Hard Bottom Research Articles

Habitat and benthic diversity in the bay of Bagnoli and surrounding areas (Gulf of Naples, Italy): A historical baseline for environmental restoration

The aim of the study is to provide a synthesis on the biodiversity of zoobenthic species and benthic habitat distribution of Site of National Interest (SNI) of Bagnoli-Coroglio (Gulf of Naples, Tyrrhenian Sea, Italy), which represents one of the priority areas selected at National level for habitat restoration, and is located within the Gulf of Pozzuoli (a large Bay at the northern part of the Gulf of Naples). The work provides a dataset, covering the entire Gulf of Pozzuoli, and obtained consulting several sources of information, from historical to recent publications, and grey literature, aimed at the production of a check-list of species, and reconstruction map of the main marine habitats, in order to achieve a synoptic overview of the historical and recent zoobenthic fauna, as well as distribution of habitats, in order to serve as reference point for any future restoration plan in the area. Relevant information regarding the study area was found in 67 out of more than 250 sources consulted. Overall, 813 species of benthic organisms were recorded, summing up a total of 1006 records. Among them, 148 species were reported in the pre-industrial period (prior to 1911), 361 species during the industrial period (from 1911 to 1991), and 381 species in the course of the post-industrial period (from 1992 up to the present day). No differences in biodiversity or distribution of individual species were directly attributable to the industrial activities in the study area. Such a finding is possibly due to different sampling effort among periods and lack of quantitative data for the majority of the recorded taxa. A mosaic of various habitat and biocoenoses were documented in the zones (shallow and deep hard bottoms, soft-bottoms with different sediment types, seagrass meadows). An overall reduction of the cover and a higher habitat fragmentation was documented for seagrass meadows (mainly Posidonia oceanica) over time. Given that regression of this seagrass species is common in a much wider extent than that covered by the study area, the trend here observed is probably due to multiple impacts from different human activities, including the industrial one at the Bagnoli SNI. The present study highlights that the SNI area is placed in a wider area representing a mosaic of different habitat types, which can provide donor populations of both habitat formers (sponges, gorgonians, scleractinians, bryozoans and mollusks), and seagrasses. These organisms are potentially relevant in implementing restoration measures aimed to improve the ecological status of this post–industrial area.

A novel Enterostomula (Platyhelminthes, Prolecithophora) species from two brackish lakes in Japan.

BackgroundThe genus Enterostomula Reisinger, 1926 belongs to the family Pseudostomidae and comprises generally small and often conspicuously coloured species living on hard bottoms, in gravel and amongst algae. The Pseudostomidae comprises approximately 44 known species from Europe as well as North and South America. Previously, only one species, Allostoma durum, had been recorded in Japan. Known Enterostomula species are predominantly found in marine and brackish habitats.New informationI collected seaweed and sand samples from two brackish lakes near the coast of Shimane Prefecture, Japan and isolated turbellarians from them. The animals were observed as both living and preserved. Here, I describe a novel Enterostomula species with two dorsal black bands and a thick bursal wall.

Influence of Fluid in Dynamic Calculation of Thin-Walled Cylindrical Tanks by Means of Calculating Added Masses of Fluid

This paper presents the exact solution for the problem of the added masses of fluid, oscillating inside a cylindrical tank. A thin smooth cylindrical shell of finite length, filled with the ideal incompressible fluid that is subjected to transient dynamic load (it may be an earthquake, air explosion impact, etc.), is taken as a design model. In this case, the shell of a tank becomes a part of the oscillating process along with the fluid stored inside. The shell bending equation (stipulated by the membrane theory of shells) is taken as a design model for this case. In this equation, the shell deflection is expanded into Fourier series by oscillation modes, and the velocity potential takes the form of the Laplace’s equation. Fluid’s inertial reaction to the shell motion is covered by the shallow water theory, which is specified by the boundary free surface conditions and the influence of the tank hard bottom. These mathematical expressions of the shell response to the external transient impact are solved by the Bubnov–Galerkin method with the transformation of the initial relations into a system of ordinary differential equations, which include expressions for determining added masses of fluid by oscillation modes of the elastic shell.

