Limits...
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

The development of Φ at individual stations (mean and SD) in winter surface water (0, 5, 10, 15, and 20 m) during winter from 1990 (F64 and SR5/C4 from 1993) to 2012. Upper nBP and ÅS, middle BS, lower BB. Balanced nutrients (Φ = 0) indicated
© Copyright Policy - OpenAccess
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4591228&req=5

Fig3: The development of Φ at individual stations (mean and SD) in winter surface water (0, 5, 10, 15, and 20 m) during winter from 1990 (F64 and SR5/C4 from 1993) to 2012. Upper nBP and ÅS, middle BS, lower BB. Balanced nutrients (Φ = 0) indicated

Mentions: The general trends found at the basin scale could be recognized at the individual stations for the period 1990–2011 and were consistent for stations located in the same basin (Fig. 3). The change in Φ toward more pronounced nitrogen limitation around year 2000 could be identified at all stations in the nBP and ÅS. Even if regressions were significant, the regression explained variation was low (low R-square), because of a marked nonlinear shift around the year 2000. In the BS, the shift was gradual and showed a continuous decline without marked shift, and the linear time trends were highly significant (p < 0.003, statistics in Fig. 3). The intercepts (243, 243, 215, and 178 μmol N L−1) and slopes (−0.12, −0.12, −0.11, −0.09 μmol N L−1 yr−1) found in the BS were very similar for stations SR5/C4, F26/C15, US5b/C1, and F18, respectively. Slopes became less steep, and intercepts decreased going from south to north as did R-squares (0.85, 0.71, 0.57, and 0.44, for stations as above). In the BB, there were no strong temporal trends and low values of R-square. Yearly averages were used in the regressions to avoid unintentional weighting of years since there were sporadic occurrences of missing data. Results were, however, almost identical, if all data were used instead of yearly averages.Fig. 3


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)

The development of Φ at individual stations (mean and SD) in winter surface water (0, 5, 10, 15, and 20 m) during winter from 1990 (F64 and SR5/C4 from 1993) to 2012. Upper nBP and ÅS, middle BS, lower BB. Balanced nutrients (Φ = 0) indicated
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4591228&req=5

Fig3: The development of Φ at individual stations (mean and SD) in winter surface water (0, 5, 10, 15, and 20 m) during winter from 1990 (F64 and SR5/C4 from 1993) to 2012. Upper nBP and ÅS, middle BS, lower BB. Balanced nutrients (Φ = 0) indicated
Mentions: The general trends found at the basin scale could be recognized at the individual stations for the period 1990–2011 and were consistent for stations located in the same basin (Fig. 3). The change in Φ toward more pronounced nitrogen limitation around year 2000 could be identified at all stations in the nBP and ÅS. Even if regressions were significant, the regression explained variation was low (low R-square), because of a marked nonlinear shift around the year 2000. In the BS, the shift was gradual and showed a continuous decline without marked shift, and the linear time trends were highly significant (p < 0.003, statistics in Fig. 3). The intercepts (243, 243, 215, and 178 μmol N L−1) and slopes (−0.12, −0.12, −0.11, −0.09 μmol N L−1 yr−1) found in the BS were very similar for stations SR5/C4, F26/C15, US5b/C1, and F18, respectively. Slopes became less steep, and intercepts decreased going from south to north as did R-squares (0.85, 0.71, 0.57, and 0.44, for stations as above). In the BB, there were no strong temporal trends and low values of R-square. Yearly averages were used in the regressions to avoid unintentional weighting of years since there were sporadic occurrences of missing data. Results were, however, almost identical, if all data were used instead of yearly averages.Fig. 3

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