Control of Phytoplankton Growth: Nitrogen, Phosphorus, or Grazers?
•David Wong1, Nancy N Rabalais2,3, R. Eugene Turner3, Ling Ren4
•1.Massachusetts Department of Environmental Protection •2.Louisiana Universities Marine Consortium •3.Louisiana State University •4.George Mason University Primary production (P): P Growth t Mortality
Advectionx, y,z
Diffusionx, y,z Sinking
•Frost 1991 Phytoplankton Growth Control in Lakes
• Bottom-up Control: Nutrient Limitation on Phytoplankton Growth
• Top-down Control: Microzooplankton, mesozooplankton, and Bivalves
Upper •New Orleans Barataria Basin
•Davis Pond Diversion •Lac des Allemands •Lake •Cataouatche
•Lake Salvador Phytoplankton Growth Control
• Bottom-up Control: Nutrient Limitation on Phytoplankton Growth
• Top-down Control: Microzooplankton, mesozooplankton, and Bivalves
Experimental Lakes
• Lac des Allemands
• Lake Salvador
•Wong et al. 2016 The physical conditions during the experiments: ambient lake salinity and Secchi disk depth, experiment duration
•Ren et al. 2009 Nutrient Limitation Experiments • +N • +P, • +Si • +N+P • +N+Si • +P+Si • +N+P+Si • Control Nutrient Limitation Experiments
• Nitrite+Nitrate • Phosphate • Ammonium • Silicate • Chl a • Phytoplankton Identification • Phytoplankton Enumeration • Suspended Particulate Matter
• Samples taken at Time 0h, 6h, 12h, • Temp and 24h, • Solar Radiation • Every 24h after the first day and ended when Chl a started to • Light Intensity decrease
The initial concentration of chlorophyll a (Chla), SPM, nutrients in lake waters, and the added nutrients in the bioassay experiments
•Ren et al. 2009 Composition of phytoplankton (biovolume %)
•Ren et al. 2009 Lake Cataouatche Lake Salvador Lac des Allemands
The changes in Chl a concentration in response to N additions were different for all experiments
•Ren et al. 2009 Five bioassays with N additions ( N, N + P, N + Si, and N+P+Si)
• The concentration of Chl a increased significantly after N additions (i.e., after adding N, N + P, N + Si, and N+P+Si)
• The addition of +Si,+P, and Si+P did not result in an increase in Chl a
• N was the only limiting nutrient for phytoplankton growth in these five experiments
Lake Cataouatche Lake Salvador Lac des Allemands
The changes in Chl a concentration in response to N+P but More strongly By N than P Because +P Alone did not stimulate Additional growth
•Ren et al. 2009 Lake Cataouatche Lake Salvador Lac des Allemands
The addition of P Only resulted in marginally elevated Chl a concentration (P = 0.03) but was much less than N Additions (P < 0.001)
•Ren et al. 2009 Chl a responses to nutrient additions and the results of nutrient limitation from bioassays
+N > +P > +Si +N > +P > +N+P +N+P > Lakes Date Control Control >Control +P +N >+N +P Limitation
Cataouatche 3-Oct y – – y – – y N 4-Jan y – – y – y y N+P 4-Apr y – – y – y y N+P 4-Jul y – – y – y y N+P
Salvador 3-Oct y – – y – – y N 4-Jan y P=0.03 – y – – y N,P 4-Apr y – – y – y y N+P 4-Jul y – – y – – y N des Allemands 3-Oct y – – y – – y N 4-Jan y P=0.03 – y – – y N,P 4-Apr y – – y – y y N+P 4-Jul y – – y – – y N
•Ren et al. 2009 Chl a responses to nutrient additions and the results of nutrient limitation from bioassays Nutrient Lakes deficiency Ndef Pdef Ndef/Pdef Cataouatche 6.9 0.6 12 4.9 3.2 1.5 3.5 0.9 3.5 5.2 3.2 1.6
Salvador 6.2 0.4 16 0.6 0.2 3 6.1 5.1 1.2 5.6 0.04 140 des
•Ren et al. 2009 Allemands 1.3 0.02 65 0.2 0.04 5 1.1 0.3 3.4 0.9 0.07 12 The Nutrient Limitation Experiments
