Observations on variation in skull size of three mammals in Israel during the 20th century

Among mammals, food availability, especially during the growth period, is a key predictor in determining final body size, and improved nutrition may lead to an increase in their body size. In Israel during the last century food availability for animals commensal with humans increased greatly, due to a 16-fold increase in the human population and the accompanying changes, such as a 135-fold increase in the area of irrigated agriculture and the availability of large quantities of organic garbage.Using museum material, we studied temporal changes in skull size of a sample of 89 red foxes (Vulpes vulpes Linnaeus, 1758), 108 golden jackals (Canis aureus Linnaeus, 1758) and 117 Cape hares (Lepus capensis Linnaeus, 1758) collected during the 20th century. Four measurements (condylobasal length, zygomatic breadth, the length of the upper cheek teeth row and the length of the mandible) were taken for each skull, and principal component analysis was used to combine the measurements into principal components.We found that skull size of the red fox increased significantly during the 20th century, possibly due to improved food availability from man-made resources such as agricultural produce and garbage. No temporal trend in body size was detected for the jackal and hare. These differences are discussed.     

Ecological Meltdown in the Firth of Clyde,Scotland: Two Centuries of Change in a Coastal Marine Ecosystem

Background

The Firth of Clyde is a large inlet of the sea that extends over 100 km into Scotland''s west coast.

Methods

We compiled detailed fisheries landings data for this area and combined them with historical accounts to build a picture of change due to fishing activity over the last 200 years.

Findings

In the early 19^th century, prior to the onset of industrial fishing, the Firth of Clyde supported diverse and productive fisheries for species such as herring (Clupea harengus, Clupeidae), cod (Gadus morhua, Gadidae), haddock (Melanogrammus aeglefinus, Gadidae), turbot (Psetta maxima, Scophthalmidae) and flounder (Platichthys flesus, Pleuronectidae). The 19^th century saw increased demand for fish, which encouraged more indiscriminate methods of fishing such as bottom trawling. During the 1880s, fish landings began to decline, and upon the recommendation of local fishers and scientists, the Firth of Clyde was closed to large trawling vessels in 1889. This closure remained in place until 1962 when bottom trawling for Norway lobster (Nephrops norvegicus, Nephropidae) was approved in areas more than three nautical miles from the coast. During the 1960s and 1970s, landings of bottomfish increased as trawling intensified. The trawl closure within three nautical miles of the coast was repealed in 1984 under pressure from the industry. Thereafter, bottomfish landings went into terminal decline, with all species collapsing to zero or near zero landings by the early 21^st century. Herring fisheries collapsed in the 1970s as more efficient mid-water trawls and fish finders were introduced, while a fishery for mid-water saithe (Pollachius virens, Gadidae) underwent a boom and bust shortly after discovery in the late 1960s. The only commercial fisheries that remain today are for Nephrops and scallops (Pecten maximus, Pectinidae).

Significance

The Firth of Clyde is a marine ecosystem nearing the endpoint of overfishing, a time when no species remain that are capable of sustaining commercial catches. The evidence suggests that trawl closures helped maintain productive fisheries through the mid-20^th century, and their reopening precipitated collapse of bottomfish stocks. We argue that continued intensive bottom trawling for Nephrops with fine mesh nets will prevent the recovery of other species. This once diverse and highly productive environment will only be restored if trawl closures or other protected areas are re-introduced. The Firth of Clyde represents at a small scale a process that is occurring ocean-wide today, and its experience serves as a warning to others.     

