MEPS 125:95-106 (1995)  -  doi:10.3354/meps125095

Seasonal fluctuations in the size spectra, biochemical composition and nutritive value of the seston available to a suspension-feeding bivalve in a subarctic environment

Navarro JM, Thompson RJ

Seasonal changes in the size spectrum and biochemical composition of the suspended particulate matter were recorded for 2 yr in Logy Bay, southeast Newfoundland, Canada. The seston load was lower than in many shallow marine bays, owing partly to a relatively small terrigenous input and little silt, and the quantity of the particulate organic matter primarily depended on phytoplankton productivity. The ratio chlorophylla:phaeopigments was high during the phytoplankton bloom, due to the living nature of the organic seston at this time, compared with the rest of the year, when lower values were associated with the highly degraded suspended material. The size-frequency distribution of the suspended particulate matter reflected the succession of the phytoplankton community throughout the year. The spring peaks were composed mainly of single diatoms and chain-forming diatoms in the size range 20 to 60 um (equivalent spherical diameter). Variations in carbohydrate, lipid and protein in the seston were primarily associated with the periods of high and low standing stocks of phytoplankton observed in this environment. The seasonal trends were very similar for each biochemical component, and values were highly correlated with those for other properties of the seston, such as organic matter, chlorophyll a and particulate organic carbon and nitrogen. The nutritional quality of the seston was expressed by a food index, calculated as the ratio of food material (protein + carbohydrate + lipid) to total seston. This index followed the cycle of the phytoplankton bloom, with maximum values during spring and summer, and much lower values during winter. The results suggest that the gross analysis of the suspended particulate matter or the measurement of a single chemical variable cannot describe fully the nutritive value of the seston to a suspension-feeder. An analysis of the size spectrum and biochemical composition of the material is required for this purpose.


Seston . Phytoplankton bloom . Suspension-feeding . Cold ocean


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