23 research outputs found
Stellar structure of quark stars in a modified Starobinsky gravity
We propose a form of gravity-matter interaction given by in the
framework of gravity and examine the effect of such interaction in
spherically symmetric compact stars. Treating the gravity-matter coupling as a
perturbative term on the background of Starobinsky gravity, we develop a
perturbation theory for equilibrium configurations. For illustration, we take
the case of quark stars and explore their various stellar properties. We find
that the gravity-matter coupling causes an increase in the stable maximal mass
which is relevant for recent observations on binary pulsars
Satellite ocean colour sensors
The 70% of the earthтАЩs surface is covered by the ocean and the life inhabiting the
oceans play an important role in shaping the earthтАЩs climate. Phytoplankton, also known as
microalgae, are the single celled, autotrophic components of the plankton community and
a key part of oceans, seas and freshwater basin ecosystems. They are significant factor in
the ocean carbon cycle and, hence, important in all pathways of carbon in the ocean.
Phytoplankton contain chlorophyll pigments for photosynthesis, similar to terrestrial plants
and require sunlight in order to live and grow. Most of them are buoyant and float in the
upper part of the ocean, where plenty of sunlight is available. They also require inorganic
nutrients such as nitrates, phosphates, and sulphur which they convert into proteins, fats,
and carbohydrates. In a balanced ecosystem, phytoplankton are the base of the food web
and provide food for a wide range of sea creatures (NOAA). The measurement of
phytoplankton can be indexed as chlorophyll concentration and is important as they are
fundamental to understanding how the marine ecosystem responds to climate variability
and climate change
Regional and seasonal variations in phytoplankton
One of the main goals of remote-sensing observations is the study of seasonal cycles
of phytoplankton biomass in different regions of the World Ocean. In many regions these
cycles repeat every year including minor details. This pattern is a result of seasonal oscillations
of physical environment. In high latitudes these oscillations are more pronounced, and the
response of phytoplankton is more evident
Identifying mesoscale eddies- Relevance to mud banks and fishery
The most popular fishing area during mud bank formation in Kerala is off Punnapra
coast in Alapuzha district. This place is equipped with unique crafts such as one-man operated
expanded polystyrene thermocol made gill netters, and several other traditional crafts. The
fishermen community along this coast is vigilant against any mechanized fishing during
mud bank period which falls in the southwest monsoon months when there is a ban on
mechanized crafts. There are comparable datasets, from mud bank vis-├а-vis non mud bank
in this region, which indicate that, the catch per unit effort (CPUE) do not vary significantly.
Fishing in Thrissur and Malappuram districts are not restricted by the formation of mud
banks. In these districts modified outboard crafts such as pair trawlers operating double
net and the high horse power of the out board engines are generally on a look out for nonmud
bank resources also. In Malappuram district, the occurrence of the mud bank fishery is
for limited days and generally less reported. Therefore, the analysis of data sets indicated
better production and CPUE from non-mud banks in Malappuram. In general we can say
that there is no significant increase in abundance of fishes reported from the mud bank
regions. But the calm waters generated at certain pockets of the otherwise disturbed coastal
waters act as areas for seasonal landings of fish
Satellite Data Products for Marine Ecosystem Studies
Satellite Data Products for Marine Ecosystem Studie
Fundamentals of ocean colour remote sensing
Remote sensing refers to collection of information about an object without being in
direct contact with the object. Remote sensing aids in measuring remote areas which are
inaccessible by any other means and offer less expense than in-situ measurements. Remote
sensing facilitates creation of long time series and extended measurement. This has the
advantage that several parameters can be measured at same time and satellite-based remote
sensing measurements allow global observations. Remote sensing has its own advantages
and disadvantages. The limitation includes indirect measurements of large areas which are
not of interest to the user. The automated instrument degradation creates retrieval errors
and are affected by several factors/processes, and not only by the object of interest.
Additional assumptions and models are needed for the interpretation of the measurements
and before using these models in oceanographic studies, it is extremely important to validate
the performance of the various ocean colour algorithms with in-situ observations (Swirgon
et al., 2015)
Comparison of Seasonal Cycles of Phytoplankton Chlorophyll, Aerosols, Winds and Sea-Surface Temperature off Somalia
In climate research, an important task is to characterize the relationships between
Essential Climate Variables (ECVs). Here, satellite-derived data sets have been used to
examine the seasonal cycle of phytoplankton (chlorophyll concentration) in the waters
off Somalia, and its relationship to aerosols, winds and Sea Surface Temperature
(SST). Chlorophyll-a (Chl-a) concentration, Aerosol Optical Thickness (AOT), ├Еngstr├╢m
Exponent (AE), Dust Optical Thickness (DOT), SST and sea-surface wind data for a
16-year period were assembled from various sources. The data were used to explore
whether there is evidence to show that dust aerosols enhance Chl-a concentration in
the study area. The Cross Correlation Function (CCF) showed highest positive correlation
(r2 = 0.3) in the western Arabian Sea when AOT led Chl-a by 1тАУ2 time steps (here, 1
time step is 8 days). A 2 ├Ч 2тЧж box off Somalia was selected for further investigations.
