Nouvelles données micropaléontologiques(Foraminifères planctoniques et petits Foraminifères benthiques) sur le stratotype bordelais du Burdigalien

The present work deals with the microfauna of small benthonic and planktonic Foraminifera from the Burdigalian stratotype of Aquitaine basin (France) and from a few outcrops in the stratotype vicinity showing the upper or lower boundary of the stratotype.Benthonic fauna is rich: more than 250 species divided in 92 genera have been collected. The most frequent are hyaline Foraminifera (Pararotalia, Elphidium, Asterigerina, Florilus, Virgulopsis, Bolivina). The miocene feature is more pronounced than in the Aquitanian stratotype.Planktonic Foraminifera are much less abundant:only 20 species. However, some of them authorize to place the stratotype (or its equivalent l. s.) in N5 Blow's zone and perhaps in the basel N6 zone.The figurations of many species are made withthe scanning electronic microscope.     

Relationship of Foraminifera and thecamoebian distributions to sediments contaminated by pulp mill effluent: Saguenay Fiord, Quebec, Canada

Gravity cores and grab samples collected in the Saguenay Fiord between 1976 and 1988 contain the record of a 20th century benthic marine environment contaminated primarily by organic matter discharges from several local pulp and paper mills.Spiroplectammina biformis is the dominant arenaceous species. Its living percent abundance decreases between 1982 and 1988 as a consequence of the apparent recolonization of the upper reaches of the fiord by several arenaceous taxa, the most important beingTextularia earlandi. Cassidulina reniforme, the dominant living calcareous species, shows about a three fold increase in relative abundance over the six year interval. Grab sample observations also suggest a recolonization of some formerly barren benthic environments near the head of the fiord by foraminiferal species between 1982 and 1988. This recolonization may reflect the combined effect of government regulations imposed on local industrial polluters in the early 1970's and the capping of a large area of contaminated sediment by a layer of clay that was transported to the basin at the head of the fiord as the result of a catastrophic landslide in 1971.X-radiographs of core sections from a basin at the head of the fiord show sharp laminations that reflect both the absence of bioturbators and the seasonal variation of fluvial depositional processes. Organic waste deposition from pulp and paper mill outfalls first increased around 1910 and shows a first order inverse relationship to benthonic foraminiferal assemblage diversity. The presence of only allochthonous thecamoebian and reworked planktonic Foraminifera tests in many benthonic Foraminifera-barren core intervals supports the idea that common indigenous estuarine species such asSpiroplectammina biformis were excluded from these areas at certain times as a consequence of pollution “stress” rather than having been removed from the sediment record as a result of post-depositional diagenetic effects. However, future studies of estuarine pollution history based on proxy foraminiferal data from cores must give greater emphasis to distinguishing ecological stress responses from diagenetic process (i.e. test dissolution effects) since both mechanisms can be reflected in the proxy pollution “signal” in a similar way.     

Nouvelles données micropaléontologiques(Foraminifères planctoniques et petits Foraminifères benthiques) sur le stratotype de l'Aquitanien

The authors study the microfauna of small benthonic and planktonic Foraminifera from the Aquitanian stratotype and of a few exposures in the stratotype vicinity.Benthonic microfauna is rich: more than 150species have been collected; among them Miliolidae mainly belonging to the genera Quinqueloculina and Miliola.Planktonic Foraminifera are much less abundant:only 20 species. They authorize to place the stratotype at the boundary of N4–N5 Blow's zones.The figurations of many species are made withthe scanning electronic microscope.     

The influence of freshwater flows on two estuarine resident fish species show differential sensitivity to the impacts of drought,flood and climate change

