Brackish Water Region Research Articles

Molecular Identification of Two Strains of Third-Stage Larvae of Contracaecum rudolphii Sensu Lato (Nematoda: Anisakidae) From Fish in Poland

Contracaecum sp. larvae (L3) from fish were identified using nucleotide sequences of the internal transcribed spacers ITS-1 and ITS-2 of the ribosomal DNA. The nematode larvae originated from fish in a freshwater situation (crucian carp Carassius carassius, from Selment Wielki Lake in Mazury, northeastern Poland) and a brackish-water region (Caspian round goby Neogobius melanostomus from the Baltic Sea, Gdafisk Bay at the Polish coast). Two strains (Contracaecum rudolphii A and B) of Contracaecum rudolphii senso lato, a parasite common at the adult stage in fish-eating birds, were identified. In fish from the freshwater site, only the strain temporarily designated C. rudolphii B was identified; in the brackish-water region, both strains were found, suggesting that fish serve as paratenic host for both genotypes. Contracaecum rudolphii sensu lato has been recorded in several species of fish-eating birds in Poland, particularly in the great cormorant, Phalacrocorax carbo, in which the abundance is highest. The results, although based on a restricted number of larvae, suggest that the life cycles of both genotypes can be completed in the Polish region and that at least one of them, C. rudolphii B, can develop both in fresh and brackish water.

Habitat Segregation of a Functional Gene Encoding Nitrate Ammonification in Estuarine Sediments

Distribution and diversity of nrfA gene encoding dissimilatory nitrite reduction to ammonium (DNRA) in the sediments of the Colne River, North Essex, UK, were investigated. Sequencing cloned nrfA fragments amplified from environmental DNA enabled structure analysis of the bacterial community responsible for this pathway. The DNA was extracted from the sediment samples at different depths from the estuary ranging from freshwater to seawater regions, and amplified using specific PCR primer pairs targeting for the nrfA gene. Analysis of the nrfA clones showed two distinct clusters corresponding to their origins, namely, divided into the stable sites (marine and freshwater regions) and the unstable sites (brackish water region), where the tidal rise and fall constantly disturbs the environmental conditions. In addition, the nrfA clones from the deeper layer of the sediment formed a more homogenous community than those from the surface layer of the sediment. This may be due to more isolated and anaerobic conditions kept in the deeper sediment less influenced by the overlying water and other environmental factors. Most of the nrfA clones from the Colne estuarine sediments formed several distinct clusters including known nitrate ammonifiers such as Aeromonas, Shewanella, Desulfovibrio and Sulfurospillum. One of which was, however, related to Bacteroides but still quite divergent (∼70% identity) and the rest forming unknown clusters of supposedly uncultured members of bacteria. This is the first trial to describe the nrfA partial sequences derived from a natural environment, with reference to their habitat-specific community structure.

Economic characteristics of extensive shrimp farms in the Mekong delta

Extensive forms of shrimp aquaculture have become an important source of income for farm households in the brackish water region of the Mekong Delta, Vietnam. The economic and production characteristics of farms are discussed in this paper, based on a 1997 farm survey, with particular emphasis on shrimp farming practices. Two types of shrimp fanning practice were observed, one based on natural recruitment of seedstock with few supplementary inputs, and the other based on relatively high cash investments in Penaeus monodon seedstock and other inputs. Households practising monodon culture made significantly more income, but faced high risk associated with shrimp mortality. An investigation of the factors affecting monodon yields indicated that investment in higher quality inputs had a positive effect on yield and income. However, further research is needed on the extent to which management can reduce risk of shrimp mortality by investing in such premium quality inputs.

