Osman, R. W. Academy of Natural Sciences, osman@acnatsci.org
Sanders, J. G. Academy of Natural Sciences, jsanders@acnatsci.org
Breitburg, D. L. Academy of Natural Sciences, breit@acnatsci.org
Bundy, M. H. Academy of Natural Sciences, bundy@acnatsci.org
Riedel, G. F. Academy of Natural Sciences, friedel@acnatsci.org
Seitzinger, S. P. Rutgers University, sybil@imcs.rutgers.edu
Gilmour, C. C. Academy of Natural Sciences, gilmour@acnatsci.org

 
EFFECTS OF MULTIPLE STRESSES ON ESTUARINE ECOSYSTEM DYNAMICS IN LARGE-SCALE FIELD ENCLOSURES: A COMPARISON TO MESOCOSMS
 
The effects on an estuarine ecosystem of nutrients and toxic trace metals were examined using 3.3 m diameter enclosures sunk into the natural bottom of the Patuxent River estuary. Each replicate enclosed a 1-2 m water column which varied tidally. All water exchange with the river was through 35 um plankton netting. Fish and epibenthic invertebrates were removed prior to the study and replaced by representative species. A small oyster reef with representative fauna and 25 cm diameter mud cores with 100 clams were added to each enclosure. Treatments with nutrients (P, N) and/or metals (Cu, As, Cd) continuously added were contrasted to control treatments and treatments that received excessive numbers (blooms) of sea nettles or oysters. Experiments were conducted in 1997 and 1998 and were run for 2 months and results were similar to those in mesocosm studies in which trophic complexity was also manipulated. Phytoplankton and bacterial production increased with nutrient additions and phytoplankton abundance and species composition were influenced by both nutrient and metal additions. These changes caused differences in clams, oysters, zooplankton, and fish which feed directly on phytoplankton, but not on higher levels (e.g. some fish). Blooms of sea nettles and oysters had marginal effects.
 
Day: Thursday, Feb. 4
Time: 04:00 - 04:15pm
Location: Hilton of Santa Fe
 
Code: SS51TH0400E