Creating column using ifelse in R [duplicate]

I'm a little stuck with creating a new Layer column in the dataset below:

> head(Sites.merge)
     Echo_ID                 Layer Interval Lat_M         Lon_M          Target_depth_mean Depth_mean ADens
[1,] "20180919_PS-1105_BN_1" "0"   "14"     "26.28209994" "-97.04343251" "0"               " "        "0"  
[2,] "20180919_PS-1105_BN_1" "0"   "15"     "26.28205407" "-97.04343251" "0"               " "        "0"  
[3,] "20180919_PS-1105_BN_1" "0"   "16"     "26.2820098"  "-97.04343558" "0"               " "        "0"  
[4,] "20180919_PS-1105_BN_1" "0"   "17"     "26.28196587" "-97.04344517" "0"               " "        "0"  
[5,] "20180919_PS-1105_BN_1" "0"   "18"     "26.28192194" "-97.04346068" "0"               " "        "0"  
[6,] "20180919_PS-1105_BN_1" "0"   "19"     "26.28187837" "-97.04346667" "0"               " "        "0"  
 Echo_ID_Layer                   numID sum                Echo_max_depth_m S_type       DepthZone  
[1,] "20180919_PS-1105_BN_1_Layer_0" "1"   "13.4396280406658" "16.79"          "Artificial" "Nearshore"
[2,] "20180919_PS-1105_BN_1_Layer_0" "1"   "13.4396280406658" "16.79"          "Artificial" "Nearshore"
[3,] "20180919_PS-1105_BN_1_Layer_0" "1"   "13.4396280406658" "16.79"          "Artificial" "Nearshore"
[4,] "20180919_PS-1105_BN_1_Layer_0" "1"   "13.4396280406658" "16.79"          "Artificial" "Nearshore"
[5,] "20180919_PS-1105_BN_1_Layer_0" "1"   "13.4396280406658" "16.79"          "Artificial" "Nearshore"
[6,] "20180919_PS-1105_BN_1_Layer_0" "1"   "13.4396280406658" "16.79"          "Artificial" "Nearshore"
 Subregion midLayer school.depth newLayer schoolLayer
[1,] "South"   "1.679"  " "          "1"      " "        
[2,] "South"   "1.679"  " "          "1"      " "        
[3,] "South"   "1.679"  " "          "1"      " "        
[4,] "South"   "1.679"  " "          "1"      " "        
[5,] "South"   "1.679"  " "          "1"      " "        
[6,] "South"   "1.679"  " "          "1"      " "   

The current "Layer" column has some right values but most of them are wrong so I'm trying to essentially piece together a new Layer column using values from other columns that I have created:

#the first one doesn't work
Sites.merge$artLayer = ifelse(Sites.merge$Target_depth_mean == 0 & Sites.merge$school.depth == "NA", Sites.merge$Layer, Sites.merge$newLayer)
Sites.merge$schLayer = ifelse(Sites.merge$Depth_mean != "NA", Sites.merge$schoolLayer, Sites.merge$artLayer)
Sites.merge$Layer = ifelse(Sites.merge$S_type == "Artificial", Sites.merge$artLayer, Sites.merge$Layer)

In the ifelse statements below the "TRUE" statement works but the "FALSE" statement don't. Any help would be greatly appreciated. Thank you!