Tempestitic shell beds formed by a new serpulid polychaete from the Bajocian (Middle Jurassic) of the Central High Atlas (Morocco)

Serpulid-dominated shell beds from the Lower Bajocian (Middle Jurassic) of the Central High Atlas (Morocco) are primarily formed by quadrangular tubes of the serpulid polychaete Nogrobs moroccensis sp. nov. The transverse tube ornament consisting predominately of wrinkles, the lack of narrow spirals and the shortness or absence of attached posterior tube portion represent the diagnostic features of this new species. Tubes of Nogrobs moroccensis co-occur with gastropods and oyster–crinoidal debris. We suggest that these serpulids were free-lying in their adult stage and formed benthic meadows on soft-bottom habitats. They frequently show parallel alignment in plane views in both graded and non-graded, few-cm-thick shell beds, corresponding to distal tempestites deposited close to and below storm wave base in an outer-ramp environment. The excellent preservation of serpulids implies short residence time on the seafloor, and the lack of compositional mixing with other communities and their restriction to outer-ramp habitats indicate that they represent parautochthonous assemblages. Analyses of serpulid orientation on the bottom bedding planes of shell beds revealed weak unidirectional arrangement of tubes, whereas orientation on the top bedding planes revealed strong unidirectional arrangement of tubes, with significantly different orientation relative to the bottom planes. This change could suggest a shift from predominantly a current component of the combined storm flow (with uneven seafloor surface and adhesion of skeletal grains to muddy substrate) to significant oscillatory component of the waning storm, as also suggested by bidirectional orientation of gastropods.     

Diet and Habitat use by Bluefish, Pomatomus Saltatrix, in a Chesapeake Bay Estuary

Bluefish, Pomatomus saltatrix, are recreationally valuable finfish along the Atlantic seaboard and in the Chesapeake Bay. Diet and habitat use patterns for bluefish life history intervals in Chesapeake Bay estuaries are poorly described although it is widely acknowledged that this apex piscivorous species relies on estuarine habitat for feeding and nursery grounds after oceanic spawning and inshore migration of larvae. Bluefish diet, distribution, and abundance patterns were examined in relation to oyster reef, oyster bar, and sand bottom habitat in the Piankatank River, Virginia. Bluefish from all sites were predominantly piscivorous and were more abundant at reef sites than non-reef sites. Bluefish caught in association with the oyster reef consumed a wider diversity of prey items than fish from other sites; diet diversity may contribute to bluefish success during periods when small pelagic food fish abundance is reduced. Bluefish estuarine habitat use is positively correlated with the presence of oyster shell habitat and the complex trophic communities centering on oyster reefs.     

Feeding behaviour of Black Sea bottom fishes: Did it change over time?

This study was designed to improve knowledge in feeding behaviour of the round goby (Apollonia melanostomus (Pallas, 1814)), the red mullet (Mullus barbatus ponticus Essipov, 1927), the whiting (Merlangius merlangus (Linnaeus, 1758)), the flounder (Platichthys flesus (Linnaeus, 1758)), the sole (Solea solea (Linnaeus, 1758)), the turbot (Psetta maeotica (Pallas, 1814)) and the starry sturgeon (Acipenser stellatus Pallas, 1771) from the north-western Black Sea. Gut content coupled with stable isotope analysis allowed describing food web variations according to species, in two seasons and at two areas located seawards the Danube River. Present results showed that most fishes have likely changed their feeding behaviour compared to past studies from the same area. Trophic niches were reduced and dietary overlap was common, as different fish species consumed the same dominant prey types. Fishes probably adapted their feeding behaviour to the increasingly low biodiversity of the Black Sea communities.     

Evidence for Distinct Coastal and Offshore Communities of Bottlenose Dolphins in the North East Atlantic

