Time filter

Source Type

Jayasinghe R.P.P.K.,National Aquatic Resources Research and Development Agency | Jayasinghe R.P.P.K.,University of Cádiz | Amarasinghe U.S.,University of Kelaniya | Newton A.,University of Algarve
Marine Environmental Research | Year: 2015

European marine waters include four regional seas that provide valuable ecosystem services to humans, including fish and other seafood. However, these marine environments are threatened by pressures from multiple anthropogenic activities and climate change. The European Marine Strategy Framework Directive (MSFD) was adopted in 2008 to achieve good environmental status (GEnS) in European Seas by year 2020, using an Ecosystem Approach. GEnS is to be assessed using 11 descriptors and up to 56 indicators. In the present analysis two descriptors namely "commercially exploited fish and shellfish populations" and "food webs" were used to evaluate the status of subareas of FAO 27 area. Data on life history parameters, trophic levels and fisheries related data of cod, haddock, saithe, herring, plaice, whiting, hake and sprat were obtained from the FishBase online database and advisory reports of International Council for the Exploration of the Sea (ICES). Subareas inhabited by r and K strategists were identified using interrelationships of life history parameters of commercially important fish stocks. Mean trophic level (MTL) of fish community each subarea was calculated and subareas with species of high and low trophic level were identified. The Fish in Balance (FiB) index was computed for each subarea and recent trends of FiB indices were analysed. The overall environmental status of each subarea was evaluated considering life history trends, MTL and FiB Index. The analysis showed that subareas I, II, V, VIII and IX were assessed as "good" whereas subareas III, IV, VI and VII were assessed as "poor". The subareas assessed as "good" were subject to lower environmental pressures, (less fishing pressure, less eutrophication and more water circulation), while the areas with "poor" environment experienced excessive fishing pressure, eutrophication and disturbed seabed. The evaluation was based on two qualitative descriptors ("commercially exploited fish and shellfish populations" and "food webs") is therefore more robust. © 2015 The Authors.


Lozovatsky I.,University of Notre Dame | Lee J.-H.,Korea Advanced Institute of Science and Technology | Fernando H.J.S.,University of Notre Dame | Kang S.K.,Korea Advanced Institute of Science and Technology | Jinadasa S.U.P.,National Aquatic Resources Research and Development Agency
Journal of Geophysical Research C: Oceans | Year: 2015

A series of 134 microstructure profiles were taken in the central East China Sea from a drifting ship, covering more than 12 miles over the sloping bottom. The water depth z varied in the range 52-62 m; the tidal elevation of semidiurnal component was ±1 m. Prior to the onset of 25 h drift, a hydrographic section consisting of 9 stations, 15 miles apart, was taken in the area. A shallow mixed surface layer (SL) underlain by a diurnal pycnocline (z < 13 m), a sharp thermohalocline (13 < z < 30 m), and about 20 m tall bottom boundary layer (BBL) were the main features of summertime stratification. The splitting of upper pycnocline by a warmer, saltier intrusion led to the generation of turbulent patches at the lower, but not at the upper, density interface of this water body, suggesting asymmetry of mixing across the intrusion. In a limited range of the normalized squared buoyancy frequency, 2


Lee C.M.,University of Washington | Jinadasa S.U.P.,National Aquatic Resources Research and Development Agency | Anutaliya A.,University of California at San Diego | Centurioni L.R.,University of California at San Diego | And 6 more authors.
Oceanography | Year: 2016

The region surrounding Sri Lanka modulates monsoon-driven exchange between the Bay of Bengal and the Arabian Sea. Here, local circulation impacts the pathways followed by the boundary currents that drive exchange, thereby modulating mixing and water mass transformation. From 2013 to 2016, an international partnership conducted sustained measurements around the periphery of Sri Lanka, with the goal of understanding how circulation and mixing in this critical region modulate exchange between the Bay of Bengal and the Arabian Sea. Observations from satellite remote sensing, surface drifters, gliders, current meter moorings, and Pressure Inverted Echo Sounders capture seasonally reversing monsoon currents off the southern tip of Sri Lanka, trace the wintertime freshwater export pathway of the East India Coastal Current, and document the deflection of currents running along the east coast of Sri Lanka by cyclonic and anticyclonic eddies. Measurements also reveal energetic interleaving, indicative of mixing and stirring associated with these flows. Circulation inferred from satellite remote sensing and drifter tracks sometimes differs from that indicated by in situ sections, pointing to the need for observing systems that employ complementary approaches toward understanding this region. © 2016 by The Oceanography Society. All rights reserved.


