Brackish Water Lagoon Research Articles

Recent benthic foraminifera and their distribution between Tuticorin and Tiruchendur, Gulf of Mannar, south-east coast of India

Foraminifera have been successful inhabitants of every aquatic environment from deep oceans to brackish water lagoons, estuaries and even rarely in freshwater streams, lakes, etc. In order to know their distribution in different offshore habitats, the present study has been undertaken between Tuticorin and Tiruchendur, wherein 31 bottom sediment and water samples were collected. Benthic foraminiferal taxa belonging to four suborders (Textulariina, Miliolina, Lagenina and Rotaliina), 14 superfamilies, 25 families, 45 genera and 66 species have been identified; three planktonic species (suborder Globigerinina) have also been identified. An increase in total foraminiferal distribution with depth has been observed, except off Tiruchendur. Living/dead ratios range from 1.57% to 10.02%, indicating a low to moderate rate of sedimentation in this region. Off Punnaikayal and Tiruchendur, the rate of sedimentation is more at greater depths; at other stations, however, it is higher at relatively shallower depths. Based on this study, it is concluded that fluctuations in the distribution of foraminifera are mainly controlled by coastal morphology, wave dynamics, bathymetry and environmental parameters.

First recording of kinorhynchs from Java, with the description of a new brackish water species from a mangrove-fringed lagoon

A new species of Echinoderes, E. applicitus sp. nov., is described from a brackish water lagoon on the south coast of Central Java, Indonesia. The species is recognized by its complete lack of spines on segments 1–10, lateroventral tubules on segments 5 and 8, laterodorsal tubules on segment 10, and a mid- to subdorsal tergal protrusion of segment 10 that extends beyond the posterior margin of segment 11. The general reduction of spine size and numbers, the absence of lateral terminal accessory spines in females and the enlarged sieve plate suggest a close relationship with E. rex, E. coulli, E. maxwelli and E. teretis. The adaptation to a brackish, estuarine habitat with highly fluctuating salinities is also shared between the three latter species and E. applicitus sp. nov. The examined populations of the new species had a relatively high infection rate (10–15%) of epibiontic growth from at least three different prokaryotic or protist organisms. An infection rate of this magnitude has not previously been reported for kinorhynchs, and it may have a relationship to the brackish habitat.

Evaluation and integration of soil salinity and water data for improved land use of underproductive coastal area in Orissa

Coastal agriculture in Orissa is predominantly rainfed and hence vulnerable owing to uncertain distribution of rainfall over time. Lack of irrigation support and salt stress affect crop growth and reduce yield as well. Good quality aquifer and low-saline soil are available but vary spatially. Promoting potential use of spatially varied resources, precise assessment of soil and water quality at micro-level is therefore imperative. In this study the soil salt stress, availability and quality of underground aquifers at different sites were evaluated in the neighbourhood area of Chilika, the largest brackish water lagoon of Asia. Integrating soil salinity, soil moisture content, aquifer availability and quality, various farming strategies specific to different sites were developed. These could trigger 1.59 to 2 times more production from its present level in that area. Where there is a diverse occurrence of resources, a precise estimation of those resources' potentials thus provides keys to develop cost-effective options for improving production in an underproductive area. Copyright © 2010 John Wiley & Sons, Ltd. L'agriculture du littoral de l'Orissa est essentiellement pluviale et donc vulnérable en raison de la distribution temporelles incertaine des précipitations. Le manque d'irrigation et le stress dû au sel affectent la croissance des cultures et ainsi réduisent le rendement. Un aquifère de bonne qualité et des sols peu salins sont disponibles, mais varient dans l'espace. Il est donc impératif de promouvoir l'utilisation des ressources potentielles variables dans l'espace, l'évaluation précise des sols et de la qualité de l'eau à micro-échelle. Dans cette étude, la salinité du sol, la disponibilité et la qualité des aquifères souterrains dans les différents sites ont été évalués dans la zone de Chilika, la plus grande lagune d'eau saumâtre de l'Asie. En intégrant la salinité du sol, la teneur en humidité des sols, la disponibilité et la qualité de l'aquifère, des stratégies agricoles spécifiques aux différents sites ont été développées. Celles-ci pourraient déclencher dans cette zone 1,59 à 2 fois plus de production par rapport au niveau actuel. Pour diverses occurrences de ressources, l'estimation précise des ressources potentielles fournit ainsi des clés pour développer des options efficaces pour améliorer la production des zones les moins productives. Copyright © 2010 John Wiley & Sons, Ltd.

