Epifaunal Assemblages Research Articles

Comparison of epifaunal assemblages betweenCymodocea nodosaandCaulerpa proliferameadows in Gran Canaria (eastern Atlantic)

Epifaunal invertebrates are sensitive to changes in the identity of the dominant host plant, so assessing differences in the structure of epifaunal assemblages is particularly pertinent in areas where seagrasses have been replaced by alternative vegetation (e.g. green seaweeds). In this study, we aimed to compare the diversity, abundance and structure of epifaunal assemblages, particularly amphipods, between meadows dominated by the seagrassCymodocea nodosaand the green rhizophytic algaeCaulerpa proliferaon shallow soft bottoms of Gran Canaria Island, determining whether patterns were temporally consistent between two times. The epifaunal assemblage structure (abundance and composition) consistently differed between both plants, those assemblages associated withC. prolifera-dominated beds being more diverse and abundant relative toC. nodosameadows. Amphipods constituted ~70% of total crustaceans for the overall study, including 37 species belonging to 16 families. The amphipod abundance was ~3 times larger inC. prolifera-dominated beds than inC. nodosameadows. We detected species-specific affinities; for example,Microdeutopus stationis, Dexamine spinosa, Aora spinicornis, Ischyrocerus inexpectatusandApherusa bispinosawere more abundant inC. prolifera-dominated beds; while the caprellidMantacaprella macaronensisdominated inC. nodosameadows. However, some species, such asPseudoprotella phasmaandAmpithoe ramondi,were found in both habitats with varying abundances between times.

Biodiversity patterns of epifaunal assemblages associated with the gorgonians Eunicella gazella and Leptogorgia lusitanica in response to host, space and time

Patterns of biodiversity (α- and β-diversity), abundance and community structure of the epifaunal assemblages associated with two gorgonians, Eunicella gazella and Leptogorgia lusitanica, were analysed in relation to host, colony size, location and time. Colony size and time were the major factors shaping attendant assemblages. Patterns of α-diversity and β-diversity were host-dependent. Assemblages associated with E. gazella showed a significant inter-annual variability for most of the metrics analysed, while in those associated with L. lusitanica only Shannon–Wiener varied significantly between years. In L. lusitanica Hurlbert's expected number of taxa was significantly lower in small-sized than in medium- to large-sized colonies, but an opposite pattern was detected for β-diversity, reflecting the higher heterogeneity among small-sized colonies. The dbRDA analysis segregated the assemblages associated with each of the two hosts; the faunal patterns were mainly explained by colony size related attributes (area, number of branches and, to a lesser extent, width) and the “colonial” epibiont cover. However, we suggest that altogether they may act as a metacommunity, with high temporal and spatial fluidity in their composition and structure related to multiple factors including not only a component of stochasticity but also life history events, biotic interactions and response to habitat heterogeneity and environmental variability.

Effects of temperature on the recruitment phenology and niche overlap of shallow epifaunal assemblages in southern New England

Recruitment phenology, or the timing of recruitment, can have a large influence on individuals and populations by affecting their exposure to adverse environmental conditions and interspecific competition. In this study, we examined whether temperature parameters could predict the timing of recruitment, the duration of recruitment and total recruitment in 18 benthic epifaunal species using partial least squares regression (PLSR) and ordinary least squares regres- sion. Additionally, we used a null model to test whether temperature parameters and inter-annual variation in those parameters affect the temporal niche overlap of these benthic species. We specifically examined the recruitment patterns of non-native species to help illustrate how shifts in phenology may help drive changes in the community composition. Results from the PLSR helped determine the most instructive regressors for univariate least-squares models. For many (14 of 18) of the species examined, recruitment patterns could be predicted by seasonal growing degree days. Additionally, communities at cooler sites exhibited greater temporal niche overlap than assemblages found at warmer sites. Finally, we observed a unique pattern among invasive species, with more recent invaders recruiting later in the season, which may be a result of shifts in niche overlap. The findings of this study illustrate potential mechanisms for species coexistence and increased rates of invasion resulting from climate change.

