Primary Substratum Research Articles

Origin and genetic diversity of the invasive mussel Semimytilus algosus in South Africa, relative to source populations in Chile and Namibia

Worldwide, the spread of alien species in marine ecosystems has increased, with mussels frequently being involved. In South Africa, 91 alien and 39 cryptic marine and estuarine species, from 17 taxonomic groups, are known. Of these, three are associated with major invasions, including the Pacific mussel, Semimytilus algosus, which has rapidly spread and colonised the lower portions of rocky shores on the west coast. Semimytilus algosus is indigenous to Chile and has been introduced to Namibia. To determine the source and likely mode of introduction of S. algosus, we analysed the population genetic structure of eight populations on the west coast of South Africa and Namibia, as well as three populations in the native Chilean range. Using cytochrome c oxidase subunit I, we collected sequence data from 226 individuals sampled across the 11 localities. We detected no evidence for founder effects, as the South African and Namibian populations had comparable genetic variation to those sampled in Chile, pointing to large effective population sizes and high propagule pressure in the region. It is probable that the Namibian population originated from Chile, and that introduction took place from there to South Africa via a single and substantial natural larval dispersal that breached the biogeographic barrier created by the Luderitz upwelling cell; but we cannot discount the possibility that introduction associated with oyster aquaculture played a role. Based on comparisons with Mytilus galloprovincialis, we predict S. algosus will continue to spread in South Africa but will be confined to temperate regions; reduce limpet abundance by monopolising primary substratum and because it is too small for them to occupy its shells; and supplement food sources for predators such as oystercatchers and dogwhelks.

Effects of sediment on early life history stages of habitat-dominating fucoid algae

The effects of sediment on settlement and early post-settlement survival of habitat-dominating fucoid algae have not been extensively investigated. Two separate experiments tested whether different size-fractions, abundances and types of sediment differentially affect the attachment of Hormosira banksii and Cystophora torulosa zygotes under laboratory conditions, and whether alteration of the sediment environment differentially affects early post-settlement survival of fucoid zygotes placed into the natural environment. In the laboratory, an average of c. 59% of Hormosira zygotes were able to attach to primary substratum in the presence of sparse sand and silt, compared to 28% (silt) and 39% (sand) of Cystophora zygotes. In the presence of dense sand or silt, <8% of either species attached to primary substratum, with the great majority of zygotes of both species attaching to sediment grains. In the field, Hormosira zygotes across three treatments survived for the entire two week experimental period, whereas no Cystophora zygotes survived beyond 8 days. For both species there was a gradient of survival across treatments, from the poorest survival on bare rock, slightly better survival in coralline turf that contained sediments, and greater survival in coralline turf with the sediment removed, although there were significant interactive effects of treatment and time. After two weeks, an average of 22% of Hormosira zygotes survived on bare rock, around 38% on coralline turf with sediment, and 40% on coralline turf minus sediment, but with high variation in the treatments. On day 5 of the field experiments, when zygotes of both species remained across treatments, there were significant differences between species and between treatments which mirrored results across the whole experiment. Overall, the experiment showed that the sediment environment influenced both the attachment of fucoid zygotes and early post-settlement survival. The experiments highlighted key differences between species in their method of attachment and subsequent interactions within the abiotic environment, with the larger stickier zygotes of Cystophora more readily attaching to sediment grains, and the less sticky Hormosira zygotes often rolling through the sediments and attaching to the primary substratum. These early life history characteristics of key species and their interaction with those of microsites in which they settle clearly have importance to the replenishment and maintenance of populations.