Life history of Ammonia "beccarii" forma 1 on hard substrate in the Ohashi River, southwestern Japan

We investigated the life history of Ammonia forma 1 (A. beccarii forma 1 sensu Matoba) inhabiting a bridge pier and surface sediments in the Ohashi River (tidal river between two brackish-water lagoons) in southwestern Japan based on seasonal changes in the standing crop and size distribution. This species commonly occupies shallow infaunal habitats but sometimes is found in attached macrobenthos on hard substrates. Attached macrobenthos at 1 m and 2 m water depth on a concrete bridge pier and surface sediments on the river floor at two sites were studied. Seasonal changes in both the standing crop and size distribution of A. forma 1 were generally different between the bridge pier and surface sediments. There was no statistical correlation between the standing crop of bridge pier A. forma 1 and the abundance of attached macrobenthos on the bridge pier. This finding suggests that bridge pier foraminifera do not simply depend on the abundance of attached macrobenthos on a hard substrate. The presence of small bridge pier individuals indicated that major reproduction occurred in spring and fall during the study period. A. forma 1 from the bridge pier can likely breed in the macrobenthos colonies on hard substrates (i.e., in-situ) and hence recover, even when it has been diminished by physical disturbance (e.g., freshet). Thus, these characteristics of A. forma 1 on the bridge pier likely enable the population to persist in an ephemeral habitat within macrobenthos colonies and an unstable brackish-water environment.

Coastal Vulnerability Assessment for Orissa State, East Coast of India

Coastal areas of Orissa State in the northeastern part of the Indian peninsula are potentially vulnerable to accelerated erosion hazard. Along the 480-km coastline, most of the coastal areas, including tourist resorts, hotels, fishing villages, and towns, are already threatened by recurring storm flood events and severe coastal erosion. The coastal habitats, namely the largest rookeries in the world for olive Ridley sea turtles (the extensive sandy beaches of Gahirmatha and Rushikulya), Asia's largest brackish water lagoon (the “Chilika”), extensive mangrove cover of Bhitarkanika (the wildlife sanctuary), the estuarine systems, and deltaic plains are no exception. .The present study therefore is an attempt to develop a coastal vulnerability index (CVI) for the maritime state of Orissa using eight relative risk variables. Most of these parameters are dynamic in nature and require a large amount of data from different sources. In some cases, the base data is from remote sensing satellites; for others it is either from long-term in situ measurements or from numerical models. Zones of vulnerability to coastal natural hazards of different magnitude (high, medium, and low) are identified and shown on a map. In earlier studies, tidal range was assumed to include both permanent and episodic inundation hazards. However, the mean of the long-term tidal records tends to dampen the effect of episodic inundation hazards such as tsunamis. For this reason, in the present study, tsunami run-up has been considered as an additional physical process parameter to calculate the CVI. Coastal regional elevation has also been considered as an additional important variable. This is the first such study that has been undertaken for a part of the Indian coastline. The map prepared for the Orissa coast under this study can be used by the state and district administration involved in the disaster mitigation and management plan.

Modelling the effects of variable salinity on the temporal distribution of plankton in shallow coastal lagoons

In shallow lagoons, there is a much greater ecological diversity than fully marine water bodies and communities comprise of representatives from both freshwaters and coastal sea. In the present study, an attempt has been made, through mathematical modelling, to study the effect of changing salinity on freshwater and marine plankton. The model proposed here is a five-compartment (Nutrient ( N), Freshwater phytoplankton ( P), Marine phytoplankton ( Q), Zooplankton ( Z) and Detritus ( D)) ecological model. The unique feature of the model is its ability to simulate plankton dynamics, as a response to salinity variations, with freshwater and marine species of phytoplankton represented separately. Numerical experiments and sensitivity analysis show that changes in salinity levels, nutrients and grazing are the controlling factors. For the case of intermediate salinity (17 psu approx.), the nutrient availability and palatability by zooplankton play a significant role. It is in this case, the two species are found to coexist. As a case study, the model is applied to Chilika Lagoon (19°28′N–19°54′N and 85°06′E–85°36′E), the largest brackish water lagoon on the east coast of India which has distinct and variable characteristics. The model is able to reproduce most of the significant characteristics of the phytoplankton distribution in Chilika, viz., bimodal oscillations, major plankton peaks and increased productivity after the salinity level was increased due to the opening of a new mouth connecting Bay of Bengal.

