Erect Bryozoans Research Articles

The genome sequence of an erect bryozoan, Bugulina stolonifera (Ryland, 1960).

We present a genome assembly from a Bugulina stolonifera colony (an erect bryozoan; Bryozoa; Gymnolaemata; Cheilostomatida; Bugulidae). The genome sequence is 235 megabases in span. Most of the assembly (99.85%) is scaffolded into 11 chromosomal pseudomolecules. The mitochondrial genome was also assembled and is 14.4 kilobases long.

Early Maastrichtian erect bryozoans from western Kazakhstan, with descriptions of two new species and the comparative internal morphology of some cheilostome genera

Early Maastrichtian erect bryozoans from western Kazakhstan, with descriptions of two new species and the comparative internal morphology of some cheilostome genera

The suitability of alkali activated slag as a substrate for sessile epibenthos in Reef Cubes®

Reef Cubes® are novel artificial reef units intended to enhance habitat complexity and provide hard substrate around marine man-made infrastructure. If made with Portland Cement, Reef Cubes® could create numerous negative environmental impacts, including a high carbon footprint. Alkali-activated materials (AAMs) are a collection of alternative binders associated with lower embodied emissions but alterations to concrete chemistry can affect the development of marine fouling communities. The objectives of this study were to evaluate the effect of replacing Portland Cement with an AAM binder on the development of macrofouling communities on Reef Cubes®. 25 cm sided Reef Cubes® were manufactured using three different concrete material types and deployed in the subtidal zone of Torbay, Devon, UK. The material types were an alkali activated slag concrete (Type: AAM), a cement-limestone blend (CEM-II) concrete (Type: C) and a cement-limestone blend (CEM-II) concrete with an additional micro silica pozzolan and an exposed aggregate texture (Type: CP). After 1 year of immersion the Reef Cubes® were retrieved, and fouling communities were analysed visually or scraped and weighed to gauge biomass. Univariate metrics of species richness, species diversity, total live cover, total biomass, calcareous mass and live biomass; and multivariate community compositions were compared. There were no significant differences in species richness, species diversity, total biomass, calcareous mass and live biomass between the material types. Total live cover was significantly different; with C appearing the highest, followed by AAM and CP, however pairwise comparisons were not significant. The community compositions on the AAM and C Reef Cubes® were not significantly different. Both were significantly different to the CP material type, which had a higher abundance of erect Bryozoans. The results suggest that compared to cement-based concretes, AAMs are a satisfactory substrate for the development of epibenthic communities on Reef Cubes®. There was also evidence contrary to common artificial reef practice that exposing the aggregate and incorporating a pozzolan improves biodiversity.

Ecology, distribution and demography of erect bryozoans in Mediterranean coralligenous reefs

Coralligenous reefs are considered as one of the most important benthic ecosystems in the Mediterranean Sea in terms of biodiversity, ecosystem functioning, and aesthetic value. Bryozoans deserve special attention within the coralligenous framework fauna: they are among the most common animals, showing high diversity values and playing different functional roles. Distribution, spatial variability, and demographic features of five erect bryozoan taxa Adeonella sp., Myriapora truncata, Pentapora fascialis, Reteporella sp., and Smittina cervicornis were studied in the central Tyrrhenian Sea. Abundance, size, and relationship with other taxa/morphological groups of benthic organisms were studied in coralligenous reefs between 35 and 40 m depth. High density of colonies was reported especially in association to gorgonians and algae dominated assemblages. Size distributions of the five bryozoans were characterized by small colonies; only two species (P. fascialis and S. cervicornis) showed colonies larger than 50 cm2. Structure of coralligenous assemblages and disturbances outlined different ecological requirements of the five studied taxa. Results provide baseline information for monitoring trajectories of change of these organisms in the coralligenous ecosystem. To date, this work represents the first study exploring ecology and distribution patterns of common erect bryozoans in the Mediterranean Sea.