Lack of substrate specificity contributes to invasion success and persistence of Membranipora membranacea in the northwest Atlantic

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 580:117-129 (2017) - DOI: https://doi.org/10.3354/meps12287 Lack of substrate specificity contributes to invasion success and persistence of Membranipora membranacea in the northwest Atlantic Danielle Denley*, Anna Metaxas Department of Oceanography, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada *Corresponding author: danielle.denley@dal.ca ABSTRACT: Selective settlement by planktonic larvae plays a significant role in determining the distribution and abundance of many species of marine invertebrates. For non-indigenous species, larval settlement behavior can determine invasive potential by influencing initial invasion success, secondary spread, and persistence of species outside their native environments. Membranipora membranacea is an ecologically significant invasive bryozoan in the northwest Atlantic, where settlers are most abundant on some but not all species of kelp. Whether the increased abundance of M. membranacea on select kelp species is the result of larval settlement preference remains unknown. In this study, we examine selective settlement by larvae of M. membranacea by (1) quantifying settlers in mixed kelp beds and determining whether larvae settle preferentially with respect to kelp species, (2) conducting laboratory settlement preference experiments using the most abundant kelp substrates in Nova Scotia, and (3) examining whether the presence of kelp beds provides a settlement cue for larvae by quantifying settlement of M. membranacea on plates deployed within and outside of kelp beds. Contrary to settlement behavior described for native populations, our results suggest that larvae of M. membranacea in invaded habitats do not exhibit preference for settling on particular kelp species or within kelp beds. Instead, larvae settle on substrates extending furthest above the primary substratum. Lack of substrate specificity suggests that M. membranacea will continue to persist in the northwest Atlantic despite significant declines in regional kelp abundance. Our results emphasize the importance of early life-history strategies in contributing to invasion success. KEY WORDS: Invasive · Selective settlement · Invertebrate larvae · Life-history strategies · Bryozoans Full text in pdf format Supplementary material PreviousNextCite this article as: Denley D, Metaxas A (2017) Lack of substrate specificity contributes to invasion success and persistence of Membranipora membranacea in the northwest Atlantic. Mar Ecol Prog Ser 580:117-129. https://doi.org/10.3354/meps12287 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 580. Online publication date: September 29, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Understanding the association between the non-geniculate coralline red alga Spongites discoidea and the mollusc Oxystele sinensis

Nearly all adult winkles Oxystele sinensis encountered in the Kalk Bay (Western Cape province, South Africa) shallow subtidal zone were observed to bear a thick, convoluted form of the non-geniculate coralline red alga Spongites discoidea. To understand this association, various data were collected. The results show that O. sinensis is for the most part restricted to the shallow subtidal zone and rockpools, whereas the morphologically similar O. tigrina is largely restricted to the intertidal zone. Fleshy macroalgae were absent from all habitats sampled, with much of the primary substratum being occupied by encrusting algae. Spongites discoidea was restricted to intertidal rockpools and the shallow subtidal zone where O. sinensis was the most abundant winkle. Subtidal specimens of S. discoidea were generally thicker (7.24 mm [SE 0.55] on shells, 6.02 mm [SE 0.67] on boulders) than intertidal specimens (2.39 mm [SE 0.21] on boulders, 1.02 mm [SE 0.09] on bedrock), were more heavily burrowed into (44% [SE 3.32] for subtidal shells, 36% [SE 3.94] for subtidal boulders), and were more weakly attached (2.2 kg [SE 0.58] for subtidal shells, 8.4 kg [SE 0.77] for subtidal boulders). Experimental evidence showed that the coralline has no preference for shells of O. sinensis and that, contrary to our assumption, there is no apparent advantage to the winkle bearing the coralline, other than perhaps for camouflage to avoid predation. The high frequency of the association is more likely due to the substantial overlap in the niches of the coralline and the winkle.

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.

Distribution of hydroids along fronds of the kelp Ecklonia radiata

Abundances of organisms generally increase with structural heterogeneity and complexity of habitat. Patterns of distribution of hydroids on the kelp Ecklonia radiata were studied in Australia to examine the generality of this pattern. It was predicted that the cover of hydroids on E. radiata would be greater in the most heterogeneous (e.g., peripheral, crinkled blades) and complex (e.g., middle and bushy) parts of the alga. When different zones were independently compared along laminae of E. radiata, two clear patterns were found. Covers of hydroids in basal, middle and distal zones were greater in the periphery than in the centre of kelp. Second, covers in the periphery and in the centre of kelp were greater in middle than in distal zones and greater in distal than in basal zones. Both patterns conform to those predicted. At a finer spatial resolution, hydroids were significantly more abundant in troughs than on ridges of the peripheral blades of E. radiata. The primary substrata on which kelp was growing (pier-pilings or shark-nets) did not affect the distribution of hydroids. Biological and abiotic factors associated with the kelp itself most probably influence the distribution of hydroids along fronds, but manipulative experiments are needed to establish what models explain these patterns.

