Delineating morphological traits of oceanic micro-phytoplankton as potential ecological indicators.

The micro-phytoplankton (>20 μm) adaptations and resilience were assessed using morphological traits (shape, surface-to-volume ratio; S:V, and greatest-axial-linear-dimension; GALD) from sea-surface and different SCML-depths (shallow:20-50 m, intermediate:50-100 m, and deep:100-140 m) across different bioregions of Indian Ocean. The dominant simple elongated phytoplankton-geometric-shapes (PGSs) and morphological traits showed distinct north-south distribution and varied with light and nutrient availability. Further, SCML and corresponding sea-surface PGS will be similar or dissimilar if the former is located within or deeper than mixed-layer depth.

Geographic distribution of modern dinoflagellate cysts in surface sediments of the Arabian Sea: significance of taxa and morphometry as potential ecological indicators.

Studies on dinoflagellate cysts in the Arabian Sea (AS) are limited to the coastal waters, but no information from the deeper depths. The dinoflagellate cyst assemblages in surface sediment samples (0-2 cm) from the deeper depths (up to ~ 4500 m) of central (oxygen minimum zone (OMZ)) and southeastern (oligotrophic) AS revealed that the relatively good numbers of cyst concentrations reach deeper depths of OMZ (3505 m) and oligotrophic (4368 m) regions, but the former harbored more cyst concentrations than the latter. The cyst concentration and species count (including HAB species) recorded here are lower compared to the eastern (EAS) and western (WAS) AS, but the autotrophic cyst dominance (74-83%) at deeper depths is in contrast with the heterotrophic dominance in coastal AS.

Variability in phytoplankton shape dominance in marine pelagic systems: prevalence of different adaptive strategies in the eastern Arabian Sea during the winter monsoon.

Phytoplankton communities from pelagic systems were assessed to explore the potential of using commonly used traits (such as cell geometry and taxa) as ecological function indicators from the data generated during the winter monsoon in the eastern Arabian Sea (AS). Altogether, data from two oceanic, i.e.

Responses of Phytoplankton Benthic Propagules to Macronutrient Enrichment and Varying Light Intensities: Elucidation from Monsoon-Influenced Mandovi and Zuari Riverine System : Responses of Phytoplankton Benthic Propagules to Macronutrient Enrichment and Varying Light Intensities: Elucidation from Monsoon-Influenced Mandovi and Zuari Riverine System.

The ecological importance of phytoplankton-benthic-propagules (PBP) from coastal sediments, except tropical monsoon-influenced rivers and estuaries, is well documented. PBP in such systems is often transported from upstream (near freshwater) to downstream (estuary) through freshwater discharges during monsoon and thereby experiences higher salinities (>30 PSU) and nutrients with varying light conditions due to reducing discharges during the monsoon-break/withdrawal-phase. However, the PBP responses (germination and subsequent growth) to such changes are unknown and are examined here at ~35 PSU salinity.

Dark survival in biofilm-forming microalgae: potential for colonizing benthic ecosystems.

The biofilm-forming microalgae are known to experience periods of continuous darkness (upto several days), in addition to the natural day-night cycle, especially in the intertidal sediment regions (when transported to deeper sediments) and the ships' ballast water tanks (during voyages). However, the information on community and physiological responses to different periods of darkness is limited. Here, the survival capability of biofilm-forming microalgae to varying periods of darkness (7-35 days) and the growth patterns upon resumption of normal 12 h light:dark photocycle has been addressed through simulation experiments.

Benthic-pelagic coupling assessed using phytoplankton marker pigments: a case study from the Paradip port, East Coast of India.

This study addresses the seasonal distribution of phytoplankton marker pigments (PMP) and the ratios (indicating freshness and fate) from water and surface sediments from the coastal port ecosystem (Paradip port, Odisha, east coast of India) and its utility in understanding phytoplankton pelagic-benthic linkages. Chlorophyll and PMP (for different groups and degradation) distribution revealed distinct seasonality, but the seasonal trend was different for water and sediments. High and low values were observed in the water column during inter-monsoons (fall/spring) and monsoons (southwest/northeast), respectively, whereas, in sediments, the reverse was recorded.

