Seasonal Variation In Abundance Research Articles

Population biology of shrimp Artemesia longinaris (Crustacea: Decapoda: Penaeidae) from the southern coast of Brazil

Size at morphological sexual maturity, sex-ratio, and the seasonal variation in abundance of the shrimp Artemesia longinaris Bate, 1888 were assessed off Pinheira Beach, Palhoça, Santa Catarina southern Brazil. Shrimp were collected monthly from November 2003 through to October 2004, in two areas that are customarily used by local traditional fishermen (27°52′–27°51′S and 48°33′–48°29′W). Of the total of 1099 specimens measured, 23.93% were males and 76.07% females. Mean size at first maturity (LM50) was estimated as 56.38 mm total length (TL) for males, and 70.34 mm TL for females. Females were significantly larger than males. Abundance of juveniles varied seasonally. A high predominance of juveniles in the areas sampled occurred in winter for both sexes, and in spring for females. In the summer and autumn, we observed a decrease in juveniles in both areas, mainly, area II. We suggest that the differential migration pattern of sexes during the reproductive cycle was the principal reason for the larger catch of females. The classical paradigm of continuous reproduction at lower latitude, with increased seasonality of the breeding period at higher latitudes, seems to apply to this species.

Oilfield Development and Glaucous Gull (Larus hyperboreus) Distribution and Abundance in Central Alaskan Beaufort Sea Lagoons, 1970–2001

We evaluated aerial survey data for glaucous gulls ( Larus hyperboreus ) in central Alaskan Beaufort Sea lagoons near the Prudhoe Bay oilfields during June to September 1978– 2001 for trends in numbers of glaucous gulls, associations with human activity, and confounding relationships with environmental variables. Most glaucous gulls were in barrier island and mainland shoreline habitats, and the total number of gulls per survey ranged from 50 to 1600. Seasonal variation in abundance was apparent, with the largest numbers of gulls consistently recorded during September surveys. Ice cover and wave height had a significant negative correlation with the linear density of glaucous gulls (gulls/km). There was no clear trend in abundance of gulls in the lagoons at Prudhoe Bay or obvious interaction with human activity (such as air traffic, boat traffic, or humans on land or water) in the survey area during the period of oilfield development (1978–2001). We compiled glaucous gull nest counts from 1970 to 2001 across barrier islands to evaluate trends in the number of nests and associations with other colonial nesting species. The mean number of active glaucous gull nests increased from 1970–74 (77.6 nests per year) to 1975–85 (154.4 nests per year), but there was no evidence of a difference from 1970–74 to 1987– 2001 (153.0 nests per year). However, the change in 1976 from aerial to ground-based nest surveys confounds comparison of the survey periods before this date (1970– 74) with those after it (1975–85 and 1987– 2001). A strong positive relationship between the number of glaucous gull nests and both common eider and snow goose nests suggests that common environmental variables may be regulating nesting for these species.

Seasonal variation in hyperiid amphipod abundance and diversity and influence of mesoscale structures off Baja California

