Ecological Studies and Mathematical Modeling of Cladophora in Lake Huron: 4. Photosynthesis and Respiration as Functions of Light and Temperature

231

154

The effects of nutrient ratios on algal community structure and algal growth have been examined extensively in lakes and marine environments, but rarely in streams. We manipulated stream water N : P ratio (65 : 1, 17 : 1, 4 : 1) and total nutrient concentration (low and high) in a factorial experiment using once-through streamside flumes and measured responses in abundance, community structure, and elemental composition of periphyton communities. Early in the experiment, periphyton chlorophyll a and total algal biovolume were higher for treatments where N was added (high total nutrient concentration) but were not affected by N : P ratio. This response is contrary to our prediction that P would limit periphyton growth based on the high N : P ratio in the source water and unamended periphyton mats. The relative abundance of nine of eleven common algal taxa was affected by N : P ratio, total nutrient concentration, or both. Overall, algal community structure was more sensitive than bulk measures of periphyton abundance to changes in N : P ratio and total nutrient concentration. Periphyton %N and %P increased with the N and P concentration of stream water, and periphyton N : P tracked stream water N : P ratio. Responses in periphyton chemical composition to nutrients could affect the food quality of periphyton for consumers.

Section: Discussionsupporting

confidence: 48%

Effects of N: P ratio and total nutrient concentration on stream periphyton community structure, biomass, and elemental composition

Stelzer

Lamberti

2001

231

154

“…Sloughing rates are recognized as the most difficult parameter to quantify accurately . More likely, Cladophora respiration rates may have been underestimated for senescing Cladophora because metabolic-rate algorithms were based on measurements of vigorously growing Cladophora filaments (Graham et al 1982). The metabolic demands of cellular repair may increase as Cladophora ages, leading to higher respiration following peak biomass.…”

Section: Discussionmentioning

confidence: 99%

“…R day was measured as the dark respiration rate of Cladophora that had been immediately previously acclimated to a given light level. R night was calculated as the dark respiration rate measured in dark-acclimated Cladophora and was a function of temperature alone (Graham et al 1982). The M P multiplier was based on the Droop growth model in which P is the limiting resource…”

Section: Methodsmentioning

confidence: 99%

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

Malkin

Guildford

Hecky

2008

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'...

“…Among eucaryotic green algae, the effects of irradiance and temperature on photosynthesis and respiration have been reported for Cladophora glomerata (Graham et al 1982), Ulothrix zonata (Graham et al 1985), Pithophora oedogonia (Spencer et al 1985), and a Spirogyra species isolated from a nuisance bloom in a eutrophic lake (Graham et al 1995). Optimal conditions for C. glomerata were 15°C and 300 pmol quanta m-2 s-l, but even under optimal conditions, maximum net photosynthesis was only 7.7 mg O2 g-l h-l. P. oedogonia, which is closely related to Cladophora (both are members of the Cladophorales), exhibited a similarly low maximum rate of net photosynthesis (9.7 mg O2 g-l h-l) but very different optimal temperature and irradiance conditions (26°C and 970 pmol quanta m-2 s-l).…”

Section: Discussionmentioning

confidence: 99%

Physiological ecology of a species of the filamentous green alga Mougeotia under acidic conditions: Light and temperature effects on photosynthesis and respiration

Graham

Arancibia-Ávila

Graham

1996

Self Cite

One of the earliest and most reliable indications of acid precipitation affecting freshwater systems is the development of littoral blooms of the filamentous green alga Mougeotia (Zygnematales, Charophyceae). Field observations of depth distribution and seasonal abundance in Little Rock Lake, an experimentally acidified seepage lake in north-central Wisconsin, suggest that Mougeotia might prefer warmer temperatures and carry out net photosynthesis at fairly low light levels. To test these hypotheses, we measured net photosynthesis and respiration at 56 combinations of irradiance and temperature in a controlled environment facility. Optimum conditions were 25°C and 300-2,300 bmol quanta m-2 s-I. Over this range, net photosynthesis averaged 40.4 mg 0, g-l h-l. Respiration rates increased with both temperature and prior irradiance. Lightenhanced respiration rates were significantly greater than dark respiration rates following irradiance 2 164 pm01 quanta m-* s-l. Mougeotia's photosynthetic response to temperature and irradiance explains aspects of its growth and distribution in acidified lakes but it does not by itself explain the magnitude of this alga's growth at low pH.Since the early 197Os, acidification of freshwater systems by acid precipitation has been increasingly recognized as a widespread and significant environmental problem. One of the earliest and most reliable indications of acid precipitation affecting freshwaters is the development of littoral blooms or mats of filamentous green algae of the family Zygnemataceae. The genus Mougeotia is one of the most common bloom-forming alga in acid waters of Europe and North America. Despite the frequency with which Mougeotia is cited as an indicator of acidification, little is known about its ecology or physiology. Why should Mougeotia rather than some other alga be so frequently associated with acidification? The most Acknowledgments