def merge_duplicate(merged_streams_in_island_list):
    """
    Merge lists that have at least one common element into one list.
    
    :param merged_streams_in_island_list: list of lists to test and merge
    :type merged_streams_in_island_list: list of lists
    
    :return: list of merged lists
    :rtype: list of lists
    """
    # List of lists to merge
    list_islands = merged_streams_in_island_list.copy()
    
    # For each pair of lists
    for list1 in list_islands:
        for list2 in list_islands:
            if list1 != list2:
                # Test if there is a common element
                to_merge = False
                for elem in list2:
                    if elem in list1:
                        to_merge = True
                # If so, merge
                if to_merge:
                    for elem in list2:
                        if elem not in list1:
                            list1.append(elem)
                    list_islands.pop(list_islands.index(list2))
    
    # List or merged lists               
    return list_islands