Hyperiid amphipods collected during 4 IMECOCAL (Spanish acronym for Mexican Investigations of the California Current) cruises in January, April, July, and October 2005 were ana- lyzed for seasonal variation in abundance and diversity and to determine the influence of surface cir- culation. The number of species was high in all seasons (between 79 and 92), but abundances showed remarkable differences. The total number of amphipods was lowest in January and highest in October (geometric means were 82 and 606 ind. 1000 m -3 respectively). Multivariate analysis based on similar- ity indices demonstrated a tight coupling between species composition and mesoscale structures. The largest cluster joined 67 stations, with 40% of similarity being explained by 4 species (Vibilia armata, Lestrigonus schizogeneios, Eupronoe minuta, and Primno brevidens). The geographic position of these stations coincided with the main California Current (CC) flow from spring to autumn. Subgroups were defined by minor seasonal differences. In contrast, the CC flow during winter was reduced to a meander off north Baja California, and was surrounded by oligotrophic water as indicated by the pres- ence of the hyperiids Anchylomera blossevillei and Phrosina semilunata plus 3 of the dominant species (V. armata, E. minuta, and P. brevidens). To the south of this front, other clusters with high oceanic influence were formed. In 2005, 3 eddies were detected in the area: one anticyclonic eddy in April and 2 cyclonic eddies in July. The anticyclonic eddy located in the southwest had its own faunal cluster that had high diversity but low population density. The main species in the anticyclonic eddy was Platyscelus ovoides. Only one of the cyclonic eddies had a unique faunal identity, being strongly dom- inated by Vibilia armata; this was located in the north between the CC flow and the coast. The other eddy was large and situated in the middle of the area, with a faunal array analogous to that in the CC flow. Correlation between hyperiid and salp species abundances suggested that the increase in salps (Salpa fusiformis, Thalia orientalis, Cyclosalpa bakeri) in spring could be relevant, as many hyperiid species showed a strong increase at this time. However, the most correlated salp was Cyclosalpa danae, which occurred only in October. Chains of C. danae aggregates were firmly attached in the samples. This would promote the aggregation and survival of amphipod hosts, particularly small spe- cies such as Lestrigonus schizogenios and L. bengalensis.

Seasonal variations of Aulacoseira granulata population abundance in the Pearl River Estuary

Seasonal variations of the abundance of Aulacoseira granulata populations were studied in the Pearl River Estuary from August 2007 to May 2009. The average abundance of A. granulata reached 134.14 × 10 3 cells dm − 3 (10.66 × 10 3 filaments dm − 3), contributing 9.1% to the total phytoplankton. Compared with freshwater areas, A. granulata abundance in the Pearl River Estuary was one or more orders lower. Among the four variant forms of A. granulata, the dominance sequence was A. granulata var. granulata > var. angustissima > var. curvata > var. angustissima f. spiralis. The dominance of A. granulata var. granulata and A.g. var. angustissima benefited from their linear shape. A. granulata abundance was higher in the warm seasons and lower in the cold seasons. The fluctuations of Si concentrations could also influence contrasting results as in May 2008 and May 2009. The spatial distribution of A. granulata was mainly influenced by the water runoff of the Pearl River at different outflow channel. We found that the relative abundance of var. angustissima to A. granulata var. granulata was much higher in winter than in other seasons, which maybe because high cell surface/volume area (A/V) benefited var. angustissima by ensuring more effective uptake of nutrients and CO 2 and a slower sinking velocity than var. granulata.

Striking a balance between retaining populations of protected seahorses and maintaining swimming nets

Abstract The fish family Syngnathidae (seahorses, pipefish, pipehorses and seadragons) is fully protected in New South Wales, Australia, but in some countries certain species are threatened by unsustainable collecting, capture as incidental bycatch, and habitat degradation. Within Sydney Harbour, two species of seahorses (Hippocampus abdominalis and Hippocampus whitei) have been found to colonize artificial structures such as jetty pylons and protective netted swimming enclosures. These protective nets are subject to fouling from epibiotic growth (algae, ascidians, bryozoans, etc.) and rubbish, which causes the nets to collapse from the additional weight. Local authorities employ diving contractors on an ad hoc basis to remove the epibiota from nets. Surveys showed a significant decline in the numbers of both seahorse species at one site following the replacement of a net, and recovery of the H. whitei population took more than 15 months. A manipulative experiment tested the importance of epibiotic growth for seahorses. H. whitei, tagged with individual marks, were allocated to sections of a net that had undergone different cleaning procedures. Seahorse size, position on the net and total population abundance were recorded every 2 weeks over a 3 month period. It was demonstrated that seahorses have a significant positive association with epibiotic growth and proximity to the sea floor. Seahorse populations also showed seasonal variation in abundance with increased numbers on the net during the breeding season (spring–summer). This project has led to the development of best practice net cleaning procedures for local authorities in Sydney Harbour to manage growth on the nets while minimizing impacts on seahorse populations. Copyright © 2009 John Wiley & Sons, Ltd.