Benthic Habitats, as Derived from Classification of Side‐Scan‐Sonar Mapping Data, Are Important Determinants of Reef‐Fish Assemblage Structure in the Eastern Gulf of Mexico

AbstractIncreasingly restrictive management regulations have greatly reduced the utility of fishery‐dependent data for characterizing temporal changes in the abundance of managed fish populations, so fishery‐independent data are becoming more important for the accurate assessment of stock status. A notable downside to fishery‐independent data is the high cost of conducting surveys, and efforts to maximize survey efficiency are critical given ongoing reductions in agency funding. We conducted a pilot study to explore the utility of classifying side‐scan‐sonar mapping data to provide a practical a priori characterization of reef habitat in the eastern Gulf of Mexico. An analysis of side‐scan‐sonar mapping data identified five distinct reef habitat types (low‐relief hard bottom, mixed hard bottom, fragmented hard bottom, ledges, and potholes) that were subsequently sampled with stereo baited remote underwater video (S‐BRUV) arrays and trap‐mounted GoPro cameras. The permutational analysis of variance indicated that the assemblage structure of reef fish differed significantly (P < 0.01) among all of the pairs of habitats except ledges and fragmented hard bottom; assemblage structure did not differ among cameras (P = 0.45). Overall species richness and diversity were significantly higher in the habitats with greater vertical relief, as were the abundances of several economically and ecologically important reef fishes, although many taxa were observed across all of the habitat types. Benthic habitats that are identified from side‐scan‐sonar mapping data are important determinants of reef‐fish assemblage structure and may prove to be useful as a stratification scheme for reef‐fish surveys, although additional research is necessary to explore the transferability of these results to the rest of the eastern Gulf of Mexico.

Assessing natural capital value in marine ecosystems through an environmental accounting model: A case study in Southern Italy

Coastal and marine natural capital stocks provide a bundle of ecosystem services vital to humans. The delivery of these benefits depends on the protection and sustainable management of natural capital through effective nature conservation strategies. Marine Protected Areas (MPAs) are recognized worldwide as important tools to protect biodiversity while ensuring the delivery of ecosystem services and promoting sustainable human activities. Following the results of a national project aimed at assessing the value of natural capital in the Italian MPAs, in this study we assessed the value of marine natural capital stocks in the Gulf of Naples and Campania Region (Southern Italy) based on a biophysical and trophodynamic accounting model. The assessment focused on four macro-habitats: sciaphilic hard bottom (SHB), photophilic hard bottom (PHB), soft bottom (SB), and Posidonia oceanica seagrass bed (PSB). The total biophysical value of natural capital stocks related to the total area of the Gulf of Naples and Campania Region was 5.70⋅1020 sej and 3.10⋅1021 sej, while the total economic value was 795.92 and 4323.16 M€. Although the SHB habitat only represents about 4% and 1% of the total marine area of the Gulf of Naples and Campania Region, it contributes by 28% and 7% to the total value of natural capital. These figures reflect the high convergence of natural input flows into the marine ecosystem for the generation of the SHB habitat, highlighting the importance of proper measures and actions for its protection. In addition, the calculated values of natural capital stocks were combined with the bionomic map of the Gulf of Naples and Campania Region to show the spatial distribution of natural capital value. The outcomes of this study can support local managers and policy makers in charge for implementing nature conservation strategies aimed at ensuring the sustainable use of marine resources.

Unveiling the deep biodiversity of the Janua Seamount (Ligurian Sea): first Mediterranean sighting of the rare Atlantic bamboo coral Chelidonisis aurantiaca Studer, 1890

Seamounts represent ecologically important marine environments and undeniably play a crucial role in the functioning of the deep-sea ecosystems, thanks primarily to their contribution in supporting offshore benthic and pelagic biodiversity. In the last decades, these features have received attention in all oceans of the world, but they were relatively overlooked in the Mediterranean Sea. In particular, the Ligurian Sea hosts six major structures, whose summits, ranging from 150 to nearly 2000 m depth, are virtually unknown from the biological point of view. The summit region of the Janua Seamount, located approximately at 40 nautical miles off the harbour of Genoa at 810 m depth, was explored for the first time using Remotely Operated Vehicles. The sea bed topography is characterized by a heterogeneous hard bottom, dominated by sub-fossil thanatocoenoses of Lophelia pertusa (Linnaeus, 1758) covered in a thick Ferrous-Manganese crust, and colonized by a scattered bathyal assemblage dominated by hexactinellids and benthic cnidarians showing a distinct regionalization around the summit. Cnidarians observed in this site include a rare Atlantic bamboo coral (Isididae, Chelidonisis aurantiaca Studer, 1890), described herein for the first time for the Mediterranean Basin. These findings provide new information on the biogeographic patterns of colonization of the bathyal Mediterranean fauna but also highlight the large knowledge gap that still exists for deep-sea biodiversity of this basin.

