Freshwater Components Research Articles

Seven Decades of Change in the Zooplankton (s.l.) of the Nile Delta Lakes (Egypt), with Particular Reference to Lake Borullus

AbstractAround the 1930s, the zooplankton (and benthos) of the Nile delta lakes, and Lake Borullus in particular, had a mixed, eutrophic facies, with marine and mesohaline elements dominant for about eight months per year, and freshwater species taking over during the four months of the Nile flood. After the Aswan dam became operational, this regime changed: a steady supply of agricultural drainage water of Nilotic origin consistently freshened the delta. Thus, except in the immediate vicinity of their outlet to the sea, the lakes became almost fresh. Only during the rare and short‐lived (one‐three weeks) occasions when Aswan closes in winter, marine water is sucked in, and along with it, a saline fauna temporarily becomes re‐established in the east and centre of lake Borullus, and presumably of the other delta lakes as well. This marine fauna remained the same over 70+ years of observations. The freshwater component, in contrast, partly nilotic, partly mediterranean, changed deeply over time. First, the fraction of species from temporary waters disappeared, as well as (among copepods and cladocerans) all large‐bodied species. Several cladocerans and copepods with a euro‐mediterranean range appeared and diluted the pre‐existing Afrotropical fauna. The abundance of small cladocerans and, especially, rotifers increased by a factor ten or more. This latter change is believed to reflect two pressures. In a first phase, a re‐arrangement of the lake's fish fauna (a top down force) occurred. Freshwater fish replaced marine diadromic species, and their predation pressure on the zooplankton preferentially removed large‐bodied prey. In a second phase, increased agricultural drainage caused eutrophication (a bottom‐up force) and larger filtrators (cladocerans, some copepods) began to be replaced by small filtrators (rotifers). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Freshwater budget of the Canada Basin, Arctic Ocean, from salinity, δ18O, and nutrients

The contribution of freshwater components (e.g., meteoric, sea ice, and Pacific water) in the Canada Basin is quantified using salinity, δ18O, and nutrient data collected in 2003 and 2004. The penetration depth of sea ice meltwater is limited to the upper 30 m, and brine, rejected during sea ice formation, is observed from 30 to 250 m depth. The fraction of meteoric water is high in the upper 50 m and decreases with depth. Pacific water entering via Bering Strait is the main source of freshwater below 50 m depth. Bering Strait throughflow, which transports Pacific water with salinity 32.5 together with meteoric water supplied upstream of the Bering Strait, contributes up to 75% of freshwater input (>3200 km3 a−1) to the Canada Basin. The mean residence time of Pacific water in the Canada Basin is estimated to be 11 years. Precipitation and river runoff from both North American and Eurasian continents add >800 km3 a−1 and sea ice formation removes <900 km3 a−1 (<0.6 m a−1) of fresh water. The export of ice and liquid fresh water from the Canada Basin contributes ∼40% of the freshwater flux from the Arctic Ocean to the North Atlantic Ocean.

A GAP ANALYSIS AND COMPREHENSIVE CONSERVATION STRATEGY FOR RIVERINE ECOSYSTEMS OF MISSOURI

North America harbors an astounding proportion of the world's freshwater species, but it is facing a freshwater biodiversity crisis. A first step to slowing the loss of biodiversity involves identifying gaps in existing efforts to conserve biodiversity and prioritizing opportunities to fill these gaps. In this monograph we detail two separate, but complementary, conservation planning efforts—a Gap Analysis (GAP) and a State Wildlife Action Plan (WAP)—for Missouri that address this first step. The goal of the Missouri Aquatic GAP Project was to identify riverine ecosystems, habitats, and species not adequately represented (i.e., gaps) within existing conservation lands. The goal of the freshwater component of the Missouri Wildlife Action Plan was to identify and map a set of conservation‐opportunity areas (COAs) that holistically represent all riverine ecosystems, habitats, and species in Missouri. Since conservation planning is a geographical exercise, both efforts utilized geographic information systems (GIS). Four principal GIS data sets were used in each planning effort: (1) a hierarchical riverine ecosystem classification, (2) predicted species distributions, (3) public ownership/stewardship, and (4) a human‐threat index. Results of the gap analyses are not encouraging. Forty five, mostly rare, threatened, or endangered, species are not represented in lands set aside for conserving biodiversity. Results also illustrate the fragmented nature of conservation lands, which are mainly situated in the uplands and fail to provide connectivity among riverine habitats. Furthermore, many conservation lands are severely threatened by an array of human disturbances. In contrast, results of the WAP provide hope that relatively intact riverine ecosystems still exist. A total of 158 COAs, representing ∼6% of the total kilometers of stream in Missouri, were selected for the WAP. This illustrates that a wide spectrum of biodiversity can be represented within a small portion of the total resource base, but the area of conservation concern is often much larger. Identifying priority riverscapes for conservation is an important first step toward effective biodiversity conservation. Yet, achieving the ultimate goal of conserving biodiversity will require vigilance on the part of all responsible parties, with particular attention to addressing and coordinating the many remaining logistical tasks.

