Hydroid assemblages from the Southwestern Atlantic Ocean (34–42° S)

This paper provides updated taxonomic knowledge about hydrozoan species and provides ecological information including geographical and bathymetric distributions and biological substrata for the various hydroid assemblages from the Sub-Antarctic Biogeographical Region, mainly Buenos Aires and the Uruguayan coasts. Five of the 41 species found are new records for the study region. Thirty-one species (75.6%), all found at depths of less than 80 m, have cosmopolitan distributions. Biodiversity decreased markedly below 80 m depth, where nine species (≈22%) distributed in the Southern hemisphere and one endemic species (2.4%) were found. Most species were non-specific epizoites, occurring on diverse substrata. A non-parametric multivariate similarity analysis revealed nine species groups that were correlated with large-scale and local oceanographic patterns and with the availability of suitable substrata. The main hydroid substrata for eight of the groups were cnidarians, molluscs (mainly blue mussels), quartzite rocks and sponges. In a single group found in Patagonian scallop beds, the main biological substrata were polychaete tubes, other hydroids and scallops.     

Hydrozoa (Cnidaria) symbiotic with Porifera: a review

Many hydroids are symbiotic with other organisms. Sponges, because of their complex canal system and their filter‐feeding activity inducing a continuous water flow, are used by numerous species as either exclusive or facultative substrata. The associated hydroid fauna thriving on or inside sponges shows a wide range of relationships with their hosts. Hydroids may be simply epibiotic on sponges, their stolons running on the host surface. Alternatively, the stolons may grow inside the sponge body, the polyps emerging from the sponge surface, having also the possibility of retraction inside the sponge tissue. Finally, stolons and branches may develop deeply inside the sponge body, producing a skeletal network for sponge growth. This paper reviews the described relationships of hydrozoans symbiotic with sponges and reports new observations.     

DNA barcode,taxonomic and ecological notes for the identification of the invasive amphipod Monocorophium acherusicum (Costa, 1851)

We report the occurrence of the invasive amphipod Monocorophium acherusicum in Mar del Plata port, Argentina, using morphological and molecular analysis and estimated mean abundance to detect monthly variations of this population. We compared M. acherusicum morphology with that of M. insidiosum and Crassicorophium bonelli, the two most similar locally occurring species, to establish the diagnostic characteristics for the correct identification of them; moreover, we provide some taxonomic notes about others corophiids regionally distributed. M. acherusicum were collected in a subtidal biofouling community and its mean abundance was maximum in summer. In the molecular analysis, the maximum-likelihood tree showed that specimens from Mar del Plata were clustered with M. acherusicum specimens from GenBank and Boldsystems. We support and confirm the species identity in Mar del Plata port using DNA barcoding and with taxonomic methods.     

Polychaete Associations in a Subtropical Environment (São Sebastião Channel, Brazil): A Structural Analysis

Abstract. Analysis of polychaetes from 60 quantitative soft bottom samples (November 1993 – August 1994) from the São Sebastião Channel at 10 to 45 m yielded 126 species from a total of 12,003 individuals. The distribution of both the bottom sediment type and species was patchy. Abundance data were analysed with multivariate techniques and revealed a strong correlation between species and sediment variables. Polychaetes were more diverse, abundant and richer in species number in those sites with higher sandy fractions. On the other hand, sites where silt, clay and organic carbon predominated showed a poor annelid fauna. Here, pollution by the sewage discharge of a submarine pipe, the oil terminal activities and the clandestine oil tank washing have an important impact on the bottom fauna. Only little temporal variation in the composition of the polychaete associations was found during the study period.     

Polychaete Communities Related to Plant Covering in the Médiolittoral and Infralittoral Zones of the Balearic Islands (Western Méditerranean)

Abstract. The polychaete fauna of the subtidal in the médiolittoral and the infralittoral hard bottom zones of the Balearic Islands at depths from 0 to 40m contained 220 species. Five different polychaete communities could be identified by changes in abundance, species richness, species composition, diversity, and trophic structure. In the very clear waters of these islands the infralittoral zone extends to a depth of 40 m and allows us to investigate whether former proposed models of polychaete distribution can be extended to this particular situation.     