Seasonality and disturbance recovery of the epibenthic community on a warm-temperate hard bottom

Hard bottom communities are variable systems controlled by physical environmental factors, and can be altered by disturbances. Biological factors such as competition, predation, and recruitment can also exert control on the structure of hard bottom communities. Community composition and recovery were measured at three sites on a nearshore hard bottom community in Onslow Bay, North Carolina. Seasonality and recovery of macroalgae and sessile invertebrates were evaluated at a frequency that would allow for an effective assessment of temporal change over a consecutive 16 months (24 May 2016 to 15 Sep 2017). Temporal communities were designated by grouping consecutive sampling days that did not differ (p ≥ .05). Community composition was significantly different between established temporal communities and sites (p < .001). Recovery within experimentally disturbed quadrats differed from corresponding controls depending on the state of the community before the disturbance. Specific taxa were identified as ‘important’ in differentiating temporal communities and sites for community composition. Seasonal temperature changes help explain the temporal patterns, and patchiness can justify the spatial variation. The transition through temporal communities can be related to consistent physical environmental factors, like temperature, but disturbances can introduce variability.

Annual benthic irradiance levels at the Northwestern Cuban shelf

This study, aimed at determining the average annual benthic light irradiance in the northwestern shelf to later calculate its macrophytobenthos total primary production, is the first and only one ever conducted on this subject in Cuban waters to date. Organic mud constitutes 39% of all bottom types, sand is 37%, and the remaining 24% is made up of carbonate mud, hard bottom, rubble, coral, and their combinations. The water average depth is 7.9 m (2 to 28 m range), with an average color 6 (2 to 14 range) in the Forel-Ule scale. Average water temperatures are 28.1 ºC at bottom, and 28.4 ºC at 0.5 m depth, indicating a well-mixed water column; the average bottom water currents speed of 0.116 m s−1 is unremarkable. Visible down to bottom in 73% of all stations, the average Secchi disk depth is 7.1 m (90% transparency) at the remaining 27% stations. The value of the diffuse attenuation coefficient of down welling irradiance “k” is affected by the hour of day, seasons, water color, runoffs, distance from the coast, and depth where it is determined. With an average surface-to-bottom “k” (k0−bottom) value of 0.13 m−1, this shelf water is 34% less transparent than nearby open ocean water. The bottom light illumination is 49% of that at surface, allowing an instantaneous irradiance energy at bottom of 0.31 kW m−2, which is almost twice the average energy most abundant macrophytobenthos species require to reach maximum photosynthesis rates.

Polychaetes from the Caribbean coast of Colombia: An updated checklist and some taxonomic annotations

We present an updated list of the polychaete species described for the Caribbean coasts of Colombia after a historical review of the literature. The taxonomic list includes references to the nomenclature, the synonymies, the data from the ecoregion, the habitat and the bathymetry. Based on the review, we were able to determine that up to September 2019, 51 families, 230 genera, and 293 species with scientific validity had been described for the Colombian Caribbean coast. Eunicidae is the family with the highest number of records, with a total of 33 (11.3%) species, followed by Syllidae with 23 species (7.8%) and Nereididae with 19 species (6.5%). The Tayrona ecoregion presented the greatest diversity, with 32% of species records, followed by the Magdalena ecoregion with 23.4%. Polychaetes in Colombia have been collected in natural habitats such as mangroves, seagrasses, and even as parasites and commensals of other organisms; however, about 60% of the taxonomic records correspond to organisms collected in soft and hard bottoms, mainly between 0 and 15 m deep. The descriptions and records of species on the Colombian Caribbean coast are due to the important contributions made in the 19th century by international and national researchers.