Estuaries are particularly susceptible to climate change and drought resulting in atypical changes to freshwater flows. How such changes in flow impact on the ecology of estuarine fishes may depend on how a species moves in response to changing flow conditions. Acoustic telemetry was used to interpret fine-scale movements of two co-inhabiting estuarine fish species, black bream, Acanthopagrus butcheri and estuary perch, Macquaria colonorum in relation to freshwater flows, season and moon phase. We found black bream to be highly mobile, regularly travelling the length of the estuary and into the neighbouring estuaries. In contrast, estuary perch had particular home ranges and made occasional, upstream or downstream movements. Possibly influenced by freshwater flows, estuary perch moved at greater rates in the Tambo compared to fish in the Mitchell. Black bream resided in the upper estuary during winter and spring and the lower estuary during summer and autumn, whereas estuary perch remained in the upper estuary throughout the year, with occasional downstream movements in winter and spring. This study revealed 1) significantly large increases in freshwater flows result in mass downstream movements in both species, 2) fish moved upstream during full moons and 3) there are contrasting spatio-temporal patterns in movement between species. The results from this study highlight that estuarine fishes are likely to show differential sensitivity to the impacts of drought and climate change and illustrate how acoustic telemetry methods can be used to determine the environmental needs of fishes and help efforts to conserve and manage estuaries worldwide.     

Description de Pseudolituonella? guerneti,nov. sp., nouveau foraminifere benthonique du Cenomanien d'Eubee (Grece)

A new benthonic Foraminifera: Pseudolituonella? guerneti n. sp. (Ataxophragmiidae) has been found in upper cenomanian limestones of central Eubee (Greece, pelagonian zone). It is described and illustrated in this publication.     

Spatial distribution and trophic ecology of dominant copepods associated with turbidity maximum along the salinity gradient in a highly embayed estuarine system in Ariake Sea, Japan

The present study aimed to investigate into the feeding ecology of the dominant copepods along a salinity gradient in Chikugo estuary. Copepod composition was studied from samples collected from stations positioned along the salinity gradient of the estuary. Copepod gut pigment concentrations were measured by fluorescence technique and hydrographical parameters such as temperature, salinity, transparency, suspended particulate matter (SPM); pigments such as chlorophyll-a (Chl-a), phaeopigment; and particulate nutrients such as particulate organic carbon (POC) and particulate organic nitrogen (PON) were measured. Two distinct zones in terms of nutrient and pigment concentrations as well as copepod distribution and feeding were identified along the estuary. We identified a zone of turbidity maximum (TM) in the low saline upper estuary which was characterized by having higher SPM, higher POC and PON but lower POC:PON ratios, higher pigment concentrations but lower Chl-a/SPM ratios and higher copepod dry biomass. Sinocalanus sinensis was the single dominant copepod in low saline upper estuary where significantly higher concentrations of nutrients and pigments were recorded and a multispecies copepod assemblage dominated by common coastal copepods such as Acartia omorii, Oithona davisae and Paracalanus parvus was observed in the lower estuary where nutrient and pigment concentrations were lower. Copepods in the estuary are predominantly herbivorous, feeding primarily on pigment bearing plants. However, completely contrasting trophic environments were found in the upper and the lower estuary. It was speculated from the Chl-a and phaeopigment values that copepods in the upper estuary receive energy from a detritus-based food web while in the lower estuary an algal-based food web supports copepod growth. Overall, the upper estuary was identified to provide a better trophic environment for copepod and is associated with higher SPM concentrations and elevated turbidity. The study demonstrates the role of estuarine turbidity maximum (ETM) in habitat trophic richness for copepod feeding. The study points out the role of detritus-based food web as energy source for the endemic copepod S. sinensis in the upper estuary, which supports as nursery for many fish species.     

Fish assemblage structure in an estuary of the Atlantic Forest biodiversity hotspot (southern Brazil)

We described the fish assemblage in the estuary of the Guaraguaçu River (one of the largest tributaries of the Paranaguá Bay Estuary, located within Brazil’s Atlantic Forest Biosphere Reserve) from June 2005 to May 2006, and assessed the seasonal and spatial effects of abiotic environmental attributes on the fish assemblage structure. Despite some oscillations in salinity, the upper and lower estuaries had year-round persistent oligohaline and polyhaline conditions, respectively. Despite high species richness (55 species), the Guaraguaçu River Estuary fish community contains a few dominant taxa; 11% of the richness accounts for >60% of its density and biomass. The most abundant species (in terms of both biomass and density) was Atherinella brasiliensis. Species whose densities were most strongly associated with the upper estuary were Centropomus parallelus, Ctenogobius schufeldti, Eucinostomus melanopterus, Platanichthys platana, Trinectes paulistanus, and Eugerres brasilianus. Those whose densities were most strongly associated with the lower estuary were A. brasiliensis, Sphoeroides greeleyi, Eucinostomus argenteus, Sphoeroides testudineus, Diapterus rhombeus, and Harengula clupeola. Throughout the year, canonical correspondence analysis identified: (1) the pattern of horizontal stratification of salinity along the river as being the most important variable for explaining most of the fish fauna structure; and (2) a strong relationship between the fish fauna and the salinity gradient along the estuary. Analysis of similarity further confirmed that each estuarine zone supports a year-round persistent and relatively homogeneous fish species assemblage. Total mean density and biomass remained constant over time in each estuarine habitat, but density shifted in the most abundant species, which appears related to recruitment patterns. Such species and abundance persistence likely occurs because seasonal rainfall-induced changes in river discharge are not sufficient to significantly shift runoff and salinity and thus fish assemblage structure (species composition, density and biomass) along the estuary. Such a lack of seasonal fish fauna movement as a response to changes in river flow contrasts with other estuarine systems around the world.     

