Abstract
Microalgal biofilms are sensitive to environmental conditions. Impacts of contaminants on assemblages of marine biofilm are often investigated in laboratories or in mesocosms. Such experiments are rarely representative of the effects of contaminants on biofilms under natural conditions. Studies in field situations, with enough power to detect impacts, are necessary to develop a better understanding of the effects of contaminants on ecological processes. Metals are a common contaminant of marine systems and can cause disturbances to assemblages. Using a new technique to experimentally deliver contaminants to microalgal assemblages, hypotheses were tested regarding the effects of zinc on microalgal biofilms growing on settlement panels in subtidal and intertidal habitats. PAM fluorometry was used to assess the amount and physiological state of biofilms on panels. Control panels deployed for 1 month in each habitat had significantly greater amounts of biofilm than those exposed to zinc. After deployment for 3 months, the results varied with location. The observed effects on the biofilm did not, however, cause significant changes in the macro-invertebrate assemblages that developed on the panels.
Highlights
Bacteria and micro-algae are among the first organisms to colonize hard surfaces submersed in the sea, forming a film, hereafter referred as microbial films or biofilm
On panels deployed in the subtidal habitat, there were no significant differences in the Yield between treatments
The yield of marine phytoplankton has been shown to decrease significantly when micro-algae are exposed to metal solutions of zinc, copper and cadmium (Miao et al 2005)
Summary
Bacteria and micro-algae are among the first organisms to colonize hard surfaces submersed in the sea, forming a film, hereafter referred as microbial films or biofilm. Especially bacteria, are sensitive to changes in environmental conditions. The physiology and composition of a biofilm can reflect the local environmental conditions for a given substratum (Wieczorek et al 1996 and references therein). Herbicides and metals, for example, have long-term effects on chlorophyll-a in biofilms, because the latter tend to react to toxicants by changing their composition, usually favouring more tolerant taxa (Sabater et al 2007). Biofilms have been suggested to contribute to the cycling of metals, such as zinc, in aquatic systems Little is known , about the effects of contaminants on biofilms, but it is believed that lethal or chronic effects of contaminants throughout a trophic web depend on the specific effects of such contaminants on the biofilms in addition to the characteristics of the biofilms themselves (Sabater et al 2007)
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