Geochemical evidence of seawater intrusion into a coastal geothermal field of central Greece: example of the Thermopylae system

Thermal water of Thermopylae and from other geothermal fields located in the southern part of the Sperchios basin (central Greece) are characterized by high salinity (total dissolved salts, or TDS, range from 1.2 to 30.3 g L−1) associated with a degassing of CO2. To determine the mineralization processes, geochemical and isotopic investigations (major elements, 18O, 2H and 13C) have been carried out upon 17 thermal waters from springs and boreholes. This study emphasizes that all the thermal waters result from the mixing of a seawater end-member, several fresh water components depending on the field location, and a mantle-derived CO2 rising upward through an E–W fault system. The seawater identified in the thermal mixture is likely to be evolved Aegean seawater (ASW). Once intruded into the basin sediments, the trapped seawater has its chemical content modified by both water–rock interactions and massive dissolution of the deep CO2 (pCO2 of 100.5 atm). The modelling performed with PHREEQC indicates that the anomalous major ion ratios measured in the so-called evolved ASW are explained by the dissolution of calcite and dolomitization process associated to precipitation of gypsum within the thermal aquifer.

Distribution, characteristics and potential impacts of chromophoric dissolved organic matter (CDOM) in Hudson Strait and Hudson Bay, Canada

The characteristics of chromophoric dissolved organic matter (CDOM) were studied in Hudson Bay and Hudson Strait in the Canadian Arctic. Hudson Bay receives a disproportionately large influx of river runoff. With high dissolved organic matter (DOM) concentrations in Arctic rivers the influence of CDOM on coastal and ocean systems can be significant, yet the distribution, characteristics and potential consequences of CDOM in these waters remain unknown. We collected 470 discrete water samples in offshore, coastal, estuarine and river waters in the region during September and October 2005. Mixing of CDOM appeared conservative with salinity, although regional differences exist due to variable DOM composition in the rivers discharging to the Bay and the presence of sea-ice melt, which has low CDOM concentrations and low salinity. There were higher concentrations of CDOM in Hudson Bay, especially in coastal waters with salinities < 28 , due to river runoff. Using CDOM composition of water masses as a tracer for the freshwater components revealed that river runoff is largely constrained to nearshore waters in Hudson Bay, while sea-ice melt is distributed more evenly in the Bay. Strong inshore–offshore gradients in the bio-optical properties of the surface waters in the Hudson Bay cause large variation in penetration of ultraviolet radiation and the photic depth within the bay, potentially controlling the vertical distribution of biomass and occurrence of deep chlorophyll maxima which are prevalent only in the more transparent offshore waters of the bay. The CDOM distribution and associated photoprocesses may influence the thermodynamics and stratification of the coastal waters, through trapping of radiant heating within the top few meters of the water column. Photoproduction of biologically labile substrates from CDOM could potentially stimulate the growth of biomass in Hudson Bay coastal waters. Further studies are needed to investigate the importance of terrestrial DOM in the Hudson Bay region, and the impact of hydroelectric development and climate change on these processes.

