Natural Rocky Habitats Research Articles

Movement ecology of an endangered mesopredator in a mining landscape

BackgroundEfficient movement and energy expenditure are vital for animal survival. Human disturbance can alter animal movement due to changes in resource availability and threats. Some animals can exploit anthropogenic disturbances for more efficient movement, while others face restricted or inefficient movement due to fragmentation of high-resource habitats, and risks associated with disturbed habitats. Mining, a major anthropogenic disturbance, removes natural habitats, introduces new landscape features, and alters resource distribution in the landscape. This study investigates the effect of mining on the movement of an endangered mesopredator, the northern quoll (Dasyurus hallucatus). Using GPS collars and accelerometers, we investigate their habitat selection and energy expenditure in an active mining landscape, to determine the effects of this disturbance on northern quolls.MethodsWe fit northern quolls with GPS collars and accelerometers during breeding and non-breeding season at an active mine site in the Pilbara region of Western Australia. We investigated broad-scale movement by calculating the movement ranges of quolls using utilisation distributions at the 95% isopleth, and compared habitat types and environmental characteristics within observed movement ranges to the available landscape. We investigated fine-scale movement by quolls with integrated step selection functions, assessing the relative selection strength for each habitat covariate. Finally, we used piecewise structural equation modelling to analyse the influence of each habitat covariate on northern quoll energy expenditure.ResultsAt the broad scale, northern quolls predominantly used rugged, rocky habitats, and used mining habitats in proportion to their availability. However, at the fine scale, habitat use varied between breeding and non-breeding seasons. During the breeding season, quolls notably avoided mining habitats, whereas in the non-breeding season, they frequented mining habitats equally to rocky and riparian habitats, albeit at a higher energetic cost.ConclusionMining impacts northern quolls by fragmenting favoured rocky habitats, increasing energy expenditure, and potentially impacting breeding dispersal. While mining habitats might offer limited resource opportunities in the non-breeding season, conservation efforts during active mining, including the creation of movement corridors and progressive habitat restoration would likely be useful. However, prioritising the preservation of natural rocky and riparian habitats in mining landscapes is vital for northern quoll conservation.

Taxonomic and functional diversity of subtidal benthic communities associated with hard substrates at Crozet archipelago (sub-Antarctic, Southern Ocean)

Sub-Antarctic coastal marine ecosystems harbor rich and diverse benthic communities. Despite their ecological uniqueness and vulnerability to global changes, studies on benthic communities remain limited. Using underwater video-imagery, we investigated the taxonomic and functional diversity of benthic communities associated with hard substrates at Baie du Marin (Ile de la Possession, Crozet archipelago). The Baie du Marin species richness and diversity were additively partitioned to evaluate spatial patterns of species through the following spatial scales: within images, among images within transects, and among transects. We analyzed imagery data from seven transects located at different sites inside Baie du Marin and covering contrasting natural rocky habitats and underwater artificial cable substrates. A total of 50 faunal (mainly represented by Echinodermata and Porifera phyla) and 14 algae (mainly represented by Rhodophyta phylum) taxa were identified. Rocky substrates were dominated by high densities of the polychaetes Parasabella sp. and Lanice marionensis, whereas submarine cables were dominated by high densities of the bivalve Kidderia sp. attached to macroalgae. Our results show contrasted distribution patterns in the faunal and algal assemblages within the Baie du Marin, with significant ecological differences between submarine cables and natural rocky substrates. Larger spatial scale (i.e., among transects) accounted for most of the bay richness and diversity, highlighting a high-level of habitat heterogeneity within the bay. Through a trait-based approach, our findings revealed that Crozet benthic communities are characterized by low functional richness, evenness, and redundancy, highlighting a potential vulnerability to current and future natural and anthropogenic changes. This study provides a novel bentho-ecological baseline for future assessments of natural and anthropogenic impacts on the marine environment of the Crozet archipelago; and for the conservation management of these remote habitats that make part of the French Southern Territories Marine Protected Area, recently inscribed on the UNESCO World Heritage list.

