Under the Radar: Long-term perspectives on ecosystem changes in - PowerPoint PPT Presentation

Under the Radar: Long-term perspectives on ecosystem changes in lakes John P. Smol Professor and Canada Research Chair in Environmental Change Paleoecological Environmental Assessment and Research Laboratory (PEARL) Queen’s University, Kingston, Ontario, Canada SmolJ@QueensU.Ca

Notwithstanding major advances in our lives, our relationship with the environment has been riddled with unintended consequences.

The Anthropocene: The period of human- dominated Earth’s history http://tothewire.wordpress.com/2009/08/21/the-anthropocene-era-is-man-dominating-nature/ http://seedmagazine.com/content/world/

Important management questions What were pre-disturbance conditions? What is the range of natural variability? Have conditions changed? How much? How fast? When? Why?

Smol, 2019, Proc Roy Soc B

Techniques to Assess Environmental Change historical records and traditional knowledge modeling natural archives

Paleolimnology: Sediments as environmental archives e.g. aerially transported contaminants e.g. pollen grains outside material e.g. soil particles within lake material e.g. algae & aquatic insects

Surface sediment gravity coring

Close-interval sectioning

Dating the sedimentary sequences • 210 Pb & 137 Cs (radioisotopes) Youngest 2006 2005 2004 0 2003 2002 2 2001 1999 4 ~1963 1998 6 1996 Continuous Record 8 1994 10 1992 1990 12 Core Depth (cm) 1987 14 1985 16 1981 18 1976 20 1972 1965 22 1950 24 1946 214 Bi 26 1936 1926 28 137 Cs 1920 30 1910 1900 32 1890 210 Pb 34 1870 1860 36 1856 10 15 20 25 30 35 40 45 50 -5 0 5 1850 Oldest Activity (dpm/g) 1846

From the Atmosphere metals and other carbon particles fly ash from coal pollutants from from carbon combustion industry combustion

From the Catchment mineral insect pollen particles remains beetle wing

From the Aquatic System algae cladocerans chironomids

In addition to morphological fossils, there is a growing suite of biogeochemical indicators. Phycoerythrin (e.g. fossil pigments, environmental DNA, etc.)

Sterols & stanols Redrawn from: Leeming et al. 1996 Water Res.

The Paleolimnological Approach 210 Pb 137 Cs 14 C Select Study Lake Select Coring Site & Section & Date Sediment Core Retrieve Sediment Core Analyze Data Sub-sample Sediments & Isolate Indicator of Interest Collect Indicator Data Photos courtesy of B. Cumming, I. Walker, Dell & Leic

• Targets • Trajectories

What factors can be addressed using paleolimnology? eutrophication anoxia and fish habitat climate change acidification groundwater quality river paleoecology fire history species invasion speciation / evolution, etc.

Eutrophication

Impacts of Cultural Eutrophication -  algal growth and toxins -  plant growth - shoreline fouling - taste and odour problems - P release - hypolimnetic anoxia -  accumulation and decay - fish kills - presence of undesirable species - aesthetic degradation

Three lake characteristics we typically wish to track 1) Lakewater nutrient levels 2) Deepwater oxygen levels 3) Algal and cyanobacterial blooms

1) Trends in lakewater nutrients Why not just measure total P in the sediments? Many pitfalls and largely abandoned ~30 years ago (this is not to say that sedimentary P has no value in other applications – very important in mass balance studies and determining processes, etc.)

So we have to use indirect proxy methods that are related to lakewater total phosphorus (TP) Research ongoing for over 30 years, but especially last 20 years

Freshwater diatoms Photos: K. Laird and B. Cumming; Fig. 5.5 in Smol (2008)

Develop a “paleo TP meter” sp. 4 sp. 1 Abundance of taxa sp. 3 sp. 5 sp. 6 sp. 2 Environmental variable ( e.g. TP)

2) Deepwater oxygen levels? Use organisms that need oxygen, and live in the deep waters http://www.nzfreshwater.org/food.html

Chironomid life cycle (Drawing: Walker 1987) http://www.ec.gc.ca/ceqg-rcqe/images/SAS/fact3_img2.jpg

Chironomid head capsules as indicators Chironomus Chironomus mentum Using fossil assemblage data we develop a 5 mm “paleo - oxygen meter”.

3) Algal and cyanobacterial blooms Photo Todd Sellers

Not all groups leave reliable morphological fossils Biogeochemical indicators, such as fossil pigments, DNA, and preserved microcystin toxins may be used.

