Intertidal Animals Research Articles

Differential effects of native and invasive algal wrack on macrofaunal assemblages inhabiting exposed sandy beaches

Many sandy beaches worldwide receive large amounts of drift seaweed, known as wrack, from offshore algal beds and closer rocky intertidal shores. Despite the important influence of algal wrack on macrofaunal assemblages from different coastal systems, relatively little attention has been paid to the macrofaunal responses in sandy beaches to macrophyte wrack supplies. Algal wrack is a key resource, i.e . for food and/or refuge, for beach invertebrates while its availability can affect diversity and abundance of intertidal animals including shorebirds, but the role of certain types of wrack and its location on the shore has not been examined experimentally to date. In this paper, we use experimental manipulation of two species of brown seaweeds, i.e. artificial wrack patches made up of the native macroalgae Saccorhiza polyschides and the invasive species Sargassum muticum, to test hypotheses about influences on macrofaunal assemblages inhabiting the drift line and supratidal levels of exposed beaches. Results pointed out that different types of wrack deposits were not used uniformly by invertebrates. Nutritional value differed between the two species of wrack. In most cases, the carbohydrates, lipids and organic carbon content were greater in patches of S. muticum than in patches of S. polyschides. Data also provided evidences that nutritional content and microclimatic conditions of wrack deposits, i.e. temperature and humidity, might affect macrofaunal assemblages.

Computer simulations of high shore littorinids predict small-scale spatial and temporal distribution patterns on rocky shores

High shore littorinid snails exhibit complex spatial distribution patterns, forming dense aggregations both in crevices and on crevice-free sections of rocky shores. To understand how these patterns may form, an individual-based computer simulation of littorinid behaviour, similar to those used to model social insects, was used to mimic snail movement on rocky shores. Individual littorinid movement patterns were simulated, along with chance interactions with other littorinids, their trails, crevices and any resultant decisions made by the littorinids when these interactions occurred. The simulation investigated how simple behavioural rules can predict spatial aggregation patterns and the persistence and variation of these aggregation patterns over timescales of several tidal cycles. Morisita’s index of dispersal showed good agreement between the simulation and observed patterns of littorinids on-shore. Trail-following was vital in the simulation, since points where trails intersected with crevices, or points where 2 or more trails met, formed the site of aggregations. Both in the simulation and in reality, aggregations often occurred in identical positions over several tidal cycles, both within and outside crevices. This temporal predictability may be due to the persistence of mucus trails on the shore over successive tidal cycles. Removal of the influence of past mucus trails from the simulation resulted in far lower persistence of aggregations over time. The simulation, therefore, is an important tool in examining behavioural mechanisms of intertidal animals. It provides insights into how simple behaviour of grazing animals can explain complex population patterns and subsequently the community dynamics of algal-herbivore interactions.

Climate change, parasitism and the structure of intertidal ecosystems

Evidence is accumulating rapidly showing that temperature and other climatic variables are driving many ecological processes. At the same time, recent research has highlighted the role of parasitism in the dynamics of animal populations and the structure of animal communities. Here, the likely interactions between climate change and parasitism are discussed in the context of intertidal ecosystems. Firstly, using the soft-sediment intertidal communities of Otago Harbour, New Zealand, as a case study, parasites are shown to be ubiquitous components of intertidal communities, found in practically all major animal species in the system. With the help of specific examples from Otago Harbour, it is demonstrated that parasites can regulate host population density, influence the diversity of the entire benthic community, and affect the structure of the intertidal food web. Secondly, we document the extreme sensitivity of cercarial production in parasitic trematodes to increases in temperature, and discuss how global warming could lead to enhanced trematode infections. Thirdly, the results of a simulation model are used to argue that parasite-mediated local extinctions of intertidal animals are a likely outcome of global warming. Specifically, the model predicts that following a temperature increase of less than 4 degrees C, populations of the amphipod Corophium volutator, a hugely abundant tube-building amphipod on the mudflats of the Danish Wadden Sea, are likely to crash repeatedly due to mortality induced by microphallid trematodes. The available evidence indicates that climate-mediated changes in local parasite abundance will have significant repercussions for intertidal ecosystems. On the bright side, the marked effects of even slight increases in temperature on cercarial production in trematodes could form the basis for monitoring programmes, with these sensitive parasites providing early warning signals of the environmental impacts of global warming.