Bottlenose dolphin stock structure in the northeast Atlantic remains poorly understood. However, fine scale photo-id data have shown that populations can comprise multiple overlapping social communities. These social communities form structural elements of bottlenose dolphin (Tursiops truncatus) populations, reflecting specific ecological and behavioural adaptations to local habitats. We investigated the social structure of bottlenose dolphins in the waters of northwest Ireland and present evidence for distinct inshore and offshore social communities. Individuals of the inshore community had a coastal distribution restricted to waters within 3 km from shore. These animals exhibited a cohesive, fission-fusion social organisation, with repeated resightings within the research area, within a larger coastal home range. The offshore community comprised one or more distinct groups, found significantly further offshore (>4 km) than the inshore animals. In addition, dorsal fin scarring patterns differed significantly between inshore and offshore communities with individuals of the offshore community having more distinctly marked dorsal fins. Specifically, almost half of the individuals in the offshore community (48%) had characteristic stereotyped damage to the tip of the dorsal fin, rarely recorded in the inshore community (7%). We propose that this characteristic is likely due to interactions with pelagic fisheries. Social segregation and scarring differences found here indicate that the distinct communities are likely to be spatially and behaviourally segregated. Together with recent genetic evidence of distinct offshore and coastal population structures, this provides evidence for bottlenose dolphin inshore/offshore community differentiation in the northeast Atlantic. We recommend that social communities should be considered as fundamental units for the management and conservation of bottlenose dolphins and their habitat specialisations.     

Palaeoecological analysis of a sclerobiont fauna on a single basibiont across the Valanginian of the Neuquén Basin,west‐central Argentina

Sclerobiont communities have proven their environmental and taphonomic value in extant and past settings; studies are beginning to quantify and evaluate their changes across time. Through the Valanginian of the Neuquén Basin, Argentina, trigonioids of the genus Steinmanella present an almost continuous record. Materials were collected from shales and shell beds across second‐order systems tracts (LST, TST and HST). Their sclerobiont communities were characterized and compared across systems tracts and facies. In addition, a link between them and coeval oyster mass occurrences (OMOs) was investigated, since studies on other local sclerobiont communities have consistently shown pronounced oyster dominance. Eleven sclerobiont taxa were found on Steinmanella (bryozoans, bivalves, foraminifers and polychaetes), of which oysters are usually strongly dominant but for the TST, in which their dominance is diminished. The sclerobiont community has a simple structure and interspecific relationships and competition for space seem to have had little importance. Few differences in richness, taxonomy and other parameters were found between facies. Across systems tracts, features of the sclerobiont communities are differentiated mostly from swings in relative abundance of taxa. The lowered oyster dominance in the TST may reflect a source–sink dynamics between OMOs (sources) and Steinmanella as sinks in shallower, soft substrate settings. Likely the sea‐level rise temporally drowned the oyster carbonate factory, resulting in decreased larvae emigration to the sinks and lowered oyster dominance during the TST.     

Detection of environmental impacts by bottom trawling onPosidonia oceanica (L.) Delile meadows: sensitivity of fish and macroinvertebrate communities

Along the Mediterranean coast,Posidonia oceanica (L.) Delile meadows have a great ecological and economical importance. However, there is a general regression of these meadows due to human activities such as illegal bottom trawling, may be affecting to overall ecosystem health. We examined changes in the community structure of mobile fauna associated withP. oceanica meadows at different spatial scales and taxonomic levels. The aim of this paper was to identify the most efficient taxonomic level to use in environmental impact studies of bottom trawling. At the macroscale level (10 to 100 m), there were significant differences between sites in the densities of some fish species and also the total fish assemblage structure, at both family and species taxonomical levels. At the microscale (0.1 to 1 m), some species of amphipods and isopods showed significant differences in their population densities. In the overall analysis of community structure, the coarse taxonomical levels, such as phyla and class, did not show significant differences, however amphipods and isopods showed significant differences at family and species levels. From these results, both study scales are required to detect changes onPosidonia meadows' fauna. Monitoring of some fish species such asDiplodus annularis (Linnaeus, 1758) and the overall fish assemblage as well as the structure of the amphipod and isopod communities appears to be the most efficient tool in the assessment of environmental impacts by bottom trawling onP. oceanica meadows.     

