[Show abstract][Hide abstract] ABSTRACT: It is important to know the ultimate role of small copepods in structuring mesozooplankton community
pattern and diversity on an estuary-coastal gradient. Here multivariate analyses were used to elucidate
this in the Godavari estuary, on the east coast of India. During May 2002, corresponding to the spring
intermonsoon, mesozooplankton were sampled from 4 GPS fixed stations in the estuarine reaches of
River Godavari and 19 in the coastal waters where Godavari enters the Bay of Bengal. There were 91
mesozooplankton taxa represented by 23 divergent groups. Copepods were by far the most prominent in
terms of species richness, numerical abundance, and widespread distribution followed by appendicularians.
Small copepods of families Paracalanidae, Acartiidae, Oithonidae, Corycaeidae, Oncaeidae, and
Euterpinidae dominated. There were differing regional mesozooplankton/copepod communities, that
segregated the estuary-coastal sites into different biotic assemblages: Group-I representing the estuary
proper, Group-II estuary mouth and near shore, Group-III the intermediate coastal stations and Group-IV
the coastal-offshore waters. Alpha (SRp, H0 , J0 , D*) and beta diversity (MVDISP, b, b-dissimilarity) measures
varied noticeably across these assemblages/areas. The significant correlation of small copepod
abundance with total mesozooplankton abundance and biomass (mgDM.m�3) in the estuarine (r: 0.40)
and coastal (r: 0.46e0.83) waters together with a regression analysis of diversity measures have revealed
the importance of small copepods in the overall mesozooplankton/copepod community structure. There
were ‘characterizing’ and ‘discriminating’ species, responsible for the observed assemblage patterns.
Mesozooplankton/copepod community structure and the size-spectra observed during this study indicate
an estuarine-coastal gradient in plankton tropho-dynamics that may shift between a microbial
dominated system inside the estuary and mixotrophy in the coastal waters. The functional diversity of
copepods revealed features of an effective niche sharing and efficient utilization of the coastal resources
by the resident zooplankton some of which are brought out for the first time showing a tropical estuary
under the influence of monsoons. The present study also illustrates the importance of, and advocates the
need for, incorporating complementary or additional biodiversity measures while describing biotic
communities vis-à-vis environmental gradients.
[Show abstract][Hide abstract] ABSTRACT: After withdrawal of the Indian Summer Monsoon and until onset of the next monsoon, i.e., roughly during November–May, winds
in the coastal regions of India are dominated by sea breeze. It has an impact on the daily cycle of the sea state near the
coast. The impact is quite significant when large scale winds are weak. During one such event, 1–15 April 1997, a Datawell
directional waverider buoy was deployed in 23 m water depth off Goa, west coast of India. Twenty-minute averaged spectra,
collected once every three hours, show that the spectrum of sea-breeze-related ‘wind-seas’ peaked at 0.23 ±0.05 Hz. These
wind-seas were well separated from swells of frequencies less than 0.15 Hz. The TMA spectrum (Bouwset al 1985) matched the observed seas spectra very well when the sea-breeze was active and the fetch corresponding to equilibrium
spectrum was found to be 77±43 km during such occasions. We emphasize on the diurnal cycle of sea-breeze-related sea off the
coast of Goa and write an equation for the energy of the seas as a function of the local wind
Journal of Earth System Science 04/2006; 115(2):229-234. DOI:10.1007/BF02702036 · 0.79 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Longterm current measurements for a period of 14 months were taken up by National Institute of Oceanography, Goa, India at high current regime in Gulf of Khambhat. The measurement was intended at seabed for obtaining vector averaged current speed and direction on the sea surface and at a fixed five layers. The company supplied frame was not suitable to use at the proposed measurement location, owing to random oscillation in the seabed, strong currents and high concentration of sediments in the water column. The authors have designed a special frame to withstand for above problems and the measurements were carried out successfully for such harsh environment, first time in India. The details of the design and the measurement techniques are described in the paper.
