No abstract

Large-scale changes in subtidal reef habitats have occurred within the Leigh Marine Reserve (New Zealand) since its establishment in 1976. To determine the extent of habitat change within Goat Island Bay, video transects positioned by a radio acoustic positioning telemetry (RAPT) system were used to map habitats within a Geographic Information System (GIS) framework. This map was compared to a map of the same area constructed 22 years earlier in 1978. Visual categorisation of habitats was consistent with the quantification of habitat-forming species within quadrats, justifying the creation of a map based on visually interpreted video footage. Furthermore, the large-scale changes in habitats were consistent with smaller-scale changes in community structure identified at permanent sites located in the study area. The most obvious changes were the total disappearance of ‘urchin barrens’ across all depths and the recovery of kelp forest in water <8 m, caused by a trophic cascade related to predator recovery. In water > 12 m, the extent of kelp forest and sponge flats was found to decrease by 25 and 33%, respectively, while turfing algal habitat had increased by 50%. This increase in turfing algal habitat had not been previously documented due to the spatial scale of traditional sampling methods.

Monitoring species' response in marine protected areas is important for informing both the management of those areas and the establishment of additional protected areas. Populations of spiny lobsters Jasus edwardsii were monitored in eight New Zealand marine reserves for up to 34 years. The populations displayed highly variable responses to protection. While a few showed rapid (within 1-2 years of protection) increases in abundance, others showed little response even after a decade of protection. Some reserves displayed little initial recovery, then a sudden increase following several years of protection, while others displayed significant declines in abundance following initial recovery. Marine reserves located in areas with initially high densities of juveniles tended to have rapid recovery, but aspects of reserve design had no significant influence on the recovery rate. Variability among recovery trajectories also suggests that supply-side dynamics may be a key driver of lobster recovery. Densities of legal-sized lobsters were positively correlated with reserve age, but the abundance of juvenile lobsters increased in all but one reserve, indicating enhanced recruitment, survival and/or movement of juvenile lobsters into reserves. It is important to consider the placement of reserves, with respect to potential levels of larval supply, when establishing marine reserves for either conservation or fisheries management purposes and for evaluating their effectiveness.

High in situ rates of phosphate uptake should coincide with high tissue phosphorus content and/or high growth rate and be either supply-driven (largely controlled by the phosphate concentration in the surrounding seawater) or demand-driven (largely dictated by the maximum uptake rate, V max , and under the control of the organism). To test this hypothesis, 6 common New Zealand seaweed species (Cystophora torulosa, Melanthalia abscissa, Pterocladia lucida, Ulva intestinalis, Xiphophora chondrophylla and Zonaria turneriana) were used. We calculated in situ rates of phosphate uptake from the kinetic constants of uptake, monthly rates of uptake at a fixed phosphate concentration and seawater phosphate concentration, and compared these rates with monthly tissue phosphorus content. There were no significant differences in the half-saturation constant (K m ) values for phosphate uptake by the 6 species. V max and affinity (V max /K m ) were largely a function of the seaweed surface area:volume quotient. In the 5 species where there was a peak in tissue phosphorus levels, it occurred in July or September/October. Peaks in tissue phosphorus in M. abscissa, P. lucida, U. intestinalis and Z. turneriana coincided with, or occurred soon after, peaks in calculated in situ rates of phosphate uptake. Maximum rates of in situ phosphate uptake were demand-driven in all subtidal species and supply-driven in the only intertidal alga U. intestinalis.

1. The ocean's remoteness, ecological complexities, lengthy ecosystem processes, and vulnerability to multiple and cumulative anthropogenic threats make marine conservation communication particularly difficult. Both scientists and journalists face unique challenges in explaining the science of these often out-of-sight