Molluscs and echinoderms under boulders: Tests of generality of patterns of occurrence

Quantifying and understanding the spatial patterns of variation in diversity and abundances of intertidal animals is receiving increased attention because causal models must focus on the scales at which individual organisms interact. Intertidal boulders are complex and naturally fragmented habitats and many species on boulders are absent from the matrix on which boulders lie and which separates individual boulders. This study builds on quantified observations of molluscs and echinoderms living underneath boulders in a sheltered boulder-field in New South Wales, Australia, which documented that, at the same tidal height, most of the variation in these fauna was at the scale of individual boulders, or between replicate sites only 20 m apart. Here, six specific models and hypotheses about spatial and temporal variability arising from that study were tested in 4 boulder-fields along 200 km of coast. Most variation was at the scale of individual boulders and between sites within boulder-fields, with some sites having similar fauna to sites in other boulder-fields and sites in the same boulder-fields having very different fauna. Although individual taxa were very variable in abundance, measures of the assemblages remained relatively consistent through time. Both rare and abundant species were extremely overdispersed, only being found on a minority of boulders and with very large abundances on some of these. The degree of overdispersion varied among boulder-fields for some taxa and not others, but there was no generality of patterns for a range of taxa in the same boulder-field, nor for individual taxa in different locations. Nevertheless, over 95% of the 1200 boulders sampled were occupied by at least one species. These extreme patterns of partitioning of habitat are discussed briefly in terms of managing these complex habitats.

Impacts by heavy-oil spill from the Russian tanker Nakhodka on intertidal ecosystems: recovery of animal community

The impact of a heavy-oil spill from the Nakhodka on an intertidal animal community, and the recovery process of animals from the damage were surveyed from the autumn of 1997 to the spring of 2001. The field study was carried out in the rocky coast of Imago-Ura Cove, located along the Sea of Japan, where clean-up operations for oil pollution had been conducted less intensely than in other polluted areas. We have examined individual number of each animal taxon by continuously placing a quadrat of 5 m width along the entire intertidal zone of the cove. A total of 76 invertebrate taxa including 57 species of mollusks, 10 species of crustaceans were observed during the survey. The number of taxa increased from 1998 to 1999 in areas where the initial oil pollution was intense. Total individual number of benthic animals continued to increase from 1998 to 2000 in the polluted areas. The impact of oil on benthic animals was different from species to species. Some species such as Cellana toreuma and Monodonta labio confusa increased rapidly after the oil spill, whereas other species such as Patelloida saccharina lanx and Septifer virgatus did not show any apparent temporal tendencies. Population size structure of P. saccharina lanx varied greatly among years, however that of M. labio confusa did not. For P. saccharina lanx, recruitment was unsuccessful in 1997, possibly due to the effect of oil pollution. These differences in responses to oil pollution among benthic animals are considered to be caused by the differences in habitat use, susceptibility to heavy-oil, life history and migration ability. The findings suggest that it took at least 2–3 years for the intertidal animal community to recover to its original level after the oil spill.