Shewanella chilikensis sp. nov., a moderately alkaliphilic gammaproteobacterium isolated from a lagoon

A Gram-negative, motile, rod-shaped, facultatively anaerobic bacterium was isolated from sediment of Chilika Lagoon, a brackish water lagoon in India. The strain, designated JC5(T), was able to grow in the presence of 0-8.0 % NaCl and at pH 7.0-10.0. The isolate was positive for oxidase and catalase and exhibited alpha-haemolysis. The major fatty acids were iso-C(15 : 0) (18.3 %), C(16 : 0) (11.3 %), C(17 : 1)omega8c (13.1 %) and a summed feature, C(16 : 1)omega7c and/or C(16 : 1)omega6c (15.1 %). The genomic DNA G+C content was 54.6 mol%. A phylogenetic tree based on the 16S rRNA gene sequences showed that strain JC5(T) forms a lineage within the genus Shewanella and is closely related to Shewanella haliotis DW01(T) (98.0 %), Shewanella algae ATCC 51192(T) (97.6 %) and Shewanella marina C4(T) (95.8 %). Further, genomic DNA-DNA hybridization of strain JC5(T) with S. haliotis DW01(T) and S. algae ATCC 51192(T) showed relatedness of only 42 and 23 %, respectively. On the basis of phenotypic and molecular genetic evidence, strain JC5(T) represents a novel species of the genus Shewanella, for which the name Shewanella chilikensis sp. nov. is proposed. The type strain is JC5(T) (=CCUG 57101(T) =NBRC 105217(T) =KCTC 22540(T)).

Metazoan fish parasites of Segara Anakan Lagoon, Indonesia, and their potential use as biological indicators

The present study reports metazoan fish parasites from Segara Anakan, a brackish water lagoon located at the southern Java coast, Indonesia. Seven economically important marine fish species (Mugil cephalus, Siganus javus, Scatophagus argus, Caranx sexfasciatus, Lutjanus johnii, Eleutheronematetradactylum and Johnius coitor) were examined at two different sampling sites within the lagoon for the occurrence of metazoan parasites. A diverse parasite fauna was found, consisting of 43 species/taxa. Ectoparasites (31) were more abundant than endoparasites (12). The fish species J. coitor, M. cephalus and S. argus harboured the most diverse metazoan parasite fauna with 11, 13, and 16 different parasite species, respectively. Prevalence and intensity of infection for each parasite species/taxon is given, including short descriptions for rapid diagnosis. For the first time, we discuss the utilisation of the sampled fish parasites as biological indicator organisms for fish and environmental health within this tropical mangrove ecosystem. Ecto- versus endoparasite ratio and endoparasite diversity are suitable tools to describe the environmental health status at a tropical brackish water locality, and might be applied also for other tropical and possibly non-tropical marine ecosystems.

Spatial Variation in Hydrological Characteristics of Chilika–a Coastal Lagoon of India

The distribution of hydrological characteristics like temperature, pH, salinity, conductivity, DO, BOD, alkalinity, nutrients (NO 2 -N, NO 3 -N, PO 4 -P, SiO 4 -Si) along with depth, transparency and turbidity were studied in Chilika, the largest brackish water lagoon in Asia. The results exhibited pronounced spatial variation and distribution pattern, indicating large variations, possibly due to seasonal changes. The photosynthesis of weeds caused the lake water slightly alkaline due to uptake of CO 2 from water column and on the other hand, the formation of humic acid because of decaying of weeds in northern sector lowers the pH of the lake water. The low salinity in northern sector related to influx of more floodwater, which was not very much affected in southern sector. Addition and removal of fresh water, seawater intrusion and mixing bring out the change in salinity of the lagoon. The low DO and high BOD values were associated with the area near to large fishing jetties, where organic decomposition was more. Nitrite exhibited higher concentrations during May due to its release into the water column from the decomposed freshwater weeds. High nitrate during July and August were related to agricultural runoff through floodwater. Silicate concentration showed a well-defined pattern with higher during monsoon months, which was slightly removed at high salinities areas.

