Aquatic ecosystems, cyanobacteria

In recent years, the unicellular nature of planktonic algae has been exploited for the construction of whole-cell based biosensors capable of real-time response on critical change of the aquatic ecosystems caused by pollutant emissions. Most of the proposed devices are based on the electrochemical detection of the inhibiting effect on the photosynthetic activity of algae and cyanobacteria exerted by some toxicants. 

Saxitoxin is the only cyanobacterial toxin that is included in Schedule 1 of the Chemical Weapons Convention. However, other cyanotoxins would in fact be easier to obtain, due to the fact that they are produced by a wider range of species, and occur in many aquatic ecosystems. For this reason, in this chapter we will consider all the hep-atoxins and neurotoxins synthesized by cyanobacteria. 

Eutrophication of coastal areas results in an increase of phytoplankton aquatic ecosystems and the potential of rapidly increased emissions of isoprene and monoterpenes from the algae and cyanobacteria in the bloom. Eutrophication, therefore, could be a result of higher density and biomass of phytoplankton per area unit, but unfortunately studies of terpenoid productiOTi of single species under the excess nutrients have not been performed. 

Lakes, rivers, swamps, and marshes - common in temperate areas - contribute little to the diversity of natural products. Abundant dull-green grass and dull-colored fish and moUusks characterize lakes and rivers, in contrasts with the vivid colors of tropical fish and seaweeds. Haplosclerid sponges are occasionally abundant in freshwater, but their secondary metabolism is limited to demospongic acids (Dembisky 1994), in contrast with the variety of metabolites from marine sponges in the same order. Where not for cyanobacteria (which are as rich of unusual metabolites as the marine strains), tropical amphibians, and aquatic fimgi, freshwater ecosystems would have passed unnoticed in this book. 

Mulholland, M. R., Glibert, P. M., Berg, G. M., Van Heuiielem, L., Pantoja, S., and Lee, C. (1998). Extracellular amino acid oxidation by phytoplankton and cyanobacteria A cross-ecosystem comparison. Aquat. Microb. Ecol. 15, 141-152. 

Freshwater phytoplankton blooms commonly occur in reservoirs, lakes, canals, and ponds under eutrophic and other physicochemical conditions that are favorable for bloom formation. Among the different types of phytoplankton blooms that can occur in freshwater ecosystems, cyanobacterial (blue-green algal) blooms are usually the most undesirable for the following reasons 1) certain species of cyanobacteria can produce toxins that kill aquatic and terrestrial animal life 2) some species of cyanobacteria produce off-flavor compounds that can impart an undesirable taste to cultured fish 3) cyanobacteria are a poor base for... 

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