100
M. T. Dokulil
trophic state of a water body. Trophic categorization based
on phytoplankton productivity, however, is based on the assumption that inputs from littoral or allochthonous sources
are negligible. On a global basis, productivity from the littoral or of external origin can be much larger than phytoplankton production in many cases (Wetzel 1990).
The original concept of the trophic system aims to arrange surface waters, regardless of their size and ecological
characteristics, in a continuous sequence of increasing trophy. The basis for comparison is the intensity of organic production (Ohle 1958). The autotrophic capacity of a lake or a
river therefore appears to be an ideal basis for establishing
an absolute scale of trophic level (Elster 1954, 1958; Winberg 1960). Hence, ‘trophy’ is often directly equated with
the intensity of primary production, which should better be
termed ‘autotrophic production’ following argumentation by
Flynn (1988).
The aim of this chapter is to gather and critically evaluate information on the use of primary production criteria to
define trophic boundary conditions, particularly for variable
eutrophic systems.
9.2 Lakes, Data and Methods
The lakes covered in this study range from ultra-oligotrophic
Arctic lakes to hypertrophic tropical lakes, include shallow
and deep lakes, high mountains and flatland lakes from around
the world. If not otherwise stated, the data used in this compilation are original or come from information summarised
in Dokulil (2005) for alpine lakes, Dokulil et al. (2005) for a
variety of lake types, Håkanson and Boulion (2001) for lakes
from the former Soviet Union (their Annex A) and Kimmel
et al. (1990) for reservoirs.
Carbon uptake can conveniently be estimates using the
14
C-technique developed by Steemann Nielsen (1951) or one
of its modifications (Dokulil and Kaiblinger 2009). Incubation periods of equal or less than 2 h are considered to represent gross uptake. Alternatively, photosynthetic oxygen evolution or fluorescence signals can be measured (Dokulil et al.
2005; Dokulil and Kaiblinger 2009). For details on methods
and conversions to carbon, refer to Wetzel and Likens (1991,
p. 207 ff.) and Kaiblinger and Dokulil (2006).
Chlorophyll-a (chl-a) is used here as a universal indicator
of algal biomass and was measured by extraction in either
acetone or ethanol followed by photometrical determination
(Lorenzen 1967, ISO 10260 1992).
Production estimations reported as oxygen rates were
converted to carbon using a factor of 0.3 mg C per mg O 2
assuming an assimilation coefficient of 1.25. Hourly rates
of photosynthesis were converted to daily rates using appropriate day length conversion (day light hours × 0.6; Talling
1957).
9.3 Primary Productivity Relationships
Almost all definitions of trophic categories are primarily related to nutrient concentration and loading from the catchment (Rast and Thornton 2005). Klapper (1992) related average annual integrated primary production (ΣΣP) to total
phosphorus (TP) concentration at spring overturn (Fig. 9.1).
A similar relation to soluble reactive phosphorus at spring
overturn (SRP SP ) was reported by Fricker (1981). Daily and
annual production was correlated with TP, SRP SP and to TP
concentrations predicted from models (Clasen and Bernhardt 1980; Fricker 1980; Vollenweider and Kerekes 1980;
OECD 1982). Håkanson and Boulion (2001) have related TP
to maximum and mean volumetric daily production in their
extensive study, trophic relations. Similarly, production estimates from clear and humic lakes were correlated to chl-a
and TP by Nürnberg and Shaw (1999). A recent meta-analysis examined the effects of several variables including nutrients on absolute and relative production estimates (Faithfull
et al. 2011). One of their conclusions was that both P and
N can be predictors of primary production. This well-established, positive relationship between loading and productivity becomes apparent when phytoplankton biomass increases as a consequence of eutrophication (e.g. Harper 1992).
Eutrophic and hypereutrophic lakes can sustain very high
algal biomass often dominated by few taxa. In such systems,
however, total phytoplankton biomass as well as all groups
except blue-greens and diatoms tend to flatten off (Watson
et al. 1992, 1997). This curvilinearity is also evident during
the oligotrophication process (Jeppesen et al. 2005). Phytoplankton biomass can be estimated indirectly using chl-a as
a surrogate parameter. Both variables correlate well as has
been demonstrated many times (e.g. Huot et al. 2007). The
chl-a therefore remains the best proxy of phytoplankton biomass for studies of primary productivity (Huot et al. 2007).
The chl-a correlates with daily photoautotrophic production (A) over a wide range of trophic levels from ultra-oligotrophic arctic lakes to highly productive tropical lakes in
Africa (Fig. 9.2).
Average volumetric production in the euphotic zone directly depends on mean chl-a concentration. The correlation of the 214 observations is highly significant ( r
2
= 0.81,
p < 0.001). The 95 % confidence limits remain narrow over
the entire range (4 orders of magnitude) indicating good
agreement between variables. This close relation allows designation of empirical trophic boundaries (Fig. 9.2). These
boundaries omit average values as suggested by the regression equation and is orientated towards accommodation of
all production rates in each trophic category.
