Effects of submersed macrophytes on ecosystem processes

Bacteria and algae are the numerically dominant organisms in the plankton of lakes and the ocean and their metabolism largely controls pelagic energy flow and nutrient cycling. The purpose of this review is to examine the means by which algae and heterotrophic bacteria interact in planktonic systems. In terrestrial systems, bacterial-plant interactions have been well studied in the rhizosphere, the zone in the soil where microorganisms are influenced by plant roots (108). The concept of the "phycosphere" was introduced as a pelagic analogy to the rhizosphere (7). The phycosphere would be the zone surrounding an algal cell within which microorganisms are influenced by algal products. In considering bacterial-algal interactions, then, we should ask ourselves whether a phycosphere exists. I cite specific evidence from the literature for various types of interactions. In doing this I rely heavily on laboratory studies because relatively little field oriented work is available. I include neither the photosynthetic bacteria (e.g. Chlorobiaceae, Rhodospirillaceae) nor the large macroalgae (seaweeds) in this review. The cyanobacteria have both algal and bacterial characteristics, being prokaryotes and capable of oxygenic photosynthesis. As planktonic, aerobic photo-autotrophs the cyanobacteria clearly belong with the phytoplankton in terms of this review.

Interactions between bacteria and algae in aquatic ecosystems

A mechanism to account for macrophyte decline in progressively eutrophicated freshwaters

Diatom extracellular polymeric substances: function, fine structure, chemistry, and physiology

Publisher Summary This chapter discusses the factors controlling the zonation of freshwater plants The groups of plants classified as macrophytes that comprise aquatic vegetation are presented along with their overall depth distribution Specific examples of the zonation of vegetation in a range of lakes, to emphasize the distinction between environmental factors varying solely in the vertical plane and those that have both vertical and horizontal components are presented in the chapter This distinction underlies the causal analysis of zonation The chapter describes vertical sequences of growth form or individual dominants in relation to gradients in water table The aquatic vegetation ranges along this gradient from woodland to submerged plant communities The chapter discusses the habitat variables, vertical zonation, vertical and horizontal components of zonation, sediments and plant responses, plant adaptations, photomorphogenetic responses underwater, growth forms, plant strategies and interspecific competition, competition with microalgae, and the control of macrophyte zonation by substrate or by light

zonation of plants in freshwater lakes

The littoral regions of most aquatic ecosystems represent some of the most productive communities of the world (Wetzel 1964) and, as such, warrant intensive investigation. Lake Wingra (Madison, Wisconsin, U.S.A.) contains an extensive littoral zone. Lake Wingra was selected as an intensive study site within the Eastern Deciduous Forest Biome, US-IBP, and is the focus of an interdisciplinary ecosystems analysis study involving more than twenty-two subprojects. The lake is approximately 139-6 ha, with a littoral zone encompassing 31% (43 ha) of the total area. The lake is highly alkaline (80-200 mg CaCO3 equivalent per litre), with high (7-10-3) pH values prevailing within the littoral during midsummer. Most of the phosphorus enters the lake via a storm sewer system from an urban watershed, and dissolved phosphorus concentrations in the littoral range from 5 to 33 jug 1-1 during summer (Kluesener 1972). Phytoplankton production in the pelagial is very high with the annual mean rate of carbon fixation near 2 g C m-2 day (Koonce 1972). The littoral of Lake Wingra is dominated by the submergent macrophyte Myriophyllum spicatum L. (Eurasian water milfoil). The macrophyte vegetation of the lake affords an extensive substratum for colonization by periphytic epiphyton. Apparent net primary production of the community is high and, in addition, a considerable level of extracellular secretion ('excretion') of photosynthate occurs. This excretant, generally about 5% of total net photosynthesis of macrophytes in Lake Wingra, is available for channelling through other trophic levels within the ecosystem. Another important aspect of the macrophyte component of the littoral of Lake Wingra is the dense structure which the macrophytes provide as a habitat for bluegill sunfish (Lepomis macrochiris Raf.). The habitat has the appearance of a dense forest and may serve as a factor in the high numbers and small individual size of fish in the bluegill population of the lake. The macrophytes contribute considerably to the annual detritus pool. Since submergent macrophytes remove nutrients from both the water and sediments (Bristow & Whitcombe 1971), the plants are expected to have a significant role in the nitrogen and phosphorus cycling in the lake.

Seasonal Production of the Myriophyllum Component of the Littoral of Lake Wingra, Wisconsin

This investigation was conducted to characterize the algal inhibitory material originally isolated by Proctor (1957b) from Chlamydomonas. Analysis of purified extracts demonstrated that the inhibitor was a mixture of fatty acids. The identity and relative percentages of most of the components of the mixture were determined by GLC analysis. There is evidence that unsaturated fatty acids were responsible for the majority of the toxicity.

A chemical characterization of an algal inhibitor obtained from chlamydomonas

Interactions between a naturally-collected algal species and strains of bacteria with which it was closely associated were examined under controlled conditions. Three strains of bacteria, Pseudomonas, Xanthomonas and Flavobacterium, were isolated from Oscillatoria. These bacteria were grown in combination with axenic cultures of the Oscillatoria culture as well as with several additional algal species. Oscillatoria growth was stimulated by all of the bacteria, but other algal species varied in their response. Some were stimulated, but others were inhibited or unaffected by exposure to the bacterial strains. There were also observations indicating that some algae may be able to develop resistance to antagonistic bacteria. These data suggest that succession and dominance of individual algal species may be influenced by interactions with bacteria.

Observations on interactions between naturally-collected bacteria and several species of algae

Photosynthetic rates and productivity of Myriophyllum spicatum L. were examined in the littoral by incubating shoot sections at three rooting depths using a 14C technique. At a rooting depth of 240 cm, the interrelation of biomass and photosynthetic rates resulted in the production of 56% of the total photosynthetic productivity within 100 cm of the water surface in May. In August, 57% of the total productivity occurred within only 20 cm of the surface. Variations in the depth distribution of biomass, due to differing growth and sloughing patterns, resulted in different depth relations of photosynthesis at the other rooting depths. Light extinction and light adaptation of photosynthetic tissues were other factors determining the depth relations of photosynthesis.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1974.19.3.0377

Michael D. McCracken

Papers

Seasonal Production of the Myriophyllum Component of the Littoral of Lake Wingra, Wisconsin

A chemical characterization of an algal inhibitor obtained from chlamydomonas

Observations on interactions between naturally-collected bacteria and several species of algae

Depth distribution of photosynthetic activity in a Myriophyllum, spicatum community in Lake Wingra1

Productivity of Oedogonium in Lake Wingra, Wisconsin