مجله بین المللی زیست شناسی آبزیان
سال:1396 | دوره:5 | شماره:5 |تعداد مقالات:8

Phytoplankton of three floodplain lakes (beels) of the Majuli River Island of upper Assam, northeast India (NEI), sampled during September 2010–August 2012, revealed rich diversity (108species) with Ghotonga>Holmari ≥ Bhereki beels; richness of Chlorophyta and of Cosmarium>Staurastrum>Euastrum in particular. The monthly richness and community similarities affirmedheterogeneity in phytoplankton composition. Phytoplankton comprised between 59.5±12.5, 57.1±12.3 and 48.6±13.5% of net plankton abundance of Bhereki, Holmari and Ghotonga beels, respectively. Bacillariophyta>Chlorophyta showed quantitative importance in Bhereki whileChlorophyta>Bacillariophyta recorded importance in Holmari and Ghotonga beels. Cyanophytashowed sub-dominance and Dinophyta>Euglenophyta showed low densities in the three beels.Phytoplankton richness and abundance followed oscillating monthly variations; ANOVA registeredinsignificant richness variations amongst beels. The results are characterized certain monthly andannual variations but mean values depicted high species diversity, low dominance and highequitability. Individual and cumulative influence (vide CCA) yielded limited insight on the role ofseventeen abiotic factors on phytoplankton in Holmari and Bhereki beels.

This study presents the first record of Halodule pinifolia on the eastern coast of Sri Lanka, approximately 310 km along the coastline from the previously recorded location (Kapparathota, Weligama). Further, this study describes the new locality of the nationally endangered seagrassspecies Halophila beccarii to Valaichchenai Lagoon, 26.5 km north of Batticaloa Lagoon, where itwas previously recorded, along with the presence of two other species, Halophila ovalis and Haloduleuninervis. While the species composition the seagrass habitat of Valaichchenai Lagoon might changein the near future due to the impact of climate change, multiple threats already exist at these newlydiscovered seagrass habitats, including multiday fishing vessel movements, the collection of shellson the seagrass beds, and solid waste dumping into the lagoon. Decline of seagrass abundance inValaichchenai Lagoon would negatively impact the food security and income generation of fishers.Therefore, a well-established legislative framework and systematic long-term monitoring of seagrassin Valaichchenai Lagoon are essential in order to develop seagrass conservation plans beforepopulations decline significantly or become locally extinct.

Marine environments are continuously being threatened by a large number of pollutantsincluding heavy metals and organophosphorous pesticides from anthropogenic sources. Thesecompounds can cause a serious environmental problem. The present study aimed: (1) to measuresensitivity of acetylcholinesterase (AChE) activity to in vivo exposure to the organophosphorouschlorpyriphos-ethyl (CPF) and to the heavy metals cadmium (Cd) and copper (Cu) and (2) to use thehistopathological lesions as tissue biomarkers for biomonitoring of different contaminations. Theresults clearly showed that the AChE activity in different tissues (digestive gland, muscle and eyes)of Carcinus maenas was relatively sensitive to the concentrations of CPF and tended to have differentpatterns in response to Cd, Cu and Cu+Cd mixture exposure. The transfer of treated crabs to the cleansea water allowed to recover totally or partially the lost activity depending on selected tissues andcontaminant exposure (metals or organophosphorous compounds). Histopathological biomarkers inC. maenas exposed to different contaminants showed the presence of different lesions which alteredthe digestive gland after 7 days of contamination.