To what extent the size fraction affects an interpretation of planktonic foraminiferal assemblages - case study from Southern Adriatic

• Published in: Acta Adriatica
• Main Authors: MARKULIN, Krešimir, ĆOSOVIĆ, Vlasta
• Format: Article in Journal/Newspaper
• Language: English
• Published: Institute of Oceanography and Fisheries 2017
• Subjects: Adriatic Sea; planktonic foraminifera; size fraction; Turborotalita quinqueloba; Globigerina bulloides; Globigerinoides ruber; diversity indices; Jadransko more; planktonske foraminifere; veličina zrna; Turborotalita quinqueloba;Globigerina bulloides;Globigerinoides ruber; indeksi raznolikosti; Puta; Planktonic foraminifera
• Online Access: https://hrcak.srce.hr/185166; https://hrcak.srce.hr/file/272976

Study of planktonic foraminifera, sampled from two levels of a 26 cm thick core, recovered at 1,200 m water depth, sheds some lights on the composition of foraminiferal assemblages that occur in the Southern Adriatic. Altogether 15 planktonic species (including one referred as undeterminable and two species recorded for the first time in the eastern Adriatic Sea) identified from 0-2 cm and 24-26 cm sediment intervals, were grouped into two assemblages: >63 μm fraction Turborotalita quinqueloba and >125 μm fraction as Globigerina bulloides-Globigerinoides ruber. The differences in core-top and core-bottom assemblages lie in: a) change in the relative proportion of some species; and b) slight differences in diversity indices. The relative proportions of species are strongly controlled by sieve mesh size, whereas the slight increase in diversity follows the increase in sieve mesh size. The benthic foraminifera, although constituting a negligible quantitative factor, show a slight increase in abundance and diversity of species with age. Istraživanje planktonskih foraminifera iz dviju razina 26 cm duge jezgre izvađene sa 1,200 m dubine daje nove podatke o sastavu foraminiferskih zajednica u južnom dijelu Jadranskog mora. Ukupno 15 planktonskih vrsta (uključujući jednu neodredivu i dvije vrste koje su po prvi puta zabilježene u istočnom dijelu Jadranskog mora) određene su iz sedimentnih intervala 0-2 cm i 24-26 cm grupiranih u dvije zajednice: frakcija >63 μm nazvana Turborotalita quinqueloba, te frakcija >125 μm Globigerina bulloides -Globigerinoides ruber. Razlike između zajednica u vršnom i najdubljem dijelu jezge leže u: a) razlici u relativnim zastupljenostima nekih vrsta; b) blagim razlikama u indeksima raznolikosti. Relativni udio vrsta pod snažnim je utjecajem veličine otvora sita, gdje s povećanjem otvora sita lagano raste raznolikost. Bentičke foraminifere, iako čine neznatni kvantitativni faktor, pokazuju blago povećanje udjela i raznolikosti vrsta s dubinom sedimenta (sa starosti).