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PHYCOLOGICAL SOCIETY OF AMERICA

Ecology

Distribution    Biotic Interactions    Nutrients    Bioindicators    

Bioindicators

Because many Ulva species thrive in high nutrient conditions, their abundance in an area may indicate eutrophication.   In addition, there is a close correlation between the concentration of seawater inorganic nitrogen and phosphate and tissue nitrogen and phosphorous, respectively.  (U. lactuca and U. expansa are particularly good bioindicators of eutrophication.)  This close correlation between seawater concenctrations and tissue concentrations in Ulva implies that the relative amounts of tissue nutrients reflect the degree of eutrophication in the water where the algae grew.   Even better than simply testing the water itself, the advantage of using Ulva as a bioindicator is that the levels of nutrients in the tissues result from long-term integration and accumulation from the surrounding water.  A sample of water would only show the relative concentrations for the particular time the sample was taken. Their cosmopolitan distribution, simple morphology and ease of growth assessment, along with a graded tolerance and response to stress induced by pollutants all make Ulva good bioindicators.  

Ulva are often able to thrive in polluted environments

Ulva species can be used as bioindicators of metal contamination as well.  U. lactuca, for example, is a good indicator of  Mn, Fe, Cu, Zn and Pb contaminations.  The locations of high levels of metal contamination, for example in urban sites, can be reliably identified using U. lactuca.  Metals can harm many forms of marine life, including algae.  Metals may inhibit reproduction of Ulva by interfering with the ability of male and female gametes to find one another via phermones.  Cadmium has been found to reduce growth uptake by about half in U. lactuca by inducing loss of pigments and thus decreasing the rate of photosynthesis.  

Ulva can also be used as indicators in areas that have been exposed to large concentrations of crude oil. The oil hurts algae by inhibiting DNA and RNA activities.  It can cause damage simply by coating them or by disrupting cell metabolism and inhibiting photosynthesis through algal uptake of hydrocarbons. Ulva can be good algae to study in such cases due to their simple morphology, ease of growth assessment and graded tolerance and response to stress induced by pollutants, as I mentioned earlier.

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