record of intertidal disturbance caused by drift ice in the spring on the Atlantic coast of Nova Scotia

In the early spring of 2014, an unusually large amount of sea ice drifted from the Gulf of St. Lawrence, where it had been produced, towards the open Atlantic Ocean through the Cabot Strait, between Nova Scotia and Newfoundland, Canada. In early April, significant amounts of drift ice reached the Atlantic coast of mainland Nova Scotia. The ice floes persisted in those coastal waters for up to 16 days, depending on the location. During that time, the ice fragments caused extensive physical disturbance in rocky intertidal communities, removing high quantities of seaweeds and invertebrates. For example, at a location where the ice stayed for 9 days, the loss of macroalgal and invertebrate biomass was almost total. At a location where the ice stayed for 4 days, losses were lower, albeit still high overall. Such a magnitude of disturbance is not common on this coast, as sea ice had not reached the surveyed locations in the previous 4–5 years. We suggest that the frequency of ice scour events may help to predict intertidal community structure. This notion could be tested through multiannual surveys of ice conditions and biological communities along the Atlantic coast of Nova Scotia.

Estimating latitudinal variability in extreme heat stress on rocky intertidal shores

AbstractAimBroad‐scale patterns of heat stress play an important role in shaping the geographical distributions of many species and may differ from large‐scale changes in average temperatures. For species living on rocky intertidal shores extreme heat stress occurs when hot dry aerial conditions coincide with midday low tides. We used empirical and modelled temperature data, and estimates of cumulative aerial exposure and solar radiation, in order to test the hypothesis that heat stress on Australian rocky intertidal shores decreases with increasing latitude.LocationRocky intertidal shores of south‐eastern Australia spanning > 1500 km and 13° of latitude (26°24′23″ S to 39°07′47″ S).MethodsIn situ temperature measurements, hourly tidal elevations and daily solar radiation taken over three consecutive summers (December 2009–February 2012) were used to quantify latitudinal variability in extreme heat stress, cumulative aerial exposure and solar radiation, respectively. Comparisons between hourly in situ temperatures and meteorological data were used to produce a large‐scale statistical model capable of estimating intertidal substratum temperatures during daytime low‐tides, which was then extrapolated across 22 locations.ResultsHeat stress estimated using in situ loggers deployed across five east coast locations typically did not decline with increasing latitude and neither did midday exposure or solar radiation. The meteorological model proved to be a successful method for estimating rocky shore heat stress and in contrast to the empirical data displayed strong latitudinal trends in mean daily maxima and cumulative heat stress. Modelled acute heat stress (i.e. summer maxima), however, did not decline with increasing latitude, as there was greater thermal variability at higher latitudes.Main conclusionsThe meteorological model developed in this study represents a useful approach for estimating broad‐scale patterns of heat stress on rocky intertidal shores. Results also indicate that latitudinal patterns of acute and chronic heat stress may differ from average temperatures, which are commonly assumed to decline with increasing latitude. Such broad‐scale patterns of thermal stress as described in this study will significantly contribute to our ability to understand the impact of climate change on vulnerable rocky intertidal communities.

Effects of intensity and seasonal timing of disturbances on a rocky intertidal benthic community on the southern coast of Korea

AbstractThe effects of intensity and timing of disturbances on recovery of marine benthic organisms were investigated on a rocky intertidal shore in Gwangyang Bay, Korea. We hypothesized that the recovery pattern of the benthic community structure would be affected by disturbance intensity and season. Twenty‐eight permanent plots were set up, with disturbance intensity (cleared plots and sterile plots) and seasonal disturbance (fall 1999 and spring 2000) incorporated into the experimental design. To monitor natural seasonal variation in benthic community abundances, we established seven permanent unmanipulated plots. Turf‐forming algae were observed in the unmanipulated plots throughout the experimental period, whereas green algae and invertebrate presence varied with season. In the disturbance‐intensity experiment, turf‐forming and green algae were dominant in cleared plots. The highest coverage of sessile organisms was observed in sterile plots, which exhibited the highest species richness because of their relatively low macroalgal coverage. Seasonal effects of disturbance were an important factor in the recovery pattern of benthic organisms under high disturbance intensity. Coverage of green algae was higher in sterile spring plots than in sterile fall plots; this result was attributed to low spatial competition, as the disturbances occurred just before green algal blooms. On the other hand, the abundances of barnacles and bivalves were highest on sterile fall plots, as these organisms were suppressed by green algal blooms in other periods. These results indicate that the effects of disturbance intensity on benthic community recovery patterns can be influenced by season of disturbance.

