Life cycle and population dynamics of Annina mesopotamica (Ahmed), (Isopoda, Flabellifera) in the Shatt Al-Arab Region, Basrah, Iraq

A population of the intertidal, ovoviviparous, cirolanid isopod Annina mesopotamica was studied at the Al-Chibassy tributary of the Shatt Al-Arab river from 14 May 1973 to 29 April 1974, and at the Garmat-Ali river of the Shatt Al-Arab, Basrah, Iraq from 5 November 1984 to 30 June 1986. Population density varied between 128 to 5760 individuals m^–2 with a mean of 1218 m^–2. Highest numbers occurred between June and September. Breeding extended for most of the year except November/January to February/March, although ovigerous females were present throughout the year. The incubation period varied with season, and was ca. 2 weeks during the warmest period, and about a month at lower temperatures. Egg numbers varied between 4 to 66 with mean 24. Brood size was linearly proportional to female size. The size frequency distribution of the population was polymodal with a predominance of females over males. Four different types of growth curves were found: exponential, concave, convex, and intermediate between concave and convex. Growth rate varied between 0.63 and 2.19 mm month^–1. Mortality was higher among summer cohorts. Life span varied between 5 and 11 months.     

Effect of pollution on phytoplankton in the Ashar Canal,a highly polluted canal of the Shatt al-Arab Estuary at Basrah,Iraq

The effect of pollution on the phytoplankton in the Ashar Canal was studied during March and June 1976. Higher temperatures were recorded in June. The canal water was more turbid than that of the adjoining Shatt al-Arab estuary due to high algal populations and sewage disposal. The chlorosity values were remarkably high in the canal, due to sewage disposal. The flood waters in June lowered the chlorosity in both estuary and canal. Sewage disposal into the canal decreased its dissolved oxygen content. The lower oxygen values in the estuary in June were accompanied with higher temperatures. The pH values were generally higher in the estuary and were also higher in June than in March.Eighty-six algal taxa were recorded, 45 of which were diatoms. The phytoplankton in the estuary was more abundant in March, due to the increase in currents and turbidity in June. The Chlorophyta, Conjugatophyta, Myxophyta and Bacillariophyta in the estuary showed reverse seasonal trends from those of the total phytoplankton. These algal seemed to flourish during periods of high temperatures. The dense blue-green algae recorded in June is attributed to the high temperature and dissolved organic matter. The Chrysophyta recorded high populations in the estuary in March and were totally absent in June. Lower temperatures and high transparency in March might have led to their relative abundance.The total phytoplankton in the Ashar Canal followed two different seasonal trends, one resembling and the other differing from those in the estuary. The disposal of domestic sewage and agricultural wastes in the canal seemed to lead to such adverse seasonal variations. The diatoms only dominated the phytoplankton at one station in both months. The sewage and agricultural wastes disposal seemed to favour the abundance of the other phyla than the diatoms. Increased organic load in the canal has led to a considerable increase in the Myxophyta in June. Blooms of Chlamydomonas sp. and Euglena acus increased the phytoplankton densities in March at stations II and IV, respectively. Benthic or periphytic algae were found in the phytoplankton populations. Raised salinity seemed to restrict the distribution of the planktonic diatom Bacillaria paradoxa. Among the noticeable widespread planktonic algae in the study area are Dinobryon sertularia, Pediastrum duplex and P. simplex.     

Investigations on the meiofauna and sediment of the Shatt Al-Arab near Basrah (Iraq)

SUMMARY. Sediment quality and meiofauna distribution were investigated in the Shatt Al-Arab near Basrah (Iraq). Four stations were fixed in a transect reaching from the eulittoral to the main channel of the river. The sediment was investigated with respect to wet mud density, dry mud density, water content, organic matter, calcareous substances, and allochthonous inorganic materials. There were no major differences between the sediments taken at the different stations. Sediment quality was not a limiting factor for the distribution of meiofauna; important factors were water current, light penetration and temperature. The current has a great influence on sediment structure, the main channel of the river had harder sediment consisting of clay. Because of high turbidity, light can reach the bottom only in shallow water at stations I and II; macrophytes were present only at these two stations. The highest numbers of invertebrates were found at station II (0.5 m depth). As water depth increased, the abundance of meiofauna decreased. Nevertheless, the number of individuals at station I (0.05 m) in the tidal zone was lower than at station II. This fact can be explained by the magnitude of changes of the environmental conditions, especially temperature and insolation. There were very large diurnal temperature fluctuations, fluctuating between 10 and 25°C on a single day. Many meiofauna species cannot tolerate such fluctuations and colonize mainly the deeper reaches of the river, which are continuously covered by water. Stronger currents in the middle of the river prevent the settlement of large numbers of animals in this area.     