Diurnal Abundance, Foraging Behavior and Habitat Use by Non-Breeding Marbled Godwits and Willets at Guerrero Negro, Baja California Sur, México

Seasonal variation in abundance, time activity budgets and foraging behavior of non-breeding Marbled Godwits (Limosa fedoa) and Willets (Tringa semipalmata) were compared at four sites at the Laguna Ojo de Liebre—Guerrero Negro saltworks complex, Baja California, Mexico. Habitat use varied between species, seasons and sites. Marbled Godwits (182 ± 44.1 individuals per site) were more abundant than Willets (70 ± 16.1 individuals per site), reflecting their overall pattern in northwestern Mexico. Overall abundance diminished throughout the season (270 ± 69 individuals per site in Oct–Nov, 85 ± 21 in Dec–Jan and 60.2 ± 24 in Feb–Mar), although it remained high at mudflat. Consistent with bill length, Willets foraged mostly by pecking, while Marbled Godwits did so mostly by probing (proportion of pecks: 0.95 ± 0.17 and 0.4 ± 0.27, respectively). Marbled Godwits changed their time activity budgets through the wintering season: time devoted to vigilance changed from 8–23% in Oct–Nov, to 0.4–8% in Feb–Mar whereas time devoted to feeding changed from 12–40% in Oct–Nov to 59–74% in Feb–Mar. This pattern seems to reflect a change in priorities; surviving early in the season and accumulating energy to migrate, later. In both species, differences in use of habitat appeared to be related to site characteristics such as substrate hardness and risk of predation. The mudflat was the site most used and the saltmarsh, the least used. Some individuals in both species used the more risky saltmarsh, but increased the time devoted to vigilance. Thus, habitat quality for non-breeding shorebirds depended on both benefits and costs for foraging birds, and habitat choice by specific individuals was complex and probably involved condition- or state-dependent tradeoffs that balanced metabolic requirements, safety priorities, and, perhaps, social status or dominance.

Seasonality of litter insects and relationship with rainfall in a wet evergreen forest in South Western Ghats.

The seasonality of litter insect abundance and its relationship with rainfall was analyzed in a wet evergreen forest on the windward side of south Western Ghats. Monthly litter samples were collected using Berlese funnels during 4 seasons of a year: southwest monsoon season June—August), northeast monsoon season (September—November), summer (March -May) and pre-summer season (December—February). Insect fauna as a whole showed no seasonal variation in abundance, however, some individual insect orders showed significant seasonal variation. Overall insect fauna and individual orders were distributed independently relative to rainfall. All insect orders with the exception of Psocoptera were present during all four seasons. Coleoptera (42%) was the dominant group in all seasons followed by Formicidae (12.3%), insect larvae (10.1%), Collembola (9.2%) and Thysanoptera (8.9%). Exceptionally high abundance of Ptiliidae contributed to the unprecedented abundance of litter Coleoptera. The aseasonality of litter insect fauna as a whole is attributed to year-round availability of rainfall and the absence of severe summer conditions.

Abundance and diversity of snow bacteria in two glaciers at the Tibetan Plateau

Snow bacterial abundance and diversity at the Guoqu Glacier and the East Rongbuk Glacier located in the central and southern Tibetan Plateau were investigated using a 16S rRNA gene clone library and flow cytometry approach. Bacterial abundance was observed to show seasonal variation, with different patterns, at the two glaciers. High bacterial abundance occurs during the monsoon season at the East Rongbuk Glacier and during the non-monsoon season at the Guoqu Glacier. Seasonal variation in abundance is caused by the snow bacterial growth at the East Rongbuk Glacier, but by bacterial input from the dust at the Guoqu Glacier. Under the influence of various atmospheric circulations and temperature, bacterial diversity varies seasonally at different degrees. Seasonal variation in bacterial diversity is more distinct at the Guoqu Glacier than at the East Rongbuk Glacier. Bacterial diversity at the two glaciers exhibits different responses to various environmental conditions. More bacteria at the Guoqu Glacier are connected with those from a soil environment, while more bacteria affiliated with a marine environment occur at the East Rongbuk Glacier.

