Variability of nutrients and phytoplankton biomass in a shallow brackish water ecosystem (Chilika Lagoon, India)

Abstract

Seasonal and spatial variations in water quality parameters, such as nutrients [NH 4 ? -N, NO 2 --N, NO 3 --N, PO 4 3--P, total nitrogen (TN) and total phosphorus (TP)], Secchi disc depth, salinity, dissolved oxygen, chlorophyll a, primary productivity and phytoplankton standing stock, were studied in Chilika Lagoon (from 27 sampling locations) during 2001-2003 to assess the present ecological status. The study was undertaken after a major hydrological intervention in September 2000, which connected the lagoon body and the Bay of Bengal via a manmade opening (new mouth). Current and old data on water quality were also compared to establish the changes that had occurred after the hydrological intervention. Multivariate techniques and gridding methods were used to investigate the spatial and seasonal variability of the data and to characterize the trophic evolution of the basin. Results of principal component analysis (PCA) indicated that the 27 stations can be classified into five groups based on similarities in the temporal variation of nutrients, chlorophyll a concentration, salinity, and other physicochemical parameters. The tributaries and the exchange of lagoon water with the Bay of Bengal most probably determine the water quality and the dynamics of the ecosystem. Hydrodynamics of the lagoon, weed coverage, input of urban sewage through tributaries and agricultural runoff are probably the key factors controlling the trophic conditions of the lagoon. An increase in salinity and total phosphorus was noted after the new mouth was opened, while the total suspended sediment load, the water column depth, and nitrogenous nutrients decreased. The new mouth opening also brought changes in the phytoplankton species composition.

Influence of Monsoon on Macrobenthic Assemblage in Outer Channel Area of Chilika Lagoon, East Coast of India

“…The Chilika wetland ecosystem is one of such wetland where unique assemblage of marine, brackish water and fresh water ecosystem is seen. It is located on the east coast of India and regarded as the largest tropical brackish water lagoon in Asia (Panigrahi 2009;CDA 2008). This lagoon is enriched with high fisheries resource that supports the livelihood of fisher folk, for a population more than 2 lakhs (CDA 2008).…”

“…Naming a few Bhattacharya et al, 1994;Panigrahy (2000); Chandramohan and Nayak,(1994) have enumerated the geology, geomorphology and tidal variation in the lagoon. Panda et al, (2006) have studied the distribution of trace metals in the surficial sediment, while Sahu and Adhikary, (1999) and Shaw et al, (2000) elucidated the distribution of seaweed and macrophytes, Panigrahy(1985); Panigrahi (2006Panigrahi ( ,2007Panigrahi ( ,2009) have described for phytoplankton and primary productivity potentiality of the lagoon where as Nayak et al, (2004) ;Panigrahi, (2009) and Mohapatra et al, (2007) studied the water chemistry and fishery production of the lake and the works of Zoological Survey of India regarding fauna of Chilika lake (ZSI 1995). Perusal of the literature has suggested that attention towards the study of macrobenthic organisms in the Chilika lake is still scarce.…”

Exploring the seasonal dynamics within the benthic foraminiferal biocoenosis in a tropical monsoon-influenced coastal lagoon

“…In the present study, we did not encounter any live specimens beyond 4 cm, with the majority of the density restricted to the surface 0−2 cm fractions in most of the samples. The studied environment of Chilika lagoon has previously been reported to be under seasonal influence due to the southwestern monsoon-induced precipitation and freshwater influx from the Ma hanadi basin (Panigrahi et al 2009, Srichandran et al 2015a. During the study period, the maximum precipitation was observed during the months of July−October, which corresponds to the monsoon season in the region.…”

“…Nutrient dynamics observed in this shallow (< 2 m) water body are influenced by monsoonal precipitation (Nayak & Behera 2004, Panigrahi et al 2009), along with physiological factors and carbon dynamics (Muduli et al 2012(Muduli et al , 2013. Previous studies of the lagoon have identified seasonal variations within the phytoplankton (Panigrahi et al 2009, Srichandan et al 2015a) and zooplankton (Naik et al 2008) communities of the water column; however, studies investigating seasonal patterning within the benthic bottom-dwelling communities are not available. Previous reports on the diversity of benthic foraminifers from this lagoon have reported extremely low values (Jayalakshmy & Rao 2001, Kumar et al 2015.…”

“…The majority of the freshwater influx originates from the unregulated drainage of the western catchment and from the distributaries of the Mahanadi River basin that meet the lagoon in its northern fringes. The lagoon is bordered on its northern and eastern sides by a catchment region of 4406 km 2 , which provides an additional source of freshwater inflow (Panigrahi et al 2009). The lagoon is separated from the Bay of Bengal by a sand bar approximately 60 km long bearing 3 openings, of which 2 were naturally formed in 2008 and 2012 (Sahu et al 2014), alongside an artificially dredged inlet opened in 2001.…”