To model photoautotrophic production from chl-a
(Håkanson and Peters 1995; Bot and Colijn 1996; Morin
et al. 1999), additional information on the relationship with
incoming radiation is required. Daily column production
M. T. Dokulil
trophic state of a water body. Trophic categorization based
on phytoplankton productivity, however, is based on the assumption that inputs from littoral or allochthonous sources
are negligible. On a global basis, productivity from the littoral or of external origin can be much larger than phytoplankton production in many cases (Wetzel 1990).
The original concept of the trophic system aims to arrange surface waters, regardless of their size and ecological
characteristics, in a continuous sequence of increasing trophy. The basis for comparison is the intensity of organic production (Ohle 1958). The autotrophic capacity of a lake or a
river therefore appears to be an ideal basis for establishing
an absolute scale of trophic level (Elster 1954, 1958; Winberg 1960). Hence, ‘trophy’ is often directly equated with
the intensity of primary production, which should better be
termed ‘autotrophic production’ following argumentation by
Flynn (1988).
The aim of this chapter is to gather and critically evaluate information on the use of primary production criteria to
define trophic boundary conditions, particularly for variable
eutrophic systems.
9.2 Lakes, Data and Methods
The lakes covered in this study range from ultra-oligotrophic
Arctic lakes to hypertrophic tropical lakes, include shallow
and deep lakes, high mountains and flatland lakes from around
the world. If not otherwise stated, the data used in this compilation are original or come from information summarised
in Dokulil (2005) for alpine lakes, Dokulil et al. (2005) for a
variety of lake types, Håkanson and Boulion (2001) for lakes
from the former Soviet Union (their Annex A) and Kimmel
et al. (1990) for reservoirs.
Carbon uptake can conveniently be estimates using the
14
C-technique developed by Steemann Nielsen (1951) or one
of its modifications (Dokulil and Kaiblinger 2009). Incubation periods of equal or less than 2 h are considered to represent gross uptake. Alternatively, photosynthetic oxygen evolution or fluorescence signals can be measured (Dokulil et al.
2005; Dokulil and Kaiblinger 2009). For details on methods
and conversions to carbon, refer to Wetzel and Likens (1991,
p. 207 ff.) and Kaiblinger and Dokulil (2006).
Chlorophyll-a (chl-a) is used here as a universal indicator
of algal biomass and was measured by extraction in either
acetone or ethanol followed by photometrical determination
(Lorenzen 1967, ISO 10260 1992).
Production estimations reported as oxygen rates were
converted to carbon using a factor of 0.3 mg C per mg O 2
assuming an assimilation coefficient of 1.25. Hourly rates
of photosynthesis were converted to daily rates using appropriate day length conversion (day light hours × 0.6; Talling
1957).
9.3 Primary Productivity Relationships
Almost all definitions of trophic categories are primarily related to nutrient concentration and loading from the catchment (Rast and Thornton 2005). Klapper (1992) related average annual integrated primary production (ΣΣP) to total
phosphorus (TP) concentration at spring overturn (Fig. 9.1).
A similar relation to soluble reactive phosphorus at spring
overturn (SRP SP ) was reported by Fricker (1981). Daily and
annual production was correlated with TP, SRP SP and to TP
concentrations predicted from models (Clasen and Bernhardt 1980; Fricker 1980; Vollenweider and Kerekes 1980;
OECD 1982). Håkanson and Boulion (2001) have related TP
to maximum and mean volumetric daily production in their
extensive study, trophic relations. Similarly, production estimates from clear and humic lakes were correlated to chl-a
and TP by Nürnberg and Shaw (1999). A recent meta-analysis examined the effects of several variables including nutrients on absolute and relative production estimates (Faithfull
et al. 2011). One of their conclusions was that both P and
N can be predictors of primary production. This well-established, positive relationship between loading and productivity becomes apparent when phytoplankton biomass increases as a consequence of eutrophication (e.g. Harper 1992).
Eutrophic and hypereutrophic lakes can sustain very high
algal biomass often dominated by few taxa. In such systems,
however, total phytoplankton biomass as well as all groups
except blue-greens and diatoms tend to flatten off (Watson
et al. 1992, 1997). This curvilinearity is also evident during
the oligotrophication process (Jeppesen et al. 2005). Phytoplankton biomass can be estimated indirectly using chl-a as
a surrogate parameter. Both variables correlate well as has
been demonstrated many times (e.g. Huot et al. 2007). The
chl-a therefore remains the best proxy of phytoplankton biomass for studies of primary productivity (Huot et al. 2007).
The chl-a correlates with daily photoautotrophic production (A) over a wide range of trophic levels from ultra-oligotrophic arctic lakes to highly productive tropical lakes in
Africa (Fig. 9.2).
Average volumetric production in the euphotic zone directly depends on mean chl-a concentration. The correlation of the 214 observations is highly significant ( r
2
= 0.81,
p < 0.001). The 95 % confidence limits remain narrow over
the entire range (4 orders of magnitude) indicating good
agreement between variables. This close relation allows designation of empirical trophic boundaries (Fig. 9.2). These
boundaries omit average values as suggested by the regression equation and is orientated towards accommodation of
all production rates in each trophic category.
To model photoautotrophic production from chl-a
(Håkanson and Peters 1995; Bot and Colijn 1996; Morin
et al. 1999), additional information on the relationship with
incoming radiation is required. Daily column production