Assessing the Possibilities of Identifying Bowhead Whales on the Arctic Shelf

Real recordings of bowhead whale signals and numerical simulation were used to investigate the propagation of such signals in an Arctic-type shallow-water waveguide. The authors analyzed attenuation and distortion of whale signals with increasing distance in the following conditions: (1) a soft and hard bottom, (2) different whale depths, (3) surface waves, (4) additive noise, and (5) reception by a single hydrophone and a vertical array. Signal attenuation was estimated by the change in sound pressure level (SPL). Signal distortion was estimated by the change in the correlation coefficient for the spectrograms of received signals and the reference spectrograms. It is shown that, compared to signals from a single receiver, the attenuation and distortion characteristics of the array output signals are more stable and resistant to changes in whale depth, to possible, under Arctic conditions, significant variations in sound speed in the bottom along the acoustic path, and to the effects of additive noise. The results can be used for passive monitoring of bowhead whales on the Arctic shelf.

Arrecifes de arenisca en el Golfo de Salamanca, plataforma continental del Caribe colombiano

In tropical seas there are submerged hard bottoms that harbor corals but that are not coralline in origin. This is the case for the “Banco de las Ánimas” sector in the continental shelf of the Gulf of Salamanca, Colombian Caribbean. In its upper portion (14–16 m in depth), there are low mounds of sandstone blocks and slabs, conforming reefs, colonized by coralline biota and sparse corals. To confirm their lithology an initial petrographic analysis was carried out, which showed the rocks are made up of fine-grained sands, mature in texture, cemented by dolomite. It is proposed that these reefs were formed in a beach–dune–lagoon system during an ancient sea level, similar to the recent coastal bar of Salamanca. In these high-evaporation, supratidal saline environments, they could have been formed as beach rocks or as eolianites, by aragonite cementation, modified later into dolomite. Whether the foundation of the deeper coral formations of the bankis also sandstone or in fact coralline, remains to be determined.

Comparative Analysis of Mollusc Assemblages from Different Hard Bottom Habitats in the Central Tyrrhenian Sea

Composition, trophic structure, and species-substrate relationships of molluscan assemblages inhabiting different hard bottom habitats (Sabellaria alveolata reef, photophilic bottoms, Phyllophora crispa sciaphilic assemblage, and coralligenous bioconstruction) were studied in two different sites of the Tyrrhenian Sea. In particular, molluscs from the Sabellaria alvevolata (Linnaeus, 1767) reef and coralligenous concretion were investigated, testing the hypothesis that bioconstructions increase the diversity and abundance of associated biota compared to the surrounding habitats. A total of 3134 individuals belonging to the classes of Polyplacophora (5 species, 24 individuals), Bivalvia (39 sp., 2734 ind.), and Gastropoda (53 sp., 376 ind.) were identified. These three taxonomic groups showed different distribution patterns in the studied habitats. Multivariate analyses revealed significant inter-habitat differences in the composition of mollusc assemblages, especially between bioconstructions and the other habitats. S. alveolata and coralligenous host the highest rich molluscan fauna when compared to the neighboring hard bottom habitats characterized by photophilic and sciaphilic assemblages. The first ones were dominated by bivalve suspension feeders, mainly represented by sessile and sedentary organisms, which act as bio-constructors, bio-eroders, or simply inhabit the several microhabitats provided by the bioconstructions, while the second ones host a rich molluscan fauna dominated by gastropod grazers and predators. The present study increases the comparative knowledge of molluscan assemblages inhabiting habitats of littoral plans of the Mediterranean Sea, providing pivotal information regarding biodiversity of coastal zones.

On the Possibility of using Vertical Receiving Arrays for Underwater Acoustic Communication on the Arctic Shelf

Numerical simulation is applied to analyze the possibilities of using vertical receiving arrays covering the entire waveguide for underwater acoustic communication on the shallow Arctic shelf. Binary phase shift keying with a carrier frequency of 750 Hz is selected for data transfer. It is shown that an algorithm for selecting acoustic signals corresponding to the first waveguide mode or an algorithm based on using passive-phase conjugation eliminates intersymbol interference. In case of spatial signal processing and waveguide depth of 30 m the error-free information transmission is possible when the signal-to-noise ratio is ≈15 dB less than that for a single receiver. It has been demonstrated these advantages to be present in different conditions on the Arctic shelf: with an acoustically soft or acoustically hard bottom, with surface waves, or with ice cover.