Changes in biological traits of macro-benthic communities subjected to different intensities of demersal trawling along the west coast of southern Africa

Biological traits analysis (BTA) is considered to be a powerful technique for describing the ecological functioning of marine benthic assemblages. This study is the first to apply BTA to assess differences in the traits of benthic faunal assemblages between areas exposed to heavy and light trawling in a major upwelling ecosystem along the west coast of southern Africa. The data were collected from two sampling locations in Namibia and six sampling locations in South Africa. The intensity of trawling varied from area to area. Significant differences in biological traits (BT) were detected between heavily and lightly trawled areas. Weighted infaunal traits showed significant differences between heavily and lightly trawled areas for 17% of the traits investigated, while 24% of epifaunal traits investigated were significantly different between areas of different trawling intensities. This suggests that the measured BTs of the epifauna might be more sensitive to trawling disturbances than BTs of the infauna. The infaunal traits differed significantly between areas with larger or smaller proportions of sand and mud. Nevertheless, more of the significant differences in infaunal BTs were related to variations in trawling intensity than to variations in sediment composition. Significant modifications of BTs are likely to lead to modified functioning of the community and provide more general potential indicators for management than those based on species. The study confirms the need for more basic biological and life history data on macro-benthic invertebrates but nevertheless shows that BTA detected specific features that correlate with trawling intensity and that these features may be important for epifaunal assemblage functioning.

Evidence of trawl disturbance on mega-epibenthic communities in the Southern Tyrrhenian Sea

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 475:101-117 (2013) - DOI: https://doi.org/10.3354/meps10115 Evidence of trawl disturbance on mega-epibenthic communities in the Southern Tyrrhenian Sea M. Cristina Mangano1,2,*, Michel J. Kaiser2, Erika M. D. Porporato1, Nunziacarla Spanò1 1Dipartimento di Biologia Animale ed Ecologia Marina, Università degli Studi di Messina 98166, Messina, Italy 2School of Ocean Sciences, Bangor University, LL59 5AB Menai Bridge, Anglesey, UK *Email: mmangano@unime.it ABSTRACT: Bottom trawling has direct impacts on benthic communities. These impacts are modified by the environmental context in which they occur. Communities that occur in habitats subjected to low levels of natural disturbance are considered to be the most vulnerable to bottom trawling. The present study examined the impact of otter trawl fisheries on epifaunal assemblages of the Southern Tyrrhenian Sea (Central Mediterranean Sea), across the continental shelf and down to the meso-bathyal plain. Using a long time-series of non-target epifaunal species collected by experimental otter trawl surveys, differences in assemblage structure and composition were detected among areas that experienced different levels of fishing intensity relative to Fishery Exclusion Zones. Areas that experienced the highest levels of trawling had a significantly lower abundance of crinoids and ophiuroids; the former are important structuring fauna. The epifaunal assemblage composition in the areas that had been subjected to the heaviest levels of fishing activity were characterised by a greater number of scavenging species that are resilient to the effects of fishing. Although the heavily trawled areas had higher diversity than the less heavily fished areas, this was associated with the absence of K-selected species such as crinoids and dominance by r‑selected scavenging biota. KEY WORDS: Trawling · Impact · Disturbance · Crinoids · Continental shelf · Continental slope Full text in pdf format PreviousNextCite this article as: Mangano MC, Kaiser MJ, Porporato EMD, Spanò N (2013) Evidence of trawl disturbance on mega-epibenthic communities in the Southern Tyrrhenian Sea. Mar Ecol Prog Ser 475:101-117. https://doi.org/10.3354/meps10115 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 475. Online publication date: February 14, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Seagrass-epifauna relationships in a temperate South African estuary: Interplay between patch-size, within-patch location and algal fouling

