Artificial Hard Substrates Research Articles

The Kumamoto Oyster Crassostrea sikamea is Neither Rare nor Threatened by Hybridization in the Northern Ariake Sea, Japan

The status of the Kumamoto oyster Crassostrea sikamea in its native Japan is uncertain because of a lack of information about its abundance and distribution and a suggestion that C. sikamea and the Pacific oyster C. gigas hybridize in the northern Ariake Sea. Furthermore, broodstock populations on the United States Pacific coast have been hybridized with C. gigas in the past and may suffer inbreeding depression from multiple generations of hatchery-propagation. As a result, Japanese conservationists and United States oyster growers share an interest in the status of this species in the wild. We collected wild oysters from three sites in Saga Prefecture located in the northern portion of the Ariake Sea, Kyushu, Japan, in September 2006 and used molecular methods (species-specific PCR of the mitochondrial COI gene and PCR-RFLP of the nuclear ribosomal ITS1 gene) to assign 628 sampled oysters to one of three species found in this region. C. sikamea proved to be the dominant organism on artificial hard substrates, comprising 91% of the oysters sampled and typed. Many individuals confirmed as C. sikamea by diagnostic DNA markers had C. gigas-like phenotypes, such as striped shells. Crassostrea ariakensis was present (8% of typed oysters) but only at the lowest intertidal levels, and C. gigas was rare (1%) at these sites. We found no evidence of hybridization between any of the species and were unable to repeat a previous study, which suggested hybridization between C. sikamea and C. gigas based on sharing of a calmodulin allele. We conducted gamete compatibility tests among all combinations of Japanese (Ariake Sea) and United States C. sikamea and C. gigas broodstocks and found strong one-way gamete incompatibility (male C. sikamea × female C. gigas) between species of Japanese stocks, supporting the molecular diagnosis of C. sikamea. However, this one-way incompatibility was less evident in United States stocks, indicating lower barriers to potential hybridization in commercially cultured stocks.

Epilithic communities in a lake littoral zone: the role of water-column transport and habitat development for dispersal and colonization of meiofauna

Abstract During the past 30 y, periphyton has been recognized as a key component in the benthos of lake littoral zones. However, the role of meiofauna-sized organisms living in the periphyton and mechanisms regulating and influencing those communities largely have been neglected, and the process of community development and colonization pathways of periphytic meiofauna are unknown in lakes. We studied these processes on littoral hard substrates in an oligotrophic lake. We manipulated the access of meiofauna to artificial hard substrates for a period of 57 d in a field experiment. In one treatment, the direct colonization pathway via active crawling was prohibited by elevating substrates into the water column. Development of the meiofaunal community was compared between elevated and nonelevated (control) treatments. In addition, relationships among the meiofaunal communities on the substrates in the field experiment and those in sediment traps and on natural hard substrates were examined. Periphyton biomas...

Seasonal variations of epilithic diatoms on different hard substrates, in the northern Adriatic Sea

The colonization of epilithic diatoms on artificial hard substrates (marble, quartzite and slate) was investigated on a seasonal basis in a subtidal site of the northern Adriatic Sea to determine if substrate-dependent differences in colonization occurs and to define the seasonal variations of microepilithic communities in terms of abundance, biomass and community structure. Artificial substrates (smoothed small discs mounted on a Plexiglas sheet) were placed at a depth of 8 m in April 2003, July 2003, January 2004 and February 2004. The discs were collected after 6–7 weeks for counting and taxonomic identification of the diatoms. The community structure of epilithic diatoms showed a dominance of motile species over the entire study period, followed by erect, adnate and tube-dwelling diatoms. Diatom density showed a marked seasonal variability, ranging from 365±407 (winter 2004) to 557156±82602 cells cm-2 (spring 2004). Biomass ranged from 0.02±0.01 to 17.53±3.20 μg C cm-2. Abundance and biomass values did not present any significant differences for the three substrates examined.