Weak effects of age but important role of microhabitats in community differences between breakwaters and natural rocky shores across a latitudinal gradient

AbstractAimCoastal infrastructures are increasing at different latitudes, and their deployment often results in a complete replacement of natural habitats. Although infrastructure provides novel habitats, ecological engineering can increase their similarity to natural rocky habitats. One hurdle for effective design of greener infrastructure is the scarce information on the processes that underpin differences in the structure of communities between built and natural habitats. Using long‐term data of intertidal community structure, we tested whether the magnitude of between‐habitat differences changes with breakwater age and across latitudes, and we examined the role of topographic microhabitats (i.e., rock pools) in driving these differences.LocationNine locations distributed from 18 to 41°S.Time period2016–2020.MethodsWe sampled the mid‐intertidal community structure on breakwaters of different age and on natural rocky habitats (platforms and boulder fields) and assessed the availability of microhabitats, such as crevices and rock pools, along a coastline spanning 23° of latitude. Using generalized additive models (GAMs), we assessed the effect of the different factors on species diversity and functional group abundances.ResultsAge since construction was a poor predictor of differences between breakwaters and natural habitats. Communities on older breakwaters bore a poor resemblance to the species composition or functional group abundances found in natural habitats. The magnitude of differences between breakwaters and natural habitats varied with latitude, with season and with the type of natural habitat attributable to differences in microhabitats, especially in rock pool availability.ConclusionsOur results indicate that replacement of rocky habitats with breakwaters will cause permanent alterations to coastal ecosystems. Our findings suggest that the availability of microhabitats able to shelter species from stressful environmental conditions is more important at lower and intermediate latitudes; hence, they should be incorporated primarily into infrastructures in tropical or subtropical areas. These strategies could help to compensate for the impacts on rocky ecosystems associated with increases in coastal urbanization.

The ecological benefits of adding topographic complexity to seawalls vary across estuarine gradients

Artificial structures such as seawalls increasingly dominate marine urban environments. As compared to natural rocky shore habitats, seawalls are usually flat, featureless, vertical surfaces that support reduced biodiversity. One approach to increase their biodiversity is to add topographic complexity (‘complexity’) that increases microhabitat diversity and surface area. Initial investigations of the effects of complexity on the biodiversity of marine built structures found positive relationships, but more recently spatially variable effects have been found at a biogeographical scale. The present study tested whether at the scale of sites within an estuary (in this case Sydney Harbour), effects of complexity also spatially vary, and whether pollution and estuarine gradients are good predictors of this variation. Comparisons of intertidal communities colonising flat and complex (creviced / ridged) tiles, affixed to seawalls confirmed that effects of complexity were spatially variable at the site-scale, ranging from neutral to highly positive. Proximity to stormdrains, a point source of contaminants including metals, was a poor predictor of complexity effects, but effects were generally greater in the outer harbour, where biodiversity was overall greater, than the inner harbour. These results suggest that eco-engineering interventions based on complexity will not have universally positive effects and instead vary between sites separated by as little as hundreds of meters. Knowledge of spatial variation in physico-chemical conditions and the size and composition of the species pool of available colonists may assist in predicting when and where adding complexity to marine built structures will be of ecological benefit.

Beachrock Formation Mechanism Using Multiproxy Experimental Data from Natural and Artificial Beachrocks: Insights for a Potential Soft Engineering Method

Beachrocks are a window to the past environmental, geological, sedimentological and morphological conditions that were dominant in the coastal zone during their formation. Furthermore, beachrocks have the ability to reduce coastal erosion impact on sandy beaches. This study focuses on the beachrock formation mechanism through the comparison of cement characteristics, mineral chemistry and sedimentology of beachrock occurrences from two different geological and geographical localities: Diolkos, Corinth, Greece and Sumuide, Okinawa, Japan. In addition, in order to investigate a potential soft engineering method to protect coasts from erosion, artificial beachrock samples were created in vitro using sand samples and ureolytic bacteria from both areas under accelerating conditions. For Okinawa artificial beachrock experiments, the bacteria Pararhodobacter sp. was used, and for Diolkos, it was the bacteria Micrococcus yunnainensis sp. For the natural beachrocks, a multi-analytical approach was accomplished with the use of microscopic investigation, a scanning electron microscope, energy-dispersive X-ray spectroscopy, X-ray diffraction and X-ray fluorescence. Correlations were made between natural and artificial beachrocks. Results have shown that Diolkos beachrock was formed in the upper part of the intertidal zone, consisting of detrital material originating from the local bedrock, while Sumuide beachrock formed in the low intertidal–upper subtidal zone, consisting of coral sand and foraminifera fragments. For the artificial beachrocks, three samples were created using the microbial-induced carbonate precipitation (MICP) method, one from Diolkos (Corinth, Greece) and two from Sumuide (Okinawa, Japan). Diolkos artificial beachrock was better consolidated in comparison to Sumuide. Our investigation has shown that bacterial density was the key factor for the creation of the artificial beachrocks, while the samples’ granulometry played a secondary role in the process. The laboratory artificial beachrocks show encouraging results for a new soft engineering method to encounter beach erosion while keeping an ecofriendly character by saving energy, material resources and gas emissions. Artificial beachrocks can share the same properties of a natural beachrock and can contribute positively to marine biodiversity as a natural rocky habitat.