Understanding the primary and interactive effects of patch-size, within-patch location and degree of algal fouling on epifaunal assemblages is important for seagrass ecology and management, especially in fragmented habitats. In this paper we examine the influence of these factors on epifaunal assemblages in the Heuningnes Estuary, which is one of South Africa's oldest protected systems. Multivariate analyses indicated that all seagrass properties significantly affected epifaunal assemblages and that two gastropods viz. Assiminea globulus and Haminoea alfredensis contributed most to the dissimilarities between factors. Abundance of epifauna and A. globulus were significantly greater at the edges of seagrass beds, whereas species diversity was higher in the interior. Differences in assemblage structure between inner cores and outer edges of seagrass beds are most likely due to the physical properties of each of these zones as well as competitive interactions and habitat preferences of species that utilize each section. Epifaunal richness and A. globulus abundance were significantly greater in large beds compared to small ones and the degree of algal fouling on seagrass beds inversely affected epifaunal abundance, species richness and A. globulus abundance. Importantly, there was a strong interaction between within-patch location and patch-size, indicating that the effects of within-patch location can be altered by patch-size. When explored further, ordinations indicated that epifaunal assemblages in cores and edges became more dissimilar as bed size increased. Similarly, differences in epifaunal abundance, and diversity as well as abundance of A. globulus and H. alfredensis between cores and edges of seagrass beds became greater with increasing bed size. Our results indicate the importance of large beds in enhancing spatial heterogeneity, richness and diversity and the need for adequate protection to prevent their fragmentation in future. This is especially pertinent given the small number of large beds currently found in the system. We discuss the importance of current management strategies in the Heuningness Estuary, specifically the artificial maintenance of an open mouth state, in the persistence of large seagrass beds in the system.

Epifaunal and algal assemblages associated with the native Chondrus crispus (Stackhouse) and the non-native Grateloupia turuturu (Yamada) in eastern Long Island Sound

Although the spread of non-native algae is rapidly escalating, relatively few ecological studies have been done to gauge the impacts incurred to native flora and fauna. A reduction in the dominance of a native habitat-forming macroalga due to the replacement by an introduced species can have adverse effects on the community. The non-native red alga Grateloupia turuturu, first reported in Rhode Island, USA in 1994, has since extended its southern range into eastern Long Island Sound. This large alga has the potential to impact coastal communities by altering the floristic composition important to associated flora and fauna. A comparison of algal and epifaunal assemblages was made during 2006 and 2007 between native and non-native algal communities dominated by either G. turuturu or the native, Chondrus crispus at two sites in Long Island Sound. We found that within Grateloupia-dominated habitat, there was a large decrease in overall macrophyte biomass as compared to native habitat. We also found that habitat dominated by the non-native alga reduced species richness and total abundance of invertebrates relative to nearby habitats dominated by C. crispus. In addition, we found that the dominant mesofaunal species, important to higher trophic level consumers, had greatly reduced densities in communities dominated by the non-native alga.

Spatial patterns and environmental correlates in leaf-associated epifaunal assemblages of temperate seagrass (Zostera marina) meadows

We estimated and tested variability of seagrass leaf-associated epifaunal assemblages at a range of scales. Sampling was performed in 36 seagrass (Zostera marina) meadows within three regions along the Swedish west coast following a hierarchical design (samples separated by 10 s m, km or 100 km). Results showed strongest variability (43–81%) at the intermediate amongst-meadow (km) scale using biomass of functional categories, while considering taxa composition the within-meadow (10 s m) scale contributed most to variability (60%). Using functional categories, we found that embayment exposure and seagrass shoot density were the most important predictor variables explaining part of the variability in biomass of suspension feeders (bivalves and barnacles) and grazers. In contrast, variability in epifaunal taxa composition was predicted mainly by sediment chemistry, substratum coverage and geographical positioning. Our findings suggest that models to develop predictive power and mechanistic understanding should focus on variables and processes varying at small and intermediate scales rather than those varying at larger scales.