Consumption of drift kelp by intertidal populations of the sea urchin Tetrapygus niger on the central Chilean coast: possible consequences at different ecological levels

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 251:141-151 (2003) - doi:10.3354/meps251141 Consumption of drift kelp by intertidal populations of the sea urchin Tetrapygus niger on the central Chilean coast: possible consequences at different ecological levels Sebastián R. Rodríguez1,2,* 1Departamento de Ciencias Básicas, Universidad Santo Tomas, Ejército 146, Santiago, Chile 2Center for Advanced Studies in Ecology & Biodiversity, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Casilla 114-D, Santiago, Chile *Email: srodriguez@ust.cl ABSTRACT: Drift algae are an important food resource for many intertidal marine invertebrates. This study quantifies the arrival rate of drift kelp on the intertidal zone of central Chile and analyses its nutritional role in maintaining populations of the sea urchin Tetrapygus niger. The analysis was based on stomach contents and on stable isotope ratios of the food and the sea urchin. Gonad development was also evaluated. Lessonia nigrescens was the kelp most commonly observed, and its arrival pattern showed both temporal and spatial variation. The highest levels of drift kelp occurred in late spring, early summer and part of the autumn. Lessonia spp. were the most important food of T. niger, comprising 68% of the diet, and most of the assimilated carbon came from this source. The availability of drift kelp influenced gonad development. Trophic subsidies such as drift kelp are clearly important to intertidal animals of temperate ecosystems and have effects at different levels of biological organization. Two alternative scenarios of community organization are proposed for tidepools, depending on drift kelp availability. KEY WORDS: Drift kelp · Rocky substratum · Tidepools · Sea urchins · Gonad development · Community structure Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 251. Online publication date: April 11, 2003 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2003 Inter-Research.

Thermal Physiology and Vertical Zonation of Intertidal Animals: Optima, Limits, and Costs of Living

Temperature's pervasive effects on physiological systems are reflected in the suite of temperature-adaptive differences observed among species from different thermal niches, such as species with different vertical distributions (zonations) along the subtidal to intertidal gradient. Among the physiological traits that exhibit adaptive variation related to vertical zonation are whole organism thermal tolerance, heart function, mitochondrial respiration, membrane static order (fluidity), action potential generation, protein synthesis, heat-shock protein expression, and protein thermal stability. For some, but not all, of these thermally sensitive traits acclimatization leads to adaptive shifts in thermal optima and limits. The costs associated with repairing thermal damage and adapting systems through acclimatization may contribute importantly to energy budgets. These costs arise from such sources as: (i) activation and operation of the heat-shock response, (ii) replacement of denatured proteins that have been removed through proteolysis, (iii) restructuring of cellular membranes ("homeoviscous" adaptation), and (iv) pervasive shifts in gene expression (as gauged by using DNA microarray techniques). The vertical zonation observed in rocky intertidal habitats thus may reflect two distinct yet closely related aspects of thermal physiology: (i) intrinsic interspecific differences in temperature sensitivities of physiological systems, which establish thermal optima and tolerance limits for species; and (ii) 'cost of living' considerations arising from sub-lethal perturbation of these physiological systems, which may establish an energetics-based limitation to the maximal height at which a species can occur. Quantifying the energetic costs arising from heat stress represents an important challenge for future investigations.

Ontogeny of phototaxis and geotaxis during larval development of the sabellariid polychaete Phragmatopoma lapidosa

Thorson generalized that the larvae of intertidal animals should remain photopositive throughout larval life to facilitate encounters with shallow surfaces at settlement. We tested this idea for the sabellariid polychaete Phragmatopoma lapidosa by investigating ontogenetic changes in phototaxis and geotaxis of well-fed, laboratory-reared larvae. Larvae at each of 5 age groups were exposed to (1) 8 different light intensities from a directional light source in a horizontal trough and (2) complete darkness in a vertical chamber. Phototaxis changed with age. Half-day old larvae were not responsive to light, 1 d old larvae were positively phototactic, and all older larvae to 28 d age were negatively phototactic. Larvae from 0.5 to 28 d age were positively geotactic with the exception of 5 d old larvae, which lacked a defined response. Consequently, larvae of the predominantly intertidal P. lapi- dosa did not conform to Thorson's suggestion of continuous positive phototaxis in intertidal species.