Spatial variation in hydrological characteristics of Chilika – A coastal lagoon of India

The distribution of hydrological characteristics like temperature, pH, salinity, conductivity, DO, BOD, alkalinity, nutrients (NO 2 -N, NO 3 -N, PO 4 -P, SiO 4 -Si) along with depth, transparency and turbidity were studied in Chilika, the largest brackish water lagoon in Asia. The results exhibited pronounced spatial variation and distribution pattern, indicating large variations, possibly due to seasonal changes. The photosynthesis of weeds caused the lake water slightly alkaline due to uptake of CO 2 from water column and on the other hand, the formation of humic acid because of decaying of weeds in northern sector lowers the pH of the lake water. The low salinity in northern sector related to influx of more floodwater, which was not very much affected in southern sector. Addition and removal of fresh water, seawater intrusion and mixing bring out the change in salinity of the lagoon. The low DO and high BOD values were associated with the area near to large fishing jetties, where organic decomposition was more. Nitrite exhibited higher concentrations during May due to its release into the water column from the decomposed freshwater weeds. High nitrate during July and August were related to agricultural runoff through floodwater. Silicate concentration showed a well-defined pattern with higher during monsoon months, which was slightly removed at high salinities areas.

Long-term stability of the seasonal succession of different zooplankton species in a brackish water lagoon (southern Baltic Sea)

Long-term zooplankton monitoring data of a shallow brackish water lagoon (southern Baltic Sea) were analysed regarding the stability of the seasonal development of single species or genera. Median values and the interquartile ranges of normalised monthly mean densities of the species and the frequency of their occurrence were used to characterise the species. Correlations of cumulated sums (CUSUM) of the yearly time series were used to point out the number of significant correlations as a measure of the stability of the yearly development patterns. A very stable yearly succession pattern of the zooplankton species over the whole investigation period was found. Thereby, the copepod Eurytemora affinis, rotifers with a development peak in summer and the larvae of the polychaete Marenzelleria neglecta which were found regularly in the late autumn were characterised by a high number of significant correlations (67.5–81.8%) between the years. This indicates relative stable yearly development patterns for this species. In contrast, the copepod Acartia tonsa and rotifers of the genus Synchaeta showed a higher inter-annual variability marked by a lower number of significant correlations between the years (45.9% and 52.4%). The result of a canonical correspondence analysis which showed associations between species and abiotic parameters fits very well with the seasonality of every single species. Nevertheless, the very stable temporal change of dominance between E. affinis and K. cochlearis f. tecta at the end of May cannot be directly explained by changes of abiotic parameters because these parameters exhibit a higher temporal variability.

Water quality and heavy metal monitoring in water and sediment samples of the Küçükçekmece Lagoon, Turkey (2002–2003)

Physical and chemical parameters have been analyzed in water samples from a brackish water lagoon, Küçükçekmece, located on the western outskirts of Istanbul. Samples were collected every two months for a year from nine sampling stations. Of the parameters measured, temperature, pH, salinity, nitrate and phosphate showed changes when compared with the previously published data. The lagoon was found eutrophic as it was reported previously. Sulphate and COD levels were higher when compared with the standards established by the Turkish Water Pollution and Control Regulation. Additionally, concentrations of heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn) in water and bottom sediments were measured and compared with the standards established by the Turkish Water Pollution and Control Regulation and with the previously published data. The results were analysed statistically with respect to location and any relationships between the concentration of the elements in corresponding water and sediment samples were examined. Principal Component Analysis of water samples allowed us to discriminate three areas affected mainly by heavy metal contamination, possibly due to industrial, commercial and/or urban activities. Generally, the concentrations of the heavy metals were higher at stations near the three estuaries, suggesting a direct influence of the three creeks on the pollution of the Küçükçekmece Lagoon. Although elevated levels of Cd were recorded in several water samples, it was not detected in sediment. On the other hand, a particularly high level of Cr pollution was recorded most of the water and sediment samples.

Mathematical modelling of the seasonal variability of plankton in a shallow lagoon