• The results of these bioassays show that the phytoplankton growth in the lakes in upper Barataria Basin are primarily N- limited • P colimitation occurs - when it does, P is a secondary limiting nutrient Phytoplankton Growth Control
• Bottom-up Control: Nutrient Limitation on Phytoplankton Growth
• Top-down Control: Microzooplankton, mesozooplankton, and Bivalves
Grazers Flagellates Ciliates Pelagic Community Rotifers Copepods Cladocerans Meroplankton larvae
Bivalve molluscs Sponges Benthic Community Corals Cnidarians Tunicates
Top-Down Control by Grazers
• Microzooplankton • Mesozooplankton • Benthic grazer: Rangia clam Microzooplankton (< 200 µm) Microzooplankton Grazing Experiment
Dilution Method (Landry et al. 1998)
202 m 0.2 m P = P e ( - m)t screened filtered t 0 water water - m = 1/t Ln (Pt / P0) 100 % 0% 1/t Ln (Pt / P0) = - m D + Dilution 100% 0% D: Dilution factor 50% 50% m: Microzooplankton Incubation 25% 75% grazing : Phytoplankton growth 12.5% 87.5% rate 6.25% 93.75% Lake Cataouatche
Season Phytoplankton size Line R N P value Grazing rate (day -1)
Fall 2003 < 5 micro y = -0.33x + 0.72 0.69 24 <0.01 0.33 5-20 micro * 0 > 20 micro * 0 Total phytoplankton y = -0.07x + 0.88 0.44 24 <0.01 0.07
Winter 2004 < 5 micro y = -0.57x + 0.35 0.77 24 <0.01 0.57 5-20 micro * 0 > 20 micro * 0 Total phytoplankton y = -0.22x + 0.34 0.84 24 <0.01 0.23
Spring 2004 < 5 micro ** 0.23 5-20 micro ** 0.67 > 20 micro * 0 Total phytoplankton * 0
Summer 2004 < 5 micro * 0 5-20 micro y = -0.90x + 1.84 0.84 24 <0.01 0.91 > 20 micro * 0 Total phytoplankton ** 0.04 Wong et al. 2016 Lake Salvador
Season Phytoplankton size Line R N P value Grazing rate (day -1)
Fall 2003 < 5 micro y = -0.85x + 0.85 0.87 24 <0.01 0.85 5-20 micro y = -0.34x + 1.02 0.74 24 <0.01 0.34 > 20 micro y = -0.19x + 0.10 0.44 24 <0.01 0.19 Total phytoplankton y = -0.63x + 0.89 0.89 24 <0.01 0.63
Winter 2004 < 5 micro y = -0.74x + 0.30 0.84 24 <0.01 0.74 5-20 micro * 0 > 20 micro y = -0.18x + 0.43 0.55 24 <0.01 0.18 Total phytoplankton y = -0.16x + 0.26 0.69 24 <0.01 0.16
Spring 2004 < 5 micro y = -0.46x + 0.47 0.52 24 <0.01 0.46 5-20 micro * 0 > 20 micro y = -0.64x + 0.89 0.54 24 <0.01 0.64 Total phytoplankton y = -0.44x + 0.97 0.85 24 <0.01 0.44
Summer 2004 < 5 micro y = -0.56x + 1.30 0.95 24 <0.01 0.56 5-20 micro y = -0.37x + 1.63 0.81 24 <0.01 0.37 > 20 micro y = -0.44x + 1.39 0.73 24 <0.01 0.44 Total phytoplankton y = -0.47x + 1.39 0.95 24 <0.01 0.47 Wong et al. 2016 Lac des Allemands
Season Phytoplankton size Line R N P value Grazing rate (day -1) Fall 2003 < 5 micro y = -0.18x + 0.74 0.49 24 <0.01 0.18 5-20 micro y = -0.36x + 0.85 0.85 24 <0.01 0.36 > 20 micro y = -0.37x + 0.73 0.54 24 <0.01 0.37 Total phytoplankton y = -0.23x + 0.75 0.87 24 <0.01 0.23
Winter 2004 < 5 micro * 0 5-20 micro * 0 > 20 micro * 0 Total phytoplankton * 0
Spring 2004 < 5 micro y = -0.31x + 0.15 0.84 24 <0.01 0.31 5-20 micro * 0 > 20 micro * 0 Total phytoplankton y = -0.14x + 0.12 0.75 24 <0.01 0.14
Summer 2004 < 5 micro * 0 5-20 micro * 0 > 20 micro * 0 Total phytoplankton * 0 Wong et al. 2016 Microzooplankton Grazing Rate
) 0.5 -1 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05
Microzooplankton grazing rate (day rate grazing Microzooplankton 0 < 5 micro 5 - 20 micro > 20 micro
Wong et al. 2016 •0.5 •Instantaneous growth rate • Apparent growth rate •0.4
•0.3 c
)
•
1
-
• •0.2
b •0.1
•0 Growth rate (day rate Growth
• •-0.1
< 5 m •-0.2 5 - 20 m •-0.3 > 20 m a •-0.4 Phytoplankton size composition
