TY - JOUR
T1 - Fluvial seeding of cyanobacterial blooms in oligotrophic Lake Superior
AU - Reinl, Kaitlin L.
AU - Sterner, Robert W.
AU - Lafrancois, Brenda Moraska
AU - Brovold, Sandra
N1 - Publisher Copyright:
© 2020
PY - 2020/12
Y1 - 2020/12
N2 - Lake Superior has recently begun experiencing cyanobacterial blooms comprised of Dolichospermum lemmermannii near the Apostle Islands and along the southern shore of the western arm. Little is known about the origin of these blooms. Experiments were conducted during the summers of 2017 and 2018 to identify sources of propagules and characteristics of sites that were potential sources. The 2017 experiments were conducted using a factorial design with three source zones (‘River’, ‘Lake’, and ‘Harbor’), two nutrient conditions (high and low N:P), and three temperatures (15, 20, and 25°C). At the end of the experiment, cyanobacteria were most abundant from the ‘River’ and ‘Harbor’ zones at low N:P and 20 and 25°C, with D. lemmermannii most abundant at 20°C. Subsequently, in 2018 we evaluated 26 specific inland locations from three waterbody types (‘River’, ‘Lake/Pond’, and ‘Coastal’) and explored similarities among those sites that produced cyanobacteria in high abundance when samples were incubated under optimal conditions (low N:P and 25°C). Under these growing conditions, we found high cyanobacteria abundance developed in samples from river sites with low ambient temperatures and high conductivity. Field monitoring showed that Lake Superior nearshore temperatures were higher than rivers. These observations suggest that blooms of D. lemmermannii in Lake Superior are initiated by fluvial seeding of propagules and highlight the importance of warmer temperatures and favorable nutrient and light conditions for subsequent extensive cyanobacterial growth. We argue that the watershed is an important source of biological loading of D. lemmermannii to Lake Superior and that when those cells reach the nearshore where there are warmer water temperatures and increased light, they can grow in abundance to produce blooms.
AB - Lake Superior has recently begun experiencing cyanobacterial blooms comprised of Dolichospermum lemmermannii near the Apostle Islands and along the southern shore of the western arm. Little is known about the origin of these blooms. Experiments were conducted during the summers of 2017 and 2018 to identify sources of propagules and characteristics of sites that were potential sources. The 2017 experiments were conducted using a factorial design with three source zones (‘River’, ‘Lake’, and ‘Harbor’), two nutrient conditions (high and low N:P), and three temperatures (15, 20, and 25°C). At the end of the experiment, cyanobacteria were most abundant from the ‘River’ and ‘Harbor’ zones at low N:P and 20 and 25°C, with D. lemmermannii most abundant at 20°C. Subsequently, in 2018 we evaluated 26 specific inland locations from three waterbody types (‘River’, ‘Lake/Pond’, and ‘Coastal’) and explored similarities among those sites that produced cyanobacteria in high abundance when samples were incubated under optimal conditions (low N:P and 25°C). Under these growing conditions, we found high cyanobacteria abundance developed in samples from river sites with low ambient temperatures and high conductivity. Field monitoring showed that Lake Superior nearshore temperatures were higher than rivers. These observations suggest that blooms of D. lemmermannii in Lake Superior are initiated by fluvial seeding of propagules and highlight the importance of warmer temperatures and favorable nutrient and light conditions for subsequent extensive cyanobacterial growth. We argue that the watershed is an important source of biological loading of D. lemmermannii to Lake Superior and that when those cells reach the nearshore where there are warmer water temperatures and increased light, they can grow in abundance to produce blooms.
KW - Algal loading
KW - Cyanobacteria
KW - Harmful algal blooms
KW - Oligotrophic
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U2 - 10.1016/j.hal.2020.101941
DO - 10.1016/j.hal.2020.101941
M3 - Article
C2 - 33298366
AN - SCOPUS:85096159655
SN - 1568-9883
VL - 100
JO - Harmful Algae
JF - Harmful Algae
M1 - 101941
ER -