Here is the latest list of supported cameras OS X Mountain Lion: Supported digital camera RAW formats it does appear that the p310 is on the list. How long has the camera been released? Nixon's (and Canon's) usually get included fairly quickly so it might be include in the next one or two updates.
In the meantime there are a couple of things you could do.
If the camera has a RAW+JPG mode you could shoot in that and import both into Aperture with the JPG as master. Once the RAW format are supported you could switch over to using the RAW's as master.
You could shoot in the RAW &JPG mode and just import the JPG's and keep the RAW's in a folder on your HD. When the RAW's are supported you could import them then.
You could shoot just RAW and use Adobe's DNG converter to convert the RAW;s into DNG's and import those.
Which to use depends on a number of factors, hard to say which is best.