The Invasive Macroalga Rugulopteryx okamurae: Substrata Plasticity and Spatial Colonization Pressure on Resident Macroalgae

The present study constitutes the first evaluation of the space colonization strategies performed by Rugulopteryx okamurae when co-occurring with the resident macroalgal community in the introduced areas. Since the first apparition of the nonindigenous macroalga in the Strait of Gibraltar, its high propagation capacity together with its colonization ability has enhanced the establishment success of the species in detriment of the resident biota. In this study, we carried out observational surveys during 2017–2020 in order to assess the coverage levels of R. okamurae on different lighting conditions, surface orientations, and substrata types (artificial and natural). Results revealed that, beyond the high percent coverages already reported at illuminated and semi-illuminated natural rocky habitats, R. okamurae is able to settle on a wide variety of artificial substrata. The settlement performance of the species was also investigated and different mechanisms underlying the space colonization were proposed. Thus, R. okamurae was observed interacting with 43 resident macroalgal species at generally illuminated rocky habitats of the northern Strait coasts. Six colonization mechanisms were proposed for spatial growth scenarios. Overall, results pointed out that, in most of the cases where the invasive species co-occur with the resident community, R. okamurae would be favored as regards spatial growth success. Competitive interactions and environmental factors which influence results obtained must be addressed in order to fully predict impacts on resident communities. Moreover, together with previous scientific works, overall data provided in this study highlight the need to urgent implement management measures focused on habitats susceptible to be invaded, as well as studies on the ecology and dispersal vectors of R. okamurae in the Strait of Gibraltar and adjacent areas.

Distribution patterns of two co-existing oyster species in the northern Adriatic Sea: The native European flat oyster Ostrea edulis and the non-native Pacific oyster Magallana gigas

Abstract The Pacific oyster Magallana gigas, globally one of the most translocated marine species, has never been commercially farmed in any part of the Croatian eastern Adriatic Sea, where the native flat oyster Ostrea edulis is the only cultured oyster species. The Pacific oyster has, however, established populations on the west coast of the Istria peninsula, in the northeast Adriatic Sea. Current distribution, abundance and size structure of the flat and Pacific oysters were studied there along spatial and depth gradients in natural and artificial habitats to assess their potential for coexistence. This is the first quantitative assessment of native and non-native oyster populations on a Mediterranean-wide scale providing a baseline for determining future changes in their distribution. Both species were omnipresent, with the Pacific oyster displaying a more pronounced variability in abundance and size in relation to survey regions and depths. The population density of flat oysters was low, generally less than 1 individual/m2, with no difference among regions. The density of the Pacific oyster was significantly higher, being on average 5 individuals/m2. Dense, reef-forming aggregations of Pacific oysters were contained in Lim Bay, a nationally-important shellfish aquaculture area, where its mean density was 107 individuals/m2. Along the open coastline its densities were considerably lower and followed a latitudinal gradient. The observed abundance and size distribution patterns of the Pacific oyster suggest that Lim Bay was the introduction point, with feral settlement likely originating from short-lived experimental aquaculture trials and subsequently dispersing by prevailing local currents. The flat oysters were larger in size and settled at different depths compared to the Pacific oysters. The vertical range of Pacific oysters was mostly contained in the tidal zone, while flat oysters were present in the subtidal exclusively. Such spatial partitioning likely resulted from introduced oysters occupying a vacant ecological niche and not due to interspecific competitive exclusion. Habitat type had a strong effect on proliferation of Pacific oysters. Artificial hard substrata harboured more abundant and larger Pacific oysters than the natural rocky shore habitat. The possibility of multiple local introduction pathways in ports and marinas is also discussed. Currently, there seems to be no spatial competition between the two oyster species, but as it is hard to predict future possible impacts of non-native species, we strongly suggest regular monitoring of the Pacific oyster, prioritising sensitive and protected areas as well as areas at the edge of its distribution.