Possible relation between phytoplankton numbers and Saprolegnioid fungi in Shatt Al-Arab near Basrah,Iraq

This study, carried out in Shatt Al-Arab river near Basrah, Iraq, reports a close negative (inverse) relation between phytoplankton numbers and decomposing fungi belonging to the family Saprolegniaceae (Oomycetes). This relation seems to depend on substrate relationship and antagonism. In addition the role of other physico-chemical factors, pH, temperature and salinity has been discussed.     

Desmids of the Basrah District,South Iraq

79 taxa of desmids belongig to 17 genera were observed in 17 samples collected from several parts in Basrah district, South Iraq. 3 genera viz. Actinotaenium, Docidium and Spondylosum, and 41 taxa are new records for Iraqi waters. Distribution of taxa in the area studied as well as in the whole country (when available) are given. Some slight morphological variations in desmids were observed due to the alkaline nature of water.     

Observations of stranded and swimming whale sharks Rhincodon typus in Khor Al-Zubair,NW Arabian Gulf and Shatt Al-Arab Estuary,Iraq

This study is the first record of a whale shark Rhincodon typus in Iraqi waters and the second record from the Arabian (Persian) Gulf portion of the north-west Indian Ocean. The stranding and sighting events were documented by photos of three individuals: the stranded specimen was 6.5 m total length (L_T) and the free-swimming individuals were c. 1–2 and 2–3 m L_T respectively_. An appeal is made for Iraqi policy makers to participate in regional and international organizations for the conservation of this endangered species.     

Studies on the Genus Vaucheria (Xanthophyceae) in Iraq

Eight species of Vaucheria from southern Iraq, V. dichotoma, V. sessilis, V. erythrospora, V. verticillata, V. hamata, V. woroniniana, V. synandra, and V. longicaulis were studied and described. All but V. sessilis and V. longicaulis are recorded for the first time from Iraq.     

Relationship between opercular girth, maximum girth and total length of fishes caught in gillnets in the estuarine and lower river sections of Shatt al-Arab River (Basrah Province, Iraq)

In fisheries, the two morphological parameters of opercular and maximum girth are related to the effectivity of capture methods in gilled and wedged fish, respectively. The present work investigates the relationship between opercular ( G _ope) and maximum girths ( G _max) to total length ( L _t) for 10 fish species captured from Shatt al-Arab River, Basrah, Iraq. Data were collected October 2005 to December 2006. Cyprinids were the best represented family with six species; engraulids, silurids, heteropneustids and mugilids were each represented by one species. G _ope and G _max were found to increase linearly with total length of all species, all r ² values being greater than 0.73 and statistically significant (P < 0.01). When G _ope and G _max for all species were plotted against total length, two groups were identified ( G 1, G 2), corresponding to general girth-length relationships: (a) G 1 = −0.252 + 0.424 L _t and G 2 = −0.262  +  0.600 L _t for opercular girth and, (b) G 1 = 1.538 + 0.419 L _t and G 2  =  1.538  +  0.696 L _t for maximum girth. These groups correspond to different body shapes of fishes: G 1-round and G 2-compressed. These relationships have implications when using length data and mesh size to determine size selectivity of gill nets.     

Ecosystem and macrophyte primary production of the Fort River,Massachusetts

Primary production and ecosystem respiration of the Fort River ecosystem, a medium size (mean discharge 1.4 m³/sec) lowland stream in central Massachusetts, U.S.A., were measured using diurnal oxygen techniques from May 1972 to November 1973. During the summer of 1973, vascular hydrophyte production was measured with a modified cropping technique. Whole ecosystem gross primary production ranged from 0.44 g O₂/m²:day in winter to 6.50 g O₂/m^2.day in summer, and averaged 1.78 g O₂/m^2.day for 12 months. Mean ecosystem respiration was 3.65 g O₂/m^2.day for 12 months. Mean ecosystem respiration was 3.65 g O₂/m^2.day.Macrophyte gross production (59.9 g O₂/m^2.year) constitutes 9.2% of annual ecosystem productivity and 15.2% of summer primary production. Macrophytes were little grazed and entered food webs only after death, as detritus. Decomposition occurred near the site of production at relatively rapid rates, thus transport of dead macrophyte material in stream water was low. Data from this and other stream ecosystems suggest that in general, streams are only moderately productive ecosystems which depend to varying degrees on watershed-derived organic matter inputs.     

