10/25/2011. Salomon van Ruysdael 1648

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1 CyanoHABs in China: The Need for Nitrogen and Phosphorus Input Reductions to Control Eutrophication Hans Paerl (UNC-CH CH IMS), Xu Hai, Guangwei Xu & Boqiang Qin (NIGLAS) Human nutrient over-enrichment enrichment & eutrophication: There s a long history Salomon van Ruysdael

2 In some of China s largest lakes, this is compressed into only a few decades! L. Taihu, Jiangsu Province L. Dianchi, Yunnan Province The drinking water crisis in Wuxi (Taihu Taihu),

Key Players Unicellular, (non-n 2 fixing)

non-heterocystous (mostly non-n 2 fixing)

Nodularia* * Contains toxic strains Key Nutrient

no longer just P that s controlling blooms!

Input ratios are important (N:P < 15 favors N 2

3 Key Players Unicellular, (non-n 2 fixing) Microcystis*, Gomphosphaeria Filamentous, non-heterocystous (mostly non-n 2 fixing) Lyngbya*, Oscillatoria*, Planktothrix* Filamentous, heterocystous (N 2 fixing) Anabaena*, Aphanizomenon*, Cylindrospermopsis*, Nodularia* * Contains toxic strains Key Nutrient Issues Both N & P enrichments are stimulatory Its no longer just P that s controlling blooms! N is playing an increasingly important role N:P Input ratios are important (N:P < 15 favors N 2 Fixers) chemical forms of N (i.e. NO 3, NH 4, organic N) can control algal community composition/function 3

Sources of nutrients (N&P) in Taihu Urban wastewater and industry (~ 40%) NPS Runoff (Dominated by agriculture) (~ 35 %) Atmospheric (fossil fuels & Ag) (~ 25 %) Nutrient dynamics: Inferring nutrient

4 Sources of nutrients (N&P) in Taihu Urban wastewater and industry (~ 40%) NPS Runoff (Dominated by agriculture) (~ 35 %) Atmospheric (fossil fuels & Ag) (~ 25 %) Nutrient dynamics: Inferring nutrient limitation of phytoplankton production in Taihu 90 station-1 station-2 A TN/TP J F MAMJ J AS ONDJ F MAMJ J AS ONDJ F MAMJ J ASOND P DTN/DTP B station-1 station-2 J FMAMJ J ASONDJ FMAMJ J ASONDJ FMAMJ J ASOND Nutrient (N&P) ratios in Taihu Redfield (balanced growth) 15:1 (N:P) Conclusion: P appears limiting in winter-spring, N is limniting in summer-fall 4

5 Letting the algae tell us: in situ nutrient addition/dilution bioassays Effects of nutrient (N & P) additions on phytoplankton production (Chl a) in Lake Taihu, China: Both N & P inputs matter!! Xu et al. 2010; Paerl et al

America, Europe, Asia Taihu, China (e.g.

6 The visual evidence for N & P co-limitation in Taihu Some N or N & P limited Lakes Lake Tahoe, USA Lake Okeechobee, USA Lake Taupo, NZ Lakes Erie & Superior, USA/Canada Lake Victoria, Africa Great Salt Lake, USA Lake Titicaca, S. America High mountain lakes, N. America, Europe, Asia Numerous reservoirs in N. America, Europe, Asia Taihu, China (e.g., Horne and Goldman 1994; Wetzel 2001; Elser et al. 2007, 2009; Lewis and Wurtsbaugh 2008, Sterner 2008; Leavitt et al. 2010) 6

7 Effects of different nitrogen sources on Taihu s CyanoHAB potential Influence of N sources on cyanobacterial dominance: Lake Njupfatet, Sweden + ammonium-n + nitrate-n Blomqvist et al

Form of N matters: NH 4 favors CyanoHABs in NC estuaries 15 12 Bogue Sound Bioassay August, 1996 15 Chl a 12 Fucoxanthin All phytos Concentration (mg m -3 ) 9 6 3 0 5 4 Control Nitrate Ammonium

8 Form of N matters: NH 4 favors CyanoHABs in NC estuaries Bogue Sound Bioassay August, Chl a 12 Fucoxanthin All phytos Concentration (mg m -3 ) Control Nitrate Ammonium Alloxanthin Control Nitrate Ammonium Zeaxanthin diatoms cryptophytes 0 Control Nitrate Ammonium 0 Control Nitrate Ammonium cyanobacteria Treatment Conclusions & what s next? Phytoplankton production in Taihu is dual nutrient (N & P) limited. Similar to other large lake & estuarine ecosystems. In winter-spring bloom, N appears in excess, while in the summer N appears to be limiting (i.e. P is limiting in spring while N is limiting in summer). Dilution bioassays are determining nutrient excesses and % reductions needed to control algal growth, especially during spring-summer, summer, when harmful cyanobacterial blooms (CyanoHABs) occur. Examining potential for N2 fixing CyanoHABs. Initial evidence: >50% reduction in N and P inputs will be needed to control eutrophication and blooms. This is not surprising, considering accelerating nutrient inputs! 8

9 There s one additional twist: Climate change Specifically warming 2003 was the hottest summer in 500 years in Europe! 2005 was the hottest year ever in N. America China s been setting records since 2005!! Huisman et al. 2006, KNMI, De Bilt 9

10 Air/water temperature records for Shanghai & Taihu Microcystis Buoyant CyanoHAB favored by Stronger Stratification (Paerl and Huisman 2009) 10

11 and temperature affects growth rates diatoms Microcystis Reynolds 1997; Paerl et al Mid August 2003: Lake Nieuwe Meer, Holland Heatwave & little mixing Microcystis benefits! B Jöhnk et al