Taxonomic composition and species diversity of insect assemblages in grass–shrub cover of peat bogs in Belarus

The species composition and diversity of insect assemblages in the grass–shrub cover has been studied. A total of 374 species from 10 orders have been revealed. Coleoptera, Diptera, Heteroptera, and Auchenorryncha prevailed. Each order was dominated by two to eight species. These species are Cixius similis Kirschbaum, 1868; Neophilaenus lineatus (Linnaeus, 1758); Lepyronia coleoptrata (Linnaeus, 1758) (Auchenorryncha); Lygus pratensis (Linnaeus, 1758); Kleidocerys resedae (Panzer, 1797); Stictopleurus crassicornis (Linnaeus, 1758) (Heteroptera); Lochmaea suturalis (Thomson, 1866); Cyphon padi (Linnaeus, 1758); Plateumaris discolor (Herbst, 1795) (Coleoptera); etc. The assemblages were characterized by low species diversity and distribution of species abundance. The most similar entomocomplexes were those in biotopes dominated by herbs, on the one hand, and dwarf shrubs, on the other. The regression analysis has shown a significant relation between the species richness and diversity of insects and the species composition of plants and their projective cover. The multivariate analysis with various methods (CCA and PCA) demonstrated the influence of these factors on the spatial distribution of certain species and their preferences to particular habitats.     

Changes in species diversity and size composition in the Firth of Clyde demersal fish community (1927-2009)

Following the repeal in 1962 of a long-standing ban on trawling, yields of demersal fish from the Firth of Clyde, southwest Scotland, increased to a maximum in 1973 and then declined until the directed fishery effectively ceased in the early 2000s. Since then, the only landings of demersal fish from the Firth have been by-catch in the Norway lobster fishery. We analysed changes in biomass density, species diversity and length structure of the demersal fish community between 1927 and 2009 from scientific trawl surveys, and related these to the fishery harvesting rate. As yields collapsed, the community transformed from a state in which biomass was distributed across numerous species (high species evenness) and large maximum length taxa were common, to one in which 90 per cent of the biomass was vested in one species (whiting), and both large individuals and large maximum length species were rare. Species evenness recovered quickly once the directed fishery ceased, but 10 years later, the community was still deficient in large individuals. The changes partly reflected events at a larger regional scale but were more extreme. The lag in response with respect to fishing has implications for attempts at managing a restoration of the ecosystem.     

Early faunal successional patterns in artificial reefs used for restoration of impacted biogenic habitats

This study describes the early epifaunal succession associated with an artificial reef constructed to regenerate damaged biogenic habitats formed by Modiolus modiolus (Linnaeus, 1758). Clumps of live M. modiolus were translocated onto three treatments: flattened cultch, elevated cultch, and directly onto the sea floor. Photographic surveys were carried out 1, 6, and 12 months after completion of the experimental array to test the hypothesis that the artificial reef would enhance habitat complexity thus increasing biodiversity and accelerating faunal community succession. These effects were predicted to be greater on elevated cultch due to higher level of protection and greater accessibility to food compared to sea floor treatments. Univariate analysis indicated that after 12 months the artificial reef had developed a significantly richer and more diverse community compared to 1- and 6-month stages. Multivariate analysis revealed a significant temporal shift in species composition from mobile taxa to sessile and interstitial macroinvertebrates as the artificial reef settled. Reef elevation offered no significant advantages for the development of the epifaunal assemblage. Although further regular monitoring is advisable, this study demonstrated that translocation of a foundation species can help restore marine benthic habitats through the development of a diverse community in a relatively short time.     

Effects of chronic bottom trawling disturbance on benthic biomass, production and size spectra in different habitats

Bottom trawling has widespread impacts on benthic communities and habitats. It is argued that the impact of chronic bottom trawling on benthic infauna depends on the natural disturbance levels to which benthic communities are adapted. We analysed biomass, production and size structure of two communities from a muddy and a sandy habitat, in relation to quantified gradients of trawling disturbance on real fishing grounds. We used an allometric relationship between body mass and individual production to biomass ratio to estimate community production. Chronic trawling had a negative impact on the biomass and production of benthic communities in the muddy habitat, while no impact was identified on benthic communities from the sandy habitat. These differences are the result of differences in size structure within the two communities that occur in response to increasing trawling disturbance.     