Simulation experiments to elucidate variable fluorescence as a potential proxy for bulk microalgal viability from natural water, sediments and biofilms: Implication in ships ballast water management.

The variable fluorescence fluorometry measuring microalgal biomass (initial fluorescence - F, a chl-a proxy) and photosynthetic efficiency (F/F) has been suggested as a potential tool in ballast-water assessment. In ballast tank, microalgae can be found in contiguous compartments i.e.

Effect of biofilm on fluorescence measurements derived from fast repetition rate fluorometers.

This study evaluates, for the first time, the influence of biofilms on single and double optical window (SOW and DOW, respectively) fast repetition rate fluorometer (FRRF) measurements of microalgal photosystem-II initial fluorescence (F0), maximum fluorescence (Fm), variable fluorescence (Fv = Fm - F0), quantum yield (Fv/Fm) and functional absorption cross section (σPSII)]. Biofilms with chlorophyll > 0.1 μg cm(-2) and > 0.

Picophytoplankton as Tracers of Environmental Forcing in a Tropical Monsoonal Bay.

In order to better understand the picophytoplankton (PP) dynamics in tropical monsoon influenced coastal regions, samples were collected daily (June-September 2008: monsoon, December 2008: post-monsoon and April 2009: pre-monsoon) from a fixed station in Dona Paula Bay, India. Eight PP abundance peaks comprising Prochlorococcus-like cells, picoeukaryotes, and three groups of Synechococcus occurred. The chlorophyll biomass and PP abundance were negatively influenced by reduced solar radiation, salinity and water transparency due to precipitation and positively influenced by the stabilized waters during precipitation break/non-monsoon periods.

Effect of chlorination on the development of marine biofilms dominated by diatoms.

This study addressed the antifouling efficiency of commercially available chlorine at different concentrations (0.5%, 1%, and 2%) and exposure times (0.5 min, 1 min, 5 min, and 15 min).

Variations in phytoplankton community in a monsoon-influenced tropical estuary.

In a monsoon-affected tropical estuary, oscillations in freshwater discharge during monsoon shifted the phytoplankton blooms from those adapted to low salinities to high salinities and vice versa. Salinity stratification during monsoon (onset and restart after an intermittent break) favored diatom (Skeletonema) bloom in low-saline surface waters. In high-saline, nutrient-rich bottom waters, Fragilariopsis (diatom) bloom was observed during onset of monsoon and persisted till the end of monsoon.

Ultraviolet radiation (UV-C): a potential tool for the control of biofouling on marine optical instruments.

In an effort to develop a tool for controlling biofouling of marine optical instruments, the efficiency of ultraviolet radiation (UVR - 254 nm) in preventing biofouling was evaluated by conducting in situ experiments at different intensities (14.7, 9.6, 7.

Biofilm diatom community structure: influence of temporal and substratum variability.

Diatoms, which are early autotrophic colonisers, are an important constituent of the biofouling community in the marine environment. The effects of substratum and temporal variations on the fouling diatom community structure in a monsoon-influenced tropical estuary were studied. Fibreglass and glass coupons were exposed every month for a period of 4 days and the diatom population sampled at 24 h intervals, over a period of 14 months.

Quantification of diatoms in biofilms: standardisation of methods.

Benthic diatoms, which often dominate marine biofilms are mostly pennate along with a few centric species that have an attached mode of life. Even though the range of diatoms in biofilms is diverse, their ecology is poorly understood because of the difficulty in sampling and enumeration. Scraping or brushing are the traditional methods used for removal of diatoms from biofilms developed on solid substrata.

Temporal variations in dimethylsulphoniopropionate and dimethyl sulphide in the Zuari estuary, Goa (India).

Despite tropical estuarine systems representing important sites for active biogeochemical processes, studies on dimethyl sulphide (DMS) in these systems are sparse. Here we report on DMS and dimethylsulphoniopropionate (DMSP) variability in relation to physicochemical and biological parameters for a period of 14 months in a tropical estuarine environment. DMS and DMSP showed high temporal variations with maximal concentrations during the southwest monsoon coinciding with a dinoflagellate bloom.