[Show abstract][Hide abstract] ABSTRACT: Measurements of the longshore sediment transport rate (LSTR) along the surf zone at a 4-km-long beach on the central west coast of India were made over a 4-month period. During the study, both the lateral and vertical distributions of the sediment transport rate were measured with traps deployed on a line spanning the surf zone. Sediment transport in the swash zone was not considered in the present study. The longshore current was measured at each trap location. The breaking wave parameters were calculated from a directional wave buoy at 16-m water depth. The measured values were compared with those calculated from three selected empirical formulas. The standard coefficient values in the empirical formulas were used without calibration to the data sets. The measured average gross transport was 726 m3/day and that calculated were 1108, 1017, and 781 m3/day based on CERC, Walton and Bruno, and Van Rijn formula. During the data collection 69% of the time, the transport was direct towards north, and in the remaining period, it was direct towards south. The correlation coefficient between the longshore sediment transport rates measured and those calculated by CERC, Walton and Bruno, and Van Rijn formula were 0.38, 0.71, and 0.74, respectively. The average RMS error between the measured and the calculated longshore sediment transport rate based on CERC, Walton and Bruno, and Van Rijn formula were 0.91, 0.57, and 0.47.
[Show abstract][Hide abstract] ABSTRACT: Studies (1996–'99) on the community structure of a mangrove forest in Coringa Wildlife Sanctuary in the Godavari estuarine system on the East Coast of India revealed altogether 15 species of mangroves represented by 8 families and 10 genera besides, 6 associate plant species and 6 of marshgrass. Description of forest structure (PCQM method) included measures of species composition, tree density, basal area and spatial distribution patterns of component vegetation at 75 GPS fixed locations. Avicennia marina, A. officinalis, Excoecaria agallocha, Aegiceras corniculatum, Sonneratia apetala, Ceriops decandra, Rhizophora apiculata and R. mucronata were the important mangrove species. Tree density varied between 47 and 1731 stems/0.1 ha and basal area 0.1 and 10.9 m2/0.01 ha. With the help of multivariate analysis (PRIMER) and based on species composition and tree density, it was possible to subdivide the sites into five groups that showed characteristic zonation patterns. For example, E. agallocha was typical of landward locations. A. marina (along with A. officinalis and A. alba) represented sites at the bed level and neap high tide level. There was a large group of sites inhabited by diverse species (14) indicative of spring high tide level conditions. Tidal elevation and ambient salinity appeared important in determining the observed zonation.
[Show abstract][Hide abstract] ABSTRACT: Numerous theoretical and field studies have been carried out to quantify the volume and direction of littoral sediment transport along the Indian coast. Nevertheless, very little effort has been made to identify the sources for the littoral transport, which feed to the nearshore transport mechanism and on sinks, wherein the continuous movement of the littoral sediment breaks and deposits over a considerable period of time. Rivers are the major source for the littoral drift and the annual discharge of sediments to sea along the Indian coast is about 1.2 × 10<sup>12</sup> kg. The construction of inland dams, irrigation barrages, have considerably reduced the sediment load brought to the sea. Due to the fall in the influx of sediments and concentration of wave energy, many coastal segments experience erosion. In order to identify the extent of the significance of the major sinks for the sediment deposition along the Indian coast, a study was undertaken to evaluate the long-term sediment deposition in Gulf of Kachchh, Gulf of Khambhat, Gulf of Mannar, Palk Bay and Sandheads. The study shows an average yearly deposition of sediments to a thickness of 0.025 m at Gulf of Kachchh, 0.03 m at Gulf of Khambhat, 0.01 m at Gulf of Mannar, 0.006 m at Palk Bay and 0.003 m at Sandheads. The depositional features identified in the present study have been noticed as occurrences of spits, shoals and the progradation of coastline.