Foraminiferes benthiques et bathymetrie: Le cenozoique du golfe de gascogne

Benthonic foraminifera are studied in the limited area of the Bay of Biscay and the present Aquitanian coasts.Recent populations have been dredged between 0 and 4450 m; their associations show a bathymetric zonation: faunas from an estuary (Gironde); in-shore and off-shore shelf; upper, middle and lower continental slope; abyssal fauna. The distribution of agglutinated Foraminifera and size/architectural variations of shells are also useful for bathymetrical zonation.Cenozoic Foraminifera are studied in two continental and four off-shore drillings in the Bay of Biscay and Aquitaine Basin. Results of recent faunal studies are used to select some species among the whole Tertiary population; main bathymetric associations are found that can illustrate the history of the Aquitanian area from Eocene to Recent. Two different areas can be described: a southern one with the Gouf' de Cap Breton and its anyon facies; a northern one with a continental margin which progrades to the west and is disturbed by the Pyrenean tectonic movements.It is only possible to make such a study in a restricted area, where water masses have almost constant bathymetric limits.     

Prey selection by flounder, Platichthys flesus, in the Douro estuary, Portugal

Prey selection by the flounder, Platichthys flesus (Linnaeus, 1758), in an estuarine nursery was investigated and the major factors influencing food choice by this species were assessed. Diet breadth was narrow, reflecting the low prey diversity observed in the benthos. A gradual ontogenetic shift from small prey such as amphipods to larger prey like polychaetes and bivalves was observed. Amphipods had positive electivity values in the upper estuary and negative values in the lower estuary.Polychaetes showed the inverse pattern. Bivalve electivity values were always positive. Differential selectivity throughout the estuary was mainly related to spatial segregation of flounders according to size, with the smaller individuals concentrating in the upper estuary and larger individuals concentrating in the lower estuary. Amphipods such as Corophium spp. play a crucial role in the flounder diet because of their small size, low mobility and diel activity pattern. As prey, the polychaete value increases throughout flounder ontogeny since the flounder size range is compatible with the larger mouth gapes and detection ability of larger fish. Bivalve electivity values for flounder are mainly related to high calorific values. The absence of Crangon crangon (Linnaeus, 1758) in the diet may be due to low water temperature since the cost–benefit involved in the capture of highly mobile prey is too high at low temperatures. It was concluded that flounder must use several sensory features to detect and capture prey in turbid estuarine waters and that field studies provide important background information on the actual predator preferences under natural conditions.     

The role of connectivity and physicochemical conditions in effective habitat of two exploited penaeid species

The value of estuarine habitats is often measured by their contribution to the adult component of the population, but a broader suite of attributes can also contribute to nursery function. Identifying and quantifying these elements allows habitat repair to be effectively targeted toward improving ecosystem function for desirable species. We present a study that incorporates stable isotopes and quantitative sampling to investigate the relative importance of different estuarine areas for juveniles of exploited prawn species within the context of habitat rehabilitation, and the potential drivers of these relationships. Eastern King Prawn (Penaeus [Melicertus] plebejus) and School Prawn (Metapenaeus macleayi) were studied for two years in the lower Hunter River estuary, on the temperate east coast of Australia. The higher salinity areas near the lower end of the estuary were most important for Eastern King Prawn, and marsh systems in the lower estuary were only important for the species where there was good connectivity with oceanic water. Areas along the estuary were important for juvenile School Prawn, especially marsh habitats, and relative abundance tended to increase with increasing distance along the estuary. Designation of effective juvenile habitat for School Prawn may have been affected by high fishing mortality in fished areas, but this requires further investigation. Salinity, depth, turbidity and distance along the estuary were all important indicators of prawn distribution. The implications of these patterns for current and future habitat rehabilitation in temperate Australia are discussed.     