Primary production and biomass on a Dutch salt marsh: emphasis on the below-ground component

The primary production and below-ground biomass of angiosperms were measured in four almost monospecific vegetation stands situated on a salt marsh along the Oosterschelde estuary, The Netherlands. Maximum below-ground biomass values found for Spartina anglica, Elymus pycnanthus, Halimione portulacoides and Triglochin maritima, were very high relative to values reported from other European salt marshes: 12 586, 9 717, 17 737 and 16 121 g m^-2 respectively. These relatively high values may be due to the fineness of the sieve used, compared to other studies. The actual values are likely to be even higher because the sample treatment has probably caused loss of fine root material. Below-ground production estimates, based on the difference between maximum and minimum biomass, yielded: 6 044 g m^-2 yr^-1 for Spartina, 4 421 g m^-2 yr^-1 for Elymus, 7 799 g m^-2 yr^-1 for Halimione and 3 475 g m^-2 yr^-1 for Triglochin. This high production is mainly concentrated in the deeper layers of the root environment (20–60 cm). Although these production figures are considerably higher than those generally reported for comparable species or vegetation types in Europe, statistical evidence suggests that, for the first three species, they are real values rather than figures caused by random fluctuations.     

河口、海湾生态系统初级生产力研究进展

河口及海湾生态系统与大洋生态系统相比,其理化环境因子复杂多样,且易受近岸人类活动的影响,生态系统多样性更高。初级生产力是河口及海湾生态系统研究的重要内容之一,也是渔业资源评估、水环境评价及生态环境治理等方面的重要参数。本文综述了近十年来河口及海湾初级生产力相关研究所取得的成果与进展,并从河口及海湾水域影响初级生产力的主要环境因子、初级生产力的粒级结构、赤潮机理研究、初级生产力估算方法等方面的相关研究对河口及海湾初级生产力的特点进行归纳总结,并对现在相关水域初级生产力估算的技术发展和研究重点进行了探讨和展望。     

Abundance and seasonal migrations of the penaeid shrimp Metapenaeus affinis (H. Milne-Edwards) within Iraqi waters

Migration of Metapenaeus affinis (H. Milne-Edwards) from the Arabian Gulf to nursery grounds in the inland waters of Iraq extends from May/June to January/February. Shrimp ranging in size from 3–125 mm total length were found in inland waters. In the shallow waters of the Al-Assaflya small-sized shrimp only were caught, while in the Marshes large-sized shrimp were abundant. Maximum numbers of recruits were recorded when temperatures reached 23–25 °C. However, the discharge of the Shatt Al-Arab may also be an important factor regulating recruitment.The growth rates of small shrimp were higher than those of large ones. There mostly was, a preponderance of females over males. Spawning at sea appears to occur immediately after emigration. Gonad development was not observed. Commercial landings, at the two main fish markets at Basrah, during September–November 1985 averaged 1000 kg day^–1.     

Contrasting effects of rabbit exclusion on nutrient availability and primary production in grasslands at different time scales

Herbivores influence nutrient cycling and primary production in terrestrial plant communities. However, both empirical and theoretical studies have indicated that the mechanisms by which herbivores influence nutrient availability, and thus their net effects on primary production, might differ between time scales. For a grassland in southeast England, we show that the effects of rabbits on primary production change over time in a set of grazed plots paired with exclosures ranging from 0 to 14 years in age. Herbivore exclusion decreased net aboveground primary production (APP) in the short term, but increased APP in the long term. APP was closely correlated with N mineralization rates in both grazed and ungrazed treatments, and accumulation of litter within the grazing exclosures led to higher N mineralization rates in exclosures in the long run. Rabbit grazing did not influence litter quality. The low contrast in palatability between species and the presence of grazing-tolerant plants might prevent rabbits from favoring unpalatable plant species that decompose slowly, in contrast to results from other ecosystems. Our results indicate that it is essential to understand the effects on N cycling in order to predict the effect of rabbit grazing on APP. Rabbits might decrease N mineralization and APP in the long term by increasing losses of N from grasslands.     

