Suspended particulate matter dynamics in the shallow mesotidal urdaibai estuary (Bay of Biscay,Spain)

Seston quantity and quality was measured in the Urdaibai Estuary in summer, when river discharge is low and tidal flushing is the main driving force to transport and resuspend particulate matter in the estuary. The highest seston concentrations are found in the upper estuary, where more than 90% of total suspended particulate matter is made up of particles <20 μm. There is a temporal ebb-flood asymmetry and turbulent mixing is stronger at flood tide. During dry calm periods sediment resuspension is observed for a short period of time at floods during spring tides, decreasing drastically before slack waters. In spite of this, particulate organic matter mainly originates from anthropogenic sources (domestic wastewater discharge) and plankton production.     

莱州湾大型砂壳纤毛虫群落季节变化

为揭示莱州湾砂壳纤毛虫群落季节变化规律, 在莱州湾设置8个站位, 于2011年5-11月及2012年3-4月进行了9个航次的调查, 用浅海III型浮游生物网由底至表垂直拖网采集砂壳纤毛虫。结果表明, 莱州湾3-11月砂壳纤毛虫物种丰富度的变化范围为5-19, 周年变化呈现一峰两谷的趋势。丰度的范围为0-318 ind./L, 丰度较大(> 50 ind./L)的种类有运动类铃虫(Codonellopsis mobilis)和清兰拟铃虫(Tintinnopsis chinglanensis)。各月平均丰度随时间的变化趋势为双峰型, 最大值出现在7月(63 ind./L), 次峰值出现在5月(48 ind./L), 最小值出现在3月(2 ind./L)。黏着壳种类在3-11月均有出现, 透明壳种类仅在温度较高(> 15°C)的6-9月出现。各月的优势种数目为1种(5月)到8种(8月), 其中运动类铃虫在所有月中都是优势种, 对砂壳纤毛虫丰度周年的变化规律产生较大影响。使用各月所有种类的平均丰度对各月砂壳纤毛虫群落进行聚类分析, 得到两个群落(相似度30%): 群落I(7-9月)和群落II(3-6月、10-11月), 说明砂壳纤毛虫群落发生了明显的季节变化。砂壳纤毛虫的物种丰富度、丰度与环境因子(温度、盐度)均没有明显的相关性。     

温州湾天河滩涂大型底栖动物群落分布与季节变化

2003年11月至2004年8月,在温州湾天河潮间带按季节取样对大型底栖动物群落进行了研究.共发现大型底栖动物38种,隶属7门8纲23科,主要为软体动物、节肢动物和环节动物多毛类.物种获得数季节间差异不显著(F3,9=1.76,P＞0.05),但潮位间种类获得数差异极显著(F3,9=9.56,P＜0.01).潮上带、高潮带、中潮带和低潮带的密度、生物量分别为:144.50±14.24 ind./m2,58.56±13.23 g/m2;171.00±16.52ind./m2,40.57±12.60 g/m2;182.50±39.38 ind./m2,50.26±10.57 g/m2和94.00±28.88 ind./m2,16.55±7.27 g/m2.密度的季节间差异和潮位差异均不显著(F3,9=2.78和F3,9=2.14,P＞0.05),而生物量在季节和潮位间差异极显著(F3,9=16.72和F3,9=22.24,P＜0.01).Margalef物种丰富度指数和Shannon-Weiner多样性指数4季平均数表现为:中潮带＞高潮带＞低潮带＞潮上带;Pielou均匀度指数平均数表现为:低潮带＞中潮带＞高潮带＞潮上带;Simpson优势度指数平均数表现为:中潮带＜高潮带＜低潮带＜潮上带.对4季4潮带16个群落进行聚类和排序分析可以看出,中高潮带界限不明显,低潮带和潮上带的界限明显.分析表明:生境条件的不同是大型底栖动物群落组成差异的主要原因,同一站位大型底栖动物群落物种构成数各季节之间差异不显著[动物学报52(1):45-52,2006].     

