Bacterial activity in seagrass (Posidonia oceanica) sediments

LÓPEZ, N.I.; DUARTE, C.M.; VALLESPINÓS, F.; ROMERO, J. AND T. ALCOVERRO

JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY

Elsevier Science Publishers, B.V., Amsterdam

Año: 1995 vol. 187 p. 39 - 49

0022-0981

Abstract We examine here the hypothesis that benthic bacterial activity in seagrass [Posidoniu oceanicaexamine here the hypothesis that benthic bacterial activity in seagrass [Posidoniu oceanica (L.) Delile] meadows is dependent on seagrass growth and availability of inorganic nutrients in the sediments. This was achieved by measuring bacterial activity (ammonification rates, and exoproteolytic and exoglucosidase activities) during an annual cycle in five P. oceanica oceanica meadows in the NW Mediterranean. Benthic bacterial activity was high, and tended to increase with in- creasing seagrass production. This trend is likely to involve a direct effect derived from the greater supply of organic carbon in productive meadows, and an indirect effect derived from the fact that productive meadows develop over nutrient-rich sediments and yield nutrient-rich detritus. Phos- phorus availability to bacteria was low, for plant detritus was deficient in phosphorus relative to bacterial requirements, and bacterial activity was reduced after seagrasses depleted inorganic phosphorus from the sediments at the onset of exponential plant growth. These results indicate that, on local and annual time scales, benthic bacterial activity is directly related to seagrass production in the NW Mediterranean, because of enhanced inputs of organic matter by the seagrasses, while on seasonal scales, bacteria and seagrass metabolism are inversely related, apparently because of competition for inorganic nutrients.Delile] meadows is dependent on seagrass growth and availability of inorganic nutrients in the sediments. This was achieved by measuring bacterial activity (ammonification rates, and exoproteolytic and exoglucosidase activities) during an annual cycle in five P. oceanica oceanica meadows in the NW Mediterranean. Benthic bacterial activity was high, and tended to increase with in- creasing seagrass production. This trend is likely to involve a direct effect derived from the greater supply of organic carbon in productive meadows, and an indirect effect derived from the fact that productive meadows develop over nutrient-rich sediments and yield nutrient-rich detritus. Phos- phorus availability to bacteria was low, for plant detritus was deficient in phosphorus relative to bacterial requirements, and bacterial activity was reduced after seagrasses depleted inorganic phosphorus from the sediments at the onset of exponential plant growth. These results indicate that, on local and annual time scales, benthic bacterial activity is directly related to seagrass production in the NW Mediterranean, because of enhanced inputs of organic matter by the seagrasses, while on seasonal scales, bacteria and seagrass metabolism are inversely related, apparently because of competition for inorganic nutrients.P. oceanica oceanica meadows in the NW Mediterranean. Benthic bacterial activity was high, and tended to increase with in- creasing seagrass production. This trend is likely to involve a direct effect derived from the greater supply of organic carbon in productive meadows, and an indirect effect derived from the fact that productive meadows develop over nutrient-rich sediments and yield nutrient-rich detritus. Phos- phorus availability to bacteria was low, for plant detritus was deficient in phosphorus relative to bacterial requirements, and bacterial activity was reduced after seagrasses depleted inorganic phosphorus from the sediments at the onset of exponential plant growth. These results indicate that, on local and annual time scales, benthic bacterial activity is directly related to seagrass production in the NW Mediterranean, because of enhanced inputs of organic matter by the seagrasses, while on seasonal scales, bacteria and seagrass metabolism are inversely related, apparently because of competition for inorganic nutrients.