The quality of coastal waters can be markedly influenced by the growth and distribution of phytoplankton. In this study, a non-linear mathematical model is used to explain the seasonal variability of plankton in shallow coastal lagoons. A local stability analysis for dynamical systems is undertaken in order to estimate the range of values of model parameters. Numerical experiments and sensitivity tests with different parameters show that of the thirteen parameters in the model, the main parameter affecting the productivity is the growth rate of the phytoplankton, which depends on light and nutrients. The time of maximum planktonic growth, in particular, is mostly dependent upon the parameter values within the growth rate term. As a case study, the model is then applied to Chilika Lagoon (19 ∘28′N–19 ∘54′N and 85 ∘06′E–85 ∘36′E), the largest brackish water lagoon with estuarine character on the east coast of India. Interest in detailed analysis of the ecology of the lagoon and the various factors affecting it is due to the opening of the new mouth on 23 September 2000 to resolve the threat to its environment from various factors — eutrophication, weed proliferation, siltation, industrial pollution and depletion of bioresources. The model is tested for different sectors of the lagoon which have distinct characteristics in terms of depth, light penetration, nutrients and hence planktonic growth. A fine-tuning of the model parameters, with the help of the stability analysis discussed for a general model, was performed in order to validate the model results with the data available for the lagoon. Even in its simplest form, the model is able to reproduce most of the significant characteristics of the planktonic distribution in the lagoon — the bimodal oscillations, and major plankton peaks.

Lack of temporal variability in the benthos of a coastal brackish water lagoon in Greece

The benthic fauna was studied in the small, brackish water Mazoma Lagoon in the Amvrakikos bay.Benthic samples were collected at 10 stations at bimonthly intervals over a period of a year. Temperature, salinity, dissolved oxygen and sediment organic carbon were also measured at the same time. The environmental parameters showed the expected seasonal variability but the benthic community, the structure of which was only related to plant biomass, did not. This lack of seasonality is attributed to the continuous reproduction of some abundant species and to species interactions.

Thegrowth of the bivalve Abra segmentum (Recluz, 1843) in two Mediterranean lagoons

1 - The growth of Abra segmentum was studied for nearly one year in two Mediterranean lagoons with different degrees of communication with the sea. 2 - Tsopeli, situated in Amvrakikos Gulf (Ionian Sea), is a brackish-water lagoon, with restricted water circulation, relatively isolated from the open sea. Vivari is situated in Argolikos Gulf (Aegean Sea), and has better communication with the sea. Both lagoons are shallow with muddy bottom and both are used for the extensive culture of fish. 3 - Differences in the populations of A. segmentum were found regarding intensity of recruitment and growth in the two lagoons: recruitment was higher and survival lower in Vivari, while growth was better in Tsopeli. 4 - Length frequency histograms showed that larger body-size classes prevailed in Tsopeli, as opposed to Vivari where smaller individuals dominated. Mean individual size of A. segmentum was higher in Tsopeli throughout the year. 5 - Predation may be important in structuring the populations, however, comparison with findings in the literature suggest that the degree of communication with the sea is a more important factor controlling growth of A. segmentum.

Numerical Simulation of Circulation and Salinity Structure in Chilika Lagoon

Chilika Lagoon (19°28′–19°54′N, 85°06′–85°36′E), on the Orissa coast, India, is one of the world's unique ecospheres. It is the largest brackish water lagoon with estuarine character. Because of its rich biodiversity and socioeconomic importance, it was designated as a “Ramsar site”—a wetland of international importance—in 1981. Interest in detailed analysis of the circulation, biotic, and abiotic factors affecting the lagoon and its limnology is a result of the opening of the new mouth on 23 September 2000 to resolve the threat to its environment from various factors—eutrophication, weed proliferation, siltation, industrial pollution, and depletion of bioresources. This paper describes the development of a two-dimensional depth-averaged hydrodynamic model for Chilika Lagoon and the resulting simulation of currents and salinity corresponding to (i) the Southwest and Northeast monsoon seasons and (ii) pre- and post–mouth-opening conditions. Numerical experiments are performed to understand the different factors—wind, tides and freshwater influx—and their independent and collective roles. Comparison of results obtained with one or both of the openings is made to quantify and validate the changing salinity pattern, which has improved the productivity of the lagoon. Our study shows the salinity levels to be much lower during the southwest monsoon compared to the northeast monsoon, which is validated by observations. The decrease in salinity is attributed to more freshwater influx during the southwest monsoon. There is a significant increase (14%–66%, depending on the sector) in salinity after opening of the new mouth, the maximum change being observed in the channel that connects the lagoon to the sea. The constriction in the lagoon that blocks the tidal effects entering the lagoon is found to be responsible for maintaining the main body of the lagoon with low salinity. The dynamic model will be an important input for our on going work in seasonal study of the ecology of Chilika Lagoon.

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.

