Picoplankton carbon flux in Chesapeake Bay

Abstract

ABSTRACT-Although it is increasingly clear that picoplankton play a major role in the oceanic carbon cycle, relatively little is known concerning the significance of picoplankton in coastal systems subject to significant evironmental variance on tidal to interannual scales. Here w e report on seasonal and interannual patterns of variability in the productivity and biomass of phototrophic and heterotrophic picoplankton (P-and H-PICO, respectively) and on the flow of carbon from phytoplankton to H-PICO. Annual cycles in the biomass and productivity of both picoplankton trophic levels exhibit winter-spring minima and summer maxima but do not appear to be directly coupled in terms of carbon flow from P-to H-PICO. H-PICO exceeds P-PICO durlng sprlng when picoplankton productivity is 1 0~1 , and P-PICO exceeds H-PICO during summer when productivity is high. P-PICO productlvity and biomass increase rapidly each year to an early summer peak (20",, of total phytoplankton productlvity on average) immediately following the collapse of the spring diatom bloom. In contrast, H-PICO productivity and the abundance of bacterioplankton (the predominant group of H-PICO) increase slowly to a late summer peak (equivalent to 16 % of phytoplankton productivity on average). Recently released phytoplankton exudates are a major source of dissolved organic carbon with H-PICO taking u p an average of 54 % during spring and 8 3 ?h during summer Variations in H-PICO are closely coupled to the release of DOC, most of which is produced by phytoplankton > 2 pm. New nutrient input to the Bay appears to be coupled to H-PICO productivity \rla increases in the productlvlty and DOC release of phytoplankton > 2 pm in slze.

Seasonal and regional variations in plankton community production and respiration for Chesapeake Bay

“…At least for the well-documented mesohaline region of the Bay, it is during this tune that the annual transition from a spring bloom of large diatoms to a summer assemblage of smaller flagellated cells occurs (Sellner 1987, Malone et al 1988). Also at this time, pico-and nanoplankton increase to become substantial contributors of phytoplankton primary production (McCarthy et al 1984, Malone et al 1991) and it appears that a large fraction of organic production is shunted through the microbial loop (Jonas & Tuttle 1990, Malone et al 1991, Ducklow & Shiah 1993. At the LB station, the decline in diel plankton community metabolism to heterotrophy observed in June (Fig.…”

Long-term trends in the distribution of phytoplankton in Chesapeake Bay: roles of light, nutrients and streamflow

“…From May to early June, a pronounced floral shift from a high biomass, microplankton community dominated by diatoms to a high productivity, pico-nanoplankton community dominated by a mixed, non-diatom flora has been discussed in the context of the seasonal phase relationship between biomass and productivity (Malone et al 1988(Malone et al , 1991. The regeneration of nutrients accompanying the breakdown of spring bloom-derived material drives an annual productivity maximum in summer, as reviewed by Malone (1992).…”

“…EPA 1983); (2) the size structure of Bay phytoplankton has shifted toward a community with abundant picoplankton and nanoplankton (McCarthy et al 1974, Van Valkenburg & Flemer 1974, Sellner & Kachur 1987, Verity 1988, Malone et al 1991, Malone 1992; (3) the species composition has changed from an assemblage consisting of irnrnotile, centric diatoms to one predominantly composed of flagellated species (see Wolfe et al 1926, Cowles 1930, Morse 1947, Patten et al 1963, Mulford 1972, Marshal1 & Lacouture 1986. Potential ecological consequences of these changes include: (1) a change in trophic structure from a diatom-zooplankton-fish food chain to a system characterized by a major 'microbial loop' (Verity 1988); (2) an increase in particulate organic material (POM) derived from the eutrophicationdriven increase in algal biomass that supports high rates of microbial decomposition and exacerbates summer oxygen depletion; (3) shading of submerged aquatic vegetation by the reduced clanty of the water caused by increased abundance of phytoplankton in the water column.…”

Modeling the seasonal autochthonous sources of dissolved organic carbon and nitrogen in the upper Chesapeake Bay

“…DOM can also potentially form gels that may aggregate to form particulate organic matter (POC) (Verdugo et al, 2004) which may sink out of surface waters. As in other temperate systems, the rate and magnitude of these sources and sinks varies on a seasonal basis as changes in light, temperature, and freshwater flow affect the environment (Apple et al, 2006;Bronk et al, 1998;Jonas and Tuttle, 1990;Lomas et al, 2002;Malone et al, 1991;Mulholland et al, 2003;Shiah and Ducklow, 1994b;Wommack et al, 1992).…”