Redescription of Alcyonidium my till Dalyell, 1848 (Bryozoa: Gtenostomatida)

Reproduction in the ctenostomate bryozoan Alcyonidium mytili Dalyell, 1848, was studied over 2 years, revealing confusion in the literature over the diagnostic characters of the species and incorrect assumptions about the mode of reproduction. The literature is briefly reviewed and an approximate type locality from the Firth of Forth, Scotland, is identified. Alcyonidium mytili is comprehensively redescribed from material collected in the Firth of Forth and from 2 years' collections in the Daugleddau estuary, near Pembroke Dock, South Wales. Zooid and polypide dimensions and modal tentacle number (16) have been determined from large samples. Most importantly A. mytili possesses a conspicuous intertentacular organ when reproductive; is oviparous, with eggs discharged through the intertentacular organ developing into cyphonautes larvae; and has a prolonged winter reproductive period. The contrary indications in the literature are a consequence of confusion with a superficially similar but larviparous species.     

The decapod community from the Early Pliocene (Zanclean) of “La Serra” quarry (San Miniato,Pisa, Toscana,central Italy): sedimentology,systematics, and palaeoenvironmental implications

We report an unusual and rich decapod crustacean assemblage from the early Pliocene (Zanclean), recently collected during the excavations of the “La Serra” quarry, located in La Serra, near San Miniato, Pisa (Toscana, central Italy). The studied specimens have been assigned, as follows: Axius sp., Callianassa chalmasii Brocchi, 1883, and Calliaxina cf. C. punica ( de Saint Laurent and Manning, 1982) (infraorder Axiidea de Saint Laurent, 1979); Gebiacantha tuscia Garassino, Pasini, De Angeli and Charbonnier sp. nov. (infraorder Gebiidea de Saint Laurent, 1979); Pagurus alatus Fabricius, 1775, and Pagurus sp. (infraorder Anomura MacLeay, 1838); Dromia neogenica Müller, 1978, Dromia sp., Medorippe cf. M. ampla Garassino, De Angeli, Gallo and Pasini, 2004, Ilia nucleus ( Linnaeus, 1758), Ristoria pliocaenica (Ristori, 1891), Pisa armata ( Latreille, 1803), Macropodia sp., Maja squinado (Herbst, 1788), Derilambrus angulifrons ( Latreille, 1825), Atelecyclus undecimdentatus (Herbst, 1783), Liocarcinus sp., Thalamita italica Garassino, Pasini, De Angeli and Charbonnier sp. nov., Pilumnus cf. P. hirtellus (Linnaeus, 1761), Eriphia cocchii Ristori, 1886, Goneplax rhomboides ( Linnaeus, 1758), Goneplax sacci Crema, 1895, (infraorder Brachyura Linnaeus, 1758). Moreover, two specimens have been assigned to callianassideans sensu lato and 13 specimens to indeterminate axiideans. Calliaxina Ngoc-Ho, 2003, Gebiacantha Ngoc-Ho, 1989, Ristoria Garassino, Pasini, De Angeli and Charbonnier gen. nov., and Macropodia Leach, 1814, are reported for the first time in the fossil record and the extant Pagurus alatus, Ilia nucleus, Pisa armata, Derilambrus angulifrons, and Pilumnus cf. P. hirtellus, are reported in the fossil record from the Pliocene. Everywhere “La Serra” quarry bio-community is very important, representing one of the richest and most diversified crustacean faunas from the Pliocene reported to date in the Mediterranean basin and worldwide, increasing notably the knowledge on the decapod populations and distribution during the early Pliocene. This community is indicative of a palaeoenvironment of shallow sublittoral water, with sandy-muddy and alternate hard shell bottom, partially covered or in proximity of seagrass, similar to the extant Mediterranean Posidonia beds, mainly inhabited by fossorial and benthonic decapods.     