Impact of Predation by the Invasive CrabHemigrapsus sanguineuson Survival of Juvenile Blue Mussels in Western Long Island Sound

Hemigrapsus sanguineus (Asian Shore Crab) has shown a remarkable ability to colonize rocky intertidal communities along the east coast of the United States since its introduction in the late 1980s and is an important predator of juvenile Mytilus edulis (Blue Mussel) in invaded habitats. In this study, we used two field-caging experiments and the Kaplan-Meier model to assess the impact of predation by Asian Shore Crab on the survival of juvenile Blue Mussels in an intertidal habitat of western Long Island Sound along the Connecticut coastline. Five treatment levels (high-density enclosure, low-density enclosure, exclosure, partial cage, and open plot) were used in the 2007 experiment. The high-density enclosure treatment was omitted in the 2010 experiment since there was no statistically significant difference in the proportion of mussels surviving between low- and high-density crab treatments in 2007. In 2007, we measured a statistically significant difference in mussel mortality between exclosure and crab-enclosure cages, with crabs lowering the median survival time for mussels from 15.4 to 7.6 days. In 2010, we again measured a statistically significant difference in mussel mortality between exclosure and crab-enclosure cages, suggesting a crab effect on mussel survival. In the 2010 experiment, approximately 25% of the mussel mortality was attributable to crab predation, which reduced median survival time for mussels from 12.8 to 5.6 days. The median survival time for mussels exposed to the full complement of factors affecting survival (open plots and partial cages) was only 2–3 days. Our study shows that predation by Asian crabs may account for up to 25% of the Blue Mussel mortality in the intertidal zone at Black Rock Harbor. Further studies focusing on the importance of other biotic and abiotic factors are needed to understand the apparent declines in Blue Mussel populations and the interannual variability in recruitment success in this area.

Habitat modification in tidepools by bioeroding sea urchins and implications for fine‐scale community structure

AbstractBy creating novel habitats, habitat‐modifying species can alter patterns of diversity and abundance in marine communities. Many sea urchins are important habitat modifiers in tropical and temperate systems. By eroding rocky substrata, urchins can create a mosaic of urchin‐sized cavities or pits separated by exposed, often flat surfaces. These microhabitats appear to harbor distinct assemblages of species. We investigated how a temperate rocky intertidal community uses three small‐scale (<100 cm2) microhabitats created by or adjacent to populations of the purple sea urchin (Strongylocentrotus purpuratus): pits occupied by urchins, unoccupied pits, and adjacent flat spaces. In tidepools, flat spaces harbored the highest percent cover of algae and sessile fauna, followed by empty pits and then occupied pits. The Shannon diversity and richness of these sessile taxa were significantly higher in flat spaces and empty pits than in occupied pits. The composition of these primary space holders in the microhabitats also varied. Unlike primary space holders, mobile fauna exhibited higher diversity and richness in empty pits than in flat spaces and occupied pits, although results were not significant. The protective empty pit microhabitat harbored the highest densities of most trophic functional groups. Herbivores, however, were densest in flat spaces, concordant with high algal coverage. These results suggest the habitats created by S. purpuratus in addition to its biological activities alter community structure at spatial scales finer than those typically considered for sea urchins.

Status and Trends of the Rocky Intertidal Community on the Farallon Islands

The Farallon Islands in the Gulf of the Farallones National Marine Sanctuary (GFNMS) is a 7-island chain located 48 km west of San Francisco, California. Since 1993, GFNMS biologists and associates have monitored algal and invertebrate species abundances on the intertidal shores of the 2 South Farallon Islands. The monitoring occurred 1–3 times yearly in 6 study areas. In each study area, 3–4 permanent, 0.15-m2 quadrats located between the upper and midintertidal zones were sampled for algal and sessile invertebrate cover and invertebrate counts. Taxonomic surveys were also completed to document other species in the vicinity of the sampling quadrats and to further characterize the sampling areas. Here we report monitoring results for the period 1993 to 2011. While species richness has remained relatively stable and high compared to the nearest mainland sites (Sonoma County through San Mateo County), there has been a slow, long-term net decline in the abundance of algal species and mussels at various sites on the islands. Causes for the declines remain unknown, but increased trampling from rising numbers of pinnipeds and increased waste from pinnipeds and seabirds are among the influences suspected to be important.