[Show abstract][Hide abstract] ABSTRACT: The accurate assessment of longshore sediment transport pattern along Nagapattinam-Poompuhar, Tamil Nadu, India coastline bears significance due to the historical erosion and its geographical location adjoining the sheltered Palk Bay. Directional waves were measured off Nagapattinam coastline for one year to estimate the longshore sediment transport rate. It shows that the transport rate is relatively high about 0.1 x 10 sup(6) m sup(3)/month in November and December and is low showing less than 0.03 x 10 sup(6) m sup(3)/month in March, April and July. Though the annual gross transport is found to be 0.6 x 10 sup(6) m sup(3)/year, the annual net transport is very low showing less than 0.006 x 10 sup(3)/year (towards north), indicating the coastline tends to be a nodal drift regime. The temporary rise in wave activities during the cyclonic days often increases the southerly drift, which partly gets deposited in the Palk Bay and causes deficit for the northerly drift
[Show abstract][Hide abstract] ABSTRACT: This paper describes wave directional spreading in shallow water. Waves were measured for a period of 2 months using the Datawell directional waverider buoy at 15 m water depth on the east coast of India in the Bay of Bengal. The study also showed that in shallow water wave directional spreading was narrowest at peak frequency and widened towards lower and higher frequencies. The wind direction was found to deviate from the wave direction during most of the time. The unidirectional spectrum was found to be satisfactorily represented by Scott spectra.
[Show abstract][Hide abstract] ABSTRACT: Vainguinim Beach is a small and narrow pocket beach located on the rocky coast of Dona Paula Bay, at the estuarine front of the Zuari River in Goa, India. The beach has been widely used for recreation and swimming by a large number of tourists. The beach sediments consist primarily shell fragments and quartz, with heavy mineral composed of ilmenits, magnetite and manganese. The black stain of the fine-grained heavy minerals deposited on the beach face reduces the aesthetics of the beach. This paper summarises the various studies undertaken to identify the sediment processes and the possible measures to improve the usability of the beach
[Show abstract][Hide abstract] ABSTRACT: Goa has a 125-km-long coastline of which two-thirds consists of beautiful sandy beaches. There are mainly 17 beaches having significant importance of tourism. Sporadically, surf drownings have been reported at a few stretches of the beach. Longshore currents were measured at 2-week intervals from November 1993 to October 1994 along these beaches to identify the zones of strong longshore currents and rip currents. Entire beaches were found to be unsafe for swimming during the southwest monsoon season. Parts of stations 5 and 6 in Harmal Beach, 16 at Vagator Beach, 51-54 at Miramar Beach, 75 and 76 at Valsao Beach, 84 at Majorda Beach, and 116 at Palolem Beach are observed to have the risk of permanent rip current zones; and they are unsafe places for swimming all through the year. Parts of Colva, Banaulim, and Agonda beaches, which are suitable for surf swimming, are identified
Journal of Waterway Port Coastal and Ocean Engineering 11/1997; 123(6). DOI:10.1061/(ASCE)0733-950X(1997)123:6(322) · 1.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Longshore sediment transport characteristics of the Kerala Coast have been examined to delineate various physical processes affecting the different coastal environments. Monthly averages of the daily LEO (Littoral Environmental Observation) data for one year made at each station have been used for this study. Monthly longshore sediment transport rates showed high variability in the sediment transport mechanism.
[Show abstract][Hide abstract] ABSTRACT: Numerical wave refraction study for the Kerala Coast has been carried out for waves representing southwest monsoon (June-September), northest monsoon (October-February) and fair weather period (February-May). Distribution of wave heights vary significantly from place to place due to wave refraction and shoaling. The covergence and divergence of wave energy induce non-uniform distribution of wave heights during the monsoon period. Ezhimala promontory causes waves to refract considerably along the coastline of Cannanore, Badagara and Mahe during October to February, whereas the headland at Thankasseri induces divergence of wave energy along Quilon and Varkallai. Vypin experiences convergence of wave energy almost throughout the year.
[Show abstract][Hide abstract] ABSTRACT: Maintenance dredging has been carried out along the navigational channel at Kavaratii Island and dredge spoil is disposed in the open sea. This paper describes the movement of sediment plume while dredging and disposal. The study indicates that for the present disposal location, the sediment plume settles down before reaching 50 m waterdepth, whereas shifting the disposal location to a distance of 1000 m from the reef, would cause the sediments to settle down before 200 m water depth. The study confirms that there is no settlement of dredge spoil in the lagoon bed or on the reef.