Study of Geochemical Association of Some Trace Metals in the Sediments of Chilika Lake: A Multivariate Statistical Approach

In order to establish the natural processes and geochemical factors responsible for enrichment of trace metal ions (Cu, Co, Ni, Zn and Cr) with respect to textural parameters (sand, silt and clay weight percentages) along with depth, multivariate statistical approach has been carried out for sediments in different water zones of Chilika lake, the largest brackish water lagoon in Asia. The rotated varimax factor results reveal that Cobalt enrichment is controlled by both textural parameters as well as adsorption mechanism. In fresh and saline water region, textural parameters and in mixed water, adsorption phenomenon predominates. Zn in fresh water is related to clay, whereas it is in adsorbed state in mixed water. Cu in fresh water sediments is in absorbed state and in mixed water it is related to depth and Co concentration. Cr does not show any specific association in fresh water, but in both mixed and saline water it is associated with clay minerals. Although both textural parameters and adsorption mechanism play an important role for the enrichment of trace metal ions in these lagoonal sediments, their relative importance varies with specific metal ions as well as the water quality. Sequential extraction technique was used to characterize the various forms of metals in the < 63 micro size sediments of Chilika lake. The concentrations determined indicated selective accumulation of the various metals in the different phases with spatial variability in different water zones. Slightly higher availability of Co and Zn near Balugaon township in exchangeable phase may be related to anthropogenic activities. Among the non-lithogenous (NL) phases, reducible phase associated with higher concentration of Ni, Cu and Cr. Organic bound Zn and Co contributed highest percentages among NL fractions. Residual fraction contributed more than 50% in most of the cases, reflected the predominance of physical weathering, high erosion rate along the drainage basin.

Luminescence dating of the barrier spit at Chilika lake, Orissa, India

Optically stimulated luminescence dating has been used to investigate the chronological development of the outer barrier spit forming Chilika Lake (Orissa, India), the largest brackish-water lagoon in Asia. Sixteen samples were examined, and these yielded equivalent doses of between 153 +/- 3 mGy and 2.23 +/- 0.07 Gy, corresponding to ages from approximately 40 y at the top of the spit to approximately 300 y at the bottom. The youngest ages are consistent with the age of the overlying vegetation, and modern material taken from the sub-tidal beach gave a dose of 4 +/- 2 mGy (corresponding to an age of 0.7 +/- 0.4 y), confirming that any previous potential luminescence signal in the source sediment is completely set to zero before incorporation into the spit. A clearly defined period of >2.5 m of barrier construction approximately 40 y ago is identified; prior to that the deposition rate was relatively constant for approximately 300 y.

A brackishwater isolate of Pseudomonas PS-102, a potential antagonistic bacterium against pathogenic vibrios in penaeid and non-penaeid rearing systems

A Pseudomonas sp PS-102 recovered from Muttukkadu brackish water lagoon, situated south of Chennai, showed significant activity against a number of shrimp pathogenic vibrios. Out of the 112 isolates of bacterial pathogens comprising Vibrio harveyi, V. vulnificus, V. parahaemolyticus, V. alginolyticus, V. fluvialis, and Aeromonas spp, 73% were inhibited in vitro by the cell-free culture supernatant of Pseudomonas sp PS-102 isolate. The organism produced yellowish fluorescent pigment on King's B medium, hydrolysed starch and protein, and produced 36.4% siderophore units by CAS assay and 32 μM of catechol siderophores as estimated by Arnow's assay. The PS-102 isolate showed wide ranging environmental tolerance with, temperatures from 25 to 40 °C, pH from 6 to 8, salinity from 0 to 36 ppt, while the antagonistic activity peaked in cultures grown at 30 °C, pH 8.0 and at 5 ppt saline conditions. The antagonistic activity of the culture supernatant was evident even at 30% v / v dilution against V. harveyi. The preliminary studies on the nature of the antibacterial action indicated that the antagonistic principle as heat stable and resistant to proteolytic, lipolytic and amylolytic enzymes. Pseudomonas sp PS 102 was found to be safe to shrimp when PL-9 stage were challenged at 10 7 CFU ml − 1 and by intramuscular injection into of ∼5 g sub-adults shrimp at 10 5 to 10 8 CFU. Further, its safety in a mammalian system, tested by its pathogenicity to mice, was also determined and its LD 50 to BALB/c mice was found to be 10 9 CFU. The results of this study indicated that the organism Pseudomonas sp PS 102 could be employed as a potential probiont in shrimp and prawn aquaculture systems for management and control of bacterial infections.