Seasonal variations in Secondary Production of the Mandovi-Zuari Estuarine System of Goa

7-9Mean rates of secondary production in the Mandovi, Zuari and Cumbarjua canal, Goa, India were 16.9, 35.9 and 32.4 mg C/m2/day respectively. The general hydrographic conditions of the Zuari were responsible for the higher secondary production. In general, the saline period was more productive (12.9 mg dry wt/m3/day) compared to the low saline period (11 mg dry wt/m3/day). The average secondary production in the estuarine system was 21.4 mg dry wt/m3/day or 1078 tonnes carbon/yr. The coefficient of energy transfer from primary to secondary level was 6.6%. Theoretical estimate of fish biomass in this estuarine system was 1007 tonnes/yr

Abundance and relationship of bacteria with transparent exopolymer particles during the 1996 summer monsoon in the Arabian Sea

Bacterial abundance and production, numbers, sizes and concentrations of transparent exopolymer particles (TEP) and total organic carbon (TOC) were measured during the 1996 summer monsoon to understand the relationship between TEP, the most labile particulate organic carbon, and bacteria. While high regional variability in the vertical distribution of TOC was discernible, TEP concentrations were high in surface waters at 18-20°N along 64°E with concentrations well over 25 mg alginic acid equivalents I-1 due to upwelling induced productivity. Their concentrations decreased with depth and were lower between 200 and 500 m. Bacterial concentrations were up to 1.99 × 108 I-1 in the surface waters and decreased by an order of magnitude or more at depths below 500 m. A better relationship has been found between bacterial abundance and concentrations of TEP than between bacteria and TOC, indicating that bacterial metabolism is fueled by availability of TEP in the Arabian Sea. Assuming a carbon assimilation of 33%, bacterial carbon demand (BCD) is estimated to be 1.017 to 4.035 gCm-2 d-1 in the surface waters. The observed TEP concentrations appear to be sufficient in meeting the surface and subsurface BCD in the northern Arabian Sea

Physical control of primary productivity on a seasonal scale in central and eastern Arabian Sea

Using in situ data collected during 1992-1997, under the Indian programme of Joint Global Ocean Flux Study (JGOFS), we show that the biological productivity of the Arabian Sea is tightly coupled to the physical forcing mediated through nutrient availability. The Arabian Sea becomes productive in summer not only along the coastal regions of Somalia, Arabia and southern parts of the west coast of India due to coastal upwelling but also in the open waters of the central region. The open waters in the north are fertilized by a combination of divergence driven by cyclonic wind stress curl to the north of the Findlater Jet and lateral advection of nutrient-rich upwelled waters from Arabia. Productivity in the southern part of the central Arabian Sea, on the other hand, is driven by advection from the Somalia upwelling. Surface cooling and convection resulting from reduced solar radiation and increased evaporation make the northern region productive in winter. During both spring and fall inter-monsoons, this sea remains warm and stratified with low production as surface waters are oligotrophic. Inter-annual variability in physical forcing during winter resulted in one-and-a-half times higher production in 1997 than in 1995

Observed anomalous upwelling in the Lakshadweep Sea during the summer monsoon season of 2005

Repeat near-fortnightly expendable bathythermograph (XBT) transects made along Kochi-Kavaratti (KK) shipping lane in the Lakshadweep Sea (LS) during 2002–2006 are examined to describe the observed year-to-year variability of upwelling during summer monsoon season (SMS). Among all the years, the upwelling characterized by up-sloping of 25°C isotherm is relatively weaker and persisted until November during SMS of 2005 and is stronger during the SMS of 2002. As a result of prolonged upwelling, the sea surface temperature has shown cooling extending into the postmonsoon season. The estimated marine pelagic fish landings along the southwest coast of India (SWCI) have also shown increase until December. The governing mechanisms both in terms of local and remote forcings are examined to explain the observed anomalous upwelling during SMS of 2005. The equatorward alongshore wind stress (WS) along the KK XBT transect persisted in a transient manner beyond September only during SMS of 2005. The westerly wind bursts over the equator during the winter of 2004–2005 are both short-lived and relatively weaker triggering weaker upwelling Kelvin waves that propagated into LS in the following SMS of 2005. The observed distribution of negative sea surface height anomaly in the LS is relatively weaker during the SMS of 2005 and lasted longer. The correlation analysis suggests that the local alongshore WS off the SWCI and the remote forcing from the southern coast of Sri Lanka has greater influence on the observed interannual variability of upwelling in the LS when compared to the remote forcing from the equator