The tracing of riverine U in Arctic seawater with very precise 234U/ 238U measurements

The riverine flux of U that enters the deep oceans is not well constrained since the net losses during estuarine mixing are difficult to quantify. Riverine-dissolved U normally has a higher 234U/ 238U activity ratio ( 234U/ 238U ar) than the uniform value that characterizes open ocean seawater and could be used as a tracer of riverine inputs if one could resolve subtle variations in seawater composition. Using new mass spectrometry techniques we achieve a long-term reproducibility ± 0.3‰ on 234U/ 238U ar which permits the tracing of riverine U in seawater samples from the Arctic – a partially restricted basin that is ideal for such a study. We find that surface waters from the Arctic basins carry elevated 234U/ 238U ar when compared with deep ocean seawater. Samples from the Canada Basin have a significant freshwater component and provide evidence that the Mackenzie River loses ∼ 65% of its U in the Mackenzie shelf/estuary zone before entering the deeper basin. This is in contrast to samples from the Makarov Basin, which provide evidence that all of the freshwater input is derived from the major Yenisey River alone, despite the proximity of the Lena and Ob Rivers. The differing behaviour of U between the Mackenzie and Yenisey Rivers is most likely a consequence of the strong binding of U to dissolved organic matter (DOC) or secondary phases in these rivers. The Yenisey River appears to transport the majority of the DOC through the shelf and into the Makarov Basin. In contrast, the Mackenzie River appears to lose a significant amount of DOC (> 50%) in the estuary/shelf zone, which may lead to loss of associated U. These findings offer a more detailed picture of the fresh riverine water flow patterns in the Arctic Ocean when compared to other geochemical proxies. The non-conservative behaviour of U in the Mackenzie River through the shelf/estuaries has important implications for U input into oceans and the total marine budget.

Crustacean fish parasites from Segara Anakan Lagoon, Java, Indonesia

The present study is the first investigation on ectoparasites of commercial important fish from Segara Anakan, a brackish water lagoon located at the southern coast of Java, Indonesia. Eight economically important marine fish species (Mugil cephalus, Siganus javus, Scatophagus argus, Caranx sexfasciatus, Lutjanus johnii, Eleutheronema tetradactylum, Johnius coitor, and Epinephelus coioides) were examined for crustacean parasites. Prevalence and intensity data for each parasite species are given, together with an analysis of the origin and possible transmission pathways. A highly divers copepod fauna consisting of 23 different species and two isopods was found. All fish species were at least infested with two copepod species, with the exception of L. johnii, S. argus, and M. cephalus. With seven and six species, respectively, they harboured the most species-rich ectoparasite fauna. The copepods Ergasilus sp. 3 and Caligus acanthopagri on S. argus showed the highest prevalence (78.6) and intensity [17.8 (1-233) and 5.3 (1-22)] of infestation. The recorded parasite fauna is represented by marine, brackish water, and probably also freshwater components. The brackish water environment of Segara Anakan does not prevent disease outbreaks due to parasitic copepods by preventing pathogenic marine or freshwater species to enter the lagoon. This might cause fish health problems if the Segara Anakan Lagoon would be developed for finfish mariculture in future.

Bathymetry‐topography effects on saltwater–fresh groundwater interactions around the shrinking Aral Sea

Large‐scale irrigational schemes have drastically reduced the surface water discharge into the Aral Sea, causing a sea surface level lowering of more than 20 m since 1960 and severe water quality deterioration in the region. We investigate the dynamics of submarine groundwater discharge (SGD) into the Aral Sea as well as the saltwater intrusion (SWI) into the coastal groundwater around the Aral Sea during its shrinkage by using the U.S. Geological Survey SUTRA code. Results show that the regional topography and bathymetry largely influence SGD and SWI transients as the Aral Sea shrinks. Considering the flat conditions that prevail in the southeastern Aral Sea and the irrigated Amu Darya delta, SGD drops as the sea starts to shrink because the shoreline displacement prevents seawater inflow to the aquifer and subsequent return flow to the sea. In this flat bathymetry case the groundwater discharging into the Aral Sea becomes as saline as the seawater because saltwater remains below the dried seabed. In contrast, for the steep bathymetry of the essentially uninhabited northwestern region the SGD increases as a combined effect of sea surface lowering, density differences, and storage, with the SGD salinity remaining below seawater salinity and reflecting a considerable freshwater component. Considering the potential for groundwater pumping in the original coastline vicinity for freshwater supply use, our results indicate a decreased risk of SWI in the northwestern Aral Sea region under the post‐1960 sea level lowering conditions.

