Weighted and unweighted power mean methods are compared against the accuracy of the simple arithmetic average to estimate an equivalent sandgrain roughness parameter ($k_{s}$) for streamwise-heterogeneous rough surfaces. Specifically, these methods are conceptually and iteratively tested on roughness plates with surface characteristics following beta ($\beta$), uniform or Gaussian distributions. The sandgrain roughness computed using these averaging methods, $k_{s_{eq}}$, is then compared with true parameters, $k_{s_{eff}}$, estimated from the fully rough asymptote model and a modified momentum integral method that accounts for the streamwise variation of skin friction over the heterogeneous surface. The weighted power mean offers significant advantages, particularly for roughness in $\beta$ distribution, which is attributed to the distribution bias towards smaller magnitudes of $k_s$. While the advantage of using the weighted power mean over the unweighted power mean is less significant for the other surface distributions, the weighted method consistently yields the lowest discrepancy in effective drag estimates, independent of roughness configuration, and is therefore the recommended method for estimating the effective sandgrain roughness across heterogeneous surfaces.

Ficopomatus uschakovi has been reported in Galveston Bay (GB), Texas, USA, in taxonomic lists and studies of biofouling communities since 2017; however, after 2 years (from 2022 to 2024) of no observations of this species in the system, we report the first seasonal outbreak after the landfall of Hurricane Beryl in the summer of 2024, followed by 2 weeks of heavy rain, decreasing the salinity at the collection site. In this study, we provide the first genetic characterization of the specimens of F. cf. uschakovi from GB using mitochondrial cytochrome oxidase b DNA sequence data. Results demonstrated that specimens of F. cf. uschakovi in GB belong to the same genetic species as reported on both of coasts of Mexico, the Gulf coast of Florida, and Thailand. The presence of shared haplotypes suggests possible initial introduction from Asia and subsequent expansion of F. cf. uschakovi populations. The comparison of the morphological characters with reports from nearby localities showed a variation in the number of rows and spines on the operculum and in the tube colouration. This study highlights the importance of morphological and genetic analysis for reliable identification of invasive species, the need for wide geographical sampling, as well as examinations of the ecological drivers of F. cf. uschakovi outbreaks.

This study presents the first comprehensive annotated checklist of polychaetes collected from floating dock communities across New England and adjacent New York areas, emphasizing the significance of rapid biodiversity assessment surveys in understanding marine biodiversity. With 61% of the identified species classified as cryptogenic, the research highlights the complexity of marine biogeography and the challenges of distinguishing between native and non-native species. The incorporation of DNA barcoding has significantly improved species identification and revealed the presence of cryptic species complexes. The study's findings illustrate the prevalence of tubicolous families (Spionidae, Serpulidae, Sabellidae, and Terebelllidae) that are susceptible to anthropogenic dispersal mechanisms. It also addresses the challenge posed by the high proportion of cryptogenic species, calling for enhanced taxonomic and genetic analyses to resolve their origins and ecological roles. Despite the temporal variation in polychaete composition across years, the absence of distinct community assemblages suggests a level of resilience within floating dock communities. Our study advocates for the continuation and expansion of rapid assessment surveys, coupled with the integration of genetic methodologies, to provide a clearer picture of marine biodiversity.

Microcosmus squamiger, an ascidian with high invasion potential, is recorded for the first time in the Brazilian western Atlantic, between Rio de Janeiro and Espírito Santo. The species was found near ports and marinas, and its introduction may have been favoured by intense nautical activity and climatic events such as La Niña. Coexistence with Microcosmus exasperatus, a morphologically similar species, was observed in all localities where M. squamiger was recorded. This discovery implies that a more rigorous process of species identification is necessary during monitoring activities, given that both species can be easily confused (only the syphon spinules differentiate them) and M. exasperatus is widely distributed with collection records dating back more than half a century on the Brazilian coast. The preference of M. squamiger for colder waters suggests that researchers in the Southeast and South Brazil, Uruguay, and Argentina should closely monitor the arrival and possible environmental impacts of this species. The identification of M. squamiger in locations close to bivalve mariculture areas in Rio de Janeiro raises concern, as the species has the potential to compete with bivalves. This study highlights the importance of continuing to monitor the potential spread and the implications of the introduction of M. squamiger into Brazilian waters, as well as its relationship with M. exasperatus, a species already established in this same region.