River flow,zooplankton and dominant zooplanktivorous fish dynamics in a warm‐temperate South African estuary

The possible links between river flow, zooplankton abundance and the responses of zooplanktivorous fishes to physico‐chemical and food resource changes are assessed. To this end, the seasonal abundance, distribution and diet of the estuarine round‐herring Gilchristella aestuaria and Cape silverside Atherina breviceps were studied in the Kariega Estuary. Spatio‐temporal differences were determined for selected physico‐chemical variables, zooplankton abundance and zooplanktivorous fish abundance and distribution. Results indicated that, following a river flood event in winter (>30 m³ s^?1), altered physico‐chemical conditions occurred throughout the estuary and depressed zooplankton stocks. Abundance of G. aestuaria was highest in spring, with this species dominant in the upper and middle zones of the estuary, while A. breviceps was dominant in summer and preferred the middle and lower zones. The catch per unit of effort of both zooplanktivores also declined significantly following the flooding, thus suggesting that these fishes are reliant on zooplankton as a primary food source for healthy populations. Copepods dominated the stomach contents of both fish species, indicating a potential for strong interspecific competition for food, particularly in the middle reaches. Temporal differences were evident in dietary overlap between the two zooplanktivorous fish species and were correlated with river flow, zooplankton availability and fish distribution. The findings of this study emphasize the close trophic linkages between zooplankton and zooplanktivorous fishes under changing estuarine environmental conditions, particularly river flow and provide important baseline information for similar studies elsewhere in South Africa and the rest of the world.     

Structure,growth and production of a remarkably abundant population of the common goby,Pomatoschistus microps (Actinopterygii: Gobiidae)

The common goby, Pomatoschistus microps, is a relevant species from estuarine food webs, playing important roles as predator of polychaetes and crustaceans and as prey for larger fishes and crustaceans. The Minho estuary (NW Portugal) is a relatively well-preserved and productive system. To assess the population structure and production of P. microps in this estuary, monthly samples were undertaken in three different areas along an estuarine gradient in the lower estuary. The density of P. microps varied considerably among seasons and sampling stations, with higher densities occurring in summer and autumn. The lowest densities were found closer to the sea. In general, the density of females was higher than the density of males in all sampling stations, while juveniles were more abundant within a salt marsh area. Compared with other European estuaries, our data showed a remarkable higher density and production values of P. microps. This may be related to the high freshwater input and the low salinities found in this estuary. In addition, we hypothesize that the lower density of the sympatric species P. minutus and the high availability of bivalve shells observed in the Minho estuary may have also contributed to the present results, once P. minutus and P. microps often display a diet overlap and the bivalve shells are crucial for the common goby reproduction.     

Effects of intrapopulation phenotypic traits of invasive crayfish on leaf litter processing

Environmental gradients and competition influence aquatic macrophyte distribution in estuaries. The competition-to-stress hypothesis states that some species are excluded from lower estuaries (high salinity) due to abiotic stress and others from upper estuaries (low salinity) by competition. The growth of Crinum americanum L. and Spartina alterniflora Loisel. in monoculture (10:0/0:10) and mixed culture (5:5) under different salinity levels (4/12/26) was analysed by a laboratory experiment (3 cultures × 3 sediment types × 3 replicate) to understand the role of competition and salinity on the distribution of these species in a tropical estuary as well as to verify whether the competition-to-stress hypothesis explains their zonation. We tested the hypothesis that S. alterniflora is not established in the upper estuary due to the effect of competition with C. americanum, whereas the latter presents restrictions to high salinity and has greater competitive ability in the upper estuary. Our data confirm the competition-to-stress hypothesis but not as proposed originally. We conclude that abiotic stress (low nutrient availability) is responsible for the absence of S. alterniflora in the upper estuary and that the competition between the two species is responsible for the absence of C. americanum in the lower estuary.     