The Gambia River estuary: A reference point for estuarine fish assemblages studies in West Africa

The Gambia River is one of the last aquatic ecosystems in West Africa that has not yet been affected by strong environmental changes and human disturbances. In contrast to the neighbouring Casamance and Sine Saloum estuaries, the Gambia estuary is free of major climatic perturbation and remains a “normal” estuary, with a salinity range from freshwater to 39. The present paper aims to study the spatial and seasonal variability of fish assemblages in this estuary in terms of bio-ecological categories and of their relation with some environmental variables. Four surveys were conducted, from June 2001 to April 2002, in order to cover the major hydroclimatic events, at 44 sampling sites along the lower, intermediate and upper zones of the Gambia estuary (up to 220 km). Fish assemblages were sampled using a purse seine net, fish were identified to species level and environmental variables such as water depth, transparency, salinity, temperature and percentage oxygen saturation were measured. The main spatial structure of the fish assemblages and its seasonal changes were first studied using the STATIS-CoA multitable method. The combination of fish assemblages and environmental variables was then analysed using the STATICO method, designed for the simultaneous analysis of paired ecological tables. A total of 67 species were observed, belonging to all bio-ecological categories characterizing West African estuaries. The marine component of the community was largely dominant throughout the estuary, while the freshwater component was permanently observed only in the upstream zone. The main spatial structure was a longitudinal gradient contrasting marine and freshwater affinity assemblages, with strong seasonal variations. The most complete gradient was observed in December, at the beginning of the dry and cool season, while in June, at the end of the dry and warm season, there was the least structured gradient. The role of salinity, always correlated with temperature, was emphasized, while turbidity appeared to be another important factor. Oxygen and depth did not play a major role at the estuary scale. The relative importance of the bio-ecological categories varied according to the season and the distance to sea. Stable fish assemblages were observed in the lower zone at the end of the dry season, in the upper zone during the flood and in the middle zone throughout the year. In some situations, a relative inadequacy between fish assemblages and their environment was noticed. The present study contributes to the definition of the functioning of a “normal” West African estuary, the Gambia estuary, with balanced effects of marine and freshwater influences and the presence of all bio-ecological categories. The Gambia estuary can therefore be considered to be a reference ecosystem for further comparisons with other tropical estuarine ecosystems, subjected to natural or artificial perturbations.

Biogeochemical transport in the Loxahatchee River estuary, Florida: The role of submarine groundwater discharge

The distributions of dissolved organic carbon (DOC), Ba, U, and a suite of naturally occurring radionuclides in the U/Th decay series ( 222Rn, 223,224,226,228Ra) were studied during high- and low-discharge conditions in the Loxahatchee River estuary, Florida to examine the role of submarine groundwater discharge in estuarine transport. The fresh water endmember of this still relatively pristine estuary may reflect not only river-borne constituents, but also those advected during active groundwater/surface water (hyporheic) exchange. During both discharge conditions, Ba concentrations indicated slight non-conservative mixing. Such Ba excesses could be attributed either to submarine groundwater discharge or particle desorption processes. Estuarine dissolved organic carbon concentrations were highest at salinities closest to zero. Uranium distributions were lowest in the fresh water sites and mixed mostly conservatively with an increase in salinity. Suspended particulate matter (SPM) concentrations were generally lowest (< 5 mg L − 1 ) close to zero salinity and increased several-fold (∼ 18 mg L − 1 ; low discharge) toward the seaward endmember, which may be attributed to dynamic resuspension of bottom sediments within Jupiter Inlet. Surface water-column 222Rn activities were most elevated (> 28 dpm L − 1 ) at the freshwater endmember of the estuary and appear to identify regions of the river most influenced by the discharge of fresh groundwater. Activities of four naturally occurring isotopes of Ra ( 223,224,226,228Ra) in this estuary and select adjacent shallow groundwater wells yield mean estuarine water-mass transit times of less than 1 day; these values are in close agreement to those calculated by tidal prism and tidal frequency. Submarine groundwater discharge rates to the Loxahatchee River estuary were calculated using a tidal prism approach, an excess 226Ra mass balance, and an electromagnetic seepage meter. Average SGD rates ranged from 1.0 to 3.8 × 10 5 m 3 d − 1 (20–74 L m − 2 d − 1 ), depending on river-discharge stage. Such calculated SGD estimates, which must include both a recirculated as well as fresh water component, are in close agreement with results obtained from a first-order watershed mass balance. Average submarine groundwater discharge rates yield NH 4 + and PO 4 − 3 flux estimates to the Loxahatchee River estuary that range from 62.7 to 1063.1 and 69.2 to 378.5 μmol m − 2 d − 1 , respectively, depending on river stage. SGD-derived nutrient flux rates are compared to yearly computed riverine total N and total P load estimates.