Chemically defended benthic macroalgae that dominate shallow, hard bottom communities along the western Antarctic Peninsula support very high densities of mesograzers, particularly amphipods but also small gastropods. Previous studies have demonstrated that the macroalgae and amphipods form a mutualistic relationship. The chemically defended macroalgae provide the amphipods with a refuge from predation while the macroalgae benefit from the amphipods greatly reducing surface fouling by smaller algae. One of the three most important macroalgae in terms of overstory cover, Himantothallus grandifolius, forms huge blades that can carpet the benthos. Field observations suggest that gastropods may be higher in relative abundance in proportion to amphipods on H. grandifolius than on other overstory macroalgae. The present study documents the finding that natural abundances of gastropods on H. grandifolius maintained in mesocosms reduce fouling by microscopic algae, primarily diatoms. However, amphipods are probably also important in keeping the macroalga clean of diatoms in nature. In a smaller scale experiment, three gastropod species were differentially effective at reducing diatom coverage on H. grandifolius. The hypothesis that gastropods benefit from associating with H. grandifolius in potentially gaining a refuge from sea-star predation was also tested but not supported by the experimental results.

Surface physical properties, hydrodynamics, biochemical cues, orientation and temporal scales play an important role in invertebrate larval recruitment on artificial substrates. In the present study, invertebrate recruitment on four different substrates (acrylic, stainless steel, ceramic and concrete panels) was investigated in two different orientations (vertical and horizontal) in the central Red Sea. Results showed significant variations in the abundance of benthic invertebrates between the different substrates. While barnacles and bivalves preferred panels placed in vertical positions, the abundance of bryozoans was high on horizontal panels. Artificial panel submersion season plays a significant role in the recruitment of benthic invertebrates on surfaces in the Red Sea. In conclusion, this study supports the overall notion that marine invertebrate recruitment on hard substrates is regulated by a combination of factors which include substrate type, orientation and submersion season.

We report, for the first time, the occurrence of the muzzled blenny, Omobranchus punctatus, on the coast of São Paulo, South-Eastern Brazil, partially filling a record gap within the species’ expected distribution in Brazil. One individual was found on 16 June 2014 in a sand-bottom tide pool of a tidal flat ecosystem, adjacent to the port of São Sebastião.

The diversity and distribution of polychaete species under the families Nereididae, Syllidae and Eunicidae in sub-tidal fouling assemblage was studied by submerging wood as test substratum. Wooden panels were fitted onto a raft and submerged in Kudankulam coastal waters (south east coast of India) in pre-monsoon, monsoon and post-monsoon seasons from May 2003 to July 2005. Panels (in replicate) were retrieved from the raft at 15-day intervals. A total of 24 polychaete species belonging to the three families were identified from the test panels. Perinereis cultrifera, Platynereis dumerilii, Syllis variegata, Syllis truncata, and Eunice australis were the dominant species observed on the test panels. The abundance of major polychaete group was varied considerably between the panel series submerged in May 2003 (post-monsoon), November 2003 (monsoon) and July 2004 (pre-monsoon). The major difference in the polychaete community structure was the low abundance of both nereidids on pre-monsoon season panels and the eunicids on monsoon and post-monsoon season panels.

The structure of sessile epibiotic assemblages fouling the shells of farmed populations of the common Mediterranean mussel Mytilus galloprovincialis, a species known to be involved in ecosystem engineering processes, was investigated in the north Aegean Sea. Mussel samples were collected from three aquaculture installations and all sessile organisms were examined. Fifteen species were recorded, one macroalga and 14 macro-invertebrates. Four colonial species covered up to 20% of the mussel shell. Among solitary organisms, polychaetes dominated followed by barnacles. The diversity of sessile epibionts associated with farmed mussel populations was comparable to that observed on natural mussel beds in contrast to their abundance/cover, which was higher in the former, possibly due to the higher trophic status in the farming areas. The structure of epibiotic assemblages exhibited limited variability at the spatial scale, in general. On the contrary, strong temporal variability with decreased diversity and abundance/cover values during the cold period of the year was assessed, in accordance with the life cycles of species involved and prevailing environmental conditions. Mussel epibionts appeared to have a negative impact on their basibiont since a reduced condition index was detected; however this impact was rather weak and further data are required to generalize the consequences of epibiosis on farmed mussels.

Here we report on the first record of the family Microzoanthidae (Cnidaria: Anthozoa: Hexacorallia) from Palau, and by extension in Micronesia. Unusually, the species Microzoanthus kagerou was found not in a coral reef environment as has been previously reported elsewhere, but instead inhabiting shaded seawater outflow pipes at the Palau Maricultural Developmental Center on Malakal Island, Koror.