Artificial structures influence fouling on habitat-forming kelps

The addition of artificial structures along urbanised shorelines is a global phenomenon. Such modifications of habitats have important consequences to the abundance of fouling organisms on primary substrata, but the influence on fouling of habitat-formers living on these structures is poorly understood. Fouling of habitat-forming kelps Ecklonia radiata on pier-pilings was compared to that on rocky reefs at three locations in Sydney Harbour. Kelps on pilings supported different assemblages of bryozoans from those on reefs. The abundances of bryozoans on kelps, inparticular of the non-indigenous species Membranipora membranacea, were significantly greater on pilings. Differences were consistent in time and space. This indicates that the addition of artificial structures also affects fouling on secondary biogenic substrata, altering biodiversity and potentially facilitating the introduction and dispersal of non-indigenous epibiota. Understanding the processes that cause these patterns is necessary to allow sensible predictions about ecological effects of built structures.

Competition in vitro among fungi acquired from the exoskeleton of the giant Madagascar hissing-cockroach, Gromphadorhina portentosa, and its relevance to human health

Abstract Few insects have received as much public attention as the Madagascar hissing-cockroach, Gromphadorhina portentosa , coveted by children as a household pet. Recently, this insect has been linked to allergies and asthma triggered by an antagonistic external mycoflora, and some of these fungi are known to cause serious illnesses, namely Aspergillus spp., Mucor spp. and Rhizopus spp. Other cockroach species serve as carriers of medically important fungi, but G. portentosa is of special concern because it is deliberately reared in captivity. The aim of this study was to ascertain why certain types of fungi dominate the exoskeleton’s mycoflora whereas others do not. Six ascomycetes ( Alternaria alternata , Aspergillus flavus , Aspergillus niger , Cladosporium cladosporioides , Penicillium glabrum , Trichoderma viride ), and two zygomycetes ( Mucor racemosus , Rhizopus stolonifer ) initially acquired from the exoskeleton of G. portentosa , were tested for their competitive ability to inhibit one another in vitro , using the cockroach as the primary substratum. R. stolonifer , M. racemosus , and mycoparasitic T. viride grew at a significantly faster rate compared to the other taxa, and growth rates correlated positively with conidia output. Slower colony growth rates were noted prior to physical contact, suggesting that the fungi engaged in chemical antagonism. Three genera emerged that best fit the profile of exploitative competitors – Rhizopus , Mucor , Trichoderma . The latter two genera completely inhibited the growth of all fungal taxa tested and also had some capacity to grow over the mycelium of another fungus. We conclude that M. racemosus and T. viride in particular, are successful agents of G. portentosa ’s mycoflora because they utilize both exploitation and interference competition to their advantage. Eliminating or reducing the simple sugar load entering the cockroach colony may be one way to tilt the composition of the mycoflora to favour strains that are less medically significant. Thus, we emphasize reduction of the antagonistic fungi at the colony (food entry) level and less so on the exoskeleton level.