Non-native Species and Rates of Spread: Lessons from the Brackish Baltic Sea

The Baltic Sea, a semi-enclosed brackish water region, has been inoculated by non-indigenous species for centuries. Today, much of its biological diversity is of foreign origin (i.e. xenodiversity), intentionally or unintentionally moved by humans over ecological and geographical barriers. As many as 98 introduced species have been recorded in the Baltic Sea and Kattegat. The role and abundance of much of the unique native brackish water fauna of the Baltic Sea are threatened by these non-indigenous species. The rate of primary introductions into the Baltic has increased since the 1950s; the secondary rate of spread of non-indigenous species within the basin varies from 30–480 km/year. We review here the invasion histories of the brown alga Sargassum muticum (introduced in the early 1990s), the mud snail Potamopyrgus antipodarum (1887), the barnacle Balanus improvisus (1844), the polychaetes Marenzelleria viridis (1985) and Polydora redeki (1963), the cladoceran Cercopagis pengoi (1992) and the mysid shrimp Hemimysis anomala (1962).

The Ponto–Caspian Zoogeographic complex of Cyclopoida in the Caspian, Azov and Black Seas

Zoogeographical conclusions are drawn from several years of taxonomic study of the Cyclopoida of the Ponto–Caspian brackish water region. The total Ponto–Caspian complex of Cyclopoida comprises 19 species of which 7 species are endemics to the Caspian provinces and 9 species to the mixohaline waters of the Black and Azov Seas, while 3 species are common to both areas. Of these 19 species 11 are of marine origin. The remaining ones are of freshwater origin. It is shown for the first time that Cyclopoida of the Ponto–Caspian complex are also present in the Black and Azov Seas where they occur together at the same localities with representatives of this complex from other animal groups. As compared with these other groups Cyclopoida show a higher proportion of species endemism in the Black and Azov Seas. Even a case of generic endemism among Cyclopoida is reported for the first time for these seas.

ESTIMATION BY THE GROWTH STRIATIONS FOR GROWTH SPEED OF CORBICULA JAPONICA FROM LAKE OGAWARA

A new technique is developed for estimating the age of a Corbicula Japonica which is one of common aquatic products in brackish water regions in Japan. The basic idea is as follows: Because the number ofstriations between two annual rings are almost constant, the age can be approximately estimated by counting the number of striations on the shell instead of annual rings when annual rings are not clear. A laser telemeter is used for measuring the shape of shells with an accuracy of 1 μ m. All of the measurement processes are automated. As a result, the age and the growth rate of Corbicula Japonica can be easily estimated with a short time.

The ammonia-oxidizing nitrifying population of the River Elbe estuary

The ammonia-oxidizing bacterial population of the tidal River Elbe was analysed. In the freshwater section of the river, abundance was generally at a magnitude of 10 4 cells per g dry weight and 10 3 cells per ml in sediments and in water samples, respectively. In the brackish water region, counts decreased drastically with the increase in salinity caused by the low level of abundance of ammonia-oxidizers in the seawater. The contribution of attached ammonia-oxidizers to the total number ranged between 50 and approximately 100%, depending on the respective load with suspended particulate matter (SPM) of the water. The presence of seven distinct species of the genus Nitrosomonas was established by DNA hybridizations. Based on 16S rRNA gene partial sequence analyses, four groups, comprising phylogenetically closely related species, were defined. Dependence of ammonia oxidation on the NH 4Cl concentration, tolerance against increasing salinity and the possession of urease activity were found to be useful ecophysiological characteristics, being in accordance with phylogenetic relationships among the species.

The ammonia-oxidizing nitrifying population of the River Elbe estuary

The ammonia-oxidizing bacterial population of the tidal River Elbe was analysed. In the freshwater section of the river, abundance was generally at a magnitude of 104 cells per g dry weight and 103 cells per ml in sediments and in water samples, respectively. In the brackish water region, counts decreased drastically with the increase in salinity caused by the low level of abundance of ammonia-oxidizers in the seawater. The contribution of attached ammonia-oxidizers to the total number ranged between 50 and approximately 100%, depending on the respective load with suspended particulate matter (SPM) of the water. The presence of seven distinct species of the genus Nitrosomonas was established by DNA hybridizations. Based on 16S rRNA gene partial sequence analyses, four groups, comprising phylogenetically closely related species, were defined. Dependence of ammonia oxidation on the NH4Cl concentration, tolerance against increasing salinity and the possession of urease activity were found to be useful ecophysiological characteristics, being in accordance with phylogenetic relationships among the species.

Pathogenic vibrios and Food Sanitation of Marine Products.