The twin-island state of Trinidad and Tobago has a thriving yachting industry with numbers of leisure craft having increased 10-fold from 1980 to 2000. Being geographically outside of the hurricane belt, the islands offer a prime hurricane Caribbean shelter with excellent boating and repair facilities. The Chaguaramas coastline (on the north-west peninsula) has seven (7) anchorages. One of these (the Chaguaramas Bay) was the study site for a survey of hull foulers on recreational boats. In that survey, twenty-seven (27) recreational vessels were sampled for biofoulers, one group being the Tunicates (Ascidiacea). In Trinidad and Tobago little is known about these organisms. Of the eighteen species (18) collected, eight (8) were solitary species and ten (10) were colonial species. Their distribution (all species collected) is wide and they can be found throughout the western Atlantic, the eastern Mediterranean and the Indian Ocean. This survey is a preliminary one in terms of the ascidian fauna of Trinidad and represents only one (1) sampled habitat (boat hulls). There has however been a previous survey of the Tobago fauna. For completeness, there should be a full survey of the ascidians along Trinidad's coastline including their various habitats (rocky shores, mangroves, seagrass beds, etc.). These new data could be used to determine those species which occur in natural communities in Trinidad as compared with this survey (fouling community). In this paper these preliminary results are however used for comparison with the Tobago fauna.

Bryozoans are common fouling species present on ships and artificial substrates. A number of projects reporting the presence of bryozoans in Portugal have been carried out in recent years. As part of a field survey to examine and quantify the non-indigenous marine fouling species in several marinas in Portugal, we detected the bryozoan Celleporaria brunnea for the first time. The native range of C. brunnea seems to extend from British Columbia to the Galapagos, Ecuador. Our discovery indicates that this is the first record of C. brunnea across the East Atlantic and the first record of a species in this genus in the north-eastern Atlantic. The fouling nature of Celleporaria brunnea may have facilitated its spread to the western Pacific, the Mediterranean and now the eastern Atlantic from the Americas.

Settlement of the fouling community is generally influenced by the physical, chemical and biological properties of the settling surface. The colour of the substratum may also exert an influence on larval settlement. In the present study, the influence of surface colour on the recruitment of fouling communities was investigated by suspending acrylic panels (red, green, blue, white and yellow) in coastal waters. Results showed that the colour of the substratum plays an important role in the recruitment of sessile species. Recruitment was comparatively high on red and blue coloured surfaces. Barnacle and tubeworm recruitment showed significant variation (Tukey test, P < 0.05) between different coloured surfaces. The significant conclusion of this study is that the colour of the artificial substrata should be taken into consideration when interpreting results from short-term biofouling studies.

Barnacles are the common fouling organisms encountered in coastal waters around the world. In the present study, breeding biology of the intertidal barnacle Amphibalanus amphitrite (=Balanus amphitrite) was studied for a period of two years (July 2003 to June 2005) in the Kudankulam coastal waters. Results showed that A. amphitrite breeds throughout the year in the study area. A high percentage of individuals with free nauplii in the mantle cavity was observed during March 2004 (47.6%) and May 2004 (41.7%). Barnacles with fertilized eggs in the ovary were high during November 2004 (56%), March 2005 (46.7%) and April 2005 (42.8%). Overall, a peak breeding activity was observed during the March–May period. The breeding activity showed a significant positive correlation with surface water temperature and phytoplankton abundance.

Calcareous tube polychaetes (family Serpulidae) are notorious biofoulers that are easily transported and introduced to allochthonous habitats. Here we report the recent introduction of Hydroides dianthus (Verrill, 1873) to eastern Japan as its first occurrence in East Asia, probably from European or American coasts. Specimens had been found on artificial hard substrata together with congeners H. ezoensis, H. exaltatus and H. fusicolus in Tokyo Bay, Japan in 2006. The origin, vector, source of introduction and possible impact of H. dianthus on Japanese coasts is discussed from a perspective based on worldwide Hydroides transport.

The vertical distribution of fouling communities in Kudankulam coastal waters was studied for a period of one year (January to December 2005) by suspending wooden test panels at 1 m, 4 m and 7 m depths. Panels were submerged on short-term duration (15 days) and long-term basis (cumulative). The fouling organisms observed were barnacles, mussels, ascidians, polychaetes, amphipods and seaweeds. Recruitment was observed on the panels throughout the year with a considerable variation in relation to time and depth. On the short-term series, the fouling biomass varied from 0.218 to 1.23 g.dm−2 (dry wt) at 1 m, 0.23 to 4.72 g.dm−2 (dry wt) at 4 m and 0.241 to 5.66 g.dm−2 (dry wt) at 7 m depths. The biomass of the fouling community that colonized on the long-term panels ranged between 0.79 and 35 g.dm−2 (dry wt) at 1 m, 3.72 and 58.2 g.dm−2 (dry wt) at 4 m and 0.241 and 55.9 g.dm−2 (dry wt) at 7 m depths. At 1 m depth, macro-algae, ascidians (Botryllus tuberatus and Diplosoma sp.) and amphipods were the dominant species. Barnacles, tube worms and ascidians (Didemnum spp.) were abundant on the 4 m and 7 m depth panels. In general, the fouling community recruitment was higher at 4 m than 1 m and 7 m depths.