Koontz, J., D.G. Huggins, C.C. Freeman, D.S. Baker - Central Plains ...

measurement. There are sites within our sample population that are considered lacustrine, but
due to drought conditions in 2005, at least one of these sites was completely dry apparently due
to water use on surrounding agricultural areas. Upon revisit during Phase II, this site had a
maximum depth of 1.15 m and appeared to have lacustrine qualities, including an extensive
aquatic bed habitat and a fish population. Given that rainfall, river flooding, and evaporative
processes may significantly affect floodplain wetland water depth during any year or season, the
use of water depth to define the difference between lacustrine and palustrine should be used with
caution. In the EPA‟s National Lake Survey, lake sites that were less than 1 m deep were
excluded. Perhaps 1 meter is a better threshold for helping distinguish between deepwater
habitats (e.g. lacustrine) and palustrine wetlands. It should also be noted that the NWI dataset
for wetland bodies assumes that wetlands with large surfaces areas are also deeper and thus are
assigned to the lacustrine class. In our study, many discrepancies were found between the NWI
classification and existing water body conditions. Because true lake sites did exist, and
relationships were found between and among lacustrine, palustrine, and riverine wetlands, this
major classification scheme was retained along with the dominant vegetation type and the
lacustrine zone of the surveyed wetland.
Kruskal-Wallace non-parametric tests by CPCB type indicated that emergent macrophyte bed
types (n = 25) have significantly (p = 0.001) shallower mean depths than aquatic bed types (n =
9), unconsolidated bed types (n = 15), and MIX types (n = 7), based on normal Z value
differences. However, more discriminate Bonneferonni Z value tests only indicated that AB and
EM differed significantly. Differences in maximum depth were found to be significant (p =
0.001) among types, though normal Z tests only showed that AB and EM were statistically
different. When populations were separated by major classes (lacustrine and palustrine), no
significant differences were found among the mean and maximum depth means. Mean and
maximum depth positively correlated with mean Secchi depth, TN:TP, and each other, and were
found to be negatively correlated with mean turbidity, total phosphorus, organic phosphorus,
TOC, and DOC concentrations. Robust linear regression analysis showed that a significant
positive relationship existed between mean depth and TN:TP ratio (p = 0.001, R 2 = 0.183).
Maximum depth and TN:TP relationship was even stronger (p < 0.000, R 2 = 0.28). Maximum
depth and mean Secchi depth relationship was significant and positive (p < 0.000, R 2 = 0.28),
while mean depth and mean Secchi depth was also significant (p < 0.000, R 2 = 0.25). Mean
turbidity was significantly correlated (negative) with mean depth but explained very little of the
variance between these factors (p = 0.029, R 2 = 0.069). Maximum depth was also significantly
correlated with mean turbidity (p = 0.014, R 2 = 0.093). Total phosphorus was negatively related
to maximum depth (p = 0.093, R 2 = 0.25) and mean depth (p