Do Locals Rule? Interactions between Native Intertidal Animals and a Caribbean Barnacle in Hawai'i

Chthamalus proteus, a high intertidal barnacle from the Gulf of Mexico and the Caribbean, is one of the most conspicuous recent introductions to Hawaiian waters. It arrived sometime between the early 1970s, when the last thorough survey of intertidal barnacles on O‘ahu was done (Matsuda 1973), and the late 1990s, when it was photographed by an amateur biologist who was putting together a book on Hawai‘i’s sea creatures (Southward et al. 1998). On O‘ahu, the barnacle attains high densities in protected bays and lagoons, particularly where there are few other intertidal organisms. Chthamalus proteus is somewhat less abundant in semiprotected waters where it co-occurs with a suite of native organisms. We examined interactions between C. proteus and two native Hawaiian species, the barnacle Nesochthamalus intertextus and the pulmonate limpet Siphonaria normalis. The native barnacle is highly abundant on seawalls in Waikiki and frequently overgrows or undercuts the invader. Nesochthamalus intertextus grows twice as fast as C. proteus, which may allow the native to compete more effectively for space. To examine whether the native barnacle is limiting the distribution of the invader, we established 20 permanent quadrats along a seawall. In half of the quadrats native barnacles within 5 mm of invasive barnacles were removed; the remaining quadrats served as controls. Growth and survivorship of invasive barnacles in the quadrats have been tracked for 1 yr. An additional 12 quadrats were cleared of all native intertidal organisms. Recruitment of C. proteus to these quadrats and to 12 control quadrats was recorded for 10 months. Invasive barnacles in the treatment quadrats grew faster than those in control plots. Neither recruitment nor mortality was significantly different in treatment versus control plots, however, suggesting that factors other than competition (such as larval supply) also play a role in the distribution of the invader. It is more usual to ask whether an invader is impacting a native. There were too few of the invasive barnacles at Waikiki to test this with any statistical power. At Kualoa Beach, on O‘ahu’s windward side, the situation is reversed: the invader is abundant and the native is relatively rare. An experiment similar to the one in Waikiki was established in March 2000 to test the effect of C. proteus on the growth, mortality, and recruitment of N. intertextus. After 1 yr, there appeared to be no effect of the invader on the native in any of these categories. Interactions in Kāne‘ohe Bay between C. proteus and the pulmonate limpet S. normalis were also examined. The pulmonates are highly abundant (mean 30/100 cm) at Coconut Island on a seawall that is composed of several rock types. A survey of the wall showed that the invasive barnacles were less abundant on light-colored rock and that there was an additional negative effect of pulmonate density on barnacle abundance. The pulmonates were more abundant on light-colored rock; their densities were not additionally affected by barnacle numbers. Four types of cement settlement panels (dark smooth, dark rough, light smooth, light rough) were placed in the intertidal to test for settlement preferences of C. proteus and S. normalis. Barnacles did not show a preference for color, but limpets recruited preferentially to light-colored panels. Further experiments examining the effect of the pulmonates on recruitment of C.

Patterns of Distribution of Macro-fauna in Different Types of Estuarine, Soft Sediment Habitats Adjacent to Urban and Non-urban Areas

Urban development typically creates a large number of potentially interacting disturbances that may cause impacts on assemblages of animals and plans in estuarine habitats. We tested predictions from the general model that intertidal areas exposed to different types of disturbances have different types of assemblages of benthic macrofauna. Different parts of the Port Hacking Estuary (New South Wales, Australia) are exposed to varying degrees of disturbance by human activities. We predicted that the average structure of assemblages of intertidal animals, and patterns of variability would differ between urban and non-urban areas of Port Hacking. Consistent with previous observations from the literature, there were differences in average structure between urban and non-urban sandy areas. Qualitative differences between abundances of individual taxa in urban and non-urban areas were generally not consistent with previous observations. Differences between assemblages in urban and non-urban areas were not observed in muddy sediments, nor in sediments among mangroves and seagrass. No significant differences in variability was observed between urban and non-urban areas. Two general models may be proposed to explain the observed differences in response to urbanization in different habitats: (1) animals are exposed to different levels or combinations of disturbances in different habitats; or (2) assemblages of animals differ in sensitivity to disturbances among habitats.