Seasonal variations in abundance and biomass of picoplankton in an oyster-farming area of northern Japan

We investigated seasonal variations in abundance and cell volume of picoplankton (heterotrophic bacteria and phycoerythrin-rich cyanobacteria) along with environmental conditions at a coastal site in an oyster-farming area in northern Japan. Samples were collected once or twice a month from July 2002 to July 2004 and analyzed using epifluorescence microscope methods. Abundances of bacteria and cyanobacteria both increased from summer (June–August) to autumn (September–November) and decreased from winter (December–February) to spring (March–May). The range of seasonal abundances of bacteria was within one order of magnitude, but that of cyanobacteria extended over almost three orders of magnitude. Bacterial and cyanobacterial abundances were both positively correlated with temperature. However, the abundance of cyanobacteria decreased at high temperatures when salinity was below 31 psu. Cell volumes of bacteria and cyanobacteria varied inversely with seasonal patterns of abundance. Cell volumes of cyanobacteria were negatively correlated with temperature, whereas those of bacteria showed no significant correlation with temperature. Mean water-column carbon biomass ranged from 23.4 to 174.3 μg-C L−1 for bacteria and from 0.1 to 18.4 μg-C L−1 for cyanobacteria. Maximum values of mean water-column biomass of bacteria reached 179% of the estimated biomass of phytoplankton carbon, whereas that of cyanobacteria was 58% of picophytoplankton biomass and 22% of phytoplankton biomass. Bacterial biomass levels similar to those of phytoplankton and the high contribution of cyanobacteria to picophytoplankton in summer imply that the picoplankton assemblage plays an essential role in planktonic food webs in the bivalve-farming area.

Distribution of biologically functional habitats within a lowland river, United Kingdom

The assessment and appraisal of river habitat quality for purposes of legislative compliance requires a sound understanding of the interactions between the hydrogeomorphological and ecological components of the instream environment. Reconciliation of complementary habitat concepts developed from geomorphology (‘physical biotopes’) and from ecology (biologically ‘functional’ habitats) offers improved integrity of both concepts, but may be limited by factors such as the distributional characteristics of functional habitats. Field surveys conducted on a lowland river in Shropshire, UK, reveal differences in both the spatial organisation and seasonal variations in abundance among functional habitat categories. Furthermore, the level of human modification to the channel and banks appears to influence the spatial organisation of certain functional habitats within the river channel. These factors have implications for rapid field survey methods and for the potential for linking functional habitats with the complementary geomorphological concept of physical biotopes.

Habitat effects on invertebrate drift in a small trout stream: implications for prey availability to drift-feeding fish

In this study, we focused on the drivers of micro- and mesohabitat variation of drift in a small trout stream with the goal of understanding the factors that influence the abundance of prey for drift-feeding fish. We hypothesized that there would be a positive relationship between velocity and drift abundance (biomass concentration, mg/m3) across multiple spatial scales, and compared seasonal variation in abundance of drifting terrestrial and aquatic invertebrates in habitats that represent the fundamental constituents of stream channels (pools, glides, runs, and riffles). We also examined how drift abundance varied spatially within the water column. We found no relationship between drift concentration and velocity at the microhabitat scale within individual pools or riffles, suggesting that turbulence and short distances between high- and low-velocity microhabitats minimize changes in drift concentration through settlement in slower velocity microhabitats. There were also minimal differences in summer low-flow drift abundance at the mesohabitat scale, although drift concentration was highest in riffle habitats. Similarly, there was no differentiation of drifting invertebrate community structure among summer samples collected from pools, glides, runs, and riffles. Drift concentration was significantly higher in winter than in summer, and variation in drift within individual mesohabitat types (e.g., pools or riffles) was lower during winter high flows. As expected, summer surface samples also had a significantly higher proportion of terrestrial invertebrates and higher overall biomass than samples collected from within the water column. Our results suggest that turbulence and the short length of different habitat types in small streams tend to homogenize drift concentration, and that spatial variation in drift concentrations may be affected as much by fish predation as by entrainment rates from the benthos.