Linkages among runoff, dissolved organic carbon, and the stable oxygen isotope composition of seawater and other water mass indicators in the Arctic Ocean

Flow‐weighted dissolved organic carbon (DOC) concentrations and δ18O values were determined from major arctic rivers, specifically the Ob, Yenisey, Lena, Kolyma, Mackenzie, and Yukon during 2003–2004. These data were considered in conjunction with marine data for DOC, δ18O values, nutrients, salinity, and fluorometric indicators of DOC obtained during sampling at the shelf‐basin boundary of the Chukchi and Beaufort seas. On the basis of these data, freshwater in the sampled marine waters is likely derived from regional sources, such as the Mackenzie, the Bering Strait inflow, and possibly eastern Siberian rivers, including the Kolyma, or the Lena, but not rivers farther west in the Eurasian arctic. Freshwater from melted sea ice is insignificant over annual cycles, although melted sea ice was a locally dominant freshwater component following summer sea‐ice retreat in 2002. DOC concentrations were correlated with the runoff fraction, with an apparent meteoric water DOC concentration of 174 ± 1 μM. This is lower than the flow‐weighted concentrations measured at river mouths of the five largest Arctic rivers (358 to 917 μM), indicating removal of DOC during transport through estuaries, shelves and in the deep basin. Flow‐weighted DOC concentrations in the two largest North American arctic rivers, the Yukon (625 μM) and the Mackenzie (358 μM), are lower than in the three largest Eurasian arctic rivers, the Ob (825 μM), the Yenesey (858 μM), and the Lena (917 μM). A fluorometer responding to chromophoric dissolved organic matter (CDOM) was not correlated with DOC concentrations in Pacific‐influenced surface waters unlike previous observations in the Atlantic layer. Nutrient distributions, concentrations, and derived ratios suggest the CDOM fluorometer may be responding to the release of chromophoric materials from shelf sediments. Shipboard incubations of undisturbed sediment cores indicate that sediments on the Bering and Chukchi Sea shelves are a net source of DOC to the Arctic Ocean.

Molecular Systematics of the Genus Cottus (Scorpaeniformes: Cottidae)

Abstract To evaluate the monophyly of Cottus and to identify species groups within the genus we generated a data set of 1914 base pairs of mitochondrial DNA (cytochrome b and ATPase 8 and 6) for 87 individuals representing 36 of the 42 currently recognized species of the genus. Both parsimony and Bayesian analyses consistently supported non-monophyly of Cottus with respect to the Baikalian sculpins and the genus Leptocottus. Analyses also supported recognition of five clades within the genus Cottus. These are referred to herein as the Cottopsis, Uranidea, Baikalian, Cottus, and Cephalocottus clades. These clades encompass all but ten recognized Cottus species, nine whose placement was uncertain in our analyses and one not included in our analyses. Lastly, we recognize a freshwater sculpin clade comprising the most speciose freshwater component of the family Cottidae.

Tidal Load and Salt Water Influences on Submarine Ground Water Discharge

AbstractField measurements were conducted to characterize the influences of salt water and tidal loading on submarine ground water discharge (SGD) into West Neck Bay on Shelter Island, New York. SGD was continuously recorded at three sites using an ultrasonic ground water seepage meter, and the spatial extents of the terrestrially derived SGD and the salt water/fresh water mixing zone were inferred from electrical conductivity profiling. While SGD increases with increasing hydraulic gradient in the far field of the coastal aquifer, shorter temporal variations of SGD were inversely correlated with tidal stage. SGD and hydraulic heads in the onshore unconfined aquifer near the coast responded asymmetrically to tidal loading, with discharge and head increasing faster than decreasing. A time lag of ∼1 h was observed between the tidal load and responses in onshore head and SGD. This lag represents a manifestation of the travel time required for tidal influences to propagate landward before the hydraulic gradient adjusts and influences seepage. The spatial extent of the fresh water component of SGD determined by electrical conductivity profiles, seepage velocity, and the time lag between tide and SGD amplitudes are in reasonable agreement with analytic estimates.