Coralligenous formations dominated by Eunicella cavolini (Koch, 1887) in the NE Mediterranean: biodiversity and structure

Coralligenous formations are biogenic structures typical of the underwater Mediterranean seascape. Their intricate, multi-layered species assemblages are composed of perennial, long-lived organisms, particularly vulnerable to natural or human-induced disturbances. Despite their high ecological role and conservation value, few studies have addressed the assemblages outside the NW Mediterranean. This is the first quantitative assessment of coralligenous in the N Aegean Sea (NE Mediterranean), specifically focusing at the upper bathymetric limit of assemblages that are dominated by the yellow gorgonian Eunicella cavolini. The number and percent cover of macrobenthic species were studied at depths of 18 to 35 m, using a photoquadrat method. A total of 99 benthic taxa were identified, out of which 89 perennial ones were used to investigate spatial patterns in assemblage structure, composition, and biodiversity. A mean number of 47 perennial taxa were recorded per site, with encrusting coralline algae and sponges being the dominant groups in percent cover and species number, respectively. Across the studied localities, structural complexity and community composition were overall similar, but assemblages presented distinctive differences at the level of sites highlighting the role of local abiotic and anthropogenic factors in the shaping of the coralligenous. Compared to the rest of the Mediterranean, assemblages hosted a similar number of taxa. However, the number and percent cover of erect bryozoans were generally low, while, apart from E. cavolini, other erect anthozoan species were absent. This work provides an important baseline for comparisons and monitoring at a local or Mediterranean scale level.

Deep coralligenous outcrops of the Apulian continental shelf: Biodiversity and spatial variability of sediment-regulated assemblages

Structure and spatial variability of coralligenous assemblages of the Apulian continental shelf in the southern Adriatic Sea were investigated. The area consists of small coralligenous outcrops distributed between 30 and 100 m of depth on coarse detritic or muddy bottom. Photographic samples, obtained through a Remotely Operated Vehicle, were analyzed to evaluate the abundance of the main taxa or morphological groups of macroalgae and sessile invertebrates, and the deposited sediment. A multifactorial sampling design was used to compare assemblages at two depth ranges, the shallow outcrops (between 35 and 45 m) and the deep outcrops (between 60 and 70 m), and to determine the main scales of spatial variation. Assemblages were dominated by encrusting and erect sponges, encrusting and filamentous algae, scleractinians, encrusting and erect bryozoans and the Zoantharia Parazoanthus axinellae. Deep assemblages were characterized by lower alpha and beta diversity, and by the decrease or disappearance of sensitive organisms, such as coralline macroalgae, scleractinians and erect bryozoans, and by the dominance of encrusting sponges, P. axinellae and hydrozoans. Sedimentation was higher on deep outcrops and was suggested to be the main driver of differences between shallow and deep assemblages. The peculiar composition of assemblages found in the Apulian continental shelf provides evidence that these outcrops represent an uncommon coralligenous habitat.

Diversity of marine bryozoans inhabiting demosponges in northeastern Brazil

As primary or obligate sessile organisms, bryozoans depend upon a substratum resource that affects their abundance, distribution and diversity. These animals can colonize virtually any type of substratum, including other organisms and artificial structures. Associations between bryozoans and sponges are commonly reported in the literature, but there are few studies discussing the association between these two taxa in detail. Here we present data on the bryozoan community found on shallow-water sponges from Bahia coast, northeastern Brazil, including their taxonomic status, colony form and adaptative structures utilized by these bryozoans to grow on sponges. Twenty-one bryozoan species were found attached to the surface of sixteen species of sponges. Five new species of cheilostome bryozoans are described. A total of 105 colonies were studied and most of them are erect delicate branching (44 colonies) and encrusting patches (34 colonies). The majority of bryozoan colonies were attached to the surface of rugose-textured sponges (67 colonies; 61%). This suggests that bryozoans are more likely to settle on irregular and rough surfaces. Patches colonies were mainly attached to the portion of the sponge that was in contact with the seabed, and spot colonies were particularly found in spatial refuges, showing the preference of larvae to settle on shaded and less exposed substrata. Most erect bryozoans were attached to the lateral sponge surface, other colonies grew on the underside and few on the upper surface of the sponges. These colonies were attached either using anchoring rhizoids, rigid bases, or stolons. The bryozoan species and genera reported here are common in northeastern Brazil and considered generalists in terms of larval settlement requirements. The bryozoan-sponge association studied is considered a non-obligatory commensalism (inquilinism).

