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

Abstract

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 shalloiv marine bays, owing partly to a relatively small terrigenous input and little silt, and the quantity of the parhculate organic matter primarily depended on phytoplankton productivity. The ratio chlorophyll a: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 spnng peaks were composed mainly of single diatoms and chain-forming diatoms in the size range 20 to 60 pm (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.

Influences of nutritional state and temperature on suspension-feeding rates and mechanics in the spionid polychaete Polydora cornuta

“…These algal concentrations occur naturally in coastal waters during bloom and non-bloom conditions, respectively (Lin & Hines 1994, Navarro & Thompson 1995, Hughes et al 2000, Lucas et al 2000 and these temperatures correspond to temperate-zone spring/summer and winter conditions, respectively (Vedel 1998, Hughes et al 2000, Jordana et al 2000. Each worm was conditioned separately, with its pipettor tip held upright, in a plastic container holding 4.5 l of artificial seawater and with vigorous aeration to maintain algae in suspension.…”

“…Benthic suspension feeders experience highly variable food resources in time and space (Berg & Newell 1986, Fegley et al 1992, Navarro & Thompson 1995. Because growth and reproduction are often food limited (Wilson 1985, Riisgard et al 1996, Rossi & Lardicci 2002, animals' responses to variations in food supply may be important determinants of fitness.…”

The effect of the sinking spring diatom bloom on digestive processes of the cold‐water protobranch Yoldia hyperborea

“…Because phytoplankton biomass at this latitude is highly seasonal (Navarro and Thompson 1995), benthic animals should experience a strong seasonal input of organic matter that accumulates because bacterial turnover is strongly reduced at low temperatures (Pomeroy and Deibel 1986). Hence, deposit feeders should be able to utilize the potential food source over an extended period before depleting it.…”

The effects of seasonal processes on size spectrum dynamics

“…Such environmental factors can alter abundances of plankton and (or) larger organisms, influencing the intercepts and slopes of size spectra over the year (Navarro and Thompson 1995;Mari and Burd 1998;Cózar and Echevarría 2005). The single biggest seasonal driver of variation in size spectra is the phytoplank-ton bloom that occurs at some stage during the year (Barnes et al 2011), usually in the spring, although smaller blooms can also occur in the autumn (see Truscott 1995;Findlay et al 2006).…”