Concentration and distribution of dissolved amino acids in a shallow hydrothermal system, Vulcano Island (Italy)

Hydrothermal systems are known to harbor a large number of microorganisms, but the organic chemical composition of the solution that comprises their potential substrate is largely unknown. Concentrations and distributions of dissolved free amino acids (DFAA) and dissolved combined amino acids (DCAA) were determined in fluids from the moderate-temperature (42–89 °C), shallow hydrothermal system on the volcanically active island of Vulcano, Italy. The seven samples represent three different geological settings on the island; shallow (∼1 m) submarine vents, geothermal wells, and seeps in heated beach sediments, in addition to ambient local seawater from the bay, Baia di Levante. All hydrothermal sites, with one exception, had TDAA concentrations that were 3–114 times higher than local seawater in Baia di Levante. There were large similarities in amino acid concentration and composition among samples from the same geological setting. The highest amino acid concentrations were found at sites with acidic and reducing conditions, which also had the largest freshwater component. An unusually high fraction of the TDAA pool was represented by DFAA (33–87%), possibly due to in situ acid hydrolysis of DCAA to DFAA. Both DFAA and DCAA concentrations were correlated to DOC, indicating similar source and sink functions for these pools. The yield of TDAA (TDAA-carbon as fraction of organic carbon) ranged from 2% to 25%, which is high compared with non-hydrothermal settings, and indicates high biological lability. The mole fraction of β-alanine plus γ-aminobutyric acid (%BALA + GABA) was 2–2.7% of TDAA, also indicating high biological lability. Owing to the high over-all amino acid concentrations, the high fraction of DFAAs, and the high biological lability of the organic matter, organic matter in general and amino acids specifically could represent significant carbon and energy sources for archaea and bacteria in this hydrothermal system. The clear delineation of three different groups of sites with distinct AA composition and concentrations indicates that the different geological settings within this system have the potential for harboring different microbial communities.

Spatial and seasonal distribution of the ichthyofauna of Lake Nokoué, Bénin, west Africa

The fish biodiversity of Lake Nokoué, a lagoon in Bénin, was monitored for one year from August 2000 to July 2001 by means of samples from the artisanal fishery collected once a month at three stations. A total of 5 933 fish weighing 95 322g (mean individual weight 16.0g) belonging to 51 species, 47 genera and 34 families were sampled. An abundance of juveniles was observed, confirming the importance of the lake as nursery grounds, rich in exploitable habitats like other tropical estuaries and lagoons. The fish fauna comprised three main components: i) an estuarine component (strict, freshwater and marine origins) which is the basis of the lagoon fauna community and which is stable in space and time; ii) a marine component containing fishes which appeared in the lagoon during the dry season where the salinity remains high (>20‰) and iii) a freshwater component with fishes coming into the lagoon from the river during the flood period. The magnitude of the spatial and seasonal fluctuations of the last two components varies depending on the area: marine (Zogbo), freshwater (Vêki) or intermediate (Ganvié). The global species richness and the relative abundances of fish vary between stations and from month to month. November, with 20 species on average, and January, with 6 species on average, are significantly different as regards species richness.

Freshwater Ecosystems—Structure and Response

Before it is possible to predict the impact of human activities on the natural environment it is necessary to understand the forces that drive and, therefore, control that environment. This paper is concerned with the freshwater component of the aquatic environment. The driving forces involved (some of which are under man's control) can be divided into the physical and the chemical, but the response is, almost entirely, biological. Although most impacts of the food processing industry might be perceived to be on running waters, this is not always the case, but we can apply the same basic rules to both static and running waters. The physical forces that determine how a lake functions are as follows. In early spring, in the temperate zone, the temperature of the surface water in lakes rises and the sunlight input increases. This results in stratification of the water body. The cooler, deeper water is separated, physically, by gravity. This isolated water plays a very different role in the function of the lake and is analogous to how a river works. Man's activities drive these systems by our input of inorganic and organic substances. The inorganic inputs, particularly of phosphorous, stimulate undesirable algal growths, some of which may produce particularly dangerous toxins. We must now accept that climate change, driven by man, will exacerbate these problems. Organic inputs from the food industry, i.e., carbohydrates, lipids, and proteins, will all impact lakes and rivers by increasing the biological oxygen demand. The worst case scenario is total loss of oxygen from the water as a result of microbial activity. Lipids create the greatest oxygen demand but carbohydrates (more easily biodegradable) also result in unsightly “sewage fungus.” Protein waste can be degraded to produce ammonia and sulfide, both of which produce toxicity problems. Bioremediation processes, particularly phytoremediation, can alleviate these problems in a cost-effective manner and this paper will address these options.