Potential Transmission Cycles of Leishmania tropica in a Historic Disease Focus of Cutaneous Leishmaniasis in Southeast Tunisia

The transmission of Leishmania tropica (Wright) (Protozoa: Sarcomastigophora: Trypanosomatidae) was studied in a historic focus of the cutaneous leishmaniasis disease in southeast Tunisia. The sandfly Phlebotomus sergenti (Parrot) (Diptera: Psychodidae), the confirmed vector of L. tropica in humans, was the most abundant Phlebotomus species found in homes. Phlebotomus chabaudi s.l. (Croset) was the dominant species in the natural rocky habitats favored by the North African gundi, Ctenodactylus gundi (Rothman), which is a known putative rodent reservoir of L. tropica. Leishmania tropica MON-8 (Rioux, Lanotte and Pratlong) was the species isolated and identified from gundi, humans, and P. sergenti in the disease focus area. Based on these results, the North African gundi may serve at least as a maintenance host for L. tropica in this area of southeast Tunisia, even though L. tropica is commonly stated to be anthroponotic. These results also suggest that there may be two transmission cycles of L. tropica in this region, with P. sergenti transmitting L. tropica among humans inside and in peridomestic habitats and P. chabaudi s.l. transmitting the disease agent among gundi in their natural habitats. Phlebotomus chabaudi s.l. also may transmit to humans when humans venture into areas inhabited by gundi host reservoirs.

Production and vertical distribution of invertebrates on riprap shorelines in Chesapeake Bay: A novel rocky intertidal habitat

Along the North American Mid-Atlantic coast, soft-sediment shorelines are armored with hard substrata, such as riprap (rock revetments), for erosion protection. These structures are valuable for determining anthropogenic effects on marine ecosystems, and riprap potentially represents a habitat similar to an “emerging ecosystem” with productive species assemblages. The goals of this project were to (i) quantify species diversity, secondary production, and vertical distribution associated with armored (i.e., riprap) habitats in various locations in Chesapeake Bay and (ii) compare benthic epifaunal production on riprap with infaunal production on natural soft-sediment habitats in a system where natural rocky intertidal habitats are absent. Density, diversity, and secondary production of benthic epifauna on riprap and benthic infauna were compared in adjacent habitats in lower (Lynnhaven River) and upper (Patuxent River) Chesapeake Bay. To compare riprap habitat between tributaries that differed in physical characteristics and with natural rocky intertidal habitats from other systems, oyster, mussel, and barnacle vertical distribution on riprap in southern (Lynnhaven River) and northern (Piankatank River) locations was quantified. The hypothesis was that riprap assemblages and secondary production would differ between rivers and among regions due to differences in physical variables such as temperature (thermal stress in northern locations), or osmotic stress (greater upriver), and patterns would be comparable to natural rocky habitats. We predicted that productivity would be relatively high and relate positively with diversity on riprap, suggesting that it is a habitat within an “emerging ecosystem” where new combinations of species and habitat appear. Benthic epifaunal production on riprap was sevenfold greater than natural infaunal production, and both tended to be highest in the Lynnhaven. Vertical distribution on riprap was similar to that on natural rocky intertidal habitats: oyster and mussel densities tended to be highest in the mid- and low-intertidal zones, whereas barnacle density was greatest in the high intertidal at the southern location and the low intertidal in the northern location. Secondary productivity on riprap was high relative to the natural, infaunal, soft-bottom habitat in this area. Species richness and epifaunal non-oyster production were positively related to oyster production. We demonstrate that intertidal riprap-armored shorelines are a productive novel habitat in an emerging ecosystem, and they enhance species diversity, abundance, and production. Thus, riprap shorelines mimic the ecological characteristics of natural hard-bottom habitats, and they may contribute substantially to ecosystem function throughout the Atlantic and Gulf of Mexico coasts due to riprap's widespread use and distribution.