Changes in the Georgian Bay fish community,with special reference to lake trout (Salvelinus namaycush) rehabilitation

We describe and explain some of the changes in the fish community as reflected by the catches of the commercial fishery, and evaluate the efforts to restore the trout (Salvelinus spp.) in Georgian Bay. The changes in the fish community were caused in part by excessive fishing for lake trout (S. namaycush), lake whitefish (Coregonus clupeaformis) and deepwater ciscoes (Coregonus spp.), and the introduction of new species such as sea lamprey (Petromyzon marinus), alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax) and salmonids (Oncorhynchus spp.). The most striking changes were the near extinction of the lake trout, reductions in lake herring (Coregonus artedii), deepwater ciscoes and lake whitefish, and the increase in abundance of smelt and alewife. In an effort to replace the loss of yield from the cold-water habitat, a fast growing and early maturing hybrid trout (splake [S. namaycush × S. fontinalis]) and its backcross to lake trout were selectively bred for stocking in Georgian Bay. Splake did poorly because of low survival immediately after planting. The survival of backcross after planting was better, but adult mortality was still high. Adult survival of backcross improved considerably after restrictions were placed on the commercial fishery in 1984. The first naturally produced backcross larvae were collected in 1985.     

Recent increase of filamentous algae in shallow Swedish bays: Effects on the community structure of epibenthic fauna and fish

A summary is presented of estimates of distribution and growth of filamentous algae and its effect on the structure and functioning of epibenthic fauna and fish communities in shallow bays on the Swedish west coast. As a consequence of coastal eutrophication vegetation cover has gradually increased during the last decade, and during 1990's most bays in the Skagerrak-Kattegat area were variously covered with filamentous algae during spring and summer (May–July). In some areas filamentous algae (mainlyCladophora andEnteromorpha) completely covered the bottom. In field studies it was demonstrated that increased cover and dominance of filamentous algae result in structural changes of the epibenthic fauna community. Field studies showed that species richness and biomass of epibenthic fauna increased in a sandy bay with a moderate increase (30 to 50%) of filamentous algae cover. At higher cover (90%), biomass of epibenthic fauna was reduced, however, to the same level as for the sandy habitat, although the dominant epibenthic species were different. Heavy growth of epiphytic filamentous algae on eelgrass resulted in reduced biomass and a shift in the species composition of the epibenthic fauna community. Fish assemblage structure was also related to changes in vegetation. In eelgrass beds, fish species numbers were reduced with increasing cover of epiphytic filamentous algae, and at rocky bottoms with kelp algae (dominated byFucus), fish biomass decreased with increasing cover of attached filamentous algae. Further, foraging efficiency of juvenile cod and settling success of plaice were reduced as a response to increasing dominance of filamentous algae.     

Diatom bloom in the tidal freshwater zone of a turbid and shallow estuary,Rupert Bay (James Bay,Canada)

Phytoplankton biomass and species composition were studied from June to September 1991 at the mouth of four major rivers and in the freshwater (sal. 0 %), the estuarine (sal. 2–10%) and the coastal (sal. 10–12%) zones of Rupert Bay, located at the southeast tip of James Bay, Canada.A chlorophyll a maximum (5–14 µg 1^–1) was observed in the freshwater zone from July to September. Chlorophyll values were low at the mouth of the rivers and in the estuarine and coastal zones (chl a < 1.00 µg 1^–1). Diatoms were dominant in the freshwater zone (30–80 % abundance), with flagellates dominating in the estuarine and coastal zones (60–95% abundance). Diversity was low (H: 1.5–2.5) in the freshwater zone and decreased seaward (H: 0.5–1.5).The diatom bloom was composed almost exclusively of the autochthonous planktonic diatom Cyclotella meneghiniana Kütz., which contributed 25–85% of the species composition, and of the subdominant benthic species Diploneis smithii, Navicula lanceolata and Surirella robusta. Peak abundance occurred upstream of the turbidity maximum, in the tidal freshwater zone. In this zone the mean photic depth was 1 m and residence time was from 7 to 8 days during the bloom. Residence time is considered to be the dominant factor controlling the phytoplankton bloom, with light not acting as a limiting factor. The high turbidity due to resuspension and shallow depth of the bay controlled the species composition.     