The CSULB Mobile Science Museum: An interactive science outreach tool

Since 1980, a converted 27-ft recreational vehicle has been visiting local schools filled with a variety of hands-on science exhibits and activities. The Mobile Science Museum (MSM) has recently undergone a major renovation, including adding a generator. The MSM is now self-contained with inside exhibits that focus on the physical sciences, including sound, light, electricity, etc. The MSM also carries five large tables for outside activities, including a seawater touch-tank containing local intertidal animals, optical illusions, fossils, bones, etc. The majority of the exhibits have been developed or adapted for the MSM and utilize oscilloscopes, oscillators, strobes, power supplies, fans, and other equipment. University students act as docents and serve as enthusiastic role models for our young visitors. It is a compliment to the interest generated by the MSM that many of the current volunteer docents received their first exposure to the program when the MSM visited their schools several years ago. The major funding for the program has come from the CSULB Alumni Association, the Long Beach Industry–Education Council, and other individual support. The requests for visits greatly exceed the current ability to meet them, but this will improve as additional funding becomes available.

Poor design of behavioural experiments gets poor results: examples from intertidal habitats.

Many patterns of distribution and abundance of intertidal animals are explained by processes of movements of animals, selecting particular habitats or levels on the shore, or interacting with other species. Movements of intertidal animals have therefore been studied over many years. During this long history, much intertidal ecology has changed in focus from broad-scale to small-scale patterns and processes, although there has been recent refocus on a combination of many scales. Simultaneously, there has been an increase in the incidence of field experiments and growing recognition that behaviour is more flexible than originally thought. This review examines changes in the ways that experiments on movements on intertidal animals have been and are being done, taking into account these changes in emphasis. Although some progress has been made, there is still a long way to go. The idea is still prevalent that behaviour is simple, rather invariant and that the animals respond to broad-scale cues that have traditionally been of interest to many investigators. This means that many experiments are still designed to minimise (or ignore) natural variation in behaviour rather than to measure it and that any associated disturbances are considered irrelevant and therefore not evaluated. Understanding the role that behaviour has in establishing and maintaining many of the patterns observed on intertidal shores is crucial to our understanding of the ecology of these habitats. Better experiments, designed logically with appropriate controls to evaluate realistic processes and to measure how behaviour varies among places and from time to time can only improve this understanding.

Experimental ecology of rocky intertidal habitats: what are we learning?

Experimental analyses of causes of patterns of distribution and abundance of intertidal animals and plants on rocky shores have been a major activity for many years. In this review, some of the themes and topics that have emerged from such analyses are briefly discussed to provide an up-date for practitioners and ecologists working in other habitats. Conceptual issues include the widespread occurrence of transphyletic use of the same resources (space and food), theories and experimental analyses of intermediate disturbance in relation to numbers of species, the complex but pervasive nature of indirect interactions among species, relative importance of 'top-down' versus 'bottom-up' control of assemblages and the importance to rocky intertidal species of 'supply-side' influences on densities and interactions. Methodological advances include experimental designs for complex and patchy, interacting sets of species, the importance of controls in experimental manipulations and methods for analyses of hierarchical scales of patterns and processes. Finally, some contributions to social issues (pollution, biodiversity) and some scenarios for future directions are briefly considered.

Combined effects of pentachlorophenol and salinity stress on phagocytic and chemotactic function in two species of abalone