Wijesekera H.W.,U.S. Navy | Teague W.J.,U.S. Navy | Jarosz E.,U.S. Navy | Wang D.W.,U.S. Navy | And 7 more authors.
Oceanography | Year: 2016

Long-term time series of velocity, hydrographic, and turbulence fields were collected from a six-element subsurface mooring array in the southern Bay of Bengal. The moorings, deployed in December 2013 and recovered in August 2015, were entangled with commercial fishing nets and lines, while top subsurface buoys ended up being serendipitously closer to the surface than planned. In spite of these unexpected events, almost all the sensors and data were recovered. The moorings provided currents between 6 m and 500 m depths from acoustic Doppler current profilers, supplemented by hydrographic data and turbulent dissipation rates at selected depths. The observations captured the summer and winter monsoon currents, eddies, and intraseasonal oscillations. Near-surface currents as large as 1.75 m s–1 were observed in July 2014. Currents stronger than 0.5 m s–1 were confined to the upper 200 m. Observations of currents, temperature, and sea surface height (SSH) fields revealed eddylike features with positive and negative SSH anomalies (~20 cm) moving westward at speeds of about 0.1 m s–1. Intraseasonal oscillations with periods of 30 to 90 days were strongest near the surface. For the duration of the deployment, root-mean-square velocity fluctuations were about 0.1 m s–1 near the surface but decayed with depth and became nearly uniform (~0.03–0.06 m s–1) below 100 m. © 2016 by The Oceanography Society. All rights reserved.


Jinadasa S.U.P.,National Aquatic Resources Research and Development Agency | Lozovatsky I.,University of Notre Dame | Planella-Morato J.,University of Notre Dame | Planella-Morato J.,University of Girona | And 5 more authors.
Oceanography | Year: 2016

As a part of the US Air-Sea Interactions Regional Initiative, the first extensive set of turbulent kinetic energy dissipation rate (ε) measurements from microstructure profilers were obtained in the Bay of Bengal (BoB) and around Sri Lanka during 2013–2015. The observations span almost 1,200 km meridionally, and capture the dynamics associated with a variety of mesoscale and submesoscale features. High freshwater input in the northern part of the basin leads to regions of intense near-surface stratification, which become weaker moving south. The thin layers trap mechanical energy input from the atmosphere, often confining turbulence to the surface boundary layer. These thin layers can form shallow fronts, which at times resemble turbulent gravity currents (Sarkar et al., 2016, in this issue), and are associated with high levels of mixing. Away from the local frontal zones, turbulence in the surface low-salinity layer appears to be decoupled from the underlying pycnocline, where turbulence occurs only in rare and sporadic breaking events. A striking feature common to all of the data acquired is a dearth of turbulent mixing at depth, a condition that appears to be pervasive throughout the basin except during the passage of tropical storms. It is likely that the strong near-surface stratification effectively isolates the deeper water column from mechanical penetration of atmospheric energy. © 2016 by The Oceanography Society. All rights reserved.


Jinadasa S.U.P.,National Aquatic Resources Research and Development Agency | Lozovatsky I.D.,University of Notre Dame | Fernando H.J.S.,University of Notre Dame
Physica Scripta | Year: 2013

The intermittency correction factor μc for the Obukhov-Corrsin ' - 5/3' inertial-convective subrange spectral law is estimated using conductivity (temperature) fluctuation measurements conducted within the microstructure patches of oceanic pycnocline in Monterey Bay. The value of μc was found to be in the range of 0.46-0.51, depending on the accuracy of calculation, which is applicable to stratified, low-Reynolds-number oceanic turbulence. The intermittency factor μM c for mesoscale (up to 1 km) lateral variations of scalar dissipation is estimated as 0.43 ± 0.02. The breakdown mechanisms of small-scale locally isotropic and mesoscale non-isotropic (lateral) turbulent temperature fluctuations in oceanic turbulence are discussed in the light of the above observations. © 2013 The Royal Swedish Academy of Sciences.


Abdullah Sani N.,National University of Malaysia | Ariyawansa S.,National University of Malaysia | Ariyawansa S.,National Aquatic Resources Research and Development Agency | Babji A.S.,National University of Malaysia | Hashim J.K.,Health Level
Food Control | Year: 2013

