Recruitment Potential of a Green Alga Ulva flexuosa Wulfen Dark Preserved Zoospore and Its Development

The recruitment potential and the ability of Ulva flexuosa Wulfen zoospores to survive darkness were tested under different conditions in the present study. The dark preserved zoospore was cultured under a two-factor experimental design to test the effect of salinity and nitrate, effect of salinity and phosphate, effect of light and salinity, and effect of light and phosphate. The recruitment (germination and growth) of zoospores was significantly affected by light and salinity. The nitrate concentration of 20 µmol.l−1 was found to initiate the process of germination and its subsequent growth and, its effect appeared greatest under 25 psu condition. While nitrate enhances the growth of biomass more than phosphate, both show a positive interactive effect on biomass increase when crossed with salinity. The combined effect of 25 psu salinity and 8 µmol.l−1 phosphate exhibited higher biomass growth. There was a significant effect of light and salinity on the biomass of zoospore, though there was no significant interaction between the two factors. There was an increase in biomass of growing zoospores to increase in light intensity and 80 µmol.m−2.s−1 of light intensity was considered optimal. Similarly, high light intensity condition favored higher biomass growth and there was significant interaction between light (80 µmol. m−2. s−1) and phosphate (4 µmol. l−1) in high salinity (35 psu) condition. The result of this study showed that dark preserved zoospores of U. flexuosa have the potential for recruitment and it gives us an understanding how different factors play a role in the process of recruitment

Effect of habitat attributes on the abundance of Sargassum’s epifauna and the feeding habit of an amphipod epifauna from the coast of Western India

432-439The Sargassum bed along the rocky intertidal region is highly productive and serves as a habitat for numerous associated species. In this study, the effect of habitat attributes (algal morphology) on the abundance and diversity of epifauna in Sargassum tenerrimum was investigated. Qualitative and quantitative analysis showed that the overall species diversity was high, and Hyale nuda, Gammaropsis sp. and Modiolus adriaticus were the most abundant epifaunal species observed. The abundance of epifauna varied significantly with time. Compared to pre-monsoon months (February to May), post-monsoon (October to January) had a greater diversity of S. tenerrimum associated epifauna. The diversity was particularly high in the month of November. Epifauna showed a positive correlation with the characteristic of algal morphology, indicating its influence on abundance and diversity. Hyale nuda being the most ubiquitous and abundant epifauna observed, the biotic interaction between S. tenerrimum and H. nuda was studied further. Close examination of the gut contents of H. nuda revealed that they graze and consume the epiphytic microalgae of S. tenerrimum, instead of the macroalgal fronds. This suggests that through this relationship, epibiosis in Sargassum may remain in control, while the amphipod derives food, shelter and protection from the predators

Provenance and tectonic setting of Miocene siliciclastic sediments, Sibuti formation, northwestern Borneo

Provenance and tectonic setting of sandstone and mudstone units of the Miocene Sibuti Formation from northwest Borneo have been studied based on the mineralogy, major and trace element geochemistry data. The X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) data revealed that the sandstones and mudstones were abundant in quartz, pyrite, clay, and heavy minerals such as zircon, rutile, and some detrital cassiterite. Geochemically, the sandstones and mudstones are classified into quartz arenite, litharenite, sublitharenite, arkose, and wacke. Quartz arenites are enriched with SiO2, Zr, and Th and depleted in Al2O3, CaO, and other elements compared to other sandstone types, indicating high maturity and intensive weathering. Chemical index of alteration (CIA: 77–90), plagioclase index of alteration (PIA: 86–100), and A-CN-K diagram suggest intense weathering in the source area. Elemental ratios such as La/Sc, Th/Sc, Cr/Th, La/Co, and Th/Co are similar to sediments derived from the felsic rocks. Also, the provenance discrimination diagrams suggest recycled continental nature of these clastic sediments which are mostly derived from metasedimentary source (Rajang Formation). Discriminant-function diagram for the tectonic discrimination of siliciclastic sediments revealed that the sediments of Sibuti Formation were derived from a collision zone, which is consistent with the geology of the study area