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Increasing nitrogen limitation in the Bothnian Sea, potentially caused by inflow of phosphate-rich water from the Baltic Proper.

Rolff C, Elfwing T - Ambio (2015)

Bottom Line: This is affected by the by inflow of phosphate-rich and oxygen-depleted water from depths near the halocline in the northern Baltic Proper, where severe oxygen conditions currently cause extreme phosphate concentrations in the deep water.The change in relation between inorganic nitrogen and phosphorous in the BS occurs first in the deep water and then progresses to the surface water.The change can potentially cause increased production in the BS and more frequent cyanobacterial blooms.

View Article: PubMed Central - PubMed

Affiliation: Stockholm University Baltic Sea Centre, 106 91, Stockholm, Sweden. carl.rolff@su.se.

ABSTRACT
The study showed that the open water of the Bothnian Sea (BS) is likely to have shifted from altering nitrogen and phosphorous limitations of the spring bloom to more nitrogen-limited conditions during the last 20 years. This is affected by the by inflow of phosphate-rich and oxygen-depleted water from depths near the halocline in the northern Baltic Proper, where severe oxygen conditions currently cause extreme phosphate concentrations in the deep water. The change in relation between inorganic nitrogen and phosphorous in the BS occurs first in the deep water and then progresses to the surface water. The change can potentially cause increased production in the BS and more frequent cyanobacterial blooms. There does not appear to be any immediate concern in the short-term perspective for the state of the BS, but a progression of the processes may lead to a more eutrophic state of the BS.

No MeSH data available.


Related in: MedlinePlus

November–December salinity, oxygen, phosphate, DIN, and Φ values in surface water (0, 5, 10, 15, and 20 m) and deep water (80, 90, and 100 m) at station SR5/C4 (mean and SD). Changes in the deep water precede those of the surface water
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Fig6: November–December salinity, oxygen, phosphate, DIN, and Φ values in surface water (0, 5, 10, 15, and 20 m) and deep water (80, 90, and 100 m) at station SR5/C4 (mean and SD). Changes in the deep water precede those of the surface water

Mentions: From 1994 to 2012, there were no strong trends in external loads to the BS with uncertain estimates suggesting a somewhat greater relative reduction of phosphorous load in relation to nitrogen load on a weight basis (HELCOM 2013). The trends in the water column of the nBP, however, corresponded with damped equivalents in the BS (Fig. 4). The hypoxia and elevated concentrations of phosphate found at 50–60-m depth in the nBP are thus likely to be the main cause of the decreasing oxygen concentration and increasing phosphate concentration in the deep water of the BS (Fig. 4). The trend toward more nitrogen-limited conditions in the BS is likely to be driven by inflow of phosphate-rich water from the nBP, forming deep water in the BS since there is no consistent trend in DIN concentration in the water column (Fig. 6). For all the key variables, changes in the deep water precede the corresponding changes in surface water. Generally speaking, these are increasing deep water salinity, decreasing oxygen concentration below the halocline, increasing phosphate concentration, and variable trends in DIN. All trends were most pronounced below the halocline.Fig. 6


Increasing nitrogen limitation in the Bothnian Sea, potentially caused by inflow of phosphate-rich water from the Baltic Proper.

Rolff C, Elfwing T - Ambio (2015)

November–December salinity, oxygen, phosphate, DIN, and Φ values in surface water (0, 5, 10, 15, and 20 m) and deep water (80, 90, and 100 m) at station SR5/C4 (mean and SD). Changes in the deep water precede those of the surface water
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4591228&req=5

Fig6: November–December salinity, oxygen, phosphate, DIN, and Φ values in surface water (0, 5, 10, 15, and 20 m) and deep water (80, 90, and 100 m) at station SR5/C4 (mean and SD). Changes in the deep water precede those of the surface water
Mentions: From 1994 to 2012, there were no strong trends in external loads to the BS with uncertain estimates suggesting a somewhat greater relative reduction of phosphorous load in relation to nitrogen load on a weight basis (HELCOM 2013). The trends in the water column of the nBP, however, corresponded with damped equivalents in the BS (Fig. 4). The hypoxia and elevated concentrations of phosphate found at 50–60-m depth in the nBP are thus likely to be the main cause of the decreasing oxygen concentration and increasing phosphate concentration in the deep water of the BS (Fig. 4). The trend toward more nitrogen-limited conditions in the BS is likely to be driven by inflow of phosphate-rich water from the nBP, forming deep water in the BS since there is no consistent trend in DIN concentration in the water column (Fig. 6). For all the key variables, changes in the deep water precede the corresponding changes in surface water. Generally speaking, these are increasing deep water salinity, decreasing oxygen concentration below the halocline, increasing phosphate concentration, and variable trends in DIN. All trends were most pronounced below the halocline.Fig. 6

Bottom Line: This is affected by the by inflow of phosphate-rich and oxygen-depleted water from depths near the halocline in the northern Baltic Proper, where severe oxygen conditions currently cause extreme phosphate concentrations in the deep water.The change in relation between inorganic nitrogen and phosphorous in the BS occurs first in the deep water and then progresses to the surface water.The change can potentially cause increased production in the BS and more frequent cyanobacterial blooms.

View Article: PubMed Central - PubMed

Affiliation: Stockholm University Baltic Sea Centre, 106 91, Stockholm, Sweden. carl.rolff@su.se.

ABSTRACT
The study showed that the open water of the Bothnian Sea (BS) is likely to have shifted from altering nitrogen and phosphorous limitations of the spring bloom to more nitrogen-limited conditions during the last 20 years. This is affected by the by inflow of phosphate-rich and oxygen-depleted water from depths near the halocline in the northern Baltic Proper, where severe oxygen conditions currently cause extreme phosphate concentrations in the deep water. The change in relation between inorganic nitrogen and phosphorous in the BS occurs first in the deep water and then progresses to the surface water. The change can potentially cause increased production in the BS and more frequent cyanobacterial blooms. There does not appear to be any immediate concern in the short-term perspective for the state of the BS, but a progression of the processes may lead to a more eutrophic state of the BS.

No MeSH data available.


Related in: MedlinePlus