Positive and negative effects of a dominant competitor on the settlement, growth, and survival of competing species in an epibenthic community

Because dominant competitors can monopolize resources, any positive effects they have on other species can have large community impacts. The solitary tunicate Ascidia ceratodes is a dominant competitor in the fouling community in Bodega Harbor, CA. This tunicate preempts primary substratum from competitors, but its thick tunic also allows other species to grow on its surface. The net effect of Ascidia on the community as a whole therefore depends on the balance between competitive and facilitative effects. In this study we evaluate the facilitative effects of Ascidia on different life stages of common competing species. We quantified larval settlement onto Ascidia compared to unoccupied space; we quantified the growth rate on Ascidia of small colonies of two common species; and we measured whether established colonies could escape overgrowth by Ascidia by growing onto its tunic. We found evidence for high rates of settlement on Ascidia, with some species showing higher and others lower settlement relative to that observed on free space. The growth rate of settlers was generally lower on Ascidia compared to primary substratum. We also found that colonial species established on primary space commonly escape overgrowth from Ascidia by growing onto Ascidia, as this occurs in about half of all encounters. This study indicates that the total effect of Ascidia on the community will depend on species-specific and life stage-specific effects, with likely long-term consequences for the diversity and composition of the community.

Recruit/algal interaction prevents recovery of overexploited mussel beds: Indirect evidence that post-settlement mortality structures mussel populations

The mechanisms maintaining community structure following an ecosystem shift are poorly understood and we propose that they must inherently be biological. Over-exploitation can provide a “natural experiment” with man as a predator driving a change in community structure, possibly an ecosystem shift. We examined a possible mechanism that maintains algal beds as an alternative state on the east coast of South Africa where the mussel Perna perna has been overexploited. Even on unexploited shores, about 50% of mussel larvae settle onto algae, but it is unclear whether they later recruit into adult beds. On such shores we used two indirect field approaches to understand the fate of recruits, testing whether inhibition of mussel recruitment by macroalgae could constitute a biological mechanism preventing reversion from the algal to the pre-disturbance mussel-dominated state. First, we examined possible ontogenetic migration of recruits from algae to adult mussels, testing the prediction that the ratio large:small recruits in adult beds is greater where algae are liberally interspersed with mussels. Second, we examined whether, like adults, recruits show spatial structure that is related to the distribution of topographic depressions, testing the hypothesis that large and small recruits show different co-variation with depressions, microhabitats where algae commonly occur. We found no evidence that recruits on algae actively move to nearby mussel beds as neither the ratio large:small recruits nor the abundances of small or large recruits showed any relationship with algal cover/variability. Small and large recruits showed different co-variation with topographic depressions on spatially structured transects. Like adults, large recruits commonly exhibited negative relationships with depressions. Thus, large recruits neither occur on algae nor migrate from algae to the primary substratum or onto adult beds. Consequently our results (a) highlight the importance of post-settlement mortality in structuring these mussel populations, and (b) suggest that the interception of larvae by algae forms a biological mechanism that can maintain macroalgal beds that develop following exploitative disturbance by man, thus preventing or at least drastically delaying the natural recovery of mussel beds.

Regeneration of Sponges in Ecological Context: Is Regeneration an Integral Part of Life History and Morphological Strategies?

Sponges, simple and homogeneous relative to other animals, are particularly adept at regeneration. Although regeneration may appear to be obviously beneficial, and many specific advantages to regeneration of lost portions have been demonstrated, comparisons of regeneration among species of sponges have consistently revealed substantial differences in style (i.e., relative rates of reconstituting surface features, infilling depressions, regaining lost primary substratum), and overall time course, raising questions about adaptive significance of variations in patterns of regeneration. Do sponges simply regenerate as quickly as possible, given constraints imposed by skeletal construction, morphology, or other traits that are determined primarily by evolutionary heritage? Does allocation of energy or materials impose trade-offs between regeneration versus competing processes such as growth or reproduction? Is regeneration time-course and style an integral part of coherent life history and morphological strategies? One approach to answering these questions is to compare regeneration among species that represent a spectrum of higher taxa within the demosponges as well as different growth forms and life-history strategies. Because detailed ecological studies of sponges have tended to focus on small sets of species of the same growth form, community-wide comparisons have been hampered. Data on growth rate, colonization, mortality, susceptibility to predation, and competitive ability have recently been accumulated for species of sponges typical of the Caribbean mangrove prop-root community. Experimentally generated wounds in individuals of 13 of these species allow comparison of the timing and style of regeneration among sponge species that span a range of life histories and growth forms. The species chosen represent four orders of the class Demospongiae, and include four sets of congeneric species, allowing distinction of patterns related to life history and morphology from those determined by shared evolutionary heritage.