High biological productivity in the central Arabian Sea during the summer monsoon driven by Ekman pumping and lateral advection

Open oceans are generally oligotrophic and support less biological production. Results from the central Arabian Sea show that it may be an exception to this. We provide the observational evidence of fairly high biological production (up to 1700 mg C m-2 d-1) in the central Arabian Sea, along 64oE, during the summer monsoons of 1995 and 1996. The reasons for the observed high biological production, comparable to that from the traditionally well-known Somali upwelling region, were examined in light of the physical forcing and prevailing chemical fields. In the northern part of the central Arabian Sea, north of the axis of the Findlater Jet, upward Ekman pumping and entrainment driven by basin-wide winds along with advection of upwelled waters from the coastal region of Arabia supply nutrients to the upper layers. In the southern part, production is supported by nutrients advected from the Somali upwelling regio

Seasonal and interannual variations of oceanographic conditions off Mangalore coast (Karnataka, India) in the Malabar upwelling system during 1995–2004 and their influences on the pelagic fishery

Mangalore coast is well known for its multi-species and multi-gear fisheries and the fishery and oceanographic features of this region is a true representation of the Malabar upwelling system. Ten years of study (1995–2004) of oceanographic parameters has been carried out from the inshore waters off Mangalore to understand their seasonal and interannual variations and influences on the pelagic fishery of the region. Attempt has been also made to understand the influence of local and global environmental conditions on the alternating patterns of abundance between the Indian mackerel and oil sardine from the area

Reactive Nitrogen in Coastal and Marine Waters of India and Its Relationship With Marine Aquaculture

India is bordered in the soutii, south-west, and south-east with Indian Ocean, Arabian Sea (AS), and the Bay of Bengal (BOB), respectively. Indian coast is 7517 km long comprising 5423 km in the peninsular India and 2094 km in Andaman and Nicobar, and Lakshadweep Islands. The Indian exclusive economic zone (EEZ) is spread in 2.02 million sq km (0.86 million sq km in west coast, 0.56 m illion sq km in east coast and 0.6 million sq km in Andaman and Nicobar Islands). The Indian marine environmentconsisting of adjoining coastal areas and EEZ directly sustains useful habitats and suppons the livelihood of 3.9 million fishers. Nearly 25% of the country’s population resides in these areas and about 340 communities are primarily occupied in marine and coastal fisheries (MoEF, 2009; SACEP, 2014). Nitrogen (N) exists in various chemical forms, produced by marine biota through several chemical transformations during their growth and metabolism in the marine environment. Nitrogen as N2 is generally unavailable in marine conditions and thereby, the equilibrium of the processes of N2 fixation (conversion of atmospheric N2 to organic nitrogen) and denitrification (conversion of nitrate to N2) decides the bioavailable nitrogen supply and productivity (Gruber, 2008)

Being young in a changing world: how temperature and salinity changes interactively modify the performance of larval stages of the barnacle Amphibalanus improvisus

The fate of key species, such as the barnacle Amphibalanus improvisus, in the course of global change is of particular interest since any change in their abundance and/or performance may entail community-wide effects. In the fluctuating Western Baltic, species typically experience a broad range of environmental conditions, which may preselect them to better cope with climate change. In this study, we examined the sensitivity of two crucial ontogenetic phases (naupliar, cypris) of the barnacle toward a range of temperature (12, 20, and 28°C) and salinity (5, 15, and 30 psu) combinations. Under all salinity treatments, nauplii developed faster at intermediate and high temperatures. Cyprid metamorphosis success, in contrast, was interactively impacted by temperature and salinity. Survival of nauplii decreased with increasing salinity under all temperature treatments. Highest settlement rates occurred at the intermediate temperature and salinity combination, i.e., 20°C and 15 psu. Settlement success of “naive” cyprids, i.e., when nauplii were raised in the absence of stress (20°C/15 psu), was less impacted by stressful temperature/salinity combinations than that of cyprids with a stress history. Here, settlement success was highest at 30 psu particularly at low and high temperatures. Surprisingly, larval survival was not highest under the conditions typical for the Kiel Fjord at the season of peak settlement (20°C/15 psu). The proportion of nauplii that ultimately transformed to attached juveniles was, however, highest under these “home” conditions. Overall, only particularly stressful combinations of temperature and salinity substantially reduced larval performance and development. Given more time for adaptation, the relatively smooth climate shifts predicted will probably not dramatically affect this species