Motutapu Island, Hauraki Gulf: protecting our heritage with biologically justified MPA placement
The state of Marine Protected Area’s (MPA’s) in New Zealand and the current guidelines for implementing new MPA’s are discussed with particular emphasis on intertidal rocky shores of northeastern New Zealand and Hauraki Gulf using Motutapu Island as a case study.
The rocky shores of Motutapu Island, Hauraki Gulf, were surveyed to investigate if widely distributed assemblages of species occur around the island and if any assemblages around the island were particularly unique relative to those throughout the surveyed area of northeastern New Zealand. Presence/absence inventories of all macro flora and fauna (>2mm) at 41 sites were collected and analysed with reference to bray-curtis similarity, species richness and relative species rarity. The final biological data matrix of all 41 shores was subjected to Mantel tests to investigate whether the environmental variables, fetch, exposure (product of wind & fetch), shore substratum, shore width and biological shoreheight were significantly correlated with the species assemblages encountered around Motutapu Island.
The species assemblages of Motutapu Island were then compared with a further 71 sites surveyed by Palacio (2008) throughout the region extending from Mimiwhangata Bay (north of Whangarei) to Tauranga, along the northeastern coast of New Zealand.
A total of 338 taxa were recorded on the rocky shores of Motutapu Island. Bray-curtis similarity revealed all 41 sites were at least 57% similar in assemblage structure with 25 of the 41 shores >70% similar in assemblage structure. The highest species richness (181) of all surveyed shores of northeastern New Zealand was also on Motutapu Island, with many more shores around the Island classified as having high species richness. Regardless of species richness, most shores surveyed on Motutapu Island had a good percentage of species deemed to be rare or very rare based on the frequency of occurrence relative to all surveyed shores. The rocky shores of Motutapu Island are outstanding, rare, distinctive and nationally important, therefore two alternative MPA proposals are presented.
Mantel tests revealed significant correlation between species assemblages and the total fetch, substratum, or maximum exposure (product of wind & fetch) of any surveyed shore. The appropriateness of using such environmental variables to represent unknown marine biodiversity when implementing MPA’s is a contentious issue currently facing conservation planners.
Recommendations are made for future research priorities such as comparative intertidal surveys throughout northeastern New Zealand before decisions on the placement of MPA’s are made.