Contribution a la connaissance d'une Poussee extraordinaire d' algues unicellulaires (Adriatique Septentrionale)

The phenomenon known as "sea-water bloom" ("mare sporco", "Meeresbliite") was observed in the northern Adriatic in summer 1983. It appears as a gelatinous, dense mass floating at the sea surface. Samples from Crikvenica (July) and Lopar, Rab Island (August) were analysed. A total of 58 diatoms, of which 32 benthic species, 25 dinoflagellates and 10 coccolithophorids were identified by microscopy. A recently described genus, Spatulodinium Cachon & Cachon, represented by the type species S. pseudonoctiluca (Pouchet) Cachon & Cachon, was also found. With respect to the known ecology of individual algal groups it may be concluded that benthic diatoms had reproduced intensively at the sea bottom a long while before the phenomenon became visible at the sea surface. Reproduction is also the period of the most intensive secretion of mucus. Release of the gelatinous mass from the sea bottom at summer temperatures which are unfavourable for diatoms, is actually the end of the bloom. A gelatinous mass full of gases released by bacterial degradation begins to ascend and on its way towards the sea surface, it embeds plankton organisms. In the final stage torn mucus descends to the bottom where it is gradually completely degraded.peer-reviewe

El rol de los ciliados en la red trófica microbiana de la zona eutrófica de la bahía de Kaštela (Adriático central)

Interactions among phytoplankton, bacterioplankton, heterotrophic nanoflagellates (HNF), ciliated protozoa and copepod nauplii were studied in the eutrophicated part of Kas?tela Bay from May 1998 to November 1999. Special emphasis was placed on relationships between size categories of nonloricate ciliates (NLC) and other microbial food web components. Biomasses of phytoplankton and bacteria were primarily influenced by abiotic parameters. Temperature indirectly controlled variation in HNF biomass through the changes in biomass of bacteria and the smaller phytoplankton fraction. Besides HNF, bacterial biomass was affected by the NLCLas interacciones entre fitoplancton, bacterioplancton, nanoflagelados heterótrofos (HNF), ciliados y nauplios de copepodos fueron estudiadas en una zona eutrófica de la bahía de Kas?tela desde Mayo de 1998 hasta Noviembre de 1999. Se dedicó una atención especial a la relación entre distintas clases de tamaños de ciliados no loricados (NLC) y otros componentes de las redes tróficas microbianas. Las biomasas de fitoplancton y bacterioplancton estaban principalmente influenciadas por parámentros abióticos. La temperatura de forma indirecta controlaba la variación de la biomasa de HNF, a través de cambios en la biomasa bacteriana y de la fracción de menor tamaño de fitoplancton. Aparte de los nanoflagelados heterótrofos, la biomasa bacteriana estaba afectada por los NL

CHANGED PATTERNS OF REMOTELY SENSED CHLOROPHYLL A IN THE ADRIATIC-INFLUENCE OF METEOROLOGICAL CONDITIONS

The patterns of spatial distribution of pigment concentrations in the Adriatic Sea were studied using remotely sensed data from the CZCS (1978-1986), SeaWiFS data from 1997-2000 and 2003, Color POLDER (CNES) data for 1997, and some other data. In the earlier investigations, open waters of the Middle and especially the Southern Adriatic were considered almost oligotrophic regions. Although the pollution-induced changes were reflected from time to time in the whole Adriatic, the southern portion seemed to remain the least productive. Contrary to this, the recent evidence was found for the increased productivity of this southern region in some periods. The patterns of pigment distribution were the result of the meteorological forcing, which influenced oceanographic phenomena like water stratification, upwelling, stronger inflows of Mediterranean water into the Adriatic, etc. The satellite methods allowed frequent measurements of the sea, and the possibility to observe changes at the synoptic scale compared to the ship based cruises whose results might have been considerably influenced by undersamplin

Abundance of mesozooplankton in central Adriatic Sea from 1959 to 1991 at Stoncica Station

The dataset is composed of 50 years of approximately monthly mesozooplankton sampling at station Stončica. The volume of filtered water was estimated assuming 70% efficiency of the Hensen 330 micrometer mesh size net according to Laevastu (1958). Subsamples amounting to 1/20 of the catch were counted for the most representative groups. The whole catch was examined for rare species.The results in the datatables are recalculated to (#/m**3)

Evento de mortalidad en un pequeño lago salido (Lago Rogoznica) causado por inusuales condiciones de holomixia

The study of a small saline eutrophic lake was performed under meromictic and holomictic conditions. The meromictic period was characterised by anoxic conditions in the bottom layer with high sulphide and nutrient concentrations. The depth of the nutricline varied as affected by thermohaline conditions in the water column. In late summer 1997, holomictic conditions replaced ordinary meromitic conditions in the lake. This transformation caused anoxia to spread throughout the water column and mass mortality of almost all the organisms occured. Thereafter, oxic conditions were re-established slowly as the new phytoplankton population developed. As a consequence of the particulate organic matter decay, inorganic N and P concentrations increased and had doubled approximately six weeks after the mass mortality. The revitalisation of the phytoplankton population was initiated immediately after the mass mortality by the development of "microflagellate" species, which were favoured by the high ammonia concentrations. The larger phytoplankton species (diatoms and dinoflagellatae) developed at the expense of smaller ones when nitrate became the dominant nutrient in the water column. A year after the mass mortality the composition of the phytoplankton population was the same as before.Se realizó un estudio de un lago salino eutrófico bajo condiciones de meromixia y holomixia. El período meromíctico se caracteriza por condiciones de anoxia en la capa profunda con elevadas concentraciones de nutrientes y sulfhídrico. La profundidad de la nutriclina variaba en función de las condiciones termohalinas de la columna de agua. Al final del verano de 1997, las condiciones de holomixia reemplazaron las de meromixia del lago. Esta transformación causó anoxia que se extendió por toda la columna de agua, lo que se tradujo en una mortalidad masiva de todos los organismos. Después de este evento las condiciones aeróbicas se restablecieron lentamente mientras la nueva población de fitoplancton se desarrollaba. Como consecuencia de la disminución de la materia orgánica particulada, las concentraciones de N y P inorgánico se incrementaron y aumentaron el doble aproximadamente seis semanas después de la mortalidad masiva. La revitalización de la población de fitoplancton se produjo inmediatamente después de la mortalidad masiva por la aparición de especies de “microflagelados”, que se veían favorecidos por la alta concentración de amonio. Las especies de fitoplancton de mayor tamaño (diatomeas y dinoflagelados) se desarrollaronn a expensas de las más pequeñas cuando el nitrato se convertía en el nutriente dominante en la columna de agua. Un año después de la mortalidad masiva la composición de la población de fitoplancton era la misma que había anteriormente