Climate‐related differences in the dominance of submerged macrophytes in shallow lakes

Abstract

It has been suggested that shallow lakes in warm climates have a higher probability of being turbid, rather than macrophyte dominated, compared with lakes in cooler climates, but little field evidence exists to evaluate this hypothesis. We analyzed data from 782 lake years in different climate zones in North America, South America, and Europe. We tested if systematic differences exist in the relationship between the abundance of submerged macrophytes and environmental factors such as lake depth and nutrient levels. In the pooled dataset the proportion of lakes with substantial submerged macrophyte coverage (430% of the lake area) decreased in a sigmoidal way with increasing total phosphorus (TP) concentration, falling most steeply between 0.05 and 0.2 mg L À1 . Substantial submerged macrophyte coverage was also rare in lakes with total nitrogen (TN) concentrations above 1-2 mg L À1 , except for lakes with very low TP concentrations where macrophytes remain abundant until higher TN concentrations. The deviance reduction of logistic regression models predicting macrophyte coverage from nutrients and water depth was generally low, and notably lowest in tropical and subtropical regions (Brazil, Uruguay, and Florida), suggesting that macrophyte coverage was strongly influenced by other factors. The maximum TP concentration allowing substantial submerged macrophyte coverage was clearly higher in cold regions with more frost days. This is in agreement with other studies which found a large influence of ice cover duration on shallow lakes' ecology through partial fish kills that may improve light conditions for submerged macrophytes by cascading effects on periphyton and phytoplankton. Our findings suggest that, in regions where climatic warming is projected to lead to fewer frost days, macrophyte cover will decrease unless the nutrient levels are lowered.

Restoring macrophyte diversity in shallow temperate lakes: biotic versus abiotic constraints

“…This may indicate that growing conditions are still not good enough and in that case transplanting will be unsuccessful. For macrophytes to maintain a clear water state a minimum coverage of the lake seems to be required; as a rule of thumb 30% coverage has been used as a minimum threshold (Jeppesen et al, 1994;Van Nes et al, 2002;Janse et al, 2008;Kosten et al, 2009a), which is in the range of 10%-40% reported by Sondergaard et al (2010), but others report the need for higher coverage (50% Tatrai et al, 2009, 60% Blindow et al, 2002. In warm lakes in tropical and subtropical regions, a higher coverage of macrophytes may be needed as the grazing of zooplankton on phytoplankton is low due to high fish predation Kosten et al, 2009a).…”

Effects of warming on Potamogeton crispus growth and tissue stoichiometry in the growing season

“…Macrophytes are key components in the ecological functioning of shallow lake ecosystems and they are affected by warming in various ways (Kosten et al, 2009). At the level of the plant individual, warming may affect plant physiology (Madsen and Brix, 1997;Rooney and Kalff, 2000), growth (Haag and Gorham, 1977;Short and Neckles, 1999) and reproduction (Van Vierssen et al, 1984;Mckee et al, 2002).…”

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“…Macrophyte biomass is one of the most important indices of the ecological status of lakes (Kosten et al, 2009). High values of biomass, especially of submerged macrophytes, indicate good condition of lakes.…”

“…Submerged ones however, particularly in shallow lakes, are sensitive to changes in habitat conditions and can change within a few years (Rooney, Kalff, & Habel, 2003;Schaumburg et al, 2004). Changes in environmental conditions including differences in nutrients and seasonal temperature can influence the composition of submerged macrophytes (Kosten et al, 2009). Nevertheless, other important factors that influence macrophyte development include wind, water level fluctuations, and algal blooms (Lechmann & Lachavanne, 1999).…”