The component helminth community in six sympatric species of Ardeidae

We studied the helminth communities in 6 sympatric species of Ardeidae (Ixobrychus minutus (Linnaeus, 1766), Nycticorax nycticorax (Linnaeus, 1758), Bubulcus ibis (Linnaeus, 1758), Egretta garzetta (Linnaeus, 1766), Ardea cinerea (Linnaeus, 1758), and Ardea purpurea (Linnaeus, 1766)) from "La Albufera de Valencia," Spain. The survey revealed 13 species of helminth parasites: 5 digeneans, 2 cestodes, and 6 nematodes. The component helminth communities of the Ardeidae examined are depauperate and conform to the pattern typically found in isolationist communities, probably because of their high trophic dependence on a few prey species. Evenness was positively correlated with richness and abundance, but host body weight was not correlated with the number of helminth species or with the total number of helminths. Ardea cinerea is more heavily infected than E. garzetta by Apharyngostrigea cornu, and B. ibis is more heavily infected than both Ardea cinerea and E. garzetta by Desportesius spinulatus. Apharyngostrigea cornu was positively associated with Desmidocercella numidica and D. spinulatus in A. cinerea.     

An experience of rearing some hawk moths (Lepidoptera,Sphingidae) on artificial diets

A method for rearing five hawk moth species, namely Acherontia atropos (Linnaeus, 1758), A. lachesis (Fabricius, 1798), Agrius convolvuli (Linnaeus, 1758), Daphnis nerii (Linnaeus, 1758), and Hyles livornica (Esper, 1780) (Lepidoptera, Sphingidae) on artificial diets is described. Two recipes of these artificial rearing media are proposed. Special attention is given to maintenance of adult moths in captivity and raising immature stages.     

Biochemical studies on Brachionus plicatilis: hydrolytic enzymes,integument proteins and composition of trophi

In Terminos Lagoon, México, more than 80 fish species use the mangrove and seagrass habitats. We studied nekton dynamics in an inlet seagrass system and a more sheltered seagrass/mangrove system located behind a barrier island. Seasonal community biomass ranges from 0.6 to 5.2 g wet wt m^-2. For the two habitats together, there are 28 dominant species. Eleven species were common to both areas: Sphoeroides testudineus (Linnaeus, 1758), Archosargus rhomboidalis Linnaeus, 1758, A. probatocephalus (Walbaum, 1792), Arius felis (Linnaeus, 1766), A. melanopus (Gunther, 1864), Eucinostomus gula (Cuvier & Valenciennes, 1830), Bairdiella chrysoura (Lacépède, 1803), Orthopristis chrysoptera (Linnaeus, 1766), Chilomycterus schoepfi (Walbaum, 1792), Opsanus beta (Goode & Bean, 1879) and Lutjanus griseus (Linnaeus, 1758). Ten species used exclusively the inlet seagrass system: Urolophus jamaicensis (Cuvier, 1817), Haemulon aurolineatum (Cuvier, 1829), H. bonariense (Cuvier, 1830), H. plumieri (Lacépède, 1802), Anisotremus virginicus (Linnaeus, 1758), Odontoscion dentex (Cuvier, 1830), Corvula sanctae-luciae (Jordan, 1890), Nicholsina usta (Valenciennes, 1839), Stephanolepis hispidus (Linnaeus, 1766) and Diodon hystrix Linnaeus, 1758. Seven species were dominant only in the seagrass/mangrove system: Anchoa mitchilli (Cuvier & Valenciennes, 1848), Scorpaena plumieri Bloch, 1789, Cynoscion nebulosus (Cuvier & Valenciennes, 1830), Diapterus rhombeus (Cuvier & Valenciennes, 1830), Bairdiella ronchus (Cuvier & Valenciennes, 1830), Cichlasoma urophtalmus (Günther, 1862) and Acanthostracion quadricornis (Linnaeus, 1758). Comparative analysis showed that periodic variation in biomass and diversity of fish assemblages in seagrass and seagrass/mangrove habitats were synchronized with sizes and densities of population, season of the year (dry, wet, ‘nortes’), circulation pattern, and patterns of primary production (phytoplankton, Thalassia testudinum Konig, 1805; and Rhizophora mangle Linnaeus). This analysis allowed the definition of 3 life-cycle patterns with a clear nektonic ‘seasonal programming’ following the timing of primary production in these critical habitats: (1) marine species which spawn in or near the inlet with eggs and larvae transported into and distributed throughout the lagoon by the predominant currents; (2) estuarine-marine species which spawn in different habitats of the lagoon and use the seagrass/mangrove system as a nursery area, and (3) species which complete their life history in the inlet seagrass and/or seagrass/mangrove systems. EPOMEX Program Contribution No. 0026.     