The long-term impacts of fisheries on epifaunal assemblage function and structure, in a Special Area of Conservation

Fisheries can have profound effects on epifaunal community function and structure. We analysed the results from five dive surveys (1975–1976, 1980, 1983, 2003 and 2007), taken in a Special Area of Conservation, Strangford Lough, Northern Ireland before and after a ten year period of increased trawling activity between 1985 and 1995. There were no detectable differences in the species richness or taxonomic distinctiveness before (1975–1983) and after (2003–2007) this period. However, there was a shift in the epifaunal assemblage between the surveys in 1975–1983 and 2003–2007. In general, the slow-moving, or sessile, erect, filter-feeders were replaced by highly mobile, swimming, scavengers and predators. There were declines in the frequency of the fished bivalve Aequipecten opercularis and the non-fished bivalves Modiolus modiolus and Chlamys varia and some erect sessile invertebrates between the surveys in 1975–1983 and 2003–2007. In contrast, there were increases in the frequency of the fished and reseeded bivalves Pecten maximus and Ostrea edulis, the fished crabs Cancer pagurus and Necora puber and the non-fished sea stars Asterias rubens, Crossaster papposus and Henricia oculata between the surveys in 1975–1983 and 2003–2007. We suggest that these shifts could be directly and indirectly attributed to the long-term impacts of trawl fishing gear, although increases in the supply of discarded bait and influxes of sediment may also have contributed to changes in the frequency of some taxa. These results suggest that despite their limitations, historical surveys and repeat sampling over long periods can help to elucidate the inferred patterns in the epifaunal community. The use of commercial fishing gear was banned from two areas in Strangford Lough in 2011, making it a model ecosystem for assessing the long-term recovery of the epifaunal community from the impacts of mobile and pot fishing gear.

Effects of demersal trawling along the west coast of southern Africa: multivariate analysis of benthic assemblages

This study is the first to examine the benthic impacts of the otter-trawl fishery on hake in the southern Benguela upwelling region. Infauna were sampled at 4 sites, from southern Namibia to Cape Town by means of 5 replicate grab samples at each of 2 trawling treatments (heavily and lightly trawled areas), paired at each site. The large invertebrate epifauna was also sampled at 2 of these sites using a fine-meshed otter trawl. Sites ranged in depth from 350 to 450 m. Environmental attributes (sediment particle size, total organic carbon, depth, salinity, temperature and dissolved O2 concentra- tion) were examined along with faunal assemblage composition. Vertical profiles of water mass char- acteristics showed little long-shore variation, apart from slightly lower O2 concentrations in the north. Difficulties of pseudo-replication in benthic impact studies are discussed, and methods for circumvent- ing these suggested. There were significant differences in sediment characteristics among the 4 sites, but only 2 sites showed different sediment characteristics between trawling treatments. Studies of spe- cies richness, evenness and numbers of infaunal individuals showed little difference between trawling treatments at 3 sites and species diversity was similar between treatments at all 4 sites. Multivariate analyses show marked differences in both infaunal and epifaunal assemblages among the sites and between trawling treatments at all sites. The analyses suggest that differences in trawling intensity are at least partially responsible for significant variation in benthic assemblage composition between heavily and lightly trawled areas. These findings contrast to those in shallower waters in the northern hemisphere, where infauna are more sensitive to trawling than epifauna. This study shows that epifau- nal abundances, number of species and species diversity decrease with increasing trawling intensity, and that there are also considerable changes in epifaunal assemblages in more heavily trawled sites.

Effects of macroalgal identity on epifaunal assemblages: native species versus the invasive species Sargassum muticum

Seaweeds are a refuge from stressful conditions associated with life on rocky intertidal shores, and there is evidence that different macrophytes support different assemblages of mobile epifauna. Introduction of non-indigenous macroalgae may have a great impact on associated epifaunal assemblages and ecosystem processes in coastal areas. Previous studies have reported conflicting evidences for the ability of epifauna to colonize non-indigenous species. Here, we analyzed epifaunal assemblages associated with three species of macroalgae that are very abundant on intertidal shores along the Galician coast: the two native species Bifurcaria bifurcata and Saccorhiza polyschides and the invasive species Sargassum muticum. We collected samples of each species from three different sites at three different times to test whether variability of epifaunal assemblages was consistent over space and time. Epifaunal assemblages differed between the three macroalgae. Results suggested that stability and morphology of habitat played an important role in shaping the structure of epifaunal assemblages. This study also showed that the invasive S. muticum offered a suitable habitat for many invertebrates.