Recruitment, growth and population size structure of Pollicipes pollicipes in SW Portugal

A general model for the life cycle of Pollicipes pollicipes in SW Portugal is proposed integrating results from a study on recruitment, growth and population size structure. A brief summary of literature concerning Pollicipes published since Margaret Barnes' review paper of 1996 is presented. Recruitment of P. pollicipes on conspecifics (number of cyprids and juveniles with Rostro-Carinal length (RC) < 0.6 mm per adult) was intense during summer and autumn, but inter-annual variation in the timing and duration of recruitment season was observed. Different indices of recruitment used in Iberian studies were compared. Spatial correlation between shores (∼ 40 km apart) in SW Portugal suggests that cyprids of P. pollicipes are being affected by the same larval pool and physical transport processes operating at this scale. Recruitment of P. pollicipes in SW Portugal was higher on the low shore (∼ 2.5 times) than on the high shore. Most recruits were attached to the lower half of the adult peduncle. The period of maximum attachment of juveniles (RC < 12.5 mm) to conspecifics was summer and autumn (average of 15 juveniles per adult), while spring was the season with a lower number of juveniles growing on adults (average of 2 juveniles). Size of juveniles attached to conspecifics was rarely greater than 6 mm RC. Individual annual growth rate of P. pollicipes that settled on a denuded surface was 15.7 mm RC (individuals ≤ 1 year old) which corresponds to a monthly increment of 1.3 mm RC in their first year of life. Size structure analyses of P. pollicipes attached directly to primary substratum and/or to the base of conspecifics showed that barnacles at the low tide level reached a higher maximum size, indicating that growth at this level was faster than on the high shore. A higher temporal variability between these size-frequency distributions was detected in spring (March to May). In March, two cohorts (< 1 year old, > 1 year old) were identified. In May and August, it was difficult to identify individual different cohorts. From mid autumn to early spring, as a consequence of recruitment of barnacles to the primary substratum, it was again possible to identify two cohorts.

Combination of biodegradable organic matter quantification and XAD-fractionation as effective working parameter for the study of biodegradability in environmental and anthropic samples

The present work proposes to couple quantification of biodegradable organic matter (BOM) with XAD-fractionation. Biodegradable dissolved organic carbon (BDOC) and assimilable organic carbon (AOC) analysis were applied to fractions extracted by XAD resin. An examination of mechanisms during consumption of BOM has been carried out, using comparison of biodegradability between the bulk BOM of samples (landfill leachate and surface water) and the sum of BOM contents obtained for the extracted fractions. Results point out that a cometabolism mechanism seems to be involved during the degradation of the surface water fractions. On the other hand, fractions extracted from the leachate seem to be degraded as primary substratum. The more reactive fractions of the leachate (HPO ∗) and the water (HPI) have been identified as well the less reactive (HPI ∗ and HPO, respectively). The BDOC contents determined for the bulk leachate and surface water are 10 ± 2% and 28 ± 2%, respectively. The values of AOC are 107 ± 18 μg C acetate L −1 and 163 ± 21 μg C acetate L −1, respectively.

Spatial and temporal effects of pre-seeding plates with invasive ascidians: Growth, recruitment and community composition