Increasing cyanobloom reports across Ontario 2009 • 2010 26% from oligotrophic lakes 2011 2012 (Winter et al. 2011) 2013 2014 Blue-green algae (cyanobacteria) blooms 70 # reports confirmed as blooms 60 50 40 66 30 54 51 51 20 31 31 27 25 24 10 19 17 16 14 0 Winter et al. 2011, Lake and Res. Manage., Updated by OMOECP 2018; M. Palmer (unpub. Data)

Climate change: The new “threat multiplier” www.ccepr.org/liu/researchCC_en.html

Without question, you need a minimum amount of nutrients (P, N, etc.) to generate algal biomass. But people are recording increased algal blooms, even in lakes with steady or declining nutrient levels.

Example #1 Can climate change be affecting algal blooms, even without increases in nutrients? 1) The “longer summer” (less ice cover) 2) Enhanced thermal stratification

Lake of the Woods (almost a Great Lake - 2 provinces and 1 state)

LOW: External phosphorus load LOWER P HIGHER P Rainy River = primary source of TP to LOW (Hargan et al. 2011) P load from Rainy River decreased from ~1500 t/year (1960- 1975) to ~500 t/year (post-1990) (Reavie et al. 2017 LRM)

AND YET… nuisance algal blooms are being reported Satellite image of blue-green algae blooms widespread across LOW, Sept. 1, 2015. Susie the dog surveys an algal bloom in October. Credit: Todd Sellers Credit: MODIS, University of Wisconsin Space Science and Engineering Center

Is there a disconnect in Lake of the Woods? = Perception blue-green blooms have A decline in TP loading. increased in intensity and duration in recent years. (Photo: T. Sellers)

Whitefish Bay TP <10 µg/L 1975 42 % Relative Abundance Rühland et al. 2010. Limnol. Oceanogr.

Lake of the Woods, Canada and USA - temperature Whitefish Bay – Reference site Annual Temperature Cyclotella spp Aulacoseira spp 4.5 50 4.0 40 3.5 30 3.0 Annual Temperature (ºC) Relative Abundance (%) 20 2.5 10 2.0 0 1.5 R = 0.73 1.0 1900 1920 1940 1960 1980 2000 2020 4.5 60 4.0 50 3.5 40 3.0 2.5 30 2.0 20 1.5 R = - 0.65 1.0 10 1900 1920 1940 1960 1980 2000 2020 Year AD Rühland, Paterson, Smol 2008: Global Change Biology

Lake of the Woods, Canada and USA – lake ice data Whitefish Bay – Reference site Ice-out day of year Cyclotella spp Aulacoseira spp 134 50 132 40 130 30 Relative Abundance (%) 128 126 20 Ice-Out Day of Year 124 10 122 0 120 R = - 0.76 118 1970 1980 1990 2000 134 60 132 50 130 128 40 126 30 124 122 20 R = 0.77 120 118 10 1970 1980 1990 2000 Year AD Rühland, Paterson, Smol 2008: Global Change Biology

How will this affect other algae and cyanobacteria?

Potential triggers for algal blooms on LOW Have lake TP concentrations increased over time? NO Consistent with declines in TP loading to Rainy R. (and with limited monitoring data)

Is there a disconnect in Lake of the Woods? Perception is correct but warming is likely playing a key role Perception that blue green blooms have increased in intensity and duration in recent years (Photo: T. Sellers)

Diatom-inferred TP Applied the Hyatt et al. (2011) TP model (R 2 boot =0.58, RMSEP=0.15) 48 Rühland et al. 2010. Limnol. Oceanogr.

TP >12 µg/L TP <10 µg/L TP >14 µg/L Sediment chl a (and its main diagenetic products) also increase with warming/thermal stability, provided a nutrient threshold is reached. Paterson et al. 2017. LRM

Blue-greens like it hot!

Stronger mixing and/or longer ice-cover period Strongly mixed water column Stratified and/or longer open water period Weakly mixed/increased thermal stability EXACERBATES BLOOMS Even without further increases in nutrients

Are the blooms cyanobacteria?? (eDNA and microcystin toxins preserved in LOW sediment cores) present in all bacteria proxy of bg abundance microcystin-synthesizing gene Pilon et al. 2019, LRM

Example #2 Can too little of something cause an algal bloom?

Calcium declines in lakes – A legacy of acid rain? X

Lake [Ca] Decline “Aquatic Osteoporosis” The widespread threat of calcium decline in fresh waters Jeziorski, A., Yan, N.D., Paterson, A.M., DeSellas, A.M., Turner, M., Jeffries, D., Keller, W., Weeber, R., McNicol, R., Palmer, M., McIver, K., Arseneau, K., Ginn, B., Cumming, B., and Smol, J.P. (2008) Science 322: 1374-77.

Ont. Min. Env. Climate Change

Ont. Min. Env. Climate Change