GERBAM — Deuxième Colloque International de Bactériologie marine — CNRS, Brest, 1-5 octobre 1984
IFREMER, Actes de Colloques, 3, 1986, pp. 129-136
14
BIOMASS DISTRIBUTION AND PHYSIOLOGICAL CAPABILITIES OF BACTERIA IN THE WATER COLUMN ABOVE A SEAGRASS SYSTEM
B. VELIMIROV*, G. HERNDL* et G. KAVKA**
* Zool. Institut, Abt. Meeresbiologie, Univ. WIEN (AUSTRIA)
** Bundesanstalt fur Wassergüte, WIEN (AUSTRIA)
ABSTRACT - The distribution pattern of bacteria in the water column above and within a Posidonia uceanica
bed near Ischia (off the Gulf of Naples) was investigated and correlated with DOC and POM data for autumn
and winter. Data from samples of 5 stations along a transect from shallow to deep showed rather low bacterial
densities ( 10
4 . ml' 1 ) for both seasons. The number of attached bacteria was higher in late winter as compared to
autumn when the leaves are shed from the stands. Except for occasional peaks DOC ranged between 1.5 and
4.5 mg C/1 while POM concentrations ranged from 4 to 14 mg AFDW.1-1. Hydrolytic capabilities of isolated
bacterial colonies showed that more carbohydrate substrates could be fermented in winter as compared to
autumn. This is correlated with an input of POM into the system due to the leaf fall of the seagrass which takes
place in late autumn. The problem of structural carbohydrate breakdown is discussed.
Key words: seagrass bed, DOC, POM, fermentation, cellobiose.
RÉSUMÉ - La distribution des bactéries dans l’eau sus-jacente et dans un herbier de Posidonia oceanica a été
étudiée à Ischia (au large du Golfe de Naples) et reliée aux concentrations de COD et MOP en automne et en
hiver Les données de 5 stations le long d’un transect montrent que la densité bactérienne est faible (x 104) pour
les deux saisons et que le nombre de bactéries fixées est plus élevé en hiver qu’en automne. La concentration en
COD varie entre l,4 et 4,5 mgC/1 et celle en MOPentre4et 14 mg de matière organique l -1. Les caractéristiques
hydrolytiques des souches purifiées indiquent qu’un plus grand nombre de substrats carbohydratés peuvent être
fermentés en hiver. Cette caractéristique peut être reliée avec la chute des feuilles de l’herbier en automne, qui
représente une augmentation importante de matière organique dans l’écosystème. Le problème de la dégradation des carbohydrates de structure est discuté.
Mots clés : herbier, COD, MOP, fermentation, cellobiose
INTRODUCTION
Most of the work on the ecology of mediterranean seagrass beds has concentrated on
growth and production (Bay, 1978; Ott, 1980), the related daily and seasonal variations in
carbohydrate and amino acid concentrations (Velimirov and Pirc, 1983, Pire, 1984), or
consumer interactions (Ott and Maurer, 1977; Traer, 1980; Velimirov, 1983). The importance of microorganisms as decomposers of macrophyte material or as a potential food
source for filter and deposit feeders has been rather neglected. Although information on
the role of bacteria on Posidonia derived macrophyte debris and on metabolically active
Posidonia leaves is now available (Velimirov et al., 1981; Novak, 1984), data on the
distribution and abundance of bacteria within and above seagrass beds are still lacking.
The growth cycle of Posidonia oceanica is marked by the leaf fall of the seagrass in late
autumn (October, November). This brings about a release of particulate organic matter
129
IFREMER, Actes de Colloques, 3, 1986, pp. 129-136
14
BIOMASS DISTRIBUTION AND PHYSIOLOGICAL CAPABILITIES OF BACTERIA IN THE WATER COLUMN ABOVE A SEAGRASS SYSTEM
B. VELIMIROV*, G. HERNDL* et G. KAVKA**
* Zool. Institut, Abt. Meeresbiologie, Univ. WIEN (AUSTRIA)
** Bundesanstalt fur Wassergüte, WIEN (AUSTRIA)
ABSTRACT - The distribution pattern of bacteria in the water column above and within a Posidonia uceanica
bed near Ischia (off the Gulf of Naples) was investigated and correlated with DOC and POM data for autumn
and winter. Data from samples of 5 stations along a transect from shallow to deep showed rather low bacterial
densities ( 10
4 . ml' 1 ) for both seasons. The number of attached bacteria was higher in late winter as compared to
autumn when the leaves are shed from the stands. Except for occasional peaks DOC ranged between 1.5 and
4.5 mg C/1 while POM concentrations ranged from 4 to 14 mg AFDW.1-1. Hydrolytic capabilities of isolated
bacterial colonies showed that more carbohydrate substrates could be fermented in winter as compared to
autumn. This is correlated with an input of POM into the system due to the leaf fall of the seagrass which takes
place in late autumn. The problem of structural carbohydrate breakdown is discussed.
Key words: seagrass bed, DOC, POM, fermentation, cellobiose.
RÉSUMÉ - La distribution des bactéries dans l’eau sus-jacente et dans un herbier de Posidonia oceanica a été
étudiée à Ischia (au large du Golfe de Naples) et reliée aux concentrations de COD et MOP en automne et en
hiver Les données de 5 stations le long d’un transect montrent que la densité bactérienne est faible (x 104) pour
les deux saisons et que le nombre de bactéries fixées est plus élevé en hiver qu’en automne. La concentration en
COD varie entre l,4 et 4,5 mgC/1 et celle en MOPentre4et 14 mg de matière organique l -1. Les caractéristiques
hydrolytiques des souches purifiées indiquent qu’un plus grand nombre de substrats carbohydratés peuvent être
fermentés en hiver. Cette caractéristique peut être reliée avec la chute des feuilles de l’herbier en automne, qui
représente une augmentation importante de matière organique dans l’écosystème. Le problème de la dégradation des carbohydrates de structure est discuté.
Mots clés : herbier, COD, MOP, fermentation, cellobiose
INTRODUCTION
Most of the work on the ecology of mediterranean seagrass beds has concentrated on
growth and production (Bay, 1978; Ott, 1980), the related daily and seasonal variations in
carbohydrate and amino acid concentrations (Velimirov and Pirc, 1983, Pire, 1984), or
consumer interactions (Ott and Maurer, 1977; Traer, 1980; Velimirov, 1983). The importance of microorganisms as decomposers of macrophyte material or as a potential food
source for filter and deposit feeders has been rather neglected. Although information on
the role of bacteria on Posidonia derived macrophyte debris and on metabolically active
Posidonia leaves is now available (Velimirov et al., 1981; Novak, 1984), data on the
distribution and abundance of bacteria within and above seagrass beds are still lacking.
The growth cycle of Posidonia oceanica is marked by the leaf fall of the seagrass in late
autumn (October, November). This brings about a release of particulate organic matter
129