which is usually at the same temperature and for the same time period as used after
the exposure (see Table 3). Once the leaf discs have been weighed, they are usually
resoaked in water or conditioned, if that is still to be done, and provided to the
Gammarids during the experiment, after sometimes rinsing with water.
During and after the exposure, data are collected to calculate the feeding rate of
the organisms. The feeding rate equation is similar throughout the literature, but
variations can still be found. For example, the data might not have been collected in
the same way, even though the same equation might have been used. The most
common way to estimate the feeding rate is to compare leaf dry weight before and
after exposure to the amphipods, in relation to the duration of the experiment and the
weight of the organisms. Commonly, the dry weight of the leaves is adjusted with a
constant. This constant takes the loss in weight due to leaching and microbial
decomposition into consideration. It is often calculated as the ratio of the control
leaves final dry weight and their initial dry weight (e.g. Blarer and Burkhardt-Holm
2016) (see Table 3), but sometimes the equation might vary (e.g. Bundschuh et al.
2011b) (see Table 3). The control leaves are leaf discs that went through the same
conditioning process, and through the same experimental conditions as those fed to
the organisms, but they themselves were not.
The constant is not always positioned in the same place within the feeding rate
equation. Most commonly, it multiplies with the initial dry weight of the leaves
(e.g. Maltby et al. 2002) (see Table 3) as the initial dry weight might not be exact. A
small amount of leaf might have been lost due to leaching and microbial decomposition during the conditioning process, for example. Sometimes it divides the final
dry weight of the leaves (Agatz et al. 2014) (see Table 3). A proportion of the leaf
might have been lost through leaching and the decomposition process, and not
through Gammarids consumption. Both constant positions are trying to adjust the
equation by compensating for the same problem, leaching and decomposition, but
mathematically the equations are dissimilar and the results might be different.
Weight is sometimes considered as wet weight (Danger et al. 2012) or as ash-free
dry weight (AFDW) (De Castro-Català et al. 2017) rather the normal dry weight (see
Table 3). Once the exposure is complete, the leaf discs are collected and dried. The
drying process is normally carried out in an oven and/or furnace (i.e. AFDW) at a
specific temperature for a specific duration, which was also used for leaf disc
preparation. As shown in Table 3, the temperature at which the leaves are dried
can be very different and so can the duration of the process.
On rare occasions, the feeding rate is calculated by measuring differences in the
leaf disc’s surface area, which instead of being weighed are photographed and later
analysed with a specific software (Coulaud et al. 2011; Hahn and Schulz 2007) (see
Table 3). Scanning the leaf surface might result in very accurate data when it is
calculated by pixel size or in mm
2 , for example. This calculation does not incorporate a leaching constant (leaf change correction factor), which takes into account the
loss of leaf weight due to the conditioning process. Differences in leaf surface could
potentially occur as it happens with the loss in weight method. The authors acknowledge that it is still unclear if the choice of feeding equation and the different ways of
calculating the feeding rate are actually comparable and equivalent. Interestingly
32
G. Consolandi et al.
the exposure (see Table 3). Once the leaf discs have been weighed, they are usually
resoaked in water or conditioned, if that is still to be done, and provided to the
Gammarids during the experiment, after sometimes rinsing with water.
During and after the exposure, data are collected to calculate the feeding rate of
the organisms. The feeding rate equation is similar throughout the literature, but
variations can still be found. For example, the data might not have been collected in
the same way, even though the same equation might have been used. The most
common way to estimate the feeding rate is to compare leaf dry weight before and
after exposure to the amphipods, in relation to the duration of the experiment and the
weight of the organisms. Commonly, the dry weight of the leaves is adjusted with a
constant. This constant takes the loss in weight due to leaching and microbial
decomposition into consideration. It is often calculated as the ratio of the control
leaves final dry weight and their initial dry weight (e.g. Blarer and Burkhardt-Holm
2016) (see Table 3), but sometimes the equation might vary (e.g. Bundschuh et al.
2011b) (see Table 3). The control leaves are leaf discs that went through the same
conditioning process, and through the same experimental conditions as those fed to
the organisms, but they themselves were not.
The constant is not always positioned in the same place within the feeding rate
equation. Most commonly, it multiplies with the initial dry weight of the leaves
(e.g. Maltby et al. 2002) (see Table 3) as the initial dry weight might not be exact. A
small amount of leaf might have been lost due to leaching and microbial decomposition during the conditioning process, for example. Sometimes it divides the final
dry weight of the leaves (Agatz et al. 2014) (see Table 3). A proportion of the leaf
might have been lost through leaching and the decomposition process, and not
through Gammarids consumption. Both constant positions are trying to adjust the
equation by compensating for the same problem, leaching and decomposition, but
mathematically the equations are dissimilar and the results might be different.
Weight is sometimes considered as wet weight (Danger et al. 2012) or as ash-free
dry weight (AFDW) (De Castro-Català et al. 2017) rather the normal dry weight (see
Table 3). Once the exposure is complete, the leaf discs are collected and dried. The
drying process is normally carried out in an oven and/or furnace (i.e. AFDW) at a
specific temperature for a specific duration, which was also used for leaf disc
preparation. As shown in Table 3, the temperature at which the leaves are dried
can be very different and so can the duration of the process.
On rare occasions, the feeding rate is calculated by measuring differences in the
leaf disc’s surface area, which instead of being weighed are photographed and later
analysed with a specific software (Coulaud et al. 2011; Hahn and Schulz 2007) (see
Table 3). Scanning the leaf surface might result in very accurate data when it is
calculated by pixel size or in mm
2 , for example. This calculation does not incorporate a leaching constant (leaf change correction factor), which takes into account the
loss of leaf weight due to the conditioning process. Differences in leaf surface could
potentially occur as it happens with the loss in weight method. The authors acknowledge that it is still unclear if the choice of feeding equation and the different ways of
calculating the feeding rate are actually comparable and equivalent. Interestingly
32
G. Consolandi et al.