Zonation of dominant fouling organisms on northern gulf of Mexico petroleum platforms

In a study of the fouling communities of petroleum platforms near the Louisiana coast, scraped samples were collected by divers at depths from 1 to 30 m. The main habitat-forming species were barnacles and pelecypods, which accounted for over 99% of the drained weight of the samples. Other abundant forms included ophiuroids, actiniarian and zoanthid anemones, caprellid and gammaridian amphipods, hydroids, bryozoans, tunicates, and clionid sponges. Although the fauna of both nearshore and offshore platforms included many cosmopolitan taxa, a number of tropical species more commonly found on coral reefs were collected on offshore platforms. Algal abundance was higher near the surface, especially at the nearshore platforms, and was higher off shore than near shore at all depths. There was no evidence that a produced water discharge on one of the platforms had any significant effect on community composition a few meters away from the point of discharge, although it was not possible to determine the chemical content of the discharge.     

Intertidal biogenic reefs built by the polychaete Boccardia proboscidea in sewage‐impacted areas of Argentina,SW Atlantic

The rocky intertidal zone around the city of Mar del Plata (SW Atlantic, 38° S–57° W) is characterized by dense mussel beds of Brachidontes rodriguezii. This intertidal community develops on natural and artificial hard substrates, including abrasion platforms in sewage‐impacted areas. A monitoring program, designed to assess the effect of sewage discharge on intertidal macrobenthic communities, has been conducted since 1997. During the spring season of 2008, a new spionid polychaete (Boccardia proboscidea) was found near the sewage outfall, forming large biogenic reefs. This is the first report of biogenic reefs being built by a non reef‐forming spionid polychaete in areas organically impacted by sewage discharges. The aim of this work was to evaluate the spatial–temporal dynamics (% cover and density of B. proboscidea) of these reefs. These biogenic reefs covered almost the entire impacted site, reaching a density of 650,000 ind·m^?2. This phenomenon is unique in that there is no other record available worldwide of any other biogenic polychaete reefs that could be sewage‐induced. The presence and stability of these biogenic reefs is discussed in relation to increased organic contamination as a structuring factor.     

Polychaete Assemblages in the San José Gulf (Chubut, Argentina), in Relation to Abiotic and Biotic Factors

Abstract. The composition and distribution of the polychaete assemblages of the San José Gulf (Chubut, Argentina) are described in relation to environmental variables using indicator species (TWINSPAN) and canonical correspondence analysis (CCA). The polychaetes were collected during a benthic cruise in October 1984. Sediments were collected at 110 sampling sites using a 0.25 m² van Veen bottom grab or by divers in near-shore areas and sieved with 1 mm mesh. A total of 73 polychaete taxa were collected and identified. Both analyses revealed the presence of four main assemblages distributed according to depth as well as bivalve and seaweed abundance gradients: ' Syllis-Eunice ' and ' Harmothoe-Eunice ' assemblages occurred at the same depths (0 –­ 185 m) and substrata (poorly sorted rock and coarse sand), but were separated by bivalve and seaweed abundance, wherby the highest abundances of bivalves and the minimum abundances of seaweeds corresponded to the ' Syllis-Eunice ' association. The ' Ninoe-Glycera ' and ' Aglaophamus- Fabriciinae indet. 6' assemblages also occurred at similar depths (0 – 60 m) and substrata (very well-sorted medium-fine sand), but differed in their composition of bivalves and seaweed abundances; the ' Aglaophamus- Fabriciinae indet. 6' association corresponded with minimum bivalve and maximum seaweed abundances.     

Tube-forming polychaetes enhance invertebrate diversity and abundance in sandy sediments of Mozambique,Africa

In marine soft-bottom systems, polychaetes can increase habitat complexity by constructing rigid tubes (e.g. several onuphid species) that contrast with surrounding topographically flat sediments. These structures can provide predation refuges and increase larval settlement and thereby increase the richness and abundance of fauna. We collected invertebrate samples from an intertidal flat with low onuphid tube density (2.7 m^–2) in Mozambique and document that more organisms (70 times higher mollusc abundances) and more species (15 times more mollusc species) were found associated with solitary tubes of an onuphid polychaete compared with surrounding sand habitats. These results are in agreement with tube versus sand comparisons from soft-bottom systems in the North Atlantic where polychaete tube densities are often much higher.     

