Spatiotemporal Distribution of Harmful Algal Flora in the Tropical Estuarine Complex of Goa, India

Mandovi and Zuari estuarine complex is monsoon-influenced estuaries located along the central west coast of India. During the past few years, there has been an increase in nutrient loading specially during monsoonal runoff which is responsible for the growth of harmful algal flora. To understand occurrence and distribution of harmful algal blooms species, daily/alternate day samplings were carried out in Mandovi and Zuari estuaries during 2007-2008 and 2008-2009 periods, respectively, comprising of monsoon (June–November) and nonmonsoon (December–May). In Mandovi, total 54 HAB species with 49 in monsoon and 36 during nonmonsoon period were reported. In Zuari, total 46 HAB species with 38 in monsoon and 41 were reported during nonmonsoon period. Bray-Curtis cluster analysis based on log-transformed phytoplankton density detected seven well-defined groups revealing spatiotemporal variability. The density of the dominant harmful algal species was significantly positively correlated with nutrients, but negatively correlated with salinity. The results of the study indicate that monsoon plays an important role in occurrence and distribution of harmful algal species having direct correlation with salinity variations and nutrient loading

Effect of freshwater influx on phytoplankton in the Mandovi estuary (Goa, India) during monsoon season: Chemotaxonomy

The Mandovi estuary is a prominent water body that runs along the west coast ofIndia. It forms an estuarine network with the adjacent Zuari estuary, connected via the Cumbharjua canal. The physico-chemical conditions seen in the Mandovi estuary are influenced by two factors: the fresh water runoff during the monsoon season (June-September) and the tidal influx of coastal seawater during the summer (October to May) season. However, the effects of monsoon related changes on the phytoplankton of the Mandovi estuary are not yet fully understood. An attempt to understand the same has been made here by applying the process of daily sampling at a fixed station throughout the monsoon season. It was noticed that the onset of the monsoon is responsible for an increase in nitrate levels upto 26 μM from <1 μM during pre-monsoon and enhancement of chlorophyll a (chl a) as high as 14 μg·L-1 during the same period. The phytoplankton population was observed through both chemotaxonomy and microscopy and was found to be composed mainly of diatoms. CHEMTAX analysis further uncovers the presence of several other groups of phytoplankton, the presence of which is yet to be reported in many other tropical estuaries. It includes chrysophytes, cyanobacteria, prasinophytes, prymnesiophytes and chlorophytes. The appearance of phytoplankton groups at various stages of the monsoon was recorded, and this data is discussed in relation to environmental changes in the Mandovi estuary during the monsoon season

Locating Noctiluca Miliaris in the Arabian Sea: An Optical Proxy Approach

Coincident with shifting monsoon weather patterns over India, the phytoplankter Noctiluca miliaris has recently been observed to be dominating phytoplankton blooms in the northeastern Arabian Sea during the winter monsoons. Identifying the exact environmental and/or ecological conditions that favor this species has been hampered by the lack of concurrent environmental and biological observations on time and space scales relevant to ecologic and physiologic processes. We present a bio-optical proxy for N. miliaris measured on highly resolved depth scales coincident with hydrographic observations with the goal to identify conducive hydrographic conditions for the bloom. The proxy is derived from multichannel excitation chlorophyll a fluorescence and is validated with microscopy, pigment composition, and spectral absorption. Phytoplankton populations dominated by either diatoms or other dinoflagellates were additionally discerned. N. miliaris populations in full bloom were identified offshore in low-nutrient and low-N : P ratio surface waters within a narrow temperature and salinity range. These populations transitioned to high-biomass diatom-dominated coastal upwelling populations. A week later, the N. miliaris blooms were observed in declining phase, transitioning to very-low-biomass populations of non-N. miliaris dinoflagellates. There were no clear hydrographic conditions uniquely associated with the N. miliaris populations, although N. miliaris was not found in the upwelling or extremely oligotrophic waters. Taxonomic transitions were not discernible in the spatial structure of the bloom as identified by the ocean color Chl imagery, indicating that in situ observations may be necessary to resolve community structure, particularly for populations below the surface

Colonies of marine cyanobacteria Trichodesmium interact with associated bacteria to acquire iron from dust

Iron (Fe) bioavailability limits phytoplankton growth in vast ocean regions. Iron-rich dust uplifted from deserts is transported in the atmosphere and deposited on the ocean surface. However, this dust is a poor source of iron for most phytoplankton since dust-bound Fe is poorly soluble in seawater and dust rapidly sinks out of the photic zone. An exception is Trichodesmium, a globally important, N2 fixing, colony forming, cyanobacterium, which efficiently captures and shuffles dust to its colony core. Trichodesmium and bacteria that reside within its colonies carry out diverse metabolic interactions. Here we show evidence for mutualistic interactions between Trichodesmium and associated bacteria for utilization of iron from dust, where bacteria promote dust dissolution by producing Fe-complexing molecules (siderophores) and Trichodesmium provides dust and optimal physical settings for dissolution and uptake. Our results demonstrate how intricate relationships between producers and consumers can influence productivity in the nutrient starved open ocean

Some Aspects of Culture of Mullet (<i>Mugil cephalus</i>) & Pearl Spot (<i>Etroplus suratensis</i>) in Siridaon Fish Farm, Goa

199-201Results of a study on the culture of M. cephalus and E. suratensis in Siridaon Fish Farm are presented and the influence of ecological parameters on the growth is discussed. In spite of understocking the culture is economical and hence with proper stocking strategy the profit margin can be increased to higher level

Suspended sediment dynamics regulated by the macrotidal regime: evidences from the OCM P-4 data

The understanding of the dynamics of suspended matter is crucial for coastal engineering projects and for food web in the coastal environment. The turbidity determines also optical properties of the waters, and is crucial for the coral reef system. Gulf of Kachchh is one of the macrotidal sites of India with occurrence of numerous harbors and an ecologically fragile coral reef system. The macrotidal gulf has high magnitude currents which amplify inland with tide into the gulf. A sequential analysis of imageries of the Ocean Color Monitor of IRS P-4, during different tidal phases reveals that there is a large variation in the TSM contents of the gulf associated with tidal cycle. The suspended matter dispersal under different tidal phases in the gulf is evaluated. The source to sink pathways of the suspended matter into different regions of the gulf, specifically in the vicinity of the National Marine Park, are determined which is important for restoring the stressed coral reefs

An algorithm to determine backscattering ratio and single scattering albedo

We present here algorithms to determine the inherent optical properties of water, backscattering probability and single scattering albedo at 490 and 676 nm from the apparent optical property, remote sensing reflectance. We have used the measured scattering and backscattering coefficients and the remote sensing reflectance to obtain a relationship for the backscattering ratio, which is defined as the ratio of the total backscattering to the total scattering in terms of the remote sensing reflectance of two bands. Using the empirical relationship for the total backscattering ratios, we have also computed single scattering albedo, which is defined as the ratio of the scattering to the beam attenuation coefficient. The values of single scattering albedo obtained from measured values and those obtained from the empirical method are found to be comparable. The values of single scattering albedo derived using the algorithm are found to be comparable to the measured values obtained from the eastern Arabian Sea, with the root mean squared error of 0.078 and the mean percentage error of 9.5% for the 490 nm and root mean squared error of 0.043 and the mean percentage error of 7.5% for the 676 nm