Microbial food web interactions in two Long Island embayments

Abstract

Phytoplankton mortality (herbivory) and bacterivory were examined experimentally in West Neck Bay and Coecles Harbor, Long Island, NY, from April through September 1998. Small algae (< 5 µm diameter) dominated phytoplankton communities in both ecosystems throughout much of the summer, and most microzooplankton (< 200 µm) were also small (< 40 µm) for that category. Generally, plankton abundances were indicative of eutrophic ecosystems. Oscillations in standing stocks and mortality of prey indicated tight coupling of growth and grazing mortality in both bays. Phytoplankton mortality rates accounted for the removal of 14 to 65% of total phytoplankton standing stocks daily, while bacterivory accounted for the removal of 14 to 88% of total bacterial standing stocks daily. Carbon consumption was estimated from phytoplankton and bacterial removal rates and from conversion to carbon from chlorophyll (phytoplankton) or cell number (bacteria). These calculations indicated that carbon consumption due to bacterivory constituted an average of 21 and 47% of carbon consumption due to herbivory in West Neck Bay and Coecles Harbor, respectively. Total carbon consumption (bacterivory + herbivory) revealed high energy flux through the nano-and microzooplankton assemblages of these estuarine environments.KEY WORDS: Bacterivory · Herbivory · Microbial ecology · Bacteria · Phytoplankton · Zooplankton · Protozoa · Long Island Bays · Peconic Bay · Estuary Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 26: [139][140][141][142][143][144][145][146][147][148][149][150][151][152][153][154][155] 2001 caused by a picoplanktonic pelagophyte, Aureococcus anophagefferens (Cosper et al. 1987, Bricelj & Lonsdale 1997. Eutrophic WNB has repeatedly experienced high abundances of A. anophagefferens, typically in June or July. In contrast, the appearance of brown tides in CH has occurred only occasionally during the past 15 yr when A. anophagefferens cells have reached bloom abundances throughout the entire Peconic Estuary System (SCDHS 1988, Nuzzi & Waters 1989, Nuzzi 1995.The dominance of the phytoplankton community by small algae in Long Island bays implies an important role for microbial consumers as conduits for carbon, energy and nutrient flow in these estuaries. The size range of much of the algal community in WNB and CH is below the optimal range for particle capture by mesozooplankton (Nival & Nival 1976, Bartram 1980. Accordingly, studies in the Peconic Estuary System during 1988-89 observed that grazers > 64 µm in size did not contribute substantially to phytoplankton mortality during times when small algae comprised high percentages of the phytoplankton biomass (Kim 1993). Lonsdale et al. (1996) further showed that copepods depended on ciliate prey when picoplanktonic algae dominated the phytoplankton community in WNB. These observations support the supposition that phagotrophic protistan assemblages play a major role in the removal of phytoplankton production in Long Island ba...

Microbial herbivory on the brown tide alga, Aureococcus anophagefferens: results from natural ecosystems, mesocosms and laboratory experiments

“…The role of pelagic microbial consumers in the mortality of A. anophagefferens has been examined in a few studies (Caron et al, 1989;Mehran, 1996;Boissonneault-Cellineri et al, 2001). The results of these studies indicated that populations of the brown tide alga are consumed in the plankton, but the significance of these losses relative to the rates of removal of other phytoplankton species is still poorly characterized.…”

Bacterioplankton dynamics in the York River estuary: primary influence of temperature and freshwater inputs

“…Topdown controls such as grazing are thought to set limits on bacterial biomass and abundance (Billen 1990, Boissonneault-Cellineri et al 2001, while limits on bacterial growth rates are thought to be set by bottomup factors such as substrate supply and temperature (White et al 1991, Shiah & Ducklow 1994, Revilla et al 2000. These factors are influenced by physical processes such as freshwater flow, light intensity, storm frequency, circulation effects and other physical processes (Day et al 1989) and may vary seasonally in an estuary.…”

Influence of suspension-feeding bivalves on the pelagic food webs of shallow, coastal embayments

“…Microzooplankton are significant grazers of phytoplankton in Long Island estuaries and elsewhere (Lonsdale et al 1996, Boissonneault-Cellineri et al 2001, Deonarine et al 2006. Summarizing data from the literature on rates of growth of oceanic phytoplankton and microzooplankton grazing determined from dilution experiments, Calbet & Landry (2004) found that, on average, microzooplankton consumed 67% of phytoplankton growth on a daily basis.…”

“…in coastal systems has been associated with eutrophication and poor growth in bivalves (Grizzle et al 2001). In the absence of historically high abundances of benthic suspension-feeders in these bays, the primary consumers of these small cells are protists such as nanoflagellates and ciliates (mostly < 40 µm in cell diameter; Boissonneault-Cellineri et al 2001).…”