Drag on Hydroid-Fouled Nets – An Experimental Approach

The present study investigated the drag increase on aquaculture nets due to biofouling of the colonial hydroid Ectopleura larynx. It had two main parts: firstly the growth characteristics of E. larynx were investigated by use of field tests at a Norwegian aquaculture site; secondly the hydrodynamic drag on the fouled twines was studied in a towing tank by using fabricated models of net twines with artificial hydroid fouling. In the field tests, the growth of the hydroids was first measured after three weeks of immersion and then again after six weeks. During this interval, the density of hydroids and the thickness of the hydroid stem were almost constant(1.4 hydroids/mm and 0.29 mm, respectively), while the average length of the hydroids increased from 6.4 to 11.2 mm. The hydroid length followed a Rayleigh distribution, while the thickness was normal(Gaussian) distributed. Replicas of twines with three different levels of hydroid growth were made(1.5 hydroids/mm twine, hydroid length 9 mm, 16 mm and 20 mm), and the drag on these twines was measured at different towing velocities(0.1 to 1.4 m/s) and with different twine configurations. For the twine with the shortest hydroids(9 mm), the drag was from 1.5 times(Re=4000) to 2.2 times(Re=1000) the drag on a clean twine. For the longest hydroids(21 mm), the drag was 2 times and 3.8 times, respectively.     

Long‐term changes in hydroid (Cnidaria,Hydrozoa) assemblages: effect of Mediterranean warming?

Marine hydroids are markedly seasonal in temperate seas, being extremely sensitive to climatic changes disrupting seasonal patterns. Modifications in the composition, seasonality, bathymetric distribution and reproductive period of hydroid assemblages are useful to evaluate the influence of global warming on the marine ecosystem. The hydroids on the rocky cliff of the Portofino Promontory (Ligurian Sea, Italy) were carefully studied between 1976 and 1983; in particular, in 1980 the study was carried out along a vertical transect. The hydroids were sampled again throughout 2004, with the same techniques and along the same transect. Species diversity decreased slightly in the 2004 survey. Some species present in 1980 had disappeared in 2004, but other species with southern affinity, never recorded from the area, became abundant in 2004. Species that were present in summer in the first period were also present in winter in the second one. Furthermore, shallow summer species widened their bathymetric distribution, reaching deeper levels. These data strongly suggest that the Portofino hydroid assemblage reacted to the water temperature increase found in the Mediterranean Sea.     

Preliminary data on the composition and distribution of polychaetes in the deep-water areas of the north-western part of the Sea of Japan

During the SoJaBio expedition, the deep sea fauna of the north-western Sea of Japan was sampled in August–September 2010. From this study, 11 epibenthic sledge stations are analyzed, with a focus on species composition, diversity and distribution patterns of polychaetes. A total of 92 polychaete taxa belonging to 70 genera and 28 families and 3 indeterminate species were found. Twelve species and eight genera have not been reported from the Sea of Japan before, but were registered from other deep-sea basins. Calculation of diversity (Shannon–Wiener Index, Pielou's Evenness) showed that the upper bathyal of the Sea of Japan is an area of higher polychaete diversity than the abyssal plain. The increased richness and diversity here could possibly be explained by a zoogeographic overlapping with the shallower species' assemblages of the shelf. At a higher taxonomic level the polychaete fauna of the deep Sea of Japan does not seem to differ from that of other deep-sea regions world-wide. In depths below 2000 m about 30% polychaete species have wide distributional ranges.     

