Microcosm trophic structure. Trophic structure modifications by planktivorous fish in aquatic microcosms. [Gambusia affinis]

Technical Report · Tue Feb 01 04:00:00 EST 1977

OSTI ID:7323033

Jassby, A; Rees, J; Dudzik, M; Levy, D; Lapan, E; Harte, J

Two of 4 replicate 700-liter aquatic microcosms each were stocked with 2 mosquito fish (Gambusia affinis). The dominant zooplankter shifted from the large cladoceran Simocephalus vetulus to the smaller Alona guttata. The subsequent release of grazing pressure resulted in a rise in both phytoplankton and bacteria levels, which in turn were responsible for an increased rotifer biomass. Particulate organic carbon was higher and dissolved inorganic nitrogen was lower in the presence of Gambusia, reflecting a net shift of nutrients from inorganic to organic form, presumably because of smaller zooplankton respiratory losses. Ratios of particulate to dissolved organic carbon and of phytoplankton carbon to chlorophyll a were unnaturally high in the microcosms containing fish. An increase in total nitrogen was deduced for all 4 systems during the experiment; the increase could be explained by the presence of heterocystous Anabaena sp. and was independent of the presence of fish.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 7323033
• Report Number(s): LBL-5978
• Country of Publication: United States
• Language: English

Related Subjects

520100* -- Environment
Aquatic-- Basic Studies-- (-1989)
54 ENVIRONMENTAL SCIENCES
ANIMALS
AQUATIC ECOSYSTEMS
AQUATIC ORGANISMS
ARTHROPODS
BACTERIA
BIOMASS
CARBON
CARBOXYLIC ACIDS
CHLOROPHYLL
CRUSTACEANS
CRYOGENIC FLUIDS
ECOSYSTEMS
ELEMENTS
ENERGY SOURCES
FISHES
FLUIDS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INVERTEBRATES
MICROORGANISMS
NITROGEN
NONMETALS
NUTRIENTS
NUTRITION
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PARTICLES
PHYTOCHROMES
PIGMENTS
PLANKTON
PORPHYRINS
RENEWABLE ENERGY SOURCES
VERTEBRATES