12 Testing the Model Theory Lake data B A = mixing off B = mixing on Huisman et al., 2004 Global warming, associated climate change and CyanoHAB potential 12

non-cyanobacterial taxa Caveats: : must accompany overall nutrient reduction; at high

13 So What s Feasible? CyanoHAB Control & Management Nutrient input reductions N, P, N&P, Fe? Must establish bloom thresholds (especially with regard to warming) & resolve timing issues Dual N&P reductions are often most effective Nutrient ratio manipulations Molar N:P >15 favors non-cyanobacterial taxa Caveats: : must accompany overall nutrient reduction; at high N concentrations non-n 2 fixing cyanos (e.g. Microcystis, Lyngbya, Oscillatoria) may still dominate Reduce water residence time Increase flushing rate, if water supply is available Less feasible as water supplies dwindle Biomanipulation? Experimental, ecosystem consequences must be assessed Thanks to NC Sea Grant, NSF, USDA, EPA-STAR, NC-DENR (ModMon), St Johns R. Water Management District, FL, Chinese Academy of Sciences (NIGLAS) Special Thanks to: Jeremy Braddy, Melissa Hoffman, Alan Joyner, Ben Peierls, Pia Moisander, Karen Rossignol, Amy Waggener, Pam Wyrick R

14 Why does N limitation persist? There s plenty of N2 fixing taxa to potentially supply N 14

Controls on N 2 fixation, it isn t just P or N:P Other controls energy constraints Photosynthesis Heterotrophy Chemolithotrophy Fe

Dinitrogen gas flux from several eutrophic lakes indicates net loss (negative net N 2 flux) of reactive nitrogen to the atmosphere.

5 Lake Mendota, Wisconsin, USA 10 1.0 12 1.2-0.2 Lake Okeechobee, Florida, USA 0.8 3.5 0.3 3.0-2.2 to 0.5 Lake Erken, Sweden 0.5 1.2-0.7 *Experimental Lakes Area From: Paerl & Scott (2010) ES&T And marine systems?

met by N fixation Oceans World oceans (total) <0.04 10% W. Central Sargasso Sea <0.1 20% North Pacific Gyre <0.

15 Controls on N 2 fixation, it isn t just P or N:P Other controls energy constraints Photosynthesis Heterotrophy Chemolithotrophy Fe limitation 4 Fe S 2 Fe Mo MW=60.5 KD (V) MW=245 KD O 2 Does N 2 Fixation meet N demands in lakes? Dinitrogen gas flux from several eutrophic lakes indicates net loss (negative net N 2 flux) of reactive nitrogen to the atmosphere. N 2 Flux (g N m -2 yr -1 ) Nitrogen Lake Fixation Denitrification Net N 2 Flux Lake 227 (ELA*), Canada to -4.5 Lake Mendota, Wisconsin, USA Lake Okeechobee, Florida, USA to 0.5 Lake Erken, Sweden *Experimental Lakes Area From: Paerl & Scott (2010) ES&T And marine systems? N 2 fixation supplies only a portion of N needed to support ecosystem primary production They remain N or N+P limited % total N needs met by N fixation Oceans World oceans (total) < % W. Central Sargasso Sea <0.1 20% North Pacific Gyre < % Estuaries Bothnian Sea (Baltic) <5 Baltic proper Harvey Estuary, Australia 17 Neuse River Estuary, North Carolina <3 15

Florida lakes : Cylindrospermopsis raciborskii,, rapidly- proliferating, toxic N 2 fixing cyanohab High P

often significantly increase growth (chl a and cell counts) and productivity N 2 fixer (can supply its own N

column with other cyanohabs St. Johns R.

ts/ml 300 250 200 150 100 50 0 14000 12000 10000 8000 6000 4000 2000 0 1 day 4 days control +N +P +N&P C.

16 Florida lakes : Cylindrospermopsis raciborskii,, rapidly- proliferating, toxic N 2 fixing cyanohab High P uptake and storage capacity High NH + 4 uptake affinity (competes well for N) N additions (NO NH + 4 ) often significantly increase growth (chl a and cell counts) and productivity N 2 fixer (can supply its own N needs) Tolerates low light intensities Eutrophication/decreased transparency favors Cylindro Often in water column with other cyanohabs St. Johns R. System, FLorida: Nitrogen and Phosphorus Effects on CyanoHAB Growth and Bloom Potential mg C m-3 h-1 unit ts/ml day 4 days control +N +P +N&P C. raciborskii control +N +P +N&P Take home message: Cylindrospermopsis raciborskii is opportunistic Dual N & P input constraints will likely be needed to control it Piehler et al,

17 17

The Baltic Sea: N 2 fixers, but rates don t

controls N 2 fixation Acetylene reduction

01 60 40 20 0 0 5 10 15 20 25 30 Upper mixed

18 The Baltic Sea: N 2 fixers, but rates don t meet ecosystem N demands ~ 30% (Elmgren and Larsson 2001; Wulff et al. 2006) Example: Turbulence in the Baltic Sea controls N 2 fixation Acetylene reduction (µmol C2H4 m 2 h -1 ) r= ; p< Upper mixed layer depth (m) Take home message: Mixing depth (physics) matters Moisander

Human nutrient over-enrichment in coastal waterways and deltas; There s a long history

www.marine.unc.edu/paerllab Human nutrient over-enrichment in coastal waterways and deltas; There s a long history Salomon van Ruysdael 1648 1 RN (ton/yr) Mississippi R. Basin Choptank R, Chesapeake Bay