A Sponge-Eating Worm from Bermuda: Branchiosyllis oculata (Polychaeta,Syllidae)*,†

Abstract. Branchiosyllis oculata is a small, errant polychaete that lives only on the surface of sponges: among inshore Bermudian sponges, 9 out of 16 species surveyed were infested. All of these sponges were conspicuously colored, but the bodies and gut contents of associated polychaetes matched the sponge color only for Tedania ignis (red), Cinachyra alloclada (yellow) and Sphecio-spongia othella (brownish-black). For the remaining 6 sponge species, the polychaete bodies were uncolored and the polychaete gut contents were inconspicuously brown or grey. Uncolored polychaetes with grey gut contents were removed from a dark green Tethya actinia and placed on a red Tedania ignis: 2 days later, the polychaete gut contents were red, although the tissues were still uncolored. Acetone extractions of Tedania ignis and Cinachyra alloclada were prepared from sponge tissue and from the gut-free tissue of their respective polychaetes: absorption spectra matched for each sponge/polychaete pair. To test the influence of ingested sponge pigments on polychaete body color, red polychaetes from Tedania ignis were induced to autotomize their posterior ends, transplanted to other sponge species and allowed to regenerate new posterior segments for 20 days. At the end of the experiment the original segments were still red, but the regenerated ones were either yellow (for polychaetes transplanted onto Cinachyra alloclada, on which resident worms are yellow) or colorless (for polychaetes transplanted onto Chondrilla nucula or Tethya actinia, on which resident worms are uncolored). The foregoing observations suggest that (1) the polychaetes consume the soft parts of the sponges on which they live and (2) the pigments vary among sponge species: pigments from some sponges are stored in the polychaete body, while pigments from other sponges are not. Additional information on the morphology, distribution and natural history of Branchiosyllis oculata is presented and discussed.     

A unified assessment of marine Mediterranean assemblages: a lesson from benthic hydroids

Hydroids are important components of the communities of rocky bottom shallow coastal areas. The hydrozoan fauna of the Mediterranean Sea is probably one of most investigated in the world, with lots of faunistic and biogeographical studies. However, quantitative studies using the same sampling methodology and controlled sampling effort have been restricted to areas in the Western and Central Mediterranean. We compared hydroid assemblages in four areas of the Mediterranean Sea, from the Gulf of Cádiz to the South Adriatic Sea, following the same sampling and quantification methodology. Our analysis showed the dominant Atlantic character of the assemblages of the Gulf of Cádiz and the South Alboran Sea because of the influence of the inflowing Atlantic waters. Conversely, the hydroid assemblages of the North Alboran Sea were more similar to the assemblages in the Ligurian and in the South Adriatic, and with a number of species ranking between the observed in these two Mediterranean zones. Fourteen species were identified as making the most significant contributions to characterizing the Mediterranean hydroid species pool from a quantitative point of view. These taxa include species previously named as typical components of the Mediterranean hydroid fauna as well as those only recently recorded in the region (Eudendrium moulouyensis) and invaders such as Clytia hummelincki.     

Importance of seep primary production to Lophelia pertusa and associated fauna in the Gulf of Mexico

To investigate the importance of seep primary production to the nutrition of Lophelia pertusa and associated communities and examine local trophic interactions, we analyzed stable carbon, nitrogen, and sulfur compositions in seven quantitative L. pertusa community collections. A significant seep signature was only detected in one of the 35 species tested (Provanna sculpta, a common seep gastropod) despite the presence of seep fauna at the three sample sites. A potential predator of L. pertusa was identified (Coralliophila sp.), and a variety of other trophic interactions among the fauna occupying the coral framework were suggested by the data, including the galatheid crab Munidopsis sp. 2 feeding upon hydroids and the polychaete Eunice sp. feeding upon the sabellid polychaete Euratella sp. Stable carbon abundances were also determined for different sections of L. pertusa skeleton representing different stages in the growth and life of the aggregation. There was no temporal trend detected in the skeleton isotope values, suggesting that L. pertusa settles in these areas only after seepage has largely subsided. Isotope values of individual taxa that were collected from both L. pertusa and vestimentiferan habitats showed decreasing reliance upon seep primary production with average age of the vestimentiferan aggregation, and finally, no seep signature was detected in the coral collections. Together our data suggest that it is the presence of authigenic carbonate substrata, a product of past seep microbial activity, as well as hydrodynamic processes that drive L. pertusa occurrence at seep sites in the Gulf of Mexico, not nutritional dependence upon primary production by seep microbes.     