Animal fouling as an indicator of water quality in Mediterranean fish farmed areas

In the Mediterranean, most of the fish farm plants are located in very deep water columns (>20-30 m) and are characterised by energetic hydrodynamic regime levels. Thus, the effects of farming loading should not be investigated exclusively in the underlying sediments, because the uneaten feed particles, once produced, are transported laterally rather than vertically within the water column. Under such conditions, benthic organisms attached on artificial hard substrata (i.e. fouling) in the surrounding of fish farms are recently proposed as a reliable tool in detecting environmental modifications in the water column. In the present paper, we report on the ecological response of fouling organisms to organic loading from a fish farm located in the Gulf of Castellammare (Sicily) by comparing artificial hard substrata in sites upstream (control, CTRL) and downstream (impact, IMP) from the fish cages. The experiment was carried out in Autumn 2004, when samples of fouling organisms (quadrats of 20×20cm) were scraped by means of a putty knife from plastic buoys spaced throughout the study area. In the lab, samples were frozen (-20°C) or stored in alcohol or formalin as a function of taxa. All specimens from each quadrat were sorted, classified according to species or genera (number of taxa, S), and counted (abundance, n). To test whether fouling ecological features were different among CTRL and IMP, a Permutational Analysis of Variance (PERMANOVA) was carried out on a Bray-Curtis dissimilarity matrix and P-values were calculated using 9999 permutations. In the analysis, treatment (CTRL vs IMP, 2 levels) was the fixed factor and quadrats in each treatment represented replicates (n=9). The fouling community was composed of 6 functional groups, and their abundance and frequency were significantly different among controls and impacts (PERMANOVA, p<0.05). Suspension feeders, represented by bivalves (55.0-60.0 ± 30.0%) and barnacles (40.0-45.0 ± 27.0%), were the most abundant taxa within the fouling community, while grazers (e.g. limpets) and predators (e.g. crabs) accounted for not more than 1% of the total abundance within the community. Bivalves were significantly more abundant at impacted sites, while barnacles dominated at controls. The water column depth in the study area was higher than 40m and for this reason sediments were less affected by organic waste coming from facilities. Thus, the results of the present paper showed that, in deep waters, fouling organisms could efficiently record trophic modifications of the water column induced by organic waste. They also represent one of the most reliable tools for detecting environmental alterations in the surrounding of fish farms.

Colonization and early succession on artificial hard substrata by meiofauna

An experiment was undertaken at Farol Island, Brazil, to examine colonization of bare aluminium surfaces by microbes and meiofauna. It was hypothesized that a primary source of meiofaunal colonists was sediment resuspended during upwelling events, two of which occurred during the experiment. Microbial biofilms formed on the experimental substrata within 1 day, and continued to develop throughout the experimental period. Among meiofaunal groups copepods also appeared on the first day, and nematodes on the second. Meiofaunal community structure developed in three main phases: an initial phase of 2 days, characterized by low abundances of copepods; a second phase during the first upwelling period characterized by higher abundances of copepods and also by turbellarians; and a third phase from day 13 onwards characterized by relatively stable abundances of a range of taxa including copepods, cirripedes, nematodes and ostracods. Nematode assemblages also developed in three phases, but with different timings coinciding with upwelling events: an initial phase, from the beginning of the experiment to day 9, characterized by few species and low (or no) abundances; a second phase following the first upwelling characterized by moderate abundances of Chromadorina, Chromadorella, Daptonema and Euchromadora sp. 3; a third phase following the second upwelling period (from day 26 onwards) in which Daptonema disappeared and the assemblage was characterized by moderate to high abundances of Euchromadora (species 1 and 2) and Chromadorella. Although shifts in nematode assemblage structure coincided with upwelling events no evidence was found for sediments being the primary source of colonizers on the aluminium substrata, in contrast to our hypothesis.

Changes in benthic fish assemblages as a consequence of coastal works in a coastal lagoon: The Mar Menor (Spain, Western Mediterranean)

The benthic fish assemblage of the Mar Menor consisted of 37 species. Dominant species are: Gobius cobitis, Lipophrys pavo and Tripterygion tripteronotus on infralittoral rocks; Pomatoschistus marmoratus, Callionymus pussillus, Callionymus risso and Solea vulgaris on sandy bottoms and Gobius niger, Syngnathus abaster, Hippocampus ramulosus and Symphodus cinereus on Cymodocea nodosa– Caulerpa prolifera mixed beds. From 1985 to 1989 tourist development has led to the creation of new beaches and the installation of artificial rocky structures for retaining sediments. Dredging for the extraction of sand and subsequent pumping altered sediment characteristics causing a real stress leading to the substitution of typical sandy bottoms communities with Cymodocea nodosa by Caulerpa prolifera communities on mud. Soft bottom fish assemblages responded to changes in vegetation cover and substratum characteristics mainly changing the species composition, while artificial hard substrata contain a similar fish community than natural ones, harbouring even richer and more diverse assemblages. This positive effect of breakwaters should not obscure their likely negative effects on hydrodynamics and the subsequent changes of sediment quality and vegetation cover on the breakwaters’ area of influence.

