Grazing of phototrophic nanoplankton by microzooplankton in Narragansett Bay

Abstract

Daily photosynthetic nanoplankton (< l 0 pm and < 5 pm) growth rates and microzooplankton (10 to 202 pm) grazing rates were measured at weekly intervals for 1 yr using size-fractionated natural populations incubated in situ in lower Narragansett Bay. Changes in < 10 pm and < 5 pm chlorophyll a in the presence and absence of 10 to 202 pm microzooplankton were used to calculate growth and grazing rates. NH,, NO3, PO,, and Si(OH), concentrations measured within the dialysis bags before and after in situ incubations indicated that nutrient availability was adequate to meet uptake requirements during these short experiments. Chl a growth rates ranged from 0 to 2.2 doublings d-I (< 10 pm) and 0 to 2.1 doublings d-' ( < 5 pm), and increased with temperature. Microzooplankton grazing rates ranged from 0 to 2.2 pg chl a 1-' d-' ( < l 0 pm) and 0 to 2.1 pg chl a 1-' d-' ( < 5 pm).Grazing was linearly related to chl a standing stock and production in each size fraction. Annual mean microzooplankton grazing represented 62 % of < 10 pm and <S pm chl a production. Grazing impact was elevated when low temperatures limited nanoplankton production, suggesting that microzooplankton grazing contributed to seasonal variations in relative importance of different size fractions of phytoplankton in Narragansett Bay.

Seasonal niche strategy of the bloom-forming dinoflagellate Heterocapsa triquetra

“…Microzooplankton grazing rates often exceed those of macrozooplankters, particularly when water temperatures are elevated and the average cell size is <10 µm (Burkhill et al 1987, Litaker et al 1988. In contrast, during winter in temperate estuaries, microzooplankton concentrations are generally too low to graze significant numbers of phytoplankton cells, although there are exceptions to this general trend (Verity 1986, Sanders 1987, Baird & Ulanowicz 1989, Mallin 1991, Kamiyama 1994, Gallegos & Jordon 1997. The microzooplankton assemblage measured during the spatially intensive study (1997 to 1998) was dominated by tintinnids and oligotrichs.…”

Planktonic ciliates in the Baltic Sea in summer: distribution, species association and estimated grazing impact

“…Heinbokel & Beers 1979, Gast 1985, Lessard & Swift 1985, Sherr et al 1986, Verity 1986, Paranjape 1987, Sherr & Sherr 1987, Hall et al 1993, Kivi & Setälä 1995, Verity & Smetacek 1996, Johansson & Coats 2002. Nevertheless, estimates on the grazing impact or clearance capacity of a ciliate community are often based on average clearance values, regardless of average ciliate cell size, which may give biased estimates of the actual grazing capacity of the ciliate community.…”

Patterns in tintinnid species composition and abundance in relation to hydrological conditions of the southwestern Atlantic during austral spring

“…Indeed, microzooplankton grazing rates were reported to be linearly related to nanoplankton production (Verity 1986b).…”