Articulation in the Family Rhabdomesidae (Cryptostomata: Bryozoa) from the Mississippian of Ireland

Articulation in erect bryozoans is known from the Ordovician to the Recent, and is developed in a number of Palaeozoic Orders. In the Order Cryptostomata, articulation is largely confined to some members of the Suborder Ptilodictyina and the Family Arthrostylidae of the Suborder Rhabdomesina, and was previous noted in the sole genus of the Family Bactroporidae. Articulation is reported herein in the Family Rhabdomesidae for the first time. The new genus Pharopora from the Mississippian of Ireland is characterised by zoaria composed of branches with regular internodes and conical-shaped articulating terminations.

Unheralded arrivals: non-native sessile invertebrates in marinas on the English coast

Between 2005 and 2012, 61 marinas and harbours around the English coast were surveyed to record the occurrence of non-native species (NNS) of sessile invertebrates. From these surveys, geographic distributions are described for eight species of ascidians, six bryozoans and five other species. A mean of 6.7 sessile invertebrate NNS per site (range 0–13 species) was recorded. At the 43 sites on the English Channel coast, the mean was 7.8 NNS per site, and all of the ten English sites that had ≥ 10 NNS were in the western or central region of the Channel coast. Ten sites on the Channel coast surveyed in 2004 were re-visited at least once in 2009 or 2010, and the mean number of sessile invertebrate NNS had increased from 6.0 to 7.6 species per site. Combining data from all visits in 2005–2012 for the sites surveyed in 2004, the mean number of NNS recorded per site rose to 9.2. Very rapid rates of spread along the English coast and beyond are inferred for the erect bryozoan Tricellaria inopinata d’Hondt & Occhipinti Ambrogi, 1985 and the ascidian Corella eumyota Traustedt, 1882. At least five recently arrived species that were limited to a small number of sites in 2012 are expected to increase markedly in geographic range and prevalence: the ascidians Asterocarpa humilis (Heller, 1878), Botrylloides diegensis Ritter and Forsyth, 1917, and Didemnum vexillum Kott, 2002; and the bryozoans Schizoporella japonica Ortmann, 1890 and Watersipora subatra (Ortmann, 1890). Rapid assessment surveys of marinas and similar sites proved to be an effective means of documenting the arrival and spread of NNS over a relatively wide geographic range and of distinguishing different rates of progression.

Assessing the erect bryozoan Myriapora truncata (Pallas, 1766) as indicator of recreational diving impact on coralligenous reef communities

Recreational diving effects on Mediterranean benthic communities have been scarcely studied to date. In this study, we evaluate the recreational diving impact on the Mediterranean bryozoan Myriapora truncata. Eight localities with different diving rates and protection levels were sampled before and after summer, the season of maximum presence of divers in the region. A photographic sampling technique was used, which made possible to increase the number of replicates. In each sample: number; mean, maximum and total area; total and mean perimeter and exposure; and aggregation levels of M. truncata colonies were measured by image treatment software. ANOVA, MDS and PERMANOVA were the statistical techniques used to detect and evaluate the effects of the five factors considered (time, protection, impact, locality and site) on M. truncata colonies. The number, area and perimeter of colonies significantly decreased after summer at localities with high presence of divers; whereas hidden colonies went through a positive increase comparing with exposed colonies. Our results evidence M. truncata as a good indicator species for recreational diving impact on coralligenous reef communities. The monitoring of a combination of representative parameters of this species could play an important role on the management of diving areas.