Utilisation of the Invasive Alga Caulerpa taxifolia as Habitat by Faunal Assemblages in the Port River–Barker Inlet Estuary, South Australia

The epifaunal and infaunal assemblages associated with Caulerpa taxifolia in the Port River/Barker Inlet estuary of Adelaide, South Australia were compared to those associated with the co-occurring seagrass Zostera muelleri. Both taxa contained an abundant and diverse fauna, but with substantial differences between them. In particular, ophiuroids (brittle stars) were abundant in Caulerpa, but almost absent from Zostera. Crustaceans, mostly amphipods, and annelids, mostly polychaetes, were abundant in both Caulerpa and Zostera, but the families present differed substantially. Taxa that dominated in Caulerpa include the amphipods: Amphithoidae, Corophiidae, and Talitridae; and the polychaetes: Cirratulidae, Nephtyidae, and Nereididae. Zostera was dominated by the polychaetes: Capitellidae; amphipods: Caprellidae; isopods: Sphaeromatidae; and Neballidae. Some taxa (arthropods, nemerteans, and echinoderms) had their peak abundance during summer, when Caulerpa biomass was highest, while others did not seem to respond to changes in Caulerpa biomass. Overall, epifauna were 4–9 times more abundant in Caulerpa than Zostera, while infauna were slightly more abundant in Zostera, indicating that at least in South Australia, Caulerpa provides a functional habitat for a diverse array of taxa.

Environmental effects of yellowtail kingfish aquaculture in South Australia

The culture of yellowtail kingfish Seriola lalandi in South Australia is one of the most rapidly growing aquaculture sectors in Australia. To date, there is a paucity of information on the environmental impacts of this industry, due to its relatively small size in comparison to other industry sectors. Here, we report on a study examining the response of a range of environmental variables to yellowtail kingfish aquaculture in Fitzgerald Bay, northern Spencer Gulf, South Australia. The clearest response occurred in several chemical variables, with an 81% increase in ammonia con- centrations adjacent to cages relative to controls, increased sediment organic carbon (7 to 46%) and increased porewater phosphorus in the sediments (80 to 3077%). While there were also statistically significant effects on infaunal and epifaunal assemblages, results for both groups were equivocal because of high small-scale variability. For the infauna, assemblages at the sites furthest from cages tended to be similar to those adjacent to cages, while those at intermediate distances differed. No impacts were detected on phytoplankton, or on seagrasses (although the latter only occurred >250 m from any aquaculture cage). The lack of clear responses in the biotic datasets is probably related to the relatively low production levels (<2000 t yr -1 at the time of the study), although the responses in the chemical variables provide a valuable early warning as production increases.

Biogeography of the Lord Howe Rise region, Tasman Sea

The two principal aims of this study were to synthesise physical and biological information to characterise the Lord Howe Rise (LHR) region and to use recent survey collections of benthic invertebrates (mostly large benthic epifauna) to describe its biogeography at regional and sub-regional scales. The LHR region is large (1.95 million km 2), spans tropical and cool temperate latitudes (18.4 to 40.3°S), and is influenced by several ocean currents, notably the East Australian Current and the Tasman Front. Our analyses revealed that biological patterns were related to two groups of geomorphic morphotypes found in this topographically complex region: subdued bathymetric features (expansive soft sediment basins and plateaus) and raised bathymetric features (scattered seamounts, guyots, knolls, and pinnacles). Raised bathymetric features in the LHR region were more likely to support richer and more abundant epifaunal assemblages dominated by suspension feeding invertebrates on hard substrata compared to subdued features which were dominated by infauna and detritivores in soft sediments. However, this trend does not apply to all raised bathymetric features (e.g., Gifford Guyot), with variations in depth, elevation, latitude, and particularly substrata affected the composition of biological assemblages. In addition, some demersal fishes, ophiuroids, and other benthic invertebrates showed distinct north-south delineations that coincide with the influence of the Tasman Front and thermal gradients. While the lack of spatially- and temporally- replicated data in the region limits our interpretation of survey data, paleo-environmental processes and examples from other regions provide some indication of how dispersal influences migration, speciation, and endemism in the LHR region. Although our current knowledge is limited, it is hoped that this review will help inform future studies in the area, as equitable examination of biological, geological, and oceanographic characteristics will facilitate future assessments of LHR biogeography and permit the inclusion of this region in biogeographic studies with a national or global context.