Many shallow water subtidal habitats in Massachusetts, USA have recently been invaded by five non-indigenous ascidian species: Ascidiella aspersa, Botrylloides violaceus, Didemnum sp., Diplosoma listerianum and Styela clava. This study examined the effects of seawater temperature, as a proxy for climate change, on B. violaceus and D. listerianum and the impact these ascidians have on native sessile fouling communities. Field experiments were conducted over a four month period at two locations (Lynn and Woods Hole, MA) to examine growth dynamics over regional thermal and geographic ranges. Invasive ascidians occupied as much as 80% of the primary substratum and accounted for the majority of species richness. B. violaceus and D. listerianum growth were similar at both study sites, but initial colony growth of D. listerianum was positively affected by temperature. B. violaceus and D. listerianum exhibited rapid two-week growth rates during the summer months with more rapid growth at the warmer Woods Hole site. Competition for space between B. violaceus and D. listerianum typically resulted in neutral borders between colonies. Overgrowth occurred if the colony of one species was disproportionably larger than the colony of the other species. Recruitment and growth of native species influenced the long-term composition of experimental communities more than the pre-seeding with B. violaceus or D. listerianum colonies. Elevated temperatures, however, increased initial growth of B. violaceus and D. listerianum and may have facilitated the species success to invade the communities during crucial periods of introduction. With projected global climate change, a rise in sea surface temperatures may exacerbate the cumulative impacts of invasions on benthic communities and facilitate the invasion of other non-native ascidian species.

Effect of Detachment on the Palatability of two Kelp Species

Many species of macroalgae survive after becoming dislodged from their primary substratum, but little is known about their capacity to express anti-herbivore defences after detachment. We examined the effect of detachment on the relative palatability of the two kelp species Lessonia nigrescens and Macrocystis integrifolia to mesograzers. Laboratory and field experiments were conducted on the northern-central coast of Chile to investigate whether (i) time after detachment and (ii) grazing on detached and attached algae could trigger internal defence mechanisms in the algae, which may have acted as deterrents to grazing. In order to examine palatability, feeding assays were run after each experiment using fresh algal pieces and artificial food. Time after detachment had a significant influence on palatability of L. nigrescens but not of M. integrifolia. During the first 12 days of detachment, detached L. nigrescens held in grazer-free laboratory tanks were not significantly more palatable than attached conspecifics from the field but thereafter detached individuals became more palatable. Floating individuals of M. integrifolia showed no effect of detachment, indicating that this alga maintains its defence after detachment. An experiment conducted in the field confirmed these results for M. integrifolia. An additional laboratory experiment confirmed that attachment status plays an important role on algal defence reaction for L. nigrescens when exposed to grazers. Detached and previously grazed individuals of this species were less palatable than grazer-free control algae, but grazing had no effect on palatability of attached algae. Our results indicate that kelps have varying capacities for development of anti-grazing responses once they become detached, possibly depending on their capacity to float and survive after detachment.

Mussel beds on different types of structures support different macroinvertebrate assemblages

Abstract Artificial structures, such as seawalls, pilings and pontoons, are common features of urban estuaries. They replace natural structures or add to the amount of hard substratum in an area and provide habitats for many fish and invertebrates. Previous work has concentrated on fish or on the invertebrates that occupy the primary substratum of artificial structures. Mussels often grow on different types of structures (pontoons, pilings, seawalls and natural reefs) and provide a secondary substratum for other organisms to inhabit. Counting and identifying organisms associated with mussel beds is traditionally done to species level, which is very time‐consuming. To save time, organisms in this study were identified to coarse levels of taxonomic resolution (a mix of taxa, such as class, order, family and genus), which showed similar patterns to those when particularly speciose and abundant groups were identified to species. This study tests hypotheses that the distribution and abundance of mobile and sessile organisms that inhabit mussel beds will differ among natural and various types of artificial structures. When the associated assemblages of mussel beds from different types of structures and from different locations were examined, assemblages varied according to the type of structure they inhabited and its location. Assemblages associated with mussels on pontoons differed consistently from those on other types of structures. Patterns in the assemblages were also consistent through time. These data show that the types and amounts of artificial structures added to an environment can affect the types, distribution and abundances of organisms living in biogenic habitats.