Assemblages of hydroids (Cnidaria) from three seamounts near Bermuda in the western North Atlantic

Three seamounts flanking the oceanic island of Bermuda were sampled for hydroids. Collecting was undertaken by submersible (SDL-1) and by dredge at depths between 48 and 107 m on the summits of Argus and Challenger banks. A shallower collection (<20 m) from the pilings of a tower on Argus Bank was made using SCUBA. Major bottom types on both banks were aggregations of rhodoliths, limestone reefs, and areas of calcareous sand. Hydroids were ubiquitous, but quite sparse, on firm substrata. None was collected on sandy bottoms. Of 45 species identified from the two oceanic banks, over half (25) were found on both. On Bowditch Seamount, samples were obtained at depths between 1285 and 1381 m by dredge and grab. Of four species found, only one (Filellum serratum) occurred in shallower collections from Argus and Challenger banks. Most species (43 of 48) from the three seamounts have been reported elsewhere in the Western Atlantic Tropical region, and many (38 of 48) are known from Bermuda. No endemics were discovered, and no relicts or exotics were recognized. Gonophores in >70% of the species are fixed sporosacs instead of free medusae. This conforms with a hypothesis that invertebrates of oceanic islands and seamounts tend to have short-lived pelagic larval stages, ensuring the greatest retention and conservation of propagules.     

The Ecology of Marine Hydroids and Effects of Environmental factors: A Review

Abstract. The history of the study of hydroid ecology is briefly outlined, pointing out the major methodological innovations which have contributed to the development of ecological research in the last thirty years. The influence of the major ecological factors on hydroid ecology and biology is synthesized, taking into account: substratum, water movement, light, salinity, sedimentation, exposure to air, temperature, food availability and pollution. Besides affecting the species composition of the hydroid community, these factors also influence the morphology and general biology of the individual species. The adaptations and reactions of hydroids to different intensities of the various environmental factors and to their combinations are reported.     

福建三沙湾网箱养殖对多毛纲动物群落结构的影响

利用东海近海典型网箱养殖海湾三沙湾9个航次数据,基于群落结构时空差异,阐释网箱养殖活动对多毛纲(Polychaeta)动物群落的影响。就群落组成而言,网箱养殖和非网箱养殖水域多毛纲物种组成存在差异,丝鳃虫科(Cirratulidae)和多鳞虫科(Polynoidae)分别是两种水域最占优势的类群;网箱养殖水域多毛纲优势物种的丰度及丰度比值略高于非网箱养殖区(104.06ind./m248.29ind./m2,57.59%46.96%)。双因素方差分析(采样时间和养殖方式)结果表明,两种因素对物种数(S)、丰度(N)、生物量(B)、Shannon-Wiener多样性指数(H′)、Pielou均匀度指数(J′)、Margalef丰富度指数(d)等典型群落参数的交互作用不显著(P0.05);考虑两种因素独立效应时,群落参数均无显著空间差异(P0.05),但存在极显著时间差异(P0.01)。双因素群落结构相似性分析(two-way ANOSIM analysis)表明群落结构无显著空间差异(P0.05),但存在极显著时间差异(P0.01)。典型对应分析(canonical correspondence analysis,CCA)显示pH、水深和溶解氧是影响三沙湾多毛纲动物分布格局的主要环境因子。上述结论显示,三沙湾网箱养殖活动对多毛纲动物群落结构已产生一定影响,主要表现在群落组成方面,群落结构和部分典型底栖环境因子具较强相关性。     

Benthic Fauna of Oga Bay (Novaya Zemlya,Kara Sea)

Oceanology - The benthic fauna of Oga Bay (Kara Sea, Novaya Zemlya archipelago) was studied in 2015–2016 during the R/V Akademik Mstislav Keldysh expeditions. Five grab stations at depths of...