Benthic environments of the Lord Howe Rise submarine plateau: Introduction to the special volume

The Australian exclusive economic zone (EEZ) contains1.6 million km 2 of submarine plateaus, equal to about 13.8% of the world's known inventory of these features. This disproportionate occurrence of plateaus presents Australia with an increased global responsibility to understand and protect the benthic habitats and associated ecosystems. This special volume presents the results of two major marine surveys carried out on the Lord Howe Rise plateau during 2003 and 2007, during which benthic biological and geological samples, underwater photographs, video and multibean sonar bathymetry data were collected. The benthic habitats present on Lord Howe Rise are dominated by slowly-accumulating, low-energy, soft-sediment habitats, but also include hard/rocky substrates covering a small area of volcanic peaks (around 31 km 2) and parts of other larger seamounts (e.g., the Lord Howe Island seamount) which support rich and abundant epifaunal assemblages dominated by suspension feeding invertebrates. These rocky habitats appear to qualify as ecologically and biologically significant areas under the United Nations Convention on Biological Diversity (CBD) scientific selection criteria 1 (uniqueness or rarity), 4 (vulnerability, fragility, sensitivity or slow recovery) and 7 (naturalness). The collection of papers included in this special volume represents a major advance in knowledge about benthic habitats of the Lord Howe Rise, but also about the ecology of submarine plateaus in general.

Patterns of abundance and assemblage structure of epifauna inhabiting two morphologically different kelp holdfasts

The mobile fauna associated with two sympatric kelp species with different holdfast morphology (Saccorhiza polyschides and Laminaria hyperborea) was compared to test for differences in the assemblage structure of holdfast-associated mobile epifauna. A total of 24,140 epifaunal individuals were counted from 30 holdfasts of each kelp species. Overall epifaunal abundances exceeded faunal abundances previously reported from holdfasts of other kelps. Three taxonomic groups, Amphipoda, Mollusca, and Polychaeta, accounted for ca. 85% of all individuals. Total abundances increased with the amount of habitat available, quantified either as the volume or the area provided by the holdfasts. The multivariate structure of the epifaunal assemblage did not differ between holdfasts of the two kelp species. However, epifaunal assemblages responded differentially to the habitat attributes provided by each type of kelp holdfast: multivariate variation in the assemblage structure of epifauna was mostly explained by holdfast area and volume for L. hyperborea, and by the surface-to-volume ratio for S. polyschides holdfasts. Therefore, the physical attributes of biogenic habitats, here kelp holdfasts that better predict patterns in the assemblage structure of associated fauna can differ according to their different physical morphology, even though the overall assemblage structure of associated fauna was similar.

Biodiversity of epibenthic community in the inshore waters of southeast coast of India

AbstractThe epifaunal assemblage was evaluated at three different depths (5, 15 and 25 m) in the inshore waters of Pazhayar, Parangipettai and Cuddalore apart from 5 m depth near SIPCOT covering totally 10 stations (11°21′ N to 11°42′ N; 79°46′49″ E to 79°52′34″ E) in the southeast coast of India, Bay of Bengal. The occurrence of as many as 112 species belonging to 6 groups was recorded. Among these, gastropods constituted the largest component (42.85%) with 48 species. Bivalves came next with the percentage contribution of 24.10% with 27 species. Crustaceans and polychaetes contributed with 16.96% (19 species) and 6.25% (7 species), respectively. Others contributed with 9.82% (11 species). The maximum number of species was recorded in Cuddalore transect (65 species) and the minimum in SIPCOT (20 species). The maximum abundance was recorded in SIPCOT (1363 ind./haul) but the diversity was found to be lower here than in the other stations. The bivalve, Scapharca inaequivalvis was abundant only in this station whereas the large sized polychaetes, Epidiopatra hupferiana monroi and Sternaspis scutata were found only in the Pazhayar transect during all the seasons. Multivariate analyses were done to define assemblages. The total number of species estimated by various extrapolators varied from 112 species to 169.73 species. The cluster analysis revealed the gradual change in species composition with increase in depth. In the principal coordinate analysis (PCO) the first two axes explained 49.8% of the total variability in the case of biota and 98.3% of the total variability in the case of environmental variables. The distance based linear model (DISTLM) was used to find out the relationship between the abundance of epifauna and environmental variables. Depth explained about 23.7% of the variability while temperature and pH explained 17.5 and 10.6%, respectively. The best solution suggested all the nine environmental variables to combinedly explain about 92.49% of the total variability

