Modeling the growth response of Cladophora in a Laurentian Great Lake to the exotic invader Dreissena and to lake warming

Abstract

A Cladophora growth model (CGM) is calibrated and validated here to simulate attached and sloughed Cladophora biomass in daily time-steps in an urbanized location of Lake Ontario, using two years of collected input data and independent measurements of Cladophora biomass. The CGM is used to hindcast Cladophora growth using multiplicative factors of seasonal minimal tissue phosphorus concentrations (Q P ) and seasonal mean nearshore light attenuation (Kd PAR ) of the early 1970s and 1980s relative to modern data. The possible effects of climate on growth are also forecast using additive temperature increases. Cladophora Q P in Lake Ontario has declined in parallel with decreasing pelagic P concentrations, resulting in reduced Cladophora biomass at all depths in the euphotic zone. Kd PAR has also declined, most strongly since the mid-1990s, following Dreissena mussel invasion, driving an increase in biomass between 3.5-and 10-m depth. Combining these effects, the CGM predicts that biomass along shorelines today is lower in Lake Ontario than in the 1980s. However, any increases in Q P in this post-dreissenid-mussel period will result in greater Cladophora proliferation than in previous decades due to increased nearshore water clarity. Cladophora Q P , while still currently lower than in the early 1980s, may be rising due to P supply to the littoral zone by the invasive mussels. The surface water temperature of Lake Ontario indicates warming of 0.96uC decade 21 from 1980 to 2006. With increasing surface water temperatures, the CGM predicts an earlier spring growth but only a marginal increase in peak Cladophora biomass.Eutrophication continues to be among the most critical and pervasive issues facing coastal waters-marine and freshwater alike ( Nuisance densities of Cladophora have been reported from estuaries (Gordon and McComb 1989;Valiela et al. 1997), inland seas (Kiirikki 1996;Curiel et al. 2004), and hardwater rivers and lakes with moderate energy (Power 1992;Parker and Maberly 2000). In the Laurentian Great Lakes, Cladophora is a nuisance throughout Lakes Ontario, Erie, and Michigan, where hard substrate is available, and in isolated areas near nutrient point sources in Lake Huron (Herbst 1969).There is a widespread perception that since the establishment of invasive dreissenid mussels (i.e., the zebra mussel [Dreissena polymorpha] and the quagga mussel [D. bugensis]) over the past 15 yr, Cladophora biomass has resurged in the lower Great Lakes (Mills et al. 2003;Hecky et al. 2004;Bootsma et al. 2005). The degree to which this perception is accurate, however, is unclear. Due to their high biomass in these lakes (e.g., up to 150 g shell-free DM m 22 ; Fleisher et al. 2001), dreissenid mussels have been credited with reengineering nutrient distributions by removing suspended particulate matter through filterfeeding, then excreting dissolved regenerated nutrients as well as generating organic waste as feces and pseudofeces in the benthos (Hecky et al. 2004). This process, recently termed ''benthification'...

A deep chlorophyll maximum nourishes benthic filter feeders in the coastal zone of a large clear lake

“…Our growth rates measured as change in shell length generally fell within the ranges reported for upstream Lake Erie (MacIsaac 1994;Stoeckmann 2003). As expected, our reported mean near-bottom Chl a concentrations during expt 1, calibrated at Shallow and Middle stations, were somewhat higher on average than extracted Chl a concentrations previously reported from near-surface waters in the same study area during the same season (Malkin et al 2010). No comparable extracted Chl a data from near-bottom water exist from during expt 1.…”

“…In the littoral zone, dreissenid mussels are a dominant source of soluble reactive phosphorus (Ozersky et al 2010;Turner 2010), and thereby may contribute to a nutrient gradient from depth. Furthermore, mussels have likely increased light penetration in the coastal zone through their persistent filtration (Malkin et al 2008) and/or by reducing the frequency of calcite precipitation (i.e., 'whiting events'; Barbiero et al 2006). Taken together, dreissenid mussels may be promoting development of a deeper DCM.…”

“…Epilimnetic offshore waters of Lake Ontario are oligotrophic: spring total phosphorus (TP) concentration and summer Chl a concentration, averaged from 1998 to 2008, were 0.25 6 0.04 (SD) mmol L 21 and 2.37 6 1.17 (SD) mg L 21 , respectively (Malkin et al 2010). Closer to shore (2-12-m depth) in this study area, near-surface spring TP concentration was higher and summer Chl a was lower than offshore (TP 5 0.38 6 0.13 [SD] mmol L 21 and Chl a 5 1.34 6 0.8 [SD] mg L 21 ).…”

TheCladophoraresurgence in Lake Ontario: characterization and implications for management

“…Samples were taken at depths of 0.5, 1.5, 3.0, and 5.0 m at times of peak Cladophora biomass (June-August) along the shores of Oakville, Whitby, Cobourg, Presqu'ile, Point Petre, Bath, and Emeric Point (all on Lake Ontario). Additional Lake Ontario biomass values used in this study were reported by Malkin et al (2008;biomass in 2004 and at Oakville, Ontario), Higgins et al (2008; …”

Effects of Environmental Factors on Zoospore Release and Early Growth of the Green Tide Alga Cladophora albida

“…C. laetevirens, C. sericea, C. glomerata (7-9 ) (Smith et al, 2005;Malkin et al, 2008;Gubelit and Berezina, 2010;Balkıs et al, 2013).…”