the reef biota at bunurong marine national park - Parks Victoria

Parks Victoria Technical Series No. 84
Bunurong Subtidal Reef Monitoring
3.4 Climate Change
Species composition
Cold water, Maugean algal species richness and total abundance is consistently higher in the
MNP sites throughout the monitoring period. In the 2011 survey Maugean algal species
richness at reference sites was the lowest of the entire monitoring period (Figure 3.17). The
Maugean fish species richness and total abundance also decreased in the 2011 survey
(Figure 3.18). The occurrence of Maugean invertebrate species was low or absent in all
surveys.
The western algal species richness was relatively low, with abundance only varying
occasionally throughout the monitoring period, (Figure 3.19). Western invertebrate species
richness increased slightly over the previous three surveys, following a decline in the 2003
survey. Abundance of western invertebrates has been consistently low, with the exception of
reference sites in 2000 and 2002. Species richness of western invertebrates has been similar
in MPA and reference sites following a similar pattern (Figure 3.20). Western fish species
richness and abundance were low on all survey occasions, with no discernible trends
evident.
The eastern algal species in the Bunurong region were not well represented at any time.
Eastern invertebrate species were recorded intermittently in very low densities over the
monitoring period. Eastern fish species were observed in low to medium abundances in
surveys prior to the park declaration, however have been absent or in very low abundances
in subsequent surveys (Figure 3.21).
Macrocystis pyrifera
The string kelp M. pyrifera can grow up to 10 m in height and form dense forests with a thick
canopy floating on the surface. Consequently, M. pyrifera is a significant habitat forming
species. Anecdotal evidence suggests M. pyrifera was once present in relatively high
abundance along the Victorian coast, forming large forests in some locations. Abundances of
M. pyrifera were reduced for much of this decade. Possible causes of this decline include a
rapid succession of El Niño events in the late 1980s and early 1990s (affecting water
temperature and nutrient levels), a long-term increase in average sea temperature (1 ºC over
the last 40 years) and changes to coastal nutrient inputs.
The quadrat-cover measurements detected substantial changes in M. pyrifera cover between
the first two surveys. During June 1999, coverage was greatest at Cape Patterson (Site 1),
Oaks East (Site 3), Twin Reefs (Site 4) and Shack Bay West (Site 5) with coverage of 2.5,
1.6, 0.8 and 1.5 percent respectively. By January 2000, this had increased to 15 % at sites
Oaks East and Twin Reefs, with minor increases or decreases detected at other sites. A
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