Seasonal variability in bacterial abundance, production and protistan bacterivory in the lower Urdaibai estuary, Bay of Biscay

Seasonal variations in abundance of heterotrophic bacteria, small (1-8 µm) heterotro- phic nanoflagellates (HNF), and ciliates, as well as bacterial production (BP) and bacterivory (PB) rates were investigated from May 1998 to May 1999 in the lower Urdaibai estuary (Bay of Biscay). Abundances ranged from 2.6 × 10 8 to 1.3 × 10 9 cells l -1 , 0.65 × 10 6 to 3.00 × 10 6 cells l -1 , and 12 to 436 cells l -1 for bacteria, HNF and ciliates, respectively. BP varied between 0.9 and 18.5 × 10 8 cells l -1 d -1 . Bacteria seemed to be more limited by food supply than by temperature. The major bacterivores were small HNF, but they could not satisfy their carbon demand only through bacterivory. Bacterivory rate per small HNF varied between 2.7 and 28.2 bacteria flagellate -1 h -1 . This rate showed seasonal vari- ations and was higher during late winter/early spring than during summer/early autumn. This pat- tern is probably due to the greater dependence of small HNF on bacteria during late winter/early spring, when the availability of food sources other than bacteria, e.g. autotrophic picoplankton, was low. This led to seasonal variations in the degree of grazing control on the bacterial standing stock, this control being tighter during late winter/early spring. Bacterivory rate was substantially higher than BP in many months, i.e. bacteria showed a negative growth, and this was paralleled by reduc- tion in bacterial abundance. The relationship between log bacterial abundance and log small HNF abundance suggested that small HNF were largely under a substrate supply (bottom-up) control.

A baseline biological survey of the proposed Taputeranga Marine Reserve (Wellington, New Zealand): spatial and temporal variability along a natural environmental gradient

Abstract Four macroalgal, four macroinvertebrate and eight fish species were surveyed at eight sites (three inside, five outside the proposed reserve) over three years before the establishment of the Taputeranga Marine Reserve (MR) on Cook Strait (Wellington, New Zealand). This baseline data set was used to estimate temporal and spatial variability in size and abundance of these taxa, and will be used to quantify taxon‐specific changes in size and abundance once the MR is established. Statistically significant differences in size and/or abundance were observed for many taxa among the sites. These differences are consistent with the existence of a natural environmental gradient from the west (entrance to Cook Strait) to the east (Wellington Harbour). This gradient highlights the importance of conducting a pre‐reserve baseline survey at multiple sites and over multiple years to better understand the conservation or fisheries benefits that MRs are expected to deliver. Two macroalgal, one macroinvertebrate, and six fish species showed statistically significant seasonal variation in abundance. Subsequent multi‐taxa monitoring needs to include a seasonal component to capture this natural variability. This multi‐site and multi‐year data set represents one of the most comprehensive and robust baseline data sets available anywhere in the world. It will be used to quantify the ecological changes associated with a newly established full no‐take marine reserve. Ongoing monitoring will enhance understanding of the sizes and abundances of key taxa, allow a detailed determination of the conservation effects of reserve establishment, and inform management decisions for Wellington's south coast. Copyright © 2008 John Wiley & Sons, Ltd.