Mass occurrence of an introduced crustacean (Caprella cf. mutica) in the south-eastern North Sea

The caprellid amphipod Caprella mutica is indigenous to coastal waters of north-east Asia and was first recorded in European waters in 1995. We now detected mass occurrences of > 3000 individuals per m2 in harbours of the two islands of Sylt and Helgoland in the German Bight, North Sea. Currently, Caprella mutica seems to be restricted to artificial hard substrata but we expect it to become a new species in natural hard bottom assemblages of that region as well.

Peracarida populations of hard substrate assemblages in ports of the NW Aegean Sea (eastern Mediterranean)

This study deals with the structure of Peracarida populations in four ports in the NW Aegean Sea, Greece, and with the degree this structure is influenced by the particular biotic and abiotic conditions that prevail in the ports. Quantitative samples were taken during summer and winter in two successive years from artificial hard substrates and were analysed using common biocoenotic methods. The examination of approximately 81,250 specimens revealed the presence of 24 Peracarida species, the most dominant of which were Corophium acutum, Leptochelia savignyi and Elasmopus rapax. All species are very common and have been reported from many sites and assemblages in the N Aegean Sea. The ratios of certain Peracarida genera are discussed as possible indicators of environmental health that may be used in long-term biomonitoring programmes on the impact of pollution in harbours.

Structure of the artificial hard substrate assemblages in ports in Thermaikos Gulf (North Aegean Sea)

The present study describes the hard substrate assemblages established on the concrete blocks of three ports placed in gradually longer distances from the main source of pollution in Thermaikos Gulf. The samplings were performed on a seasonal basis for a 2-year period. The data analysis indicates a clear separation of the assemblages from each port. Evenness and Shannon–Weaver diversity indices were calculated and their values were found to be quite high. This fact, combined with the seasonal pattern that these assemblages hold, reveals stability and a good adaptation of their faunistic components to local environmental conditions. A change due to the construction of a new block functioning as a surge barrier was detectable at the station of N. Michaniona. Once again, biomonitoring proves to be essential in order to obtain useful information about the water conditions. Emphasis was laid on the taxa of Polychaeta by analyzing their numerical abundance and their feeding guilds separately. The results were very similar, a fact that supports the opinion that a specific taxonomic group can be used for the description and the monitoring in many different cases.

Abundance and colonization potential of artificial hard substrate-associated meiofauna

Meiofauna are known to live on hard substrates in association with periphytic and epiphytic algae and attached epibiota; however, the abundance, diversity and colonizing abilities of hard-substrate meiofauna have been poorly documented. We quantified meiofauna living on microalgal-covered pilings associated with a wood pier in a shallow (<2 m deep) estuarine embayment with the use of a suction sampler, and compared colonization of pier-piling and sediment-dwelling meiofauna onto collectors that capture suspended meiofauna from the water column. Collectors were small mesh pads (159 cm 3) suspended at mid-water depth, and their size and structural complexity were similar to floating or drifting masses of macroalgae that may be colonized by meiofauna. Sediment was collected by coring, and copepod (to species) and nematode (to genera) colonists on mesh pads were compared with pier-piling and sediment communities. Abundance of total meiofauna averaged 124±13.6 (S.E.) on pier pilings, compared to 2092±274.6 individuals 10 cm −2 in surrounding sediment. Phytal copepods (free-living copepods with prehensile first legs and dorsoventrally and laterally compressed body forms) and copepod nauplii dominated pier-piling collections, but nematodes were dominant on faunal collectors and in sediment. Phytal copepods also were abundant on faunal collectors but were rare in sediments. Copepod and nematode diversities were similar, but species composition was largely nonoverlapping, in pier pilings and sediments. Net recruitment of meiofauna to faunal collectors averaged about 900 individuals collector −1 day −1 during the 1-week experiment. Nematode and copepod colonists on faunal collectors were both much more similar to pier-piling than to sediment assemblages. These data suggest that meiofauna are abundant and diverse on algal-covered pier pilings, and they may become more important to marine ecology as artificial hard substrates increase with increasing urbanization. Furthermore, pier-piling meiofauna appear to readily migrate into the water column and probably contribute to a rapidly dispersing pool of meiofauna in estuaries.

