How was the original image converted to the binary (black/white) that you include in your post? If it is made by thresholding it might be possible to improve the thresholding level. Otherwize it might be a good idea to use some-kind of image filtering (e.g. variance) before the thresholding.
You can do a binary operation called "close-" under the "Process" -> "Binary" menu. This effective works as if you perform a "Dilate" followed by a "Erode", and will close the space between particle "fragments" close together.