Shelving the Coast With Vertipools: Retrofitting Artificial Rock Pools on Coastal Structures as Mitigation for Coastal Squeeze

Coastal squeeze caused by sea level rise threatens the size, type and quality of intertidal habitats. Along coastlines protected by hard defences, there is a risk that natural rocky shore habitat will be lost, with remaining assemblages characteristic of hard substrata confined to sea walls and breakwaters. These assemblages are likely to be less diverse and different to those found on natural shores as these structures lack features that provide moist refugia required by many organisms at low tide, such as pools and crevices. Engineering solutions can help mitigate the impacts of sea level rise by creating habitats that retain water on existing structures. However, as experimental trials are strongly affected by local conditions and motivations, the development of new techniques and solutions are important to meet the needs of local communities and developers. Following a small scale community project, a feasibility study retrofitted five concrete-cast artificial rock pools (‘Vertipools’) on to a vertical seawall on the south coast of England. After 5 years, the artificial pools increased the species richness of the sea wall and attracted mobile fauna previously absent, including fish and crabs. The Vertipools had assemblages which supported several functional groups including predators and grazers. Although disturbance of algal assemblages on the seawall from the retrofitting process was still evident after 3 years, succession to full canopy cover was underway. Collaboration between policy makers, ecologists, children and artists produced an ecologically sensitive design that delivered substantial benefits for biodiversity and that could be adapted and scaled-up to both mitigate habitat loss and enhance coastal recreational amenity.

Fish Assemblages on Artificial Fish Habitats in Estuaries: A Comparison with Natural Rocky Habitats

In this study, fish assemblages on deployed artificial fish habitats and natural rocky habitats were compared 1 year post-deployment in Zuari estuary, southwest coast of India employing underwater visual census. Comparisons demonstrated significant differences in fish species composition between artificial fish habitats and natural rocky habitats. Within the artificial fish habitats, the habitats located at deeper regions indicated high richness, diversity and species abundance. The rich and diverse fish assemblages on deeper artificial fish habitats might be a result of isolated location, species behavioral preferences on feeding and shelter and complexity of the habitat.

Time-dependent effects of orientation, heterogeneity and composition determines benthic biological community recruitment patterns on subtidal artificial structures

Worldwide, coastlines are becoming increasingly hardened by infrastructure in response to population growth, need for space, and coastal protection. Coastal and marine infrastructure (CMI) supports fewer species and lower abundance and diversity than analogous natural rocky habitats, which can alter community composition and ecosystem functioning. Efforts to develop ecological engineering solutions that offset these negative consequences on biodiversity while retaining engineering function abound, but to date few studies have investigated the role of multiple factors simultaneously driving patterns of biotic colonisation. Here, the role of surface heterogeneity, chemical composition and surface orientation was evaluated over a 6-month period. An increase in habitat heterogeneity, the replacement of shale for ground oyster shell (cue) and downward orientation was predicted to increase species richness, diversity and abundance. Orientation and heterogeneity greatly affected species richness, abundance, and community composition, and the inclusion of ground oyster shell (cue) increased bivalve recruitment but had only a marginal effect on community structure. Community formation was facilitated by low light but inhibited by sedimentation. On upward-facing surfaces, sediment accumulation on high complexity surfaces expanded niche heterogeneity, and supported communities comprised of burrowing polychaetes and predatory species. Surface orientation and heterogeneity are key factors influencing larval recruitment, and in supporting diverse benthic assemblages on artificial structures. These factors should be considered during the design phase of new engineering projects if the negative consequences of artificial structures are to be minimised while ensuring engineering function is maintained.

Environmental and ecological factors influencing the spillover of the non-native kelp, Undaria pinnatifida, from marinas into natural rocky reef communities

The non-native kelp, Undaria pinnatifida, is considered one of the world’s worst invasive species. The northeast Atlantic is a hotspot of Undaria invasion, yet there is limited knowledge on its invasion dynamics. In the UK its distribution is strongly associated with artificial structures, primarily marina and harbour pontoons, with relatively few records of Undaria on natural substrates. Here, the southwest UK is used as a case region, to explicitly link Undaria distribution-abundance patterns in artificial marina habitats with those in natural rocky reef habitats. Using a mixture of in situ recording and video survey techniques, Undaria was found at all thirteen marina sites surveyed; but in only 17 of 35 rocky reef sites, all of which were in 2 of the 5 larger systems surveyed (Plymouth Sound and Torbay). The distribution-abundance patterns of Undaria at reef sites were analysed using zero-inflated models. The probability of finding Undaria on rocky reef increased with increasing proximity to marinas with high abundances of Undaria. Total propagule pressure from marinas also increased the probability of occurrence, and was positively related to Undaria abundance and cover at reef sites. Increases in the cover of native kelps, Laminaria spp., and wave exposure at reef sites were linked to a reduced probability of Undaria occurrence, and lower abundance and cover. Identifying high risk areas, natural boundaries and factors affecting the spread and abundance of non-native species in natural habitats is key to future management prioritisation. Where Undaria is confined to artificial substrates management may be deemed a low priority. However, the results of this study suggest that controlling the abundance and propagule pressure in artificial habitats may limit, to some extent, the spillover of Undaria into natural rocky reef habitats, where it has the potential to interact with and influence native communities.