Biogeographical and ecological patterns in bryozoans across the Cretaceous-Paleogene boundary: Implications for the phytoplankton collapse hypothesis

Research Article| June 01, 2013 Biogeographical and ecological patterns in bryozoans across the Cretaceous-Paleogene boundary: Implications for the phytoplankton collapse hypothesis Caroline E. Sogot; Caroline E. Sogot 1Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK2Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK Search for other works by this author on: GSW Google Scholar Elizabeth M. Harper; Elizabeth M. Harper 1Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK Search for other works by this author on: GSW Google Scholar Paul D. Taylor Paul D. Taylor 2Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK Search for other works by this author on: GSW Google Scholar Author and Article Information Caroline E. Sogot 1Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK2Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK Elizabeth M. Harper 1Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK Paul D. Taylor 2Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK Publisher: Geological Society of America Received: 06 Sep 2012 Revision Received: 21 Dec 2012 Accepted: 04 Jan 2013 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2013 Geological Society of America Geology (2013) 41 (6): 631–634. https://doi.org/10.1130/G34020.1 Article history Received: 06 Sep 2012 Revision Received: 21 Dec 2012 Accepted: 04 Jan 2013 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Caroline E. Sogot, Elizabeth M. Harper, Paul D. Taylor; Biogeographical and ecological patterns in bryozoans across the Cretaceous-Paleogene boundary: Implications for the phytoplankton collapse hypothesis. Geology 2013;; 41 (6): 631–634. doi: https://doi.org/10.1130/G34020.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The hypothesized collapse in primary productivity associated with the Cretaceous-Paleogene (K-Pg) mass extinction would have been particularly severe on suspension feeders dependent on phytoplankton. Previous research on the ecological dynamics of erect bryozoans in the Danish Basin supported the phytoplankton crash hypothesis in showing a major postextinction increase in the skeletal biomass of cyclostome bryozoans relative to the more nutrient-demanding cheilostome bryozoans. New data on the ecological dynamics between these two bryozoan clades across the K-Pg boundary are provided to determine whether the postextinction cyclostome spike is also evident in encrusting bryozoans and over a greater geographical area. Changes across the K-Pg were quantified in encrusting bryozoans using three metrics: (1) abundance of colonies; (2) area of substrate covered; and (3) colony form. Data from the southeastern United States were added to those from Denmark to control for regional factors. Our analyses indicate a globally uniform change among encrusting bryozoans but without the strong postextinction cyclostome spike seen previously in Danish erect bryozoans. An increased proportion of sheet over runner cyclostome colonies was found in the lower Danian of Denmark and the southeastern United States, despite the expectation that runners with widely dispersed zooids should fare better in low nutrient conditions. Furthermore, weighed samples of erect bryozoans from the basal Danian of Maastricht (Netherlands) and the southeastern United States failed to reveal a strong cyclostome spike. These findings question the phytoplankton crash hypothesis, or at least the extent to which this kill mechanism influenced suspension feeders during the K-Pg mass extinction. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Role of the sea anemone Metridium senile in structuring a developing subtidal fouling community

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 421:139-149 (2011) - DOI: https://doi.org/10.3354/meps08838 Role of the sea anemone Metridium senile in structuring a developing subtidal fouling community Matthew L. Nelson, Sean F. Craig* Department of Biology, Humboldt State University, 1 Harpst St. Arcata, California 95521, USA *Corresponding author: Email: sfc4@humboldt.edu ABSTRACT: In a variety of ecological settings, individual species have been shown to possess the ability to influence the structure and development of the community at large. However, within fouling communities, the influences of many sessile invertebrate species and how they drive patterns of succession remain relatively unexplored. The sea anemone Metridium senile is ubiquitous in cold temperate fouling communities, but its role within these communities has largely been overlooked. Natural fouling communities that had formed on plastic experimental panels were ‘gardened’ to form treatments containing only M. senile, compound ascidians, or erect bryozoans. These panels were deployed under floating docks and were surveyed photographically over 4 mo. M. senile maintained more free space through time within its experimental treatment community than did organisms contained within the other 2 (ascidian or bryozoan) treatments. Subsequent short-term field experiments on recruitment concluded that the presence of M. senile in fact enhances recruitment rates among fouling organisms (relative to controls), ruling out larval predation and larval avoidance as a cause for observed long-term patterns. However, when M. senile were placed upon panels containing natural recruitment in laboratory tanks, it was shown that the anemone ‘smothers’ the majority of these new recruits by sliding over them with its pedal disk, killing all other potential space occupiers and thereby generating increased free space. This study illustrates how a single species can have multiple, opposing influences on patterns of succession at different temporal scales. KEY WORDS: Fouling community · Metridium senile · Recruitment · Succession Full text in pdf format PreviousNextCite this article as: Nelson ML, Craig SF (2011) Role of the sea anemone Metridium senile in structuring a developing subtidal fouling community. Mar Ecol Prog Ser 421:139-149. https://doi.org/10.3354/meps08838 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 421. Online publication date: January 17, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