The influence of tidal cycles and freshwater inflow on the distribution and movement of an estuarine resident fish Acanthopagrus butcheri

Movement patterns and habitat utilization by black bream Acanthopagrus butcheri (Sparidae), an estuarine resident species, were investigated using acoustic telemetry in a small estuary on the east coast of Tasmania, Australia. Thirty‐four adult A. butcheri were tracked for periods of up to 187 days between August 2005 and January 2006. Although able to tolerate a wide range of salinities, the fish spent most of the time within the upper and middle regions of the estuary, where brackish conditions dominated. The species exhibited extensive movements linked to tidal cycles, with small‐scale upstream movements during incoming tides and downstream movements during out going tides. The extent of these movements was positively correlated with the tidal height difference between consecutive tidal peaks and troughs. Freshwater inflows and resultant changes in salinity also significantly influenced distribution and movement patterns. Fish moved downstream during the periods of heavy inflows, returning upstream as salinities increased to c. >10. During the peak of spawning period (November to December) fish moved into the upper region of the estuary, where they aggregated to spawn. Periodic increases in freshwater discharge, however, resulted in fish leaving the spawning grounds and moving downstream. Towards the end of the spawning season (January), the fish became more dispersed throughout the entire estuarine system.     

Strategies of resource partitioning between two sympatric puffer fishes in a tropical hypersaline estuary,Brazil

The strategies of food partitioning among two abundant estuarine puffer fishes, Sphoeroides greeleyi (Gilbert, 1900) and Sphoeroides testudineus (Linnaeus, 1758), were investigated in a tropical hypersaline estuary. We examined the stomachs of 946 fishes collected with a beach seine across three zones (upper, middle and lower estuary) along with a salinity gradient. The highest abundances of species were recorded in the upper and middle estuary. The diet was comprised mostly by benthic organisms, mainly Bivalvia, Gastropoda, and Brachyura. However, in a hypersaline estuary, these species develop strategies of resource partitioning in three ways: 1) asymmetry effects; 2) habitat selection; and 3) trade-offs among age classes. Diet variations according to fish age classes indicated that the largest individuals showed a decrease in their consumption of small preys (Amphipods, Copepods, and Ceratopogonidae) and an increase in their consumption of larger preys (Bivalvia and Decapoda). This behavior of switching diet towards larger prey was related to the functional trade-offs in swimming capacity, and feeding mode used to capture prey. The middle and upper estuary are important feeding grounds for puffer fishes, as demonstrated by their influence on prey distributions and habitat type. Diet breadth indicated that S. greeleyi tended to be a generalist, whereas S. testudineus tended to be a specialist. Thus, the strategies of partitioning seem to have importance for puffer fish populations in this hypersaline environment.     

Emsian (Lower Devonian) conodonts from the Daliantang Formation at Daliantang,southeastern Yunnan,China

The lower/upper Emsian boundary witnessed prominent diversification of biostratigraphically important genera Polygnathus Hinde, Caudicriodus Bultynck, and Latericriodus Müller. In contrast, conodonts previously reported around this boundary from the South China Block were characterized by relatively low species or subspecies diversity, and only a few widely distributed and extensively studied zone-defining taxa were recorded. In this paper, conodonts from the Daliantang Formation at the Daliantang section (Guangnan, southeastern Yunnan), one of the representative sections of the transitional facies between the benthic Xiangzhou facies and the pelagic Nandan facies, are investigated. The conodont fauna shows a remarkably high species or subspecies diversity, with fourteen taxa that are assignable to the notoperbonus Zone and inversus Zone. Five polygnathid species are described: P. gronbergi Klapper and Jonson, P. inversus Klapper and Jonson, Polygnathus sp. B, P. luciae Martínez-Pérez and Valenzuela-Ríos, and P. mashkovae Bardashev. The latter two are reported for the first time from the South China Block. Additionally, three icriodontid taxa are also described, of which L. guangnanensis n. sp. is characterized by distinctly chevron-shaped transverse rows in the anterior part and a well-developed process branching off to the outer side. The new conodont record increases our understanding of the diversification and faunal composition around the lower/upper Emsian boundary in the South China Block. It contributes to the regional and inter-regional biostratigraphical correlation between shallower- and deeper-water facies and also furnishes important South China material for future discussion and deliberation on the position of the lower/upper Emsian boundary.     