Seasonal variation in abundance and feeding rates of the first stages of copepods in a temperate sea

An understanding of the role of copepod populations in marine ecosystems and carbon fluxes is limited by the scarcity of information on small copepods and developmental stages (nauplii and copepodites). Here, we present a study that includes the whole copepod population in the Cantabrian Sea, with special emphasis on copepodites and copepods <200 µm and nauplii. Total copepod abundance and feeding rates of phytoplankton by nauplii, copepods and copepodites belonging to the size fraction < 200 µm were measured during an annual cycle in 3 stations off Cud- illero (southern Bay of Biscay). Nauplii were the most abundant group in the metazooplankton, with densities ranging between 1 and 48 ind. l -1 . The highest abundances were found during late summer and autumn. Feeding rates on phytoplankton showed a significant increase with chlorophyll a con- centration in the water, and a saturation response at around 240 µg C l -1 . Specific ingestion rates ranged from 0.04 to 2.05 µg C µg -1 nauplii C d -1 and 0.04 to 3.38 µg C µg -1 copepod C d -1 . Nauplii and copepods < 200 µm, respectively, ingested 0.2 to 7.1% and 0.1 to 4.9% of total chlorophyll a in the water column daily.

The parasitoid complex ofParthenolecanium corniBouché in the city of Tbilisi and its surroundings and comparison with some other European countries

The European fruit lecanium (EFL), Parthenolecanium corni Bouché (Hemiptera: Coccoidea), is a common and harmful soft scale, which attacks Fraxinus oxycarpa Willd. and other ornamental and orchard plants in Tbilisi, Georgia. This study investigates the phenology, degree of plant damage and effect of parasitoids on this scale in Tbilisi, a densely populated area. We present data on the 32 species of chalcidoid parasitoids recorded from EFL in Georgia and south-eastern Europe. The scale is heavily parasitized in Tbilisi, but we did not find any variation in seasonal abundance. The most common parasitoid of EFL was Blastothrix longipennis (Hymenoptera: Encyrtidae).

여자만 저층트롤 어획실태와 종조성

Fishes were caught by a bottom trawl in the Yeo-ja bay of Korea by every three month(March, June, September and December) and seasonal variation of abundance and species composition were studied in 2005. The catches were 1,187kg and were composed of 115 species with 20 hauls by 5 stations. The dominant species caught were Charybdis bimcaulata, Crangon hakodatei, Parapenaeus fissurus, Oratosguilla oratoria, and Thryssa purava. One hundred fifty species were identified as fish(38%), crustacea(20%), mollusca(4%) and others(38%) which including of Asterias amurensis. The amount of species was high in June and September and low in March and December. The diversity index(H`) was about 1.2－2.5 and station similarity of fishes caught among the community was 0.009－0.230.

Thermal constraints on daily patterns of aggregation and density along an intertidal gradient in the periwinkle Echinolittorina peruviana

Variations in environmental temperature have both direct and indirect effects that affect organisms at levels ranging from intra-cellular physiological processes to ecological patterns. These variations are especially important for intertidal marine ectotherms such as littorinids since they alternate between periods of immersion in seawater, and must also experience long periods of emersion. In central Chile, Echinolittorina peruviana is one of the most conspicuous species on rocky intertidal shores, occurring at high tidal levels and in the splash zone. The species is known to resist direct exposure to the sun for long periods, although juveniles tend to be restricted to protected microhabitats. Adults show seasonal variations in abundance and vertical distribution and may form aggregations that have been shown to help reduce water loss and body temperature. In this study, we evaluate the relationship between daily thermal variations throughout the vertical distribution of this species and how these affect the patterns of density and aggregation. Our results suggest that one of the leading determinants of the spatio-temporal variation of density in E. peruviana may be operative temperature ( T O: the amount of stored heat resulting from the balance between heat fluxes into and out of the body, measured with taxidermic mounts mimicking heat transfer properties of the snail). T O showed a strong negative relationship with density and a strong positive relationship with aggregation in the highest intertidal level monitored. The strength of these relationships decreased in importance at lower levels. While T O alone cannot explain the abundance of E. peruviana throughout its range of distribution, our results show that it does have a strong influence that should be considered in addition to other ecological factors affecting the density of intertidal littorinids.

