Patterns of microzooplankton growth in dilution experiments across a trophic gradient: Implications for herbivory studies |
| |
Authors: | Matthew R First Peter J Lavrentyev Frank J Jochem |
| |
Institution: | (1) Department of Biology, The University of Akron, Akron, OH 44325-3908, USA;(2) Marine Biology Program, Florida International University, 3000 NE 151 Street, North Miami, FL 33181, USA;(3) Present address: Department of Marine Sciences, Marine Science Building, University of Georgia, Athens, GA 30602-3636, USA |
| |
Abstract: | To investigate the growth and grazing patterns of microzooplankton (MZP) in environments of differing productivity, dilution
experiments measuring phytoplankton growth (μ) and grazing mortality (m) rates were performed using samples from contrasting
locations along the Texas coast. Samples were collected from estuaries, coastal lagoons and offshore Gulf of Mexico locations
in the spring and summer of 2001. MZP growth rates were determined in each dilution treatment. Although MZP biomass changed
over time in most dilution treatments, adjusting μ and m for the actual grazer gradient (represented by geometric mean MZP
biomass) did not cause a significant deviation from the nominal dilution gradient. Likewise, these adjustments did not yield
significant regressions where none existed before adjustment. The dynamics of MZP taxonomic groups (ciliates, dinoflagellates)
and size categories differed suggesting that in some cases internal predation may lead to trophic cascades. MZP biomass was
higher in productive coastal waters and included a larger proportion of dinoflagellates than in the oligotrophic, ciliate-dominated
waters of the Gulf of Mexico. The MZP biomass-to-chlorophyll a ratio was lowest in the hypereutrophic Nueces River, where MZP biomass significantly increased in all dilution treatments
(net growth rates up to 2 day−1) suggesting a strong top–down control. In the brown-tide dominated Upper Laguna Madre and the oligotrophic seagrass-dominated
Lower Laguna Madre MZP growth was decoupled from that of phytoplankton. At these sites, MZP were likely fueled by bacterial
carbon and mixotrophy, respectively. Observing the growth response of MZP in dilution experiments can provide insight into
trophic structure and efficiency of the microbial food web. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|