Relationship of bacterioplankton production with primary production and respiration in a shallow estuarine system (Ria de Aveiro, NW Portugal)

The response of bacterial growth to phytoplankton production and planktonic respiration (RESP) variation was examined over different stations and dates in the shallow estuarine system Ria de Aveiro. The temporal and spatial profiles of bacterial productivity (2.7-744.2mg Cm(-3)d(-1)) did not coincide with those of primary production (PP) (0.2-19.1 g Cm(-3)d(-1)) and RESP (0.1-8.2 g Cm(-3) d(-1)). The bacterioplankton production/PP ratio varied differently, depending on the season and location. The heterotrophic zones, with the lowest values of PP, exhibited the most intense bacterial secondary production. Moreover, the variation of PP in the system was rather small when compared with that of bacterial secondary production. These suggest that, in a large extension of the lagoon and throughout the year, bacterioplankton growth is largely dependent on non-phytoplanktonic carbon sources. Benthic PP and/or allochtonous organic matter from land have a fundamental role in the dynamics of the planktonic compartment of the estuarine system.     

Nutrients,light and primary production by phytoplankton and microphytobenthos in the eutrophic,turbid Westerschelde estuary (The Netherlands)

Abiotic factors and primary production by phytoplankton and microphytobenthos was studied in the turbid Westeschelde estuary. Because of the high turbidity and high nutrient concentrations primary production by phytoplankton is light-limited. In the inner and central parts of the estuary maximum rates of primary production were therefore measured during the summer, whereas in the more marine part spring and autumn bloom were observed. Organic loading is high, causing near anaerobic conditions upstream in the river Schelde. Because of this there were no important phytoplankton grazers in this part of the estuary and hence the grazing pressure on phytoplankton was minimal. As this reduced losses, biomass is maximal in the river Schelde, despite the very low growth rates.On a number of occasions, primary production by benthic micro-algae on intertidal flats was studied. Comparison of their rates of primary production to phytoplankton production in the same period led to the conclusion that the contribution to total primary production by benthic algae was small. The main reason for this is that the photosynthetic activity declines rapidly after the flats emerged from the water. It is argued that CO₂-limitation could only be partially responsible for the noticed decrease in activity.     

Bacterioplanktonic biomass and production in the river Meuse (Belgium)

This paper presents results of bacterial biomass determination by epifluorescence microscopy after acridine orange staining and ³H-thymidine incorporation measurements in the river Meuse. Bacterial production is calculated from thymidine incorporation using an experimental conversion factor (0.5 10¹⁸ bacterial cells produced per mole of thymidine incorporated into macromolecules). Seasonal variations of bacterial biomass and production at two stations are presented. Biomass ranges between 0.05 mgC · 1⁻¹ (in winter) and 0.8 mgC · 1⁻¹ (in summer). The variations of bacterial production seem to be closely linked to those of primary production; values lower than 1 μgC · 1⁻¹ · h⁻¹ are found in winter and high values (> 5 μgC 1⁻¹ · h ⁻¹) in summer. Longitudinal profiles in the Belgian course of the river show important increase of biomass and production from upstream to downstream. Bacterial growth yield (Y) has been determined (Y = 0.3) in order to calculate bacterial carbon uptake from bacterial production.     

Density,production and life cycle of Brachycentrus subnubilus Curtis (Trichoptera: Brachycentridae) in a lowland river,Central Poland

The annual mean density of Brachycentrus subnubilus a trichopteranspecies with a univoltine life-cycle was 572 ind. m^-2. Itconstituted of only 2.1% of the total macrozoobenthos abundance,while this species in terms of biomass exceeded 11.9% of the totalbenthic biomass. Production of Brachycentrus subnubilus was estimated bysize-frequency method was 26.56 g wet weight m^-2 and theturnover ratio was 5.7.     