Benthic assemblages, biodiversity and invasiveness in marinas and commercial harbours: an investigation using a bioindicator group

Fouling communities on artificial marine structures are generally different from benthic communities in natural rocky habitats. However, they may also differ among different types of artificial structures. Two artificial structures in direct contact with arriving vessels were compared: floating pontoons within recreational marinas, and sea-walls within commercial harbours. Natural rocky habitats were used as a reference, and the genus Eudendrium (Cnidaria, Hydrozoa) was chosen as a bioindicator. The assemblages were different among the three types of habitat studied, with different species characterising each habitat. The probability of finding an invasive Eudendrium species was significantly higher on pontoons. Diversity was the lowest on pontoons, but it was not significantly different between sea-walls and natural rocks. In general, a barrier to the spread of exotic species exists between harbours and natural rocky habitats. Floating pontoons seem to be a less suitable habitat for native fauna and a key element in marine biological invasions.

Mantacaprella macaronensis, a new genus and species of Caprellidae (Crustacea: Amphipoda) from Canary Islands and Cape Verde.

Mantacaprella macaronensis new genus, new species, is described based on specimens collected from Canary Islands and Cape Verde. Mantacaprella is close to the genera Parambus, Pseudolirius, Propodalirius and Paracaprella, but can be distinguished by the combination of the following characteristics: pereopods 3, 4 and 5 two-articulate; pereopods 6 and 7 six-articulate; mandibular molar present and palp absent; male abdomen with a pair of well-developed appendages. The new species has been found living in Cymodocea nodosa meadows and Caulerpa prolifera beds from 8.8 to 14.6 m depth in Gran Canaria (Canary Islands), and in natural rocky and artificial habitats (shipwrecks) at 25 m in Sal Island (Cape Verde). Even though the new species is one of the dominant amphipods inhabiting meadows of Cymodocea nodosa in Gran Canaria and in Cape Verde, it had not been described so far. This reflects the lack of knowledge on Macaronesian invertebrates, such as amphipods, and the need of further taxonomical studies to better characterise the whole biodiversity of this region and to design adequate programmes of management and conservation.

Passive acoustic monitoring of Sciaena umbra on rocky habitats in the Venetian littoral zone

A passive listening survey was conducted in the Venetian littoral zone and combined with a meta-analysis on coastal Mediterranean fish communities resulting in the use of Sciaena umbra as a biological indicator of a typical fish community. The passive listening technique allowed the collection of fish presence/absence data, the analysis of the contribution of different sound categories to the total sound production, as well as a quantitative evaluation of the fish acoustic activity. The passive listening survey proved to be successful in detecting S. umbra drumming sounds in two Venetian inlets and on a natural rocky habitat, whereas this species was absent in the inner Venice lagoon. Within one of the two inlets, pulse rate was positively related to the nearest distance of the listening points to an artificial rocky reef. The meta-analysis allowed the identification of a 16-species cluster significantly associated with S. umbra, a large number of which represent commercially important species. Our results suggest the importance of a wider application of the passive listening technique for biological monitoring, with particular focus on Mediterranean coastal habitats and artificial reefs.

Genetic structure of Linaria capraria Mill. (Plantaginaceae) and endemic species of the Tuscan Archipelago (central Mediterranean)

This study, based on inter-simple sequence repeats in 14 populations of Linaria capraria, shows that genetic diversity at the species level is 0.21 and represents 58% of total variance, whereas the level of intrapopulational genetic diversity is 0.07 and represents 42% of total variance. Gene flow is absent between populations from the same island. On the basis of analysis of molecular variance, three centers of genetic diversity were found: Elba and Pianosa, Montecristo, and Capraia; these correspond to the group of islands that remained isolated during the Würm marine regression. A mean proportion of species-level diversity resides among populations, so we hypothesize that the species has a mixed reproductive system that lies somewhere between obligate outcrossing and obligate selfing. The most genetically diverse populations live in natural and well-isolated rocky habitats that seem to have no particular intervention requirements for conservation but the entire system of populations of this endemic species should be preserved.