ENVIRONMENTAL CONTROLS ON THE DISTRIBUTION OF LATE PALEOZOIC BRYOZOAN COLONY MORPHOTYPES: AN EXAMPLE FROM THE PERMIAN OF TASMANIA, AUSTRALIA

Paleozoic bryozoans differ significantly from modern forms in systematics and form, and in strength and occurrence of morphotypes. Nevertheless, the distribution of bryozoan morphotypes in modern oceans is often applied to the interpretation of fossil depositional environments. This study assesses the dominance of bryozoan morphotypes in the upper Paleozoic glaciomarine Tasmania Basin, and determines the environmental parameters that control their distribution by comparison with the environmental distribution and life habit of co-occurring brachiopod and bivalve biotas. Common Tasmanian late Paleozoic bryozoan morphotypes are erect-rigid fenestrate, erect-rigid branching, and erect-rigid foliose, with impersistent occurrences of encrusting forms. Water energy, or turbulence, is the primary control on bryozoan occurrence, with erect-rigid fenestrates occuring in low-energy settings, similar to reclining productid brachiopods, and erect-rigid foliose and branching forms in low- to moderate-energy settings, similar to nestling spiriferids. The secondary environmental parameter controlling bryozoan distribution is sediment accumulation rate. Both brachiopods and bryozoans need to keep their lophophores clear of sediment particles and are usually assumed to indicate low water turbidity. Differential epifaunal tiering, however, allows erect bryozoans to inhabit settings where sediment accumulation rates are sufficient to bury primary tier brachiopods at the sediment surface. With the caveat that water energy levels must remain at low-to-moderate levels, erect-rigid bryozoans are capable of dominating onshore settings where sedimentation rates may prohibit brachiopod dominance. The distribution of late Paleozoic bryozoan morphotypes examined here differs from modern distributions.

Interaction between the invasive macroalga Lophocladia lallemandii and the bryozoan Reteporella grimaldii at seagrass meadows: density and physiological responses

Invasive epiphyte Lophocladia lallemandii macroalga induces changes in the erect bryozoan Reteporella grimaldii at shallow Posidonia oceanica meadows at a Mediterranean pristine location. Bryozoan densities at noninvaded seagrass plots (88.32 ± 3.11 colonies m−2) are higher than those at invaded plots (13.39 ± 1.09 colonies m−2) with a fourfold decrease in number of colonies. Activation of enzymatic pathways (catalase, superoxide dismutase, glutathione peroxidase) and increase in lipid peroxidation malondialdehyde (MDA) [0.80 ± 0.06 nmol/mg prot at Posidonia oceanica plots to 1.08 ± 0.04 nmol/mg prot at L. lallemandii (P < 0.05)] is observed on sessile bryozoans as response to anoxia caused by L. lallemandii. δ13C of bryozoan isotopic composition differed among treatments, covering a broad range (−19.30‰ invaded to −2.84‰ at noninvaded plots), suggesting modification of food sources. Induced shifts of a filter-feeding erect bryozoan by dense algal turfs at invaded seagrasses are demonstrated, highlighting the need to further address interaction across natural communities and alien species invaded systems before further cascade effects are driven.

Morphology of the larva and ancestrula of Myriapora truncata (Bryozoa, Cheilostomatida)

During an essay to rear in aquarium some colonies of the Mediterranean erect bryozoan Myriapora truncata (Gymnolaemata, Cheilostomatida, Ascophorina, Myriaporidae) it was possible to study its larval and ancestrular morphology by scanning electron microscope (SEM) and by light microscope. The different phases of metamorphosis, giving origin to the preancestrula and the ancestrula, were also investigated. The larva of M. truncata is short‐lived, lecithotrophic, and of the coronate type, with expanded corona and small pallial sinus (AEO/ps type, according to Zimmer & Woollacott; VB type, according to d'Hondt). Its morphology, life and metamorphosis appear very similar to those of other well described cheilostome larvae (Neocheilostomida sensu d'Hondt). But, unlike in the other known species of this group, the ancestrula derived from metamorphosis is an ‘ancestrular twin’, in which two zooids simultaneously develop; these can form in two possible reciprocal orientations (same—ipsolateral—or opposite—contralateral—in the direction of growth).

