Microbiological studies along a gradient of eutrophication in a shallow coastal inlet in the southern Baltic Sea (Nordrügensche Bodden)

Abstract

bleasurements of microblal biomass and actlvity were carried out at 6 representative locatlons along a gradient of eutrophlcatlon In the Nordrugensche Bodden (southern Baltic Sea Germany) h4easurements in the water column revealed that turbid~ty, seston content and concentratlons of chlorophyll a and inorganic nutnents (ammonla nitnte, nitrate phosphate) increased from the outer to the inner parts of the Bodden whereas salin~ty decreased Investigations of sedlments conf~rmed this gradlent of eutrophlcatlon Whereas in the outer parts of the Bodden sandy sediments prevailed sandy mud and muddy s e d ~m e n t s dominated towards the inner parts Generally, organic carbon and nltrogen, concentratlons of chlorophyll a and phospholip~ds (indicator of microbial biomass) oxygen consumption and hydrolytlc enzyme actlv~tles Increased wlth Increasing level of eutrophlcatlon At the relatively unpolluted locatlon in the outer parts of the Bodden proteolytic enzymes dominated at the sedlment surface In subsurface horlzons carbohydrate-decomposing enzymes galned more importance At the heavily polluted locatlons In the inner parts of the Bodden proteolytlc enzymes were even more Important Wlth increasing sediment depth enzyme actlvlties were greatly reduced h o w ever, and shlfts In the spectrum of hydrolytlc enzymes were less pronounced Among the blologlcal and chemlcal parameters, charactenstlc patterns of lnterrelatlonships became obvious whlch led to the conclus~on that microblal blomass and enzyme actlvlties in sediments of the outer and central parts of the Bodden are limited by organlc carbon The organic-nch sediments of the lnner parts of the Bodden however did not support furthe] increases In microbial biomass and decompos~tlon act~vltles Enzyme actlvltles are discussed In relatlon to the composition and degradablhty of substrates The enzymatic decomposltlon potential was measured by means of fluorogenlc model substrates Methodological investigations showed that the methylumbelllferyl substrates used reacted specifically enough to ]ustlfy the11 use In ecological studies Sedlments can be stored refngerated for over 2 mo without changes in the spectrum of hydrolytic enzymes KEY WORDS-Nordrugensche Bodden (Southern Baltic Sea) .