Algae as hosts for epifaunal bryozoans: Role of functional groups and taxonomic relatedness

Macroalgae build biogenic habitats which give shelter and provide a suitable physical environment for a great variety of organisms. Structural complexity of algal substrates may influence the composition of their attached epifauna. The aim of this study is to test whether the taxonomic relatedness of the algal hosts and the functional groups to which they belong influence the species richness and composition of their epifaunal bryozoans. We analysed 36 algal genera from the Atlantic coast of South America between 42°S and Cape Horn. Changes in bryozoan species richness (number of species) among different algal functional groups (filamentous algae, foliose algae, corticated foliose algae, corticated macrophytes) were non-significant. The composition of the epifaunal assemblages differed significantly only between filamentous and foliose algae. Sheet-like bryozoans (i.e. encrusting, pluriserial colonies) were more frequent on foliose than on filamentous algae, while runner-like species (i.e. uniserial stolons) were characteristic epibionts on filamentous thallii. Similarity of bryozoan assemblages increased with increasing taxonomic relatedness of their hosts. As most filamentous seaweeds analysed in this study are members of the Order Ceramiales, the influence of algal taxonomic relatedness and functional groups on the composition of their bryozoan assemblages can be viewed as two different aspects of the same phenomenon.

First record of the non-native light bulb tunicate Clavelina lepadiformis (Müller, 1776) in the northwest Atlantic

We report the first record of the colonial tunicate Clavelina lepadiformis (Muller, 1776) in the northwest Atlantic. Populations were found along the eastern Connecticut shoreline in October 2009. At one site C. lepadiformis had a mean percent cover of 19.95% (±4.16 S.E.). A regional survey suggests that the invasion is relatively localized. Genetic analysis confirms our morphological identification and places the introduced population in the previously described ‘Atlantic clade’. While it appears Clavelina lepadiformis is currently in the incipient stage of introduction in eastern Connecticut waters, its spread to other areas in the region could lead to competition with resident members of shallow water epifaunal assemblages and shellfish species.

Effects of habitat structure and tidal height on epifaunal assemblages associated with macroalgae

Patterns of distribution and abundance of epifauna often differ markedly among macroalgal species. The hypotheses tested were that (1) assemblages of mobile epifauna associated with Laminaria ochroleuca and Sargassum muticum differed because they have different structure, and (2) assemblages of mobile epifauna associated with S. muticum differed between heights on the shore because tidal height affects physical and biological conditions. We also investigated the effect of epiphytic biomass on the composition of epifaunal assemblages. Hypotheses were tested with measuring and manipulative experiments using natural and artificial algae, and by measuring uni- and multivariate assemblage descriptors. The results indicated that epifaunal assemblages associated with natural L. ochroleuca and S. muticum differed, but only differences in epifaunal densities were likely to be related to the structure of algae since all other variables did not clearly differ between the two algae. Although structure might play an important role, other factors need to be taken into account and further experimental tests are necessary. Epifaunal assemblages associated with S. muticum did vary depending on the height on the shore, but inconsistently over time in the case of natural algae. In addition, epifaunal densities of natural algae were positively related to biomass of epiphytes in both species. Time of sampling, epiphytic load and height on the shore were the most important factors in structuring epifaunal assemblages rather than complexity of the host algae.