Sediment on rocky intertidal reefs: Effects on early post-settlement stages of habitat-forming seaweeds

Modification of the coastal environment by human activities often leads to an increase in sedimentation of nearshore waters, with potential impacts on benthic marine assemblages. Here we assess the relationships between the levels of sedimentation, wave exposure and benthic organisms on rocky intertidal platforms around the Kaikoura Peninsula in southern New Zealand. We designed and tested five sediment traps to provide a tool for measuring the relative abundance of sediment across sites. Using field- and laboratory-based experiments, we tested hypotheses concerning whether different levels of sedimentation affected algal germling survival and algal zygote attachment, and whether the interactions of grazers and sediments affected germling survival. Levels of sediment and exposure were inversely related across seven sites. The fucoid alga Hormosira banksii characterized the more sedimented wave-sheltered and intermediately wave-exposed sites, with up to 80% cover in the lower mid-tidal zone, while the bull kelp Durvillaea antarctica characterized the three most wave-exposed sites. Grazing molluscs were found across all sites but species abundances varied by sediment and exposure levels. We did two 11-day trials testing the effects of different levels of sediment and different species of molluscan grazers on the survival of 1-week-old Hormosira germlings. Generally, there was no significant treatment effect of grazers, but mortality varied considerably among sites. In particular, one site had very high levels of sediment, which resulted in 100% mortality of germlings across all grazer treatments. Removing sediment at 1-week, 2-week and 4-week intervals made no difference to the survival of Hormosira germlings. In laboratory-based experiments, a light dusting of sediment reduced the percentage of zygotes of Hormosira by 34% and Durvillaea by 71% that attached to primary substratum, and a complete cover of sediment prevented attachment altogether. Overall, the effects of sediments and its interaction with molluscan grazing were highly variable but often large, particularly on the attachment of zygotes to primary substratum.

Neurological Subtrata of the Basic Ego States

This article relates contributions from the field of neuroscience to the basic functional model of ego states from transactional analysis. Among the diverse neuroanatomical and neurochemical operating systems that have been investigated and described, the author considers four to be the primary subcortical substrata of the three basic cerebral networks that neurologically sustain the manifestation of the three basic functional ego states. Previously, he also described the three main groups of neurological structures in the brain and their structural interplay in the ego states, considering them the cerebral substrata of the psychic organs.

Induction of metamorphosis in larvae of the brooding corals Acropora palifera and Stylophora pistillata

Many coral larvae require surface contact with crustose red algae (CRA) to induce metamorphosis; however, many features of the ecology of pocilloporid corals, such as their ability to colonize primary substrata, suggest that their larvae respond to different cues. We compared the metamorphosis of larvae of the brooding corals Stylophora pistillata (family Pocilloporidae) and Acropora palifera (family Acroporidae) in response to a variety of environmental cues. Acropora palifera metamorphosed only in the presence of three species of CRA. In contrast, S. pistillata metamorphosed in all assays, except those containing the brown alga Lobophora sp. Metamorphosis was highest (80 ± 20%) in unfiltered sea water; however, metamorphosis also occurred in 0.2-μm filtered sea water. These results suggest that S. pistillata larvae respond to both large and small water-borne molecular cues. The lack of a stringent requirement for surface contact with CRA will allow S. pistillata larvae to pre-empt species that require a more developed fouling community to induce metamorphosis and this feature of larval ecology may be the key to understanding the success of many opportunistic benthic species.

Hydroid colonies as primary substrata for recruits of the musselMytilus edulis platensisfront off Mar Del Plata, Argentina

Abstract Due to the sparse presence of algae, hydroid clumps appear as the main primary substrata for the settlement of epizoical mussels in Buenos Aires province (Argentina). The settlement and growth of Mytilus edulis platensis on Amphisbetia operculata and Plumularia setacea colonies during their first life stages was analyzed throughout the year and the double settling larvae phenomenon is discussed. Colonies of both species were frequently colonized by numerous spat, which reached a maximum density of 1370 and 1450 individuals g-1 of colony, respectively. Settlement of Mytilus larvae on the hydroids occurred mainly in November, decreasing in December and January. The plantigrade's biomass on A. operculata increased from December until April in spite of a decrease in the number of individuals. In constrast in P. setacea both plantigrade numbers and biomass decreased from December and no individuals were found in February. The major abundance and permanency of plantigrades on A. operculata could be exp...