Naslov
Nutrient limitation of phytoplankton in the Ombla estuary

Autori
Carić, Marina ; Jasprica, Nenad

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Abstract book International interdisciplinary scientific conference Sustainability of the karst environment-dinaric karst and other karst regions / Bonacci O., Župan Ž. - Gospić : Plitvička jezera : Centar za krš i speleologiju, Sarajevo, 2009, 32-32

ISBN
978-953-7333-02-7

Skup
Sustainability of the karst environment-dinaric karst and other karst regions

Mjesto i datum
Plitvice lakes, Croatia, 23.09.2009. - 26.09.2009

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
limitation; nutrient; salinity; estuary; phytoplankton

Sažetak
The spring of the karstic Ombla River is located on the Adriatic coast near Dubrovnik. The spring discharges at sea level, forming the Ombla River, and almost immediately flows into the sea to form a small, 4-km long, highly stratified estuary. The estuary&#8217; s upper reach is about 6 m deep, while the lower reach is up to 25 m deep. The discharge measurements of the Ombla River show that the average outflow equals 26 m3 s-1 (discharge varies between 2.3 and 112 m3 s-1). Samples for the analysis of hydrographic, chemical and biological parameters were collected at three stations (Ombla-1, 6 m deep ; Ombla-2, 15 m ; Ombla-3, 25 m) along the estuary, during 17 cruises from November 1999 to November 2000. In estuaries which are seasonally varying mixtures of fresh and sea water, there is evidence for seasonal and spatial variations in the limiting nutrient. The scope of this paper is to determine which nutrient may be limiting for phytoplankton growth along the longitudinal section of the Ombla estuary, at any salinity. For the Ombla estuary has been used for the first time a method utilizing overlaid graphs for nutrients vs. salinity. Temperatures rose from March to end-May and were more or less constant until September. In October, the water column began to cool, especially in the surface layer. A sharp halocline persisted throught the year and delimited the low salinity surface layer and the saline bottom layer. Salinity in the surface layer oscilated from 9.68 &#8211; 37.54. The salinity in the bottom layer was quasi constant throughout the year, with most values around 38, and range from 33.3 &#8211; 38.88. In total, 40% of samples were with salinity values >38.4. The concentration of all nutrients decreased throughout the estuary for most of the year. Maximal nutrient values, excluding ammonia, were found in the surface layer. The nutrient concentrations in the surface layer oscillated far more than in the bottom layer, especially TIN and SiO4. The Redfield ratio (TIN/ PO4) values were appropriate for phytoplankton growth from April to August, and means were as follows: 27 (Ombla-1), 31 (Ombla-2), 38 (Ombla-3). The Redfield ratio increased throughout the estuary, almost due to decreased PO4 concentrations (<0.01 &#181; M). P is limited nutrient at any salinity along the longitudinal axis of estuary, except by the higher salinities (salinity >38.4 when there is a transition from P to N limitation. The phytoplankton abundances, both NANO and MICRO significantly decreased (P<0.05) along the estuary, as well as throughout the water column. The phytoplankton abundance was greater at lower salinity, and the maximal, MICRO abundance (2.8 x 105 cells L-1) and NANO abundance (1.9 x 106 cells L-1) were found at a salinity of 24.79 and 29.21, respectively. A lower phytoplankton abundances at higher salinities is probably caused by N limitation in this estuary.

Izvorni jezik
Engleski

Znanstvena područja
Geologija, Kemija, Biologija

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