Temporal variability in the biochemical composition of sedimentary organic matter in an intertidal flat of the Galician coast (NW Spain)

Abstract

Temporal variations and spatial distribution of sedimentary organic matter composition were investigated over a one year period in an intertidal flat of the NW Spain. Sediment samples were collected from 0 to 25 cm depth, every three months, from January 1997 to January 1998 at three tidal levels (high, medium and low). Changes in the elemental and biochemical composition were assessed to gather information on temporal and spatial fluctuations in quantity and quality of sedimentary organic matter potentially available to benthic deposit-feeder nutrition. Organic matter content was significantly higher at the medium tidal level, while minimum values were found at the high tidal level. The different biochemical classes of organic compounds exhibited different temporal patterns. Carbohydrate and lipid concentrations decreased with sediment depth. The biopolymeric fraction of organic carbon (i.e. the sum of lipid, carbohydrate and protein carbon) was dominated by proteins (61%), followed by lipids (26%) and carbohydrates (14%). Biopolymeric carbon accounted for only a small fraction (37% on average) of the total organic carbon. Refractory organic carbon (i.e. non biopolymeric) accounted for 50 to 80% of the total organic carbon and it tended to be buried into deeper sediment layers. The nutritional quality of the sedimentary organic matter, expressed as the biopolymeric carbon to total organic carbon ratio, was higher in January 1997, when also the higher protein to carbohydrate ratio values were observed and related to the presence of newly-produced organic matter. Low biopolymeric carbon to total organic carbon ratio and protein to carbohydrate ratio were recorded during the rest of the year, indicating a low-quality and aged organic matter. Results of the present study revealed an inverse relationship between the overall amount of organic matter and its potential availability to consumers.

Core sediment biogeochemistry in specific zones of Cochin Estuarine System (CES)

“…Protein-carbohydrate ratio (PRT:CHO) is used as an index to evaluate the origin of material present in sediments and to determine the age of sedimentary organic matter (Cividanes et al 2002). This ratio was generally higher in estuarine sediments which point to the presence of low dead organic matter accumulation, probably due to the vibrant condition of estuaries.…”

Variation in food sources of the macrobenthos along a land–sea transect: a stable isotope study

“…Because TOM is usually rich in refractory compounds such as cellulose and lignin, its nutritional value for coastal animals is considered to be small (Cividanes et al 2002). Taking into account the considerable distance from the fish farm (> 3 km) and the dispersal range of aquaculturederived particulate organic matter (< 300 m from the fish cage, Yokoyama et al 2006), such organic matter appears not to be used by intertidal animals directly.…”

Isotopic evidence for phytoplankton as a major food source for macrobenthos on an intertidal sandflat in Ariake Sound, Japan

“…In general, terrestrial vascular plants contain large amounts of refractory compounds such as cellulose and lignin, which do not rapidly biodegrade, resulting in their accumulation in estuarine sediments. Most sedimentary organic matter is therefore of low nutritional value and not directly assimilable by benthic consumers (Cividanes et al 2002). Kimura et al (2002) assayed enzyme activities in a congeneric species of Nihonotrypaea japonica, N. harmandi, inhabiting sandflats in the outer part of Ariake Sound and suggested that labile, low-molecular-weight nitrogenous compounds in sediments serve as a principal source of nitrogen for this species.…”