Age, growth and carbonate production by erect rigid bryozoans in Antarctica

Well-calcified marine bryozoans are often important producers of temperate and polar shelf carbonate sediments. In cold waters, bryozoans can be long-lived, and their skeletons therefore reflect many years of growth and carbonate production. This study examines growth, age, and calcification in 12 specimens of three species of cheilostomate Antarctic bryozoans from the Ross Sea (77° 53.394′ S and 166° 40.286′ E, 500 m water depth). Cellarinella nutti and C. nodulata, erect branching bryozoans in the family Sclerodomidae, reached a maximum age of 18 years, grew 1 to 8 mm/year and added new carbonate at a rate of 3 to 57 mg/year. Swanomia belgica, family Cellariidae, reached a maximum age of 23 years, added to branch length at 1 to 4.4 mm/year and calcified at 1 to 23 mg/year. Antarctic bryozoans can be quite long-lived (up to 50 years), but they exhibit slower growth rates than their temperate counterparts, perhaps due to the shortness of the growing season. Seasonal growth checks in many erect Antarctic bryozoans may result from low food availability in winter. There is a clear relationship between growth rate and age, where the polar cellariid bryozoans that live the longest are the slowest-growing. The combination of slow growth, long life-spans, and seasonal growth checks make Antarctic erect bryozoans excellent recorders of environmental conditions and benthic calcification. Calcification rates in Antarctic cellarinellids are generally low: 10–20 g CaCO 3/year, with sedimentation rates of about 0.3 to 1.0 g CaCO 3/m 2/year. Carbonate sediments in which bryozoans are a significant component must accumulate at slow rates in the Antarctic.

Spatial variability ofPosidonia oceanica(L.) Delile epiphytes around the mainland and the islands of Sicily (Mediterranean Sea)

AbstractThis paper investigates patterns of variability in epiphytes ofPosidonia oceanicaleaves at various spatial scales around Sicily, including geographical differences among the Mediterranean basins, differences between the small islands and mainland, and the variability among and within replicated meadows in each of the previous conditions. Data on percentage cover of the most common epiphytic organisms were analysed by univariate techniques. Encrusting red algae, encrusting brown algae, filamentous algae, encrusting bryozoans, erect bryozoans, hydroids and Foraminifera were the most abundant taxa. Significant differences in the abundance of taxa were detected among geographical regions, while no significant differences were found between the islands and mainland. At smaller scales, variability was concentrated mostly among leaves 100s of centimetres apart and among meadows a few kilometres apart. These results suggest that both geographical and local processes are important in structuring the epiphytes ofP. oceanicaleaves in this area of the Mediterranean.

Diversity, structure and interactions of encrusting lithophyllic macrofaunal assemblages from Belgica Bank, East Greenland

Drop stones with lithophyllic macrofauna from Belgica Bank, Greenland Sea (79–81°N and 5–17°W) were collected during the Polarstern cruise in August 2000. The investigation focussed on species richness, diversity, abundance, and interactions of organisms colonizing rocks. On 101 stones collected by 10 dredges from nine sites, 113 taxa (58 genera, 38 families, 12 orders and 8 phyla) were recognized. Among the most abundant groups of organisms were foraminiferans, bryozoans and polychaetes, while the least abundant were anthozoans and ascidians. Abundance ranged from 1239 to 11,383 individuals m−2 of rock surface area. Bryozoans were the most species-rich group, while anthozoans and ascidians were represented by the least number of species. Colonization occurred at various topographical levels and was classified into two categories. Stones were classified as primary space and were colonized by erect membranous, erect flexible, erect rigid, and flat encrusting organisms. The second level of colonization by epibionts occurred on erect forms of organisms (e.g. erect bryozoans) and was classified as a secondary space. Species composition and abundance between faunal assemblages of primary and secondary space differed greatly. Colonization occurred only on the top of stones and was considered a special adaptation to avoid burial by sedimentation and to enhance food supply. Only 3% of recruits were involved in any competitive interactions. Competition was considered to be of minor importance in structuring lithophyllic assemblages.