Stephanostomum lophii sp. nov. (Digenea: Acanthocolpidae), intestinal parasite of Lophius piscatorius, with reference to seasonal fluctuations of metacercariae in intermediate second hosts (Gadidae)

We describe the adult and metacercaria of a new species of digenetic trematode, Stephanostomum lophii sp. nov., an intestinal parasite of the angler fish, Lophius piscatorius . The species is distinguished from the similar Stephanostomum kovalevi by the numerous peristomial spines in the latter and from S. baccatum by the oral sucker being larger than the ventral sucker and by the fact that the principal intermediate hosts are gadids, not pleuronectids as in the case of Stephanostomum baccatum . We also report the prevalence of S. lophii metacercariae in various potential angler fish prey species caught off the coast of Galicia (NW Spain).     

Composition,density and feeding of crustacean zooplankton community in a shallow,temperate lake (Lake Balaton,Hungary)

Composition density and filtering rates of crustacean zooplankton were studied in the open water and among the macrophytes of the oligo-mesotrophic part of Lake Balaton from 1981 to 1983. From the individual filtering rates of the different populations and the densities community grazing rates were derived.Copepoda made up 79–90% of crustacean plankton community in the open lake and 95–97% of it in littoral zone. Among them the nauplii dominated. At the end of summer 1982, when Anabaenopsis was in bloom, the filter-feeding species (Eudiaptomus, Daphnia) practically disappeared, being replaced by cyclopoids. Daphnia had the highest filtering rates followed by those of Eudiaptomus and Diaphanosoma. Among copepods, the filtering rates in decreasing order were: ovigerous > all adults > copepodites > nauplii. > . The filtering rates of the different species varied both seasonally as well as from year to year. In 1983, when the concentration of organic seston decreased, filtering rate increased compared with those in the earlier years. During the water bloom in 1982, the rates decreased by 70% on the average.The community grazing rate was very low (3% per day) in the open lake and among macrophytes, both in 1981 and 1982; also the share of crustacean zooplankton in grazing was very low. In 1983, together with the improving of water quality, the community grazing rate increased 4-fold. In 1981 and 1983 the rates were influenced by water temperature but in 1982 by seston concentration.     

Zoobenthos of the Cheshskaya Bay (southeastern Barents Sea): spatial distribution and community structure in relation to environmental factors

Structural and functional characteristics of zoobenthos of the Cheshskaya Bay (SE Barents Sea) were studied at 21 stations in June/July 1995. Strong prevailing cyclonic and tidal currents result in relatively uniform temperature and salinity in the area. Sediments consist mainly of sand and pebbles, while the flux of suspended matter from rivers locally increases the share of finer fractions. Analysis of species composition (419 taxa), abundance (up to 4,200 ind m⁻² and up to 29,000 ind m⁻² with juveniles) and biomass (up to >6,000 g wet wt m⁻²) indicates high species richness in most parts of the bay, especially in the northeast. Analysis of community structure using production characteristics of species revealed a general predominance of suspension feeders partitioned into seven communities. The dominant species of these communities were Mytilus edulis and Balanus crenatus (Type 1), B. crenatus (Type 2), Modiolus modiolus and Verruca stroemia (Type 3), Flustra foliacea and V. stroemia (Type 4), Hydrallmania falcata (Type 5), V. stroemia and Chirona hameri (Type 6), and Ophelia limacina (Type 7). The structure of the communities is mainly regulated by sediment type, water depth and, to some extent, by riverine input. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Homogenisation of water and sediment bacterial communities in a shallow lake (lake Balihe,China)

