Type of suspended clay influences zooplankton response to phosphorus loading

Abstract

The effects on zooplankton community structure of P loading and two different kinds of suspended sediments were tested in a small lake. Limnocorrals were used in a complete, triplicated, sixtreatment-block design. Treatments were loading with P, kaolinitic clay (IQ, K+P, montmorillonitic clay (M), and M+P plus a control without additions. P fertilization caused blooms of blue-green bacteria and resulted in reductions of the dominant copepod (Diaptomus mississippiensis) and cladocerans (Diaphanosoma brachyurum, Bosmina longirostris, and Ceriodaphnia reticulata), while causing a 5-fold increase in rotifers (mostly Keratella cochlearis). Zooplankton in the K and K+P treatments were similar to the control, but cladoceran species other than Diaphanosoma were reduced. M was more detrimental to zooplankton than K, causing a lo-fold decrease for all crustaceans. We attribute this in part to lower algal densities in the A4 treatment. Simultaneous P loading mitigated the effects of M on Diaphanosoma, rotifers, and copepods and may involve a transfer loop in which dissolved organic C adsorbed on clay becomes available to filter-feeding zooplankton. The effects of mineral turbidity apparently cascaded up the food chain, with both kinds of clays reducing densities of Chaoborus larvae.

Suspended Clays Alter Trophic Interactions in the Plankton

“…These levels of P and clay loading were the same as those used in a study conducted the previous year, which resulted in a high population of the cladoceran zooplankter Diaphanosoma (Cuker and Hudson, 1992). Subsequently, a phosphorus loading rate of 3.3 mg·m-2 ·d-1 (0.035 ~mol·L-1 ·d-1 ) and a clay loading rate of 100 g·m-2 ·d-1 (33.1 mg·L-1 ·d-1 ) were maintained throughout the experiment by twice-weekly batch additions.…”

“…I originally hypothesized that mineral turbidity would release the crustacean zooplankton from predation by fish, resulting in a community dominated by clay-tolerant taxa such as Diaphanosoma and Diaptomus (Geddes 1984, Threlkeld 1986, Hart 1988, Koenings et al 1990, Cuker and Hudson, 1992. This is done through experimental manipulation ofzooplanktivorous fish and turbidity from suspended clays.…”

Influence of suspended clay on phosphorus uptake by periphyton

“…Table 1 lists several studies involving suspended sediment along with the type and concentration used in natural and experimental systems. Suspended clays shifted phytoplankton and zooplankton species in responses to SRP, montmorillonite, and kaolinite clay loadings in lentic systems (Cuker & Hudson, 1992;Cuker et al, 1990). Burkholder & Cuker (1991) found increases in periphyton growth when suspended clay was combined with SRP amendments in a lake mesocosm.…”

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“…In addition, the low density of filter feeding zooplankton can be the consequence of elevated pH (Jeppesen et al 1990), since most, particularly small cladocerans, i.e., B. longirostris (Hansen et al, 1991) and C. quadrangula (O'Brien and De Noyelles, 1972), are noted to suffer from pH values approaching 10. The role of a dominant cladoceran in cyanophyte plagued Kirkkojärvi basin indicates that D. brachyurum, besides being better adapted to mineral turbidity than other crustacean zooplankters (Hart, 1988;Koenings et al, 1990;Schuman, 1990) and able to utilize organically enriched, suspended clay as food resource (Cuker and Hudson, 1992), is comparatively tolerant to the mechani-cal inhibition by filamentous algae. The role of a dominant cladoceran in cyanophyte plagued Kirkkojärvi basin indicates that D. brachyurum, besides being better adapted to mineral turbidity than other crustacean zooplankters (Hart, 1988;Koenings et al, 1990;Schuman, 1990) and able to utilize organically enriched, suspended clay as food resource (Cuker and Hudson, 1992), is comparatively tolerant to the mechani-cal inhibition by filamentous algae.…”