Slow growth of Antarctic bryozoans increases over 20 years and is anomalously high in 2003

Some organisms are particularly appropriate models for investigation of variability in time and space for given environments. The erect bryozoan Cellarinella nutti, an endemic Antarctic species, is one such organism: it is extremely abundant, occurs from the polar front to the Antarctic continental edge, and preserves a clear macroscopic environmental record in its skeleton (growth check lines). We studied variability in the growth of 93 C. nutti individuals at depths between 247 and 414 m, at sites 1, 10, 100 and >1000 km apart in the Weddell Sea, Antarctica. Trawled C. nutti varied from 5 to 23 yr in age, and nearly half the colonies had grown asexually from fragments. We measured the annual growth increments, which ranged from ~18 zooids (8.6 mg dry mass, 0.8 mg ash-free dry mass; Age 1) to ~130 zooids (43 mg dry mass, 2.48 mg ash-free dry mass; Age 20). At 9 yr (the modal age), each C. nutti individual had precipitated >182 mg CaCO3, and by 20 yr nearly 580 mg. C. nutti grows slowly compared with other erect bryozoans, even those in the Antarctic. We found colony and site to be insignificant factors in its growth, despite the large range of distances between sites, but year was highly significant. We found a non-linear increase in growth spanning the last 2 decades that has no obvious relation to El Nino Southern Oscillation (ENSO)-associated environmental fluctuations. In particular we found that growth in 2003 was greater than in any other year measured by a factor of 2. Given its abundance, longevity, ubiquity in Antarctic waters, insignificant spatial variability in growth, but distinct annual variability, C. nutti may prove to be an important species to investigate whether benthic organisms, as well as krill, salps and fur seals, are beginning to develop major climate-related changes in phenology.

POSITIVE INTERACTIONS BETWEEN NONINDIGENOUS SPECIES FACILITATE TRANSPORT BY HUMAN VECTORS

Numerous studies have shown how interactions between nonindigenous spe- cies (NIS) can accelerate the rate at which they establish and spread in invaded habitats, leading to an invasional meltdown. We investigated facilitation at an earlier stage in the invasion process: during entrainment of propagules in a transport pathway. The introduced bryozoan Watersipora subtorquata is tolerant of several antifouling biocides and a common component of hull-fouling assemblages, a major transport pathway for aquatic NIS. We predicted that colonies of W. subtorquata act as nontoxic refugia for other, less tolerant species to settle on. We compared rates of recruitment of W. subtorquata and other fouling organisms to surfaces coated with three antifouling paints and a nontoxic primer in coastal marinas in Queensland, Australia. Diversity and abundance of fouling taxa were compared between bryozoan colonies and adjacent toxic or nontoxic paint surfaces. After 16 weeks immersion, W. subtorquata covered up to 64% of the tile surfaces coated in antifouling paint. Twenty-two taxa occurred exclusively on W. subtorquata and were not found on toxic surfaces. Other fouling taxa present on toxic surfaces were up to 248 times more abundant on W. subtorquata. Because biocides leach from the paint surface, we expected a positive relationship between the size of W. subtorquata colonies and the abundance and diversity of epibionts. To test this, we compared recruitment of fouling organisms to mimic W. subtorquata colonies of three different sizes that had the same total surface area. Sec- ondary recruitment to mimic colonies was greater when the surrounding paint surface contained biocides. Contrary to our predictions, epibionts were most abundant on small mimic colonies with a large total perimeter. This pattern was observed in encrusting and erect bryozoans, tubiculous amphipods, and serpulid and sabellid polychaetes, but only in the presence of toxic paint. Our results show that W. subtorquata acts as a foundation species for fouling assemblages on ship hulls and facilitates the transport of other species at greater abundance and frequency than would otherwise be possible. Invasion success may be increased by positive interactions between NIS that enhance the delivery of prop- agules by human transport vectors.