Particulate phosphorus in water column of the middle Adriatic sea

Partikularni fosfor (PP) istraživan je u vodenom stupcu srednjeg Jadrana na 34 postaje, od toga na 7 postaja u priobalju i 4 postaje u otvorenom moru (vertikalna raspodjela), na 4 postaje na uzgajalištima školjkaša i riba (vertikalna raspodjela) i na 19 postaja u estuarijima Krke, Cetine i Jadra (površinski sloj). U svim uzorcima morske vode određene su i koncentracije otopljenog anorganskog (DIP) i ukupnog fosfora (TP). Na postajama priobalja i otvorenog mora mjereni su hidrografski parametri, koncentracije hranjivih soli dušika i silicija i koncentracije klorofila a. U uzorcima morske vode iz područja srednjeg Jadrana provedena su dva laboratorijska eksperimenta u kojima su koncentracije partikularnog i ukupnog fosfora mjerene tijekom razdoblja od 9 dana. Koncentracije PP-a u području priobalja i otvorenog mora srednjeg Jadrana bile su u rasponu od 0,007 μmol dm-3 (otvoreno more blizu otoka Palagruže) do 0,589 μmol dm-3 (Šibenski zaljev). U priobalnom području više koncentracije PP-a zabilježene su u površinskom sloju tijekom proljeća, jeseni i zime, a tijekom ljeta u pridnenom sloju. U području otvorenog mora koncentracije PP-a bile su prostorno i vremenski ujednačene. Koncentracije PP-a u području priobalja bile su više od koncentracija otopljenog anorganskog fosfora, a u području otvorenog mora niže. Statističkom analizom rezultata sezonskih istraživanja hranjivih soli, temperature, saliniteta i koncentracija klorofila a određene su značajne pozitivne korelacije PP-a s klorofilom a te hranjivim solima dušika i silicija i negativna korelacija sa salinitetom. Na uzgajalištima školjkaša najniže koncentracije PP-a izmjerene su na dubini pergolara. U području uzgajališta riba najviše koncentracije PP-a zabilježene su u sloju vodenog stupca gdje se ribe uzgajaju. Koncentracije PP-a u površinskom sloju duž estuarija rijeka Krke, Cetina i Jadra upućuju na nekonzervativno ponašanje PP-a u odnosu na salinitet. U Cetini i Jadru zabilježeno je pozitivno odstupanje od teoretske raspodjele PP-a duž čitavog estuarija, dok je u Krki u gornjem dijelu estuarija zabilježeno pozitivno odstupanje, a u donjem dijelu negativno odstupanje.Particulate phosphorus (PP) was investigated in the water column of the central Adriatic at 34 stations, of which 7 stations were located in coastal and 4 in the open sea area (vertical distribution), 4 stations at shellfish and fish farms (vertical distribution) and at 19 stations in the estuaries of Krka, Cetina and Jadro rivers (surface layer). At all stations concentrations of dissolved inorganic (DIP) and total phosphorus (TP) were also determined. Hydrographic parameters, concentrations of nitrogen and silicon nutrient salts and chlorophyll a were also recorded at 11 coastal and open sea stations. In seawater samples from the area of central Adriatic, two laboratory experiments were conducted in which concentrations of particulate and total phosphorus were measured over period of 9 days. PP concentrations in the coastal and open sea areas were in range from 0,007 μmol dm-3 (open sea near Palagruža Island) to 0,589 μmol dm-3 (Šibenik Bay). In the coastal area higher PP concentrations were recorded in the surface layer during spring, autumn and winter and in the bottom layer during summer.. PP concentrations in the coastal area were higher than the concentration of dissolved inorganic phosphorus, while lower in the open sea area. Statistical analysis of the results determined significant positive correlation of PP with chlorophyll a and nutrient salts of nitrogen and silicon and negative correlation with salinity. On the shellfish farms, the lowest PP concentrations were measured at the depth of the breeding shellfish. In the fish farm area, the highest concentration of PP was recorded in the layer of water column where organisms are grown. Concentrations of PP in the surface layer along estuaries of Krka, Cetina and Jadro indicate the non-conservative behavior of PP in relation to salinity. In Cetina and Jadro there was a positive deviation from the theoretical distribution of PP along the entire estuary. In the upper part of the Krka estuary there was a positive deviation and in the lower part negative deviation was recorded. Dissolved inorganic phosphorus was the most common form of phosphorus in the samples of the surface layer in all investigated estuaries