Helminth communities in eels Anguilla anguilla from Adriatic coastal lagoons in Italy.

The composition and diversity of the total and intestinal component and infra-communities were determined in eels Anguilla anguilla from three shallow lagoons on the Adriatic coast of Italy to determine whether the helminth communities would differ in composition and structure from those in eels from lagoons on the Tyrrhenian coast. The lagoons differed in respect of their management regimes and the extent of freshwater influx. Both freshwater and marine species of helminths were found in the eels in all three lagoons, but the freshwater component was richer in Valle Figheri. A suite of three digenean eel specialist species occurred in all three lagoons, of which any two members dominated each community. This conferred a high degree of similarity between the communities of the three lagoons. The same three species also dominated helminth communities in eels in lagoons along the Tyrrhenian coast of Italy, and compositional similarity levels were similar within and between western and eastern groups. Species richness was higher in the component communities of the eels of the Adriatic lagoons when compared to the Tyrrhenian ones, but diversity and dominance indices were of a similar order of magnitude and range. Intestinal helminth communities were richer and more diverse in two of the Adriatic lagoons because the proportion of eels with zero or one helminth species was, unusually, in the minority. It was nevertheless concluded that infracommunity structure was similar in eels from both western and eastern lagoons and that the hypothesis that it would differ in Adriatic lagoons could not be supported. The findings provide further evidence of the similarity in composition and structure of helminth communities in eels from coastal lagoons throughout Europe.

Humic matter and contaminants. General aspects and modeling metal ion binding

Abstract Humic substances are soil and fresh-water components that play an important role in the binding and transport of both organic and inorganic contaminants. Transport of the contaminants due to ground- and fresh-water dynamics is directly related to the risks associated with contaminations. The mobility of soluble humic substances is related to their interaction with soil mineral particles. Some key references for the binding of organic and inorganic contaminants and for the binding of humics to mineral particles are presented. Humic substances also play a role in the analysis of the contaminants in natural waters and with remediation of water or soil polluted with pesticides, heavy metal ions, and radionuclides. These aspects are illustrated with some examples. The problems that are encountered with the modeling of the binding of contaminants to humics and of heavy metal ions in particular are illustrated by considering the nonideal competitive adsorption model (NICA) extended with electrostatic interactions. The NICA-Donnan model gives quite good results for the description of metal ion binding, as is illustrated for metal ion binding to purified peat humic acid (PPHA). Finally, some remarks are made with respect to the use of the NICA-Donnan model in general purpose speciation programs and of simplified versions of the model for predictions under restricted environmental conditions.

The magnitude of river flow to the Arctic Ocean: dependence on contributing area

The export of freshwater from the Arctic Ocean (AO) is an important modifier of themohaline circulation in the North Atlantic and ultimately global climate. Arctic river discharge is known to be the most important source of freshwater to the AO but considerable variation about its magnitude exists in the literature. A reanalysis of all available data showed that the major source of variation is differences in the geographical definition of the receiving body. The contributing area to inflow relationship was also found to be remarkably linear for the major spatial definitions of the AO “catchment”. Precise catchment and receiving area boundaries of the AO need to be properly defined before freshwater components are calculated or compared.

Pathways and mean residence times of dissolved pollutants in the ocean derived from transient tracers and stable isotopes

During the past decades, a variety of transient tracers have been used to derive information on pathways and mean residence times of oceanic water masses. Here, we discuss how information obtained in such studies can be applied to studying the spreading of dissolved pollutants in the ocean. The discussion focuses on the transient tracers tritium/ 3He and the H 2 18O/H 2 16O ratio of water. These tracers are used in combination with CFCs and 14C in a case study of Arctic Ocean contaminant transport to: (1) separate the freshwater components contained in the near-surface waters; (2) infer mean pathways of freshwater and associated contaminants from the H 2 18O/H 2 16O distribution in the surface waters; and (3) determine mean residence times of the surface, intermediate, deep and bottom waters.