A microbiological risk assessment was conducted on Vibrio parahaemolyticus in order to estimate the risk of getting infected by consuming cooked shrimps (Penaeus monodon) for Malaysians. This study was based on the risk assessment framework developed by the Codex Alimentarius Commission. The risk estimate was calculated by using the data generated from this study and assumptions based on data taken from reports produced by the Ministry of Health Malaysia and from other studies. The @RISK software package, version 4.5 (2005 Palisade USA) in combination with Microsoft® Excel were used to run the simulations. All of the calculations were performed by the Monte Carlo method of simulations from specified input distributions and appropriately combining the sampled values to generate the corresponding output distributions. All simulations, consisting of 10,000 iterations were undertaken. The estimated illness per year was 123 people (aged from 18 to 59 years) for Malaysians. The 90% of distribution of illness due to the consumption of cooked shrimps lies between 49 and 197 cases per year. The incidence rate of illness/100,000 population/year (aged between 18 and 59 years) is 1.3 while 90% distribution lies between 0.5 and 2. In the case of shrimp that were cooked during meal preparation, the hazard has been significantly reduced. It is important to pay attention to temperature control during harvesting and post-harvest handling. It is also required to prevent cross-contamination during handling and preparation of shrimps and adequate cooking before consumption. © 2012.


Subasinghe N.D.,Sri Lanka Institute of Fundamental Studies | Jinadasa P.,National Aquatic Resources Research and Development Agency
Applied Mechanics and Materials | Year: 2012

Demarcation of fresh- and saline-water interface is important in water supply engineering in coastal regions. A resistivity imager system was employed to investigate the saline water intrusion to freshwater table at selected coastal locations in Sri Lanka. This is the first such attempt in Sri Lanka using the above technique. Systematic geo-resistivity investigations were carried out at randomly selected sites at Mundel and Rekawa coastal areas. Measured and calculated values generally show good agreement, especially in Mundel area, where the current penetration is good. The results indicate a possibility of using resistivity imager system to demarcate the saline and fresh water interfaces and intermixing zones, especially in the wet zone. © (2012) Trans Tech Publications, Switzerland.


Jayasiri H.B.,National Aquatic Resources Research and Development Agency | Purushothaman C.S.,Central Institute of Fisheries Education | Vennila A.,Central Institute of Fisheries Education
Marine Pollution Bulletin | Year: 2013

Plastic litter was quantified on four sandy beaches in Mumbai. The mean abundance of 7.49. g and 68.83 items per square metre was recorded. The abundance of plastics significantly varied among the beaches showing an increasing trend in the southern part. The abundance of plastics by weight in Dadar was significantly higher than that in Aksa. The size fractionation of plastics proved that small particles (1-20. mm) are predominant with 41.85% microplastics (1-5. mm) which emphasizes the high risk to marine organisms due to possible ingestion. The highest quantity of microplastics was seen in Juhu beach (55.33%) followed by Versova, Aksa and Dadar. The major contributing factors for the abundance are beach usage for different activities such as recreational, religious and fishing which suggest that the land-based sources provide major inputs to plastic pollution in these beaches. © 2013 Elsevier Ltd.


Jayasiri H.B.,National Aquatic Resources Research and Development Agency | Vennila A.,Central Institute of Fisheries Education | Purushothaman C.S.,Central Institute of Fisheries Education
Environmental Monitoring and Assessment | Year: 2014

Nine metals were monitored in the beach sediment in Mumbai from May 2011 to March 2012 to evaluate the spatial and temporal distributions. The average heavy metal concentrations exhibited the following order: Fe > Mn > Cr > Co > Ni > Pb > Zn > Cu > Cd for the four sampling sites. The mean concentrations (± SD) of Fe, Mn, Cr, Co, Ni, Pb, Zn, Cu and Cd were estimated to be 31.15 ± 10.02 g kg-1, 535.04 ± 76.42, 151.98 ± 97.90, 92.76 ± 14.18, 67.52 ± 11.32, 59.57 ± 15.19, 54.65 ± 15.01, 32.24 ± 8.07 and 18.75 ± 1.76 mg kg-1, respectively. The results indicated that the sediments were polluted with Cd, Cr, Co and Pb due to high anthropogenic influences. Spatial variation of metals revealed that most of the metals were high in Dadar beach and low in Aksa beach. Cd was the highest contaminant metal studied with a mean contamination factor of 93.75. The pollution load indices of the studied beaches ranged from 1.63 (Aksa) to 1.91 (Dadar) and indicated that the beach sediments were polluted with heavy metals. The heavy metal contents increased in relation to monsoon, and most of the heavy metals showed significantly high concentrations in November during the post-monsoon. The statistical analysis revealed significant effect of study site on all the metals studied. Further, there was a significant difference on metal accumulation on bimonthly basis in relation to weather pattern in Mumbai beaches. © 2013 Springer Science+Business Media Dordrecht.

Loading National Aquatic Resources Research and Development Agency collaborators
Loading National Aquatic Resources Research and Development Agency collaborators