Inhabiting the technosphere: The encroachment of anthropogenic marine litter in Neotropical mangrove forests and its use as habitat by macrobenthic biota

Coastal urbanization is leading to the accumulation of anthropogenic litter. Understanding the distribution and habitat use of litter by marine biota is important to predict how organisms will respond to anthropogenic changes. We assessed the density, distribution and composition of surface macro-litter (SML) in mangrove forests in Buenaventura (Colombia) and analysed how these microhabitats are used by marine biota. SML density ranged from 2 to 314 g m−2 (0.22 to 35.5 items m−2), implying that mangrove forests surrounding Buenaventura city are among the most polluted coastal areas in the World. Biological assemblages colonizing SML differed according to position on the forest and litter type. The encroachment of SML in mangrove forest enables a seemingly transient colonization of resident and immigrant biota from intertidal rocky shores and subtidal hard bottoms. The successful colonization of SML poses questions regarding the potential for plastics or their leaching chemicals to transfer through food webs.

Distance from rocky shores affects infaunal recolonization in a subtropical tidal flat

Hard bottoms can negatively affect the surrounding infauna by hosting predatory fauna and modifying local hydrodynamics and sedimentation rates. Considering that these effects depend on the distance to the hard bottoms, we expected that the infaunal structure and recolonization would change accordingly. We assessed whether the distance from a rocky shore alters infaunal recolonization in a subtropical tidal flat. Sediment was defaunated on sites near and far from a rocky shore and the subsequent faunal recolonization was followed for 40 days. The sites near and far from the rocky shore displayed different assemblage structures, which we attributed to local variation in hydrodynamic conditions. Both the total infaunal abundance and the abundance of the dominant species recovered faster at the near site. We indicate that changes in infaunal recolonization at varying distances from natural rocky shores are primarily driven by the availability of adults. Infaunal recovery took less than 2 weeks, but recolonization rates increased near the rocky shore, as a function of its naturally variable assemblage structure and relatively lower species richness and abundances. We suggest that models of infaunal distribution and recolonization should incorporate landscape features such as the presence and distance from rocky bottoms.

Lessons from photo analyses of Autonomous Reef Monitoring Structures as tools to detect (bio-)geographical, spatial, and environmental effects

We investigated the validity of Autonomous Reef Monitoring Structures (ARMS) as monitoring tools for hard bottoms across a wide geographic and environmental range. We deployed 36 ARMS in the northeast Atlantic, northwest Mediterranean, Adriatic and Red Sea at 7–17 m depth. After 12–16 months, community composition was inferred from photographs, in six plate-faces for each ARMS. Overall, we found a highly significant effect of sea region, site (within seas), and plate-face on community composition. Plate-faces thus represent distinct micro-habitats and provide pseudo-replicates, increasing statistical power. Within each sea region taken individually, there was also a highly significant effect of site and plate-face. Because strong effects were obtained despite the fusion of taxonomic categories at high taxonomic ranks (to ensure comparability among biogeographic provinces), ARMS photo-analysis appears a promising monitoring tool for each sea region. We recommend keeping three ARMS per site and analyzing more numerous sites within a sea region to investigate environmental effects.

A unique and threatened deep water coral-bivalve biotope new to the Mediterranean Sea offshore the Naples megalopolis

The Gulf of Naples is an example of the most beautiful and biodiverse marine regions of the Mediterranean Sea and of the most impacted areas in terms of industrial activities, large contaminated areas, resource exploitation, infrastructures at sea and maritime transportation. We conducted Remotely Operated Vehicle surveys in the Dohrn Canyon in the Tyrrhenian Sea at approximately 12 NM off Naples metropolitan area, and revealed a hotspot of deep-sea benthic biodiversity of sessile fauna at ca. 400 m depth. The hard bottoms are characterized by a high abundance of charismatic species, such as the habitat forming cold-water corals (CWC) Madrepora oculata, Lophelia pertusa, Desmophyllum dianthus in association with the large size bivalves Acesta excavata and Neopycnodonte zibrowii. This CWC-bivalve co-occurrence represents a novel biotope for the Mediterranean Sea, which coexists with the evidence of severe anthropogenic threats, such as illegal dumping and fishery malpractices that were visually documented during the survey. We recommend the adoption of specific protection measures to preserve these unique deep-sea assemblages showing the uncommon co-existence of such a number of deep-sea species in a single habitat.

