A Comparative Study of the Primary Production of Higher Aquatic Plants, Periphyton, and Phytoplankton in a Large, Shallow Lake

Abstract

A Comparative Study of the Primary Productivity of Higher Aquatic Plants, Periphyton, and Phytoplankton in a Large, Shallow Lake C o n t e n t s I n t r o d u c t i o nI n present day limnological and oceanographic studies on primary productivity emphasis is largely on the photosynthetic bacteria and phytoplankton. The contribution of the littoral zone to the total energy fixation of a body of water is commonly assumed to be insignificant. I n marine areas and moderate to large, deep lakes such an assumption is generally valid. It can be erroneous to neglect the sessile littoral producers, however, in.rivers, marshes, ponds, and large, shallow lakes.The importance of the littoral and benthic regions of fresh waters to higher trophic levels is often underestimated. These shallow areas are commonly a source of initial individuals of lentic plankton populations. This habitat provides environmental conditions requisite for numerous organisms, including a vast assemblage of nektonic forms. Perhaps the greatest significance of the littoral zone, however, lies in its contribution to primary productivity for utilization by other trophiclevelsin this portion of the ecosystem. The present studies were designed to elucidate the relative significance of primary productivity of macrophytes and benthic algae to total photosynthetic carbon fixation in a shallow lake. A technique of assaying the growth rate of macrophytes was developed employing carbon-14 as a tracer. Priortoinsitu 1 Intcrnationale Revue 2 ROBERT G. WETZEL application, this method was compared in laboratory cultures to those techniques commonly in use.Modern aquatic synecological concepts have evolved rather slowly from a conflicting and argumentative development of theories and definitions. Fresh waters offer a distinct advantage in the integration of community interrelationships, in that they provide a relatively simplified ecosystem when considered as an individual unit. External factors influencing the relationships are minimized, even though very complex. Perhaps the first consideration of a lake as a n entity per se was the concept of a lake as a microcosm ('FORBES 1887).Early community studies considered the organisms within their environment only from a static species-distributional aspect. Evidence soon accumulated that a more realistic view resulted from investigation of the distribution of species communities from a changing or dynamic viewpoint (i. e. successional, cf. LINDEMAN 1942). Recognition that both the plant and animal constituents of the community are deeply and specifically interrelated, although often indirectly, resulted in several excellent studies of food chain concepts. Aquatic examples include an abbreviated monocyclic freshwater food web of SHELFORD (1913), food cycle interrelationships by NAUMANN (1925) and THIENEMANN (1926), and bicyclic circulation by PERFILIEV (1929) and MACFADYEN (1948).Abolition of the artificial separation of the living community from the environment was initiated among others by THIENEMANN (1918) and deve...

The relative contribution of aquatic macrophytes and their epiphytes to the production of macrophyte beds1

“…The "'CO, evolved was collected in Oxifluor-CO, (NEN) and counted in a scintillation counter (Beckman). Both membrane filters and dried plants were fumed in HCl for 10 min to eliminate Ca1"C03 precipitated during the incubation by macrophyte photosynthetic activity (Wetzel 1965). Membrane filters, which were rolltinely counted with a gasflow colmter (Nuclear-Chicago), were oc- Primary production rates were c&ulated following the methods of Vollenweider (1975).…”

“…Some investigators have been interested only in the macrophytes and have therefore attempted to remove the epiphytes (Wetzel 1964;Adams et al 1974); others were interested only in the epiphytes and therefore measured their production after removal from the macrophytes (Hickman 1971;Kowalczewski 1975) or by growing them on artificial substrates (Allen 1971). These differences in techniques make results difficult to compare and obscure any synergistic effects due to competition (Fitzgerald 1969), shading (Sand-Jensen 1977), or the exchange of nutrients (1McRoy and Goering 1974).…”

Respiration Corrections for Bacterial Uptake of Dissolved Organic Compounds in Natural Waters1

“…The absorbing paper was then wet-oxidized in a Van Slykc apparatus and the gas passed into an ion chamber for counting (Wetzel 1964).…”

“…Since such large changes of V and T were introduced, the respiration corrcction is certainly necessary if true uptake values arc to bc obtained, Having established the importance of thcso corrections, we then tested the efficiency of the evolution, absorption, and counting of the 14C02. The gas phase counting system (Wetzel 1964) was calibrated by adding standard Naz*4C0,7 solution, acidifying, and passing the evolved gas into the counting chambers. Some of the same solution was also added to the closed system and the *"CO2 absorbed by the phenethylaminc-moistened paper.…”

Controls of Benthic Nitrogen Fixation and Primary Production from Nutrient Enrichment of Oligotrophic, Arctic Lakes

“…In oligotrophic lakes, benthic production can dominate whole-lake production (Wetzel 1964;Ramlal and others 1994;Vadeboncoeur and others 2003;Ask and others 2009) and fuel whole-lake food webs (Sierszen and others 2003;Vander Zanden and others 2006;Hampton and others 2011). Although oligotrophic lakes can exhibit a high buffering capacity to added nutrients as oxic bottom-waters sequester phosphorus in the formation of iron-P oxides (Wetzel 2001;O'Brien and others 2005), the dynamics that affect benthic processes during the early stages of eutrophication can be subtle and evident even before water-column changes are documented (Rosenberger and others 2008).…”