Epipelic and pelagic primary production in Alaskan Arctic lakes of varying depth

We compared on eight dates during the ice-free period physicochemical properties and rates of phytoplankton and epipelic primary production in six arctic lakes dominated by soft bottom substrate. Lakes were classified as shallow ( < 2.5 m), intermediate in depth (2.5 m <  < 4.5 m), and deep ( > 4.5 m), with each depth category represented by two lakes. Although shallow lakes circulated freely and intermediate and deep lakes stratified thermally for the entire summer, dissolved oxygen concentrations were always >70% of saturation values. Soluble reactive phosphorus and dissolved inorganic nitrogen (DIN = NO₃ ⁻–N + NH₄ ⁺–N) were consistently below the detection limit (0.05 μmol l⁻¹) in five lakes. However, one lake shallow lake (GTH 99) periodically showed elevated values of DIN (17 μmol l⁻¹), total-P (0.29 μmol l⁻¹), and total-N (33 μmol l⁻¹), suggesting wind-generated sediment resuspension. Due to increased nutrient availability or entrainment of microphytobenthos, GTH 99 showed the highest average volume-based values of phytoplankton chlorophyll a (chl a) and primary production, which for the six lakes ranged from 1.0 to 2.9 μg l⁻¹ and 0.7–3.8 μmol C l⁻¹ day⁻¹. Overall, however, increased resulted in increased area-based values of phytoplankton chl a and primary production, with mean values for the three lake classes ranging from 3.6 to 6.1 mg chl a m⁻² and 3.2–5.8 mmol C m⁻² day⁻¹. Average values of epipelic chl a ranged from 131 to 549 mg m⁻² for the three depth classes, but levels were not significantly different due to high spatial variability. However, average epipelic primary production was significantly higher in shallow lakes (12.2 mmol C m⁻² day⁻¹) than in intermediate and deep lakes (3.4 and 2.4 mmol C m⁻² day⁻¹). Total primary production (6.7–15.4 mmol C m⁻² day⁻¹) and percent contribution of the epipelon (31–66%) were inversely related to mean depth, such that values for both variables were significantly higher in shallow lakes than in intermediate or deep lakes. Handling editor: L. Naselli-Flores     

Seasonal flooding,soil salinity and primary production in northern prairie marshes

Hydrologic regime is an important control of primary production in wetland ecosystems. I investigated the coupling of flooding, soil salinity and plant production in northern prairie marshes that experience shallow spring flooding. Field experiments compared whitetop (Scolochloa festucacea) marsh that was: (1) nonflooded, (2) flooded during spring with 25 cm water and (3) nonflooded but irrigated with 1 cm water · day^–1. Pot culture experiments examined whitetop growth response to salinity treatments. The electrical conductivity of soil interstitial water (EC_e) at 15 cm depth was 4 to 8 dS· m^–1 lower in flooded marsh compared with nonflooded marsh during 2 years. Whitetop aboveground biomass in flooded marsh (937 g · m^–2, year 1; 969 g · m^–2, year 2) exceeded that of nonflooded marsh (117 g · m^–2 year 1; 475 g · m^–2, year 2). Irrigated plots had lower EC_e and higher aboveground biomass than nonflooded marsh. In pot culture, EC_e of 4.3 dS · m^–1 (3 g · L^–1 NaCl) reduced total whitetop biomass by 29 to 44% and EC_e of 21.6 dS · m^–1 (15 g · L^–1 NaCl) reduced biomass by more than 75%. Large reductions of EC_e and increases of whitetop growth with irrigation indicated that plants responded to changes in soil salinity and not other potential environmental changes caused by inundation. The results suggest that spring flooding controls whitetop production by decreasing soil salinity during spring and by buffering surface soils against large increases of soil salinity after mid-summer water level declines. This mechanism can explain higher marsh plant production under more reducing flooded soil conditions and may be an important link between intermittent flooding and primary production in other wetland ecosystems.     

乌鲁木齐河源区高寒冰缘植被的生态特征研究

对乌鲁木齐河源区高寒冰缘植被进行了调查和生态环境分析。研究了高寒冰缘植物对寒区环境在形态结构和繁殖方式等方面的适应特征及其生态对策,在该区域垂直带谱中,植被包括了两个垂直带;高山草甸和高山垫状植被。主要植物群系有：苔草群系、蒿草群系、早熟禾群系、四蕊山莓草系、高山红景天群系、族生柔籽草群系、珠芽蓼群系等７个,共包括２７类植物群（群丛）此外,在高山流石堆上具有有牌演替早期阶段的高山植物群聚。决定该区