1. Planktonic and benthic bacterial communities hold central roles in the functioning of freshwater ecosystems and mediate key ecosystem services such as primary production and nutrient remineralisation. Although it is clear that such communities vary in composition both within and between lakes, the environmental factors and processes shaping the diversity and composition of freshwater bacteria are still not fully understood.
2. In order to assess seasonal and spatial variability in lake bacterial communities and identify environmental factors underpinning biogeographical patterns, we performed a large-scale sampling campaign with paired water and sediment sample collection at 18 locations during four seasons in Lake Balihe, a subtropical shallow fish-farming lake in mid-eastern China.
3. Pelagic and benthic bacterial communities were distinctly different in terms of diversity, taxonomic composition and community structure, with Actinobacteria, Bacteroidetes, Cyanobacteria and Alphaproteobacteria dominating lake water, and Acidobacteria, Bacteroidetes, Chloroflexi, Gammaproteobacteria and Deltaproteobacteria dominating sediment. Nevertheless, these two communities had stronger spatial concordance and overlap in taxa during spring and autumn seasons. Together, the main drivers of both the spatial and temporal variations in Lake Balihe bacterial communities were identified as water temperature, turbidity, nitrogen and phosphorus availability, and thermal stratification controlled by wind-mixing and activity of the dense farmed fish populations. Notably, populations affiliated with Firmicutes, known to be abundant in fish gut microbiome, were especially abundant in the summer season and locations where high fish biomass was found, suggesting a potential link between fish gut microbiome and the pelagic bacterial communities.
4. Our findings demonstrated seasonal homogenisation of pelagic and benthic bacterial communities linked to marked shifts in a set of seasonally-driven environmental variables including water temperature and nutrient availability.

     

Seasonal dynamics of phytoplankton and phytobenthos,and associated chemical interactions,in a shallow upland lake (Malham Tarn,northern England)

Seasonal changes of phytoplankton were followed over 3 years (1985–87) in a shallow, unstratified and calcareous upland lake.The phytoplankton was of low to moderate abundance and generally dominated by phytoflagellates. Seasonality involved a winter minimum of abundance, a spring maximum of diatoms, and often brief increases in summer that included blue-greens, especially the colonial Gloeotrichia echinulata. Some components were of benthic origin. Seasonal growth of the main component of the phytobenthos, Chara globularisvar. virgata, caused a regular summer depletion in lake water of Ca²⁺ and HCO₃ ^- (alkalinity) by associated CaCO₃ deposition, and a more extreme (and unusual) depletion of K⁺. Chemical analysis of Chara biomass and of underlying sediments indicated a large benthic nutrient stock, much surpassing that represented by the phytoplankton. Growth in this biomass, and the magnitude of water-borne inputs, influenced the removals of Ca²⁺, K⁺ and inorganic N. The phytoplankton was probably limited by a low-P medium, to which co-precipitation of phosphate with CaCO₃ may have contributed. A vernal depletion of Si was probably limiting to diatom growth, and appeared to be mainly induced by benthic rather than planktonic diatoms. Examples of long-term change in composition of the phytoplankton and phytobenthos are noted and discussed in relation to the interaction of these components, nutrient enrichment, and possible alternative stable states.     

Measurements of import and export in the Krabbenkreek,a tidal area in the Oosterschelde (S.W. Netherlands)

Summary The Krabbenkreek is a tidal area of about 11.5 km², surrounded by dikes for 94%. Mudflats cover nearly 65% of the area and salt marshes cover 15%. The area is connected to the Oosterschelde estuary by a main channel, which allows the tides to reach the inner parts; a small channel draines the mudflats near the mouth directly to the estuary.In a series of 10 measurements the fluxes of material were observed in the two channels by measuring the flow velocities each half hour during two tidal cycles. The water was sampled concurrently. A rough calculation of the data indicated that the resulting masses of soluble and particulate material during a tidal cycle between Krabbenkreek and Oosterschelde are of the same magnitude as the error due to incorrect flow velocity measurements. A more refined calculation is under develoment, which together with checks on the flow measurements will reduce the error.A statistical analysis of the data on the soluble and particulate material gives an indication of the direction of the net flow. In this analysis the chloride is considered a conservative parameter and data of ebb and flood are treated separately. This analysis reveals that ammonia is imported over the year while nitrate is exported. Chlorophyll-a is exported throughout the year as is particulate organic carbon. Silicate is imported throughout the year. There is an import of phosphorus in spring and summer and an export during autumn and winter.     