Bacteria of the genus Vibrio are normal habitants in an aquatic environment such as river, estuarine, coastal and sea water, but include some species pathogenic for human. Currently 37 species are reported in the genus Vibrio, and 11 species in the genus Vibrio are recognized to be pathogenic for human. Of these pathogenic species, V. cholerae is well known as pathogen of epidemic cholera, and V. parahaemolyticus is the most important food poisoning bacterium in Japan. V. cholerae is serologically classified into two groups, V. cholerae Ol and non-Ol, namely NAG vibrio. V. cholerae Ol is an actual cholera vibrio causing epidemic cholera, characterized by severe watery diarrhea caused by cholera toxin. In the humen history, there were 7 worldwide cholera pandemics. On the other hand, some strains of non-Ol also cause diarrhea, but the symptoms are not so severe and not contagious. Therefore, non-Ol is defined as a food poisoning bacterium. In recent years, 40 to 60% of the food poisoning outbreaks are due to V. parahaemolyticus. V. mimicus and V. fluvialis are also recognized as food poisoning bacteria. In addition to these diarrhogenic vibrios, significance of V. vulnificus as a pathogen of opportunistic infection is suggested recently, because the vibrio occasionally causes fatal septicemia to aged patients having underlying disease, such as hepatic dysfunction. Sea foods in markets are frequently contaminated with V. parahaemolyticus or V. vulnificus in summer season, and V. cholerae non-Ol and V. mimicus are universal inhabitants in fresh or brackish water regions. Thus, the pathogenic vibrios are important bacteria in food sanitation control.

The Geonemertes problem (Nemertea)

A new genus of monostiliferous hoplonemerteans, Pantinonemertes gen. nov., provides evidence for the separate evolution of terrestrial nemerteans. The genus is established for two new species found in Australia, P. enalios sp. nov., an intertidal form, and P. winsori sp. nov., which lives in fallen timber in the supralittoral brackish water regions of mangrove swamps. One only of the known species of land nemerteans, Geonemertes agricola from Bermuda, closely resembles these two species morphologically and is transferred to the new genus as Pantinonemertes agricola.A re‐examination of all the known species of Geonemertes has shown that two major groups can be distinguished on the basis of morphological characters. In one group the rhynchocoel musculature is in two distinct layers, a frontal organ is present, the mid‐dorsal blood vessel has a single vascular plug, and the flame cells are binucleate and reinforced with cuticular support bars. It comprises the genus Pantinonemertes gen, nov, and the Pelaensis or Indopacific group of terrestrial nemerteans, for which the generic name Geonemertes is retained. In the second major group the rhynchocoel musculature is composed of interwoven longitudinal and circular fibres, there is no frontal organ, the mid‐dorsal blood vessel bears two vascular plugs, and the flame cells are mononucleate and lack support bars. Five genera, three of which are new, are distinguished in this group. Australian species are united in the genus Argonemertes gen. nov., and New Zealand forms comprise the genus Antiponemertes gen. nov., while Acteonemertes bathamae from New Zealand and the Auckland and Ocean Islands remains in a separate genus. Geonemertes nightingaleensis is transferred to a new genus, Katechonemertes gen. nov., and for Geonemertes chalicophora a previously used generic name, Leptonemertes, is adopted.A key to the terrestrial, brackish‐water and marine nemertean species described in the present paper is provided.

Standing Crops of Marsh Vegetation of Two Tributaries of Chesapeake Bay

A comparative study of the standing crop of marsh vegetation was made of the Patuxent River and Parker Creek, two tributaries of Chesapeake Bay. The biomass of marsh vegetation in the tidal freshwater and brackish regions of the Patuxent was relatively uniform with regard to salinity, seasonally high concentrations of dissolved nitrogen, and phosphorus and nutrient gradient. Maximum values of biomass occurred in the tidal freshwater and slightly brackish water region of Parker Creek, a system whose nutrient concentrations approximated 20% of those of Patuxent River. Biomass values for the Patuxent River and Parker Creek averaged about 1417 and 895 g m−2 dry weight, respectively. Estimates of total annual marsh production based on the maximum standing crop was 27×103 and 519 metric tons, respectively, for the Patuxent River and Parker Creek.

