Biogeochemistry of surficial sediments in the intertidal systems of a tropical environment

Abstract

Variability of nature and composition of organic matter in the surficial sediments of mangrove and estuarine systems of Cochin were investigated. Assessment of biochemical composition and elements such as carbon, nitrogen and sulphur were employed for this. Irrespective of the higher content of total organic matter, the labile organic matter was very low in both mangrove and estuarine sediments. Concentrations of biochemical compounds were comparatively higher in mangrove sediments. Total lipids were the dominant class among labile organic compounds in both mangrove and estuarine sediments contributing 51.4% and 45.3%, respectively. Protein to carbohydrate ratio was higher in estuarine sediments when compared to mangroves, indicating low dead organic matter accumulation, probably due to the strong hydrodynamic conditions in estuaries. Correlation analysis showed that sediment texture had no significant correlation with any of the sedimentary parameters in mangroves, whereas in estuaries, it showed significant correlations with most of the sedimentary parameters. Principal component analysis indicated three different dominant processes in mangroves namely mangrove litter addition, diagenesis and other geochemical process like siltation and sorption/desorption, while in estuaries the dominant process seems to be diagenesis.

Fate and source distribution of organic constituents in a river-dominated tropical estuary

“…During the investigation, TOC levels were high in the riverine (S1, S2, S3) and industrial zones (S12, S14, S15), on account of the transport of allochthonous material via terrestrial run-off (Martin et al 2010;Gireeshkumar et al 2012;Renjith et al 2012). Surficial sediments of the CES recorded a moderate level of TOC comparable to previous studies (Balachandran et al 2005;Joseph et al 2008;Martin et al 2010;Deepulal et al 2012;Gireeshkumar et al 2012;Renjith et al 2012;Akhil et al 2013). Organic matter constitutes an integral part of aquatic sediments and its distribution pattern in the study region was noted to be governed by the in situ primary production, supply rate of terrestrial materials, deposition rate and texture of the sediments.…”

“…Bulk geochemical parameters are available for the evaluation of OM sources and its fate within marine sediments, including biochemical composition, elemental and stable isotope ratios. Biochemical composition serves not only as a valid methodology to determine the origin of organic matter (Colombo et al 1996), but also as a useful tool to evaluate the nutritional quality of organic materials as available food for benthic consumer organisms (Dell'Anno et al 2000;Rossi et al 2001;Rossi and Lardicci 2002;Cividanes et al 2002;Joseph et al 2008). Composition of OM in sediments has been recognized as the major factor affecting metabolism, distribution and dynamics of benthic organisms (Grant and Hargrave 1987;Graf 1989;Duineveld et al 1997) and has been widely employed to evaluate the trophic state of both marine and estuarine ecosystems (Cloern 2001;Renjith et al 2012;Akhil et al 2013).…”

Phosphorus fractions in the surface sediments of three mangrove systems of southwest coast of India

“…Phytate is relatively stable as it can be strongly adsorbed onto iron hydroxide and multivalent cations (De Groot and Golterman 1993). Irrespective of the higher content of total organic matter, the labile fraction was very low in these mangrove sediments, signalling to the dead organic matter accumulation (Joseph et al 2008). This might result in the higher concentration of Alk-OP, which is non-bioavailable.…”

Sewage contamination in a tropical coastal area (São Sebastião Channel, SP, Brazil)

“…Thirty-three sediment sampling stations were positioned along three main areas of the study site, where samples were collected Joseph et al (2008). The study area was divided into three sampling areas according to the previous knowledge about pollution sources (Medeiros and Bícego, 2004): I (north, sites 1 to 10), Caraguatatuba Bay and the northwest coast of the São Sebastião Island; area II (central, sites 11 to 20 and 33), TEBAR, urban sewage and São Sebastião Harbour; and area III (south, sites 21 to 30 and 32), SW coastal of the São Sebastião Island.…”