Artificial armored shorelines: sites for open-coast species in a southern California bay

Artificial hard substrates have been used to stabilize naturally soft bay shorelines for centuries. Despite the loss of over half of the natural shoreline in many bays, little attention has been paid to the communities inhabiting armored shorelines and to the ecological implications of armoring. The goal of the present study was to examine factors affecting spatial and temporal variation of intertidal, hard-substrate biota (emergent species and fishes), with emphases on the influence of exposure, distance from the open ocean, and similarity to open-coast, hard-substrate communities. We examined community composition at eight San Diego Bay (California, USA) sites (an exposed and a protected site at four bay locations) in June and November 2000 and two open-coast sites in August 2000. At all bay sites, the shore was armored with granite boulders, a form of shoreline stabilization referred to as "riprap." Community structure was more variable spatially than temporally on the scales we studied, affected more by distance from the bay mouth and exposure to wave energy than by differences between June and November. Exposed sites near the bay mouth were more similar to natural open-coast sites, sharing about 45% of their species, than protected sites and sites farther from the mouth, which shared as few as 8%. Species richness was generally higher in exposed than protected bay sites. Species tended to occur higher in the intertidal zone at exposed than protected sites, and higher in November, when sea level was higher, than in June. Such results will be useful to shoreline managers who examine the ecological implications of hardening long stretches of coastline and may suggest ways to incorporate artificial structures into ecosystems in a more meaningful way.

Marine Macroinvertebrate Diversity of St. Catherines Island, Georgia

St. Catherines Island is one of several barrier islands lining the coast of Georgia, USA. This island is among the least recently anthropogenically impacted of the Georgia Sea Islands, but had not previously been examined in detail for coastal invertebrate macrofauna. From 1992 through late 1998 a coastal survey was conducted that examined the diverse marine invertebrate fauna of St. Catherines Island. Salt marshes, sand flats, mid- to low-energy sand beaches, beach wood debris, tidal creeks, shallow benthos, and artificial hard substrata (including docks) were qualitatively sampled for macroinvertebrates. Over 340 species were identified. Crustaceans composed close to 40% (14% amphipods; 15% decapods), polychaetes 17.5%, and molluscs about 25% of all species recovered. These results are compared to the few other relevant studies from the United States mid-Atlantic Coast.

A study of the natural antifouling mechanisms of the green musselPerna viridisL. (Mytilidae)

The green mussel Perna viridis L. (Mytilidae) is commonly found on hard substrata in the littoral zone of the upper Gulf of Thailand. Mussels appeared to be less densely colonized by epibionts than other artificial and natural hard substrata. The number of epibionts (bacteria, diatoms, protozoa, fungi, macroorganisms) on Perna viridis shells and their potential defence mechanisms were studied. The number of epibionts on isolated mussels and those in patches were compared. Densities of protozoa and macrofauna were much higher on isolated specimens than on aggregated (patch forming) mussels. Among possible antifouling mechanisms which were studied sloughing, shell surface tension and surface‐pH proved to be non effective in preventing fouling. Toxicity assays of shell extracts showed limited activity against bacteria and fungi. Grazing by two different gastropod species (Planaxis sulcatus, Thais sp.) reduced the number of protozoa and macroorganisms on isolated and aggregated mussels. Diatoms were restricte...

The origin of manganese nodules on the ocean floor : Bonatti Enrico and Y. Rammohanroy Nayudu 1965. Am. J. Sci., 263 (1): 17–39

Habitat restoration and recolonisation of benthic communities after physical perturbation in the deep sea has long been thought to be extremely slow. This study reports on a serendipitous opportunity to survey the current state of a large mechanical disturbance of sediments at 6460 m in the Pacific Ocean. The impact was caused 77 years ago by the sinking of the USS Johnston. The surrounding debris field had little impact on the sedimentary habitat, other than in the provision of artificial hard substrates, while the troughs that formed as the ship impacted the seafloor and slid down the slope of the Philippine Trench were still completely void of animal tracks and burrows, or any observable epifauna, and in some areas subsurface stratification was still exposed at the surface. This suggests that mechanical perturbations of sediments in the deep Pacific may remain ecologically significant for, at the very least, 100 years.