The distribution of Chironomid larvae in relation to Chloride concentration in a brackish water region of the Netherlands

Drainage ditches are a familiar and common habitat in the Netherlands. Until recently however they have been the focus of few ecological studies. Extensive studies on Walcheren, a brackish water region of The Netherlands, have shown that chironomid larvae form a major component of the animal communities in the mud. The spatial distribution of some of these species can be correlated with the chloride concentration of the water. Biometric data are included for the speciesChironomus salinarius, C. halophilus andC. plumosus.

The Relation of Treatment and Ecological Effects in Brackish Water Regions

The Relation of Treatment and Ecological Effects in Brackish Water Regions

Food Habits and Seasonal Abundance of the American eel, Anguilla rostrata, from the Lower Chesapeake Bay

Food habits and seasonal abundance of the American eel, Anguilla rostrata (Lesueur), were studied from the brackish water regions of three Virginia rivers. Abundance in trawl surveys was related to water temperatures with fewer eels being caught during the colder months. Polychaetes, crustaceans and bivalves were the most important dietary items of A. rostrata in brackish water. There was much predation on the commercially important species Mya arenaria and Callinectes sapidus.

On the importance of marine meiofauna for benthos communities.

1. In sublittoral sediments of silty sand live about 55000-1300000 meiofauna animals, which is a minimum figure because methods are not absolutely efficient. 2. Meiofauna biomass ranges from 0.2 to 2.0 g wet weight in sublittoral silty sand, that is about 3% of macrofauna biomass. 3. A higher percentage of meiofauna biomass is recorded from brackish water regions, intertidal beaches and from the deep sea, where meiofauna and macrofauna biomass are of the same magnitude. 4. Oxygen consumption in meiofauna animals is between 200 and 2000, in small macrofauna between 200 and 500, and in larger macrofauna between 10 and 100 mm3 O2/h/g wet weight. 5. The assumption is forwarded that in general meiofauna has a metabolism five times more active than that of macrofauna. 6. Generation time in meiofauna lasts from a few days as was observed in cultures, to one or a few years, as was observed in natural populations. For a generalization the guess is forwarded that three generations per year would be an average meiofauna value. 7. Life cycle turnover rate as calculated from life cycle models of two nematodes is 2.2-3. Multiplied by three annual generations results in an average annual turnover rate of about 9 for meiobenthos, which is about five times more than that in macrobenthos. 8. If one compares meiobenthos and macrobenthos, meiobenthos importance in terms of food consumed and in terms of biomass provided for the food chain is 15% in a community like sublittoral silty sand, although meiobenthos in terms of standing stock is just 3% of macrobenthos.

A Survey of the Island Fisheries of the Territory of New Guinea and Papua

A survey of two weeks' duration was made of part of the territory of New Guinea and Papua to study the possibility of extending the freshwater and brackish water fisheries. The brackish water region possesses a higher productivity potential than inland waters, owing to the introduction of the normal nutrient components of sea water with the fertile sedimented mud from the rivers, together with organic matter from the rain forests. Ecologically, and in regard to type of vegetation found, the limited coastal flats, the river deltas, and the extensive mangrove swamps are Indonesian in character. The estuarine region has a fauna rich in density, there being numerous fish species and large populations of prawns, while shrimps and oysters are also plentiful. In the freshwater areas two types of river exist — one shallow, subject to flooding and shifting of sands, and few fish; the second deep, with fertile mud, and fairly productive of fish. The lowland lakes, with fertile colloidal mud, were not examined in detail, but should provide a considerable fishery potential. There is considerable scope for fish cultural operations, e.g. in constructed ponds. Before a sound extension of the fisheries can be planned it will be necessary to obtain adequate basic scientific knowledge of the density and composition of the flora and fauna, including the food of the fish stocks, and of the characteristics of the environment. I t appears that a fishery more than adequate to supply the protein requirements of the coastal population could therefore be developed, by relatitive simple means, in the brackish waters and in the great lowland rivers.