Role of predation on sandy beaches: Predation pressure and prey selectivity estimated by laboratory experiments

Predation is known to play an important role in structuring communities. In rocky intertidal communities, both environmental variables and the structuring role of predation determine species zonation and distribution patterns. However, on intertidal sandy beaches, little is known on the presence and the role of predation. In this study, laboratory experiments were used to examine prey consumption, prey selectivity and predation pressure of the two main epibenthic predators, being shrimp and juvenile flatfish, present on the intertidal beach at high tide. Results show that macrobenthos is important in the diet of these epibenthic predators and that prey selectivity is present. As predation pressure on the intertidal beach is high, predation is probably an important structuring factor for the sandy beach macrobenthos community. Hence, the macrobenthos zonation pattern is likely to be steered by the combination of abiotic and biotic factors: while the upper limit of a species zone is defined by the species physiological response to abiotic environmental variables, the lower limit is defined by biotic factors such as predation pressure. Furthermore, the intertidal zone functions as an important nursery area for commercially important species like shrimp and flatfish.

Bottom-up control of temperate rocky intertidal community structure: evidence from a transplant experiment

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 491:137-151 (2013) - DOI: https://doi.org/10.3354/meps10456 Bottom-up control of temperate rocky intertidal community structure: evidence from a transplant experiment Jonathan P. A. Gardner* Centre for Marine Environmental and Economic Research, School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand *Email: jonathan.gardner@vuw.ac.nz ABSTRACT: Transplantation of mussels Mytilus galloprovincialis to Wellington Harbour and Cook Strait (central New Zealand) was carried out to test for bottom-up control (food limitation) of intertidal community structure and scarcity of mussels. Analysis of water-column variables revealed that mean turbidity and chlorophyll a concentrations were 3 and 10 times higher, respectively, in Wellington Harbour than in Cook Strait. The responses of transplanted mussels reflected the water-column properties: mortality of Wellington Harbour mussels was very low whereas mortality of Cook Strait mussels was significantly greater, and all components of shell growth and soft tissue condition were higher for Wellington Harbour than Cook Strait mussels. These results are consistent with bottom-up control of mussel abundance, as mediated by feeding activity, body condition and energy balance. The results demonstrate how pronounced differences in localised coastal conditions may influence temperate rocky intertidal community structure on spatial scales of hundreds of metres, and how this influence may explain differences in community composition on spatial scales of many kilometres. KEY WORDS: Mytilus galloprovincialis · Food limitation · Bottom-up control · Coastal processes · Growth · Condition index · Mortality Full text in pdf format PreviousNextCite this article as: Gardner JPA (2013) Bottom-up control of temperate rocky intertidal community structure: evidence from a transplant experiment. Mar Ecol Prog Ser 491:137-151. https://doi.org/10.3354/meps10456 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 491. Online publication date: October 02, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Reddened seascapes: experimentally induced shifts in 1/f spectra of spatial variability in rocky intertidal assemblages.

Ecological tests of 1/f-noise models have advanced our understanding of how environmental fluctuations affect population abundance and species distributions. Most empirical studies have been conducted under controlled laboratory conditions and have focused on individual drivers. We present the results of a four-year field experiment in which canopy presence/absence and the availability of primary space were manipulated as red-noise and white-noise spatial processes, respectively, to evaluate their separate and compounded effects on algal turf distribution in a rocky intertidal community. Algal turfs closely tracked spatial variation in canopy distribution, displaying a reddened spectrum of spatial variation. Surprisingly, white-noise clearings also induced a red-shift in turf distribution, a pattern that was related to a nonlinear relation between gap size and turf colonization. The two disturbances interacted antagonistically, dampening the red-shift of turf distribution. Our results provide evidence of experimentally induced shifts in the spectrum of a spatial variable under natural environmental conditions.