期刊
INLAND WATERS
卷 2, 期 3, 页码 147-162出版社
TAYLOR & FRANCIS LTD
DOI: 10.5268/IW-2.3.469
关键词
biomanipulation; eutrophication; internal load; phosphorus model; Pyhajarvi; polymictic lake
资金
- Academy of Finland [09/109, 09/074, 1071004, 1071149, 1071255, 35619, 44130, 52271, 104483, 201414, 256240]
- EU
- European Regional Development Fund
- Pyhajarvi Protection Fund
- Academy of Finland (AKA) [256240, 104483, 201414, 256240, 104483, 201414] Funding Source: Academy of Finland (AKA)
We quantified internal phosphorus (P) load for 26 years in the polymictic, large (155 km(2)) and shallow (mean depth 5.5 m) Lake Sakylan Pyhajarvi, which was heavily biomanipulated by fish removal. Internal load was estimated as (1) partially net estimates from in situ P summer increases, (2) net estimates from P budgets (mass balance approach), and (3) gross estimates from predicted active sediment release area and sediment P release, dependent on August lake temperature. Long-term averages of these estimates were similar and large at about 60% of average external load (105 mg m(-2) yr(-1)) and were larger than external load in years with high water temperature and low water load. Regression analysis revealed that external load is decreasing but internal load is increasing over time. Internal load was negatively correlated with annual water load and positively correlated with lake water temperature. Long-term average annual or summer P concentrations are adequately predicted by a P mass balance model that includes external load, internal load (Method 3), and sedimentation as independently predicted retention. Predictability was poor for individual years, however, partially due to the poor correlation of observed lake and outflow P concentrations, the variable abundance of planktivorous fish, and reflecting the violation of the steady state assumption when individual years are modeled. Scenario modeling shows that biomanipulation cancels out the effects of internal load and forecasts a rapid increase of internal load and P concentration due to climate change; therefore, measures that further decrease external and internal P load and strengthen biomanipulation are recommended.
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