Primary Productivity, Chemo‐organotrophy, and Nutritional Interactions of Epiphytic Algae and Bacteria on Macrophytes in the Littoral of a Lake

Abstract

Epiphytic algal and bacterial in situ community metabolism and physiological—nutritional relationships of macrophyte—epiphyte systems were investigated in the littoral zone of a small temperate lake from April 1968 through May 1969. Annual primary productivity, chemo—organotrophy of dissolved organic compounds, and field and laboratory studies of macrophyte—epiphyte interactions were monitored by carbon—14 techniques. Productivity measurements of epiphytic algae on artificial substrates colonized in emergent (Scirpus acutus Muhl.) and submergent (Najas flexilis L. and Chara spp.) macrophytic vegetation sites were compared over an annual period with pigment (corrected chlorophyll a and total plant carotenoids) estimates of biomass. Changes in biomass are not proportional to changes in photosynthetic activity, except during periods of intense productivity. The mean daily productivity of epiphytic algae was higher per unit macrophyte surface area of emergent plants (336 mg C m—2 day—1) than on submerged plants (258 mg C m—2 day—1). Mean daily productivity per unit area of the littoral zone, for all of the macrophytic surface area colonized, was 195 and 1,807 mg C m—2 day—1 in the Scirpus and Najas—Chara dominated sites, respectively. The total annual production by algal epiphytes in the Scirpus and Najas—Chara dominated sites was 2.86 and 35.00 g C m—2 of lake surface year—1, respectively. Estimates of annual net production of macrophytes and epipelic algae, derived from studies undertaken during the same time period as reported in this study, indicate that epiphytic algae were responsible for 31.3% of the total littoral production. The epiphytic algae were responsible for 21.4% of the total annual production for the whole lake when the production of the pelagial phytoplankton was added to that of the littoral communities. In comparison to the pelagial phytoplankton alone, the algal epiphytes fixed an amount of carbon equivalent to 75% of the phytoplankton production over the annual period. These results indicate that algal epiphytes on submerged macrophytes may be one of the dominant primary producers in shallow—water ecosystems and may be comparable to the phytoplankton. Deposition of 14C—monocarbonates during in situ productivity measurements represented 38.5—71.7% of the total intracellular fixed carbon. Acidification of 14C—productivity samples by rinsing with dilute hydrochloric acid (0.001 N) removed 24% of previously incorporated carbon and is not recommended as a routine procedure. Physiological interactions in macrophyte—epiphyte systems were investigated by bioassay procedure. Inorganic iron added at less than 10 mg liter —1, and at 100 mg liter—1 in combination with organic compounds of chelatory or complexing ability, stimulated photosynthesis of epiphytic algae. Bioassay experiments in which vitamins, trace metals, and inorganic phosphorus were added to algal photosynthesis. Chlorophyll a, corrected for pheopigment degradation products, and total plant carotenoid levels are among the highest standing cr...

Primary production of algae growing on natural and artificial aquatic plants: A study of interactions between epiphytes and their substrate1

“…The lower alkaline phosphatase activity of the epiphytes growing on natural plants suggests that these algae were less P-limited than those growing on plastic plants and obtained P from the living macrophyte. Such transfer has been noted a few times (Allen 1971;McRoy and Goering 1974;IIarlin 1973u) and was recently quantified in our laboratory by Carignan (unpubl. data) who found that about 5% of epiphytic P was derived from the macrophytes.…”

“…A form of symbiosis has been suggested (Wetzel 1975) wherein epiphytes benefit from the organic compounds and nutrients excreted by the plant (Allen 1971;Harlin 1973u;.McRoy and Goering 1974), which, in return, is protected against grazers by the epiphytes (Hutchinson 1975). Alternatively, a competitive relationship has been proposed, in which the macrophytes inhibit epiphyte growth through the release of antibiotics, competition for nutrients, or both (Fitzgerald 1969), while the epiphytes may reduce macrophyte photosynthesis by shading (SanclJensen 1977).…”

Limnology of Lake Rerewhakaaitu

“…In the main lake the shallowness of the water column allows frequent mixing and promotes exchanges between the open water and the sediments. The extensive littoral zone may also play an important role as macrophytes and their associated epiphytes may release large amounts of organic and inorganic compounds which can be utilised by planktonic bacteria and algae (Allen 1971, Wetzel 1975. The crater has a small littoral zone and the shape of its steep-sided basin is probably more important in influencing its limnology.…”

The Biomass and Physiological Responses of Vallisneria natans (Lour.) Hara to Epiphytic Algae and Different Nitrate-N Concentrations in the Water Column

“…However, Wetzel [50] and Allen [51] suggested that host plants could exert considerable influence on periphyton. Under stress conditions, secondary metabolites largely accumulated in V. natans and were released from the surface of leaves, which promoted the growth of attached epiphytic algae and affected its community composition [52,53].…”