[Show abstract][Hide abstract] ABSTRACT: Mean grain size distribution under different environmental conditions along the coast of Kerala showed considerable spatial variation (0.14-0.96 mm). Standard deviation values indicated a very well sorted class along all the beaches with a lowest value of 0.48 phi. Difference in standard deviation values between the stations were significant in all the stations. Samples were nearly symmetrical to negatively skewed with most of the values clustered at -0.01 to -0.10.
Indian Journal of Geo-Marine Sciences 01/1996; 25(3). · 0.31 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Estimation of breaker angle in a littoral environmental observation (LEO)program is still based on a visual method and therefore is subjective. Breaker angles thus measured generally vary from person to person. In the absence of a sophisticated wave-direction recording instrument, a simple and practical method has been evolved based on the time lapse between the wave breaking progressively at two points along the crest parallel to the shoreline. This method removes to a greater extent the subjectivity in observation, thereby making it a more reliable practical procedure. The method can be readily adopted for field observation by coastal engineers.
Journal of Waterway Port Coastal and Ocean Engineering 05/1994; 120(3). DOI:10.1061/(ASCE)0733-950X(1994)120:3(318) · 1.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Estimation of the breaker angle in the littoral environmental observation (LEO) programme is still based on visual methods and therefore is subjective in nature. In the absence of a wave direction recording instrument, a simple device called the wave vane as described here has been developed to measure the breaking wave angle. The changes in the horizontal component of the orbital velocity under a progressive wave govern the operation of the wave vane. The wave vane consists of a pair of fins, one responding to the velocity in the direction of wave propagation below the wave crest, and the other to the velocity in the direction opposite to wave propagation below the wave trough. This results in wave vane orienting itself in the direction of the wave orthogonal. The performance of the wave vane was evaluated using the instrumentally recorded wave directional data as well as the visually observed data. The wave vane was found to give the wave directional information fairly accurate for the open coast where the influence of tidal currents was negligible.
[Show abstract][Hide abstract] ABSTRACT: Ten day records of Aanderaa current meters (24 Dec 1981 to 2 Jan. 1982) at four depths, viz. 30, 45, 60 and 75 m at Bombay High (19˚24.5'N, 71˚2.5'E) off the west coast of India, in a water depth of 80 m have been subjected to spectral, cross-spectral, rotary spectral, harmonic analysis, and low pass filtering in the frequency domain. It was found that at semidiurnal and diurnal frequencies the currents were predominantly barotropic. At all depths the tidal ellipses corresponding to the semidiurnal and diurnal tides were oriented roughly perpendicular to the shelf-break while the mean currents were northwestwards along the shelf-break. During the observation period, the mixed layer (-50 m) remained isothermal while a steady rise in temperature (~2˚C) with time was noticed in the cooler bottom layer.
[Show abstract][Hide abstract] ABSTRACT: The longshore current velocity varied between 0.1 and 0.33 m.sec/1. The longshore current direction was predominantly southward at Ratnagiri, Ambolgarh (Maharashtra, India), whereas it was variable at Vengurla during the study period. Based on the field measurements, the estimated longshore sediment transport rates at Ratnagiri, Ambolgarh and Vengurla were 1.19 x 10 super(5), 1.9 x 10 super(5) and 0.53 x 10 super(5) m super(3) y/1 respectively and the direction was southward. Significance of field measurement is emphasized here, in view of the large variation in the computed longshore sediment transport rates reported in earlier studies
[Show abstract][Hide abstract] ABSTRACT: Chilka Lake (Orissa, India) inlet mouth is exposed to high annual littoral drift of about 1 x 10 super(6) m super(3). The inlet mouth was observed to migrate about 500 m northward during the period of one year study. Measurement on daily longshore currents indicated that the predominant longshore sediment transport across the mouth is towards north throughout the year