Intertidal Assemblages On Artifical Structures And Natural Rocky Habitats On Taiwan'S North Coast

Differences in intertidal assemblages between artifi cial structures and natural rocky habitats require further investigation, so that the potential effects of artifi cial structures on coastal intertidal community can be better understood. We examined the intertidal assemblages on breakwaters, seawalls, and natural rocky shores in the Linshanbi and Houcuo fi shing ports on the northern coast of Taiwan. Nine seawater parameters were measured at each sampling site in Dec.2010, Mar.2011, and Jun.2011. Intertidal assemblages on seawalls were largely distinct from those on breakwaters or natural rocky shores. The taxa that contributed most to the differences among habitats were algae, barnacles, oysters, and limpets. Limpets, red algae, and green algae were less abundant on seawalls compared to breakwaters or the natural rocky shore. Fewer intertidal organisms existed on seawalls than on breakwaters and natural rocky shores. The mobile organisms on breakwaters were similar to those on natural rocky shores. However, during the growing season, a greater number of mobile organisms were found on natural rocky shores than on breakwaters. We suggest that differences in seawater quality, which might relate to the presence of artifi cial structures, could affect the abundance of intertidal organisms. Further information is required on important factors in artifi cial structures that affect intertidal assemblages, in various coastal areas, to help conserve intertidal biodiversity.

Do artificial structures alter marine invertebrate genetic makeup?

Human-made structures are increasingly built in marine coastal habitats for a variety of purposes. Offshore oil and gas production platforms are among the largest examples. Yet, biological effects of these increasing density artificial substrata are under evaluated. The objective of our study is to investigate the possible role of offshore platforms in modifying the genetic composition of populations of natural rocky shores species. The serpulid Pomatoceros triqueter was used as a model, and genetic variation was assessed using a 419 bp fragment of the mtDNA COI gene in samples collected on eleven offshore gas platforms, on one coastal buoy on the sandy shore and in four sites located on natural rocky shores in the Adriatic Sea. Deep phylogenetic lineages were uncovered over all samples. Nucleotide diversity and mean number of pairwise differences among haplotypes were significantly smaller in offshore platform samples compared to rocky shores samples. No significant genetic structure was observed over all samples. We found direct evidence of lower genetic diversity on platforms confirming that, although artificial structures attract and support species typical of hard bottoms, they are not analogues of natural rocky habitats.

Determining the native region of the putatively invasive ascidian Didemnum vexillum Kott, 2002

Over the past 40years, an increasing number of previously unrecorded populations of a colonial ascidian, recently identified as Didemnum vexillum, have been documented in most temperate coastal regions of the world, impacting aquaculture operations, natural rocky habitats, cobble/gravel substrates, and eelgrass beds. The earliest sample thought to be D. vexillum was collected in Mutsu Bay, Japan in 1926, but was not identified to species at the time. Lack of a published description led to widespread mis-identification of this species. Because of incomplete historical records and the numerous mis-identifications of this species, the native range of D. vexillum has not been conclusively known. To determine which portion of the current known range of D. vexillum is within its native region, we obtained DNA sequences of two genes, cytochrome c oxidase subunit 1(co1; mitochondrial) and THO complex subunit (tho2; nuclear), from 365 and 75 samples of D. vexillum from around the world, respectively. Both population genetics (co1 only) and phylogenetics (co1 and tho2) were used to measure and compare the amount of genetic variation contained in each region where D. vexillum is currently found (Eastern North America, Japan, New Zealand, Northwestern Europe, and Western North America). We found that genetic diversity in Japan was greater than in any other region. Northwestern Europe, western North America, and New Zealand all showed evidence of having recently undergone a genetic bottleneck. The gene tree for co1 in D. vexillum was divided into three clades: one which is found globally; the other two found only in Japan. Analysis of a partial genomic sequence of the nuclear gene tho2 confirmed that the co1 clades belong to the same species. In agreement with the sparse historical data, the molecular evidence suggests that Japan lies within the native range of D. vexillum.