Changes in phytoplankton and zooplankton biomass and composition reflected by sedimentation

Abstract

Eight 2-week limnocorral (LC) experiments were performed in Lake Lucerne, Switzerland, during 1982Switzerland, during -1984 to study the effects of biomanipulation. The large zooplankton were removed by 95-pm plankton nets in some LCs and different phosphorus fertilization regimes were applied. The chlorophyll a and sestonic POC and PP concentrations decreased significantly in the presence of crustacean zooplankton, whereas algal biomass was 'less affected. Within the short period of 2 weeks this "top-down" regulation seemed to be balanced by "bottom-up" control, because phosphate fertilization and favorable light conditions stimulated phytoplankton production and increased seston concentrations. The significant shift from nanoplankton to net plankton in both the filtered and control LCs, which caused the sedimentation rates to increase during all the experiments, could not be attributed solely to selective zooplankton grazing but was also induced by different algal nutrient strategies. In the control (unfiltered) LCs, the herbivorous crustaceans (usually ~80% Daphnia spp.) increased POC and PP sedimentation by 14-50 and 25-57% due to fecal pellet production.

Formation of macroscopic organic aggregates (lake snow) in a large lake: The significance of transparent exopolymer particles, plankton, and zooplankton

“…As in marine systems, it has been demonstrated that larger particles contribute more to the sinking flux than do smaller particles (Bloesch and Burgi 1989;Weilenmann et al 1989). However, only recently macroscopic organic aggregates have been described in a lake (Grossart and Simon 1993;Grossart 1995).…”

Impact of planktonic food web structure on nutrient retention and loss from a late summer pelagic system in the coastal northern Baltic Sea

“…Lynch & Shapiro 1981, Hessen et al 1986, Horstedt et al 1988, Mazumder et al 1988. Consequently, sedimentary losses of particulate nutrients tend to increase due to the higher sinking velocities of larger cells (Bloesch & Burgi 1989, Mazumder et al 1989 and Increased contribution of zooplankton fecal material to the settling flux (Bloesch & Burgi 1989). Addition of visually feeding planktivorous fish reduces the numbers of larger herbivores, and leads to a biomass increase of nanoplankton, generally favored by zooplankton grazers (Hessen et al 1986, Mazumder et al 1988, Drenner et al 1989, as well as to a subsequent decline of sedimentation rates and retention of nutrients in the pelagic system (Mazumder et al 1992).…”

Brine shrimp grazing and fecal production increase sedimentation to the deep brine layer (monimolimnion) of Great Salt Lake, Utah

“…Many studies in both marine and freshwater have found that zooplankton decreases the vertical flux of nutrients and organic matter (e.g., Bathmann et al, 1987;Ayukai & Hattori, 1992;Sarnelle, 1999;Yoshimizu & Urabe, 2002), which has been attributed to a high grazing rate of zooplankton on fecal material, the production of bacteria associated with zooplankton activity, and a high primary production. Other studies have reported an opposite relationship (Honjo & Roman, 1978;Bloesch & Bürgi, 1989;Andreassen et al, 1996;Pilati & Wurtsbaugh, 2003;Pitsch et al, 2012), which is mainly attributed to the presence of a great number of large zooplankton taxa, which produce fecal pellets that sink quickly and resist decomposition (e.g., copepods and euphausiids, Wotton & Malmqvist, 2001). Surprisingly, there have been only a few studies on the effects of zooplankton on the vertical particulate flux in saline lakes (Jellison et al, 1993, Jellison & Melack, 2001) and ponds (Bruce & Imberger, 2009), despite the fact that salinity (density) might have a large (direct and indirect) influence on sedimentation rates.…”