Partitioning multiple diversity dimensions of nearshore fish assemblages within a coastal seascape

The conservation of coastal seascapes requires a better understanding of how different dimensions of biodiversity are represented between juxtaposed habitats. We explored patterns of taxonomic, functional, and phylogenetic diversity of fishes between four habitats (sandy bottoms, rocky reefs of high and low relief, and mixed bottoms) within a semi-lagoon seascape (Las Canteras beach) in Gran Canaria Island. Data on fish presence in each habitat were provided by weekly snorkeling tours, at day and night, from August 2015 to August 2018. Indices that measured ‘how much’ biodiversity, i.e., ‘how many species’ (species richness), ‘how much functional dissimilarity’, and ‘how much evolutionary history’ were larger on rocky bottoms. However, indices that measured phylogenetic differentiation, i.e., ‘how different’, via the taxonomic distinctiveness and the Mean Pairwise Distance index were particularly high on sandy bottoms, because of the presence of elasmobranchs, which were absent from rocky bottoms. The ‘phylogenetic signal’, whether phylogenetically related species are functionally similar, was significant on rocky bottoms, but non-significant on sandy bottoms, reflecting phylogenetic ‘overdispersion’ on sandy bottoms and phylogenetic ‘clustering’ on hard bottoms. From a conservation perspective, sandy bottoms cannot be underrated, particularly in the context of maximizing indices that measure ‘how phylogenetically different’ biodiversity is.

The Identification of Hard Bottom Surface Structure using Correlation of Geoelectrical Resistivity Methods and SPT Data as Preliminary Studies for Laying the Foundation at Passing Cross Sumatera Toll Road, South Lampung Station

The planting of the Upper pass foundation on the Sumatera toll road construction project in South Lampung requires proper planning in terms of both technical and safety aspect. Generally, in principle, the foundation should be able to reach soil layers, or in case the hard soil is not easily found, the compaction or soil recovery. To find out the geological condition below the soil surface, related to the planting and construction of the foundation, it is necessary to investigate and identify the geological structure of the area. The method used to identify the subsurface methods and the Standard Penetration Test (SPT). The resistivity geoelectrical method utilizes a variety of resistivity values for each rock, while the SPT method uses the amount of resistance (N) per depth of soil penetration in its process. The result of the investigation using these two parameters will then be correlated with the geological conditions of the research field to determine the hard surface structure. Hard layer on the research field had resistivity values above 250 Ω and N-SPT values are above 50, identified as a fine sand layer containing gravel breccia sandstone and granodiorite stones. The subsurface hard layer can be found from a depth of 0-25 meters at the research field.

First Macro-Colonizers and Survivors Around Tagoro Submarine Volcano, Canary Islands, Spain

Tagoro, the youngest submarine volcano of the Canary Islands, erupted in 2011 South of El Hierro Island. Pre-existing sea floor and inhabiting biological communities were buried by the newly erupted material, promoting the appearance of new habitats. The present study pursues to describe the first metazoans colonizing different new habitats formed during the eruption and to create precedent on this field. Through dredge and remote operated vehicle samplings, five main habitat types have been detected based on the substrate type and burial status after the eruption. Inside the Tagoro volcanic complex (TVC), two new habitats are located in and around the summit and main craters—hydrothermal vents with bacterial mats and sulfurous-like fields mainly colonized by small hydrozoan colonies. Two other habitats are located downslope the TVC; new hard substrate and new mixed substrate, holding the highest biodiversity of the TVC, especially at the mixed bottoms with annelids (Chloeia cf. venusta), arthropods (Monodaeus couchii and Alpheus sp.), cnidarians (Sertularella cf. tenella), and molluscs (Neopycnodonte cochlear) as the first colonizers. An impact evaluation was done comparing the communities of those habitats with the complex and well-established community described at the stable hard substrate outside the TVC, which is constituted of highly abundant hydrozoans (Aglaophenia sp.), antipatharians (Stichopates setacea and Antipathes furcata), and colonizing epibionts (e.g., Neopycnodonte cochlear). Three years after the eruption, species numbers at Tagoro were still low compared to those occurring at similar depths outside the TVC. The first dominant species at the TVC included a large proportion of common suspension feeders of the circalittoral and bathyal hard bottoms of the area, which could have exploited the uncolonized hard bottoms and the post eruptive fertilization of water masses.