Influence of an Oyster Reef on Development of the Microbial Heterotrophic Community of an Estuarine Biofilm

We characterized microbial biofilm communities developed over two very closely located but distinct benthic habitats in the Pensacola Bay estuary using two complementary cultivation-independent molecular techniques. Biofilms were grown for 7 days on glass slides held in racks 10 to 15 cm over an oyster reef and an adjacent muddy sand bottom. Total biomass and optical densities of dried biofilms showed dramatic differences for oyster reef versus non-oyster reef biofilms. This study assessed whether the observed spatial variation was reflected in the heterotrophic prokaryotic species composition. Genomic biofilm DNA from both locations was isolated and served as a template to amplify 16S rRNA genes with universal eubacterial primers. Fluorescently labeled PCR products were analyzed by terminal restriction fragment length polymorphism, creating a genetic fingerprint of the composition of the microbial communities. Unlabeled PCR products were cloned in order to construct a clone library of 16S rRNA genes. Amplified ribosomal DNA restriction analysis was used to screen and define ribotypes. Partial sequences from unique ribotypes were compared with existing database entries to identify species and to construct phylogenetic trees representative of community structures. A pronounced difference in species richness and evenness was observed at the two sites. The biofilm community structure from the oyster reef setting had greater evenness and species richness than the one from the muddy sand bottom. The vast majority of the bacteria in the oyster reef biofilm were related to members of the γ- and δ-subdivisions of Proteobacteria, the Cytophaga-Flavobacterium -Bacteroides cluster, and the phyla Planctomyces and Holophaga-Acidobacterium. The same groups were also present in the biofilm harvested at the muddy sand bottom, with the difference that nearly half of the community consisted of representatives of the Planctomyces phylum. Total species richness was estimated to be 417 for the oyster reef and 60 for the muddy sand bottom, with 10.5% of the total unique species identified being shared between habitats. The results suggest dramatic differences in habitat-specific microbial diversity that have implications for overall microbial diversity within estuaries.     

Distribution of skates and sharks in the North Sea: 112 years of change

How have North Sea skate and shark assemblages changed since the early 20th century when bottom trawling became widespread, whilst their environment became increasingly impacted by fishing, climate change, habitat degradation and other anthropogenic pressures? This article examines long‐term changes in the distribution and occurrence of the elasmobranch assemblage of the southern North Sea, based on extensive historical time series (1902–2013) of fishery‐independent survey data. In general, larger species (thornback ray, tope, spurdog) exhibited long‐term declines, and the largest (common skate complex) became locally extirpated (as did angelshark). Smaller species increased (spotted and starry ray, lesser‐spotted dogfish) as did smooth‐hound, likely benefiting from greater resilience to fishing and/or climate change. This indicates a fundamental shift from historical dominance of larger, commercially valuable species to current prevalence of smaller, more productive species often of low commercial value. In recent years, however, some trends have reversed, with the (cold‐water associated) starry ray now declining and thornback ray increasing. This shift may be attributed to (i) fishing, including mechanised beam trawling introduced in the 1960s–1970s, and historical target fisheries for elasmobranchs; (ii) climate change, currently favouring warm‐water above cold‐water species; and (iii) habitat loss, including potential degradation of coastal and outer estuarine nursery habitats. The same anthropogenic pressures, here documented to have impacted North Sea elasmobranchs over the past century, are likewise impacting shelf seas worldwide and may increase in the future; therefore, parallel changes in elasmobranch communities in other regions are to be expected.