Some Data on the Composition and Distribution of the Meiofauna in Vostok Bay (Sea of Japan)

The effect of some environmental factors on the composition and spatial distribution of the meiobenthos were studied in Vostok Bay. The spatial density of the meiobenthos significantly positively correlated with ground type and was maximum in fine- grained sands. The eumeiobenthos was dominated by harpacticoids in coarse-grained ground and by nematodes in ground with a high silt content. The pseudomeiobenthos was dominated by polychaetes and bivalve mollusks in all ground types. The depth distribution of the meiobenthos was highly heterogenous, harpacticoids being the only group whose distribution correlated significantly with depth.     

Hydrological cycle and interannual variability of the aquatic community in a temporary saline lake (Fuente de Piedra,Southern Spain)

Fuente de Piedra is a shallow, temporary saline lake whoseseasonal behavior is strongly dependent on the annual hydrologicalbudget. In this study, we outline the characteristics of Fuente dePiedra Lake for two years that had different hydrological budgets.The high precipitations in 1989–90 caused the lake not to dry asusual, and decreased both salinity and the amplitude of changes.There were also differences in nutrient dynamics, with generallylower concentrations of soluble reactive phosphorus and ammonium,whereas in the more humid year nitrate showed a distinct maximum inwinter. Winter bloom chlorophyll a concentrations were alsomuch higher in 1989–90 (>600 g l-1) but there wasalso a winter productive phase that was presumably poorly coupledwith consumption processes that predominate in spring. Planktonicassemblages were different between years. Highly halotolerantphytoplankton species (Dunaliella salina and D. viridis) became scarcer, and especially two previouslyunrecorded diatoms (Cyclotella sp. and Chaetoceros sp.)became dominant in the bloom time in the wet year. The speciesrichness of the zooplankton increased in the wet year, with newspecies appearing that were not collected during 1987–88(Branchinectella media, Daphnia mediterranea, Macrothrix sp.,Arctodiaptomus salinus, Cyclops sp., Sigara sp...).There was also a much higher development of macrophytes (Ruppiadrepanensis, Althenia orientalis, Lamprothamnium papulosum)and bird populations, especially flamingoes (Phoenicopterusruber).Important interannual variations in this sort of system pointto the need for long term studies to observe the whole range ofstates that define the lake as an entity.     

Seasonal Ichthyodiversity and Growth Patterns of Juvenile Flatfish on a Nursery Ground in the Southern Bight of the North Sea (France)

The demersal fish community on a flatfish nursery ground, of the Southern Bight of the North Sea, was sampled monthly between May 1998 and 1999. The studied coastal area is a multispecific nursery area. Although 32 fish species were caught, only nine species had a major influence on the variation in total densities through the year and can be considered as key species. Juvenile sole and plaice exhibited similar seasonal growth patterns with rapid growth during late spring and summer, a growth arrest during autumn and winter and a restart of growth in March. Comparisons of observed growth in length with predicted maximal growth under optimal food conditions suggested that during the summer, growth of 0-group sole and plaice was only determined by prevailing mean water temperature. During autumn and winter, while growth in length of sole followed model predictions, observed length of plaice was less than model predictions, suggesting growth limitation. Analyses of the factors that may be responsible for differences between observed and expected length growth indicated that autumn and winter growth arrest of plaice was not only related to low winter water temperature. It is suggested that for visual feeders such as plaice, the interaction of decreasing food availability and day length during autumn and winter can reduce the access to food resource and therefore feeding success and growth.     