Substrate selection and seasonal variation in abundance and size composition of isopod Lirceus fontinalis in Ontario streams, Canada

The abundance and size composition of stream isopods Lirceus fontinalis were investigated from April 2001 to August 2002 in 3 streams in southern Ontario, Canada. Effects of current speed was released from the analysis by choosing slow flowing water. The effects of substrate, season and water depth on the abundance, distribution and size composition of the isopods were analyzed. It was found that substrate and season influence isopods the most. The rocky substrate with attached filamentous macro-algae contains an isopod abundance 7.05 times that of bare rock substrate and 14.6 times that of fine-sand and mud substrate. There was a large variation with respect to seasonality in both abundance and size composition of the isopods, with the highest abundance occurring in summer and the lowest in winter and spring; individual isopods also tend to be larger in the winter and spring. In all substrates, shallow areas tend to support higher densities of isopods than deeper areas.

Diel and Seasonal Variations in Abundance, Activity, and Community Structure of Particle-Attached and Free-Living Bacteria in NW Mediterranean Sea

Diel and seasonal variations in abundance, activity, and structure of particle-attached vs free-living bacterial communities were investigated in offshore NW Mediterranean Sea (0-1000 m). Attached bacteria were always less abundant and less diverse but generally more active than free-living bacteria. The most important finding of this study was that the activity of attached bacteria showed pronounced diel variations in the upper mixed water column with higher activities at night. Under mesotrophic conditions, the contribution of attached bacteria to total bacterial activity increased from less than 10% at day time to 83% at night time. At high chlorophyll a concentration, the highest cell-specific activities and contribution to total bacterial activity were due to free-living bacteria at day and to attached bacteria at night. Under summer oligotrophic conditions, free-living bacteria dominated and contributed to the most important part of the bacterial activity at both day and night, whereas attached bacteria were much less abundant but presented the highest cell-specific activities. These diel and seasonal variations in activities were concomitant to changes in bacterial community structure, mainly in the upper layer. The number of attached ribotypes was fairly constant suggesting that particles are colonized by a relatively limited number of ubiquitous ribotypes. Most of these ribotypes were also free-living ribotypes suggesting that attached bacteria probably originate from colonization of newly formed particles by free-living bacteria in the upper layer. These results reinforce the biogeochemical role of attached bacteria in the cycling of particulate organic carbon in the NW Mediterranean Sea and the importance of diel variability in these processes.

Culturable bacteria in Himalayan glacial ice in response to atmospheric circulation

Abstract. Only recently has specific attention been given to culturable bacteria in Tibetan glaciers, but their relation to atmospheric circulation is less understood yet. Here we present the results of culturable bacteria preserved in an ice core drilled from the East Rongbuk (ER) glacier, Himalayas. The average concentrations of culturable bacteria are 5.0, 0.8, 0.1 and 0.7 CFU mL−1 for the glacier ice deposited during the premonsoon, monsoon, postmonsoon and winter seasons, respectively. The high concentration of culturable bacteria in ER glacier deposited during the premonsoon season is attributed to the transportation of continental dust stirred up by the frequent dust storms during spring. This is also confirmed by the spatial distribution of culturable bacteria in Tibetan glaciers. Continental dust originated from the Northwest China accounts for the high abundance of culturable bacteria in the northern Tibetan Plateau, while monsoon moisture exerts great influence on culturable bacteria with low abundance in the southern plateau. The numbers of representatives with different ARDRA patterns from RFLP analysis are 10, 15, 1 and 2 for the glacial ice deposited during the premonsoon, monsoon, postmonsoon and winter seasons, respectively, suggesting that culturable bacteria deposited in ER glacier during monsoon season are more diverse than that deposited during the other seasons, possibly due to their derivation from both marine air masses and local or regional continental sources, while culturable bacteria deposited during the other seasons are from only one possible origin that is transported by westerlies. Our results show the first report of seasonal variations of abundance and species diversity of culturable bacteria recovered from glacial ice in the Himalayas, and we suggest that microorganisms in Himalayan ice might provide a potential new proxy for the reconstruction of atmospheric circulation.