Foraminifera in the diet of coral reef fish from the lagoon of New Caledonia: Predation, digestion, dispersion

Marine benthic Foraminifera are abundant and thus represent a potential food source for fish. Previous studies of Foraminifera in fish diets have examined only small samples, with significant input reported only for a single surface-feeding species of fish. The present study is the first based on a significant sample (247 fish belonging to 83 species, 291 species of Foraminifera identified from more than 20,000 specimens examined). It provides new information on the contribution of Foraminifera to fish diets, and on the impact of fish predation on Foraminifera. The planktonic Tretomphalus phases, selectively ingested by Pomacentrus amboinensis, were the only significant nutritional input from Foraminifera. Herbivorous fish accidentally ingested living epiphytic Foraminifera, which were still living after digestion, and were defecated, with a significant effect on their dispersion. Carnivorous fish ingested a small number of tests, which were generally altered by the acidic phase of digestion and had no impact on foraminiferal assemblages. Sediment feeders ingested large quantities of empty tests that were released elsewhere, suggesting a possible bias in paleontological interpretations by mixing the thanatocoenoses. Observations on gut contents showed that the fish sometimes fed on a wide range of food, changing with food availability and individual preferences of fish.     

Distribution patterns of the fish assemblage in the Mamanguape River Estuary,North-eastern Brazil

The Mamanguape River Estuary was studied along a continuum ranging from shallow sandstone reefs adjacent to the river mouth up to the limit of influence of seawater, the upper portions of the estuary. Fish samples were gathered using three types of nets along 17 sample sites, grouped in four regions according to salinity range (reefs and low, middle and upper estuaries), to seasonality (dry and rainy seasons) and to habitat usage (marine visitor, marine estuarine-opportunist, marine estuarine-dependent, estuarine resident and estuarine &; marine). Differences were found in the fish assemblages along the estuarine-reef gradient, with most species (n?=?30) being considered marine, estuarine-opportunists or estuarine-dependent, according to its abundance and distribution. A low number of species (n?=?11) were considered estuarine residents. Some species exhibited significant differences in spatial distribution pattern, in which juveniles and adults predominated in different portions of the estuary, suggesting an ontogenetic migration both in relation to the adjacent reef area and across estuarine regions. Several species were newly recorded in the Mamanguape Estuary: Anchoa spinifer, Halichoeres poeyi, Hyporhamphus roberti, Scomberomorus cavalla, Sphyraena barracuda and Ocgocephalus vesperilio.     

A biological trait approach to assess the functional composition of subtidal benthic communities in an estuarine ecosystem

Within transitional/estuarine environments ‘ecosystem functioning’ has been mostly investigated with “traditional” taxonomic analysis, based on the taxonomic composition of benthic invertebrate communities. However, ‘ecosystem functioning’ depends also greatly on the functional characteristics (biological traits) of organisms.It was a priori suggested that the biological traits of the subtidal benthic invertebrate communities within an estuarine environment would respond to the high variability of environmental pressures (natural and human induced) within this type of ecosystem.For this study, traditional taxonomic analysis (species richness, species density and Shannon–Wiener diversity) as well as biological trait analysis were used together for the first time to investigate the response of the subtidal benthic invertebrate communities to the environmental pressures within the Mondego estuary (Portugal).Biological trait analysis, in addition to traditional taxonomic analysis provided a more comprehensive understanding of the functioning within this type of ecosystem. Some of the most important outcomes are: (i) the trait “salinity preference” was the most important trait that distributed the species along the estuary, (ii) the central part of the estuary appeared to be under higher environmental stress levels than the other areas, as suggested by a dominance of some “opportunistic” traits (e.g. small short-lived species), (iii) the ratio between functional diversity (FD) and Shannon–Wiener diversity (H′) indicated lower functional redundancy at the upper reaches of the estuary. Our results, suggest that the ratio (FD/H′) might be a helpful tool to visualize this functional attribute and could potentially be applied to different communities from distinct environments. Using the traditional taxonomic analysis alone, this last functional aspect would not be detectable. Therefore, the inclusion of biological traits analysis is recommendable for estuarine ecological studies.