Free and Particle‐associated Extracellular Enzyme Activity and Bacterial Production in the Lower Elbe Estuary, Germany

Abstract

A high abundance of particles and aggregates is a characteristic of estuaries and may represent important loci of increased bioproductivity and microbial activity. From a survey performed in the Elbe estuary, particle concentration (using a particle counter), bacterial biomass and abundance (AODC method), bacterial production rates ([3H] thymidine method) and the microbial extracellular enzyme activity of 11 enzymes (MUF and MCA method) were determined with particular respect to their relationship to particles and aggregates (sizefractionated). Although higher particle abundance was found compared to other sections of the river Elbe, neither relative nor absolute bacterial activity associated with particles and aggregates was enhanced. The activity of free dissolved microbial enzymes was found to dominate the breakdown of organic material. The productivity of free dispersed bacteria ≥0.2…<2 μm (2…69%) and bacteria attached to small particles ≥2…<10 μm (27…93%) considerably surpassed that of bacteria associated with particles >10 μm (0…40%). This indicates that the larger particles and aggregates do not always contribute substantially to the overall microbial activity in rivers and estuaries.

Cell-free extracellular enzymatic activity is linked to seasonal temperature changes: a case study in the Baltic Sea

“…LAPase was the EEA with the lowest seasonal amplitude variability in the proportion of dissolved EEA, whereas BGase showed the largest seasonal variability. These values are within the same ranges reported in the surface coastal North Sea waters (Someville and Billen, 1983), Tokyo Bay (Hashimoto et al, 1985), Mediterranean Sea (Karner and Rassoulzadegan, 1995), Elbe estuary (Karrasch et al, 2003), Gulf of Mexico (Ziervogel and Arnosti, 2008;Ziervogel et al, 2010), North Pacific Subtropical Gyre (Duhamel et al, 2010), and the epipelagic to bathypelagic waters of the Atlantic (Baltar et al, 2010(Baltar et al, , 2013.…”

Ecomicrobiology and microbial assimilative capacity of the oligotrophic Andean Lake Laja, Chile

“…The extracellular enzyme activity constitutes the fi rst step of the microbiological self-purification process (Karrasch 2003a(Karrasch , 2003b and concurrently the rate-limiting step in the microbial utilisation of dissolved and particulate matter in aquatic environments (cf. Chróst 1991 and cited references).…”

“…The proportion of extracellular enzyme activities associated to cells and particles (ectoenzymes) versus dissolved free external enzymes represents an important ecological ratio (Karrasch et al 2003a, 2003b, Karrasch 2005. A more particle-related degradation of organic material is subjected to a higher sedimentation probability, resulting in an export (sedimentation) of organic matter and of selfpurifi cation capacities, while dissolved external enzymes remain more or less unaffected by the hydrographical situation (Karrasch et al 2003b, Karrasch 2005.…”

“…The role of bacteria in aquatic ecosystems is in the fi rst place, defi ned by their enzymatic capacities which represent the first step of organic matter degradation (Overbek 1991, Romaní & Sabater 1999, Karrasch 2003a. Extracellular enzyme activities are essential for the regeneration of nutrients and the breakdown of polymer particulate and dissolved organic compounds (Hoppe 1983, Chróst 1991, Karrasch et al 2003b.…”

“…Extracellular enzyme activities are essential for the regeneration of nutrients and the breakdown of polymer particulate and dissolved organic compounds (Hoppe 1983, Chróst 1991, Karrasch et al 2003b. These processes are a rate-limiting step for both the growth of the bacteria and for the microbial breakdown of particulate and dissolved organic material in aquatic systems (Chróst 1991, Karrasch et al 2003a, 2003b.…”