80 70 60 < 5 micro 50 40 5-20 micro 30 20 Percentage (%) Percentage 10 > 20 micro 0 0 50 100 150 200 Chlorophyll a (microgram l -1)
Wong et al. 2016 Selective grazing by microzooplankton (Hansen et al. 1994)
The size ratio between planktonic predators (Rotifers between 50 to 200 micro) and their preys (Phytoplankton) 18 : 1
Phytoplankton between 2.5 to 12 micro will be mostly consumed < 5 micro and 5 – 20 micro were impacted > 20 micro no significant impact
Grazing on phytoplankton
1.0 < 5 m
0.8 Y = 0.44 X + 0.25
) 1 - 5-20 m 0.6 Y = 0.53 X + 0.05
0.4 > 20 m Not Significant
0.2
Grazing rate (d rate Grazing Total phytoplankton
0.0 Y = 0.29 X + 0.14
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Instantaneous phytoplankton growth rate (d-1) Mesozooplankton (> 200µm) Mesozooplankton Grazing
1.8 2.5
) ) < 5 micro
-1 -1 1.6 Plot 1 Regr 5-20 micro 2.0 1.4 > 20 micro Total phytoplankton 1.2 1.5 1.0
0.8 1.0
0.6 0.5 0.4
0.2 0.0 0.0
Phytoplankton apparent growth rate (d rate growthapparent Phytoplankton
Phytoplankton apparentgrowth rate (d
-0.2 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Zooplankton density (x Natural density) Zooplankton density (x Natural density)
Lac des Allemands Lake Salvador
Wong et al. 2016 Benthic Grazers: Rangia Clam (Rangia cuneata)
Wong et al. 2010 Sample Collection Benthic grazers experiments: Rangia clams (Individuals m-2)
•Lac des Allemands •L. Cataouatche
•L. Salvador Grazing on Phytoplankton
Lake Salvador Lac des Allemands 3.6 Control 60 3.4 Clam Control Clam ) 55 3.2
)
-1
3.0 -1 50
2.8 45 2.6 40
2.4 Ch l a (ug l
Ch l a (ug l 2.2 35
2.0 30 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Time (h) Time (h)
Wong et al. 2010 Top-Down Control on Phytoplankton by Clams
4.6 107 M3 Day-1 • Lac des Allemands
2.15 108 M3 Day-1 • Lake Salvador Top-Down Control of Clams
1.5 Days • Lac des Allemands
1 Days • Lake Salvador Potential Top Down Control by Rangia clam
Pumping: 24 Pumping: 12 Clearing 50% of Lake hours a day hours a day the lake (day)
Lake Salvador 1 2.1 1.5
Lac des Allemands 1.5 3 2.1
Wong et al. 2016 Can Suspension Feeders Control Phytoplankton ?
Lake Salvador Des Allemands
Phytoplankton growth (Day –1) 0.28 0.34 Microzooplankton grazing (Day –1) 0.42 0.09 Mesozooplankton grazing (Day -1) 0 0
Phytoplankton doubling (Day) 8 2.7 Clams clearing half of the volume 1.5 2.1 Control on phytoplankton ? Yes ? - No Chlorophyll a (g L –1) in water 10.5 61.8 Chlorophyll a (g g –1) in sediment 32.4 116.8 surface Sediment Phaeopigment and Chl a
60 200 Sedimentphaeopigment(mgg
180
1) 50 - Chl a Phaeopigment 160 140 40 120 30 100 80 20 60 40 10
20
-
1) Sediment chlorophyll chlorophyll g (mg a Sediment
0 0 0 20 40 60 80 Water chlorophyll a (mg l -1)
Wong et al. 2016 Lac des Allemands: Hypoxia
Oxygen content in the water (mg l -1)
0 2 4 6 8 10 12 0.0 A
0.5
1.0
1.5
Water depth (m) 2.0
Lake Cataouatche 2.5 Lake Salvador Lac des Allemands Hypoxia = 2.0 mg l-1 3.0 Lac des Allemands
•Photo by David Wong • Mytilus edulis • Crassostrea virginica Photo by David Wong Suspension Feeders Photo by David Malosh
Eutrophication
Nutrient Enrichment
Cape Cod Area Water Quality Management Plan
Acknowledgement
Quay Dortch Nazan Atilla •National Oceanic & Atmospheric Claude J. Pirtle Administration, Center for Sponsored Jenn Lynn Coastal Ocean Research, Coastal Warren Mendenhall Ocean Program Wendy Morrison Lora Pride •Massachusetts Department of Kyle Reynolds Environmental Protection Adam Sapp Undergraduate and Graduate students Thank You