The correlations of alongshore wind speed, Ekman Mass Transport (EMT) and SST
with Chl-a were higher than that of AOT, for a lag of 8 days. When all four variables
were considered together in a multiple linear regression, the increase in r2 associated
with the AOT is only about 0.02, a consequence of covariance among AOT, SST,
EMT and alongshore wind speed. The AOT data show presence of dust aerosols
most frequently during the summer monsoon season (JuneтАУSeptember). When the
analyses were repeated for the dust aerosol events, the correlations were generally
lower, but still significant. Again, the inclusion of DOT in the multiple linear regression
increased the correlation coefficient by only 2%, indicating minor enhancement in
Chl-a concentration. Interestingly, during summer monsoon season, there is a higher
probability of finding more instances of positive changes in Chl-a after one time step,
regardless of whether there is dust aerosol or not. On the other hand, during the
winter monsoon season (NovemberтАУDecember) and rest of the year, the probability
of Chl-a enhancement is higher when dust aerosol is present than when it is absent.
The phase relationship in the 8-day climatologies of Chl-a and AOT (derived from
NASAтАЩs SeaWiFS and MODIS-A ocean colour processing chain) showed that AOTled Chl-a for most of the summer monsoon season, except when Chl-a was very high,
during which time, Chl-a led AOT. The phase shift in the Chl-a and AOT climatological
relationship at the Chl-a peak was not observed when AOT from Aerosol Climate Change
Initiative (Aerosol-CCI) was used
Upwelling over the eastern Arabian Sea
Upwelling is a vital oceanographic phenomena determining the biological productivity
of the coastal oceanic provinces in a greater extent. The annual pelagic fisheries of coastal
rim countries, adjacent to the eastern boundary of the Ocean, over the trade wind zone are
greatly dependent on upwelling. Over the North India Ocean (NIO), west coast of India,
adjacent to the eastern Arabian Sea is well known for its seasonal occurrence of upwelling
and downwelling annually. Over the past, several authors have studied upwelling along the
west coast of India (Banse 1959, 1968; Sharma 1978; Johannessen et al., 1987
Course Manual Winter School on Structure and Functions of Marine Ecosystem: Fisheries
Marine ecosystems comprises of diverse organisms
and their ambient abiotic components in varied
relationships leading to an ecosystem functioning.
These relationships provides the services that are
essential for marine organisms to sustain in the nature.
The studies examining the structure and functioning
of these relationships remains unclear and hence
understanding and modelling of the ecological
functioning is imperative in the context of the threats
different ecosystem components are facing. The relationship between marine
population and their environment is complex and is subjected to fluctuations
which affects the bottom level of an ecosystem pyramid to higher trophic
levels. Understanding the energy flow within the marine ecosystems with
the help of primary to secondary producers and secondary consumers are
potentially important when assessing such states and changes in these
environments.
Many of the physiological changes are known to affect the key functional
group, ie. the species or group of organisms, which play an important role
in the health of the ecosystem. In marine environment, phytoplankton are
the main functional forms which serves as the base of marine food web.
Any change in the phytoplankton community structure may lead to alteration
in the composition, size and structure of the entire ecosystem. Hence, it is
critical to understand how these effects may scale up to population,
communities, and entire marine ecosystem. Such changes are difficult to
predict, particularly when more than one trophic level is affected. The
identification and quantification of indicators of changes in ecosystem
functioning and the knowledge base generated will provide a suitable way
of bridging issues related to a specific ecosystem. New and meaningful
indicators, derived from our current understanding of marine ecosystem
functioning, can be used for assessing the impact of these changes and can
be used as an aid in promoting responsible fisheries in marine ecosystems.
Phytoplantkon is an indicator determining the colour of open Ocean. In
recent years, new technologies have emerged which involves multidisciplinary
activities including biogeochemistry and its dynamics affecting
higher trophic levels including fishery. The winter school proposed will
provide the insights into background required for such an approach involving
teaching the theory, practical, analysis and interpretation techniques in
understanding the structure and functioning of marine ecosystems from
ground truth measurements as well as from satellite remote sensing data.
This is organized with the full funding support from Indian council of
Agricultural Research (ICAR) New Delhi and the 25 participants who are
attending this programme has been selected after scrutiny of their
applications based on their bio-data. The participants are from different
States across Indian subcontinent covering north, east, west and south.
They are serving as academicians such as Professors/ scientists and in similar
posts. The training will be a feather in their career and will enable them to
do their academic programmes in a better manner. Selected participants
will be scrutinized initially to understand their knowledge level and classes
will be oriented based on this. In addition, all of them will be provided with
an e-manual based on the classes. All selected participants are provided
with their travel and accommodation grants. The faculty include the scientists
who developed this technology, those who are practicing it and few user
groups who do their research in related areas. The programme is coordinated
by the Fishery Resources Assessment Division of CMFRI. This programme
will generate a team of elite academicians who can contribute to sustainable
management of marine ecosystem and they will further contribute to
capacity building in the sector by training many more interested researchers
in the years to come
Study on Sea Surface Temperature and Chlorophyll-a concentration along the south-west coast of India
Global climate change affects the oceanographic features and distribution of marine fishes as they are poikilothermic animals. Study of oceanographic variables in a localized region is more relevant in the context of ecological responses rather than global or continental variations. In this study, time series analysis of chlorophyll-a concentration (Chl-a) in sea water and sea surface temperature (SST) was performed separately for southern, middle and northern stratum along south-west coast of India using various statistical tools. The SST showed an increasing trend along the entire south-west coast of India after the year 1995. The northern and southern stratum of south-west coast were highly influenced by rising SST, whereas middle stratum in present scenario showed stable conditions in terms of Chl-a concentration. The study provides a baseline information about changing patterns of oceanographic features along the south-west coast of India giving a better understanding of changing global climatic conditions in coastal ecosystems