The ability to accurately identify species is prerequisite for assessing levels of biological diversity and a fundamental requirement for ecological research. In recent times, there has been a shortfall in biologists who practice traditional alpha taxonomy, leading to difficulties in assessment of biodiversity in some taxonomic groups. The use of a molecular DNA barcoding approach has been suggested as a tool that can be used to complement and accelerate traditional alpha taxonomy, without supplanting or invalidating existing taxonomic practices. Two different techniques were used to identify organisms, molecular and alpha taxonomy. This thesis addressees several questions relating to sponge systematics. Research was focused on three areas; (1) record sponge biodiversity from the Bay of Plenty region, (2) undertake a systematic revision of the fauna correlating ‘historical’ taxonomy with a modern phylogenetic assessment (3) determine whether identifications based on genetic barcoding are congruent with those produced via traditional morphological methods (alpha taxonomy), and to assess the use of molecular techniques for Demospongiae species identifications. This was the first focused research on sponge diversity in the Bay of Plenty region. Fifty five species are described in this research. Of these, there are up to three new families, three new genera and thirty four species which are un-described and deemed new to science. However, a more conservative estimate with grouped specimens suggests that there is a minimum of at least one new family, one new genus, and eighteen new species that are un-described and deemed new to science. In summary, we conclude that for New Zealand Demospongiae, sequence variation present in the barcoding region of the COI gene is sufficient to allow for the identification individuals to their nominate species. The use of mtDNA barcoding can without doubt complement classical morphological taxonomy and accelerate the identification process and may in fact revive an interest classical morphological taxonomy.