The effect of pentachlorophenol (PCP) combined with salinity stress on specific aspects of cellular immunity was examined in two species of abalone. Chemotactic and phagocytic ability (percent phagocytosis, % P; and phagocytic index, PI), as well as gross morphological characteristics, of hemocytes withdrawn from red ( Haliotis rufescens) and black abalone ( H. cracherodii) after in vivo exposure to 25, 35, or 45‰ seawater salinity plus 1.2 mg/l PCP were determined. Abalone exposures of 3.5 and 6.5 h, respectively, were based on species-specific metabolic endpoints (MEPs) derived from previous NMR data. Hemocyte chemotaxis was found to be augmented by low salinity in red but not black abalone, while high salinity seemed to reduce chemotactic ability in both species. PCP did not potentiate the effects demonstrated by salinity variations alone in red abalone, although chemotaxis was further compromised in black abalone exposed to high salinity stress combined with PCP. Although chemotactic ability was similar among both species, both % P and PI was greater among black abalone. Low salinity may offset the effects of PCP in red but not black abalone. Whereas red abalone demonstrated a reduction in phagocytic ability upon exposure to high salinity alone, black abalone appeared more resilient to high salinity stress alone. Furthermore, while the effect of high salinity plus PCP is subadditive among red abalone, high salinity seems to potentiate the effect of PCP on black abalone. Finally, hemocytes exposed to acute salinity variations plus PCP showed varying morphological characteristics when compared to controls. Over 30% of hemocytes of high salinity plus PCP exposed abalone remained rounded and generally unattached to glass slides with only a few pseudopod extensions. Hemocyte preparations incubated in rhodamine-conjugated phalloidin were observed with fluorescence microscopy and reveal an altered actin filament pattern. Overall, black abalone demonstrate greater phagocytic ability than red abalone both in the presence and absence of PCP. Furthermore, increases in salinity are accompanied with reduced phagocytic ability with red abalone demonstrating particular sensitivity to salinity variations. While PCP inhibits ATP synthesis, salinity variations may impose an additional stress on intertidal animals exposed to transient or seasonal environmental changes.

The clocks controlling the tide-associated rhythms of intertidal animals.

The living clock that governs tide-associated organismic rhythms has previously been assumed to have a fundamental period of approximately 12.4 h, an interval that reflects the average period of the ebb and flow of the tide. But, in 1986, marine chronobiologists began to accumulate laboratory results that could not be explained by the action of such a clock. Prime among these findings was the discovery that, occasionally, one of the two daily peaks in an organism's rhythm assumed a different period from its partner. Similar results have since been observed in a host of different organisms. These data led to the circalunidian-clock hypothesis that envisions two basic 24.8 h clocks, coupled together in antiphase, as the driving force for these rhythms. There is, however, only a slight difference (50 minutes) in running times between a solar-day clock with a period of approximately 24 h and a lunar-day clock with a period of approximately 24.8 h, both of which display "circa" periods that overlap. Here, I postulate that the two clocks are fundamentally one and the same. BioEssays 22:32-37, 2000.

The clocks controlling the tide-associated rhythms of intertidal animals

The clocks controlling the tide-associated rhythms of intertidal animals

Ecologically Relevant Variation in Induction and Function of Heat Shock Proteins in Marine Organisms

Ectothermic organisms often face dramatic traverses of environmental temperature on a daily or seasonal basis; exemplars among this group are invertebrates and fish of the rocky intertidal zone. Because of the extremes of temperature exposure, intertidal animals have served as an excellent study system to examine the expression of heat shock proteins (Hsps) in response to natural variation in environmental temperature. Ecologically relevant variation in Hsp expression has been observed with seasonal acclimatization, with small-scale temperature gradients that occur in microhabitats and between species with different intertidal distributions. The maturing understanding of Hsp expression patterns in marine organisms has established a solid foundation on which to build the next set of questions. In this paper, I present an overview of the variation of Hsp expression in intertidal animals in nature and then address two emerging areas of investigation in the ecological physiology of Hsps. One area addresses the plasticity of Hsp expression in marine invertebrates and focuses on the mechanism of regulation of Hsp gene expression by environmental temperature. A second emerging area of investigation concerns whether Hsps as molecular chaperones display functional diversity that correlates with species' adaptation temperature.

