Seasonal and Spatial Changes of Primary Production in the Baltic Sea (Europe) Based on in situ Measurements in the Period of 1993–2018

Abstract

The seasonal and spatial variability of primary production (PP) measured using 14C method in two regions: open waters of the Baltic Sea and the Gulf of Gdansk were discussed. The statistical analyses of 26-years dataset (from 1993 to 2018) allow to confirm some regularities of productivity and find some features resulting mainly from changing environmental conditions like solar insolation, temperature, and chlorophyll a concentration. In the dataset, production values varied from 0.005 to 7.8 g C m–2 day–1 in open waters and from 0.07 to 12.9 g C m–2 day–1 in the Gulf of Gdansk. Analysis showed that PP in open waters were 6–17% lower than in Gulf of Gdansk in most of the cases. In both regions, the periods of intense productivity in spring and autumn were observed, but vegetation begins a month earlier in the Gulf of Gdansk than in open waters. Probably the accumulation of nutrients after the winter causes the spring bloom (April–May) in both regions to be more intense (even two times higher) than the autumn bloom (September–October) associated with favorable hydrological conditions resulting from summer insolation. The presented results showed slight downward trends in productivity in both regions, the most visible in the spring in the Bay of Gdansk. This confirms the recent reports on a possible improvement in the eutrophication state of the Baltic Sea.

Estimating the seasonal impact of optically significant water constituents on surface heating rates in the Western Baltic Sea

“…have reported a statistically significant decreasing trend of 2.11 % yr -1 of the total chlorophyll-a concentrations over last two decades (1999 to 2018), with decreasing pigment markers for such protists groups as diatoms, dinoflagellates, cryptophytes and green algae and an increase of cyanobacteria. As a consequence, primary production in the southern Baltic Sea also declined in the period from 1993 to 2018, compared to its maximum in the late 1980s (Zdun et al, 2021). Sill and Arkona Sea, these heating rate maxima were larger in May, by 0.18 and 0.35 K m -1 d -1 , respectively compared to July, while at Oder bank the heating rate maxima was larger in July by 0.1 K m -1 d -1 .…”

Photosynthesis‐Irradiance Response in the Eddy Dipole in the Western South China Sea

“…Phytoplankton convert dissolved inorganic carbon (DIC) in the ocean to organic carbon via primary production (PP), a part of the fixed carbon is transferred to the deep sea through the food web (Falkowski, 1994). PP is traditionally determined by 14 C uptake (Nielsen, 1952; Ning et al., 2004; Zdun et al., 2021), which is time consuming method and has an observational coverage limit. The net community production (NCP) estimated from the measurements of O 2 /Ar ratio allows a much finer temporal resolution and extends spatial covering (Cassar et al., 2009; Kaiser et al., 2005; Lockwood et al., 2012).…”

Copernicus Ocean State Report, issue 6

“…Still, the broad-scale spatial differences in nutrient concentrations agree with recent basin and drainage area-specific investigations. Since 1993 a slight decrease in phytoplankton primary production has been detected in the southern Baltic Sea, where Chl a concentrations are generally lower (Zdun et al 2021). Despite nutrient load reduction efforts nutrient input from rivers to the Gulf of Finland remain high as do NO 3 and Chl a concentrations (Räike et al 2020).…”