Reproductive ecology and growth of a population of brown trout (Salmo trutta L.) in an aquifer-fed stream of Old Castile (Spain)

In the River Lobos-Ucero and its tributary the River Avión-Milanos (Duero basin, Old Castile, Central Spain), two limestone streams fed by aquifers, the population of brown trout, as compared with the populations of other European streams, shows a high growth rate, high condition coefficients, short life-span and early age at first maturity. Gonad cycle was also studied. Size distributions of unshed eggs exhibit a dynamic activity with a bi-modal distribution from June onwards, spawning occurred in the last days of November. Fecundity (F) can be predicted from trout length (L, mm) according to the equation: F= –646.47+5.6167 · L. Numbers and standing crop of trout range from 18 to 3903 ind. ha^–1 and 3.6 to 452.9 Kg ha^–1, reaching higher values in the sites close to the aquifers. Egg production had values of 22.4 and 18.0 eggs m^–2 in the Rivers Ucero and Avión-Milanos respectively. Some factors suggested as regulators of these demographical characteristics are discussed in the light of recent literature.     

Interaction effects between time and cultivar on the seasonal fluctuations of the safflower fly,Acanthiophilus helianthi (Rossi) (Diptera: Tephritidae) and its parasitoids in the south of Tehran

The safflower fly, Acanthiophilus helianthi is one of the most important pests of safflower in the world that every year puts a lot of loss to the crop. In order to study interaction effect between time and cultivar on seasonal fluctuations and parasitism of the safflower fly on 2012, seven safflower cultivars including Goldasht, Padideh, Zarghan, Varamin, PI, Acataria, Mec163 was cultivated under Completely Randomised Block Design with four replicates in research field of Shahed University research (south of Tehran). Once the prey of adult samples, sampling was started from safflower bolls on weekly basis from late June to late of August. The number of larvae and pupae in each boll were counted separately for each cultivar and recorded in the tables. The highest density of larvae was observed on Goldasht cultivar on 9 July. Aceteria cultivar, on 9 July and Zarghan, Mec163 and PI cultivars on 15 July and Mec163 cultivar was observed the lowest density. The highest density of pupa was observed on cultivar Padideh on 9 July. Also the lowest density of pupa was observed on cultivar PI on 2 July. Goldasht and Aceteria cultivars on 9 July had the highest contaminated bolls, respectively. The lowest density of infested bolls on 25 June was observed on Zarghan and Aceteria cultivars with rank mean of 30.00. The highest natural parasitism of the safflower fly, A. helianthi by Microdontomerus annulatus was observed on the 9 July and lowest on the 19 June. The highest and lowest percentage of parasitism by Ormyrus gratiosus was observed, respectively on the 19 June and the 2 July. In conclusion, using integrated pest management and crop cultivars suitable for early crop up a lot of damage can be prevented.     

Spatial structure of a subtidal macrobenthic community in the Bay of Veys (western Bay of Seine, English Channel)

The spatial distribution of the muddy fine sand community from the Bay of Veys (western English Channel) were investigated during spring and autumn 1997. A grid of 55 and 54 sites was sampled in March and October, respectively, using two replicates per site of a Hamon grab (0.25 m²) for macrofauna collection and an additional one for sediment analysis. A total of 172 species were sampled with a dominance of polychaetes, followed by crustaceans and bivalves. The species richness and abundance show low temporal changes despite higher values in October than in March. In March, the mean abundance was 165 ind. 0.5 m⁻²; in October, the mean abundance was 212 ind. 0.5 m⁻². Four assemblages from the Abra alba-Pectinaria koreni community were identified corresponding to a bathymetric and sedimentary gradient from muddy fine sands with high levels of fine particles in shallow water to fine sands in deeper water. The discussion focuses on factors prevailing on the spatial structure of sandy communities in the English Channel.     

Chitin production by Ampelisca (Amphipoda) populations from a fine sand community in the Bay of Morlaix (English channel)

We measured chitin biomass and production in five species of Ampelisca (Crustacea Amphipoda) living on a fine sand community at Pierre Noire Station in the Bay of Morlaix (Western English Channel, Brittany, France). Taking into account the maxima of their mean total production, the annual chitin production was estimated at between 600 and 900 mg m^–2 yr^–1. These values are close to those of the chitin production of pioneering benthic communities growing on naked substrates in the coastal waters of Calvi bay (Mediterranean, Corsica) between 7 to 28 meter depth, and of the zooplankton of that same area.