Assessment of variability in responses of intertidal periwinkles to experimental transplantations

Behavioural responses to variables associated with habitat and level on the shore are often given as explanatory models for vertical patterns of distribution or vertical gradients of size of intertidal animals. These models are frequently examined using experimental transplants in which animals are moved to levels (or habitats) where they are not usually found and their movements subsequently monitored. There are many problems with the design, execution and interpretation of most of these studies because of lack of appropriate experimental design and inadequate analyses to identify interactions among variables. This study examined the role of behaviour in determining patterns of distribution of two small periwinkles, Littorina unifasciata Gray and Nodilittorina pyramidalis (Quoy and Gaimard) on rocky shores in New South Wales, Australia, using experimental transplantations. Also examined were the experimental and analytical procedures necessary for such experiments and spatial and temporal variability in results obtained. N. pyramidalis and L. unifasciata responded to being transplanted downshore or, for L. unifasciata only, upshore by dispersing further and moving directionally towards their level of origin. These responses were persistent and relatively widespread across many sites. There was considerable variability in the results obtained from place to place and time to time, although transplanted snails were less variable in behaviour than were snails in other treatments or controls. Translocation to a different site at the same level on the shore caused snails to disperse longer mean distances, although not as far as moved by transplanted snails, but did not have a consistent effect on directionality of movement. Experiments such as these must include controls for disturbance and translocation if responses of transplanted animals are to be appropriately interpreted. They must also include proper design and replication so that variability in responses from site to site, day to day and among similar experiments can be quantified. Only then can processes influencing such behaviour be investigated and the role of behaviour in determining patterns be understood.

Dynamics of macrofaunal communities of floating seaweed clumps off western Iceland: a study of patches on the surface of the sea

The dynamics of macrofaunal communities of floating clumps of detached intertidal algae were studied by experiments and surveys. The density of some intertidal species tended to decrease slowly with time on experimental fronds of the brown seaweed Ascophyllum nodosum that were put afloat. Many planktonic and benthic species quickly colonized such fronds. Plastic seaweed mimics were also effective in attracting colonizers and it appeared to matter little whether the A. nodosum fronds carried a complement of intertidal animals or had been rinsed of animals before being put afloat. Colonization of experimental fronds was to some extent mediated through transfer from small algal pieces caught by the fronds. Floating algal clumps in coastal areas occur in a large range of sizes. Number of species present on such clumps was closely related to clump size. The density (numbers/100 g algae) of many intertidal species was positively linked with clump size. Distance from nearest shore was a poor predictor of species composition. The clumps form dynamic patches on the surface of the sea that often coalesce or break up. These patches greatly enhance the complexity of the neustonic environment and their species richness is much greater than in the surroundings.

Metabolic response to oxygen limitation in Arenicola marina as determined with the 1H NMR signals of myoglobin

During hypoxic stress many intertidal animals preserve their functional integrity by down regulating their energy utilization and by compensating the aerobic energy loss with anaerobic ATP production. Arenicola marina is a well established invertebrate model in which aerobic metabolism starts to decline well above the critical oxygen point. Even though the A. marina oxygen consumption profile versus ambient O 2 is well characterized, the underlying biochemical mechanism regulating intracellular oxygen metabolism in vivo remains unclear. Recently, 1H NMR has opened an approach to observe tissue oxygenation with the signals of myoglobin (Mb). The deoxy Mb proximal histidyl N δ H and the oxy Mb valine E11 γCH 3 signals are detectable in tissue and along with the Mb p(O 2) 50, can yield a quantitative measurement of the intracellular oxygen level. The A. marina Mb proximal histidly N δ H signals appear at 93.4 and 92.5 ppm (25°C), respectively, while the corresponding valine E11 γCH 3 signals appear at −2.83 and −2.74 ppm. As the p(O 2) declines, MbO 2 saturation and MVO 2 decrease. However, phosphotaurocyamine concentration remains unaltered until the MbO 2 saturation falls below 33%. The data suggest that the critical intracellular p(O 2) value is below 0.1 kPa (1 torr). The study establishes the 1H NMR technique as an approach to measure the intracellular p(O 2) with an oxygenated state marker and presents the interrelationship between oxygen and the metabolic adaptation during hypoxic stress.