Development of a subsurface chlorophyll maximum at the entrance to the Gulf of Finland, Baltic Sea

• DOI: 10.4319/lo.1998.43.6.1089
• Publication Date: 2010-05-31T04:14:18Z
• Authors: Kaisa Kononen; Seija Hällfors; Marjaana Kokkonen; Harri Kuosa; Jaan Laanemets; Juss Pavelson; Riitta Autio
• Keywords: Diel vertical migration; Aphanizomenon; Deep chlorophyll maximum; Stratification (seeds)

Horizontal, vertical, and temporal variability of chlorophyll a (Chl ), stratification, currents, pelagial biology (phytoplankton, size‐fractionated primary productivity Chl , ciliates, picocyanobacteria, bacterial production) were followed at the entrance to Gulf Finland during 12‐day cast study in July–August 1994. The was carried out weak wind conditions when hydrodynamic activity minimal an intense blooming diazotrophic cyanobacteria Aphanizomenon flos‐aquae (Linné) Ralfs, Anabaena lemmermannii Richter Noduluria spumigena Mertens its decaying phase. property conservation equation used differentiate contributions physical biological processes local changes layer above thermocline. Subtraction change due processes, mainly advection, gave biologically induced mean decrease 0.18 mg m −3 d −1 . Sampling data confirmed calculated revealed basin‐wide character phenomenon. observed plankton dynamics showed that system “top‐down” controlled about half size‐specific grazing ciliates on dominating flagellates Chrysochromulina spp. 2–5 µm Ochromonas 7–8 upper layer. grazers confined thermocline, while inhabited both thermocline above. This led formation subsurface maximum